1
|
Hoganson DM, Govindarajan V, Schulz NE, Hammer PE, Rathod RH, Baird CW. Complex Patient with Azygos Continuation of the Inferior Vena Cava: Value of Flow Simulation. J Thorac Cardiovasc Surg 2024:S0022-5223(24)00357-X. [PMID: 38640997 DOI: 10.1016/j.jtcvs.2024.04.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 04/07/2024] [Accepted: 04/10/2024] [Indexed: 04/21/2024]
|
2
|
Govindarajan V, Marshall L, Sahni A, Cetatoiu MA, Eickhoff EE, Davee J, St Clair N, Schulz NE, Hoganson DM, Hammer PE, Ghelani SJ, Prakash A, Del Nido PJ, Rathod RH. Impact of Age-Related Change in Caval Flow Ratio on Hepatic Flow Distribution in the Fontan Circulation. Circ Cardiovasc Imaging 2024; 17:e016104. [PMID: 38567518 PMCID: PMC11073583 DOI: 10.1161/circimaging.123.016104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 03/15/2024] [Indexed: 04/04/2024]
Abstract
BACKGROUND The Fontan operation is a palliative technique for patients born with single ventricle heart disease. The superior vena cava (SVC), inferior vena cava (IVC), and hepatic veins are connected to the pulmonary arteries in a total cavopulmonary connection by an extracardiac conduit or a lateral tunnel connection. A balanced hepatic flow distribution (HFD) to both lungs is essential to prevent pulmonary arteriovenous malformations and cyanosis. HFD is highly dependent on the local hemodynamics. The effect of age-related changes in caval inflows on HFD was evaluated using cardiac magnetic resonance data and patient-specific computational fluid dynamics modeling. METHODS SVC and IVC flow from 414 patients with Fontan were collected to establish a relationship between SVC:IVC flow ratio and age. Computational fluid dynamics modeling was performed in 60 (30 extracardiac and 30 lateral tunnel) patient models to quantify the HFD that corresponded to patient ages of 3, 8, and 15 years, respectively. RESULTS SVC:IVC flow ratio inverted at ≈8 years of age, indicating a clear shift to lower body flow predominance. Our data showed that variation of HFD in response to age-related changes in caval inflows (SVC:IVC, 2, 1, and 0.5 corresponded to ages, 3, 8, and 15+, respectively) was not significant for extracardiac but statistically significant for lateral tunnel cohorts. For all 3 caval inflow ratios, a positive correlation existed between the IVC flow distribution to both the lungs and the HFD. However, as the SVC:IVC ratio changed from 2 to 0.5 (age, 3-15+) years, the correlation's strength decreased from 0.87 to 0.64, due to potential flow perturbation as IVC flow momentum increased. CONCLUSIONS Our analysis provided quantitative insights into the impact of the changing caval inflows on Fontan's long-term HFD, highlighting the importance of SVC:IVC variations over time on Fontan's long-term hemodynamics. These findings broaden our understanding of Fontan hemodynamics and patient outcomes.
Collapse
Affiliation(s)
- Vijay Govindarajan
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
- Surgery (V.G., D.M.H., P.E.H.), Harvard Medical School, Boston, MA
- Department of Internal Medicine, University of Texas Health Science Center at Houston (V.G.)
| | - Lauren Marshall
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
| | - Akshita Sahni
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
| | - Maria A Cetatoiu
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
| | - Emily E Eickhoff
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
| | - Jocelyn Davee
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
| | - Nicole St Clair
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
| | - Noah E Schulz
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
| | - David M Hoganson
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
- Surgery (V.G., D.M.H., P.E.H.), Harvard Medical School, Boston, MA
| | - Peter E Hammer
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
- Surgery (V.G., D.M.H., P.E.H.), Harvard Medical School, Boston, MA
| | - Sunil J Ghelani
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
- Cardiology (S.J.G., A.P., P.J.d.N., R.H.R.), Boston Children's Hospital, MA
| | - Ashwin Prakash
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
- Cardiology (S.J.G., A.P., P.J.d.N., R.H.R.), Boston Children's Hospital, MA
| | - Pedro J Del Nido
- Departments of Cardiovascular Surgery (V.G., L.M., A.S., M.A.C., E.E.E., J.D., N.S.C., N.E.S., D.M.H., P.E.H., S.J.G., A.P., P.J.d.N.), Boston Children's Hospital, MA
- Cardiology (S.J.G., A.P., P.J.d.N., R.H.R.), Boston Children's Hospital, MA
| | - Rahul H Rathod
- Cardiology (S.J.G., A.P., P.J.d.N., R.H.R.), Boston Children's Hospital, MA
- Departments of Pediatrics (R.H.R.), Harvard Medical School, Boston, MA
| |
Collapse
|
3
|
Govindarajan V, Kolanjiyil A, Wanna C, Kim H, Prakash S, Chandran KB, McPherson DD, Johnson NP. Biomechanical Evaluation of Aortic Valve Stenosis by Means of a Virtual Stress Test: A Fluid-Structure Interaction Study. Ann Biomed Eng 2024; 52:414-424. [PMID: 37957528 DOI: 10.1007/s10439-023-03389-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2023] [Accepted: 10/15/2023] [Indexed: 11/15/2023]
Abstract
The impact of aortic valve stenosis (AS) extends beyond the vicinity of the narrowed leaflets into the left ventricle (LV) and into the systemic vasculature because of highly unpredictable valve behavior and complex blood flow in the ascending aorta that can be attributed to the strong interaction between the narrowed cusps and the ejected blood. These effects can become exacerbated during exercise and may have implications for disease progression, accurate diagnosis, and timing of intervention. In this 3-D patient-specific study, we employ strongly coupled fluid-structure interaction (FSI) modeling to perform a comprehensive biomechanical evaluation of systolic ejection dynamics in a stenosed aortic valve (AV) during increasing LV contraction. Our model predictions reveal that the heterogeneous ∆P vs. Q relationship that was observed in our previous clinical study can be attributed to a non-linear increase (by ~ 1.5-fold) in aortic valve area as LV heart rate increases from 70 to 115 bpm. Furthermore, our results show that even for a moderately stenotic valve, increased LV contraction during exercise can lead to high-velocity flow turbulence (Re = 11,700) in the aorta similar to that encountered with a severely stenotic valve (Re ~ 10,000), with concomitant greater viscous loss (~3-fold increase) and elevated wall stress in the ascending aorta. Our FSI predictions also reveal that individual valve cusps undergo distinct and highly non-linear increases (>100%) in stress during exercise, potentially contributing to progressive calcification. Such quantitative biomechanical evaluations from realistic FSI workflows provide insights into disease progression and can be integrated with current stress testing for AS patients to comprehensively predict hemodynamics and valve function under both baseline and exercise conditions.
Collapse
Affiliation(s)
- Vijay Govindarajan
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA.
- Boston Children's Hospital, Boston, MA, USA.
- Harvard Medical School, Boston, MA, USA.
| | | | - Charles Wanna
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
| | - Hyunggun Kim
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
- Sungkyunkwan University, Suwon, Gyeonggi, Korea
| | - Siddharth Prakash
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
| | - Krishnan B Chandran
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
- The University of Iowa, Iowa City, IA, USA
| | - David D McPherson
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
| | - Nils P Johnson
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX, 77054, USA
| |
Collapse
|
4
|
Govindarajan V, Marshall L, Sahni A, Cetatoiu M, Eickhoff E, Davee J, St Clair N, Schulz N, Hoganson DM, Hammer PE, Ghelani S, Prakash A, Del Nido PJ, Rathod RH. Impact of Age-related change in Caval Flow Ratio on Hepatic Flow Distribution in Fontan. medRxiv 2023:2023.09.06.23295166. [PMID: 37732201 PMCID: PMC10508792 DOI: 10.1101/2023.09.06.23295166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
Background The Fontan operation is a palliative technique for patients born with single ventricle heart disease. The superior vena cava (SVC), inferior vena cava (IVC), and hepatic veins are connected to the pulmonary arteries in a total cavopulmonary connection by an extracardiac (EC) conduit or a lateral tunnel (LT) connection. A balanced hepatic flow distribution (HFD) to both lungs is essential to prevent pulmonary arteriovenous malformations and cyanosis. HFD is highly dependent on the local hemodynamics. Objective The effect of age-related changes in caval inflows on HFD was evaluated using cardiac MRI (CMR) data and patient-specific computational fluid dynamics (CFD) modeling. Methods SVC and IVC flow from 414 Fontan patients were collected to establish a relationship between SVC:IVC flow ratio and age. CFD modeling was performed in 60 (30 EC and 30 LT) patient models to quantify the HFD that corresponded to patient ages of 3, 8, and 15 years, respectively. Results SVC:IVC flow ratio inverted at ∼8 years of age, indicating a clear shift to lower body flow predominance. Our data showed that variation of HFD in response to age-related changes in caval inflows (SVC:IVC = 2,1, and 0.5 corresponded to ages 3, 8, and 15+ respectively) was not significant for EC but statistically significant for LT cohorts. For all three caval inflow ratios, a positive correlation existed between the IVC flow distribution to both the lungs and the HFD. However, as the SVC:IVC ratio changed from 2→0.5 (age 3→15+), the correlation's strength decreased from 0.87→0.64, due to potential flow perturbation as IVC flow momentum increased. Conclusion Our analysis provided quantitative insights into the impact of the changing caval inflows on Fontan's long-term HFD, highlighting the importance of including SVC:IVC variations over time to understand Fontan's long-term hemodynamics. These findings broaden our understanding of Fontan hemodynamics and patient outcomes. Clinical Perspective With improvement in standard of care and management of single ventricle patients with Fontan physiology, the population of adults with Fontan circulation is increasing. Consequently, there is a clinical need to comprehend the impact of patient growth on Fontan hemodynamics. Using CMR data, we were able to quantify the relationship between changing caval inflows and somatic growth. We then used patient-specific computational flow modeling to quantify how this relationship affected the distribution of long-term hepatic flow in extracardiac and lateral tunnel Fontan types. Our findings demonstrated the significance of including SVC:IVC changes over time in CFD modeling to learn more about the long-term hemodynamics of Fontan. Fontan surgical approaches are increasingly planned and optimized using computational flow modeling. For a patient undergoing a Fontan procedure, the workflow presented in this study that takes into account the variations in Caval inflows over time can aid in predicting the long-term hemodynamics in a planned Fontan pathway.
Collapse
|
5
|
Klegerman ME, Moody M, Peng T, Laing ST, Huang S, Govindarajan V, Kim H, Haworth K, Genstler C, Holland C, McPherson DD, Kee P. ULTRASOUND-ENHANCED DEEP ARTERIAL WALL THERAPEUTIC DELIVERY. J Am Coll Cardiol 2023. [DOI: 10.1016/s0735-1097(23)01248-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
|
6
|
Klegerman ME, Moody MR, Huang SL, Peng T, Laing ST, Govindarajan V, Danila D, Tahanan A, Rahbar MH, Vela D, Genstler C, Haworth KJ, Holland CK, McPherson DD, Kee PH. Demonstration of ultrasound-mediated therapeutic delivery of fibrin-targeted pioglitazone-loaded echogenic liposomes into the arterial bed for attenuation of peri-stent restenosis. J Drug Target 2023; 31:109-118. [PMID: 35938912 DOI: 10.1080/1061186x.2022.2110251] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Peri-stent restenosis following stent implantation is a major clinical problem. We have previously demonstrated that ultrasound-facilitated liposomal delivery of pioglitazone (PGN) to the arterial wall attenuated in-stent restenosis. To evaluate ultrasound mediated arterial delivery, in Yucatan miniswine, balloon inflations were performed in the carotid and subclavian arteries to simulate stent implantation and induce fibrin formation. The fibrin-binding peptide, GPRPPGGGC, was conjugated to echogenic liposomes (ELIP) containing dinitrophenyl-L-alanine-labelled pioglitazone (DNP-PGN) for targeting purposes. After pre-treating the arteries with nitroglycerine, fibrin-binding peptide-conjugated PGN-loaded ELIP (PAFb-DNP-PGN-ELIP also termed atheroglitatide) were delivered to the injured arteries via an endovascular catheter with an ultrasound core, either with or without ultrasound application (EKOSTM Endovascular System, Boston Scientific). In arteries treated with atheroglitatide, there was substantial delivery of PGN into the superficial layers (5 µm from the lumen) of the arteries with and without ultrasound, [(1951.17 relative fluorescence units (RFU) vs. 1901.17 RFU; P-value = 0.939)]. With ultrasound activation there was increased penetration of PGN into the deeper arterial layers (up to 35 µm from the lumen) [(13195.25 RFU vs. 7681.00 RFU; P-value = 0.005)]. These pre-clinical data demonstrate ultrasound mediated therapeutic vascular delivery to deeper layers of the injured arterial wall. This model has the potential to reduce peri- stent restenosis.
Collapse
Affiliation(s)
- Melvin E Klegerman
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Melanie R Moody
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Shao-Ling Huang
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Tao Peng
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Susan T Laing
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Vijay Govindarajan
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Delia Danila
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Amirali Tahanan
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA.,Center for Clinical and Translational Sciences, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Mohammad H Rahbar
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA.,Center for Clinical and Translational Sciences, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Deborah Vela
- Cardiovascular Pathology Research Department, Texas Heart Institute, Houston, TX, USA
| | | | - Kevin J Haworth
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH, USA
| | - Christy K Holland
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH, USA
| | - David D McPherson
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Patrick H Kee
- Department of Internal Medicine, The University of Texas Health Science Center at Houston, Houston, TX, USA
| |
Collapse
|
7
|
Govindarajan V, Kolanjiyil A, Johnson NP, Kim H, Chandran KB, McPherson DD. Improving transcatheter aortic valve interventional predictability via fluid-structure interaction modelling using patient-specific anatomy. R Soc Open Sci 2022; 9:211694. [PMID: 35154799 PMCID: PMC8826300 DOI: 10.1098/rsos.211694] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 01/04/2022] [Indexed: 05/03/2023]
Abstract
Transcatheter aortic valve replacement (TAVR) is now a standard treatment for high-surgical-risk patients with severe aortic valve stenosis. TAVR is being explored for broader indications including degenerated bioprosthetic valves, bicuspid valves and for aortic valve (AV) insufficiency. It is, however, challenging to predict whether the chosen valve size, design or its orientation would produce the most-optimal haemodynamics in the patient. Here, we present a novel patient-specific evaluation framework to realistically predict the patient's AV performance with a high-fidelity fluid-structure interaction analysis that included the patient's left ventricle and ascending aorta (AAo). We retrospectively evaluated the pre- and post-TAVR dynamics of a patient who underwent a 23 mm TAVR and evaluated against the patient's virtually de-calcified AV serving as a hypothetical benchmark. Our model predictions were consistent with clinical data. Stenosed AV produced a turbulent flow during peak-systole, while aortic flow with TAVR and de-calcified AV were both in the laminar-to-turbulent transitional regime with an estimated fivefold reduction in viscous dissipation. For TAVR, dissipation was highest during early systole when valve deformation was the greatest, suggesting that an efficient valve opening may reduce energy loss. Our study demonstrates that such patient-specific modelling frameworks can be used to improve predictability and in the planning of AV interventions.
Collapse
Affiliation(s)
- Vijay Govindarajan
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX 77054, USA
| | - Arun Kolanjiyil
- Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Nils P. Johnson
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX 77054, USA
| | - Hyunggun Kim
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX 77054, USA
- Department of Bio-Mechatronic Engineering, Sungkyunkwan University, Suwon, Gyeonggi, Korea
| | - Krishnan B. Chandran
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX 77054, USA
- Roy J. Carver Department of Biomedical Engineering, The University of Iowa, Iowa City, IA, USA
| | - David D. McPherson
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science at Houston, 1881 East Road, Houston, TX 77054, USA
| |
Collapse
|
8
|
Govindarajan V, Kolanjiyil AV, Johnson N, Kim H, Chandran K, McPherson D. PREDICTIVE EVALUATION OF PATIENT-SPECIFIC PERFORMANCE OF A TRANSCATHETER AORTIC VALVE REPLACEMENT. J Am Coll Cardiol 2021. [DOI: 10.1016/s0735-1097(21)03094-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
9
|
Hoganson DM, Govindarajan V, Schulz NE, Eickhoff ER, Breitbart R, Marx G, Nido PD, Hammer P. COMPUTATIONAL FLUID DYNAMICS MODELING OF HEPATIC-PULMONARY BLOOD FLOW FOR FONTAN PLANNING IN PATIENTS WITH INTERRUPTED INFERIOR VENA CAVA. J Am Coll Cardiol 2021. [DOI: 10.1016/s0735-1097(21)01809-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
10
|
Grover SP, Bendapudi PK, Yang M, Merrill-Skoloff G, Govindarajan V, Mitrophanov AY, Flaumenhaft R. Injury measurements improve interpretation of thrombus formation data in the cremaster arteriole laser-induced injury model of thrombosis. J Thromb Haemost 2020; 18:3078-3085. [PMID: 33456401 PMCID: PMC7805486 DOI: 10.1111/jth.15059] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Background The cremaster arteriole laser-induced injury model is a powerful technique with which to investigate the molecular mechanisms that drive thrombus formation. This model is capable of direct visualization and quantification of accumulation of thrombus constituents, including both platelets and fibrin. However, a large degree of variability in platelet accumulation and fibrin formation is observed between thrombi. Strategies to understand this variability will enhance performance and standardization of the model. We determined whether ablation injury size contributes to variation in platelet accumulation and fibrin formation and, if so, whether incorporating ablation injury size into measurements reduces variation. Methods Thrombus formation was initiated by laser-induced injury of cremaster arterioles of mice (n=59 injuries). Ablation injuries within the vessel wall were consistently identified and quantified by measuring the length of vessel wall injury observed immediately following laser-induced disruption. Platelet accumulation and fibrin formation as detected by fluorescently-labeled antibodies were captured by digital intra-vital microscopy. Results Laser-induced disruption of the vessel wall resulted in ablation injuries of variable length (18-95 μm) enabling interrogation of the relationship between injury severity and thrombus dynamics. Strong positive correlations were observed between vessel injury length and both platelet and fibrin when the data are transformed as area under the curve (Spearman r = 0.80 and 0.76 respectively). Normalization of area under the curve measurements by injury length reduced intraclass coefficients of variation among thrombi and improved hypothesis testing when comparing different data sets. Conclusions Measurement of vessel wall injury length provides a reliable and robust marker of injury severity. Injury length can effectively normalize measurements of platelet accumulation and fibrin formation improving data interpretation and standardization.
Collapse
Affiliation(s)
- Steven P Grover
- Division of Hemostasis and Thrombosis and Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
- Division of Oncology and Hematology and Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Pavan K Bendapudi
- Division of Hemostasis and Thrombosis and Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Moua Yang
- Division of Hemostasis and Thrombosis and Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Glenn Merrill-Skoloff
- Division of Hemostasis and Thrombosis and Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Vijay Govindarajan
- Department of Defense Biotechnology High Performance Computing Software Applications Institute (BHSAI), Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Development Command, Fort Detrick, Maryland; The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland, USA
| | - Alexander Y Mitrophanov
- Department of Defense Biotechnology High Performance Computing Software Applications Institute (BHSAI), Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Development Command, Fort Detrick, Maryland; The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland, USA
| | - Robert Flaumenhaft
- Division of Hemostasis and Thrombosis and Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| |
Collapse
|
11
|
Mitrophanov AY, Merrill-Skoloff G, Grover SP, Govindarajan V, Kolanjiyil A, Hariprasad DS, Unnikrishnan G, Flaumenhaft R, Reifman J. Injury Length and Arteriole Constriction Shape Clot Growth and Blood-Flow Acceleration in a Mouse Model of Thrombosis. Arterioscler Thromb Vasc Biol 2020; 40:2114-2126. [PMID: 32640902 DOI: 10.1161/atvbaha.120.314786] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
OBJECTIVE Quantitative relationships between the extent of injury and thrombus formation in vivo are not well understood. Moreover, it has not been investigated how increased injury severity translates to blood-flow modulation. Here, we investigated interconnections between injury length, clot growth, and blood flow in a mouse model of laser-induced thrombosis. Approach and Results: Using intravital microscopy, we analyzed 59 clotting events collected from the cremaster arteriole of 14 adult mice. We regarded injury length as a measure of injury severity. The injury caused transient constriction upstream and downstream of the injury site resulting in a 50% reduction in arteriole diameter. The amount of platelet accumulation and fibrin formation did not depend on arteriole diameter or deformation but displayed an exponentially increasing dependence on injury length. The height of the platelet clot depended linearly on injury length and the arteriole diameter. Upstream arteriolar constriction correlated with delayed upstream velocity increase, which, in turn, determined downstream velocity. Before clot formation, flow velocity positively correlated with the arteriole diameter. After the onset of thrombus growth, flow velocity at the injury site negatively correlated with the arteriole diameter and with the size of the above-clot lumen. CONCLUSIONS Injury severity increased platelet accumulation and fibrin formation in a persistently steep fashion and, together with arteriole diameter, defined clot height. Arterial constriction and clot formation were characterized by a dynamic change in the blood flow, associated with increased flow velocity.
Collapse
Affiliation(s)
- Alexander Y Mitrophanov
- From the DoD Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, US Army Medical Research and Development Command, Ft. Detrick, MD (A.Y.M., V.G., A.K., D.S.H., G.U., J.R.).,The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc, Bethesda, MD (A.Y.M., V.G., A.K., D.S.H., G.U.)
| | - Glenn Merrill-Skoloff
- Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (G.M.-S., S.P.G., R.F.)
| | - Steven P Grover
- Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (G.M.-S., S.P.G., R.F.)
| | - Vijay Govindarajan
- From the DoD Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, US Army Medical Research and Development Command, Ft. Detrick, MD (A.Y.M., V.G., A.K., D.S.H., G.U., J.R.).,The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc, Bethesda, MD (A.Y.M., V.G., A.K., D.S.H., G.U.)
| | - Arun Kolanjiyil
- From the DoD Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, US Army Medical Research and Development Command, Ft. Detrick, MD (A.Y.M., V.G., A.K., D.S.H., G.U., J.R.).,The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc, Bethesda, MD (A.Y.M., V.G., A.K., D.S.H., G.U.)
| | - Daniel S Hariprasad
- From the DoD Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, US Army Medical Research and Development Command, Ft. Detrick, MD (A.Y.M., V.G., A.K., D.S.H., G.U., J.R.).,The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc, Bethesda, MD (A.Y.M., V.G., A.K., D.S.H., G.U.)
| | - Ginu Unnikrishnan
- From the DoD Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, US Army Medical Research and Development Command, Ft. Detrick, MD (A.Y.M., V.G., A.K., D.S.H., G.U., J.R.).,The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc, Bethesda, MD (A.Y.M., V.G., A.K., D.S.H., G.U.)
| | - Robert Flaumenhaft
- Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA (G.M.-S., S.P.G., R.F.)
| | - Jaques Reifman
- From the DoD Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, US Army Medical Research and Development Command, Ft. Detrick, MD (A.Y.M., V.G., A.K., D.S.H., G.U., J.R.)
| |
Collapse
|
12
|
Govindarajan V, Zhu S, Li R, Lu Y, Diamond SL, Reifman J, Mitrophanov AY. Impact of Tissue Factor Localization on Blood Clot Structure and Resistance under Venous Shear. Biophys J 2019; 114:978-991. [PMID: 29490257 PMCID: PMC5984989 DOI: 10.1016/j.bpj.2017.12.034] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 11/14/2017] [Accepted: 12/27/2017] [Indexed: 01/20/2023] Open
Abstract
The structure and growth of a blood clot depend on the localization of tissue factor (TF), which can trigger clotting during the hemostatic process or promote thrombosis when exposed to blood under pathological conditions. We sought to understand how the growth, structure, and mechanical properties of clots under flow are shaped by the simultaneously varying TF surface density and its exposure area. We used an eight-channel microfluidic device equipped with a 20- or 100-μm-long collagen surface patterned with lipidated TF of surface densities ∼0.1 and ∼2 molecules/μm2. Human whole blood was perfused at venous shear, and clot growth was continually measured. Using our recently developed computational model of clot formation, we performed simulations to gain insights into the clot’s structure and its resistance to blood flow. An increase in TF exposure area resulted not only in accelerated bulk platelet, thrombin, and fibrin accumulation, but also in increased height of the platelet mass and increased clot resistance to flow. Moreover, increasing the TF surface density or exposure area enhanced platelet deposition by approximately twofold, and thrombin and fibrin generation by greater than threefold, thereby increasing both clot size and its viscous resistance. Finally, TF effects on blood flow occlusion were more pronounced for the longer thrombogenic surface than for the shorter one. Our results suggest that TF surface density and its exposure area can independently enhance both the clot’s occlusivity and its resistance to blood flow. These findings provide, to our knowledge, new insights into how TF affects thrombus growth in time and space under flow.
Collapse
Affiliation(s)
- Vijay Govindarajan
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, Maryland
| | - Shu Zhu
- Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania; Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Ruizhi Li
- Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania; Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Yichen Lu
- Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania; Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Scott L Diamond
- Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania; Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Jaques Reifman
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, Maryland.
| | - Alexander Y Mitrophanov
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, Maryland
| |
Collapse
|
13
|
Govindarajan V, Mousel J, Udaykumar HS, Vigmostad SC, McPherson DD, Kim H, Chandran KB. Synergy between Diastolic Mitral Valve Function and Left Ventricular Flow Aids in Valve Closure and Blood Transport during Systole. Sci Rep 2018; 8:6187. [PMID: 29670148 PMCID: PMC5906696 DOI: 10.1038/s41598-018-24469-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 03/27/2018] [Indexed: 11/30/2022] Open
Abstract
Highly resolved three-dimensional (3D) fluid structure interaction (FSI) simulation using patient-specific echocardiographic data can be a powerful tool for accurately and thoroughly elucidating the biomechanics of mitral valve (MV) function and left ventricular (LV) fluid dynamics. We developed and validated a strongly coupled FSI algorithm to fully characterize the LV flow field during diastolic MV opening under physiologic conditions. Our model revealed that distinct MV deformation and LV flow patterns developed during different diastolic stages. A vortex ring that strongly depended on MV deformation formed during early diastole. At peak E wave, the MV fully opened, with a local Reynolds number of ~5500, indicating that the flow was in the laminar-turbulent transitional regime. Our results showed that during diastasis, the vortex structures caused the MV leaflets to converge, thus increasing mitral jet’s velocity. The vortex ring became asymmetrical, with the vortex structures on the anterior side being larger than on the posterior side. During the late diastolic stages, the flow structures advected toward the LV outflow tract, enhancing fluid transport to the aorta. This 3D-FSI study demonstrated the importance of leaflet dynamics, their effect on the vortex ring, and their influence on MV function and fluid transport within the LV during diastole.
Collapse
Affiliation(s)
- Vijay Govindarajan
- Department of Biomedical Engineering, The University of Iowa, Iowa City, IA, USA.,Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas McGovern Medical School, Houston, TX, USA
| | - John Mousel
- Department of Biomedical Engineering, The University of Iowa, Iowa City, IA, USA
| | - H S Udaykumar
- Department of Biomedical Engineering, The University of Iowa, Iowa City, IA, USA
| | - Sarah C Vigmostad
- Department of Biomedical Engineering, The University of Iowa, Iowa City, IA, USA
| | - David D McPherson
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas McGovern Medical School, Houston, TX, USA
| | - Hyunggun Kim
- Division of Cardiovascular Medicine, Department of Internal Medicine, The University of Texas McGovern Medical School, Houston, TX, USA. .,Department of Biomechatronic Engineering, Sungkyunkwan University, Suwon, Gyeonggi, Korea.
| | - Krishnan B Chandran
- Department of Biomedical Engineering, The University of Iowa, Iowa City, IA, USA.
| |
Collapse
|
14
|
Govindarajan V, Kim H, Chandran K, McPherson D. FLUID STRUCTURE INTERACTION SIMULATION TO IMPROVE EVALUATION OF MITRAL VALVE REPAIR. J Am Coll Cardiol 2018. [DOI: 10.1016/s0735-1097(18)32518-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
15
|
Govindarajan V, Rakesh V, Reifman J, Mitrophanov AY. Computational Study of Thrombus Formation and Clotting Factor Effects under Venous Flow Conditions. Biophys J 2017; 110:1869-1885. [PMID: 27119646 PMCID: PMC4850327 DOI: 10.1016/j.bpj.2016.03.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 03/03/2016] [Accepted: 03/08/2016] [Indexed: 11/24/2022] Open
Abstract
A comprehensive understanding of thrombus formation as a physicochemical process that has evolved to protect the integrity of the human vasculature is critical to our ability to predict and control pathological states caused by a malfunctioning blood coagulation system. Despite numerous investigations, the spatial and temporal details of thrombus growth as a multicomponent process are not fully understood. Here, we used computational modeling to investigate the temporal changes in the spatial distributions of the key enzymatic (i.e., thrombin) and structural (i.e., platelets and fibrin) components within a growing thrombus. Moreover, we investigated the interplay between clot structure and its mechanical properties, such as hydraulic resistance to flow. Our model relied on the coupling of computational fluid dynamics and biochemical kinetics, and was validated using flow-chamber data from a previous experimental study. The model allowed us to identify the distinct patterns characterizing the spatial distributions of thrombin, platelets, and fibrin accumulating within a thrombus. Our modeling results suggested that under the simulated conditions, thrombin kinetics was determined predominantly by prothrombinase. Furthermore, our simulations showed that thrombus resistance imparted by fibrin was ∼30-fold higher than that imparted by platelets. Yet, thrombus-mediated bloodflow occlusion was driven primarily by the platelet deposition process, because the height of the platelet accumulation domain was approximately twice that of the fibrin accumulation domain. Fibrinogen supplementation in normal blood resulted in a nonlinear increase in thrombus resistance, and for a supplemented fibrinogen level of 48%, the thrombus resistance increased by ∼2.7-fold. Finally, our model predicted that restoring the normal levels of clotting factors II, IX, and X while simultaneously restoring fibrinogen (to 88% of its normal level) in diluted blood can restore fibrin generation to ∼78% of its normal level and hence improve clot formation under dilution.
Collapse
Affiliation(s)
- Vijay Govindarajan
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, Maryland
| | - Vineet Rakesh
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, Maryland
| | - Jaques Reifman
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, Maryland.
| | - Alexander Y Mitrophanov
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, Maryland
| |
Collapse
|
16
|
Sen S, Govindarajan V, Pelliccione CJ, Wang J, Miller DJ, Timofeeva EV. Surface Modification Approach to TiO2 Nanofluids with High Particle Concentration, Low Viscosity, and Electrochemical Activity. ACS Appl Mater Interfaces 2015; 7:20538-20547. [PMID: 26322861 DOI: 10.1021/acsami.5b05864] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This study presents a new approach to the formulation of functional nanofluids with high solid loading and low viscosity while retaining the surface activity of nanoparticles, in particular, their electrochemical response. The proposed methodology can be applied to a variety of functional nanomaterials and enables exploration of nanofluids as a medium for industrial applications beyond heat transfer fluids, taking advantage of both liquid behavior and functionality of dispersed nanoparticles. The highest particle concentration achievable with pristine 25 nm titania (TiO2) nanoparticles in aqueous electrolytes (pH 11) is 20 wt %, which is limited by particle aggregation and high viscosity. We have developed a scalable one-step surface modification procedure for functionalizing those TiO2 nanoparticles with a monolayer coverage of propyl sulfonate groups, which provides steric and charge-based separation of particles in suspension. Stable nanofluids with TiO2 loadings up to 50 wt % and low viscosity are successfully prepared from surface-modified TiO2 nanoparticles in the same electrolytes. Viscosity and thermal conductivity of the resulting nanofluids are evaluated and compared to nanofluids prepared from pristine nanoparticles. Furthermore, it is demonstrated that the surface-modified titania nanoparticles retain more than 78% of their electrochemical response as compared to that of the pristine material. Potential applications of the proposed nanofluids include, but are not limited to, electrochemical energy storage and catalysis, including photo- and electrocatalysis.
Collapse
Affiliation(s)
- Sujat Sen
- Energy Systems Division and ‡Electron Microscopy Center - Center for Nanoscale Materials, Argonne National Laboratory , Lemont, Illinois 60439, United States
| | - Vijay Govindarajan
- Energy Systems Division and ‡Electron Microscopy Center - Center for Nanoscale Materials, Argonne National Laboratory , Lemont, Illinois 60439, United States
| | - Christopher J Pelliccione
- Energy Systems Division and ‡Electron Microscopy Center - Center for Nanoscale Materials, Argonne National Laboratory , Lemont, Illinois 60439, United States
| | - Jie Wang
- Energy Systems Division and ‡Electron Microscopy Center - Center for Nanoscale Materials, Argonne National Laboratory , Lemont, Illinois 60439, United States
| | - Dean J Miller
- Energy Systems Division and ‡Electron Microscopy Center - Center for Nanoscale Materials, Argonne National Laboratory , Lemont, Illinois 60439, United States
| | - Elena V Timofeeva
- Energy Systems Division and ‡Electron Microscopy Center - Center for Nanoscale Materials, Argonne National Laboratory , Lemont, Illinois 60439, United States
| |
Collapse
|
17
|
|
18
|
Fayez R, AlMuntashery A, Bodie G, Almamar A, Gill R, Raîche I, Mueller C, AlMuntashery A, Fayez R, AlMuntashery A, Moustarah F, Khokhotva M, Anvari M, Kwong J, Elkassem S, Bonrath E, Zevin B, Sockalingam S, Smith C, Smith C, Whitlock K, Gill R, Suri M, Palter V, Wakeam E, Khan R, Martelli V, Malik A, Young P, Daigle C, McCreery G, Seth R, Paskar D, Sudarshan M, Richardson D, Haggar F, Davis V, Rivard J, Agzarian J, Racz J, Winocour J, Zilbert N, Decker C, Neumann K, Gosney J, Wissanji H, Chadi S, Alhabboubi M, Partridge E, Alhabboubi M, Olszewski M, Chan R, Nadler A, Hameed U, Brotherhood H, Menezes A, MacDonald B, Rakovich G, Hilsden R, Merani S, Davis P, Davis P, Cools-Lartigue J, Ojah J, Julien F, Carter D, Pitt D, Banks B, Rudovics A, Ravichandran P, Anantha R, Aad I, Kholdebarin R, Aird L, Wong S, Payne J, Hallet J, Farries L, Raiche I, Botkin C, Morency D, Berger-Richardson D, Isa A, Dupuis I, Schweigert M, Koubi S, Ernjakovic M, Grant K, Cools-Lartigue J, Carrott P, Stafford T, Malthaner R, Sudarshan M, Hanna W, Lee L, Markar S, Razzak R, Bharadwaj S, Ashrafi A, Ouellette D, Fergusson D, Forster A, Boushey R, Porter G, Johnson P, Gomes T, Chan B, Auer R, Moloo H, Mamdani M, Markar S, Al-Omran M, Al-Obaid O, Boushey R, Lim DR, Min BS, Baik SH, Gordon P, Kim NK, Lo A, Pinsk I, Bottoni D, Brown C, Raval M, Cheng H, Wong C, Johnston N, Farrokhyar F, Stephen W, Kelly S, Lindsay L, Forbes S, Knickle C, Bouchard A, Parry N, Leslie K, Ott M, Coughlin S, Gazala S, Gazala S, Donahoe L, Walker K, Li C, Alnasser S, Schweigert M, Schweigert M, Zhuruk A, Hanouf A, Vanounou T, Karanicolas P, Aubin JM, Yeung J, Dumitra S, Simoneau E, Vanounou T, Howe B, Hawel J, Jang JH, Bertens K, Rekman J, Wei A, Dumitra S, Koubi S, Ouellet JF, Wei A, Covelli A, Maniar R, Sun S, Davis V, Brackstone M, Boissonneault R, Kim S, Baliski C, Gazala S, Hameed U, Sudarshan M, Arnaout A, Wedman D, Nostedt M, Hebbard P, Shetty S, Dixon M, Wei A, Dixon M, Kazazian K, Lemke M, Wells B, Musselman R, Zih FSW, Menezes A, Nassif M, Leon-Carlyle M, Wei A, Krotneva S, Bradley N, Trabulsi N, Trabulsi N, Chin-Lenn L, Cheng H, Petrucci A, Sandhu L, Neville A, Lee L, Li C, Yang I, Prabhu KL, Melich G, Knowles S, Richardson D, Borowiec A, Hallet J, Boissonneault R, Kolozsvari N, Hallet J, Tuttle P, VanHouwelingen L, Haggar F, Boulanger-Gobeil C, Chan B, Chan B, Richardson D, Musselman R, Melich G, Phang P, Goldstein L, Wen C, Lebrun A, Chadi S, Roy M, Villeneuve S, AlMuntashery A, Demyttenaere S, Christou N, Court O, Fayez R, Demyttenaere S, Christou N, Court O, Bonrath E, Hagen J, Okrainec A, Sullivan P, Grantcharov T, Sharma A, Karmali S, Birch D, Majumdar S, Wang X, Tuepah R, Klarenbach S, Birch D, Karmali S, Sharma A, Padwal R, Smith C, Haggar F, Moloo H, Poulin E, Martel G, Yelle JD, Mamazza J, Jackson T, Penner T, Pitzul K, Urbach D, Okrainec A, Villeneuve S, Roy M, Fayez R, Demyttenaere S, Christou N, Court O, Roy M, Villeneuve S, AlMuntashery A, Demyttenaere S, Christou N, Court O, Fayez R, Demyttenaere S, Court O, Christou N, Biertho L, Hould FS, Lebel S, Lescelleur O, Marceau S, Marceau P, Biron S, Grantcharov T, Sharma A, Yusuf S, Okrainec A, Pitzul K, Urbach D, Jackson T, Lindsay D, Sullivan P, Smith L, Zevin B, Dedy N, Grantcharov T, Bonrath E, Aggarwal R, Grantcharov T, Cassin S, Crawford S, Pitzul K, Khan A, Hawa R, Jackson T, Okrainec A, Brar B, Mamazza J, Raîche I, Yelle JD, Haggar F, Moloo H, Brar B, Haggar F, Dent R, Mamazza J, Raîche I, Moloo H, Gill R, Ali T, Shi X, Birch D, Karmali S, Whitlock K, Shi X, Sarkhosh K, Birch D, Karmali S, Turner J, Nation P, Wizzard P, Brubaker P, Gisalet D, Wales P, Grantcharov T, Tien H, Spencer F, Brenneman F, Kowal J, Wiseman S, Fraser S, Vedel I, Deban M, Holcroft C, Monette M, Monette J, Bergman S, Bell C, Stukel T, Urbach D, Mueller T, Lucykx V, Lukowski C, Compston C, Churchill T, Khadaroo R, Grantcharov T, Vogt K, Dubois L, Gray D, Ananth A, Tai LH, Lam T, Falls T, Souza C, Bell J, Auer R, Crawford S, Parry N, Leslie K, Alhabboubi M, St-Louis E, Deckelbaum D, Razek T, Feldman L, Khwaja K, Porter G, Johnson P, Boushey R, Moloo H, Raiche I, Mamazza J, Schiller D, Eurich D, Sawyer M, Vergis A, Unger B, Hardy K, Andrew C, Gillman L, Park J, Prodger J, Kelly W, Kelly S, Prodger D, Ewara E, Martin J, Sarma S, Chu M, Schlachta C, Zaric G, Al-Ali K, Briggs K, George R, Murnaghan M, Leung A, Regehr G, Moulton CA, Mahmud S, Metcalfe J, McKay A, Park J, Hochman D, Burkle F, Redmond A, McQueen K, Desrosiers E, Gilbert A, Leslie K, Ott M, Sudarshan M, Jessula S, Alburakan A, Deckelbaum D, Razek T, Iqbal S, Khwaja K, Aikins C, Sudarshan M, Deckelbaum D, Iqbal S, Khwaja K, Razek T, Roberts N, Moulton CA, Murnaghan M, Cil T, Marshall J, Pederson K, Erichsen S, White J, Aarts MA, Okrainec A, Victor J, Pearsall E, McLeod R, Jackson T, Okrainec A, Penner T, Urbach D, Karimuddin A, Hall C, Bawan S, Malik S, Hayashi A, Gill R, McAlister C, Zhang N, DesRosiers E, Mills A, Crozier M, Lee L, Maxwell J, Partridge E, Chad S, Steigerwald S, Mapiour D, Roberts D, MacPherson C, Donahoe L, Mercer D, Hopman W, Latulippe JF, Knowles S, Moffat B, Parry N, Leslie K, Switzer N, Khadaroo R, Tul Y, Widder S, Molinari M, Levy A, Johnson P, Bailey J, Molinari M, Hayden J, Johnson P, Benlolo S, Marcus V, Ferri L, Finley R, Anderson D, Gagné JP, Chan S, Wong S, Li J, Michael A, Choi D, Liu E, Hoogenes J, Dath D, Aubin JM, Mew D, McConnell Y, Classen D, Kanthan S, Croome K, Kovacs M, Lazo-Langner A, Hernandez-Alejandro R, Vogt K, Crawford S, Parry N, Leslie K, Khoshgoo N, Iwasiow B, Keijzer R, Brown C, Isa D, Pace D, Widder S, Tul Y, Primrose M, Hudson D, Khadaroo R, Lauzier F, Mailloux O, Trottier V, ARchambault P, Zarychanski R, Turgeon A, Mailloux O, Hardy P, Muirhead R, Masters J, Haggar F, Poulin HME, Martel G, Mamazza J, Milbrandt C, Keijzer R, Sideris L, Grenier-Vallée P, Latulippe JF, Dubé P, Kurashima Y, Kaneva P, Feldman L, Fried G, Vassiliou M, Kwan AL, Fraser S, Solymosi N, Rauh N, Dubecz A, Renz M, Ofner D, Stein H, Borgaonkar M, Crystal P, Easson A, Escallon J, Reedijk M, Cil T, Leong W, McCready D, Clifton J, Mayo J, Finley R, Noreau-Nguyen M, Mulder D, Ferri L, Markar S, Hong J, Low D, Maslow A, Davignon K, Ng T, Tan L, Aruranian J, Kosa S, Ferri L, Murphy G, Allison F, Moshonov H, Darling G, Waddell T, De Perrot M, Cypel M, Yasufuku K, Keshavjee S, Paul N, Pierre A, Darling G, Pedneault C, Marcus V, Mulder D, Ferri L, Low D, Roa W, Löbenberg R, McEwan S, Bédard E, Louie B, Farivar A, McHugh S, Aye R, Tan-Tam C, De Vera M, Bond R, Ong S, Johal B, Schellenberg D, Po M, Nissar S, Lund C, Ahmadi S, Wakil N, Rakovich G, Beauchamps G, Preston S, Baker C, Low D, Campbell G, Malthaner R, Bethune D, Henteleff H, Johnston M, Buduhan G, Coughlin HE, Roth L, Bhandari M, Malthaner R, Johnson J, Kutsogiannis J, Bédard E, Rammohan K, Stewart K, Bédard E, Buduhan G, Gruchy J, Xu Z, Buduhan G, Ferri L, Mulder D, Ncuti A, Neville A, Kaneva P, Watson D, Vassiliou M, Carli F, Feldman L, Av R, Mayrand S, Franco E, Ferri L, Dubecz A, Renz M, Stadlhuber R, Ofner D, Stein H, Renz M, Dubecz A, Solymosi N, Thumfart L, Ofner D, Stein H, Croome K, Leeper R, Hernandez R, Livingstone S, Sapp J, Woodhall D, Alwayn I, Bergman S, Lam-McCulloch J, Balaa F, Jayaraman S, Quan D, Wei A, Guyatt G, Rekman J, Fairfull-Smith R, Mimeault R, Balaa F, Martel G, Boehnert M, Bazerbachi F, Knaak J, Selzner N, McGilvray I, Rotstein O, Adeyi O, Levy G, Keshavjee S, Grant D, Selzner M, Khalil JA, Jamal M, Chaudhury P, Zogopoulos G, Petrakos P, Tchervenkov J, Barkun J, Jamal M, Hassanain M, Chaudhury P, Wong S, Salman A, Tran T, Metrakos P, Groeschl R, Geller D, Marsh J, Gamblin T, Croome K, Croome K, Quan D, Hernandez R, Kim P, Greig PD, Gallinger S, Moulton CA, Wei A, Fischer S, Cleary S, Vogt K, Hernandez-Alejandro R, Gray D, Aubin J, Fairfull-Smith J, Mimeault R, Balaa F, Martel G, Devitt K, Ramjaun A, Gallingher S, Alabbad S, Constantinos D, Hassanein M, Barkun J, Metrakos P, Paraskevas S, Chaudhury P, Tchervenkov J, Borgaonkar M, Tanyingoh D, Dixon E, Kaplan G, Myers R, Howard T, Sutherland F, Zyromski N, Ball C, Coburn N, Moulton CA, Cleary S, Law C, Greig P, Steven G, Baxter N, Fitch M, Wright F, Hochman D, Wirtzfeld D, McKay A, Yaffe C, Yip B, Silverman R, Park J, McConnell Y, Temple W, Mack L, Schiller D, Bathe O, Sawyer M, Scott L, Vandenberg T, Perera F, Potvin K, Chambers A, Loungnarath R, DeBroux É, Lavertu S, Donath D, Ayoub JP, Tehfé M, Richard C, Cornacchi S, Heller B, Farrokhyar F, Babra M, Lovrics P, Liberto C, Ghosh S, McLean R, Schiller D, Jackson T, Okrainec A, Penner T, Urbach D, Dumitra S, Duplisea J, Wexler S, Seely J, Smylie J, Knight K, Robertson S, Watters J, Zhang T, Arneout A, Hochman D, Wirtzfeld D, McKay A, Yip B, Yaffe C, Silverman R, Park J, Baxter N, Yun L, Rakovitch E, Wright F, Warner E, McCready D, Hodgson N, Quan M, Natarajan B, Govindarajan V, Thomas P, Loggie B, Brar S, Mahar A, Law C, Coburn N, Devitt K, Wiebe M, Bathe O, McLeod R, Baxter N, Gagliardi A, Kennedy E, Urbach D, Brar S, Mahar A, Law C, Coburn N, Zih F, Rosario C, Dennis J, Gingras AC, Swallow C, Ko YJ, Rowsell C, Law C, Saskin R, Quan ML, Xie M, McLaughlin K, Marginean C, Moyana T, Moloo H, Boushey R, Auer R, Razik R, Haase E, Mathieson A, Smith A, Swallow C, Barnes A, Scheer A, Moloo H, Boushey R, Sabri E, Auer R, Reidel K, Trabulsi N, Meterissian S, Tamblyn R, Mayo N, Meguerditchian A, Brown J, Hamm J, Phang P, Raval M, Brown C, Devitt K, Wiebe M, Bathe O, McLeod R, Taylor B, Urbach D, Reidel K, Mayo N, Tamblyn R, Meguerditchian A, Hamm J, Wiseman S, Patakfalvi L, Nassif M, Turcotte R, Nichols A, Meguerditchian A, Riedel K, Winslade N, Grégoire JP, Meterissian S, Abrahamovicz M, Megueerditchian A, Pasieka J, McMillan C, Lipa J, Snell L, Sudarshan M, Dumitra S, Duplisea J, Wexler S, Meterissian S, Tomlinson G, Kennedy E, Wei A, Baxter N, Urbach D, Liberman A, Charlebois P, Stein B, Ncuti A, Vassiliou M, Fried G, Feldman L, Capretti G, Power A, Liberman A, Charlebois P, Stein B, Kaneva P, Carli F, Fried G, Feldman L, Carli F, Charlebois P, Stein B, Liberman A, Kaneva P, Augustin B, Gamsa A, Kim DJ, Vassiliou M, Feldman L, Boushey R, Moloo H, Vu L, Chan S, Phang P, Gown A, Jones S, Wiseman S, Jeong DH, Hur H, Baik SH, Kim NK, Faria J, Min BS, Lumb K, Colquhoun P, Porter G, Johnson P, Baxter N, Schmocker S, Huang H, Victor J, Krzyzanowska MK, Brierley J, McLeod R, Kennedy E, Milot H, Desrosiers E, Lebrun A, Drolet S, Bouchard A, Grégoire R, Vuong T, Loungnarath R, DeBroux E, Liberman A, Charlebois P, Stein B, Richard C, Capretti G, Kaneva P, Neville A, Carli F, Liberman S, Charlebois P, Stein B, Vassiliou M, Fried G, Feldman L, Milot H, Drolet S, Bouchard A, Grégoire R, Powell R, Fowler A, Mathieson A, Martin K, Vogt K, Ott M, Pereira G, Einarsdottir K, Moloo H, Boushey R, Mamazza J, Bouchard A, Gagné J, Grégoire R, Thibault C, Bouchard P, Gomes T, Musselman R, Auer R, Moloo H, Mamdani M, Al-Omran M, Boushey R, AlObeed O, Armstrong J. Canadian Surgery Forum1 Is laparoscopic sleeve gastrectomy a reasonable stand-alone procedure for super morbidly obese patients?2 Postoperative monitoring requirements of patients with obstructive sleep apnea undergoing bariatric surgery3 Role of relaparoscopy in the diagnosis and treatment of bariatric complications in the early postoperative period4 Changes of active and total ghrelin, GLP-1 and PYY following restrictive bariatric surgery and their impact on satiety: comparison of sleeve gastrectomy and adjustable gastric banding5 Prioritization and willingness to pay for bariatric surgery: the patient perspective6 Ventral hernia at the time of laparoscopic gastric bypass surgery: Should it be repaired?7 Linear stapled gastrojejunostomy with transverse handsewn enterotomy closure significantly reduces strictures for laparoscopic Roux-en-Y bypass8 Laparoscopic biliopancreatic diversion with duodenal switch as second stage for super super morbidly obese patients. Do all patients benefit?9 Sleeve gastrectomy in the super super morbidly obese (BMI > 60 kg/m2): a Canadian experience10 Laparoscopic gastric bypass for the treatment of refractory idiopathic gastroparesis: a report of 2 cases11 Duodeno-ileal switch as a primary bariatric and metabolic surgical option for the severely obese patient with comorbidities: review of a single-institution case series of duodeno-ileal intestinal bypass12 Management of large paraesophageal hernias in morbidly obese patients with laparoscopic sleeve gastrectomy: a case series13 Early results of the Ontario bariatric surgical program: using the bariatric registry14 Improving access to bariatric surgical care: Is universal health care the answer?15 Early and liberal postoperative exploration can reduce morbidity and mortality in patients undergoing bariatric surgery16 Withdrawn17 Identification and assessment of technical errors in laparoscopic Roux-en-Y gastric bypass18 A valid and reliable tool for assessment of surgical skill in laparoscopic Roux-en-Y gastric bypass19 Psychiatric predictors of presurgery drop-out following suitability assessment for bariatric surgery20 Predictors of outcomes following Roux-en-Y gastric bypass surgery at The Ottawa Hospital21 Prophylactic management of cholelithiasis in bariatric patients: Is routine cholecystectomy warranted?22 Early outcomes of Roux-en-Y gastric bypass in a publicly funded obesity program23 Similar incidence of gastrojejunal anastomotic stricture formation with hand-sewn and 21 mm circular stapler techniques during Roux-en-Y gastric bypass24 (CAGS Basic Science Award) Exogenous glucagon-like peptide-1 improves clinical, morphological and histological outcomes of intestinal adaptation in a distal-intestinal resection piglet model of short bowel syndrome25 (CAGS Clinical Research Award) Development and validation of a comprehensive curriculum to teach an advanced minimally invasive procedure: a randomized controlled trial26 Negative-pressure wound therapy (iVAC) on closed, high-risk incisions following abdominal wall reconstruction27 The impact of seed granting on research in the University of British Columbia Department of Surgery28 Quality of surgical care is inadequate for elderly patients29 Recurrence of inguinal hernia in general and hernia specialty hospitals in Ontario, Canada30 Oncostatin M receptor deficiency results in increased mortality in an intestinal ischemia reperfusion model in mice31 Laparoscopic repair of large paraesophageal hernias with anterior gastropexy: a multicentre trial32 Response to preoperative medical therapy predicts success of laparoscopic splenectomy for immune thrombocytopenic purpura33 Perioperative sepsis, but not hemorrhagic shock, promotes the development of cancer metastases in a murine model34 Measuring the impact of implementing an acute care surgery service on the management of acute biliary disease35 Patient flow and efficiency in an acute care surgery service36 The relationship between treatment factors and postoperative complications after radical surgery for rectal cancer37 Risk of ventral hernia after laparoscopic colon surgery38 Urinary metabolomics as a tool for early detection of Barrett’s and esophageal cancer39 Construct validity of individual and summary performance metrics associated with a computer-based laparo-scopic simulator40 Impact of a city-wide health system reorganization on emergency department visits in hospitals in surrounding communities41 Transcatheter aortic valve implantation for the nonoperative management of aortic stenosis: a cost-effectiveness analysis42 Breast cancer: racial differences in age of onset. A potential confounder in Canadian screening recommendations43 Risk taking in surgery: in and out of the comfort zone44 A tumour board in the office: Track those cancer patients!45 Increased patient BMI is not associated with advanced colon cancer stage or grade on presentation: a retrospective chart review46 Consensus statements regarding the multidisciplinary care of limb amputation patients in disasters or humanitarian emergencies. Report of the 2011 Humanitarian Action Summit Surgical Working Group on amputations following disasters or conflict47 Learning the CanMEDS role of professional: a pilot project of supervised discussion groups addressing the hidden curriculum48 Assessing the changing scope of training in Canadian general surgery programs: expected versus actual experience49 Predicting need for surgical management for massive gastrointestinal hemorrhage50 International health care experience: using CanMEDS to evaluate learning outcomes following a surgical mission in Mampong, Ghana51 The open abdomen: risk factors for mortality and rates of closure52 How surgeons think: an exploration of mental practice in surgical preparation53 The surgery wiki: a novel method for delivery of under-graduate surgical education54 Understanding surgical residents’ postoperative practices before implementing an enhanced recovery after surgery (ERAS) guideline at the University of Toronto55 From laparoscopic transabdominal to posterior retroperitoneal adrenalectomy: a paradigm shift in operative approach56 A retrospective audit of outcomes in patients over the age of 80 undergoing acute care abdominal surgery57 Canadian general surgery residents’ perspectives on work-hour regulations58 Timing of surgical intervention and its outcomes in acute appendicitis59 Preparing surgical trainees to deal with adverse events. An outline of learning issues60 Acute care surgical service: surgeon agreement at the time of handover61 Predicting discharge of elderly patients to prehospitalization residence following emergency general surgery62 Morbidity and mortality after emergency abdominal surgery in octo- and nonagenarians63 The impact of acute abdominal illness and urgent admission to hospital on the living situation of elderly patients64 A comparison of laparoscopic versus open subtotal gastrectomy for antral gastric adenocarcinoma: a North American perspective65 Minimally invasive excision of ectopic mediastinal parathyroid adenomas66 Perioperative outcomes of laparoscopic hernia repair in a tertiary care centre: a single institution’s experience67 Evaluation of a student-run, practical and didactic curriculum for preclerkship medical students68 Joseph Lister: Father of Modern Surgery69 Comparisons of melanoma sentinel lymph node biopsy prediction nomograms in a cohort of Canadian patients70 Local experience with myocutaneous flaps after extensive pelvic surgery71 The treatment of noncirrhotic splanchnic vein thrombosis: Is anticoagulation enough?72 Implementation of an acute care surgery service does not affect wait-times for elective cancer surgeries: an institutional experience73 Use of human collagen mesh for closure of a large abdominal wall defect, after colon cancer surgery, a case report74 The role of miR-200b in pulmonary hypoplasia associated with congenital diaphragmatic hernia75 Systematic review and meta-analysis of electrocautery versus scalpel for incising epidermis and dermis76 Accuracy of sentinel lymph node biopsy for early breast cancer in the community setting in St. John’s, New-foundland: results of a retrospective review77 Acute surgical outcomes in the 80 plus population78 The liberal use of platelets transfusions in the acute phase of trauma resuscitation: a systematic review79 Implementation of an acute care surgical on call program in a Canadian community hospital80 Short-term outcomes following paraesophageal hernia repair in the elderly patient81 First experience with single incision surgery: feasibility in the pediatric population and cost evaluation82 The impact of the establishment of an acute care surgery unit on the outcomes of appendectomies and cholecystectomies83 Description and preliminary evaluation of a low-cost simulator for training and evaluation of flexible endoscopic skills84 Tumour lysis syndrome in metastatic colon cancer: a case report85 Acute care surgery service model implementation study at a single institution86 Colonic disasters approached by emergent subtotal and total colectomy: lessons learned from 120 consecutive cases87 Acellular collagen matrix stent to protect bowel anastomoses88 Lessons we learned from preoperative MRI-guided wire localization of breast lesions: the University Health Network (UHN) experience89 Interim cost comparison for the use of platinum micro-coils in the operative localization of small peripheral lung nodules90 Routine barium esophagram has minimal impact on the postoperative management of patients undergoing esophagectomy for esophageal cancer91 Iron deficiency anemia is a common presenting issue with giant paraesophageal hernia and resolves following repair92 A randomized comparison of different ventilation strategies during thoracotomy and lung resection93 The Canadian Lung Volume Reduction Surgery study: an 8-year follow-up94 A comparison of minimally invasive versus open Ivor-Lewis esophagectomy95 A new paradigm in the follow-up after curative resection for lung cancer: minimal-dose CT scan allows for early detection of asymptomatic cancer activity96 Predictors of lymph node metastasis in early esophageal adenocarcinoma: Is endoscopic resection worth the risk?97 How well can thoracic surgery residents operate? Comparing resident and program director opinions98 The impact of extremes of age on short- and long-term outcomes following surgical resection of esophageal malignancy99 Epidermal growth factor receptor targeted gold nanoparticles for the enhanced radiation treatment of non–small cell lung cancer100 Laparoscopic Heller myotomy results in excellent outcomes in all subtypes of achalasia as defined by the Chicago classification101 Neoadjuvant chemoradiation versus surgery in managing esophageal cancer102 Quality of life postesophagectomy for cancer!103 The implementation, evolution and translocation of standardized clinical pathways can improve perioperative outcomes following surgical treatment of esophageal cancer104 A tissue-mimicking phantom for applications in thoracic surgical simulation105 Sublobar resection compared with lobectomy for early stage non–small cell lung cancer: a single institution study106 Not all reviews are equal: the quality of systematic reviews and meta-analyses in thoracic surgery107 Do postoperative complications affect health-related quality of life after video-assisted thoracoscopic lobectomy for patients with lung cancer? A cohort study108 Thoracoscopic plication for palliation of dyspnea secondary to unilateral diaphragmatic paralysis: A worthwhile venture?109 Thoracic surgery experience in Canadian general surgery residency programs110 Perioperative morbidity and pathologic response rates following neoadjuvant chemotherapy and chemoradiation for locally advanced esophageal carcinoma111 An enhanced recovery pathway reduces length of stay after esophagectomy112 Predictors of dysplastic and neoplastic progression of Barrett’s esophagus113 Recurrent esophageal cancer complicated by tracheoesophageal fistula: management by means of palliative airway stenting114 Pancreaticopleural fistula-induced empyema thoracis: principles and results of surgical management115 Prognostic factors of early postoperative mortality following right extended hepatectomy116 Optimizing steatotic livers for transplantation using a cell-penetrating peptide CPP-fused heme oxygenase117 Video outlining the technical steps for a robot-assisted laparoscopic pancreaticoduodenectomy118 Establishment of a collaborative group to conduct innovative clinical trials in Canada119 Hepatic resection for metastatic malignant melanoma: a systematic review and meta-analysis120 Acellular normothermic ex vivo liver perfusion for donor liver preservation121 Pancreatic cancer and predictors of survival: comparing the CA 19–9/bilirubin ratio with the McGill Brisbane Scoring System122 Staged liver resections for bilobar hepatic colorectal metastases: a single centre experience123 Economic model of observation versus immediate resection of hepatic adenomas124 Resection of colorectal liver metastasis in the elderly125 Acceptable long-term survival in patients undergoing liver resection for metastases from noncolorectal, non-neuroendocrine, nonsarcoma malignancies126 Patient and clinicopathological features and prognosis of CK19+ hepatocellular carcinomas: a case–control study127 The management of blunt hepatic trauma in the age of angioembolization: a single centre experience128 Liver resections for noncolorectal and non-neuroendocrine metastases: an evaluation of oncologic outcomes129 Developing an evidence-based clinical pathway for patients undergoing pancreaticoduodenectomy130 Hepatitis C infection and hepatocellular carcinoma in liver transplant: a 20 year experience131 The effect of medication on the risk of post-ERCP pancreatitis132 Temporal trends in the use of diagnostic imaging for patients with hepato-pancreato-biliary (HPB) conditions: How much ionizing radiation are we really using?196 A phase II study of aggressive metastasectomy for intra-and extrahepatic metastases from colorectal cancer133 Why do women choose mastectomy for breast cancer treatment? A conceptual framework for understanding surgical decision-making in early-stage breast cancer134 Synoptic operative reporting: documentation of quality of care data for rectal cancer surgery135 Learning curve analysis for cytoreductive surgery: a useful application of the cumulative sum (CUSUM) method136 Pancreatic cancer is strongly associated with a unique urinary metabolomic signature137 Concurrent neoadjuvant chemo/radiation in locally advanced breast cancer138 Impact of positron emission tomography on clinical staging of newly diagnosed rectal cancer: a specialized single centre retrospective study139 An evaluation of intraoperative Faxitron microradiography versus conventional specimen radiography for the excision of nonpalpable breast lesions140 Comparison of breast cancer treatment wait-times in the Southern Interior of British Columbia in 2006 and 2010141 Factors affecting lymph nodes harvest in colorectal carcinoma142 Laparoscopic adrenalectomy for metastases143 You have a message! Social networking as a motivator for fundamentals of laparoscopic surgery (FLS) training144 The evaluation and validation of a rapid diagnostic and support clinic for women assessment for breast cancer145 Oncoplastic breast surgery: oncologic benefits and limitations146 A qualitative study on rectal cancer patients’ preferences for location of surgical care147 The effect of surgery on local recurrence in young women with breast cancer148 Elevated IL-6 and IL-8 levels in tumour microenvironment is not associated with increased serum levels in humans with Pseudomyxoma peritonei and peritoneal mesothelioma149 Conversion from laparoscopic to open approach during gastrectomy: a population-based analysis150 A scoping review of surgical process improvement tools (SPITs) in cancer surgery151 Splenectomy during gastric cancer surgery: a population-based study152 Defining the polo-like kinase 4 (Plk4) interactome in cancer cell protrusions153 Neoadjuvant imatinib mesylate for locally advanced gastrointestinal stromal tumours154 Implementing results from ACOSOG Z0011: Practice-changing or practice-affirming?155 Should lymph node retrieval be a surgical quality indicator in colon cancer?156 Long-term outcomes following resection of retroperitoneal recurrence of colorectal cancer157 Clinical research in surgical oncology: an analysis of clinicaltrials.gov158 Radiation therapy after breast conserving surgery: When are we missing the mark?159 The accuracy of endorectal ultrasound in staging rectal lesions in patients undergoing transanal endoscopic microsurgery160 Quality improvement in gastrointestinal cancer surgery: expert panel recommendations for priority research areas161 Factors influencing the quality of local management of ductal carcinoma in situ: a cohort study162 Papillary thyroid microcarcinoma: Does size matter?163 Hyperthermic isolated limb perfusion for extremity soft tissue sarcomas: systematic review of clinical efficacy and quality assessment of reported trials164 Adherence to antiestrogen therapy in seniors with breast cancer: How well are we doing?165 Parathyroid carcinoma: Challenging the surgical dogma?166 A qualitative assessment of the journey to delayed breast reconstruction195 The role of yoga therapy in breast cancer patients167 Outcomes reported in comparative studies of surgical interventions168 Enhanced recovery pathways decrease length of stay following colorectal surgery, but how quickly do patients actually recover?169 The impact of complications on bed utilization after elective colorectal resection170 Impact of trimodal prehabilitation program on functional recovery after colorectal cancer surgery: a pilot study171 Complex fistula-in-ano: Should the plug be abandoned in favour of the LIFT or BioLIFT?172 Prognostic utility of cyclooxygenase-2 expression by colon and rectal cancer173 Laparoscopic right hemicolectomy with complete mesocolic excision provides acceptable perioperative outcomes but is complex and time-consuming: analysis of learning curves for a novice minimally invasive surgeon174 Intraoperative quality assessment following double stapled circular colorectal anastomosis175 Improving patient outcomes through quality assessment of rectal cancer care176 Are physicians willing to accept a decrease in treatment effectiveness for improved functional outcomes for low rectal cancer?177 Turnbull-Cutait delayed coloanal anastomosis for the treatment of distal rectal cancer: a prospective cohort study178 Preoperative high-dose rate brachytherapy in preparation for sphincter preservation surgery for patients with advanced cancer of the lower rectum179 Impact of an enhanced recovery program on short-term outcomes after scheduled laparoscopic colon resection180 The clinical results of the Turnbull-Cutait delayed coloanal anastomosis: a systematic review181 Is a vertical rectus abdominus flap (VRAM) necessary? An analysis of perineal wound complications182 Fistula plug versus endorectal anal advancement flap for the treatment of high transsphincteric cryptoglandular anal fistulas: a systematic review and meta-analysis183 Maternal and neonatal outcomes following colorectal cancer surgery184 Transanal drainage to treat anastomotic leaks after low anterior resection for rectal cancer: a valuable option185 Trends in colon cancer in Ontario: 2002–2009186 Validation of electronically derived short-term outcomes in colorectal surgery187 A population-based assessment of transanal and endoscopic resection for adenocarcinoma of the rectum188 Laparoscopic colorectal surgery in the emergency setting: trends in the province of Ontario from 2002 to 2009189 Prevention of perineal hernia after laparoscopic and robotic abdominoperineal resection: review with case series of internal hernia through pelvic mesh which was placed in attempt to prevent perineal hernia190 Effect of rectal cancer treatments on quality of life191 The use of antibacterial sutures as an adjunctive preventative strategy for surgical site infection in Canada: an economic analysis192 Impact of socioeconomic status on colorectal cancer screening and stage at presentation: preliminary results of a population-based study from an urban Canadian centre193 Initial perioperative results of the first transanal endoscopic microsurgery (TEM) program in the province of Quebec194 Use of negative pressure wound therapy decreases perineal wound infections following abdominal perineal resection. Can J Surg 2012; 55:S63-S135. [DOI: 10.1503/cjs.016712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
|
19
|
Govindarajan V, Udaykumar HS, Chandran KB. FLOW DYNAMIC COMPARISON BETWEEN RECESSED HINGE AND OPEN PIVOT BI-LEAFLET HEART VALVE DESIGNS. J MECH MED BIOL 2011; 9:161-176. [PMID: 19865586 DOI: 10.1142/s0219519409002912] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The flow dynamics through the peripheral and hinge regions of a bi-leaflet mechanical heart valve are complex and result in abnormally high shear stresses particularly during the closing phase of the valve function. It has been observed that, the late stages of closure is more significant in the dynamics of platelet activation; therefore, the later stages of closure is simulated by solving the two-dimensional Navier-Stokes equations using an Eulerian Levelset based sharp interface Cartesian grid method. Using a fixed Cartesian mesh incorporating local mesh refinement for solution accuracy and efficiency, the flow through and within a recessed hinge design and an open pivot hinge design is compared. Platelets are modelled as point particles by Lagrangian particle tracking algorithm with one way coupling. A dilute particle flow is assumed and particle-particle interactions are neglected. It was observed that the hinge region of the open pivot valve indicated a lower potential for activation of platelets compared to that in valves with a recessed hinge design.
Collapse
Affiliation(s)
- V Govindarajan
- Department of Biomedical Engineering, The University of Iowa, Iowa City, IA-52242
| | | | | |
Collapse
|
20
|
|
21
|
Govindarajan V, Trimble C. The CEO's role in business model reinvention. Harv Bus Rev 2011; 89:108-180. [PMID: 21370808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Fending off new competitors is a perennial struggle for established companies. Govindarajan and Trimble, of Dartmouth's Tuck School of Business, explain why: Many corporations become too comfortable with their existing business models and neglect the necessary work of radically reinventing them. The authors map out an alternative in their "three boxes" framework. They argue that while a CEO manages the present (box 1), he or she must also selectively forget the past (box 2) in order to create the future (box 3). Infosys chairman N.R. Narayana Murthy mastered the three boxes to reinvigorate his company and greatly increased its changes of enduring for generations.
Collapse
Affiliation(s)
- Vijay Govindarajan
- Center for Global Leadership, Tuck School of Business at Dartmouth, USA.
| | | |
Collapse
|
22
|
Thomas P, Govindarajan V, Loggie BW. Inflammatory responses in pseudomyxoma peritonei and peritoneal mesotheliomas. J Clin Oncol 2010. [DOI: 10.1200/jco.2010.28.15_suppl.e14126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
|
23
|
Govindarajan V, Udaykumar HS, Herbertson LH, Deutsch S, Manning KB, Chandran KB. Two-dimensional FSI simulation of closing dynamics of a tilting disc mechanical heart valve. J Med Device 2010; 4:11001. [PMID: 20209095 DOI: 10.1115/1.4000876] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The fluid dynamics during valve closure resulting in high shear flows and large residence times of particles has been implicated in platelet activation and thrombus formation in mechanical heart valves. Our previous studies with bi-leaflet valves have shown that large shear stresses induced in the gap between the leaflet edge and the valve housing results in relatively high platelet activation levels whereas flow between the leaflets results in shed vortices not conducive to platelet damage. In this study we compare the result of closing dynamics of a tilting disc valve with that of a bi-leaflet valve. The two-dimensional fluid-structure interaction analysis of a tilting disc valve closure mechanics is performed with a fixed grid Cartesian mesh flow solver with local mesh refinement, and a Lagrangian particle dynamic analysis for computation of potential for platelet activation. Throughout the simulation the flow remains in the laminar regime and the flow through the gap width is marked by the development of a shear layer which separates from the leaflet downstream of the valve. Zones of re-circulation are observed in the gap between the leaflet edge and the valve housing on the major orifice region of the tilting disc valve and are seen to be migrating towards the minor orifice region. Jet flow is observed at the minor orifice region and a vortex is formed which sheds in the direction of fluid motion as observed in experiments using PIV measurements. The activation parameter computed for the tilting disc valve, at the time of closure was found to be 2.7 times greater than that of the bi-leaflet mechanical valve and was found to be in the vicinity of the minor orifice region mainly due to the migration of vortical structures from the major to the minor orifice region during the leaflet rebound of the closing phase.
Collapse
Affiliation(s)
- V Govindarajan
- Department of Biomedical Engineering, University of Iowa, Iowa City, IA-52242 USA
| | | | | | | | | | | |
Collapse
|
24
|
Govindarajan V, Udaykumar H, Herbertson LH, Deutsch S, Manning KB, Chandran K. Impact of design parameters on bileaflet mechanical heart valve flow dynamics. J Heart Valve Dis 2009; 18:535-545. [PMID: 20099695 PMCID: PMC2863996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
BACKGROUND AND AIM OF THE STUDY One significant problem encountered during surgery to implant mechanical heart valve prostheses is the propensity for thrombus formation near the valve leaflet and housing. This may be caused by the high shear stresses present in the leakage jet flows through small gaps between leaflets and the valve housing during the valve closure phase. METHODS A two-dimensional (2D) study was undertaken to demonstrate that design changes in bileaflet mechanical valves result in notable changes in the flow-induced stresses and prediction of platelet activation. A Cartesian grid technique was used for the 2D simulation of blood flow through two models of bileaflet mechanical valves, and their flow patterns, closure characteristics and platelet activation potential were compared. A local mesh refinement algorithm allowed efficient and fast flow computations with mesh adaptation based on the gradients of the flow field in the gap between the leaflet and housing at the instant of valve closure. Leaflet motion was calculated dynamically, based on the fluid forces acting on it. Platelets were modeled and tracked as point particles by a Lagrangian particle tracking method which incorporated the hemodynamic forces on the particles. RESULTS A comparison of results showed that the velocity, wall shear stress and simulated platelet activation parameter were lower in the valve model, with a smaller angle of leaflet traverse between the fully open to the fully closed position. The parameters were also affected to a lesser extent by local changes in the leaflet and housing geometry. CONCLUSION Computational simulations can be used to examine local design changes to help minimize the fluid-induced stresses that may play a key role in thrombus initiation with the implanted mechanical valves.
Collapse
Affiliation(s)
- V. Govindarajan
- Department of Biomedical Engineering, University of Iowa, Iowa City, IA-52242 USA
| | - H.S. Udaykumar
- Department of Mechanical and Industrial Engineering, University of Iowa, Iowa City, IA-52242 USA
| | - L. H. Herbertson
- Department of Bioengineering, Pennsylvania State University, University Park, PA 16802
| | - S. Deutsch
- Department of Bioengineering, Pennsylvania State University, University Park, PA 16802
| | - K. B. Manning
- Department of Bioengineering, Pennsylvania State University, University Park, PA 16802
| | - K.B. Chandran
- Department of Biomedical Engineering, University of Iowa, Iowa City, IA-52242 USA
- Department of Mechanical and Industrial Engineering, University of Iowa, Iowa City, IA-52242 USA
| |
Collapse
|
25
|
Foster JM, Uppala R, Govindarajan V, Carreau JH, Stan L, Nath S, Poonam S, Galatica Z, Loggie BW. Predictive value of novel and existing activating EGFR mutations for improved survival in malignant peritoneal mesothelioma (MPM) and response to EGFR-TK inhibitors (EGFR-TKI). J Clin Oncol 2009. [DOI: 10.1200/jco.2009.27.15_suppl.11030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
11030 Background: MPMs are highly aggressive tumors with most patients diagnosed surviving 8–12 months. Currently there is a paucity of information about the molecular/biological perturbations involved in tumor formation. Previously we presented (at ASCO 2007) that novel EGFR-TK mutations occurred in these tumors predictive of optimal surgical cytoreduction; but the EGFR activity of these mutations was being investigated. Here we present the EGFR activity of these mutations as well as matured outcome data. Methods: Twenty-nine MPM patients were evaluated at a single tertiary center and tumors were probed for mutations in the TK domain of EGF receptor (mut+). All specimens were examined for somatic mutations by PCR amplification and confirmed by multiple independent PCRs. Twenty-five patients were treated with cytoreductive surgery (CRS) ± IPHC and clinical data including age, sex, cytoreductive score, histology, mutation, and survival was available for comparison of the mut+ and mut- groups. A COS-7 cell expression model was used to determine the time dependent activating profile of these mutations, as well as response to EGFR-TKI-inhibitor. Results: Mutations were found in 31% (9/29) of the tumors; 7 of these mutations were novel. All 7 novel mutations and L858R mutation identified were activating mutations with similar activation profiles. All mutations were responsive to EGFR-TKI treatment. Of the 25 patients managed surgically there were 7 mut+ and 18 mut-. Two of 7 (29%) mut+ have progressed and died of disease with a MFT of 22 months; while 13/18 (72%) mut- had progressive disease and 10/18 (56%) died with median TTP and survival of 12 months and14 months respectively. Estimated 3-year PFS was 70% mut+ and 25% mut- on log rank analysis p=0.099. Conclusions: This is the first report that MPM-EGFR mutations are activating mutations and responsive to EGFR-TKI-therapy. The mut+ subset has a “relative” improved outcome compared to wild type, but still developed progressive disease. TKIs may be a promising therapy in mut+ MPMs patients. Further elucidation of other molecular and pathway perturbations in this disease is necessary, as well as, validation of these results in a larger cohort. No significant financial relationships to disclose.
Collapse
Affiliation(s)
- J. M. Foster
- Creighton University Medical Center, Omaha, NE; University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - R. Uppala
- Creighton University Medical Center, Omaha, NE; University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - V. Govindarajan
- Creighton University Medical Center, Omaha, NE; University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - J. H. Carreau
- Creighton University Medical Center, Omaha, NE; University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - L. Stan
- Creighton University Medical Center, Omaha, NE; University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - S. Nath
- Creighton University Medical Center, Omaha, NE; University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - S. Poonam
- Creighton University Medical Center, Omaha, NE; University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Z. Galatica
- Creighton University Medical Center, Omaha, NE; University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - B. W. Loggie
- Creighton University Medical Center, Omaha, NE; University of Oklahoma Health Sciences Center, Oklahoma City, OK
| |
Collapse
|
26
|
Govindarajan V, Udaykumar HS, Chandran KB. Two-dimensional simulation of flow and platelet dynamics in the hinge region of a mechanical heart valve. J Biomech Eng 2009; 131:031002. [PMID: 19154061 DOI: 10.1115/1.3005158] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The hinge region of a mechanical bileaflet valve is implicated in blood damage and initiation of thrombus formation. Detailed fluid dynamic analysis in the complex geometry of the hinge region during the closing phase of the bileaflet valve is the focus of this study to understand the effect of fluid-induced stresses on the activation of platelets. A fixed-grid Cartesian mesh flow solver is used to simulate the blood flow through a two-dimensional geometry of the hinge region of a bileaflet mechanical valve. Use of local mesh refinement algorithm provides mesh adaptation based on the gradients of flow in the constricted geometry of the hinge. Leaflet motion is specified from the fluid-structure interaction analysis of the leaflet dynamics during the closing phase from a previous study, which focused on the fluid mechanics at the gap between the leaflet edges and the valve housing. A Lagrangian particle tracking method is used to model and track the platelets and to compute the magnitude of the shear stress on the platelets as they pass through the hinge region. Results show that there is a boundary layer separation in the gaps between the leaflet ear and the constricted hinge geometry. Separated shear layers roll up into vortical structures that lead to high residence times combined with exposure to high-shear stresses for particles in the hinge region. Particles are preferentially entrained into this recirculation zone, presenting the possibility of platelet activation, aggregation, and initiation of thrombi.
Collapse
Affiliation(s)
- V Govindarajan
- Department of Biomedical Engineering, College of Engineering, The University of lowa, 1402 SC, lowa City, IA 52242, USA
| | | | | |
Collapse
|
27
|
Govindarajan V, Trimble C. Building breakthrough businesses within established organizations. Harv Bus Rev 2005; 83:58-68, 152. [PMID: 15929404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Many companies assume that once they've launched a major innovation, growth will soon follow. It's not that simple. High-potential new businesses within established companies face stiff headwinds well after their inception. That's why a company's emphasis must shift: from ideas to execution and from leadership excellence to organizational excellence. The authors spent five years chronicling new businesses at the New York Times Company, Analog Devices, Corning, Hasbro, and other organizations. They found that a breakthrough new business (referred to as NewCo) rarely coexists gracefully with the established business in the company (called CoreCo). The unnatural combination creates three specific challenges--forgetting, borrowing, and learning--that NewCo must meet in order to survive and grow. NewCo must first forget some of what made CoreCo successful. NewCo and CoreCo have elemental differences, so NewCo must leave behind CoreCo's notions about what skills and competencies are most valuable. NewCo must also borrow some of CoreCo's assets--usually in one or two key areas that will give NewCo a crucial competitive advantage. Incremental cost reductions, for example, are never a sufficient justification for borrowing. Finally, NewCo must be prepared to learn some things from scratch. Because strategic experiments are highly uncertain endeavors, NewCo will face several critical unknowns. The more rapidly it can resolve those unknowns--that is, the faster it can learn--the sooner it will zero in on a winning business model or exit a hopeless situation. Managers can accelerate this learning by planning more simply and more often and by comparing predicted and actual trends.
Collapse
Affiliation(s)
- Vijay Govindarajan
- Dartmouth College, Tuck School of Business, Hanover, New Hampshire, USA.
| | | |
Collapse
|
28
|
|
29
|
Govindarajan V, Agarwal V, Aggarwal A, Misra R. Arthritis in sarcoidosis. J Assoc Physicians India 2001; 49:1145-7. [PMID: 11996432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
AIMS AND METHODS Sarcoidosis is systemic granulomatous disorder. Articular manifestations have received little attention in the literature. Case records of patients with sarcoidosis, presenting with articular symptoms between 1990-1999, were retrospectively analysed. RESULTS Twenty nine patients, 15 males and 14 females, median age 44 years (range 15-67 years) and median duration of articular symptoms of eight months diagnosed clinically (n=9) and on biopsy (n=20) were studied. Twenty five patients had arthritis as the presenting manifestation. Fifteen patients had chronic arthritis (> six months). Lofgren's syndrome was seen in 7% of the patients. Acute arthritis was episodic (n=4), more common in males (M:F = 9:5), predominantly affected lower limb joints and mimicked reactive arthritis. Chronic arthritis was more frequently observed in females (M:F = 1:2) and presented with involvement of bilateral symmetric hand joints, mimicking rheumatoid arthritis. Extra-articular manifestations like neuropathy and constitutional symptoms were observed in acute arthritis. Skin plaque, splenomegaly and interstitial lung disease were seen with chronic arthritis. At a median follow up of 12 months, 10/14 and 5/15 achieved complete remission whereas 2/14 and 9/15 achieved partial remission of the articular symptoms in the acute and chronic groups, respectively. CONCLUSION Arthritis in sarcoidosis is an early manifestation of disease and may mimic reactive or rheumatoid arthritis. Unsatisfactory response in chronic arthritis highlights the need for immunosuppressive drugs in addition to steroids.
Collapse
Affiliation(s)
- V Govindarajan
- Department of Clinical Immunology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India
| | | | | | | |
Collapse
|
30
|
Abstract
The vertebrate lens has a distinct polarity with cuboidal epithelial cells on the anterior side and differentiated fiber cells on the posterior side. It has been proposed that the anterior-posterior polarity of the lens is imposed by factors present in the ocular media surrounding the lens (aqueous and vitreous humor). The differentiation factors have been hypothesized to be members of the fibroblast growth factor (FGF) family. Though FGFs have been shown to be sufficient for induction of lens differentiation both in vivo and in vitro, they have not been demonstrated to be necessary for endogenous initiation of fiber cell differentiation. To test this possibility, we have generated transgenic mice with ocular expression of secreted self-dimerizing versions of FGFR1 (FR1) and FGFR3 (FR3). Expression of FR3, but not FR1, leads to an expansion of proliferating epithelial cells from the anterior to the posterior side of the lens due to a delay in the initiation of fiber cell differentiation. This delay is most apparent postnatally and correlates with appropriate changes in expression of marker genes including p57(KIP2), Maf and Prox1. Phosphorylation of Erk1 and Erk2 was reduced in the lenses of FR3 mice compared with nontransgenic mice. Though differentiation was delayed in FR3 mice, the lens epithelial cells still retained their intrinsic ability to respond to FGF stimulation. Based on these results we propose that the initiation of lens fiber cell differentiation in mice requires FGF receptor signaling and that one of the lens differentiation signals in the vitreous humor is a ligand for FR3, and is therefore likely to be an FGF or FGF-like factor.
Collapse
MESH Headings
- Animals
- Body Patterning
- Cell Differentiation
- Crystallins/biosynthesis
- Cyclin-Dependent Kinase Inhibitor p57
- DNA-Binding Proteins/isolation & purification
- Embryonic Induction
- Epithelial Cells
- Fibroblast Growth Factors
- Homeodomain Proteins/isolation & purification
- Lens, Crystalline/blood supply
- Lens, Crystalline/cytology
- Lens, Crystalline/embryology
- Mice
- Mice, Transgenic
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 3
- Mitogen-Activated Protein Kinases/metabolism
- Models, Biological
- Nuclear Proteins/isolation & purification
- Phosphorylation
- Protein-Tyrosine Kinases
- Proto-Oncogene Proteins/isolation & purification
- Proto-Oncogene Proteins c-maf
- Receptor Protein-Tyrosine Kinases/metabolism
- Receptor, Fibroblast Growth Factor, Type 1
- Receptor, Fibroblast Growth Factor, Type 3
- Receptors, Fibroblast Growth Factor/metabolism
- Transgenes
- Tumor Suppressor Proteins
Collapse
Affiliation(s)
- V Govindarajan
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | | |
Collapse
|
31
|
Abstract
FGF-10, a member of the fibroblast growth factor family, is expressed in mesodermally derived cell populations during embryogenesis. During normal ocular development, FGF-10 is expressed in the perioptic mesenchyme adjacent to the Harderian and lacrimal gland primordia. In this report, we provide evidence that FGF-10 is both necessary and sufficient to initiate glandular morphogenesis. Lens-specific expression of FGF-10 was sufficient to induce ectopic ocular glands within the cornea. In addition, lacrimal and Harderian glands were not seen in FGF-10 null fetuses. Based on these results we propose that FGF-10 is an inductive signal that initiates ocular gland morphogenesis.
Collapse
Affiliation(s)
- V Govindarajan
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, 77030, USA
| | | | | | | | | |
Collapse
|
32
|
Makarenkova HP, Ito M, Govindarajan V, Faber SC, Sun L, McMahon G, Overbeek PA, Lang RA. FGF10 is an inducer and Pax6 a competence factor for lacrimal gland development. Development 2000; 127:2563-72. [PMID: 10821755 DOI: 10.1242/dev.127.12.2563] [Citation(s) in RCA: 139] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We investigated the mechanism of tissue induction and specification using the lacrimal gland as a model system. This structure begins its morphogenesis as a bud-like outgrowth of the conjunctival epithelium and ultimately forms a branched structure with secretory function. Using a reporter transgene as a specific marker for gland epithelium, we show that the transcription factor Pax6 is required for normal development of the gland and is probably an important competence factor. In investigating the cell-cell signaling required, we show that fibroblast growth factor (FGF) 10 is sufficient to stimulate ectopic lacrimal bud formation in ocular explants. Expression of FGF10 in the mesenchyme adjacent to the presumptive lacrimal bud and absence of lacrimal gland development in FGF10-null mice strongly suggest that it is an endogenous inducer. This was supported by the observation that inhibition of signaling by a receptor for FGF10 (receptor 2 IIIb) suppressed development of the endogenous lacrimal bud. In explants of mesenchyme-free gland epithelium, FGF10 stimulated growth but not branching morphogenesis. This suggested that its role in induction is to stimulate proliferation and, in turn, that FGF10 combines with other factors to provide the instructive signals required for lacrimal gland development.
Collapse
Affiliation(s)
- H P Makarenkova
- Skirball Institute for Biomolecular Medicine, Developmental Genetics Program, Cell Biology and Pathology Departments, New York University Medical Center, New York, NY 10016, USA
| | | | | | | | | | | | | | | |
Collapse
|
33
|
Seid CA, Ramachandran RK, George JM, Govindarajan V, González-Rimbau MF, Flytzanis CN, Tomlinson CR. An extracellular matrix response element in the promoter of the LpS1 genes of the sea urchin Lytechinus pictus. Nucleic Acids Res 1997; 25:3175-82. [PMID: 9224621 PMCID: PMC146864 DOI: 10.1093/nar/25.15.3175] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The extracellular matrix (ECM) has been shown to play an important role in development and tissue-specific gene expression, yet the mechanism by which genes receive signals from the ECM is poorly understood. The aboral ectoderm-specific LpS1-alpha and -beta genes of Lytechinus pictus , members of the Spec gene family, provide an excellent model system to study ECM- mediated gene regulation. Disruption of the ECM by preventing collagen deposition using the lathrytic agent beta-aminopropionitrile (BAPN) inhibits LpS1 gene transcription. LpS1 transcription resumes after removal of BAPN and subsequent collagen reformation. Using a chloramphenicol acetyltransferase (CAT) reporter gene assay, we show that a 125 bp region of the LpS1-beta promoter from -108 to +17 contains an ECM response element (ECM RE). Insertion of the 125 bp region into the promoter of the metallothionein gene of L. pictus, a gene unaffected by ECM disruption, caused the fused promoter to become ECM dependent. As with the endogenous LpS1 genes, CAT activity directed by the fused LpS1-beta promoter resumed in embryos recovered from ECM disruption. A mutation in a cis -acting element called the proximal G-string, which lies in the 125 bp region, caused CAT activity levels in ECM-disrupted embryos to equal that of the wild-type LpS1-bet apromoter in ECM-intact embryos. These results suggest that the intact ECM normally transmits signals to inhibit repressor activity at the proximal G-string in aboral ectoderm cells. Consistent with these results were our findings which showed that in addition to expression in the aboral ectoderm, the proximal G-string mutation caused expression of the CAT gene in oral ectoderm cells. These studies suggested that the proximal G-string serves as a binding site for negative regulation of the LpS1 genes in oral ectoderm during development. We also examined trans -acting factors binding the proximal G-string following ECM disruption. Band shift gels revealed a predominant set of slower migrating nuclear proteins from ECM-disrupted embryos which bound the proximal G-string. This work suggested that ECM disruption initiates signaling that induces a repressor to bind the ECM RE and/or modifies ECM RE binding proteins, which in turn represses LpS1 gene activity.
Collapse
Affiliation(s)
- C A Seid
- Department of Biology, University of Houston, Houston, TX 77204-5513, USA
| | | | | | | | | | | | | |
Collapse
|
34
|
Ramachandran RK, Wikramanayake AH, Uzman JA, Govindarajan V, Tomlinson CR. Disruption of gastrulation and oral-aboral ectoderm differentiation in the Lytechinus pictus embryo by a dominant/negative PDGF receptor. Development 1997; 124:2355-64. [PMID: 9199362 DOI: 10.1242/dev.124.12.2355] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Little is known about the cell signaling involved in forming the body plan of the sea urchin embryo. Previous work suggested that PDGF-like and EGF-like receptor-mediated signaling pathways are involved in gastrulation and spiculogenesis in the Lytechinus pictus embryo. Here we show that expression of the human PDGF receptor-beta lacking the cytoplasmic domain disrupted development in a manner consistent with a dominant/negative mechanism. The truncated PDGF receptor-beta inhibited gut and spicule formation and differentiation along the oral-aboral axis. The most severely affected embryos arrested at a developmental stage resembling mesenchyme blastula. Coinjection into eggs of RNA encoding the entire human PDGF receptor-beta rescued development. The truncated PDGF receptor-beta caused the aboral ectoderm-specific genes LpS1 and LpC2 to be repressed while an oral ectoderm-specific gene, Ecto-V, was expressed in all ectoderm cells. The results support the hypothesis that a PDGF-like signaling pathway plays a key role in the intercellular communication required for gastrulation and spiculogenesis, and in cell commitment and differentiation along the oral-aboral axis.
Collapse
Affiliation(s)
- R K Ramachandran
- Department of Biology, The University of Houston, TX 77204-5513, USA
| | | | | | | | | |
Collapse
|
35
|
Seid CA, George JM, Sater AK, Kozlowski MT, Lee H, Govindarajan V, Ramachandran RK, Tomlinson CR. USF in the Lytechinus sea urchin embryo may act as a transcriptional repressor in non-aboral ectoderm cells for the cell lineage-specific expression of the LpS1 genes. J Mol Biol 1996; 264:7-19. [PMID: 8950263 DOI: 10.1006/jmbi.1996.0619] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Expression of the aboral ectoderm-specific LpS1 gene in Lytechinus was used to study lineage-specific transcriptional regulation during sea urchin development. Band shift assays using anti-USF antibody showed that a USF-like protein bound the USF core sequence 5'-CACGTG-3' in the promoter of the LpS1 gene. DNA constructs consisting of a wild-type LpS1 promoter and the same LpS1 promoter with a mutated USF binding site fused to the bacterial chloramphenicol acetyltransferase reporter gene were tested. The mutation in the USF binding site caused an increase in chloramphenicol acetyltransferse activity. We selected a clone that encodes USF, LvUSF, from a gastrula-stage cDNA library representing Lytechinus variegatus. Transactivation experiments, in which LvUSF RNA or a DNA construct consisting of the LvUSF cDNA clone fused to the Lytechinus pictus metallothionein promoter coinjected with the wild-type or mutated LpS1 promoter-chloramphenicol acetyltransferase gene construct, showed that chloramphenicol acetyltransferase activity from the wild-type construct was repressed, while the construct mutated at the USF binding site was active. The same wild-type and mutated LpS1 promoter DNA fragments ligated to the green fluorescent protein reporter gene were used to examine spatial expression. The reporter gene constructs containing the mutated USF binding site were expressed inappropriately in all cell types including the gut and oral ectoderm in gastrula and larva stage embryos, while the wild-type constructs were expressed primarily in the aboral ectoderm. USF was expressed in all cells of the early embryo and in all tissues except the aboral ectoderm in later embryos. The data are consistent with a model depicting Lytechinus USF, as a temporal and spatial regulator by repressing LpS1 gene transcription in non-aboral ectoderm cells.
Collapse
Affiliation(s)
- C A Seid
- Department of Biology, University of Houston, TX 77204-5513, USA
| | | | | | | | | | | | | | | |
Collapse
|
36
|
Govindarajan V, Ramachandran RK, George JM, Shakes DC, Tomlinson CR. An ECM-bound, PDGF-like growth factor and a TGF-alpha-like growth factor are required for gastrulation and spiculogenesis in the Lytechinus embryo. Dev Biol 1995; 172:541-51. [PMID: 8612970 DOI: 10.1006/dbio.1995.8059] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Growth factors and the extracellular matrix have been shown to fulfill vital developmental roles in many embryonic systems. Our hypothesis is that a developmental role played by the extracellular matrix in sea urchins may be the binding of a PDGF-like growth factor to promote signaling activity. We report here that anti-human PDGF-B antibodies and anti-human TGF-alpha antibodies immunoprecipitated specific proteins isolated from Lytechinus embryos. Addition of these antibodies to Lytechinus embryos inhibited gastrulation and spiculogenesis. The embryos are sensitive to the antibodies from the four-cell through the hatching blastula stages, which suggests that the TGF-alpha-like and PDGF-like ligands are required for the early differentiation of the gut and spicules. We present evidence that the PDGF-like growth factor depends on the extracellular matrix for signaling activity. Synthetic peptides representing the heparan sulfate proteoglycan binding sequence on human PDGF-B were added to Lytechinus embryo cultures to compete for binding sites with the endogenous PDGF-like growth factor. The experimental peptide inhibited gastrulation and caused radially arranged multiple spicules to form. Development was unaffected by a control peptide. These studies support our hypothesis and suggest that TGF-alpha-like and PDGF-like growth factors induce signaling events required for sea urchin gastrulation and spiculogenesis and suggest that an extracellular matrix-associated PDGF-like growth factor is involved in differentiation along the oral-aboral axis.
Collapse
Affiliation(s)
- V Govindarajan
- Department of Biology, University of Houston, Texas 77204-5513, USA
| | | | | | | | | |
Collapse
|
37
|
Ramachandran RK, Govindarajan V, Seid CA, Patil S, Tomlinson CR. Role for platelet-derived growth factor-like and epidermal growth factor-like signaling pathways in gastrulation and spiculogenesis in the Lytechinus sea urchin embryo. Dev Dyn 1995; 204:77-88. [PMID: 8563028 DOI: 10.1002/aja.1002040110] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The mechanisms underlying sea urchin gastrulation and spiculogenesis have been sought for decades. We have identified two growth factor signaling pathways that are involved in these developmental events. Antibodies against mammalian platelet-derived growth factor (PDGF) receptor-beta inhibited gastrulation and spiculogenesis, and antibodies against human epidermal growth factor (EGF) receptor disrupted gastrulation and spicule placement in Lytechinus pictus and L. variegatus embryos. Our studies suggested that the antibodies affect development by inhibiting rather than activating the signaling pathways. Polyclonal and monoclonal antibodies against the mammalian receptors recognized specifically Lytechinus proteins of the expected size of 170-180 x 10(3) M(r). Growth factor binding assays indicated that there are approximately 1.25 x 10(4) platelet-derived growth factor-like receptors per cell at the mesenchyme blastula stage of L. pictus, and human platelet-derived growth factor bound with an apparent affinity of KD = 4.4 nM to dissociated cells at the mesenchyme blastula stage. Immunolabelling experiments showed that at the gastrula stage, the Lytechinus platelet-derived growth factor-like receptors are located on the primary mesenchyme cells, the gut, and most prominently on the secondary mesenchyme cells and the stomodeum. The epidermal growth factor-like receptors stained less intensely on the gut and primary and secondary mesenchyme cells. Both receptors are expressed on the ciliary band and the gut of the pluteus larva but only the PDGF-like receptor is expressed on the primary mesenchyme cells. Pulse studies showed that the embryos are sensitive to the platelet-derived growth factor receptor-beta and epidermal growth factor receptor antibodies from the blastula to sometime between the mesenchyme blastula and midgastrula stages. We show that antibodies enter the blastocoel as late as the gastrula stage. Our results suggest that platelet-derived growth factor-like and epidermal growth factor-like signaling pathways are involved in the early differentiation and morphogenesis of the sea urchin gut and spicules.
Collapse
Affiliation(s)
- R K Ramachandran
- Department of Biology, University of Houston, Texas 77204-5513, USA
| | | | | | | | | |
Collapse
|
38
|
Govindarajan V. IMPACT OF PARTICIPATION IN THE BUDGETARY PROCESS ON MANAGERIAL ATTITUDES AND PERFORMANCE: UNIVERSALISTIC AND CONTINGENCY PERSPECTIVES. Decision Sciences 1986. [DOI: 10.1111/j.1540-5915.1986.tb00240.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
39
|
|
40
|
|