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Le TB, Moghaddam MG, Woodson BT, Garcia GJM. Airflow limitation in a collapsible model of the human pharynx: physical mechanisms studied with fluid-structure interaction simulations and experiments. Physiol Rep 2019; 7:e14099. [PMID: 31116516 PMCID: PMC6530458 DOI: 10.14814/phy2.14099] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 04/30/2019] [Indexed: 12/15/2022] Open
Abstract
The classical Starling Resistor model has been the paradigm of airway collapse in obstructive sleep apnea (OSA) for the last 30 years. Its theoretical framework is grounded on the wave-speed flow limitation (WSFL) theory. Recent observations of negative effort dependence in OSA patients violate the predictions of the WSFL theory. Fluid-structure interaction (FSI) simulations are emerging as a technique to quantify how the biomechanical properties of the upper airway determine the shape of the pressure-flow curve. This study aimed to test two predictions of the WSFL theory, namely (1) the pressure profile upstream from the choke point becomes independent of downstream pressure during flow limitation and (2) the maximum flowrate in a collapsible tube is V I max = A 3 / 2 ( ρ d A / d P ) - 1 / 2 , where ρ is air density and A and P are the cross-sectional area and pressure at the choke point respectively. FSI simulations were performed in a model of the human upper airway with a collapsible pharynx whose wall thickness varied from 2 to 8 mm and modulus of elasticity ranged from 2 to 30 kPa. Experimental measurements in an airway replica with a silicone pharynx validated the numerical methods. Good agreement was found between our FSI simulations and the WSFL theory. Other key findings include: (1) the pressure-flow curve is independent of breathing effort (downstream pressure vs. time profile); (2) the shape of the pressure-flow curve reflects the airway biomechanical properties, so that V I max is a surrogate measure of pharyngeal compliance.
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Affiliation(s)
- Trung B. Le
- Department of Biomedical EngineeringMarquette University & The Medical College of WisconsinMilwaukeeWisconsin
- Present address:
Department of Civil and Environmental EngineeringNorth Dakota State UniversityFargoNorth Dakota
| | - Masoud G. Moghaddam
- Department of Biomedical EngineeringMarquette University & The Medical College of WisconsinMilwaukeeWisconsin
| | - B. Tucker Woodson
- Department of Otolaryngology and Communication SciencesMedical College of WisconsinMilwaukeeWisconsin
| | - Guilherme J. M. Garcia
- Department of Biomedical EngineeringMarquette University & The Medical College of WisconsinMilwaukeeWisconsin
- Department of Otolaryngology and Communication SciencesMedical College of WisconsinMilwaukeeWisconsin
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Soares JS, B Le T, Sotiropoulos F, S Sacks M. Modeling the Role of Oscillator Flow and Dynamic Mechanical Conditioning on Dense Connective Tissue Formation in Mesenchymal Stem Cell-Derived Heart Valve Tissue Engineering. J Med Device 2013; 7:0409271-409272. [PMID: 24895524 DOI: 10.1115/1.4025984] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 11/05/2013] [Indexed: 11/08/2022] Open
Affiliation(s)
- João S Soares
- Institute for Computational Engineering and Sciences, University of Texas at Austin , Austin, TX 78712
| | | | - Fotis Sotiropoulos
- Saint Anthony Falls Laboratory, Department of Civil Engineering, University of Minnesota , Minneapolis, MN 55414
| | - Michael S Sacks
- Institute for Computational Engineering and Sciences, Department of Biomedical Engineering, University of Texas at Austin , Austin, TX 78712
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Abstract
High-resolution numerical simulations are carried out to systematically investigate the effect of the incoming flow waveform on the hemodynamics and wall shear stress patterns of an anatomic sidewall intracranial aneurysm model. Various wave forms are constructed by appropriately scaling a typical human waveform such that the waveform maximum and time-averaged Reynolds numbers, the Womersley number (α), and the pulsatility index (PI) are systematically varied within the human physiologic range. We show that the waveform PI is the key parameter that governs the vortex dynamics across the aneurysm neck and the flow patterns within the dome. At low PI, the flow in the dome is similar to a driven cavity flow and is characterized by a quasi-stationary shear layer that delineates the parent artery flow from the recirculating flow within the dome. At high PI, on the other hand, the flow is dominated by vortex ring formation, transport across the neck, and impingement and breakdown at the distal wall of the aneurysm dome. We further show that the spatial and temporal characteristics of the wall shear stress field on the aneurysm dome are strongly correlated with the vortex dynamics across the neck. We finally argue that the ratio between the characteristic time scale of transport by the mean flow across the neck and the time scale of vortex ring formation can be used to predict for a given sidewall aneurysm model the critical value of the waveform PI for which the hemodynamics will transition from the cavity mode to the vortex ring mode.
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Affiliation(s)
- Trung B. Le
- Department of Civil Engineering, Saint Anthony Falls Laboratory, University of Minnesota, 2 Third Avenue South East, Minneapolis, MN 55414
| | - Iman Borazjani
- Department of Civil Engineering, Saint Anthony Falls Laboratory, University of Minnesota, 2 Third Avenue South East, Minneapolis, MN 55414
| | - Fotis Sotiropoulos
- Department of Civil Engineering, Saint Anthony Falls Laboratory, University of Minnesota, 2 Third Avenue South East, Minneapolis, MN 55414
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Shum PW, Peet NP, Weintraub PM, Le TB, Zhao Z, Barbone F, Cashman B, Tsay J, Dwyer S, Loos PC, Powers EA, Kropp K, Wright PS, Bitonti A, Dumont J, Borcherding DR. The design and synthesis of purine inhibitors of CDK2. III. Nucleosides Nucleotides Nucleic Acids 2001; 20:1067-78. [PMID: 11562960 DOI: 10.1081/ncn-100002493] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Cyclin-dependent kinases (CDKs) belong to a class of enzymes that control the ability of a cell to enter into and proceed through the cell division cycle. Using purine as a scaffold, we have synthesized a number of nanomolar inhibitors of CDK-2/cyclin E. In this report, the synthesis of a series of piperidine-substituted purine analogs will be presented, as well as some of their in vitro and in vivo biological effects.
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Affiliation(s)
- P W Shum
- Aventis Pharmaceuticals Inc., Rt. 202-206, Bridgewater, New Jersey 08807, USA
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Abstract
Youth is a strong predictor of functional recovery after peripheral nerve repair, while adulthood is commonly associated with poor outcome. Identification of the factors responsible for this difference could form the basis for strategies to improve regeneration in adults. Preferential reinnervation of motor pathways by motor axons (PMR) occurs strongly in young rats, but is often absent in older animals, and thus parallels the overall trend for superior results in young individuals. These experiments evaluate the individual contributions of peripheral nerve age and motoneuron age to the decline in regeneration specificity (PMR) which accompanies the aging process. The femoral nerves of young and old Lewis rats were removed as inverted "Y" grafts from the femoral trunk proximally to the terminal muscle and cutaneous branches distally. These grafts were transferred from (1) old to young, (2) young to old, (3) old to old, and (4) young to young bilaterally in 10 individuals per group. After 8 weeks of regeneration, reinnervation of cutaneous and muscle branches was assessed by dual labeling with HRP and Fluoro-Gold. Motor neuron regeneration was random in old to old (mean muscle branch (M) = 159, mean cutaneous branch (C) = 168), but PMR was seen when young pathways were used in old animals (M = 163, C = 116). PMR was vigorous when either type of graft was used in young animals (young graft, M = 218, C = 134; old graft, M = 204, C = 127). In this model, motoneuron age appears to be the primary determinant of specificity. However, the pathway also makes significant contributions, as shown by the ability of young pathways to generate specificity in old animals. Manipulation of graft Schwann cell behavior might therefore be an appropriate strategy to improve outcome in older individuals.
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Affiliation(s)
- T B Le
- Departments of Orthopaedic Surgery and Neurology, Johns Hopkins Medical School, Baltimore, Maryland 21287, USA
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Le TB, Hentz VR. Hand and wrist injuries in young athletes. Hand Clin 2000; 16:597-607. [PMID: 11117050] [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] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Successful treatments of musculoskeletal injuries in the pediatric population demand a thorough understanding of the basic anatomy and its biomechanics, and the physiology of growth and development of the immature skeleton. In addition, good treatment outcomes rely on the treating physician being an effective teacher to the young athlete and the patient's parents, coaches, and trainers. At the same time, the physician must be a good student in learning the nature of the patient's sports and each patient's athletic ability and aspirations. Most pediatric hand and wrist injuries can be treated nonoperatively with proper immobilization techniques and activity modification, but cases requiring surgical intervention must be recognized promptly to avoid long-term complications.
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Affiliation(s)
- T B Le
- Department of Functional Restoration, Hand Surgery Division, Stanford University, Stanford, California, USA
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Abstract
Osteonecrosis is a disease that leads to joint destruction and often involves large joints, such as the hips, knees, and shoulders. Nontraumatic osteonecrosis of the adult elbow, to the best of the authors' knowledge, has not been reported. Nine adult patients with atraumatic osteonecrosis of 11 elbows were identified. The mean age at presentation was 36 years (range, 26-63 years); five patients were women and four were men. Six elbows involved the capitellum, three involved the lateral epicondyles, one involved the trochlea and radial head, and one involved medial and lateral epicondylar disease. All patients were receiving corticosteroid therapy, and no relationship between the duration or the amount of corticosteroid use and the severity of the osteonecrosis was found. Seven patients with radiographic Stage I and Stage II disease responded well to nonoperative treatments consisting of activity modification, analgesics, and a brief period of immobilization. Nonoperative treatment failed in two patients with Stage III disease, and they had core decompressions for pain relief. One patient with late Stage III disease in both elbows underwent bilateral total elbow arthroplasties. In contrast to the pediatric population, osteonecrosis of the adult elbow potentially can lead to end stage arthritis. If the osteonecrosis is diagnosed early, nonoperative treatment may be effective in relieving pain, although the long-term results of these treatments remain unknown.
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Affiliation(s)
- T B Le
- Johns Hopkins University School of Medicine, Department of Orthopaedic Surgery, Baltimore, MD, USA
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Le TB, Mizel MS, Temple HT. Reducing postsurgical pain and tissue reaction from suture-induced skin tenting. Foot Ankle Int 1998; 19:420. [PMID: 9677089 DOI: 10.1177/107110079801900615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- T B Le
- The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA
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Ha MC, Cordier S, Bard D, Le TB, Hoang AH, Hoang TQ, Le CD, Abenhaim L, Nguyen TN. Agent orange and the risk of gestational trophoblastic disease in Vietnam. Arch Environ Health 1996; 51:368-74. [PMID: 8896386 DOI: 10.1080/00039896.1996.9934424] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
There have been claims of an increased risk for gestational trophoblastic disease (i.e., hydatidiform mole and choriocarcinoma) in Vietnam since the period of Agent Orange sprayings. In 1990, we conducted a case-control study in Ho Chi Minh City to investigate risk factors for gestational trophoblastic disease in Vietnam. Eighty-seven married women, all of whom had a recent pathologic diagnosis of gestational trophoblastic disease, identified in the Obstetrical and Gynecological Hospital, were included in the study. Eighty-seven married women who were admitted mainly in the surgery departments of the same hospital were the controls, and they were matched to cases for age and area of residence. Odds ratios (ORs), adjusted for matching variables and other potential confounders, were estimated with unconditional logistic regression. A statistically significant trend in risk was observed with previous live births (p = .01). Cases were found to eat less meat per wk (OR = 0.4, 95% confidence interval [95% CI] = 0.2-0.9 for > or = five meat dishes) and to own fewer consumer goods than controls. An increase in risk was associated with the breeding of pigs (OR = 5.7, 95% CI = 1.2-27.6 for raising three or more pigs). A cumulative Agent Orange exposure index was constructed, using the patient's complete residence history. No significant difference was found between cases and controls for this index (OR = 0.7, 95% CI = 0.2-1.8 for high-exposure category), nor was such a difference noted for the agricultural use of pesticides.
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Affiliation(s)
- M C Ha
- Institut National de la Santé et de la Recherche Médicale, Villejuif, France
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Bates SE, Meadows B, Goldspiel BR, Denicoff A, Le TB, Tucker E, Steinberg SM, Elwood LJ. A pilot study of amiodarone with infusional doxorubicin or vinblastine in refractory breast cancer. Cancer Chemother Pharmacol 1995; 35:457-63. [PMID: 7882454 DOI: 10.1007/bf00686829] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [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: 01/27/2023]
Abstract
Increasing evidence suggests that P-glycoprotein (Pgp) expression can mediate drug resistance in refractory breast cancer. We studied 33 patients with refractory breast cancer enrolled in a pilot study of oral amiodarone as a Pgp antagonist given in combination with infusional doxorubicin or vinblastine. Whenever possible, tumors were biopsied and Pgp expression was assayed. Patients received either 60 mg/m2 doxorubicin over 96 h or 8.5 mg/m2 vinblastine over 120 h by continuous intravenous infusion. Beginning with the second cycle of chemotherapy, 600-800 mg amiodarone was given orally each day. Patients who experienced toxicity due to amiodarone but were responding to chemotherapy were placed on quinidine. Partial responses were observed in 9 of 33 patients on study and were sometimes observed after the first cycle of chemotherapy, before amiodarone was given, suggesting that some patients may have responded to treatment because of the infusional schedule. Toxicities were primarily the known side effects of the antineoplastic agents and of amiodarone. The major amiodarone toxicity was gastrointestinal, with nausea, vomiting, anorexia, or diarrhea being noted in 21 patients. Biopsy samples were obtained from 29 patients and in 21 cases, viable tumor tissue was present and the results were interpretable. Of the 21 samples, 9 had Pgp expression as determined by immunohistochemical staining; 12 were considered negative. The presence of Pgp expression was associated with an acceleration of the time to treatment failure. Whereas normal-tissue toxicities related to the combination of a Pgp antagonist with chemotherapy were not observed, amiodarone was associated with too many untoward effects to be utilized as a drug resistance-reversing agent.
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Affiliation(s)
- S E Bates
- National Institutes of Health, Bethesda, MD 20892
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Cordier S, Le TB, Verger P, Bard D, Le CD, Larouze B, Dazza MC, Hoang TQ, Abenhaim L. Viral infections and chemical exposures as risk factors for hepatocellular carcinoma in Vietnam. Int J Cancer 1993; 55:196-201. [PMID: 7690345 DOI: 10.1002/ijc.2910550205] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [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: 01/26/2023]
Abstract
A case-control study investigating risk factors for hepatocellular carcinoma (HCC) was conducted in Hanoi, in the north of Vietnam, between 1989 and 1992. Male cases of HCC (152) diagnosed in 2 hospitals were included. Hospital controls (241) admitted mainly to abdominal surgery departments were frequency-matched to cases for sex, age, hospital and place of residence (Hanoi, province). Odds ratios adjusted for matching variables and other potential confounders were estimated using unconditional logistic regression, or exact non-parametric statistical inference when numbers were small. Positivity for hepatitis B surface antigen (HBsAg) was the main risk factor for HCC in this sample. Five subjects (3 cases, 2 controls) had been infected by hepatitis C virus (HCV), and none of them were carriers of HBsAg, giving an OR of 38 associated with HCV infection among HBsAG-negative subjects. Alcohol drinking was associated with HCC and interacted with HBsAg positivity. Agricultural use of organophosphorous pesticides (30 liters/year or more) and military service in the south of Vietnam for 10 years or more were also associated with an increased risk of HCC. This study confirms the major role played by HBV infection and its association with HCC in south-east Asia. It also suggests how other factors such as alcohol consumption or exposure to chemicals may interact with HBV infection.
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Affiliation(s)
- S Cordier
- Institut National de la Santé et de la Recherche Médicale, INSERM U.170 Villejuif, France
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Harbeson SL, Shatzer SA, Le TB, Buck SH. A new class of high affinity ligands for the neurokinin A NK2 receptor: psi (CH2NR) reduced peptide bond analogues of neurokinin A4-10. J Med Chem 1992; 35:3949-55. [PMID: 1331450 DOI: 10.1021/jm00099a024] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [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: 12/26/2022]
Abstract
Analogues of [Leu10]NKA4-10 were synthesized in which each of the amide bonds was sequentially replaced with the reduced amide psi (CH2NH) bond to determine the effect of this structural modification on the antagonism of NKA binding to the HUB NK2 receptor. [psi (CH2-NH)9,Leu10]NKA4-10 (6) retained significant affinity for the NK2 receptor (IC50 = 115 nM) and showed weak partial stimulation of PI turnover (approximately 10-15% of NKA maximum). 6 behaves as a competitive antagonist of NKA-stimulated PI turnover with a pA2 = 6.7. The secondary amine of the psi (CH2NH) moiety of 6 was converted to a tertiary amine by alkylation. This modification was found to have a small effect upon receptor affinity but did result in attenuation of partial agonist activity. A combination of amino acid substitutions and psi (CH2NH) alkylation yielded [beta Ala8,psi (CH2N(CH2)2CH3)9,Phe10]NKA4-10 (21) which has very high affinity for the HUB NK2 receptor. This compound inhibited [125I]NKA binding with an IC50 = 1 nM which is equal to the receptor affinity of NKA. Compound 21 also shows very weak partial agonism of PI turnover (< or = 5% of NKA maximum) which makes this the most potent member of a new class of NKA ligands: psi(CH2NR)9-NKA4-10 analogues which potently antagonize NKA binding and possess minimal partial agonist activity.
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Affiliation(s)
- S L Harbeson
- Marion Merrell Dow Research Institute, Cincinnati, Ohio 45215
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