Effect of mechanical fatigue on commercial bioprosthetic TAVR valve mechanical and microstructural properties

Valvular structural deterioration is of particular concern for transcatheter aortic valve replacements due to their suspected shorter longevity and increasing use in younger patient populations. In this work we investigated the mechanical and microstructural changes in commercial TAVR valves composed of both glutaraldehyde fixed bovine and porcine pericardium (GLBP and GLPP) following accelerated wear testing (AWT) as outlined in ISO 5840 standards. This provided greater physiological relevance to the loading compared to previous studies and by utilizing digital image correlation we were able to obtain strain contours for each leaflet pre and post fatigue and identify sites of fatigue damage. The areas of greatest change in mechanical strain for each leaflet were then further probed using biaxial tensile testing, confocal microscopy, and electron microscopy. It was observed that overall strain decreased in the GLPP valves following AWT of 200 million cycles while the GLBP valve showed an increase in overall strain. Biaxial tensile testing showed a statistically significant reduction in stress for GLPP while no significant changes were seen for GLBP. Both confocal and electron microscopy showed a disruption to the gross collagen organization and fibrillar structure, including fragmentation, for GLPP but only the former for GLBP. However, further test data is required to confirm these findings and to provide a better understanding of this fatigue pathway is required such that it can be incorporated into both valve design and selection processes to improve overall longevity for both GLPP and GLBP devices.

Double faecal immunochemical testing in patients with symptoms suspicious of colorectal cancer

BACKGROUND

Faecal immunochemical test (FIT)-directed pathways based on a single test have been implemented for symptomatic patients. However, with a single test, the sensitivity is 87 per cent at 10 µg haemoglobin (Hb) per g faeces. This aims of this study were to define the diagnostic performance of a single FIT, compared with double FIT in symptomatic populations.

METHODS

Two sequential prospective patient cohorts referred with symptoms from primary care were studied. Patients in cohort 1 were sent a single FIT, and those in cohort 2 received two tests in succession before investigation. All patients were investigated, regardless of having a positive or negative test (threshold 10 µg Hb per g).

RESULTS

In cohort 1, 2260 patients completed one FIT and investigation. The sensitivity of single FIT was 84.1 (95 per cent c.i. 73.3 to 91.8) per cent for colorectal cancer and 67.4 (61.0 to 73.4) per cent for significant bowel pathology. In cohort 2, 3426 patients completed at least one FIT, and 2637 completed both FITs and investigation. The sensitivity of double FIT was 96.6 (90.4 to 99.3) per cent for colorectal cancer and 83.0 (77.4 to 87.8) per cent for significant bowel pathology. The second FIT resulted in a 50.0 per cent reduction in cancers missed by the first FIT, and 30.0 per cent for significant bowel pathology. Correlation between faecal Hb level was only modest (rs = 0.58), and 16.8 per cent of double tests were discordant, 11.4 per cent in patients with colorectal cancer and 18.3 per cent in those with significant bowel pathology.

CONCLUSION

FIT in patients with high-risk symptoms twice in succession reduces missed significant colorectal pathology and has an acceptable workload impact.

Webinar and survey on quality management principles within the Australian and New Zealand ACPSEM Workforce

Healthcare relies upon the accurate and safe delivery of patient care. This is only achievable when systems are developed to ensure high quality, robust outcomes, for instance quality management systems. The concept of quality management can take on a different meaning depending on the context in which it is found. To add complication, the amount of education required for quality management will vary depending on one's exposure to the implementation of quality systems. In part to address these issues, the Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) Queensland Branch held a quality management webinar for members and non-members across Australia and New Zealand. The purpose of the webinar was to educate and facilitate discussion regarding the application of quality management principles for the ACPSEM profession. In conjunction, a pre- and post-webinar survey was conducted to gain an insight into existing knowledge and attitudes within the professions governed by the ACPSEM and students undertaking related studies. This paper authored by the webinar speakers reintroduces the quality management principles that were discussed in webinar, exemplifies the importance of quality management skills within the ACPSEM professions and presents the results of the surveys, promoting the need for more educational resources on quality management tools.

A direct comparison of the optically stimulated luminescent properties of BeO and Al2O3 for clinical in-vivo dosimetry

Optically stimulated luminescence dosimetry is a relatively recent field of in-vivo dosimetry in clinical radiotherapy, developing over the last 20 years. As a pilot study, this paper presents a direct comparison between the sensitivity variance with use, stability of measurement and linearity of the current clinical standard Al₂O₃:C and a potential alternative, beryllium oxide. A set of ten optically stimulated luminescence dosimeters (OSLD), including five of each type, were used simultaneously and irradiated on a Versa HD linear accelerator. Having similar sensitivity, while Al₂O₃:C showed a relatively stable signal response from initial use, BeO was found to have a higher response to the same dose. However, BeO displayed a strong exponential decline from initial signal response following a model of [Formula: see text], reaching stability after approximately 10 irradiation cycles. BeO was shown to have potentially higher accuracy than Al₂O₃:C, with less variation between individual doses. Both OSLD showed good linearity between 0.2-5.0 Gy. Between these bounds, Al₂O₃:C demonstrated a strong linear response following the trend [Formula: see text], however beyond this showed deviation from linearity, resulting in a measured dose of [Formula: see text] Gy at 10.0 Gy dose delivery. BeO showed strong linearity across the full examined range of 0.2-10.0 Gy with following a model of [Formula: see text] Gy with a recorded dose at 10.0 Gy delivery as [Formula: see text] Gy. In conclusion, BeO does show large variance in sensitivity between individual OSLD and a considerable initial variance and decline in dose-response, however after pre-conditioning and individual normalisation to offset OSLD specific sensitivity BeO provides not only a viable alternative to Al₂O₃:C, but potentially provide higher accuracy, precision and reproducibility for in-vivo dosimetry.

Maternal and Child Health Pipeline Training Programs: A Description of Training Across 6 Funded Programs

Purpose

The HRSA-funded maternal and child health pipeline training programs (MCHPTPs) are a response to the critical need to diversify the MCH workforce, as a strategy to reduce health disparities in MCH populations. These MCHPTPs support students from undergraduate to graduate education and ultimately into the MCH workforce.

Description

The models and components of training across the six MCHPTPs funded in 2016–2021 are summarized, to examine the design and delivery of undergraduate pipeline training and the insights gained across programs.

Assessment

Strategies that emerged across training programs were organized into three themes: recruitment, support for student persistence (in education), and pipeline-to-workforce intentionality. Support for student persistence included financial support, mentoring, creating opportunity for students to develop a sense of belonging, and the use of research as a tool to promote learning and competitiveness for graduate education. Finally, the link to Maternal and Child Health Bureau (MCHB) long-term training and other MCHB opportunities for professional development contributed significant nuance to the pipeline-to-workforce objectives of these programs.

Conclusions

The MCHPTPs not only increase the diversity of the MCH workforce, they also actively prepare the next generation of MCH leaders. The intentional connection of undergraduates to the infrastructure and continuum of MCH training, underscores the comprehensive impact of this funding.

Evaluation of Pericardial Tissues from Assorted Species as a Tissue-Engineered Heart Valve Material

Decellularized pericardial tissue is a strong candidate for a TEHV material as ECM is present to guide cellular infiltration and fixed porcine and bovine pericardial tissue have existing use in bioprosthetic heart valves. In this work, we compare the mechanical and microstructural properties of decellularized-sterilized (DS) porcine, bovine, and bison pericardial tissues with respect to use as a TEHV. H&E staining was used to verify removal of cellular content post-decellularization and to evaluate collagen fiber structure. Additionally, uniaxial and biaxial tension testing were used to compare mechanical performance and, for the latter, acquire constitutive model parameters for subsequent finite element (FE) modeling. H&E staining revealed complete removal of cellular content and good collagen fiber structure. Tensile testing showed comparable mechanical strength between the three DS pericardial tissues and considerably stronger mechanical properties compared to native tissues. Bovine and bison DS pericardial tissues showed the strongest mechanical performance in the FE models with bison demonstrating the overall best mechanical characteristics. The increased thickness of bovine and bison tissues coupled with the strong mechanical behavior and ECM structure indicates that these materials will be resistant to damage until sufficient cellular infiltration has occurred such that damaged tissue can be repaired.

Finite element analysis in clinical patients with atherosclerosis

Endovascular plaque composition is strongly related to stent strut stress and is responsible for strut fatigue, stent failure, and possible in-stent restenosis. To evaluate the effect of plaque on artery wall resistance to expansion we performed in silico analysis of atherosclerotic vessels. We generated finite element models from in vivo intravascular ultrasound virtual histology images to determine local artery surface stiffness and determined which plaque structures have the greatest influence. We validated the predictive capacity of our modeling approach by testing an atherosclerotic peripheral artery ex vivo with pressure-inflation testing at physiological pressures ranging from 10 to 200 mmHg. For this purpose, the in silico deformation of the arterial wall was compared to that observed ex vivo. We found that calcification had a positive effect on surface stiffness with fibrous plaque and necrotic core having negative effects. Additionally, larger plaque structures demonstrated significantly higher average surface stiffness and calcification located nearer the lumen was also shown to increase surface stiffness. Therefore, more developed plaques will have greater resistance to expansion and higher stent strut stress, with calcification located near the lumen further increasing stress in localized areas. Thus, it may be expected that such plaque structures may increase the likelihood of localized stent strut fracture.

Experience of living with type 1 diabetes in a low-income country: a qualitative study from Liberia

INTRODUCTION

While epidemiological data for type 1 diabetes (T1D) in low/middle-income countries, and particularly low-income countries (LICs) including Liberia is lacking, prevalence in LICs is thought to be increasing. T1D care in LICs is often impacted by challenges in diagnosis and management. These challenges, including misdiagnosis and access to insulin, can affect T1D outcomes and frequency of severe complications. Despite the severe nature of T1D and growing burden in sub-Saharan Africa, little is currently known about the impact of T1D on patients and caregivers in the region.

METHODS

We conducted a qualitative study consisting of interviews with patients with T1D, caregivers, providers, civil society members and a policy-maker in Liberia to better understand the psychosocial and economic impact of living with T1D, knowledge of T1D and self-management, and barriers and facilitators for accessing T1D care.

RESULTS

This study found T1D to have a major psychosocial and economic impact on patients and caregivers, who reported stigma, diabetes distress and food insecurity. Patients, caregivers and providers possessed the knowledge necessary to effectively manage T1D but insufficient community awareness leads to delayed diagnosis, often in an emergency department. Most patients reported receiving free services and materials, though the cost of transportation to clinic visits and recommended foods is a barrier to disease management. Many providers noted the lack of national T1D-specific guidelines and registries. Policy-makers reported a lack of prioritisation of and resources for T1D. These barriers, combined with scarcity and expense of appropriate foods, pose severe barriers for self-management of T1D.

CONCLUSION

T1D was found to have a significant impact on patients and caregivers, and informants identified several key individual and systems-level barriers to effective T1D care in Liberia. Addressing these concerns is vital for designing sustainable and effective programmes for treating patients living with T1D.

Automatic Detection and Tracking of Marker Seeds Implanted in Prostate Cancer Patients using a Deep Learning Algorithm

Purpose:

Fiducial marker seeds are often used as a surrogate to identify and track the positioning of prostate volume in the treatment of prostate cancer. Tracking the movement of prostate seeds aids in minimizing the prescription dose spillage outside the target volume to reduce normal tissue complications. In this study, You Only Look Once (YOLO) v2™ (MathWorks™) convolutional neural network was employed to train ground truth datasets and develop a program in MATLAB that can visualize and detect the seeds on projection images obtained from kilovoltage (kV) X-ray volume imaging (XVI) panel (Elekta™).

Methods:

As a proof of concept, a wax phantom containing three gold marker seeds was imaged, and kV XVI seed images were labeled and used as ground truth to train the model. The projection images were corrected for any panel shift using flex map data. Upon successful testing, labeled marker seeds and projection images of three patients were used to train a model to detect fiducial marker seeds. A software program was developed to display the projection images in real-time and predict the seeds using YOLO v2 and determine the centers of the marker seeds on each image.

Results:

The fiducial marker seeds were successfully detected in 98% of images from all gantry angles; the variation in the position of the seed center was within ± 1 mm. The percentage difference between the ground truth and the detected seeds was within 3%.

Conclusion:

Our study shows that deep learning can be used to detect fiducial marker seeds in kV images in real time. This is an ongoing study, and work is underway to extend it to other sites for tracking moving structures with minimal effort.

Implementation outcomes of national decentralization of integrated outpatient services for severe non-communicable diseases to district hospitals in Rwanda

OBJECTIVES

Effective coverage of non-communicable disease (NCD) care in sub-Saharan Africa remains low, with the majority of services still largely restricted to central referral centres. Between 2015 and 2017, the Rwandan Ministry of Health implemented a strategy to decentralise outpatient care for severe chronic NCDs, including type 1 diabetes, heart failure and severe hypertension, to rural first-level hospitals. This study describes the facility-level implementation outcomes of this strategy.

METHODS

In 2014, the Ministry of Health trained two nurses in each of the country's 42 first-level hospitals to implement and deliver nurse-led, integrated, outpatient NCD clinics, which focused on severe NCDs. Post-intervention evaluation occurred via repeated cross-sectional surveys, informal interviews and routinely collected clinical data over two rounds of visits in 2015 and 2017. Implementation outcomes included fidelity, feasibility and penetration.

RESULTS

By 2017, all NCD clinics were staffed by at least one NCD-trained nurse. Among the approximately 27 000 nationally enrolled patients, hypertension was the most common diagnosis (70%), followed by type 2 diabetes (19%), chronic respiratory disease (5%), type 1 diabetes (4%) and heart failure (2%). With the exception of warfarin and beta-blockers, national essential medicines were available at more than 70% of facilities. Clinicians adhered to clinical protocols at approximately 70% agreement with evaluators.

CONCLUSION

The government of Rwanda was able to scale a nurse-led outpatient NCD programme to all first-level hospitals with good fidelity, feasibility and penetration as to expand access to care for severe NCDs.

Noncommunicable Disease (NCD) strategic plans in low- and lower-middle income Sub-Saharan Africa: framing and policy response

Background

Global efforts to address NCDs focus primarily on 4-by-4 interventions – interventions to prevent and treat four groups of conditions affecting mainly older adults (some cardiovascular disease and cancers, type 2 diabetes, chronic respiratory disease) and four associated risk factors (alcohol, tobacco, poor diets, and physical inactivity). However, the NCD burden in Sub-Saharan Africa (SSA) is composed of a more diverse set of conditions, driven by a more complex group of risks, and impacting all segments of the population.

Objective

To document the NCD priorities identified by NCD strategic plans, to characterize the proposed policy response, and to assess the alignment between the two.

Methods

Using a two-part conceptual framework, we undertook a descriptive study to characterize the framing and overall policy response of strategic plans from 24 low- and lower-middle-income countries across SSA.

Results

The national situation assessments that ground strategic plans emphasize a diversity of conditions that range in terms of severity and frequency. These assessments also highlight a wide diversity of factors that shape this burden. Most include discussions of a broad range of behavioral, structural, genetic, and infectious risk factors. Plans endorse a more narrow response to this diverse burden, with a focus on primary and secondary prevention that is generally convergent with the objectives established in global policy documents.

Conclusions

Broadly, we observe that plans developed by countries in SSA recognize the heterogeneity of the NCD burden in this region. However, they emphasize interventions that are consistent with global strategies focused on preventing a narrower set of cardiometabolic risk factors and their associated diseases. In comparison, relatively few countries detail plans to prevent, treat, and palliate the full scope of the needs they identify. There is a need for increased support for bottom-up planning efforts to address local priorities.

Evaluation of the role of peripheral artery plaque geometry and composition on stent performance

Peripheral stent fracture is a major precursor to restenosis of femoral artery atherosclerosis that has been treated with stent implantation. In this work, we validate a workflow for performing in silico stenting on a patient specific peripheral artery with heterogeneous plaque structure. Six human cadaveric femoral arteries were imaged ex vivo using intravascular ultrasound virtual histology (IVUS-VH) to obtain baseline vessel geometry and plaque structure. The vessels were then stented and the imaging repeated to obtain the stented vessel lumen area. Finite element (FE) models were then constructed using the IVUS-VH images, where the material property constants for each finite element were calculated using the proportions of each plaque component in the element, as identified by the IVUS-VH images. A virtual stent was deployed in each FE model, and the model lumen area was calculated and compared to the experimental lumen area to validate the modeling approach. The model was then used to compare stent performance for heterogeneous and homogeneous artery models, to determine whether plaque geometry or composition had added effects on stent performance. We found that the simulated lumen areas were similar to the corresponding experimental values, despite using generic material constants. Additionally, the heterogeneous and homogeneous lumen areas were also similar, implying that plaque geometry is a stronger predictor of stent expansion performance than plaque composition. Comparing stent stress and strain for heterogeneous and homogeneous models, it was found that stress from these two models had a strong linear correlation, while the strain correlation was weaker but still present. This implies that stent performance may be predicted with a simple homogeneous material models accounting for overall geometry of the plaque, providing that stent fatigue is calculated using stress criteria.

Ex Vivo Evaluation of IVUS-VH Imaging and the Role of Plaque Structure on Peripheral Artery Disease

Peripheral artery disease (PAD) results from the buildup of atherosclerotic plaque in the arterial wall, can progress to severe ischemia and lead to tissue necrosis and limb amputation. We evaluated a means of assessing PAD mechanics ex vivo using ten human peripheral arteries with PAD. Pressure-inflation testing was performed at six physiological pressure intervals ranging from 10-200 mmHg. These vessels were imaged with IVUS-VH to determine plaque composition and change in vessel structure with pressure. Statistical analysis was performed to determine which plaque structures and distributions of these structures had the greatest influence on wall deformation. We found that fibrous plaque, necrotic core, and calcification had a statistically significant effect on all variables (p<0.05). The presence of large concentrations of fibrous plaque was linked to reduced vessel compliance and ellipticity, which could lead to stent fractures and restenosis. For the plaque distribution we found that clustered necrotic core increased overall compliance while clustered calcification decreased overall compliance. The effect of plaque distribution on vessel wall deformation must be considered equally important to plaque concentration.

Chronic care service delivery models for people living with type 1 diabetes in low- and lower-middle income countries: a scoping review protocol

OBJECTIVE

The objective of this scoping review is to map the published literature that describes the distribution and organization of chronic care service delivery models for people living with type 1 diabetes (PLWT1D) in low- and lower-middle-income countries (LLMICs).

INTRODUCTION

Type 1 diabetes is an autoimmune condition commonly diagnosed in childhood and early adolescence; it cannot be prevented and is deadly without daily insulin injections. Among PLWT1D, the islet cells in the pancreas produce insufficient amounts of the glucose-regulating hormone, insulin, resulting in the need for chronic insulin replacement therapy. Epidemiological information regarding type 1 diabetes (T1D) is limited in LLMICs. Improving survival for PLWT1D in LLMICs requires early diagnosis and greater access to high quality chronic care service delivery models for T1D. The identification and reporting of service delivery model typologies for PLWT1D will allow for more specific research questions regarding individual typologies in subsequent systematic reviews.

INCLUSION CRITERIA

The review will consider all types of literature on the organization and distribution of chronic care services for the management of PLWT1D provided out of facilities in LLMICs, published from 2000 to the present.

METHODS

The JBI methodology for conducting scoping reviews will be employed. The search will be implemented across PubMed, Embase, and Web of Science. Full texts of the publications selected will be reviewed and data will be extracted through a charting table. The findings will be charted to summarize the results.

Rate-Dependent and Relaxation Properties of Porcine Aortic Heart Valve Biomaterials

Objective: This work evaluates the rate-dependent and relaxation properties of native porcine heart valves, glutaraldehyde fixed porcine pericardium, and decellularized sterilized porcine pericardium. Methods: Biaxial tension testing was performed at strain-rates of 0.001 s⁻¹, 0.01 s⁻¹, 0.1 s⁻¹, and 1 s⁻¹. Finally, relaxation testing for 300 s was performed on all heart valve biomaterials. Results: No notable rate-dependent response was observed for any of the three biomaterials with few significant differences between any strain-rates. For relaxation testing, native tissues showed the most pronounced drop in stress and glutaraldehyde the lowest drop in stress although no tissues showed anisotropy in the relaxation. Conclusions: Increasing the strain-rate of the three biomaterials considered does not increase the stress within the tissue. This indicates that there will not be increased fatigue from accelerated wear testing compared to loading at physiological strain-rates as the increase strain-rates would likely not significantly alter the tissue stress.

A Metabolic Intravascular Platform to Study FDG Uptake in Vascular Injury

PURPOSE

Metabolic alterations underlie many pathophysiological conditions, and their understanding is critical for the development of novel therapies. Although the assessment of metabolic changes in vivo has been historically challenging, recent developments in molecular imaging have allowed us to study novel metabolic research concepts directly in the living subject, bringing us closer to patients. However, in many instances, there is need for sensors that are in close proximity to the organ under investigation, for example to study vascular metabolism.

METHODS

In this study, we developed and validated a metabolic detection platform directly in the living subject under an inflammatory condition. The signal collected by a scintillating fiber is amplified using a photomultiplier tube and decodified by an in-house tunable analysis platform. For in vivo testing, we based our experiments on the metabolic characteristics of macrophages, cells closely linked to inflammation and avid for glucose and its analog ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG). The sensor was validated in New Zealand rabbits, in which inflammation was induced by either a) high cholesterol (HC) diet for 16 weeks or b) vascular balloon endothelial denudation followed by HC diet.

RESULTS

There was no difference in weight, hemodynamics, blood pressure, or heart rate between the groups. Vascular inflammation was detected by the metabolic sensor (Inflammation: 0.60 ± 0.03 AU vs. control: 0.48 ± 0.03 AU, p = 0.01), even though no significant inflammation/atherosclerosis was detected by intravascular ultrasound, underscoring the high sensitivity of the system. These findings were confirmed by the presence of macrophages on ex vivo aortic tissue staining.

CONCLUSION

In this study, we validated a tunable very sensitive metabolic sensor platform that can be used for the detection of vascular metabolism, such as inflammation. This sensor can be used not only for the detection of macrophage activity but, with alternative probes, it could allow the detection of other pathophysiological processes.

Mechanical and finite element evaluation of a bioprinted scaffold following recellularization in a rat subcutaneous model

Tissue engineered heart valves (TEHV) provide several advantages over currently available aortic heart valve replacements. Bioprinting provides a patient-specific means of developing a TEHV scaffold from imaging data, and the capability to embed the patient's own cells within the scaffold. In this work we investigated the remodeling capacity of a collagen-based bio-ink by implanting bioprinted disks in a rat subcutaneous model for 2, 4 and 12 weeks and evaluating the mechanical response using biaxial testing and subsequent finite element (FE) modeling. Samples explanted after 2 and 4 weeks showed inferior mechanical properties compared to native tissues while 12 week explants showed a mechanical response of similar magnitude but did not demonstrate the anisotropy present in native tissues. In the FE analysis, the model utilizing mechanical properties from samples explanted after 12 weeks showed the closest mechanical behavior to the native tissues. However, in diastole native tissues showed higher stress in the leaflet belly and lower strain at the commissures compared to 12 week explants, likely due to the anisotropy present in the native tissues. Thus, either further remodeling is required in situ in the aortic valve position or by in vitro preconditioning in an environment such as a bioreactor. Regardless, these results demonstrate the utility of FE analysis to optimize bioprinting process parameters for the most favorable in vivo mechanical performance.

Patient specific characterization of artery and plaque material properties in peripheral artery disease

Patient-specific finite element (FE) modeling of atherosclerotic plaque is challenging, as there is limited information available clinically to characterize plaque components. This study proposes that for the limited data available in vivo, material properties of plaque and artery can be identified using inverse FE analysis and either a simple neo-Hookean constitutive model or assuming linear elasticity provides sufficient accuracy to capture the changes in vessel deformation, which is the available clinical metric. To test this, 10 human cadaveric femoral arteries were each pressurized ex vivo at 6 pressure levels, while intravascular ultrasound (IVUS) and virtual histology (VH) imaging were performed during controlled pull-back to determine vessel geometry and plaque structure. The VH images were then utilized to construct FE models with heterogeneous material properties corresponding to the vessel plaque components. The constitutive models were then fit to each plaque component by minimizing the difference between the experimental and the simulated geometry using the inverse FE method. Additionally, we further simplified the analysis by assuming the vessel wall had a homogeneous structure, i.e. lumping artery and plaque as one tissue. We found that for the heterogeneous wall structure, the simulated and experimental vessel geometries compared well when the fitted neo-Hookean parameters or elastic modulus, in the case of linear elasticity, were utilized. Furthermore, taking the median of these fitted parameters then inputting these as plaque component mechanical properties in the finite element simulation yielded differences between simulated and experimental geometries that were on average around 2% greater (1.30-5.55% error range to 2.33-11.71% error range). For the homogeneous wall structure the simulated and experimental wall geometries had an average difference of around 4% although when the difference was calculated using the median fitted value this difference was larger than for the heterogeneous fits. Finally, comparison to uniaxial tension data and to literature constitutive models also gave confidence to the suitability of this simplified approach for patient-specific arterial simulation based on data that may be acquired in the clinic.

Effect of cyclic deformation on xenogeneic heart valve biomaterials

Glutaraldehyde-fixed bovine pericardium is currently the most popular biomaterial utilized in the creation of bioprosthetic heart valves. However, recent studies indicate that glutaraldehyde fixation results in calcification and structural valve deterioration, limiting the longevity of bioprosthetic heart valves. Additionally, glutaraldehyde fixation renders the tissue incompatible with constructive recipient cellular repopulation, remodeling and growth. Use of unfixed xenogeneic biomaterials devoid of antigenic burden has potential to overcome the limitations of current glutaraldehyde-fixed biomaterials. Heart valves undergo billion cycles of opening and closing throughout the patient’s lifetime. Therefore, understanding the response of unfixed tissues to cyclic loading is crucial to these in a heart valve leaflet configuration. In this manuscript we quantify the effect of cyclic deformation on cycle dependent strain, structural, compositional and mechanical properties of fixed and unfixed tissues. Glutaraldehyde-fixed bovine pericardium underwent marked cyclic dependent strain, resulting from significant changes in structure, composition and mechanical function of the material. Conversely, unfixed bovine pericardium underwent minimal strain and maintained its structure, composition and mechanical integrity. This manuscript demonstrates that unfixed bovine pericardium can withstand cyclic deformations equivalent to 6 months of in vivo heart valve leaflet performance.

In Silico Performance of a Recellularized Tissue Engineered Transcatheter Aortic Valve

Commercially available heart valves have many limitations, such as a lack of re-modeling, risk of calcification and thromboembolic problems. Many state-of-the-art tissue engineered heart valves rely on recellularization. Current in vitro testing is insufficient in characterizing a soon to be living valve. It is imperative to understand the performance of an in situ valve, but due to the complex in vivo environment this is difficult to accomplish. Finite element analysis has become a standard tool for modeling mechanical behavior of heart valves; yet, research to date has mostly focused on commercial valves. The purpose of this study has been to develop finite element models of a decellularized and recellularized tissue engineered heart valve. Mechanical properties from porcine aortic valves were utilized to develop finite element models, which were run through a full physiological cardiac cycle. Maximum principal stresses and strains from the leaflets and commissures were analyzed. The results of this study demonstrate that the explanted tissues had reduced mechanical strength compared to the implants but were similar to the native tissues. For the finite element models the explanted recellularized leaflets showed lower stress but increased compliance in the leaflet belly compared to native tissues and higher compliance than implant tissues. Histology demonstrated recellularization and remodeling although remodeled collagen had no clear directionality. In conclusion, we observed successful recellularization and remodeling of the tissue, however, the mechanical response indicates the further remodeling is required following implantation in the aortic/pulmonary position.

Evaluation of a multispecies probiotic as a supportive treatment for diarrhea in dairy calves: A randomized clinical trial

The objectives of this randomized clinical trial were to determine whether the utilization of a multispecies probiotic bolus (MSP) in dairy calves with diarrhea led to a rapid resolution of diarrhea and improved average daily gain (ADG). Calves, from a convenience sample of dairy farms with diarrhea challenges, having fecal scores of ≥2 were randomly assigned to receive MSP or a placebo (PLB). The MSP bolus contained Pediococcus acidilactici, Enterococcus faecium, Lactobacillus acidophilus, Lactobacillus casei, Bifidobacterium bifidum, peptide extract, an enzyme blend, killed yeast extract, dried whey, and natural flavors (Revive, Partnar Animal Health, Ilderton, ON, Canada). The enrolled calves were fecal scored daily for 7 consecutive days and resolution of diarrhea was defined as having 2 consecutive days with a fecal score ≤1. Calves were also weighed at enrollment, 7, and 14 d following enrollment and ADG was calculated. A Cox proportional hazards model was built to investigate time to resolution of an abnormal fecal score. Two mixed linear regression models were created to evaluate the effect of treatment group on ADG in the first and second weeks following enrollment. A total of 148 calves were enrolled in the experiment and no differences were observed between the groups with respect to the age or weight at enrollment. The mean time to resolution of abnormal fecal score was 5.1 and 5.9 d in the MSP and PLB groups, respectively. In the Cox proportional hazards model, the calves in the MSP group had faster resolution of diarrhea when compared with the PLB group; however, an interaction between time from enrollment of the first calf and treatment group was present. No differences were found between the 2 groups with respect to ADG. This study demonstrates a multispecies probiotic and yeast bolus administered to calves at the onset of diarrhea reduced the duration of diarrhea; however, the clinical and economic relevance of this reduction requires further exploration.

In Vivo Response of Acellular Porcine Pericardial for Tissue Engineered Transcatheter Aortic Valves

Current heart valve prostheses have limitations that include durability, inability to grow in pediatric patients, and lifelong anticoagulation. Transcatheter aortic valve replacements are minimally invasive procedures, and therefore have emerged as an alternative to traditional valve prostheses. In this experiment, the regenerative capacity of potential tissue engineered transcatheter valve scaffolds (1) acellular porcine pericardium and (2) mesenchymal stem cell-seeded acellular porcine pericardium were compared to native porcine aortic valve cusps in a rat subcutaneous model for up to 8 weeks. Immunohistochemistry, extracellular matrix evaluation, and tissue biomechanics were evaluated on the explanted tissue. Acellular valve scaffolds expressed CD163, CD31, alpha smooth muscle actin, and vimentin at each time point indicating host cell recellularization; however, MSC-seeded tissue showed greater recellularization. Inflammatory cells were observed with CD3 biomarker in native porcine pericardial tissue throughout the study. No inflammation was observed in either acellular or MSC-seeded scaffolds. There was no mechanical advantage observed in MSC-seeded tissue; however after the first week post-explant, there was a decrease in mechanical properties in all groups (p < 0.05). MSC-seeded and acellular porcine pericardium expressed decreased inflammatory response and better host-cell recellularization compared to the native porcine aortic valve cusps.

Experimental Metabolic Syndrome Model Associated with Mechanical and Structural Degenerative Changes of the Aortic Valve

The purpose of this study was to test the hypothesis that an experimental high fat (HF) animal with metabolic syndrome results in structural degeneration of the aortic valve. Domestic pigs were divided (n = 12) and administered either a normal or HF diet. After 16-weeks, the HF diet group had increased weight (p ≤ 0.05), total cholesterol (p ≤ 0.05), and systolic and diastolic pressure (p ≤ 0.05). The aortic valve extracellular matrix showed loss of elastin fibers and increased collagen deposition in the HF diet group. Collagen was quantified with ELISA, which showed an increased concentration of collagen types 1 and 3 (p ≤ 0.05). In the HF diet group, the initial stages of microcalcification were observed. Uniaxial mechanical testing of aortic cusps revealed that the HF diet group expressed a decrease in ultimate tensile strength and elastic modulus compared to the control diet group (p ≤ 0.05). Western blot and immunohistochemistry indicated the presence of proteins: lipoprotein-associated phospholipase A2, osteopontin, and osteocalcin with an increased expression in the HF diet group. The current study demonstrates that experimental metabolic syndrome induced by a 16-week HF diet was associated with a statistically significant alteration to the physical architecture of the aortic valve.

Cancer-Related Stigma in South Africa: Exploring Beliefs and Experiences Among Cancer Patients and the General Public

Background: Stigma refers to a distinctive, discrediting characteristic, rendering its bearer tainted or inferior by others. Definitions of stigma acknowledge the recognition of difference; and devaluation. Evidence, largely from high-income countries suggests that cancer is a stigmatized disease. Cancer-related stigma is not well-documented in South Africa, and little is known about how it impacts health-seeking behavior, treatment adherence, quality of life and psychosocial well-being in cancer patients. Limited research has explored perceptions and cultural representations of cancer but an in-depth focus on this is lacking. This context-specific information is essential for relevant, effective intervention. Aim: This study aims to increase understanding of cancer-related stigma in South Africa and the role of cultural beliefs in contributing to this. Findings will be used to inform a larger study and ultimately, interventions to address cancer-related stigma in communities in which the Cancer Association of South Africa (CANSA) is working. Methods: This qualitative study was conducted in two provinces of South Africa, KwaZulu Natal and the Western Cape and included participants from a range of cultural and racial groups. Cancer patients over 18 years were recruited through CANSA's Service Delivery teams to participate in focus groups or one to one in depth interviews. Six focus groups and 40 in depth interviews were conducted with cancer patients. Data collection focused on understanding patient experiences of cancer stigma; cognitive, emotional and behavioral responses to this; and inputs on interventions to address this. Six focus groups were also conducted with noncancer patients recruited from local communities to explore cultural perceptions of cancer and reasons for stigmatization. Audio recordings were transcribed and translated; coded using NVivo 11; and analyzed by the authors using thematic analysis. Results: Results indicated very poor knowledge of cancer both in patients and nonpatients. Overwhelmingly, findings highlight the perception of cancer as a “death sentence”, influencing patients' experiences and responses of others in numerous ways. The influence of cultural beliefs was relevant, exacerbating stigma in some cases. The location of the cancer also played a role in determining level of stigmatization. Certain body parts (associated with masculine and feminine roles) as well as more visible cancers/side-effects were more stigmatised. Conclusion: Results indicate that stigmatization is a significant factor for cancer patients in South Africa, increasing social isolation and negatively impacting quality of life. The implications of the findings for intervention development will be discussed. Education is needed but requires a different focus for different cultural groups.

A novel surgical technique for a rat subcutaneous implantation of a tissue engineered scaffold

Objectives

Subcutaneous implantations in small animal models are currently required for preclinical studies of acellular tissue to evaluate biocompatibility, including host recellularization and immunogenic reactivity.

Methods

Three rat subcutaneous implantation methods were evaluated in six Sprague Dawley rats. An acellular xenograft made from porcine pericardium was used as the tissue-scaffold. Three implantation methods were performed; 1) Suture method is where a tissue-scaffold was implanted by suturing its border to the external oblique muscle, 2) Control method is where a tissue-scaffold was implanted without any suturing or support, 3) Frame method is where a tissue-scaffold was attached to a circular frame composed of polycaprolactone (PCL) biomaterial and placed subcutaneously. After 1 and 4 weeks, tissue-scaffolds were explanted and evaluated by hematoxylin and eosin (H&E), Masson’s trichrome, Picrosirius Red, transmission electron microscopy (TEM), immunohistochemistry, and mechanical testing.

Results

Macroscopically, tissue-scaffold degradation with the suture method and tissue-scaffold folding with the control method were observed after 4 weeks. In comparison, the frame method demonstrated intact tissue scaffolds after 4 weeks. H&E staining showed progressive cell repopulation over the course of the experiment in all groups with acute and chronic inflammation observed in suture and control methods throughout the duration of the study. Immunohistochemistry quantification of CD3, CD 31, CD 34, CD 163, and αSMA showed a statistically significant differences between the suture, control and frame methods (P < 0.05) at both time points. The average tensile strength was 4.03 ± 0.49, 7.45 ± 0.49 and 5.72 ± 1.34 (MPa) after 1 week and 0.55 ± 0.26, 0.12 ± 0.03 and 0.41 ± 0.32 (MPa) after 4 weeks in the suture, control, and frame methods; respectively. TEM analysis showed an increase in inflammatory cells in both suture and control methods following implantation.

Conclusion

Rat subcutaneous implantation with the frame method was performed with success and ease. The surgical approach used for the frame technique was found to be the best methodology for in vivo evaluation of tissue engineered acellular scaffolds, where the frame method did not compromise mechanical strength, but it reduced inflammation significantly.

The photoreactive free radical in eumelanin

Melanin is the primary photoprotecting pigment in humans as well as being implicated in the development of deadly melanoma. The material also conducts electricity and has thus become a bioelectronic model for proton-to-electron transduction. Central to these phenomena are its spin properties-notably two linked species derived from carbon-centered and semiquinone radicals. Using a novel in situ photoinduced electron paramagnetic resonance technique with simultaneous electrical measurements, we have elucidated for the first time the distinct photoreactivity of the two different radical species. We find that the production of the semiquinone is light- and water-driven, explaining the electrical properties and revealing biologically relevant photoreactivity.

A simple method of incorporating the effect of the Uniform Stress Hypothesis in arterial wall stress computations

PURPOSE

Residual stress has a great influence on the mechanical behaviour of arterial wall. Numerous research groups used the Uniform Stress Hypothesis to allow the inclusion of the effects of residual stress when computing stress distributions in the arterial wall. Nevertheless, the available methods used for this purpose are very computationally expensive, due to their iterative nature. In this paper we present a new method for including the effects of residual stress on the computed stress distribution in the arterial wall.

METHODS

The new method, by using the Uniform Stress Hypothesis, enables computing the effect of residual stress by averaging stresses across the thickness of the arterial wall.

RESULTS

Being a post-processing method for the computed stress distributions, the proposed method is computationally inexpensive, and thus, better suited for clinical applications than the previously used ones.

CONCLUSIONS

The resulting stress distributions and values obtained using the proposed method based on the Uniform Stress Hypothesis are very close to the ones returned by an existing iterative method.

Theory of High-Spin d(4) Complexes: An Angular-Overlap Model Parametrization of the Ligand Field in Vibronic-Coupling Calculations

A new theoretical approach for the calculation of the electronic and molecular structures of octahedrally-coordinated high-spin d(4) complexes is described. A prescription for the construction of an effective (3)T1 + (5)E (O) Hamiltonian from the ligand-field matrices of a complex with general trigonal symmetry is given, where the ligand field is parametrized in terms of the angular-overlap model (AOM). The Jahn-Teller matrices for the (3)T1 + ((5)E⊗e) vibronic Hamiltonian are constructed and the lowest eigenvalues are calculated by a numerical method. The model obviates the need to assume a temperature dependence of bonding parameters, inherent to the conventional ligand-field-theory approach and is applicable over the whole range of vibronic-coupling strengths, as demonstrated by example calculations on the [Mn(OD2)6](3+) cation and MgO:Cr(2+).

A Predictive Model of Vertebral Trabecular Anisotropy From Ex Vivo Micro-CT

Spine-related disorders are amongst the most frequently encountered problems in clinical medicine. For several applications such as 1) to improve the assessment of the strength of the spine, as well as 2) to optimize the personalization of spinal interventions, image-based biomechanical modeling of the vertebrae is expected to play an important predictive role. However, this requires the construction of computational models that are subject-specific and comprehensive. In particular, they need to incorporate information about the vertebral anisotropic micro-architecture, which plays a central role in the biomechanical function of the vertebrae. In practice, however, accurate personalization of the vertebral trabeculae has proven to be difficult as its imaging in vivo is currently infeasible. Consequently, this paper presents a statistical approach for accurate prediction of the vertebral fabric tensors based on a training sample of ex vivo micro-CT images. To the best of our knowledge, this is the first predictive model proposed and validated for vertebral datasets. The method combines features selection and partial least squares regression in order to derive optimal latent variables for the prediction of the fabric tensors based on the more easily extracted shape and density information. Detailed validation with 20 ex vivo T12 vertebrae demonstrates the accuracy and consistency of the approach for the personalization of trabecular anisotropy.

Fast size-determination of intact bacterial plasmids using nanofluidic channels

We demonstrate how nanofluidic channels can be used as a tool to rapidly determine the number and sizes of plasmids in bacterial isolates. Each step can be automated at low cost, opening up opportunities for general use in microbiology labs.

Visualizing the entire DNA from a chromosome in a single frame

The contiguity and phase of sequence information are intrinsic to obtain complete understanding of the genome and its relationship to phenotype. We report the fabrication and application of a novel nanochannel design that folds megabase lengths of genomic DNA into a systematic back-and-forth meandering path. Such meandering nanochannels enabled us to visualize the complete 5.7 Mbp (1 mm) stained DNA length of a Schizosaccharomyces pombe chromosome in a single frame of a CCD. We were able to hold the DNA in situ while implementing partial denaturation to obtain a barcode pattern that we could match to a reference map using the Poland-Scheraga model for DNA melting. The facility to compose such long linear lengths of genomic DNA in one field of view enabled us to directly visualize a repeat motif, count the repeat unit number, and chart its location in the genome by reference to unique barcode motifs found at measurable distances from the repeat. Meandering nanochannel dimensions can easily be tailored to human chromosome scales, which would enable the whole genome to be visualized in seconds.

A constitutive model for ballistic gelatin at surgical strain rates

This paper describes a constitutive model for ballistic gelatin at the low strain rates experienced, for example, by soft tissues during surgery. While this material is most commonly associated with high speed projectile penetration and impact investigations, it has also been used extensively as a soft tissue simulant in validation studies for surgical technologies (e.g. surgical simulation and guidance systems), for which loading speeds and the corresponding mechanical response of the material are quite different. We conducted mechanical compression experiments on gelatin specimens at strain rates spanning two orders of magnitude (~0.001-0.1s(-1)) and observed a nonlinear load-displacement history and strong strain rate-dependence. A compact and efficient visco-hyperelastic constitutive model was then formulated and found to fit the experimental data well. An Ogden type strain energy density function was employed for the elastic component. A single Prony exponential term was found to be adequate to capture the observed rate-dependence of the response over multiple strain rates. The model lends itself to immediate use within many commercial finite element packages.

Does feeding time affect fish welfare?

Increased aquaculture production has raised concerns about managing protocols to safeguard the welfare of farmed fish, as consumers demand responsible aquaculture practices to provide 'welfare friendly' products. Feeding is one of the largest production cost in a fish farm and can be one of the biggest stressors for fish. Under farming conditions, fish are challenged with artificial diets and feeding regimes, and inadequate feeding conditions cause stress, alteration of normal behavioural patterns, poor performance and eventually diseases and death, which are by no means acceptable neither economically nor ethically. This review aims to highlight the impact of feeding rhythms and feeding time upon physiological and behavioural welfare indicators, which show circadian rhythms as well. Therefore, all these variables should be considered when designing feeding strategies in farming conditions and assessing the welfare state of cultured fish.

Increase in de novo allergies after paediatric liver transplantation: the Brisbane experience

  Pediatric liver transplantation is a successful procedure with 10-yr survival rate of 70%; following transplantation, the emphasis on promoting good quality of life is important. The increasing prevalence of allergic disorders in the general population and an increase in food allergy following solid organ transplantation are described in patients, especially in children, but the contribution to morbidity post-OLT has not been addressed.

OBJECTIVES

Identifying the incidence de novo allergies post-OLT performed by QLTS over 11 yr.

METHODS

Comprehensive medical record review of OLT recipients during study period.

RESULTS

From 1st July 1998 to 1st August 2009, 78 children received 85 cadaveric OLT; 60 children survived. Allergic disease was documented in 24/60 (40%) survivors. De novo food allergies were diagnosed in 12/60 (20%) (Table 2), 9/12 occurred in children who were infants at time of transplant. Ten of 12 had severe allergies, six anaphylactic; 6/60 (10%) carry an EpiPen. Only 31/60 (51%) diagnosed are followed in Queensland, suggesting severe allergic disease in our cohort is an underestimate.

CONCLUSION

Serious allergic disease post-OLT is clinically important, especially in infants at time of transplant, and should be targeted for specialist allergist referral and risk management. [Table: see text].

Audit of eosinophilic oesophagitis in children post-liver transplant

Pediatric liver transplantation has proven so successful that 10-yr survival post-transplantation is in excess of 70% and following transplantation, emphasis of medical care switches from life saving to promotion of good quality of life. EE is an increasingly recognised phenomenon in the general population. Eosinophilic disorders of the GI tract are increasingly recognised in patient's post-solid organ transplantation but the contribution of EE to morbidity in this population has not been addressed to date. The objective of this study was to identify the incidence of EE in children receiving liver transplantation by the QLTS over the last 15.5 yr. Comprehensive review of medical records of all liver transplant recipients during study period via cross-checking procedural and electronic laboratory results was performed. All oesophageal biopsies reporting mucosal inflammation were reviewed. EE can be diagnosed when oesophageal biopsy reveals > or =5 eosinophils per HPF; however, we used a cut-off of 20 eosinophils per HPF, which is in accordance with current opinion. In the 159 children who received DD OLT, 130 survived and four have been diagnosed with EE (3%). Only 34 are currently followed in Queensland and all four patients diagnosed are in this cohort representing 12% of our follow-up clinic. Many patients are followed elsewhere so occurrence of EE in our total surviving population is an underestimate. EE is clinically important in the post-liver transplant community. Children post-OLT who have upper GI symptoms should be considered for endoscopic evaluation and biopsy to exclude EE.