Identification of Mechanical Parameters in Mathematical Model of Human Abdominal Fascia

Миглена Г. Кирилова-Донева - Едномерен експеримент на релаксация беше извършен с 14 образци от човешка пъпна фасция. Механичното поведение на фасцията по време на релаксация беше моделирано прилагайки нелинейната теория на Максвел-Гуревич-Рабинович. Параметрите на модела за изследваните образци бяха определени и стойностите им бяха сравнени в зависимост от посоката на натоварване на образците по време на експеримента. Установено бе, че стойностите на началния вискозитет ∗η0 и на параметъра ∗m, който се влияе от скоростта на деформация на материала се изменят в много широки граници не само за образци от различни донори, но и за образци от един донор. В резултат от прилагането на модела бе изчислено изменението на вискозитета и вискозната деформация на материала по време на релаксацията. Бе показано, че изменението на вискозитета и вискозната деформация зависи от посоката на натоварване на образците.

In vivo biocompatibility evaluation of composite polymeric materials for use in a novel artificial heart valve

A novel trileaflet polymer valve is a composite design of a biostable polymer poly(styrene-isobutylene-styrene) (SIBS) with a reinforcement polyethylene terephthalate (PET) fabric. Surface roughness and hydrophilicity vary with fabrication methods and influence leaflet biocompatibility. The purpose of this study was to investigate the biocompatibility of this composite material using both small animal (nonfunctional mode) and large animal (functional mode) models. Composite samples were manufactured using dip coating and solvent casting with different coating thickness (251μm and 50μm). Sample's surface was characterized through qualitative SEM observation and quantitative surface roughness analysis. A novel rat abdominal aorta model was developed to test the composite samples in a similar pulsatile flow condition as its intended use. The sample's tissue response was characterized by histological examination. Among the samples tested, the 25μm solvent-cast sample exhibited the smoothest surface and best biocompatibility in terms of tissue capsulation thickness, and was chosen as the method for fabrication of the SIBS valve. Phosphocholine was used to create a hydrophilic surface on selected composite samples, which resulted in improved blood compatibility. Four SIBS valves (two with phosphocholine modification) were implanted into sheep. Echocardiography, blood chemistry, and system pathology were conducted to evaluate the valve's performance and biocompatibility. No adverse response was identified following implantation. The average survival time was 76 days, and one sheep with the phosphocholine modified valve passed the FDA minimum requirement of 140 days with approximately 20 million cycles of valve activity. The explanted valves were observed under the aid of a dissection microscope, and evaluated via histology, SEM and X-ray. Surface cracks and calcified tissue deposition were found on the leaflets. In conclusion, we demonstrated the applicability of using a new rat abdominal aorta model for biocompatibility assessment of polymeric materials. A smooth and complete coating surface is essential for the biocompatibility of PET/SIBS composite, and surface modification using phosphocholine improves blood compatibility. Extrinsic calcification was identified on the leaflets and was associated with regions of surface cracks.

Ethnic Differences in Insulin Resistance, Adiponectin Levels and Abdominal Obesity: Haitian Americans and African Americans, with and without Type 2 Diabetes Mellitus

Background: Metabolic outcomes of obesity and its associated disorders may not be equivalent across ethnicity and diabetes status. Aim: In this paper, we examined the association of abdominal obesity, by ethnicity and diabetes status, for indicators of glucose metabolism in Blacks. Methods: A cross sectional study was conducted in Haitian Americans (n= 186) and African Americans (n= 148) with and without type 2 diabetes mellitus (T2DM). Student’s t-test and Chi-squared test were used to assess differences in mean and proportion values between ethnicities with and without type 2 diabetes mellitus. Relationship between insulin resistance, ethnicity, diabetes status, abdominal obesity, and adiponectin levels were analyzed by analysis of covariance while controlling for confounding variables. Results:Haitian American participants were older (P = .032), had higher fasting plasma glucose (P = .036), and A1C (P = .016), but had lower levels of Hs-CRP (P < .001), insulin and HOMA2-IR and lower abdominal obesity (P = .030), than African Americans. Haitian Americans had significantly lower HOMA2-IR (P = .008) than African Americans when comparing both ethnicities with T2DM, high abdominal obesity, and adiponectin levels lower than the median ( Conclusion: The clinical significance of observed differences in insulin resistance, abdominal obesity, and adiponectin levels between Haitian Americans and African Americans could assist in forming public health policies that are ethnic specific.

Efeito agudo da respiração abdominal lenta sobre a atividade cerebral, respostas emocionais e cardiovasculares

Introduction: Slow abdominal breathing (SAB) stimulates baroreflex and generates respiratory sinus arrhythmia, changing cardiovascular, emotional and cerebral systems acute and chronically. However, although meditative practices have been receiving increasingly attention in the last years, there is no agreement on the neurophysiological changes underlying them, mainly because of the lack of topographical pieces of information. Purpose: We aimed to analyze the acute effect of SAB on brain activity, emotional and cardiovascular responses in untrained subjects in meditative techniques. Methods: Seventeen healthy adults’ men were assessed into two different sessions in a random and crossed order. Into experimental session, they breathed in 6 cycles/minute and in control session they kept breathing in normal rate, both for 20 minutes. xi Before, during, and after each session we assessed brain activity using electroencephalography (EEG), anxiety, mood, heart rate variability (HRV) and blood pressure. The sLORETA software was used to analyze EEG data for source localization of brain areas in which activity was changed. Results: The sLORETA showed that beta band frequency was reduced in frontal gyrus (P<0.01) and anterior cingulate cortex (P<0.05) both during and after SAB (P<0.05) compared to the moment before it. There was no change in brain activity in control session. Additionally, a two-way repeated measures ANOVA showed that there was no effect on anxiety (P>0.8) and mood (P>0.08). There were improvements in HRV (P<0.03), with increased RR interval and decreased HR after SAB, as well as increased SDNN, RMSSD, pNN50, low frequency, LF/HF ratio, and total power during it, with no changes in SBP and DBP. Conclusions: We conclude that SAB is able to change brain activity in areas responsible for emotional processing, even without behavioral changes. Furthermore, SAB improves HRV and does not change blood pressure in normotensive.

Efecto de la electroestimulación muscular abdominal en el caballo

La especialidad de fisioterapia y rehabilitación veterinaria ha adquirido una importancia creciente experimentando un constante desarrollo en las últimas décadas. Prueba de ello es la aparición de varios cursos de postgrado en diferentes universidades veterinarias o la creación del American College of Veterinary Sports Medicine and Rehabilitation en 2010. En términos generales, esta especialidad se ha nutrido de los protocolos de medicina humana sin existir una base científica sólida, por lo que las publicaciones científicas en el campo veterinario, aunque han ido incrementando recientemente, son aún escasas. Por lo tanto, son necesarios estudios que exploren tratamientos, protocolos y métodos de valoración funcional en veterinaria. En la clínica equina, la fisioterapia se ha centrado en gran medida en la rehabilitación de lesiones musculoesqueléticas, donde los problemas de dorso son una de las principales causas de disminución del rendimiento en caballos de deporte. Su etiología suele ser multifactorial y su presentación hace difícil un diagnóstico claro. Basándonos en el modelo de medicina humana, donde se ha demostrado el papel vital que juega la musculatura multífida en la estabilidad dinámica de la columna y en el desarrollo de patologías, se han comenzado a describir diferentes programas de ejercicios en caballos con el objetivo de mejorar la estabilidad y el control motor del raquis. Aunque algunos han demostrado ser efectivos, aún se necesitan muchos estudios que pongan de manifiesto la aplicación clínica de estos protocolos y su metodología exacta de aplicación en medicina equina...

Activity and expression of Na/K-ATPase in thoracic aorta of normal pregnant and experimental preeclamptic rats

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.