Does the Animal Origin Influence the Calcification of Xenograft Tissue Heart Valve Substitutes? Comparison between Bovine and Camel Pericardium in a Subcutaneous Rat Model

Objective: To validate the hypothesis that camel pericardium could be more protected than bovine pericardium against calcification process according to the huge difference in their respective lifestyle and lifetime. Methods: Glutaraldehyde (GA) fixed bovine and camel pericardium samples (BP and CP respectively) were both implanted in 30 New Zealand white rats (2 BP and 2 CP matched specimens in each animal) and explanted after 60 days. Unimplanted GA-fixed samples of both species served as control. Matched implanted samples and unimplanted samples were randomly submitted to elemental analysis by spectroscopy, phospholipid extraction, macroscopic and X-ray examination and histology. Results: At 60 days, calcium and phosphorus content were respectively 9.54% ± 3.1% and 4.79% ± 1.4% of tissue dry weight in BP, and 12.52% ± 2.7% and 6.14% ± 1.3% of tissue dry weight in CP (ns). In X-ray analysis, the calcification score was 1.28 ± 0.45 and 2.14 ± 0.98 in BP and CP samples respectively without significant difference (p < 0.08). In histology, calcifications were lower in BP than in CP: 1.37 ± 0.85 vs 2.28 ± 0.83 (ns);collagen fibers were better conserved in BP than in CP: 2.4 ± 0.48 vs 1.87 ± 0.78 (ns), and less disoriented: 25% vs 62% (ns). In unimplanted samples, there was a higher but not significant rate of extracted lipids in CP: 5.7 ± 1.8 vs 9.5 ± 3.8 nanomoles in PS fraction and 11.3 ± 3.7 vs 19 ± 7.7 nanomoles in total fatty acids, in BP and CP samples respectively. All results were in conjunction and demonstrated a higher but not significant rate of mineralization in camel pericardium after implantation, which could be related to a higher but not significant basic rate of phospholipid and fatty acids. Conclusion: This experiment study in a subcutaneous rat model has failed to valid our hypothesis. Because the differences observed between bovine and camel pericardium did not reach the significance, at the best, there is no difference between both species and at the worst, camel pericardium has a higher rate of the phosphatidylserine fraction of phospholipid, and is more sensitive and prompt to calcification.

Longitudinal trajectories of athlete burnout among young table tennis players: A 3-wave study

Purpose:The purposes of this study were to examine the trajectories of athlete burnout across a 2-month period characterized by high physical,psychological,and social demands to explore(1)whether several subgroups of athletes representing distinct burnout trajectories emerged from the analyses and(2)whether athlete burnout symptoms(reduced accomplishment,sport devaluation,and exhaustion)developed in tandem or whether some burnout dimensions predicted downstream changes in other dimensions(causal ordering model).Methods:One hundred and fifty-nine table tennis players in intensive training centers completed a self-reported athlete burnout measure across 3 time points within a 2-month period characterized by high demands.Data were analyzed through latent class growth analysis.Results:Results of latent class growth analysis showed 3 distinct trajectories for each athlete burnout dimension,indicating not only linear or quadratic change but also stability in longitudinal athlete burnout perceptions.Results also suggested that the 3 dimensions of athlete burnout did not develop in tandem.Rather,the likelihood of belonging to particular emerging trajectories of sport devaluation and physical/emotional exhaustion was significantly influenced by the athletes’perception of reduced accomplishment assessed at Time 1.Thus,reduced accomplishment predicted downstream changes in the 2 other athlete burnout dimensions.Conclusion:As a whole,these results highlighted that the multinomial heterogeneity in longitudinal athlete burnout symptoms needs to be accounted for in future research.

Environmental adaptations and constraints on latest Cretaceous Arctic dinosaurs

The Arctic hosts an extraordinary wealth of terrestrial fossil biotas of Late Cretaceous age representing a diverse and highly productive near-polar ecosystem that has no modern analogue. Compared to the rest of the Late Cretaceous Maastrichtian plant diversity was at its lowest and the temperature regime the coolest,yet the semi-open forests supported a rich dinosaur fauna made up of a wide range of body sizes and feeding strategies.The combination of mild winter temperatures and continuous darkness lasting several months imposed severe constraints on primary productivity. Plant survival strategies involved almost universal winter loss of foliage,which in turn limited food supply for non-migratory overwintering herbivorous animals. A combination of leaf form and tree ring studies has been used to quantify year round variations in temperature and determine the timing of spring bud-break and autumnal leaf fall. While Maastrichtian winter temperatures were cold enough( down to- 10℃ for brief intervals) for frequent frosts and snowfall,summer temperatures were cool but highly variable and at ~ 83 ° N along the north Alaskan coast frequently fell below + 10 ℃. Theropod egg shell fragments at ~ 76 ° N in the Maastrichtian of Northeastern Russia may indicate that dinosaur reproduction took place in the Arctic ecosystem,as distinct from taking place at lower latitude breeding grounds reached by migration.This raises the question of nest management and specifically the maintenance of incubation temperatures,and the duration of incubation. Of critical importance to year-round residency is the timing of hatching and juvenile care before winter darkness set in,temperatures fell to near freezing and food resources became limited.

Host evolution in Mastomys natalensis(Rodentia:Muridae):An integrative approach using geometric morphometrics and genetics

The commensal rodent Mastomys natalensis is the natural reservoir of Lassa arenavirus(LASV),which causes hemorrhagic fever in West Africa.To study a possible effect of the virus on phenotypic and genotypic variation of its persistently infected host,we compared LASV-positive and non-infected wild-caught M.natalensis.The LASV effects on the phenotypic variation were explored using standard external morphometric measurements,geometric morphometric analyses of the cranial size and shape,and brain case volume.The genetic variability of M.natalensis specimens was assessed using 9 polymorphic microsatellite markers.Independent of sex and age,LASV-infected animals had smaller external body measurements,reproductive organs,skull size and brain case volume.Cranial shape differences between the 2 groups are represented by a lateral constriction of the entire skull.The genetic variability revealed consanguinity only among the LASV-positive rodents.We hypothesize that growth impairment may result in a selective disadvantage for LASV-infected M.natalensis,leading to a preferably commensal lifestyle in areas where the LAVS is endemic and,thereby,increasing the risk of LASV transmission to humans.