Haemodynamic Analysis of the Relationship between the Morphological Alterations of the Ascending Aorta and the Type A Aortic-Dissection Disease

Type A aortic dissection(AD)is one of the most serious cardiovascular diseases,whose risk predictors are controversial.The purpose of this research was to investigate how elongation accompanied by dilation of the ascending aorta(AAo)affects the relevant haemodynamic characteristics using image-based computational models.Five elongated AAos with different levels of dilation have been reconstructed based on the centerlines data of an elderly and an AD patient.Numerical simulations have been performed assuming an inflow waveform and a Windkessel model with three elements for all outflow boundaries.The numerical results have revealed that the elongation of AAo can disturb the systolic helical flow pattern between the root of AAo and the aortic arch.The helical flow inside the AAo starts to develop into a vortex flow when the elongated AAo becomes dilated.The vortex gives rise to a localized oscillatory shear index at the ostia of the brachiocephalic artery(BA)and the inner curve of the aortic arch.This study suggests that abnormal growth of AAo,especially accompanied by its moderate dilation,can be considered as morphological risk factors of AD.

Effects of Low Temperature Stress on the Morphology and hsp70 and hsp90 Gene Expression of Phascolosoma esculenta

Phascolosoma esculenta is an intertidal organism that has recently attracted attention because of its ability to survive at relatively low temperatures.However,the gene regulation in P.esculenta in relation to its response to low temperatures is unclear.To explore the low temperature adaptability of P.esculenta,this study analyzed the changes in the morphology and hsp70 and hsp90 gene expression of P.esculenta exposed to a low temperature gradient.At 5℃,P.esculenta stretched and softened,and some individuals moved apart from the group.Histological analysis revealed cuticle breaches,myofiber scattering,disruption of the body wall,and epithelial layer dispersion and muscle fiber rupturing in the nephridium.Furthermore,the mRNA expression levels of hsp70 and hsp90 increased under acute low temperature stress,suggesting that these genes function in low temperature tolerance.Overall,low temperature stress causes morphological changes and histological damage in P.esculenta,and hsp70 and hsp90 potentially function in the low temperature adaptability of P.esculenta.Our results provide new insights into the adaptive strategies of P.esculenta under low temperature environments.