The combined impact of mechanical factors on the wall stress of the human ascending aorta – a finite elements study

Background

Biomechanical factors influence stress in the aortic wall. The aim of this study was to assess how the diameter and shape of the vessel, blood pressure and longitudinal systolic aortic stretching (SAS) caused by the contraction of the myocardium influence stress in the aortic wall.

Methods

Three computational models of the non-dilated aorta and aneurysms of the ascending aorta and aortic root were created. Then, finite elements analyses were carried out. The models were subjected to blood pressure (120 mmHg and 160 mmHg) and longitudinal systolic aortic stretching (0 mm, 5 mm, 10 mm and 15 mm). The influence of wall elasticity was examined too.

Results

Blood pressure had a smaller impact on the stress than the SAS. An increase in blood pressure from 120 mmHg to 160 mmHg increased the peak wall stress (PWS) on average by 0.1 MPa in all models. A 5 mm SAS caused a 0.1–0.2 MPa increase in PWS in all the models. The increase in PWS caused by a 10 mm and 15 mm SAS was 0.2 MPa and 0.4 MPa in the non-dilated aorta, 0.2–0.3 MPa and 0.3–0.5 MPa in the aneurysm of the ascending aorta, and 0.1–0.2 MPa and 0.2–0.3 MPa in the aortic root aneurysm model, respectively. The loss of elasticity of the aneurysmal wall resulted in an increase of PWS by 0.1–0.2 MPa.

Conclusions

Aortic geometry, wall stiffness, blood pressure and SAS have an impact on PWS. However, SAS had the biggest impact on wall stress. The results of this study may be useful in future patient-specific computational models used to assess the risk of aortic complications.

     

Di(n-butyl) phthalate has no effect on the rat prepubertal testis despite its estrogenic activity in vitro

The aim of this study was to assess the impact of di(n-butyl) phthalate (DBP) on the rat's prepubertal testis. Male Wistar rats were given daily subcutaneous injections with DBP (20 or 200 μg) or a vehicle from the 5th to the 15th postnatal day (pd). On the 16(th) pd, the rats were euthanized, and the testes were dissected, weighed, and paraffin embedded. The blood was collected to determine the serum levels of testosterone (T), estradiol (E) and FSH. The following parameters were assessed in the testis sections: diameter and length of seminiferous tubules (st), numbers of spermatogonia A + intermediate + B (A/In/B), preleptotene spermatocytes (PL), leptotene + zygotene + pachytene spermatocytes (L/Z/PA) and Sertoli cells per testis, percentage of st containing gonocytes or pachytene spermatocytes or lumen. An estrogenicity in vitro test was performed by means of a transgenic yeast strain expressing human estrogen receptor alpha. At both doses, DBP had no influence on testis and seminal vesicle weight, st diameter and length, number of germ and Sertoli cells per testis, percentage of st containing gonocytes or pachytene spermatocytes or lumen. DBP did not change E, T or FSH serum levels. The in vitro yeast screen showed that DBP was a weak estrogenic compound, approximately six to seven orders of magnitude less potent than 17β-estradiol. In conclusion, exposure of a rat to DBP in doses 100 or 1,000-fold higher than a Tolerable Daily Intake for humans had no effect on its testicular development.     

Kowala Lagerstätte: Late Devonian arthropods and non‐biomineralized algae from Poland

A rich and diverse assemblage of arthropods and non‐biomineralized macroalgae occurs in the Upper Devonian marine deposits of the Holy Cross Mountains, central Poland. The phrase Kowala Lagerstätte is herein proposed for the fossil‐bearing deposits confined to the lower Famennian marly shale and limestone succession of the famous Kowala Quarry. The arthropod fauna is represented by phosphatic exoskeletal remains that still preserve the fine micro‐ornamentation of the cuticle. The fauna includes crustaceans and crustacean‐like taxa such as thylacocephalans, phyllocarids and angustidontids (in order of abundance). The non‐biomineralized algae, represented by at least three morphotypes, occur as carbonaceous compressions of their thalli while still preserving fine details including bundles of thin tubular projections. Although their general appearance is reminiscent of some Early Palaeozoic non‐calcified Dasycladales algae, their true taxonomic position is still uncertain. Lithology, as well as faunal and phytoplankton content point to a pelagic sedimentary environment. Impoverished benthic fauna, sediment lamination and geochemical signatures indicate at least periodic bottom‐water dysoxic to anoxic conditions. Thus, the preservation of arthropod cuticle and non‐calcified algae was primarily governed by oxygen‐deficient bottom waters that prevented bioturbation and scavenging during their burial.     

Polymorphism of the serum proteins of wild pigs

One hunderd and ninety five wild pigs from two different regions of Poland were investigated for transferrin, amylase and ceruloplasmin polymorphism. A new transferrin phenotype Tf PB was detected. This phenotype differed from Tf AB in the electrophoretic mobility of the more anodal transferrin. Tf P is assumed to be the product of a new allele Tf P at the Tf locus. Two amylase phenotypes Am 1–2 and Am 2 were observed. The Am 1 allele was absent from the pigs in the Poznan region. Only one ceruloplasmin phenotype, Cp B, was found.