An integrated fluid–structure interaction and thrombosis model for type B aortic dissection

False lumen thrombosis (FLT) in type B aortic dissection has been associated with the progression of dissection and treatment outcome. Existing computational models mostly assume rigid wall behavior which ignores the effect of flap motion on flow and thrombus formation within the FL. In this study, we have combined a fully coupled fluid–structure interaction (FSI) approach with a shear-driven thrombosis model described by a series of convection–diffusion reaction equations. The integrated FSI-thrombosis model has been applied to an idealized dissection geometry to investigate the interaction between vessel wall motion and growing thrombus. Our simulation results show that wall compliance and flap motion can influence the progression of FLT. The main difference between the rigid and FSI models is the continuous development of vortices near the tears caused by drastic flap motion up to 4.45 mm. Flap-induced high shear stress and shear rates around tears help to transport activated platelets further to the neighboring region, thus speeding up thrombus formation during the accelerated phase in the FSI models. Reducing flap mobility by increasing the Young’s modulus of the flap slows down the thrombus growth. Compared to the rigid model, the predicted thrombus volume is 25% larger using the FSI-thrombosis model with a relatively mobile flap. Furthermore, our FSI-thrombosis model can capture the gradual effect of thrombus growth on the flow field, leading to flow obstruction in the FL, increased blood viscosity and reduced flap motion. This model is a step closer toward simulating realistic thrombus growth in aortic dissection, by taking into account the effect of intimal flap and vessel wall motion.

     

Malassezia Species: A Rare Cause of Invasive Fungal Infections in Immunocompromised Patients

The members of Malassezia species, which may cause skin disorders in healthy individuals, are associated with both cutaneous and systemic disorders in immunocompromised patients. These disorders include folliculitis, seborrheic dermatitis, catheter-related fungemia, and deeply invasive infections. This review examines not only the risk factors and pathogenesis of this rare fungal infection but also the clinical manifestations, diagnosis, and treatment of Malassezia infections in immunocompromised patients. Reports from several series of immunocompromised patients have shown low mortality rates with appropriate treatment.     

On the phytoscreening potential of insect-induced plant galls

Plant and Soil - Tussock microhabitat is a universal phenomenon in wetlands, where soil and plant properties differ from their surrounding lawns. This study aims to investigate the differences of...     

Quasi-Monopolar Stimulation: A Novel Electrode Design Configuration for Performance Optimization of a Retinal Neuroprosthesis

In retinal neuroprostheses, spatial interaction between electric fields from various electrodes – electric crosstalk – may occur in multielectrode arrays during simultaneous stimulation of the retina. Depending on the electrode design and placement, this crosstalk can either enhance or degrade the functional characteristics of a visual prosthesis. To optimize the device performance, a balance must be satisfied between the constructive interference of crosstalk on dynamic range and power consumption and its negative effect on artificial visual acuity. In the present computational modeling study, we have examined the trade-off in these positive and negative effects using a range of currently available electrode array configurations, compared to a recently proposed stimulation strategy – the quasi monopolar (QMP) configuration – in which the return current is shared between local bipolar guards and a distant monopolar electrode. We evaluate the performance of the QMP configuration with respect to the implantation site and electrode geometry parameters. Our simulation results demonstrate that the beneficial effects of QMP are only significant at electrode-to-cell distances greater than the electrode dimensions. Possessing a relatively lower activation threshold, QMP was found to be superior to the bipolar configuration in terms of providing a relatively higher visual acuity. However, the threshold for QMP was more sensitive to the topological location of the electrode in the array, which may need to be considered when programming the manner in which electrode are simultaneously activated. This drawback can be offset with a wider dynamic range and lower power consumption of QMP. Furthermore, the ratio of monopolar return current to total return can be used to adjust the functional performance of QMP for a given implantation site and electrode parameters. We conclude that the QMP configuration can be used to improve visual information-to-stimulation mapping in a visual prosthesis, while maintaining low power consumption.     

Early Miocene herpetofaunas from the Greek localities of Aliveri and Karydia – bridging a gap in the knowledge of amphibians and reptiles from the early Neogene of southeastern Europe

Abstract

We here describe new remains of amphibians and reptiles from the early Miocene (MN 4) of two different Greek localities, Aliveri and Karydia. The newly described material consists of urodelans, alytids, indeterminate anurans, turtles, crocodylians, lacertids, indeterminate scincomorphs, anguids, colubrids, viperids, and indeterminate snakes. The presence of the frog Latonia cf. gigantea in Greece is documented for the first time. Additionally, the presence of viperids in Aliveri implies a much wider distribution for these snakes during the early Miocene of Europe. Of special interest is the presence of a peculiar colubrid that seems to possess a hitherto unknown vertebral structure, which is herein defined as the ‘paracentral ridge’. Although incomplete, the new material has important taxonomic and biogeographic implications, as it enhances our understanding of southeastern European herpetofaunas from the early Miocene, a time period that was characterised by major dispersal and extinction events and climatic change that affected the whole continent.     

Stereodesign of chiral para-substituted calix[4]arenes

According to the hypothesis that the chirality of molecule hosts is a cause of their enantioselectivity, the chirality of para-substituted calix[4]arenes was analyzed quantitatively. The relationship between types of para-substituents and the dissymmetry of the 2D (two-dimensional) entrance into the cavity and the whole 3D (three-dimensional) cavity of calix[4]arenes was studied by means of the enantiomer dissimilarity factor (EDF) method for quantitative evaluation of molecular chirality. The design of the most chiral, and probably enantioselective, para-substituted calix[4]arenes was planned such that all four substituents should be different and the two largest should be near each other (adjacent). It was, on the other hand, shown that the 2D chiral entrance determines chirality of the whole 3D structures of these molecules. This phenomenon is interpreted as an example of the chirality transition from 2D into 3D space.Electronic Supplementary Material available.     

DeltaF508 mutation results in impaired gastric acid secretion

The cystic fibrosis transmembrane conductance regulator (CFTR) is recognized as a multifunctional protein that is involved in Cl(-) secretion, as well as acting as a regulatory protein. In order for acid secretion to take place a complex interaction of transport proteins and channels must occur at the apical pole of the parietal cell. Included in this process is at least one K(+) and Cl(-) channel, allowing for both recycling of K(+) for the H,K-ATPase, and Cl(-) secretion, necessary for the generation of concentrated HCl in the gastric gland lumen. We have previously shown that an ATP-sensitive potassium channel (K(ATP)) is expressed in parietal cells. In the present study we measured secretagogue-induced acid secretion from wild-type and DeltaF508-deficient mice in isolated gastric glands and whole stomach preparations. Secretagogue-induced acid secretion in wild-type mouse gastric glands could be significantly reduced with either glibenclamide or the specific inhibitor CFTR-inh172. In DeltaF508-deficient mice, however, histamine-induced acid secretion was significantly less than in wild-type mice. Furthermore, immunofluorescent localization of sulfonylurea 1 and 2 failed to show expression of a sulfonylurea receptor in the parietal cell, thus further implicating CFTR as the ATP-binding cassette transporter associated with the K(ATP) channels. These results demonstrate a regulatory role for the CFTR protein in normal gastric acid secretion.     

Rapid identification of malaria vaccine candidates based on alpha-helical coiled coil protein motif

To identify malaria antigens for vaccine development, we selected alpha-helical coiled coil domains of proteins predicted to be present in the parasite erythrocytic stage. The corresponding synthetic peptides are expected to mimic structurally "native" epitopes. Indeed the 95 chemically synthesized peptides were all specifically recognized by human immune sera, though at various prevalence. Peptide specific antibodies were obtained both by affinity-purification from malaria immune sera and by immunization of mice. These antibodies did not show significant cross reactions, i.e., they were specific for the original peptide, reacted with native parasite proteins in infected erythrocytes and several were active in inhibiting in vitro parasite growth. Circular dichroism studies indicated that the selected peptides assumed partial or high alpha-helical content. Thus, we demonstrate that the bioinformatics/chemical synthesis approach described here can lead to the rapid identification of molecules which target biologically active antibodies, thus identifying suitable vaccine candidates. This strategy can be, in principle, extended to vaccine discovery in a wide range of other pathogens.     

Musteloids and feloids (Mammalia, Carnivora) from the late Miocene locality of Pikermi (Attica, Greece)

Some relatively rare carnivore remains from Pikermi are studied. The present specimens include Simocyon primigenius(ROTH and WAGNER, 1854), Promeles palaeatticus(WEITHOFER, 1888), Martes woodwardiPILGRIM, 1931, Felis atticaWAGNER, 1857 and Machairodus giganteus(WAGNER, 1848), as well as some postcranial remains that resemble Enhydriodon? latipesPILGRIM, 1931 and are assigned to Mustelidae gen. et spec. indet. Some of these species were not known until now but from their holotypes as M. woodwardi and E.? latipes. Other species such as F. attica and M. giganteus are better known but from relatively scant material. Since the material of the earlier mentioned species comes from Pikermi, their type locality, it is of especial importance and improves our knowledge for the Pikermi carnivores and their relationships to other species. In some cases where the material comes from ossiferous blocks, the accompanying faunal context is discussed.