Aortic valve stenosis: persistence of infective agents or noninfective inflammatory process?]

The probable risk factors leading to aortic valve calcification are not clearly defined. The cross-sectional study of 85 patients with vascular and valvular calcification was performed. Correlations between the immune tests and aortic stenosis severity were investigated. The predictors of aortic valve calcification were probably C-reactive protein and interleukin-6. The predictors of aortic stenosis progression were interleukin-8, antibodies of Chlamydia pneumoniae and cytomegalovirus, and dysregulation of complement's components. Implication of immune reactivity could influence aortic valve calcification.     

Aortic valve leaflet mechanical properties facilitate diastolic valve function

This work was concerned with the numerical simulation of the behaviour of aortic valves whose material can be modelled as non-linear elastic anisotropic. Linear elastic models for the valve leaflets with parameters used in previous studies were compared with hyperelastic models, incorporating leaflet anisotropy with pronounced stiffness in the circumferential direction through a transverse isotropic model. The parameters for the hyperelastic models were obtained from fits to results of orthogonal uniaxial tensile tests on porcine aortic valve leaflets. The computational results indicated the significant impact of transverse isotropy and hyperelastic effects on leaflet mechanics; in particular, increased coaptation with peak values of stress and strain in the elastic limit. The alignment of maximum principal stresses in all models follows approximately the coarse collagen fibre distribution found in aortic valve leaflets. The non-linear elastic leaflets also demonstrated more evenly distributed stress and strain which appears relevant to long-term scaffold stability and mechanotransduction.     

Aortic valvuloplasties: treatment of calcified aortic stenosis in elderly subjects

Since September 1985, transluminal balloon catheter aortic valvuloplasty has been developed in France (Cribier and al.) and all around the world. Indications are still limited, in almost all catheterization laboratories, to elderly patients, with Monckeberg's disease, and with a very high operative risk. Immediately after aortic valvuloplasty, there is a moderate but a significant increase in valve area, without serious complications. Subjective improvement is often spectacular during few months after the valvuloplasty. In long-term evolution, there is sometimes a symptomatic restenosis which require a new valvuloplasty. So, if percutaneous valvuloplasty is efficacy in aortic stenosis in the elderly, long-term evaluation of this new technique is necessary.     

Modeling feature-based attention as an active top-down inference process

Vision is a crucial sensor. It provides a very rich collection of information about our environment. The difficulty in vision arises, since this information is not obvious in the image, it has to be constructed. Wheres earlier approaches have favored a bottom-up approach, which maps the image onto an internal representation of the world, more recent approaches search for alternatives and develop frameworks which make use of top-down connections. In these approaches vision is inherently a constructive process which makes use of a priory information. Following this line of research, a model of primate object perception is presented and used to simulate an object detection task in natural scenes. The model predicts that early responses in extrastriate visual areas are modulated by the visual goal.     

A family with congenital pulmonary valve stenosis

Summary Congenital pulmonary stenosis has been found in three successive generations of one family. No members of the family had any extra-cardiac malformations or abnormal facial features. The pedigree is compatible with an autosomal dominant made of inheritance.

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Zusammenfassung Kongenitale Pulmonalstenose wurde in drei aufeinanderfolgenden Generationen einer Familie festgestellt. Kein Mitglied der Familie hat irgendwelche extrakardialen Mißbildungen oder abnorme Gesichtsbildung. Die Verteilung der Merkmalträger ist mit autosomal dominanter Vererbung in Übereinstimmung.

     

Aortic valve replacement in a patient with severe hemophilia

Hemophilia A is an inherited bleeding disorder characterized by factor VIII deficiency. The basis for insufficient hemostasis lies within inadequate amplification of factor Xa production with the undersupplied factor VIII. We report on a young patient with critical aortic stenosis bearing all the clinical stigmata of severe hemophilia, in whom aortic valve replacement was performed with a tissue valve in order to avoid the need for long term anticoagulation.     

Aortic valve leaflet wall shear stress characterization revisited: impact of coronary flow

Computational characterizations of aortic valve hemodynamics have typically discarded the effects of coronary flow. The objective of this study was to complement our previous fluid–structure interaction aortic valve model with a physiologic coronary circulation model to quantify the impact of coronary flow on aortic sinus hemodynamics and leaflet wall shear stress (WSS). Coronary flow suppressed vortex development in the two coronary sinuses and altered WSS magnitude and directionality on the three leaflets, with the most substantial differences occurring in the belly and tip regions.     

Cryo-EM reveals an active role for aminoacyl-tRNA in the accommodation process

During the elongation cycle of protein biosynthesis, the specific amino acid coded for by the mRNA is delivered by a complex that is comprised of the cognate aminoacyl-tRNA, elongation factor Tu and GTP. As this ternary complex binds to the ribosome, the anticodon end of the tRNA reaches the decoding center in the 30S subunit. Here we present the cryo- electron microscopy (EM) study of an Escherichia coli 70S ribosome-bound ternary complex stalled with an antibiotic, kirromycin. In the cryo-EM map the anticodon arm of the tRNA presents a new conformation that appears to facilitate the initial codon-anticodon interaction. Furthermore, the elbow region of the tRNA is seen to contact the GTPase-associated center on the 50S subunit of the ribosome, suggesting an active role of the tRNA in the transmission of the signal prompting the GTP hydrolysis upon codon recognition.     

Silicon uptake and transport is an active process in Cucumis sativus

Cucumis sativus is a species known to accumulate high levels of silicon (Si) in the tops, though the mechanism for its high Si uptake is little understood. In a series of hydroponic experiments, we examined uptake and xylem loading of Si in C. sativus along with Vicia faba at three levels of Si (0.085, 0.17 and 1.70 mm). Measured Si uptake in C. sativus was more than twice as high as calculated from the rate of transpiration assuming no discrimination between silicic acid and water in uptake. Measured Si uptake in V. faba, however, was significantly lower than the calculated uptake. Concentration of Si in xylem exudates was several-fold higher in C. sativus, but was significantly lower in V. faba compared with the Si concentration in external solutions, regardless of Si levels. Silicon uptake was strongly inhibited by low temperature and 2,4-dinitrophenol, a metabolic inhibitor, in C. sativus but not in V. faba. It can be concluded that Si uptake and transport in C. sativus is active and independent of external Si concentrations, in contrast to the process in V. faba.