Influence of inlet boundary conditions on the local haemodynamics of intracranial aneurysms

Haemodynamics is believed to play an important role in the initiation, growth and rupture of intracranial aneurysms. In this context, computational haemodynamics has been extensively used in an effort to establish correlations between flow variables and clinical outcome. It is common practice in the application of Dirichlet boundary conditions at domain inlets to specify transient velocities as either a flat (plug) profile or a spatially developed profile based on Womersley's analytical solution. This paper provides comparative haemodynamics measures for three typical cerebral aneurysms.

Three dimentional rotational angiography images of aneurysms at three common locations, viz. basilar artery tip, internal carotid artery and middle cerebral artery were obtained. The computational tools being developed in the European project @neurIST were used to reconstruct the fluid domains and solve the unsteady Navier–Stokes equations, using in turn Womersley and plug-flow inlet velocity profiles. The effects of these assumptions were analysed and compared in terms of relevant haemodynamic variables within the aneurismal sac. For the aneurysm at the basilar tip geometries with different extensions of the afferent vasculature were considered to study the plausibility of a fully-developed axial flow at the inlet boundaries.

The study shows that assumptions made on the velocity profile while specifying inlet boundary conditions have little influence on the local haemodynamics in the aneurysm, provided that a sufficient extension of the afferent vasculature is considered and that geometry is the primary determinant of the flow field within the aneurismal sac. For real geometries the Womersley profile is at best an unnecessary over-complication, and may even be worse than the plug profile in some anatomical locations (e.g. basilar confluence).     

Immobilization of goat brain aminopeptidase B in calcium alginate beads

Aminopeptidase B, an arginyl aminopeptidase, was purified from goat brain with a purification factor of ～280 and a yield of 2.7%. It was entrapped in calcium alginate together with bovine serum albumin. The optimal conditions for immobilization for maximum activity yield were 1% CaCl₂ and 2.5% alginate. The immobilized enzyme retained ～62% of its initial activity and could be used for five successive batch reactions with retention of 30% of the initial activity. The pH and temperature optima of the free and immobilized enzyme were pH 7.4, 45°C and pH 7.8, 50°C respectively, while the pH and thermal stability as well as the stability of the enzyme in organic solvents were improved significantly after entrapment. The K_m value for the immobilized enzyme was about twofold higher than that of the soluble enzyme. Because of this increased stability, the immobilized enzyme may be useful in the meat processing industry.     

The evolution of an ideal stent design and its impact on the aortic endothelium during and after percutaneous replacement

Vascular support structures are important devices for treating valve stenosis. A large population of patients is treated for valvular disease and the preferred mode of treatment is percutaneous valve replacement. Stent devices are proving to be an improved technology in minimally invasive cardiac surgery. This new technology provides highly effective results at minimal cost and with a short duration of hospitalisation. Stents as a supporting structure for tissue valves have evolved over the years into remarkably useful and effective devices. During this process, a number of specific designs have come and gone, and a few have remained. Many design changes were successful, and many were not. This article describes the merits and demerits of various stent designs and details the specific reasons why a particular novel design is expected to be the most suitable implant during and after percutaneous aortic valve replacement.     

Characterization of Solanum tuberosum Multicystatin and the Significance of Core Domains

Potato (Solanum tuberosum) multicystatin (PMC) is a unique cystatin composed of eight repeating units, each capable of inhibiting cysteine proteases. PMC is a composite of several cystatins linked by trypsin-sensitive (serine protease) domains and undergoes transitions between soluble and crystalline forms. However, the significance and the regulatory mechanism or mechanisms governing these transitions are not clearly established. Here, we report the 2.2-Å crystal structure of the trypsin-resistant PMC core consisting of the fifth, sixth, and seventh domains. The observed interdomain interaction explains PMC’s resistance to trypsin and pH-dependent solubility/aggregation. Under acidic pH, weakening of the interdomain interactions exposes individual domains, resulting in not only depolymerization of the crystalline form but also exposure of cystatin domains for inhibition of cysteine proteases. This in turn allows serine protease–mediated fragmentation of PMC, producing ∼10-kD domains with intact inhibitory capacity and faster diffusion, thus enhancing PMC’s inhibitory ability toward cysteine proteases. The crystal structure, light-scattering experiments, isothermal titration calorimetry, and site-directed mutagenesis confirmed the critical role of pH and N-terminal residues in these dynamic transitions between monomer/polymer of PMC. Our data support a notion that the pH-dependent structural regulation of PMC has defense-related implications in tuber physiology via its ability to regulate protein catabolism.     

Determination of Mass Transfer Coefficients for A Mixture of Compost,Sugarcane Bagasse,and Granulated Activated Carbon as Packing Medium in Biofilter

ABSTRACT

A laboratory-scale biofilter unit packed with a mixture of compost, sugarcane bagasse, and granulated activated carbon (GAC) in the ratio of 55:30:15 by weight was used for a biofiltration study of air stream containing benzene, toluene, ethylbenzene, and o-xylene (BTEX). The effect of superficial velocity on mass transfer coefficient for the packing was studied by maintaining gas flow rates of 3, 4, 5, 6, and 8 L min^?1 for inlet concentrations of 0.1, 0.4, and 0.8 g m^?3 for each of benzene, toluene, ethylbenzene, and o-xylene. The maximum elimination capacity was found to be 20.92, 22.72, 20.73, and 18.94 g m^?3 h^?1 for BTEX, respectively, for stated flow rates. Removal efficiency of BTEX decreased from 99% to 71% for increasing inlet concentration from 0.1 to 0.8 g m^?3. Gas film mass transfer coefficient predicted by modified Onda's equation was within ±10% of the experimental values.     

Computational Analysis of C-Reactive Protein for Assessment of Molecular Dynamics and Interaction Properties

Serum C-reactive protein (CRP) is used as a marker of inflammation in several diseases including autoimmune disease and cardiovascular disease. CRP, a member of the pentraxin family, is comprised of five identical subunits. CRP has diverse ligand-binding properties which depend upon different structural states of CRP. However, little is known about the molecular dynamics and interaction properties of CRP. In this study, we used SAPS, SCRATCH protein predictor, PDBsum, ConSurf, ProtScale, Drawhca, ASAView, SCide and SRide server and performed comprehensive analyses of molecular dynamics, protein–protein and residue–residue interactions of CRP. We used 1GNH.pdb file for the crystal structure of human CRP which generated two pentamers (ABCDE and FGHIJ). The number of residues involved in residue–residue interactions between A–B, B–C, C–D, D–E, F–G, G–H, H–I, I–J, A–E and F–J subunits were 12, 11, 10, 11, 12, 11, 10, 11, 10 and 10, respectively. Fifteen antiparallel β sheets were involved in β-sheet topology, and five β hairpins were involved in forming the secondary structure. Analysis of hydrophobic segment distribution revealed deviations in surface hydrophobicity at different cavities present in CRP. Approximately 33 % of all residues were involved in the stabilization centers. We show that the bioinformatics tools can provide a rapid method to predict molecular dynamics and interaction properties of CRP. Our prediction of molecular dynamics and interaction properties of CRP combined with the modeling data based on the known 3D structure of CRP is helpful in designing stable forms of CRP mutants for structure–function studies of CRP and may facilitate in silico drug design for therapeutic targeting of CRP.     

Inactivation of ntcA gene revealed differential proteome expression and induction of some hypothetical proteins in the cyanobacterium Anabaena sp. PCC 7120 and its derivative ntcA mutant under different levels of calcium

Abstract

Calcium is an important macronutrient for both prokaryotes and eukaryotes. It acts as an important second messenger mediating rapid response to environmental conditions. The present investigation deals with proteome profiling of Anabaena 7120 and its derivative ntcA mutant in response to varied calcium doses (0, 1 and 10?mM CaCl₂). Concentration of 1?mM CaCl₂ salt was the optimum concentration whereas 10?mM CaCl₂ was the inhibitory concentration for both the wild type and mutant strains. The results showed highly significant alteration in terms of protein abundance and differential response related to key processes of photosynthesis, energy and metabolism, nitrogen metabolism, oxidative and antioxidative defence, transport and signalling and fatty acid metabolism. In the wild type proteins related to photosynthesis and nitrogen metabolism showed upregulation at 1?mM CaCl₂ concentration while antioxidative defence related proteins were down-regulated. In the mutant however, proteins related to photosynthesis and nitrogen metabolism exhibited severe down-regulation. Some hypothetical proteins were also realized during proteome analysis. Overall, our results suggested that NtcA have a potential role in regulation of calcium ion dependent key processes underlying in various metabolic activities of the cyanobacterium Anabaena 7120.     

Embryological studies on Indian Taraxacum Weber. Embryo sac,endosperm and embryo

Abstract

The present paper deals with the embryological studies of ten species of Taraxacum, out of which nine polyploid species are apomictic and one diploid species T. wallichii shows normal sexual behaviour. Occasional formation of normal megaspore tetrads and triads are observed in tetraploid and triploid species.

Autonomous development of endosperm from the secondary nucleus seems to be the rule. The growth of endosperm is relatively slow.