Effects of intima stiffness and plaque morphology on peak cap stress

Background  

Rupture of the cap of a vulnerable plaque present in a coronary vessel may cause myocardial infarction and death. Cap rupture occurs when the peak cap stress exceeds the cap strength. The mechanical stress within a cap depends on the plaque morphology and the material characteristics of the plaque components. A parametric study was conducted to assess the effect of intima stiffness and plaque morphology on peak cap stress.     

A low-cost, portable generic biotoxicity assay for environmental monitoring applications

Fish chromatophores have been shown to be promising biosensors for the detection of hostile agents in the environment. However, state-of-art methods for such applications are still based on extensive use of data/signal processing, in conjunction with need for a skilled human observer to carry out the detection. As a result, conventional methods are complex, costly and cumbersome rendering them useless for field applications requiring low-cost portable solutions capable of fast detection. A new technique is proposed based on the popular scheme of observing the aggregation response in chromatophores for detection of toxicity, and a solution using optical detection and electronic processing is outlined. This scheme has the advantage of being low in cost while providing simple, fast and reliable detection.     

Analysis of Methylglyoxal Metabolism in CHO Cells Grown in Culture

Recent evidence suggests that several unknown or ill-characterized factors strongly influence cell growth and function in culture. Isolating these factors is necessary in order to maximize culture productivities. Methylglyoxal (MG), a potent protein and nucleic acid modifying agent, has been identified as a player in the signaling pathways associated with cell death and is known to be detrimental to cultured cells. This compound is produced in all mammalian systems by spontaneous phosphate elimination from glycolytic pathway intermediates. A kinetic model that qualitatively describes the cellular distribution of protein-associated MG in the absence of enzymatic adduct formation predicted far lower levels of reversibly bound MG than measured in cultured CHO cells. This suggests that the targeted modification of proteins through enzymatically mediated mechanisms is a significant sink for cellular methylglyoxal. The model was validated with measurements of carbon flux through the glyoxalase pathway to d-lactic acid, a unique end product of MG metabolism in mammalian systems. Fluxes to d-lactic acid of up to 16.8 mmol ml-packed cells⁻¹ day⁻¹ were measured with CHO cells grown in batch culture or 100-fold more than found in normal tissues.     

Enhanced performance and mechanism study of microbial electrolysis cells using Fe nanoparticle-decorated anodes

Anode properties are critical for the performance of microbial electrolysis cells (MECs). In the present study, Fe nanoparticle-modified graphite disks were used as anodes to investigate the effects of nanoparticles on the performance of Shewanella oneidensis MR-1 in MECs. Results demonstrated that the average current densities produced with Fe nanoparticle-decorated anodes up to 5.89-fold higher than plain graphite anodes. Whole genome microarray analysis of the gene expression showed that genes encoding biofilm formation were significantly up-regulated as a response to nanoparticle-decorated anodes. Increased expression of genes related to nanowires, flavins, and c-type cytochromes indicates that enhanced mechanisms of electron transfer to the anode may also have contributed to the observed increases in current density. The majority of the remaining differentially expressed genes associated with electron transport and anaerobic metabolism demonstrate a systemic response to increased power loads.     

Stimulation of insulin release by glyceraldehyde may not be similar to glucose

Glyceraldehyde (GA) has been used to study insulin secretion for decades and it is widely assumed that beta-cell metabolism of GA after its phosphorylation by triokinase is similar to metabolism of glucose; that is metabolism through distal glycolysis and oxidation in mitochondria. New data supported by existing information indicate that this is true for only a small amount of GA's metabolism and also suggest why GA is toxic. GA is metabolized at 10-20% the rate of glucose in pancreatic islets, even though GA is a more potent insulin secretagogue. GA also inhibits glucose metabolism to CO2 out of proportion to its ability to replace glucose as a fuel. This study is the first to measure methylglyoxal (MG) in beta-cells and shows that GA causes large increases in MG in INS-1 cells and d-lactate in islets but MG does not mediate GA-induced insulin release. GA severely lowers NAD(P) and increases NAD(P)H in islets. High NADH combined with GA's metabolism to CO2 may initially hyperstimulate insulin release, but a low cytosolic NAD/NADH ratio will block glycolysis at glyceraldehyde phosphate (GAP) dehydrogenase and divert GAP toward MG and D-lactate formation. Accumulation of D-lactate and 1-phosphoglycerate may explain why GA makes the beta-cell acidic. Reduction of both GA and MG by abundant beta-cell aldehyde reductases will lower the cytosolic NADPH/NADP ratio, which is normally high.     

Simulation of stent deployment in a realistic human coronary artery

Background  

The process of restenosis after a stenting procedure is related to local biomechanical environment. Arterial wall stresses caused by the interaction of the stent with the vascular wall and possibly stress induced stent strut fracture are two important parameters. The knowledge of these parameters after stent deployment in a patient derived 3D reconstruction of a diseased coronary artery might give insights in the understanding of the process of restenosis.     

Microsatellite evolution in congeneric mammals: domestic and bighorn sheep

We compared genotypes at eight (AC)n microsatellite loci in domestic sheep (Ovis aries) and wild Rocky Mountain bighorn sheep (O. canadensis). The domestic sheep had greater genetic variation, higher allele-size variances, and larger allele sizes than the wild sheep. Accumulating evidence from higher taxonomic comparisons shows that these parameters are biased if microsatellite loci are selected in one taxon and used in another. Our results demonstrate similar biases between congeneric species. We compared standard measures of genetic variation, differentiation, and distance within and between species (H, D, FST) to newer measures based on allele-size variance (SW, SB, RST). The size-based distances better detected species-level divergence, but standard measures better distinguished allopatric populations. Empirical calibration of these measures at the subspecies level is needed to establish their useful ranges.