Bioactive molecules from Nocardia: diversity,bioactivities and biosynthesis

Journal of Industrial Microbiology & Biotechnology - Nocardia spp. are catalase positive, aerobic, and non-motile Gram-positive filamentous bacteria. Many Nocarida spp. have been reported as...     

Hydrodynamic interaction between erythrocytes and leukocytes affects rheology of blood in microvessels

Hydrodynamic interaction between erythrocytes (RBC) and leukocytes (WBC) in a microvessel of size 20-40 micron, typical of a postcapillary venule, is studied using a two-dimensional computational model. The model is based on immersed boundary method, and it takes into consideration the particulate nature of blood by explicitly modeling individual blood cell, and cell deformation. Due to their highly flexible nature, RBC drift away from the wall and toward the center of a vessel creating a cell-free layer. It is shown here that the lateral motion of RBC is strongly affected in presence of a WBC, and is dependent on whether the WBC is non-adherent or firmly adhered. When the WBC is non-adherent, some RBC, depending on their initial radial locations and vessel size, may be deflected closer toward the wall, resulting in a decrease in the cell-free layer. The apparent viscosity of the whole blood containing both RBC and WBC is computed, and shown to be much higher than that containing RBC only. The increased viscosity cannot be accounted for by the contribution due to WBC only. This observation is in agreement with a previous in vivo measurement. Here we show that the additional flow resistance is due to the decrease in the cell-free layer resulting from the WBC-RBC interaction. It can be accounted for by a two-layer model of blood when the reduced values of the cell-free layer thickness are used. When the WBC is firmly adhered, RBC easily move away from the wall, and the cell-free layer is not significantly changed. In such cases, the major contribution to whole blood viscosity comes from the WBC alone. The hydrodynamic interaction between WBC and RBC, though it exists, does not contribute significantly when WBC are adhered.     

Time course analysis of gene expression during light-induced photoreceptor cell death and regeneration in albino zebrafish

Constant intense light causes apoptosis of rod and cone photoreceptors in adult albino zebrafish. The photoreceptors subsequently regenerate from proliferating inner nuclear layer (INL) progenitor cells that migrate to the outer nuclear layer (ONL) and differentiate into rods and cones. To identify gene expression changes during this photoreceptor regeneration response, a microarray analysis was performed at five time points during the light treatment. The time course included an early time point during photoreceptor death (16 h), later time points during progenitor cell proliferation and migration (31, 51, and 68 h) and a 96 h time point, which likely corresponds to the initial photoreceptor differentiation. Mean expression values for each gene were calculated at each time point relative to the control (0 h light exposure) and statistical analysis by one-way ANOVA identified 4567 genes exhibiting significant changes in gene expression along the time course. The genes within this data set were clustered based on their temporal expression patterns and proposed functions. Quantitative real-time PCR validated the microarray expression profiles for selected genes, including stat3 whose expression increased markedly during the light exposure. Based on immunoblots, both total and activated Stat3 protein expression also increased during the light treatment. Immunolocalization of Stat3 on retinal tissue sections demonstrated increased expression in photoreceptors and Müller glia by 16 h of light exposure. Some of the Stat3-positive Müller cells expressed PCNA at 31 h, suggesting that Stat3 may play a role in signaling a subset of Müller cells to proliferate during the regeneration response.     

Sensitive and rapid liquid chromatography/tandem mass spectrometric assay for the quantification of chloroquine in dog plasma

A simple, sensitive and rapid liquid chromatography/tandem mass spectrometric (LC-MS/MS) method was developed and validated for quantification of chloroquine, an antimalarial drug, in plasma using its structural analogue, piperazine bis chloroquinoline as internal standard (IS). The method is based on simple protein precipitation with methanol followed by a rapid isocratic elution with 10 mM ammonium acetate buffer/methanol (25/75, v/v, pH 4.6) on Chromolith SpeedROD RP-18e reversed phase chromatographic column and subsequent analysis by mass spectrometry in the multiple reaction monitoring mode (MRM). The precursor to product ion transitions of m/z 320.3-->247.2 and m/z 409.1-->205.2 were used to measure the analyte and the IS, respectively. The assay exhibited a linear dynamic range of 2.0-489.1 ng/mL for chloroquine in dog plasma. The limit of detection (LOD) and lower limit of quantification (LLOQ) were 0.4 and 2.0 ng/mL, respectively in 0.05 mL plasma. Acceptable precision and accuracy were obtained for concentrations over the standard curve range of 2.0-489.1 ng/mL. A run time of 2.0 min for a sample made it possible to achieve a throughput of more than 400 plasma samples analyzed per day. The validated method was successfully used to analyze samples of dog plasma during non-clinical study of chloroquine.     

Translocation of human ribosomal protein S3 to sites of DNA damage is dependant on ERK-mediated phosphorylation following genotoxic stress

Besides its role in translation and ribosome maturation, human ribosomal protein S3 (hS3) is implicated in DNA damage recognition as reflected by its affinity for abasic sites and 7,8-dihydro-8-oxoguanine (8-oxoG) residues in DNA in vitro. Here, we demonstrate that hS3 is capable of carrying out both roles by its ex vivo translocation from the cytoplasm to the nucleus as a consequence of genotoxic stress. The translocation of hS3 is dependent on ERK1/2-mediated phosphorylation of a threonine residue (T42) of hS3. Two different ectopically expressed site-directed mutants of T42 failed to respond to conditions of genotoxic stress, thus providing a link between DNA damage and ERK1/2 dependent phosphorylation of hS3. Lastly, hS3 was traced in exposed cells to its co-localization with 8-oxoG foci, raising the possibility that hS3 is a member of a cellular DNA damage response pathway that results in its interaction with sites of DNA damage.     

Targeting AMPK signaling pathway by natural products for treatment of diabetes mellitus and its complications

Diabetes affects a large population of the world. Lifestyle, obesity, dietary habits, and genetic factors contribute to this metabolic disease. A target pathway to control diabetes is the 5′-adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. AMPK is a heterotrimeric protein with α, β, and γ subunits. In several studies, AMPK activation enhanced glucose uptake into cells and inhibited intracellular glucose production. Impairment of AMPK activity is present in diabetes, according to some studies. Drugs used in the treatment of diabetes, such as metformin, are also known to act through regulation of AMPK. Thus, drugs that activate and regulate AMPK are potential candidates for the treatment of diabetes. In addition, many patients encounter important adverse effects, like hypoglycemia, while using allopathic drugs. As a result, the investigation of plant-derived natural drugs that lack adverse side effects and treat diabetes is necessary. Natural products like berberine, quercetin, resveratrol, and so forth have shown significant potential in regulating and activating the AMPK pathway which can lead to manage diabetes mellitus and its complications.     

Investigation of deleterious effects of nsSNPs in the POT1 gene: a structural genomics-based approach to understand the mechanism of cancer development

Protection of telomere 1 (POT1) is one of the key components of shelterin complex, implicated in maintaining the telomere homeostasis, and thus stability of the eukaryotic genome. A large number of non-synonymous single nucleotide polymorphisms (nsSNPs) in the POT1 gene have been reported to cause varieties of human diseases, including cancer. In recent years, a number of mutations in POT1 has been markedly increased, and interpreting the effect of these large numbers of mutations to understand the mechanism of associated diseases seems impossible using experimental approaches. Herein, we employ varieties of computational methods such as PROVEAN, PolyPhen-2, SIFT, PoPMuSiC, SDM2, STRUM, and MAESTRO to identify the effects of 387 nsSNPs on the structure and function of POT1 protein. We have identified about 183 nsSNPs as deleterious and termed them as “high-confidence nsSNPs.” Distribution of these high-confidence nsSNPs demonstrates that the mutation in oligonucleotide binding domain 1 is highly deleterious (one in every three nsSNPs), and high-confidence nsSNPs show a strong correlation with residue conservation. The structure analysis provides a detailed insights into the structural changes occurred in consequence of conserved mutations which lead to the cancer progression. This study, for the first time, offers a newer prospective on the role of POT1 mutations on the structure, function, and their relation to associated diseases.     

Connectivity and dynamics in the olfactory bulb

Dendrodendritic interactions between excitatory mitral cells and inhibitory granule cells in the olfactory bulb create a dense interaction network, reorganizing sensory representations of odors and, consequently, perception. Large-scale computational models are needed for revealing how the collective behavior of this network emerges from its global architecture. We propose an approach where we summarize anatomical information through dendritic geometry and density distributions which we use to calculate the connection probability between mitral and granule cells, while capturing activity patterns of each cell type in the neural dynamical systems theory of Izhikevich. In this way, we generate an efficient, anatomically and physiologically realistic large-scale model of the olfactory bulb network. Our model reproduces known connectivity between sister vs. non-sister mitral cells; measured patterns of lateral inhibition; and theta, beta, and gamma oscillations. The model in turn predicts testable relationships between network structure and several functional properties, including lateral inhibition, odor pattern decorrelation, and LFP oscillation frequency. We use the model to explore the influence of cortex on the olfactory bulb, demonstrating possible mechanisms by which cortical feedback to mitral cells or granule cells can influence bulbar activity, as well as how neurogenesis can improve bulbar decorrelation without requiring cell death. Our methodology provides a tractable tool for other researchers.