A genetic analysis of various functions of the TyrR protein of Escherichia coli.

The TyrR protein is involved in both repression and activation of the genes of the TyrR regulon. Correction of an error in a previously published sequence has revealed a Cro-like helix-turn-helix DNA-binding domain near the carboxyl terminus. Site-directed mutagenesis in this region has generated a number of mutants that can no longer repress or activate. Deletions of amino acid residues 5 to 42 produced a protein that could repress but not activate. The central domain of TyrR contains an ATP-binding site and is homologous with the NtrC family of activator proteins. A mutation to site A of the ATP-binding site and other mutations in this region affect tyrosine-mediated repression but do not prevent activation or phenylalanine-mediated repression of aroG.     

Screening of marine actinobacteria for amylase enzymes inhibitors

Amylase inhibitor producing actinobacteria were isolated and characterized from terrestrial environment and there is no much report found from marine environment, hence in the present study, 17 strains isolated from the rhizosphere sediments of mangroves were tested for their amylase inhibition ability. Seawater requirement test for the growth of actinobacteria found that the strains SSR-3, SSR-12 and SSR-16 requires at least 50% and SSR-6 requires at least 25% seawater for their growth. The inhibition activity of both prokaryotic and eukaryotic amylase was tested by using Bacillus subtilis and Aspergillus niger. The maximum amylase activity (40mm) produced by the A. niger was taken as positive control, when the test actinobacteria strains grown in the medium they inhibited amylase activity and was evidenced by the reduction in inhibition zone (14–37 mm) similarly the amylase produced by the Bacillus subtilis was also recorded maximum (35 mm) amylase activity and was taken as positive control, and the test atinobacterial strains reduced enzyme action(12–33 mm) it varied levals. This indicates that the actinobacteria strains were controlled amylase enzyme activity in both the cases. The strain SSR-10 was highly effective and SSR-8 was less effective in inhibiting eukaryotic amylase produced by A. niger. The strain SSR-2 was effective and SSR-6 showed very less effect in inhibiting the prokaryotic amylase produced by the B subtilis.     

Disrupted-In-Schizophrenia 1 regulates integration of newly generated neurons in the adult brain

Adult neurogenesis occurs throughout life in discrete regions of the adult mammalian brain. Little is known about the mechanism governing the sequential developmental process that leads to integration of new neurons from adult neural stem cells into the existing circuitry. Here, we investigated roles of Disrupted-In-Schizophrenia 1 (DISC1), a schizophrenia susceptibility gene, in adult hippocampal neurogenesis. Unexpectedly, downregulation of DISC1 leads to accelerated neuronal integration, resulting in aberrant morphological development and mispositioning of new dentate granule cells in a cell-autonomous fashion. Functionally, newborn neurons with DISC1 knockdown exhibit enhanced excitability and accelerated dendritic development and synapse formation. Furthermore, DISC1 cooperates with its binding partner NDEL1 in regulating adult neurogenesis. Taken together, our study identifies DISC1 as a key regulator that orchestrates the tempo of functional neuronal integration in the adult brain and demonstrates essential roles of a susceptibility gene for major mental illness in neuronal development, including adult neurogenesis.     

Low frequency and low intensity pulsed electromagnetic field exerts its antiinflammatory effect through restoration of plasma membrane calcium ATPase activity

Rheumatoid arthritis (RA) is a chronic inflammatory disorder affecting 1% of the population worldwide. Pulsed electromagnetic field (PEMF) has a number of well-documented physiological effects on cells and tissues including antiinflammatory effect. This study aims to explore the antiinflammatory effect of PEMF and its possible mechanism of action in amelioration of adjuvant induced arthritis (AIA). Arthritis was induced by a single intradermal injection of heat killed Mycobacterium tuberculosis at a concentration of 500 μg in 0.1 ml of paraffin oil into the right hind paw of rats. The arthritic animals showed a biphasic response regarding changes in the paw edema volume. During the chronic phase of the disease, arthritic animals showed an elevated level of lipid peroxides and depletion of antioxidant enzymes with significant radiological and histological changes. Besides, plasma membrane Ca²⁺ ATPase (PMCA) activity was inhibited while intracellular Ca²⁺ level as well as prostaglandin E₂ levels was noticed to be elevated in blood lymphocytes of arthritic rats. Exposure of arthritic rats to PEMF at 5 Hz × 4 μT × 90 min, produced significant antiexudative effect resulting in the restoration of the altered parameters. The antiinflammatory effect could be partially mediated through the stabilizing action of PEMF on membranes as reflected by the restoration of PMCA and intracellular Ca²⁺ levels in blood lymphocytes subsequently inhibiting PGE₂ biosynthesis. The results of this study indicated that PEMF could be developed as a potential therapy for RA in human beings.     

Effect of prostaglandins A1, A2, B1, B2, E2 and F2α on human umbilical cord vessels

The effect of six naturally occurring prostaglandins on isolated umbilical arteries and veins has been studied. All six prostaglandins had a constricting effect on the umbilical vessels. On the umbilical artery preparations the potencies in decreasing order were A₂>B₂>F_2α>B₁>E₂>A₁. Prostaglandin B₂ was more potent than PGA₂ on the umbilical vein. Polyphloretin phosphate (PPP) antagonised the constricting effect of all six prostaglandins without altering responses to 5-hydroxytryptamine.     

Neoxanthin prevents H2O2-induced cytotoxicity in HepG2 cells by activating endogenous antioxidant signals and suppressing apoptosis signals

Molecular Biology Reports - The liver has a solid inbuilt antioxidant defense system to regulate oxidative stress. However, exposure to an excessive level of ROS causes liver injury. This study...     

QSAR studies on the human sirtuin 2 inhibition by non-covalent 7,5,2-anilinobenzamide derivatives

Abstract

Sirtuin 2 is a key enzyme in gene expression regulation that is often associated with tumor proliferation control and therefore is a relevant anticancer drug target. Anilinobenzamide derivatives have been discussed as selective sirtuin 2 inhibitors and can be developed further. In the present study, hologram and three-dimensional quantitative structure–activity relationship (HQSAR and 3D-QSAR) analyses were employed for determining structural contributions of a compound series containing human sirtuin-2-selective inhibitors that were then correlated with structural data from the literature. The final QSAR models were robust and predictive according to statistical validation (q² and r²_pred values higher than 0.85 and 0.75, respectively) and could be employed further to generate fragment contribution and contour maps. 3D-QSAR models together with information about the chemical properties of sirtuin 2 inhibitors can be useful for designing novel bioactive ligands.

Communicated by Ramaswamy H. Sarma     

Immunocytochemical localization of alpha-protein kinase C in rat pancreatic beta-cells during glucose-induced insulin secretion

To investigate the role of protein kinase C (PKC) in the regulation of insulin secretion, we visualized changes in the intracellular localization of alpha-PKC in fixed beta-cells from both isolated rat pancreatic islets and the pancreas of awake unstressed rats during glucose-induced insulin secretion. Isolated, perifused rat islets were fixed in 4% paraformaldehyde, detergent permeabilized, and labeled with a mAb specific for alpha-PKC. The labeling was visualized by confocal immunofluorescent microscopy. In isolated rat pancreatic islets perifused with 2.75 mM glucose, alpha-PKC immunostaining was primarily cytoplasmic in distribution throughout the beta-cells. In islets stimulated with 20 mM glucose, there was a significant redistribution of alpha-PKC to the cell periphery. This glucose-induced redistribution was abolished when either mannoheptulose, an inhibitor of glucose metabolism, or nitrendipine, an inhibitor of calcium influx, were added to the perifusate. We also examined changes in the intracellular distribution of alpha-PKC in the beta-cells of awake, unstressed rats that were given an intravenous infusion of glucose. Immunocytochemical analysis of pancreatic sections from these rats demonstrated a glucose-induced translocation of alpha-PKC to the cell periphery of the beta-cells. These results demonstrate that the metabolism of glucose can induce the redistribution of alpha-PKC to the cell periphery of beta-cells, both in isolated islets and in the intact animal, and suggest that alpha-PKC plays a role in mediating glucose-induced insulin secretion.     

Identification of salt-induced transcripts by suppression subtractive hybridization and their expression analysis under the combination of salt and elevated CO<Subscript>2</Subscript> conditions in <Emphasis Type="Italic">Salicornia brachiata</Emphasis>

Soil salinity is a major abiotic stress that affects global agricultural productivity. Exploring the mechanisms that halophytes employ to thrive and flourish under saline environments is essential to increase the salt tolerance in sensitive crop species. Of the three halophytes used in this study Salicornia brachiata and Suaeda maritima belong to the same family Chenopodiaceae, while Sesuvium portulacastrum, a mangrove-associated halophyte, belongs to the family Aizoaceae. Assuming that halophytes of same family share similar salt tolerance mechanisms, we generated a suppression subtractive hybridization (SSH1) cDNA library from salt-treated leaf tissues of S. brachiata as tester and that of S. maritima as driver to identify salt-responsive genes unique to S. brachiata. To elucidate the difference in salt-tolerance mechanisms, and to identify salt-tolerance mechanisms amongst different families of halophytes, SSH2 library was generated from salt-treated leaf tissue of S. brachiata as tester and that of S. portulacastrum as driver. Totally, 87 and 49 EST clones representing unique genes were obtained from SSH1 and SSH2 libraries, respectively. Examination of the expression patterns of 17 (SSH1) and 15 (SSH2) differentially expressed genes using semi-quantitative RT-PCR confirmed up-regulation of these genes in shoots in response to salt treatment and elevated CO₂ condition, but to a different extent. This study has provided insights into the molecular responses of S. brachiata to salt stress and elevated CO₂ conditions.