The antioxidative function of eicosapentaenoic acid in a marine bacterium, Shewanella marinintestina IK-1

When the eicosapentaenoic acid (EPA)-deficient mutant strain IK-1Delta8 of the marine EPA-producing Shewanella marinintestina IK-1 was treated with various concentrations of hydrogen peroxide (H(2)O(2)), its colony-forming ability decreased more than that of the wild type. Protein carbonylation, induced by treating cells with 0.01 mM H(2)O(2) under bacteriostatic conditions, was enhanced only in cells lacking EPA. The amount of cells recovered from the cultures was decreased more significantly by the presence of H(2)O(2) for cells lacking EPA than for those producing EPA. Treatment of the cells with 0.1 mM H(2)O(2) resulted in much lower intracellular concentrations of H(2)O(2) being consistently detected in cells with EPA than in those without EPA. These results suggest that cellular EPA can directly protect cells against oxidative damage by shielding the entry of exogenously added H(2)O(2) in S. marinintestina IK-1.     

Role of Ser216 in the mechanism of action of membrane-bound lytic transglycosylase B: further evidence for substrate-assisted catalysis

Lytic transglycosylases cleave the beta-(1-->4)-glycosidic bond in the bacterial cell wall heteropolymer peptidoglycan between the N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) residues with the concomitant formation of a 1,6-anhydromuramoyl residue. Based on sequence alignments, Ser216 in Pseudomonas aeruginosa membrane-bound lytic transglycosylase B (MltB) was targeted for replacement with alanine to delineate its role in the enzyme's mechanism of action. The specific activity of the Ser216-->Ala MltB derivative was less than 12% of that for the wild-type enzyme, while its substrate binding affinity remained virtually unaltered. These data are in agreement with a role of Ser216 in orienting the N-acetyl group on MurNAc at the -1 subsite of MltB for its participation in a substrate-assisted mechanism of action.     

Exogenous H(2)O(2) and catalase treatments interfere with Tri genes expression in liquid cultures of Fusarium graminearum

Effect of exogenous H(2)O(2) and catalase was tested in liquid cultures of the deoxynivalenol and 15-acetyldeoxynivalenol-producing fungus Fusarium graminearum. Accordingly to previous results, H(2)O(2) supplementation of the culture medium leads to increased toxin production. This study indicates that this event seems to be linked to a general up regulation of genes involved in the deoxynivalenol and 15-acetyldeoxynivalenol biosynthesis pathway, commonly named Tri genes. In catalase-treated cultures, toxin accumulation is reduced, and Tri genes expression is significantly down regulated. Furthermore, kinetics of expression of several Tri genes is proposed in relation to toxin accumulation. Biological meanings of these findings are discussed.     

Evidence for a role of glycosphingolipids in CXCR4-dependent cell migration

Chemotaxis induction is a major effect evoked by stimulation of the chemokine receptor CXCR4 with its sole ligand CXCL12. We now report that treatment of CHP-100 human neuroepithelioma cells with the glucosylceramide synthase (GCS) inhibitor DL-threo-1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol inhibits CXCR4-dependent chemotaxis. We provide evidence that the phenomenon is not due to unspecific effects of the inhibitor employed and that inhibition of GCS neither affects total or plasmamembrane CXCR4 expression, nor CXCL12-induced Ca(2+) mobilization. The effects of the GCS inhibitor on impairment of CXCL12-induced cell migration temporally correlated with a pronounced downregulation of neutral glycosphingolipids, particularly glucosylceramide, and with a delayed and more moderate downregulation of gangliosides; moreover, exogenously administered glycosphingolipids allowed resumption of CXCR4-dependent chemotaxis. Altogether our results provide evidence, for the first time, for a role glycosphingolipids in sustaining CXCL12-induced cell migration.     

Pathogenic mitochondrial DNA-induced respiration defects in hematopoietic cells result in anemia by suppressing erythroid differentiation

Anemia is a symptom in patients with Pearson syndrome caused by the accumulation of mutated mitochondrial DNA (mtDNA). Such mutated mtDNAs have been detected in patients with anemia. This suggested that respiration defects due to mutated mtDNA are responsible for the anemia. However, there has been no convincing experimental evidence to confirm the pathophysiological relation between respiration defects in hematopoietic cells and expression of anemia. We address this issue by transplanting bone marrow cells carrying pathogenic mtDNA with a large-scale deletion (ΔmtDNA) into normal mice. The bone marrow-transplanted mice carried high proportion of ΔmtDNA only in hematopoietic cells, and resultant the mice suffered from macrocytic anemia. They show abnormalities of erythroid differentiation and weak erythropoietic response to a stressful condition. These observations suggest that hematopoietic cell-specific respiration defects caused by mtDNAs with pathogenic mutations are responsible for anemia by inducing abnormalities in erythropoiesis.     

Osmotic stress blocks NF-kappaB-dependent inflammatory responses by inhibiting ubiquitination of IkappaB

The inhibitory effects of hypertonic conditions on immune responses have been described in clinical studies; however, the molecular mechanism underlying this phenomenon has yet to be defined. Here we investigate osmotic stress-mediated modification of the NF-kappaB pathway, a central signaling pathway in inflammation. We unexpectedly found that osmotic stress could activate IkappaBalpha kinase but did not activate NF-kappaB. Osmotic stress-induced phosphorylated IkappaBalpha was not ubiquitinated, and osmotic stress inhibited interleukin 1-induced ubiquitination of IkappaBalpha and ultimately blocked expression of cytokine/chemokines. Thus, blockage of IkappaBalpha ubiquitination is likely to be a major mechanism for inhibition of inflammation by hypertonic conditions.     

Identification and characterization of 10 polymorphic microsatellite loci in the German cockroach,Blattella germanica

Primer sequences and initial characterization are presented for 10 microsatellite loci isolated from the German cockroach, Blattella germanica. In a sample of 30 individuals from a single population sample, all loci were polymorphic with two to 12 alleles segregating per locus and levels of observed heterozygosity ranging from 0.27 to 0.92. One locus showed a deficit of heterozygotes. Experimental conditions are described for polymerase chain reaction multiplexing, which enables the genotyping of eight loci in three electrophoretic runs consisting of one set of three and two sets of two markers. Seven primer sets cross‐amplify in the related Blattella asahinai.     

改性胶原蛋白膜用于大肠杆菌EP8-10组合固定化

探讨了不同方法对胶原蛋白膜进行改性处理,结果表明经过甲醛处理过的胶原蛋白膜具有良好的通透性及耐水性能。将胶原蛋白膜与卡拉胶凝胶颗粒形成组合固定化体系,用于大肠杆菌EP8-10固定化,天冬氨酸转氨酶活回收率达到了91.3%,反应20批次后,酶活回收率仍在80%以上。