24 research outputs found

    Tumor induction by monoenergetic neutrons in B6C3F1 mice

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    This study was undertaken to investigate induction of tumors by monoenergetic neutrons in B6C3F1 mice. Individual groups of 6 week-old animals of both sexes (about 30 mice/group) were exposed to 0.5 Gy of various monoenergetic neutrons (dose rate 0.5 cGy/min) and then observed for 13 months. The incidences of tumors (mainly liver neoplasms) in non-irradiated male and female controls were 11% and 0%, respectively. In the irradiated animals, the incidences were 53%, 50%, 60% and 43% in males, and 75%, 81%, 71%, and 85% in females, after 0.18, 0.32, 0.6 and 1.0 MeV neutron exposure, respectively. There were no significant differences in the tumor induction rate among the different energy group

    Assembly of Cyclic Enterobacterial Common Antigen in Escherichia coli K-12

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    We describe here the purification and quantification of a water-soluble cyclic form of enterobacterial common antigen (ECA(CYC)) from Escherichia coli K-12 as well as information regarding its subcellular location and the genetic loci involved in its assembly. Structural characterization of purified ECA(CYC) molecules obtained from E. coli K-12 revealed that they uniformly contained four trisaccharide repeat units, and they were substituted with from zero to four O-acetyl groups. Cells from overnight cultures contained approximately 2 μg ECA(CYC) per milligram (dry weight), and cell fractionation studies revealed that these molecules were localized exclusively in the periplasm. The synthesis and assembly of ECA(CYC) were found to require the wzxE and wzyE genes of the wec gene cluster. These genes encode proteins involved in the transmembrane translocation of undecaprenylpyrophosphate-linked ECA trisaccharide repeat units and the polymerization of trisaccharide repeat units, respectively. Surprisingly, synthesis of ECA(CYC) was dependent on the wzzE gene, which is required for the modulation of the polysaccharide chain lengths of phosphoglyceride-linked ECA (ECA(PG)). The presence of ECA(CYC) in extracts of several other gram-negative enteric organisms was also demonstrated; however, it was not detected in cell extracts of Pseudomonas aeruginosa. These data suggest that in addition to ECA(PG), ECA(CYC) may be synthesized in many, if not all, members of the Enterobacteriaceae

    A Miso (Japanese Soybean Paste) Diet Conferred Greater Protection against Hypertension than a Sodium Chloride Diet in Dahl Salt-Sensitive Rats

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    The purpose of this study was to compare the effects of miso and sodium chloride (NaCl) on blood pressure in both sexes of Dahl and SD rats. The systolic and diastolic blood pressures (SBP/DBP) were measured at 2, 4, 8 and 12 weeks of treatment with a miso diet including 2.3% NaCl, a high-sodium diet including 2.3% or 1.9% NaCl, or a normal diet including 0.3% NaCl (MF diet; Oriental Yeast Co., Tokyo, Japan). The rats were autopsied after 12 weeks on a diet. DBP in male Dahl rats was significantly increased by the 2.3% NaCl diet as compared with that in the MF group (p<0.01) or miso group (p<0.05) from 4 weeks of treatment. Thereafter, SBP and DBP in both the high NaCl groups were significantly increased when compared with the MF or miso group. SBP in female Dahl rats on 2.3% NaCl was significantly increased from 8 weeks after treatment. Nephropathy was observed in both sexes of Dahl rats but not SD rats. These results show that blood pressure was not increased by the miso diet

    Tumor induction by monoenergetic neutrons in B6C3F1 mice

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    This study was undertaken to investigate induction of tumors by monoenergetic neutrons in B6C3F1 mice. Individual groups of 6 week-old animals of both sexes (about 30 mice/group) were exposed to 0.5 Gy of various monoenergetic neutrons (dose rate 0.5 cGy/min) and then observed for 13 months. The incidences of tumors (mainly liver neoplasms) in non-irradiated male and female controls were 11% and 0%, respectively. In the irradiated animals, the incidences were 53%, 50%, 60% and 43% in males, and 75%, 81%, 71%, and 85% in females, after 0.18, 0.32, 0.6 and 1.0 MeV neutron exposure, respectively. There were no significant differences in the tumor induction rate among the different energy group

    O Acetylation of the Enterobacterial Common Antigen Polysaccharide Is Catalyzed by the Product of the yiaH Gene of Escherichia coli K-12

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    The carbohydrate component of the enterobacterial common antigen (ECA) of Escherichia coli K-12 occurs primarily as a water-soluble cyclic polysaccharide located in the periplasm (ECA(CYC)) and as a phosphoglyceride-linked linear polysaccharide located on the cell surface (ECA(PG)). The polysaccharides of both forms are comprised of the amino sugars N-acetyl-d-glucosamine (GlcNAc), N-acetyl-d-mannosaminuronic acid (ManNAcA), and 4-acetamido-4,6-dideoxy-d-galactose (Fuc4NAc). These amino sugars are linked to one another to form trisaccharide repeat units with the structure →3-α-d-Fuc4NAc-(1→4)-β-d-ManNAcA-(1→4)-α-d-GlcNAc-(1→. The hydroxyl group in the 6 position of the GlcNAc residues of both ECA(CYC) and ECA(PG) are nonstoichiometrically esterified with acetyl groups. Random transposon insertion mutagenesis of E. coli K-12 resulted in the generation of a mutant defective in the incorporation of O-acetyl groups into both ECA(CYC) and ECA(PG). This defect was found to be due to an insertion of the transposon into the yiaH locus, a putative gene of unknown function located at 80.26 min on the E. coli chromosomal map. Bioinformatic analyses of the predicted yiaH gene product indicate that it is an integral inner membrane protein that is a member of an acyltransferase family of enzymes found in a wide variety of organisms. The results of biochemical and genetic experiments presented here strongly support the conclusion that yiaH encodes the O-acetyltransferase responsible for the incorporation of O-acetyl groups into both ECA(CYC) and ECA(PG). Accordingly, we propose that this gene be designated wecH

    Increased Glycan Chain Length Distribution and Decreased Susceptibility to Moenomycin in a Vancomycin-Resistant Staphylococcus aureus Mutant

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    A vancomycin-resistant Staphylococcus aureus mutant, COL-VR1 (MIC, 16 μg/ml), was isolated from methicillin-resistant S. aureus COL by exposure to vancomycin. COL-VR1 also showed decreased susceptibility to teicoplanin (8-fold), methicillin (2-fold), macarbomycin (8-fold), and moenomycin (16-fold). Macarbomycin and moenomycin are thought to directly inhibit transglycosylase activity. Characterization of the mutant revealed a thickened cell wall and suppression of penicillin-induced lysis, although the amounts of the five penicillin-binding proteins (PBPs 1, 2, 3, 4, and 2′) and the profiles of peptidoglycan hydrolases were not altered. Analysis of muropeptide profile and glycan chain length distribution by reversed-phase high-pressure liquid chromatography revealed slightly decreased peptide cross-linking and an increased average glycan chain length compared to those of the parent. These results together suggest that a transglycosylase activity was enhanced in the mutant. This may represent a novel mechanism of glycopeptide resistance in S. aureus

    Inverse Associations between Obesity Indicators and Thymic T-Cell Production Levels in Aging Atomic-Bomb Survivors

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    <div><p>Reduction of the naive T-cell population represents a deteriorating state in the immune system that occurs with advancing age. In animal model studies, obesity compromises the T-cell immune system as a result of enhanced adipogenesis in primary lymphoid organs and systemic inflammation. In this study, to test the hypothesis that obesity may contribute to the aging of human T-cell immunity, a thousand atomic-bomb survivors were examined for obesity status and ability to produce naive T cells, i.e., T-cell receptor excision circle (TREC) numbers in CD4 and CD8 T cells. The number of TRECs showed a strong positive correlation with naive T cell numbers, and lower TREC numbers were associated with higher age. We found that the TREC number was inversely associated with levels of obesity indicators (BMI, hemoglobin A1c) and serum CRP levels. Development of type-2 diabetes and fatty liver was also associated with lower TREC numbers. This population study suggests that obesity with enhanced inflammation is involved in aging of the human T-cell immune system. Given the fact that obesity increases the risk of numerous age-related diseases, attenuated immune competence is a possible mechanistic link between obesity and disease development among the elderly.</p></div
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