Biomedical subjects

H Seino

Publications and source records attributed to H Seino.

11 recordsLinked to original sources

PubMed1992

The source of the oxygen atom in the alpha-hydroxyglycine intermediate of the peptidylglycine alpha-amidating reaction.

Peptidylglycine alpha-amidating activity catalyses the oxidation of a C-terminally glycine-extended peptide to a desglycine alpha-amidated peptide at the expense of ascorbate and O2 in the presence of Cu2+. The reaction involves oxidative N-dealkylation within the terminal glycine residue, with retention of the glycine N atom and release of the remainder as glyoxylate. Recent studies by us and others have revealed that the reaction consists of two steps via a carbinolamide as an intermediate (peptidyl alpha-hydroxyglycine), and also that two separate enzymes derived from a common precursor protein catalyse these steps, formation of the carbinolamide and its conversion into alpha-amide and glyoxylate. As for the mechanism of carbinolamide formation, two distinct pathways can be considered: direct mono-oxygenation at the glycine alpha-C atom and dehydrogenation leading to an imine followed by hydration. To draw a distinction between them, we carried out the reaction with D-Tyr-Val-Gly as the substrate either in the H2(18)O-enriched medium or under an atmosphere of 18O2, and isolated the alpha-hydroxylglycine intermediate. The fast-atom-bombardment mass-spectral analysis demonstrated that the hydroxy O atom comes from O2, but not from H2O, indicating that the alpha-hydroxylation should be a monooxygenase reaction.

Amidine-Lyases↗

PubMed1992

Increased in vivo production of tumor necrosis factor after development of diabetes in nontreated, long-term diabetic BB rats.

We have recently reported that chronic and systemic administration of tumor necrosis factor alpha (TNF) inhibits development of autoimmune diabetes in NOD mice and BB rats, animal models of insulin-dependent diabetes mellitus (IDDM). During these experiments, we unexpectedly found that in vivo production of TNF stimulated by a single injection of lipopolysaccharide was enhanced approximately 10 times in the long-term diabetic BB rats (P less than 0.0001), whose mean duration of diabetes with more than 16.8 mM (300 mg/dl) of nonfasting blood glucose level was 26.2 +/- 2.1 days, as compared to that in the rats of nondiabetes and in the rats at the onset of diabetes, whose mean duration of diabetes was 1.4 +/- 0.6 days. The long-term diabetic, but not short-term-diabetic, rats were also associated with increased levels of serum fructosamine/albumin (P less than 0.01) and triglyceride (P less than 0.01) and with a decreased level of serum albumin (P less than 0.01). The in vivo TNF productivity in the diabetic rats, including the short-term- and long-term-diabetic rats, was correlated positively with the level of fructosamine/albumin (P less than 0.05) and negatively with the level of serum albumin (P less than 0.05), but not with levels of blood glucose. None of these correlations were observed in nondiabetic rats. The increased LPS-induced serum TNF activity in the long-term diabetic state was observed not only in BB rats but also in NOD mice and GK rats, a model of non-IDDM, irrespective of sexes and ages, indicating that the enhancement of in vivo TNF production was a result of long-term diabetes. These findings indicate that some factor(s) associated with the long-term-diabetic state may prime macrophages in vivo to produce TNF. Further study is needed to reveal a mechanism of the enhanced TNF production and its possible relevance to various abnormalities associated with the chronic hyperglycemic state.

Age Factors↗

PubMed1992

DNA-binding domain of RCC1 protein is not essential for coupling mitosis with DNA replication.

The RCC1 protein that is required for coupling mitosis with the S phase has a DNA-binding domain in the N-terminal region outside the repeat. We found that RCC1 protein without any DNA-binding activity complemented the tsBN2 mutation with the same efficiency as that of intact RCC1 protein. In ts+ transformants of tsBN2 cells transfected with the RCC1 cDNA lacking the DNA-binding domain, an endogenous RCC1 disappeared at 39.5 degrees C, and the deleted RCC1 protein encoded by the transfected cDNA was found in the cytoplasm, but a significant amount of it was also found in the nuclei. This deleted RCC1 protein was eluted from the nuclei with the same concentration of NaCl and DNase I as was used for the intact RCC1 protein in BHK21 cells. Furthermore, the deleted RCC1 protein co-migrated with the nucleosome fraction on sucrose density gradient analysis. These results indicate that the RCC1 protein binds chromatin with the aid of other unknown protein(s). Thus, the DNA-binding domain of RCC1 protein is not essential for coupling between the S and M phases, but was shown instead to function as a nuclear translocation signal.

Amino Acid Sequence↗

PubMed1991

Mutation of the hamster cell cycle gene RCC1 is complemented by the homologous genes of Drosophila and S.cerevisiae.

The RCC1 gene has been isolated from several vertebrates, including human, hamster and Xenopus. Genes similar to RCC1, namely BJ1 and SRM1/PRP20, have been isolated from the insect Drosophila and from the budding yeast Saccharomyces cerevisiae. A mutation of the RCC1 gene in the hamster BHK21 cell line, tsBN2, confers pleiotropic phenotypes, including G1 arrest and premature induction of mitosis in cells synchronized at the G1/S boundary. Similarly, mutations of the SRM1/PRP20 gene are pleiotropic; the srm1 mutant shows G1 arrest and suppression of the mating defect of mutants lacking pheromone receptors, and the prp20 mutant shows an alteration in mRNA metabolism. Here we show that both BJ1 and SRM1/PRP20 complement the temperature sensitive phenotype of the tsBN2 cells. Like RCC1 proteins of vertebrates, the protein products of the Drosophila and yeast RCC1 homologues were located in the nuclei of the mammalian cells. These results suggest that the BJ1 and SRM1/PRP20 genes are functionally equivalent to the vertebrate RCC1 genes, and that the RCC1 gene plays an important role in the regulation of gene expression in the eukaryotic cell cycle.

Amino Acid Sequence↗

PubMed1991

RCCl is a nuclear protein required for coupling activation of cdc2 kinase with DNA synthesis and for start of the cell cycle.

Explore the source record for details and available documents.

Animals↗

PubMed1991

Inhibition of autoimmune diabetes in NOD mice with serum from streptococcal preparation (OK-432)-injected mice.

We have recently reported that systemic and chronic administration of recombinant tumour necrosis factor alpha (TNF-alpha), as well as streptococcal preparation (OK-432), inhibits development of insulin-dependent diabetes mellitus (IDDM) in NOD mice and BB rats, models of IDDM. In this study we examined whether serum containing endogenous TNF induced by OK-432 injection could inhibit IDDM in NOD mice. Treatment twice a week from 4 weeks of age with OK-432-injected mouse serum, which contained endogenous TNF (75U), but not IL-1, IL-2 and interferon-gamma (IFN-gamma) activity, reduced the intensity of insulitis and significantly inhibited the cumulative incidence of diabetes by 28 weeks of age in NOD mice, as compared with the incidence in non-treated mice (P less than 0.01) and in mice treated with control serum (P less than 0.02). This inhibitory effect of the serum was diminished, although not significantly, by neutralization of serum TNF activity with anti-mouse TNF antibody. In the mice treated with the serum from OK-432-injected mice, Thy-1.2+ or CD8+ spleen cells decreased (P less than 0.01) and surface-Ig+ (S-Ig+) cells increased (P less than 0.05), whereas the proliferative response of spleen cells to concanavalin A (P less than 0.01) and lipopolysaccharide (P less than 0.05) increased. The results indicate that the inhibition by OK-432 treatment of IDDM in NOD mice was partially mediated by serum factors including endogenous TNF.

Animals↗

PubMed1991