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Biomedical subjects

H Ohsawa

Publications and source records attributed to H Ohsawa.

89 records · Page 5Linked to original sources
PubMed1985

Influence of extracellular phosphate concentrations on the regulation of hepatic glucose output.

Experiments were carried out to investigate the role of extracellular phosphate in the hormonal regulation of glycogenolysis in perfused fed-rat liver. Omission of phosphate from the perfusate did not affect the ATP, ADP and AMP contents of the tissue and the basal glucose output from the perfused liver. However, it inhibited significantly the glycogenolysis induced by glucagon, cyclic AMP, phenylephrine and vasopressin but not that induced by 2,4-dinitrophenol. In the absence of perfusate phosphate, the increase in phosphorylase a activity caused by the addition of glucagon, phenylephrine and vasopressin was significantly less than that observed in the presence of perfusate phosphate. Insulin inhibition of the glucagon- or cyclic AMP-induced glycogenolysis was abolished when the perfusion was carried out with the phosphate-free buffer. However, the inhibitory effect of insulin on phenylephrine-induced glycogenolysis was clearly demonstrated even when the perfusate contained no phosphate. These data indicate that in the phosphate-depleted liver, the hormonal control of phosphorylation and dephosphorylation of phosphorylase is impaired. The difference in the phosphate dependency of insulin action on glucagon-and alpha-adrenergic agonist-induced glycogenolysis suggests that the mechanism or site of insulin action on glucagon and phenylephrine is different.

Adenine Nucleotides↗
PubMed1984

In vitro template activity of 0.3 mRNA from wild type and initiation mutants of bacteriophage T7.

Bacteriophage T7 0.3 mRNA synthesised and processed in vitro has been purified starting from the DNA of T7+ as well as from that of two initiation mutants of T7 (CR17 with a U----C transition in the initiation codon and CR35b whose potential Shine and Dalgarno (S-D) interaction is interrupted by a G----A transition). These mRNAs were used as templates to direct the binding of fMet-tRNA and the synthesis of 0.3 protein in both E. coli and wheat germ cell-free systems. The initiation codon mutant displayed approximately 50% inhibition of fMet-tRNA binding and 0.3 protein synthesis in both systems. The S-D sequence mutant, on the other hand, was found to be less affected than the initiation triplet mutant (20%-40% inhibition) in both fMet-tRNA binding and template activity in the E. coli system. In the wheat germ system, which does not make use of the S-D interaction, however, this mutant displayed normal template activity suggesting that the inhibition obtained in the E. coli system, albeit slight, is due to the impairment of the S-D interaction and not to an alteration of the mRNA secondary or tertiary structure caused by the base substitution.

Cell-Free System↗
PubMed1983

Chemical modification in situ of Escherichia coli 30 S ribosomal proteins by the site-specific reagent pyridoxal phosphate. Inactivation of the aminoacyl-tRNA and mRNA binding sites.

epsilon-Amino groups of lysines of 30 S ribosomal subunits with affinity for phosphate groups were selectively modified in situ by reaction with pyridoxal phosphate and reduction of the Schiff base with nonradioactive or radioactive sodium borohydride. This reaction modified only a limited number of ribosomal proteins and resulted in the loss of only some 30 S activities. The modified proteins were identified and the extent of their modification determined. The main targets of the reaction were S3 greater than S1 greater than S6. The activity most severely affected by the pyridoxal phosphate reaction was mRNA-dependent aminoacyl-tRNA binding. Some inhibition of poly(U) binding was also observed, while neither binding of initiation factors nor association with 50 S subunits was inhibited. The inhibition of aminoacyl-tRNA binding showed distinct selectivity: the inhibition was far greater with NAcPhe-tRNA than with fMet-tRNA and with "A" site than with "P" site binding. In addition, initiation complex formation with some mRNAs (e.g. MS2 RNA) was affected more than with others (e.g. T7 early mRNA). Ribosome reconstitution experiments showed that the modification of protein S3 was the primary cause of the inhibition; a role was also played by ribosomal proteins S1, S2, and S21. Substrate protection experiments showed that the 30 S activity can be protected from pyridoxal phosphate inactivation upon formation of a ternary complex with poly(U) and tRNAPhe or NAcPhe-tRNAPhe. Accordingly, the extent of modification of ribosomal protein S3 was reduced in the ternary complex while modification of S1 was reduced in the presence of poly(U) alone.

Escherichia coli↗
PubMed1982

Different mode of action of cimetidine and prostaglandin on the rat gastric mucosa under stress loading by restrain and water-immersion.

Gastric mucosal blood flow and oxygen tension in the corporal mucosa gradually declined after water immersion in the control animals. Neither cimetidine nor prostaglandin E2 had any influence on the decrease of the corporal mucosal blood flow or mucosal oxygen tension during seven hours of stress loading. The stress ulceration began to occur starting three hours after cold immersion in the control rats, and the deficit of energy metabolism was attributed to reduced oxidative phosphorylation from tissue hypoxia resulting from lowered blood flow and oxygen tension under stress. Cimetidine (4 mg/kg) maintained aerobic glycolysis, continued to produce high-energy phosphates and kept the energy charge unchanged in the gastric mucosa. In addition, PG E2-Me (100 micrograms/kg) showed similar, but less marked and shorter-lived effects on aerobic glycolysis and ATP production, whereas the energy charge of the adenosine pool decreased significantly from that produced by cimetidine. These results indicated that cimetidine significantly reduced energy requirements as compared with the control and PG E2 groups due to marked inhibition of gastric secretion and produced inhibition of mucosal ulceration by water immersion. On the other hand, increased energy requirements due to the rise of cytoprotective mucoprotein production and a resultant decrease of the energy charge were seen with PG E2 as compared with cimetidine.

Animals↗
PubMed1982

Population dynamics of Japanese monkeys with special reference to the effect of artificial feeding.

Population dynamics of Japanese monkeys (Macaca fuscata) have been studied at Mt. Ryozen, central Japan, between 1969 and 1980. The troop had been artificially fed until August 1973 and, since then, has been living in its natural habitat without artificial feeding. Increase in body weight, primiparous age, age-specific natality, survivorship and mortality, population and biomass growth rate, and age of disappearance of young males were compared between the two study periods, with and without artificial feeding. Comparison of population parameters in each study period was also done between social classes, central and peripheral. As shown, in table VII, it was revealed that artificial feeding was an important factor in population growth and, furthermore, that this effect was mainly on the kin-groups of the central class of the troop. In the natural habitat without artificial feeding most of the population parameters showed almost the same figure for kin-groups of central and peripheral classes.

Animal Husbandry↗
PubMed1982

[Sensitivity to second-generation cephem agents of clinically isolated strains of bacteria in otorhinolaryngological field (author's transl)].

Clinically isolated 741 strains of 10 bacterial genus (except for Pseudomonas aeruginosa) which are frequent causal pathogens of infection in the otorhinolaryngological field were examined for their sensitivity to second-generation cephem agents, CTM, CXM and CMZ using the first-generation agent, CEZ, as a control. 1) The antibacterial activity of CTM, CXM, and CMZ was expanded to H. influenzae and Proteus spp. (indole positive) as compared with the first-generation agent, CEZ. CTM and CXM and strong antibacterial activity against H. influenzae. CMZ was slightly inferior to them in this activity. In contrast, against Proteus spp. (indole positive) CMZ was most effective and CTM was more effective than CXM. 2) The proportion of strains of S. aureus resistant to CEPs was 6.5% in CEZ, 4.8% in CTM, 8.1% in CXM, and as low as 1.6% in CMZ.

Bacteria↗
PubMed1982

[Evaluation of clinical efficacy of a cephem antibiotic, cefmetazole, in inflammatory infections of the upper respiratory tract].

We had reported the fundamental study on the utility of a new cephem antibiotic, cefmetazole (CMZ). On the basis of the results we administered CMZ to patients to investigate its clinical utility in this study. 1. CMZ was administered to 53 patients including 4 infants. They consisted of 30 cases of acute tonsillitis, 10 of peritonsillar abscess, 10 of laryngitis or pharyngitis, and 3 of sinusitis. 2. One of 2 g CMZ was administered to an adult patient except for l case and 0.5 g to an infant patient once or twice daily for at least 3 days. The method of administration was one shot intravenous injection, intravenous drip infusion or intramuscular injection. 3. The strict criteria for evaluating the efficacy of a drug were made and used for judging the efficacy of CMZ. 4. CMZ was clinically effective in 100% of patients with acute tonsillitis, 100% of those with peritonsillar abscess, 90% of those with laryngitis or pharyngitis, and 67% of those with sinusitis. 5. Bacteriologically, a single sort of bacterium was isolated in most cases of acute tonsillitis, laryngitis and pharyngitis and in the half of cases of peritonsillar abscess. Two and more sorts of bacteria were isolated in the other cases. The main bacteria isolated were beta-Streptococcus, S. pneumoniae and H. influenzae. Anaerobic bacteria, mostly Peptococcus spp. and Peptostreptococcus spp., were detected in peritonsillar abscess. 6. The clinical results agreed with the clinicobacteriological results. All the bacteria detected before treatment of CMZ disappeared. CMZ also acted effectively in cases in which H. influenzae was suspected to be a causative organism. 7. The present results of CMZ treatment were similar to those of cefazolin (CEZ) treatment published so far. 8. Thus, CMZ was confirmed fundamentally and clinically to be a very useful drug for infection of the upper respiratory tract.

Adolescent↗
PubMed1981

Structure-function relationship in Escherichia coli initiation factors. Identification of a lysine residue in the ribosomal binding site of initiation factor by site-specific chemical modification with pyridoxal phosphate.

Incubation of Escherichia coli initiation factor 3 (IF3) with pyridoxal phosphate (PLP) followed by reduction with sodium borohydride resulted in the selective modification and inactivation of this protein. The ribosomal-binding site (RNA-binding site) of IF3 is the target of PLP modification, since (a) the phosphate residue of PLP is required for inactivation; (b) RNA as well as synthetic polynucleotides (especially guanine-containing one) protect IF3 from inactivation; and (c) 30 S, but not 50 S ribosomal subunits, protect IF3 from PLP modification and from inactivation. The incorporation of PLP into IF3 occurred exclusively at lysine residues by reduction of the Schiff bases yielding epsilon-(5'-phosphopyridoxyl)lysine. The PLP-modified lysines were identified by amino acid analysis and sequencing of the PLP-modified peptides. Out of the 20 lysines of the factor, only Lys 2, Lys 5, Lys 99, Lys 112, Lys 166, and an unidentified Lys of the central cluster of the molecule (Lys 86, 87, 90, 91, 96) were found to be modified to varying degrees. The incorporation of 3 to 4 mol of PLP/mol of IF3 is accompanied by a substantial (greater than or equal to 80%) inactivation of this protein; the loss of activity follows apparent first order kinetics, and the inactivation results from the modification of just 1 Lys residue. This essential Lys residue was identified by various criteria to be Lys 112. The identification of an "active region" in the IF3 molecule is emerging from this as well as from other chemical modification studies.

Amino Acids↗
PubMed1977

Identification of a temperature-sensitive asparaginyl-transfer ribonucleic acid synthetase mutant of Escherichia coli.

A temperature-sensitive mutant of Escherichia coli K-12 isolated previously (H. Ohsawa and B. Maruo, J. Bacteriol. 127:1157-1166, 1976) was found to have an alteration in asparaginyl-transfer ribonucleic acid synthetase. This alteration can account for the temperature-sensitive phenotype of the mutant. No evidence was obtained to support the previous suggestion that ribosomal protein S1 is altered in this mutant. Combined with the previous genetic studies, we conclude that the newly defined genetic locus, asnS, for the asparaginyl-transfer ribonucleic acid synthetase maps near pyrD at 21 min on the E. coli chromosome.

Amino Acyl-tRNA Synthetases↗
PubMed1976

Restoration by ribosomal protein S1 of the defective translation in a temperature-sensitive mutant of Escherichia coli K-12: characterization and genetic studies.

A temperature-sensitive mutant of Escherichia coli was isolated that had a temperature-sensitive defect in ribosomal-wash protein(s) required for translation in vitro of E. coli endogenous messenger ribonucleic acid. It was found that 30S ribosomal protein S1 rescued the defect in the ribosomal-wash protein(s) of the mutant and that the complete restoration to the wild-type level was attained when 1 mol of protein S1 was added to 1 mol of 70S ribosome. The mutation, tss, causing such a defect was mapped at 21 min and was closely linked to the pyrD locus, the region of which was entirely different from that of the other genes coding for the many ribosomal proteins of E. coli. These results indicate that the gene specified by this mutation is involved in the function of the 30S ribosomal protein S1.

Bacterial Proteins↗