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Biomedical subjects

S Miyazawa

Publications and source records attributed to S Miyazawa.

At least 127 records · Page 7Linked to original sources
PubMed1980

Turnover of enzymes of peroxisomal beta-oxidation in rat liver.

Male Wistar rats were given a diet containing 2% (w/w) di-ethylhexyl)-phthalate (DEHP), a peroxisomal proliferator, for 4 weeks. The activities of enzymes of peroxisomal beta-oxidation and of catalase were markedly increased by the DEHP administration. The time required to reach halfway to the maximal induction for enzymes of peroxisomal beta-oxidation was 5--7 days, whereas that for catalase was 3 days. A separate DEHP group was placed on the control diet after 14 days of feeding with the DEHP diet. On the withdrawal of DEHP, activities of enzymes of the beta-oxidation system and of catalase decreased to the control levels with a half-life of 2--3 days. Responses of some mitochondrial enzymes involved in fatty acid oxidation are also described.

Animals↗
PubMed1980

Properties of mitochondria and peroxisomal enoyl-CoA hydratases from rat liver.

Mitochondrial and peroxisomal enoyl-CoA hydratases were purified from rat liver. The mitochondrial enzyme, with a molecular weight of 161,000, was composed of 6 identical subunits. The molecular structure of the rat liver enzyme was very similar to that of the bovine liver enzyme. Acetoacetyl-CoA was a competitive inhibitor of the mitochondrial enzymes. The results of titration of the rat liver enzyme with acetoacetyl-CoA suggest that 3 subunits of the enzyme exhibit catalytic activity. The catalytic properties of the enzyme were studied. The peroxisomal enzyme was composed of one polypeptide with a molecular weight of 70,000-81,000. Some of the enzyme molecules were shown to be cleaved to two polypeptides in the cell by the following methods: amino acid analysis, peptide mapping and immunoprecipitin reaction. The catalytic properties of the peroxisomal enzyme were different from those of the mitochondrial enzyme. The peroxisomal enzyme is a bifunctional enzyme exhibiting 3-hydroxyacyl-CoA dehydrogenase activity. Studies on the titration with acetoacetyl-CoA, the effects of salts, SH titration and proteolytic inactivation suggest that the active centers for these two reactions are located at different sites.

Amino Acids↗
PubMed1980

Relationship between mutability, polarity and exteriority of amino acid residues in protein evolution.

A systematic study was carried out on mutability of amino acid residues in evolving proteins in relation to their polarity and location within three-dimensional structure of proteins. Exteriority of residue sites is quantitatively defined as accessibility based on their static accessible surface area to solvent water molecule. Residue sites are classified into interior and exterior depending on their accessibility. More frequent substitution on exterior sites is confirmed to be general in eight sets of homologous protein families regardless of their biological functions and of presence or absence of a prosthetic group. Virtually all types of amino acid residues are found to have higher mutabilities on the exterior than in the interior. No correlation between mutability and polarity was observed of amino acid residues in the interior and on the exterior, respectively. Amino acid residues are classified into three depending on their polarity, polar (Arg, Lys, His, Gln, Asn, Asp and Glu), weak polar (Ala, Pro, Gly, Thr and Ser) and nonpolar (Cys, Val, Met, Ile, Leu, Phe, Tyr and Trp). Amino acid replacements during protein evolution are very conservative; 88% and 76% of them in the interior and on the exterior, respectively, are within the same group of the three. Inter-group replacements are such that weak polar residues are replaced more often by nonpolar residues in the interior and more often by polar residues on the exterior.

Amino Acids↗
PubMed1980

The presence of a new 3-oxoacyl-CoA thiolase in rat liver peroxisomes.

A novel 3-oxacyl-CoA thiolase was found in rat liver. This thiolase, mitochondrial general 3-oxacyl-CoA thiolase and acetoacetyl-CoA thiolase were purified from the rat liver after the induction of these activities by the administration to rats of di(2-ethylhexyl)phthalate, which enhanced the peroxisomal beta-oxidation activity. The new 3-oxoacyl-CoA thiolase was distinguished from mitochondrial and cytoplasmic thiolases by the following: DEAE-cellulose chromatography, phosphocellulose chromatography, immunochemical titration, and substrate specificity. Subcellular fractionation of liver and sucrose-density-gradient centrifugation of the light mitochondrial fraction revealed that the new thiolase was mainly in peroxisomes.

Acetyl-CoA C-Acyltransferase↗
PubMed1979

Two types of amino acid substitutions in protein evolution.

The frequency of amino acid substitutions, relative to the frequency expected by chance, decreases linearly with the increase in physico-chemical differences between amino acid pairs involved in a substitution. This correlation does not apply to abnormal human hemoglobins. Since abnormal hemoglobins mostly reflect the process of mutation rather than selection, the correlation manifest during protein evolution between substitution frequency and physico-chemical difference in amino acids can be attributed to natural selection. Outside of 'abnormal' proteins, the correlation also does not apply to certain regions of proteins characterized by rapid rates of substitution. In these cases again, except for the largest physico-chemical differences between amino acid pairs, the substitution frequencies seem to be independent of the physico-chemical parameters. The limination of the substituents involving the largest physico-chemical differences can once more be attributed to natural selection. For smaller physico-chemical differences, natural selection, if it is operating in the polypeptide regions, must be based on parameters other than those examined.

Amino Acid Sequence↗
PubMed1979

Ruptured aneurysm of aortic sinus of Valsalva into right ventricle.

We report a patient with ruptured aneurysm of the aortic sinus of Valsalva into the right ventricle, whose heart murmur represented only a diastolic element without aortic regurgitation. Surgery revealed a small opening through myocardium of the ventricular septum without ventricular septal defect. During systole, the opening was constricted and presumably closed with myocardial contraction, and left-to-right shunt might have occurred only in diastole. This might lead to only a diastolic murmur.

Adult↗
PubMed1978

Effects of di-(2-ethylhexyl)phthalate administration on carbohydrate and fatty acid metabolism in rat liver.

1. Rats were fed on a diet containing 0, 1, 2, or 4% di-(2-ethylhexyl)phthalate (DEHP), a widely used plasticizer, for four weeks. 2. The level of plasma triglyceride was decreased in both the 1% DEHP and the 2% DEHP groups maintained for 1 to 2 weeks, but that of cholesterol was not changed. Plasma free fatty acid and ketone bodies increased in all DEHP groups. 3. The level of blood glucose was depressed to about 80% in the 2% and the 4% DEHP groups. Liver glycogen decreased markedly. Isotopic incorporations of 14C from [2-14C]pyruvate into blood glucose and liver glycogen were decreased. The changes in the contents of intermediates in the liver indicate that gluconeogenesis is inhibited at the reaction(s) between 3-phosphoglycerate and fructose 1,6-diphosphate. 4. Hepatic fatty acid synthesis increased about 2-fold on DEHP administration. The content of phospholipid in the liver was increased, whereas that of triglyceride was decreased. The rate of phospholipid synthesis was increased, but that of triglyceride was not changed.

Acetates↗
PubMed1978

Volume and polarity changes accompanied by amino acid substitutions in protein evolution.

We evaluated the volume and polarity changes accompanied by amino acid substitutions along branches of the phylogenetic trees of cytochrome c, myoglobin and hemoglobin alpha and beta chains. In most cases the volume changes accompanied by the substitutions were found to be much larger than the volume of cavities existing in the interior of X-ray-analysed proteins. This implies that the interior of the proteins is very flexible and the necessary space for a larger amino acid residue substitution can be provided by adjusting nearby structures. Also, the volume and polarity changes are not particularly dependent on whether the substituted site is located in the exterior or interior of the proteins. This result supports the concept of the covarions by Fitch and Markowitz, when combined with the known fact that the exterior sites are more variable than the interior ones during protein evolution.

Amino Acids↗
PubMed1976

Effect of triamcinolone administration on content of flavins in rabbit liver.

Triamcinoline acetonide (10 mg per kg of body weight a day) was administered to rabbit fed on a laboratory chow diet. The content of flavins in liver but not in kidney, muscle and brain started to decrease 24 h after a single dose. The activities of enzymes in the liver were determined: the activities of pyruvate dehydrogenase complex, lipoamide dehydrogenase (NADH:lipoamide oxidoreductase EC 1.6.4.3), NADH dehydrogenase (NADH : (acceptor) oxidoreductase EC 1.6.99.3) and D-amino acid oxidase (D-amino acid: oxygen oxidoreductase (deaminating) EC 1.4.3.3) were decreased but those of succinate dehydrogenase (succinate : (acceptor) oxidoreductase EC 1.3.99.1) and xanthine oxidase (xanthine : oxygen oxidoreductase EC 1.2.3.2) remained unchanged. The activities of enzymes in the kidney, however, remained unchanged except the decrease in the activity of pyruvate dehydrogenase complex.

Animals↗
PubMed1975

Effects of ethyl p-chlorophenoxyisobutyrate on carbohydrate and fatty acid metabolism in rat liver.

1. Rats were fed on a diet containing ethyl p-chlorophenoxyisobutyrate (0.3%, w/w) for 14 days. 2. The alterations of contents of intermediates in the liver indicate that gluconeogenesis is inhibited at the reaction(s) between 3-phosphoglycerate and fructose 1,6-diphosphate. The [nad+]/([nadh] ratios in cytoplasm and mitochondria were increased about 3- and 4-fold, respectively. Marked increases in the contents of CoA and its thioesters were found. 3. Hepatic fatty acid synthesis increased about 3-fold. There was no evidence of inhibition of the acetyl-CoA carboxylase [EC 6.4.1.2] reaction by the drug.

Animals↗
PubMed1975

The effect of tryptophan administration on fatty acid synthesis in the livers of rats under various nutritional conditions.

1. Tryptophan was administered to rats under various nutritional conditions: fasted for 24 hr, fasted and refed with glucose or corn-oil, fasted and administered glycerol intramuscularly, and nonfasted. 2. The changes in the contents of glycolytic intermediates in the livers indicated that the phosphoenolpyruvate carboxykinase [EC 4.1.1.32] reaction is inhibited by tryptophan administration in all groups of rats. The inversely related changes in the contents of malate and phosphoenolpyruvate were associated with the accumulation of quinolinate in the livers. The content of quinolinate which exhibited the half-maximal effect on the contents of both metabolites was 0.1-0.2 mumole per g liver. 3. The rate of incorporation of 3H from 3H2O into the total hepatic fatty acids was increased about 2-fold by the administration of this amino acid to the fasted rats. The enhancement of the rate was closely related to the increase in the citrate content. The hyperlipogenesis was also related to the decrease of acetyl-CoA and the increase of malonyl-CoA. The content of long-chain acyl-CoA was not affected. These effects of tryptophan administration on the hepatic fatty acid metabolism were found in all groups of rats. The liver content of glycerol 3-phosphate was decreased by tryptophan administration was markedly increased by glycerol injection. The injection of glycerol into the control and the tryptophan-treated rats produced a marked increase of glycerol 3-phosphate but did not affect the rate of fatty acid synthesis in the livers of either group. 4. It may be concluded that, in the livers of rats under various nutritional conditions, the short-term control of fatty acid synthesis by tryptophan administration is most likely due to the activation of acetyl-coenzyme A carboxylase [EC 6.4.1.2] by citrate.

Acetyl Coenzyme A↗