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Biomedical subjects

K Hiraga

Publications and source records attributed to K Hiraga.

At least 145 records · Page 8Linked to original sources
PubMed1984

Chromatographic differentiation of the mitochondrial and cytosolic fumarases of rat liver and Baker's yeast and differential induction of two fumarases of Baker's yeast.

The mitochondrial and cytosolic fumarases of rat liver could be separated from each other by Bio-Gel HTP column chromatography, showing that there are some conformational differences between the native proteins of the mitochondrial and cytosolic fumarases which have been indistinguishable by their physicochemical, catalytic, and immunochemical properties. The fumarase associated with the mitochondrial fraction of Baker's yeast could also be separated from that located in the cytosol by the Bio-Gel HTP column chromatography. By applying this chromatography to the differential determination of the fumarase activities in the Baker's yeast cultured under various conditions, it was shown that the mitochondrial and cytosolic fumarases in the cell are regulated by independent control systems.

Animals↗
PubMed1984

An improved method for labeling carboxyatractyloside by [3H]KBH4.

Carboxyatractyloside was labeled with [3H]KBH4 after oxidation of the primary alcohol of the glucose disulfate moiety by dicyclohexylcarbodiimide and P2O5 under anhydrous conditions in a dimethylsulfoxide medium. The 3H-labeled product was purified by DE 52 column chromatography followed by Cellulofine GCL 25 column chromatography. The final 3H-labeled product gave a single spot on a thin-layer chromatogram, and its Rf value was the same as that of authentic carboxyatractyloside. The biological activities (such as inhibition of state 3 respiration and binding to the adenine nucleotide carrier) were also comparable with those of authentic carboxyatractyloside.

Animals↗
PubMed1983

On the mechanism of covalent binding of butylated hydroxytoluene to microsomal protein.

The structures of cysteine conjugates of 3,5-di-tert-butyl-4-hydroxytoluene (BHT) and the binding sites of BHT metabolites on microsomal protein were investigated by 13C nuclear magnetic resonance (13C-NMR) and gas-liquid chromatography/mass spectrometry. The cysteine conjugates of 2,6-di-tert-butyl-4-hydroxymethylphenol (BHT-alcohol) and 2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone (quinone methide), which are metabolites of BHT found in rat liver and specifically reacts with thiol compounds, were prepared as alcoholic aqueous solutions. The molecular structure of the cysteine conjugate of BHT-alcohol agreed completely with that of quinone methide in 13C-NMR spectra or mass spectra. These spectra of both conjugates further showed that the conjugates are due to thioether binding between the 4-methyl group of metabolites and the sulfhydryl group of cysteine. When [14C]BHT-bound microsomes prepared in vitro were enzymatically hydrolyzed with Pronase E, the major radioactive material that eluted with methanol from a column of Amberlite XAD-2 and gave a positive ninhydrin reaction was identified as a cysteine conjugate of BHT by comparing its Rf values on TLC and mass spectrum. On the basis of the results, it was apparent that the binding site of activated substituents of BHT on protein was mainly the sulfhydryl group of cysteine residue.

Animals↗
PubMed1983

Testicular atrophy induced by di-2-ethylhexyl phthalate: effect of zinc supplement.

The administration of di-2-ethylhexyl phthalate (DEHP) to young male rats was found to cause testicular atrophy and loss of testicular zinc. In an attempt to test the hypothesis that a cause and effect relationship exists between DEHP-induced loss of testicular zinc and testicular injury, zinc was coadministered (by ip injection or by dietary supplementation) with DEHP (po) for 10 days and organ weights and zinc concentrations were then measured. This testicular atrophy was not prevented by coadministration of zinc. The zinc concentration in the testis was not increased by zinc supplement despite increases in zinc concentrations in liver and serum. The results suggest that the toxic effect of DEHP on the testis may not result from an interference with gastrointestinal absorption of zinc.

Animals↗
PubMed1983

Vitamin K content of liver and feces from vitamin K-deficient and butylated hydroxytoluene (BHT)-treated male rats.

Vitamin K content of liver and feces from male rats fed diets containing butylated hydroxytoluene (BHT) was estimated by a chick bioassay method to investigate the mechanism of BHT-induced decreases in the activities of vitamin K-dependent clotting factors. The concentration of vitamin K in the liver of rats receiving BHT was reduced as compared to that of control rats. Conversely, the concentration of vitamin K in the feces from rats receiving BHT increased more than that from control rats. The vitamin K deficiency induced by BHT might be due to effects of BHT on absorption and excretion of vitamin K.

Animals↗
PubMed1983

The role of 2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone (BHT quinone methide) in the metabolism of butylated hydroxytoluene.

Male rats were fed 5.45 mmol/100 g diet butylated hydroxytoluene (BHT) or 2,6-di-tert-butyl-4-hydroxymethylphenol (BHT alcohol) in either a standard or purified diet for 1 wk, after which their livers were analysed for levels of unconjugated BHT metabolites and their blood clotting times were assayed. The BHT quinone methide, 2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone, was only found in appreciable concentrations (6-9 micrograms/g liver) in the livers of rats given BHT. For rats fed the purified diet, BHT and BHT alcohol caused significant reductions of the prothrombin index to 23 and 70%, respectively, of the control value, though rats fed the standard diet were not similarly affected. Liver concentrations of BHT in rats fed BHT alcohol also varied according to diet, indicating that the metabolic pathway may be affected by diet. Biliary excretion of the quinone methide was observed in rats given 140 mg BHT alcohol ip.

Animals↗
PubMed1983

The metabolic profile of sodium o-phenylphenate after subchronic oral administration to rats.

We examined the metabolites of o-phenylphenol (OPP) in the urine of male and female rats dosed with 2% sodium o-phenylphenate (OPP-Na) in food from the age of 5 wk for 136 days. The urinary metabolites of OPP-Na produced during the 24 hr after OPP-Na feeding accounted for 55% of the dose in male rats and 40% in females. The main metabolites were OPP-glucuronide and 2,5-dihydroxybiphenyl (2,5-DHBP)-glucuronide. OPP metabolites in the free form accounted for only 1% of the total phenolic metabolites excreted. 2,5-DHBP was rapidly converted to the corresponding quinone in aqueous solvents but not in organic solvents. There was a clear sex difference in the proportions of urinary metabolites; the amount of 2,5-DHBP excreted by male rats in 24-hr urine was more than seven times that excreted by females. This result may be related to the finding that bladder tumours occur in male but not female rats fed OPP-Na in the diet.

Administration, Oral↗
PubMed1983

Metabolic studies in the rat with 2,4,6-tri-t-butylphenol: a haemorrhagic antioxidant structurally related to butylated hydroxytoluene.

Single oral doses of the haemorrhagic antioxidant 2,4,6-tri-t-butylphenol (260 mg/kg) were well absorbed in the rat. Peak blood levels of this compound were reached in 15-60 min. The blood elimination half-lives were 18.2 min for the alpha-phase and 11.8 h for the slower beta-phase. Max. tissue concns. of this compound were reached 2-3 h in the liver, 2-6 h in kidneys, 1.5-2.5 h in spleen and greater than 24 h in epididymal adipose tissues. This compound and its metabolites were not excreted in the urine; a metabolite but not the parent compound was detected in the faeces. The faecal metabolite had a mol. wt. of 261, and was considered to be 2,4,6-tri-t-butylphenoxy radical. 2,4,6-Tri-t-butylphenoxy radical was also detected in the bile of rats after oral administration of the parent phenol.

Animals↗
PubMed1982

Effects of monoesters of O-phthalic acid on serum lipid composition of rats.

Male rats were administered diets containing monobutyl (MBP), mono-iso-butyl (MIBP), monooctyl (MOP) or mono-2-ethylhexyl phthalate (MEHP) for 1 week, and serum lipid compositions were determined. Non-esterified fatty acid was increased and triglycerides and total cholesterol were decreased in all monoester-treated groups. Fatty acid composition of triglycerides, cholesteryl esters and phospholipids showed similar alteration in the treated groups.

Animals↗
PubMed1982

Toxicity of several phosphoric acid esters in rats.

JCL--Wistar male rats were fed a diet containing 0 or 0.5% of trimethyl phosphate (TMP), triethyl phosphate (TEP), tri-n-butyl phosphate (TBP), trioctyl phosphate (TOP), or tricresyl phosphate (TCP) for 9 weeks. Body weights in TMP- and TBP-treated rats were significantly lower than the control. No differences in toxicity were observed among the test compounds, although there were differences between the treated and control rats in some organ weights, hematological values and serum components.

Animals↗
PubMed1982

The mitochondrial glycine cleavage system: differential inhibition by divalent cations of glycine synthesis and glycine decarboxylation in the glycine-CO2 exchange.

The exchange of glycine carboxyl carbon with CO2 catalyzed by the combination of chicken liver glycine decarboxylase (P-protein) and aminomethyl carrier protein (H-protein) was markedly inhibited by various divalent cations, although extents of inhibition by individual metal ions varied considerably. Cu2+ and Zn2+, at 100 microM, inhibited the reaction almost completely, and the inhibitions by Co2+ and Ni2+ were also significant, while Mg2+ and Mn2+ did not appreciably affect the reaction. The inhibition by Zn2+ was competitive with both bicarbonate and H-protein and non-competitive with glycine. Of the two reactions involved in the glycine-CO2 exchange, decarboxylation of glycine yielding the H-protein-bound aminomethyl moiety was not significantly affected by 100 microM Zn2+ or Cu2+, but carboxylation of the H-protein-bound aminomethyl moiety to form glycine was strongly inhibited by either Zn2+ or Cu2+. Various degrees of inhibition of the glycine-CO2 exchange by other divalent metal ions could also be accounted for by the inhibition of the carboxylation step of the exchange reaction. The primary site of the action of divalent metal ions is likely to be not P-protein but H-protein, and the binding of metal ions with the H-protein-bound intermediate of glycine decarboxylation was assumed to account for the observed marked inhibition.

Animals↗
PubMed1982

The mitochondrial glycine cleavage system: inactivation of glycine decarboxylase as a side reaction of the glycine decarboxylation in the presence of aminomethyl carrier protein.

Glycine decarboxylase, tentatively called P-protein, was inactivated when it was incubated with glycine in the presence of the aminomethyl carrier protein, called H-protein. The inactivation was accompanied by a spectral change in the P-protein as a pyridoxal phosphate enzyme; the spectrum became unusual, with a peak at 330 nm. The fluorescence emission spectrum of the inactivated P-protein showed a distinct peak at 390 nm when excited at 325 nm. Such a spectral change and concomitant inactivation of the P-protein could be completely prevented by the addition of sodium bicarbonate, which initiates the glycine-CO2 exchange in the reaction mixture. The inactivated P-protein was associated with H-protein and the methylene carbon of glycine, but not the carboxyl carbon, in a manner not separable by gel filtration, although the molar ratios of those three components were not constant. The H-protein recovered in the inactivated P-protein fraction was also catalytically inactive. Neither the pyridoxal derivative nor the methylene carbon of glycine appeared to be covalently bound with the protein, and the methylene carbon could be recovered as formaldemethone when treated with dimedone. The inactivation of the P-protein appears to represent a suicide reaction of the P-protein as a side reaction of the glycine decarboxylation, which is supposed to involve the formation of a ternary complex of P-protein, aminomethyl moiety of glycine and H-protein through a Schiff base linkage of the H-protein-bound amino-methyl moiety with the pyridoxal phosphate of P-protein.

Amino Acid Oxidoreductases↗
PubMed1982

Glycine cleavage system in ketotic hyperglycinemia: a reduction of H-protein activity.

Glycine cleavage activity was compared in the livers from three cases of ketotic hyperglycinemia (two cases of propionic acidemia and one case of methylmalonic acidemia) and three controls. In one case of propionic acidemia, glycine cleavage activity (5.2 nmole/mg protein/hr) was normal in the liver obtained at biopsy when the patient was well controlled by the treatment with low protein diet (0.8 g/kg/day) and the level of serum glycine was lowered to normal. In the two other cases of ketotic hyperglycinemia, glycine cleavage activity was significantly reduced in the liver obtained at autopsy when the patients died in the state of metabolic acidosis. Its activity in the liver of one case of propionic acidemia (0.7 nmole/mg protein/hr) was 6-26% of that in controls (2.7-10.8 nmole/mg protein/hr), and 2-7% in the case of methylmalonic acidemia (0.2 nmole/mg protein/hr). Analysing of the individual components of the glycine cleavage system, a marked decrease in the activity of H-protein was revealed in the livers of the both patients; it (0.2 nmole/mg protein/hr) was only 3-4% of that in controls (4.9-6.3 nmole/mg Protein/hr). These findings suggest that the reduction of the glycine cleavage system in the liver of ketotic hyperglycinemia occurs secondarily as speculated previously and is caused mainly by a decrease of H-protein activity.

Acidosis↗