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Biomedical subjects

K Hirota

Publications and source records attributed to K Hirota.

At least 469 records · Page 26Linked to original sources
PubMed1985

Reaction of 2'5'-dichloro-2'5'-dideoxyuridine with nucleophiles.

Reaction of 2',5'-dichlorouridine (1) with amines and thiols afforded 2-N-substituted 2',5'-anhydroisocytidine derivatives (2) and 2,2'-anhydro-5'-thiouridine derivatives (5), respectively. When 2,2'-anhydro-5'-acetylthiouridine (5a) was treated with NaOMe, 3',5'-S-cyclouridine (6) was obtained.

Amines↗
PubMed1984

Ophthalmic and norophthalmic acid in lens, liver, and brain of higher animals.

A sensitive high-performance liquid chromatographic method for the determination of nanomole levels of ophthalmic and norophthalmic acid has been described. The procedure is based upon the conversion of amino group to 2,4-dinitrophenyl derivatives and the detection at 420 nm. This method was applied to the determination of the peptides in lens, liver, and brain of several animals. Mean recoveries were 93.6% for ophthalmic acid and 92.3% for norophthalmic acid added to cattle lens homogenate.

Animals↗
PubMed1984

S-(1,2-dicarboxyethyl)glutathione and S-(1,2-dicarboxyethyl)L-cysteine in lens.

S-(1,2-Dicarboxyethyl)glutathione and S-(1,2-dicarboxyethyl)L-cysteine were determined by high performance liquid chromatography after reaction with 2,4-dinitrofluorobenzene. By this method the former could be determined in the range 4.05 mumol/l-815 mumol/l, and the latter in the range 1.45 mumol/l-1.45 mmol/l. The recovery from cattle lens homogenate was 90.0 +/- 3.2% for S-(1,2-dicarboxyethyl)glutathione and 95.3 +/- 3.1% for S-(1,2-dicarboxyethyl)L-cysteine. Using this method S-(1,2-dicarboxyethyl)-glutathione and S-(1,2-dicarboxyethyl)L-cysteine were determined in lenses of several vertebrates and in rat lens during cataract formation by galactose.

Animals↗
PubMed1983

High-performance liquid chromatographic method for the determination of plasma allantoin.

A new method has been devised for the determination of nanomole levels of allantoin in human plasma. Allantoin was converted into xanthylallantoin, which was chromatographed on a reversed-phase silica gel using a mixture of acetonitrile-water (27:73) as mobile phase. The eluted compound was measured using an ultraviolet detector. The detection limit of the assay for plasma was about 100 ng/ml. This method was applied successfully to the determination of allantoin in human plasma after oral administration of 100 mg of aldioxa.

Adult↗
PubMed1983

One-electron reduction of D-amino acid oxidase. Kinetics of conversion from the red semiquinone to the blue semiquinone.

The reduction of D-amino acid oxidase (DAAO) by hydrated electrons (eaq-) has been studied in the absence and presence of benzoate by pulse radiolysis. The eaq-did not reduce the flavin moiety in DAAO and reacted with the amino acid residues in the protein. In the presence of benzoate, eaq- first reacted with benzoate to yield benzoate anion radical. Subsequently, the benzoate anion radical transferred an electron to the complex of DAAO-benzoate to form the red semiquinone of the enzyme with a second-order rate constant of 1.2 X 10(9) M-1 s-1 at pH 8.3. After the first phase of the reduction, conversion of the red semiquinone to the blue semiquinone was observed in the presence of high concentration of benzoate. This process obeyed first-order kinetics, and the rate increased with an increase of the concentration of benzoate. In addition, the rate was found to be identical with that of the formation of the complex between benzoate and the red semiquinone of DAAO as measured by a stopped-flow method. This suggests that bound benzoate dissociates after the reduction of the benzoate-DAAO complex by benzoate anion radical and that free benzoate subsequently recombines with the red semiquinone of the enzyme to form the blue semiquinone.

Animals↗
PubMed1983

Suppression of cell mediated immunity to cytomegalovirus and tuberculin in pregnancy employing the leukocyte migration inhibition test.

To clarify the mechanism of reactivation of cytomegalovirus (CMV) in pregnancy, cell mediated immunity to CMV was investigated in 108 pregnant and 29 postpartal women employing the leukocyte migration inhibition technique. It was demonstrated that CMV-specific cell mediated immunity was suppressed as gestation progressed in 20% of the seropositive women during the first trimester, in 78% during the second trimester and in all at term. The suppression of cell mediated immunity during pregnancy ceased 8 weeks after parturition. The results suggested that reactivation of CMV in pregnancy was probably caused by the suppression of CMV-specific cell mediated immunity.

Adult↗
PubMed1983

Effects of spinasterol and sitosterol on plasma and liver cholesterol levels and biliary and fecal sterol and bile acid excretions in mice.

Effects of spinasterol and sitosterol on plasma and liver cholesterol levels and biliary and fecal sterol and bile acid excretions were examined with male mice. Both phytosterols were added to the diet at a 1% concentration and fed to mice for 15 days. Spinasterol increased the fecal cholesterol excretion and decreased the plasma and liver cholesterol levels, the bile acid pool size and the fecal bile acid excretion, especially those derived from chenodeoxycholic acid. Fecal coprostanol excretion remained unchanged. These changes were similar to those produced by sitosterol. These data led to the conclusions 1) that spinasterol, as well as sitosterol, inhibits cholesterol absorption, resulting in decreases of the plasma and liver cholesterol levels and 2) that when cholesterol absorption is inhibited, the synthesis of bile acids, especially that of chenodeoxycholic acid, decreases, suggesting that the dietary cholesterol is preferentially metabolized to chenodeoxycholic acid in mice.

Animals↗