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N Kitahara

Publications and source records attributed to N Kitahara.

At least 37 records · Page 2Linked to original sources
PubMed1982

Effect of ribonuclease H from chick embryo on the covalent-linked poly(A)--poly(dA) complementary to poly(dT) template.

In vitro poly(dA) synthesis on poly(dT) template can be initiated by poly(A) primer. Poly(A) chains are covalently extended by DNA polymerase. The reaction product consists of poly(dA) chain with poly(A) at their 5'-ends, hydrogen bonded to the template poly(dT). The primer poly(A) is linked to the product poly(dA) via a 3':5'-phosphodiester bond, and can be specifically removed by ribonuclease H from chick embryos, leaving a 5'-phosphate end of poly(dA). Poly- or oligoriboadenylate longer than the (pA)5 could serve as a priming activity to synthesize poly(A) covalently linked to poly(dA).

Animals↗
PubMed1982

Depside as potent inhibitor of prostaglandin biosynthesis: a new active site model for fatty acid cyclooxygenase.

Forty depsides and depsidones, the esters of phenolcarboxylic acids, were examined for their inhibitory effect against prostaglandin biosynthesis with rabbit renal microsomes. 4-0-Methylcryptochlorophaeic acid was the most active inhibitor so far tested and its IC50 value was 0.34 muM. Kinetic investigation has shown that this depside acts competitively with respect to arachidonic acid as most of the non - steroidal antiinflammatory drugs. X-Ray analysis has revealed that 4-0-methylcryptochlorophaeic acid maintains its rigid conformation by forming a strong hydrogen bond between the hydroxyl and methoxyl groups. Comparison of CPK models between 4-0-methylcryptochlorophaeic acid and non-steroidal antiinflammatory drugs revealed that the carboxyl group and the two rings of these drugs are almost superimposable to those of the depside. This finding led us to propose a new active site model based on the three dimentional structure of the depside.

Animals↗
PubMed1982

Purification and properties of magnesium- and manganese-dependent ribonucleases H from chick embryo.

Two RNases H, Mg2+- and Mn2+-dependent RNases H, are present in extracts of chick embryo. These RNases H can be separated by phosphocellulose column chromatography. Mg2+-dependent RNase H was purified over 900-fold and Mn2+-dependent RNase H over 1,700-fold from chick embryo extracts. The molecular weight of the purified Mg2+-dependent RNase H was about 40,000 and of the Mn2+-dependent RNase H about 120,000, when estimated by gel filtration. Mg2+-dependent RNase H exhibits maximal activity at pH 9.5, and requires 15 to 20 mM Mg2+ for maximal activity, whereas Mn2+-dependent RNase H is most active at pH 8.5, and is maximally active at the concentration of 0.4 mM Mn2+, and has some activity with Mg2+. Both enzymes require a sulfhydryl reagent for maximal activity. Mn2+-dependent RNase H was inhibited by o-phenanthroline, pyrophosphate, and those polyamines tested, whereas Mg2+-dependent enzyme was not, although it was inhibited by NaF. Both RNases H liberate a mixture of oligonucleotides with 5'-phosphate and 3'-hydroxyl termini endonucleolytically.

Ammonium Sulfate↗
PubMed1981

Nuclear location of ribonuclease H and increased level of magnesium-dependent ribonuclease H in rat liver on thioacetamide treatment.

Rat liver nuclei were isolated in aqueous solutions of low ionic strength or anhydrous glycerol. The presence of ribonuclease H (RNase H) [EC 3.1.4.34] activity in the cytoplasm is due to extraction of the nuclear enzyme by buffer and inorganic salts. Two forms of RNase H were separated from rat liver nuclei by affinity chromatography using a DNA-cellulose column. When the RNase H in the wash solution of nuclei with 0.3 M sucrose and in nuclear solution extracted with 0.15 M NaCl were fractionated on a single-stranded DNA-cellulose column, two peaks corresponding to Mn2+- and Mg2+-dependent RNases H were eluted at 0.1 M and 0.2 M NaCl, respectively, and a peak having both RNase H activities was recovered in the wash-through fraction from the column. Among the enzymes from these two fractions in the nuclei, the activity of the Mg2+-dependent RNase H which binds to DNA-cellulose increased several-fold within 24 h of a single injection of thioacetamide. The activities of Mg2+-dependent RNase H extracted with higher-salt solution from the nuclei and recovered in the flow-through fraction from the DNA-cellulose column and the Mn2+-dependent RNase H activities were relatively unaffected by an injection of thioacetamide.

Acetamides↗
PubMed1981

Inhibition of brain glutamate decarboxylase by 4,5-dihydroxyisophthalic acid and related compounds.

Hydroxybenzoic and phthalic acids and their related compounds were tested for inhibitory activity to brain glutamate decarboxylase. Of mono-, di-, and trihydroxybenzoic acids, gallic acid was the most inhibitory, giving 50% inhibition at a concentration of 0.17 mM. Dihydroxybenzoic acids were less inhibitory than the trihydroxyacids but more than monohydroxybenzoic acids. Of the phthalic acid-related compounds tested, 4,5-dihydroxyisophthalic acid was the most potent inhibitor, producing 50% inhibition at 0.61 microM. The inhibition of these compounds was competitive with respect to L-glutamate. The Ki values were 0.02, 1.2 and 4.9 microM for 4,5-dihydroxyisophthalic acid, 5-hydroxyisophthalic acid and gallic acid, respectively. When administered intraventricularly to mice, 4,5-dihydroxyisophthalic acid produced a significant decrease in the gamma-aminobutyric acid content of the brain, resulting in induction of convulsions.

Animals↗
PubMed1981

Xanthocillin X monomethyl ether, a potent inhibitor of prostaglandin biosynthesis.

Xanthocillin X monomethyl ether, known as an antiviral antibiotic, was isolated as a potent inhibitor of Dichotomomyces cejpii. The compound inhibited prostaglandin synthesis from 14C-arachidonic acid in rabbit kidney microsomes by 50% at a concentration of 0.2 microM, while prostaglandin synthesis by microsomes of ram seminal vesicle was inhibited by 50% at 20 microM. The inhibition of xanthocillin X monomethyl ether was reversible. Of the enzymatic steps involved in the synthesis of prostaglandins and thromboxanes tested, conversion of arachidonic acid into prostaglandin H2 was specifically inhibited by xanthocillin X monomethyl ether. Anti-inflammatory activity of this antibiotic on carrageenan-induced oedema in the rat foot was, however, not detectable.

Animals↗
PubMed1981

Thielavin A and B, new inhibitors of prostaglandin biosynthesis produced by Thielavia terricola.

Two potent inhibitors of prostaglandin biosynthesis, thielavin A (C31H34O10) and B (C29H30O10), were isolated from cultures of Thielavia terricola. Both of these compounds were shown to be structurally related to depsides, thus consisting of three hydroxybenzoic acid groups. Concentrations required for 50% inhibition of the conversion of 14C-arachidonic acid into prostaglandins F2 alpha plus E2 by microsomes of ram seminal vesicles were 12 microM for thielavin A and 9 microM for thielavin B, respectively. Of the enzymatic steps involved in prostaglandin synthesis, thielavin A specifically inhibited the conversion of arachidonic acid into prostaglandin H2, while prostaglandin E2 synthesis from the endoperoxide was the most sensitive to thielavin B. Thromboxane A2 synthesis from prostaglandin H2 in bovine platelet microsomes were inhibited by 50% at concentrations of 150 and 350 microM of thielavin A and B, respectively. Thielavin B was significantly effective on carrageenan-induced oedema of rats when administered intravenously but on on oral administration. The anti-inflammatory activity was not detectable with thielavin A either on intravenous injection or on oral administration.

Animals↗
PubMed1978

Isolation of 4.5-dihydroxyisophthalic acid an inhibitor of brain glutamate decarboxylase, produced by a Streptomyces species.

A potent inhibitor of brain glutamate decarboxylase (L-glutamate 1-carboxy-lyase, EC 4.1.1.15) was isolated from cultures of a Streptomyces species, and its structure was found to be 4,5-dihydroxyisophthalic acid. The metabolite inhibited beef brain glutamate decarboxylase 50% at a concentration of 0.12 microgram/ml (0.61 micron). The kinetic analysis indicated that 4,5-dihydroxyisophthalic acid was a competitive inhibitor having a Ki value of 0.18 micron.

Animals↗
PubMed1976

Herbicidins A and B, two new antibiotics with herbicidal activity. I. Producing organism and biological activities.

Herbicidins A and B, two new antibiotics with selective and contact herbicidal activity, were produced by a new species of Streptomyces designated as S. sagononensis. Among tested microorganisms, herbicidins indicated some activity against fungi in vitro and Xanthomonas oryzae in vivo. Their characteristic features were brought into relief by their selective and contact killing effect on many dicotyledonous plant as well as their inhibition of germination of the plant seeds, such as Chinese cabbage.

Animals↗
PubMedDate not supplied

Diagnosis and physiopathology of laryngeal deposits in autoimmune disease.

We report the clinical features and pathology of a previously unreported form of vocal fold disease seen in 4 patients, 3 of whom were diagnosed as autoimmune disease. The characteristic features of these lesions were found as bilateral transverse lesions in the mid portion of the vocal folds. The patients had dysphonia and diplophonia. Stroboscopic examinations showed 180-degree phase shifts between the anterior and posterior portion of the vocal folds. Case 1 had systemic lupus erythematosus, case 2 had Hashimoto's thyroiditis, and case 3 had progressive systemic sclerosis. Prior to the onset of hoarseness, autoimmune antibody titers were increased. These cases need differential diagnosis from vocal fold nodules and cysts. Two cases were recurrent after endoscopic surgery, 1 recurring 3 times. Glucocorticoid was effective in preventing the recurrence in the early phase. Recurrence may have occurred because the surgical strategy was the same as that used for vocal fold nodules or cysts.

Adult↗