Search PubMed⌕ Search

Biomedical subjects

C Nakayama

Publications and source records attributed to C Nakayama.

At least 73 records · Page 4Linked to original sources
PubMed1983

Partial purification and characterization of DNA-dependent RNA polymerases I and II from cherry salmon (Oncorhynchus masou).

1. DNA-dependent RNA polymerases I and II were purified approx 3900- and 13,000-fold, respectively, from sonicated nuclear extract of cherry salmon (Oncorhynchus masou) liver by DEAE-Sephadex, heparin-Sepharose and DNA-cellulose column chromatography. 2. The purified RNA polymerases exhibited a requirement for four kinds of ribonucleoside 5'-triphosphates, an exogeneous template and divalent cation. 3. The activities of RNA polymerases I and II were inhibited by Actinomycin D (24 micrograms/ml) but not by Rifampicin (200 micrograms/ml). 4. RNA polymerase I preferred native DNA as template, while polymerase II preferred single-stranded DNA. 5. RNA polymerase II was inhibited by a low concentration of alpha-amanitin (0.02 micrograms/ml). RNA polymerase I was also inhibited by the relatively high concentration of alpha-amanitin (IC50 = 100 micrograms/ml and IC70 = 750 micrograms/ml). 6. RNA polymerases from cherry salmon exhibited a higher activity at low temperature than from rat liver.

Amanitins↗
PubMed1982

Computed tomography of mediastinal bronchogenic cysts.

The computed tomographic (CT) findings in seven cases of mediastinal bronchogenic cysts were reviewed. Two showed homogeneous high density masses with CT numbers of 97 and 89 Hounsfield units (HU). One had a CT number of 40 HU. Four cases had low density masses with CT numbers ranging from -3 to 20 HU; however, two of these four low density masses had either high density outer walls or deposits. All but one of the patients' chest radiographs revealed similar water density masses. Radiographic evidence of calcium deposits was previously considered rare, but its demonstration with CT appears to be common in mediastinal bronchogenic cysts.

Adult↗
PubMed1981

Inhibitory effects of 3'deoxycytidine 5'-triphosphate and 3'-deoxyuridine 5'-triphosphate on DNA-dependent RNA polymerases I and II purified from Dictyostelium discoideum cells.

3'-Deoxycytidine 5'-triphosphate and 3'-deoxyuridine 5'-triphosphate were synthesized starting from cordycepin in good yield. The inhibitory effects of these nucleotides were examined in comparison with that of cordycepin 5'-triphosphate (3'-dATP) using purified DNA-dependent RNA polymerases I and II from Dictyostelium discoideum cells. Both nucleotide analogues strongly and competitively inhibited the incorporations of CTP and UTP into RNA by the RNA polymerases. The Km and Ki values for CTP and 3'-dCTP were 6.3 micro M and 3.0 micro M, respectively, and those for UTP and 3'-dUTP were 6.3 micro M and 2.0 micro M, respectively. These two analogues will be useful in studies at the molecular level on the relationship of template and substrate in RNA synthesis with chromatin, isolated nuclei or permeable cells, because they do not have any effect on poly (rA) synthesis.

DNA-Directed RNA Polymerases↗
PubMed1981

Interaction of 1-(5-phospho-beta-D-arabinofuranosyl)-5-substituted-uracils with thymidylate synthetase: mechanism-based inhibition by 1-(5-phospho-beta-D-arabinosyl)-5-fluorouracil.

A number of 1-(5-phospho-beta-D-arabinosyl)-5-substituted-uracils (ara-UMP's) have been examined as inhibitors of dTMP synthetase. As reversible inhibitors, all were substantially less potent than their 2'-deoxyribosyl counterparts. In the presence of 5,10-methylenetetrahydrofolate (CH2-H4folate), ara-FUMP caused a first-order, time-dependent inactivation of the enzyme. At 0 degrees C, kinetic studies indicated a reversible Kd of 3.6 micro M for the ara-FUMP-CH2-H4folate complex, and k = 0.22 min-1 for the subsequent inactivation. Spectral studies of the complex and its behavior toward protein denaturants demonstrate that its structure and stoichiometry are directly analogous to those which have previously been described for FdUMP. The significance of this finding with regard to prodrugs of ara-FU and the potential of ara-FU as a chemotherapeutic agent are discussed.

Arabinonucleotides↗
PubMed1981

Inhibitory effects of 3'-modified UTP analogues on DNA-dependent RNA polymerase I and II purified from cherry salmon (Onchorhynchus masou) liver.

Various 1-beta-D-xylofuranosyl-5-substituted uracil 5'-triphosphates were synthesized and their inhibitory effects on DNA-dependent RNA polymerase I and II, which were purified from cherry salmon (Onchorhynchus masou) liver, were examined. The results were as follows: 1) Xylo UTP and xylo TTP were strongly inhibited for both RNA polymerase I and II. 2) 5-Ethyl, 5-n-propyl and 5-n-butyl derivatives showed little inhibitory effect on RNA polymerase I while RNA polymerase II activity was strongly affected by these derivatives. 3) Four kinds of 5-halogenated derivatives including fluoro, chloro, bromo and iodo substituent inhibited both RNA polymerase I and II in almost same extent. 4) The mode of inhibition was, in all cases, competitive with UTP.

Animals↗