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Biomedical subjects

K Tsukada

Publications and source records attributed to K Tsukada.

At least 253 records · Page 14Linked to original sources
PubMed1987

Effect of actinomycin D on DNA replication and c-myc expression during rat liver regeneration.

In an attempt to elucidate the mechanisms that control the hepatic DNA replication, effect of low doses of actinomycin D on DNA synthesis and c-myc expression during the early stage of liver regeneration was investigated. Small amounts of actinomycin D, in amounts that had no effect on the rate of RNA synthesis in normal rats, were multiple injected at 0, 2 and 4 hours after partial hepatectomy. DNA synthesis and c-myc expression in these rats were compared with those in untreated rats. Hepatic DNA synthesis in the treated rats was delayed about 4 to 6 hours in comparison with control rats. In contrast, time course of c-myc expression in inhibitor treated rats was very similar to that in control rats.

Animals↗
PubMed1987

Detection in situ of active polypeptides of mammalian and T4 DNA kinases after sodium dodecyl sulfate/polyacrylamide gel electrophoresis.

DNA kinase activity of rat liver nuclei was detected in situ after electrophoresis in sodium dodecyl sulfate/polyacrylamide gel containing 5'-hydroxyl nicked DNA as DNA substrate. After renaturation of polypeptides, the gel was incubated with [gamma-32P]ATP and Mg2+. An active polypeptide corresponding to Mr 61,000 was observed as a radioactive band by autoradiography. The intensity of the band was proportional to the amount of the enzyme applied. The active band common to various tissues of rat was observed with the nuclear extracts, indicating that DNA kinase for rat tissue is composed of a single polypeptide of Mr 61,000. In contrast, T4 polynucleotide kinase (Mr = 140,000) showed an active polypeptide band corresponding to the subunit of Mr 33,000.

Animals↗
PubMed1987

Ultrastructure of the relationship between odontoblast processes and nerve fibres in dentinal tubules of rat molar teeth.

Serial ultra-thin sections across tubules were analysed three-dimensionally. There was no difficulty in distinguishing nerve fibres and odontoblast processes. In many tubules, a bundle of naked nerve fibres accompanied the odontoblast process for up to 50 microns located in concavities of the surface of the process (type I relationship). No specialized membrane structures between the plasma membrane of nerves and odontoblast process, such as gap junction or membrane thickening similar to that of synapse, were encountered. In a few tubules, the lamellar cytoplasmic processes of the odontoblast extensively enveloped the terminal part of the nerve fibres (type II relationship). This pattern was found in an animal older than the others in which there were lucent tubules and perhaps arose from peripheral sensory stimuli.

Animals↗
PubMed1987

Effects of glucocorticoids and cycloheximide upon transcription of ribosomal RNA gene in rat liver: application of quantitative S1 nuclease mapping analysis.

The change in the amount of pre-rRNA synthesized in rat liver was examined by S1 nuclease mapping analysis using the probe containing the 5' end of the rat 45S rRNA gene. It was found that the amount of pre-rRNA of adrenalectomized rats, which was about half of the normal level, was increased after administration of dexamethasone attaining to the normal level at 12 h, and that the hormone-induced pre-rRNA synthesis was completely abolished within 1 h after injection of cycloheximide. These results indicate that the glucocorticoids-stimulated initiation of rRNA transcription is mediated by the hormone-dependent short-lived protein(s).

Animals↗
PubMed1987

Relative activities of thymidylate synthetase and thymidine kinase in 1,2-dimethylhydrazine-induced colon carcinomas in rats.

Thymidylate synthetase (TS) and thymidine kinase (TK) are known to catalyse the methylation of dUMP for the de novo synthesis of dTMP and the phosphorylation of thymidine for the salvage synthesis of dTMP in the pyrimidine pathway, respectively. High TS and TK activities and the existence of TK isozymes have been observed in rapidly proliferating tissues. TS and TK activities in 1,2-dimethylhydrazine (DMH)-induced colon carcinomas in rats increased significantly to 331 and 207% of the activities in normal colon, respectively, and were well correlated inversely (y = -0.93x + 5.24), with a correlation coefficient of -0.787. The colonic TK isozymes were separated into two types by DEAE-cellulose column chromatography. The TK isozyme eluted from the column by the elution buffer alone without NaCl was markedly higher (23.6-fold) in activity in DMH-induced colon carcinoma than in normal control colon and was not affected by deoxycytidine triphosphate. This isozyme, whose mol. wt is 100,000 by h.p.l.c., is thought to be closely involved in rapid DNA replication. These results indicate that early biochemical changes in DMH-induced colon carcinoma in rats may serve as a useful model and provide valuable insight into the mechanisms involved in colonic carcinogenesis.

1,2-Dimethylhydrazine↗
PubMed1987

Alteration in the ribonucleic acids in rat liver induced by a methionine-free total parenteral nutrition solution.

The effect of infusion of a methionine-free total parenteral nutrition solution for 7 d on ribonucleic acids in liver of rats were investigated. The control solution contained leucine, valine, isoleucine, lysine, phenylalanine, threonine, tryptophan, arginine, histidine, glycine, methionine, glucose and vitamins and minerals. Deprivation of a methionine is known to increase the activity of RNA polymerase I. Infusing the methionine-free solution resulted in the accumulation of RNA molecules larger than 28S in the liver nuclei and resulted in a higher rate of rRNA synthesis than in rats infused with the control solution. A methionine deficiency did not impede either the processing of 45S pre-rRNA or transport of 28S and 18S rRNA into cytoplasm. When rats were infused with the methionine-free solution for 7 d followed by the control solution for 2 d, the level of RNA in the nucleus as well as the rate of RNA polymerase I were similar to the levels in rats receiving the control solution for 9 d. There were no significant changes in the rate of DNA synthesis due to nutritional manipulations.

Animals↗
PubMed1987

Influence of polyethylene glycol on the ligation reaction with calf thymus DNA ligases I and II.

High concentrations of the nonspecific macromolecule polyethylene glycol 6000 (PEG 6000) enabled DNA ligases I and II from calf thymus to catalyze intermolecular blunt-end ligation of duplex DNA. Intermolecular cohesive-end ligation with these enzymes was markedly stimulated in the presence of 10-16% (w/v) PEG 6000. The effect of PEG 6000 (4-16%) on the sealing of single-stranded breaks in duplex DNA with DNA ligases I and II was not appreciably stimulatory but rather inhibitory. PEG 6000 (15%) enhanced more twofold the rate of DNA ligase II-AMP complex formation, but moderately suppressed the rate of formation of DNA ligase 1-AMP complex. Polyamines and KCl inhibited blunt-end and cohesive-end ligations with DNA ligases I and II in the presence of PEG 6000.

Animals↗
PubMed1987

Cases with familiar amyloid neuropathy starting of the upper limbs and having hepatic disorder.

Here we are reporting two cases consisting of a male patient and his elder sister from Kagashima in Gifu City and both suffering from polyneuropathy of dissociation type and skin amyloidosis. In the former, the presence of amyloid was demonstrated not only in the skin, but also in the stomach, liver and gums. He was also diagnosed suffering from chronic hepatitis of inactive type. He responded to DMSO and Cepharanthin. In the patients, no urinary Bence Jones protein nor blood M component was detected and the amyloid exhibited resistance to potassium permanganate treatment. The neuropathy of the patients were slightly different from that of the Portuguese type which starts on lower extremities as well as those conventionally have been reported in Japan.

Adult↗
PubMed1987

Change in the amount of rRNA precursor synthesized in rat ventral prostates after administration of androgen and cycloheximide: application of quantitative S1 nuclease mapping.

The change in amount of pre-rRNA was observed by the use of total cellular RNA isolated from rat ventral prostates and quantitative S1 nuclease mapping. The amount of pre-rRNA from castrated rats was about 20% of that of normal rats, and increased to the normal level 24h after administration of testosterone. Cycloheximide caused a rapid decrease in the amount of pre-rRNA in normal and testosterone-treated castrated rats, to about 20% and 10% of that of normal rats, respectively, 2h after the administration of the drug. These results support the view that the androgen-stimulated initiation of the rRNA gene transcription is mediated by a hormone-dependent short-lived protein(s).

Animals↗
PubMed1986

A protein-tyrosine kinase in the nuclear matrix from rat liver.

Protein kinase activity in isolated nuclei from rat liver was detected in situ after electrophoresis on SDS-polyacrylamide gel containing no exogenous protein substrate. After renaturation of polypeptides, the gel was incubated with [gamma-32P]ATP and divalent cations. Among five major protein kinase activities observed as radioactive bands by autoradiography, a protein kinase autophosphorylating on tyrosine (Mr 30,000) was identified and found to be localized in the nucleus, particularly in the nuclear matrix. The intensity of the activity band representing the level of the protein-tyrosine kinase in rat liver nuclei did not appreciably change during 3-24 h after partial hepatectomy.

Animals↗
PubMed1986

Expression of c-myc oncogene in rat liver by a dietary manipulation.

After rats deprived of protein for several days are fed a meal containing protein, hepatic DNA replication is induced. When nuclear DNA synthesis is stimulated in the normally quiescent rat liver by a dietary manipulation, we examined the changes of the steady-state levels of messenger RNA for c-myc. Levels of c-myc mRNA are gradually elevated approximately 4 to 5-fold above normal in the livers of rats that are fed for several days a diet that lacks protein. After a nutritional shift from a protein-free diet to a diet containing 50% casein, the levels of c-myc mRNA decrease rapidly by 2 h and returned to approximately basal levels after 8 h. Our results suggest that c-myc expression during the prereplicative stage of liver is likely to reflect events associated with entry and progression of hepatocytes into the cell cycle.

Animals↗
PubMed1986

Immunochemical analysis of molecular forms of mammalian DNA ligases I and II.

Using specific antibodies against calf thymus DNA ligases I and II (EC 6.5.1.1), we have investigated the polypeptide structures of DNA ligases I and II present in the impure enzyme preparations, and estimated the polypeptides of DNA ligases I and II present in vivo. Immunoblot analysis of DNA ligase I after sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a 130-kDa polypeptide as a major one in the enzyme preparations from calf thymus throughout the purification. In addition to the 130-kDa polypeptide, a 200-kDa polypeptide was detected in the enzyme preparations at the earlier steps of the purification, and a 90-kDa polypeptide was observed as a minor one in the enzyme preparations at the later steps of the purification. The polypeptides with molecular weight of 130 000 and 90 000 were detected by SDS-polyacrylamide gel electrophoresis of DNA ligase I-[3H]AMP complex. These results suggest that a 200-kDa polypeptide of DNA ligase I present in vivo is degraded to a 130-kDa polypeptide and then to a 90-kDa polypeptide during the isolation and purification procedures. On the other hand, the monospecific antibody against calf thymus DNA ligase II cross-reacted with only a 68 kDa polypeptide in the enzyme preparations throughout the purification, suggesting that the 68-kDa polypeptide is a single form of calf thymus DNA ligase II present in vivo as well as in vitro.

Animals↗
PubMed1986

Tripolyphosphatase associated with S-adenosylmethionine synthetase isozymes from rat liver.

S-Adenosylmethionine (AdoMet) synthetase alpha and beta were purified to homogeneity, as judged by SDS-polyacrylamide gel electrophoresis from rat liver. When the purified enzymes were applied onto Sephacryl S-200, each synthetase was eluted together with a tripolyphosphatase. The activities of these isozymes in synthesizing AdoMet and in hydrolyzing tripolyphosphate decreased in parallel with increasing amounts of rabbit anti-(beta-form) IgG. The activity of the beta-form isozyme was markedly stimulated by the addition of tripolyphosphate, whereas that of the alpha-form isozyme was inhibited. The tripolyphosphatase activity of both the alpha- and the beta-form was markedly stimulated by the addition of AdoMet. The tripolyphosphatases of each isozyme showed some other similar properties.

Acid Anhydride Hydrolases↗
PubMed1986

Induction of S-adenosylmethionine synthetase isozymes in primary cultures of adult rat hepatocytes.

The activities of S-adenosylmethionine synthetase isozymes were studied using adult rat hepatocytes in primary culture. Hepatocytes from adult rats were isolated and cultured for several days. The activities of the synthetase isozymes did not change during primary culture. The activity of the alpha-form increased with increasing ethionine plus adenine or methionine in the medium, and reached about 5 fold after 2 days. However, the increased activity of the beta-form showed less than twice.

Adenine↗
PubMed1986

Purification of DNA ligase II from calf thymus and preparation of rabbit antibody against calf thymus DNA ligase II.

DNA ligase II has been purified about 4,000-fold to apparent homogeneity from a calf thymus extract. The ligase consists of a single polypeptide with a molecular weight of 68,000 as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. On fluorography after electrophoresis, a DNA ligase-[3H]AMP complex gave a single band corresponding to a molecular weight of 68,000. The Km values of the ligase for ATP and nicked DNA (5'-phosphoryl ends) were obtained to be 40 and 0.04 microM, respectively. Antibody against calf thymus DNA ligase II was prepared by injecting the purified enzyme into a rabbit. The antibody cross-reacted with DNA ligase II but not with calf thymus DNA ligase I. DNA ligase II was not affected by antibody against calf thymus DNA ligase I with a molecular weight of 130,000 (Teraoka, H. and Tsukada, K. (1982) J. Biol. Chem. 257, 4758-4763). These results indicate that DNA ligase II (Mr = 68,000) is immunologically distinct from DNA ligase I (Mr = 130,000).

Animals↗