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Biomedical subjects

S Horikawa

Publications and source records attributed to S Horikawa.

At least 73 records · Page 4Linked to original sources
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

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

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↗
PubMed1984

Synthesis in vitro of precursor-type carnitine acetyltransferase with messenger RNA from Candida tropicalis.

Carnitine acetyltransferase was synthesized in vitro in the mRNA-dependent reticulocyte system with mRNA from alkane-grown or propionate-grown cells of Candida tropicalis. The protein synthesized in vitro was isolated by immunoprecipitation with antibody against peroxisomal or mitochondrial carnitine acetyltransferase and was compared with peroxisomal carnitine acetyltransferase (Mr of subunits, 64 000 and 57 000) and the mitochondrial enzyme (Mr of subunits, 64 000 and 52 000) of C. tropicalis by electrophoresis in the presence of sodium dodecyl sulfate. Nascent carnitine acetyltransferase prepared in vitro showed a hetero-oligomeric property, like the peroxisomal and mitochondrial enzymes isolated from C. tropicalis. The molecular weights of the subunits of nascent carnitine acetyltransferase were estimated to be 71 000 and 57 000, indicating the existence of the precursor form of the enzyme. By sucrose density gradient centrifugation of total mRNA, these two subunit proteins were shown to be synthesized with respective mRNAs of different sizes. The same precursor-type of carnitine acetyltransferase was obtained with the mRNAs from the alkane-grown cells and the propionate-grown cells. The results obtained suggest that a common precursor will be post-translationally modified to form the peroxisomal and mitochondrial enzymes.

Acetyltransferases↗
PubMed1983

Isolation and sequence analysis of the human corticotropin-releasing factor precursor gene.

A human genomic DNA segment containing the gene for the corticotropin-releasing factor precursor has been isolated by screening a gene library with an ovine cDNA probe. The cloned DNA segment has been subjected to restriction endonuclease mapping and nucleotide sequence analysis. Comparison of the nucleotide sequence of the gene with that of the ovine cDNA indicates that an intron of 800 bp is inserted in the segment encoding the 5'-untranslated region of the mRNA. The segment corresponding to the protein-coding and the 3'-untranslated region of the mRNA is uninterrupted. The mRNA and amino acid sequences of the human corticotropin-releasing factor precursor have been deduced from the corresponding gene sequence. The deduced amino acid sequence of human corticotropin-releasing factor exhibits seven amino acid substitutions in comparison with the ovine counterpart.

Amino Acid Sequence↗
PubMed1982

Cell-free translation and regulation of Candida tropicalis catalase messenger RNA.

To gain information on metabolic control and peroxisome biogenesis in Candida tropicalis growing on n-alkanes, cell-free translation of catalase (H2O2:H2O2 oxidoreductase, EC 1.11.1.6), a general marker enzyme of peroxisomes, was performed. The level of catalase activity in alkane-grown cells was approximately 9-fold and 27-fold higher than that in ethanol-grown and glucose-grown cells, respectively. Immunochemical titration experiments with rabbit antiserum against the purified peroxisomal catalase from alkane-grown C. tropicalis indicated that the remarkable variation in the enzyme activity level on different carbon sources was ascribable to a corresponding change in the amount of the enzyme protein. When cell-free translation was carried out with the mRNA-dependent reticulocyte lysate system, total RNA prepared from alkane-grown cells was shown to direct the synthesis of catalase subunit in vitro. The identity of the cell-free translation product was ascertained by the following evidence: (a) the translation product was immuno-reactive with specific antibody to catalase and competed effectively with the authentic enzyme for immunoprecipitation; (b) it possessed a molecular weight indistinguishable from that of authentic catalase subunit (Mr 54000); (c) its peptide fragments formed by partial digestion with Staphylococcus aureus V8 protease were identical with those from the authentic enzyme. With the use of the cell-free translation system, it was indicated that the significant change in the amount of catalase protein on different carbon sources nearly paralleled that in the activity of the mRNA encoding the enzyme.

Alkanes↗
PubMed1982

Passive enhancement of rat heart allografts by xenogeneic antidonor sera raised in rabbits.

Antilymphocyte serum (ALS) was raised in rabbits immunized by administration of lymphoid cells from Sprague-Dawley (SpD) rats. The ALS was rendered specific for the SpD strain by complete absorption by Wistar rat lymphoid cells. The specificity was considered to be predominantly directed to SpD Ir gene-associated (Ia) antigens, since absorption by SpD erythrocytes failed to abolish lymphocytotoxic activities. Alloantibody production by Wistar rats sensitized with SpD spleen cells was completely inhibited by simultaneous injections of SpD-specific ALS. This effect was specific as normal alloantibody production occurred when Wistar rats were immunized with ACI cells, as a third party. Although this ALS exhibited restricted enhancing ability on skin allograft survival, it was capable of significantly prolonging the survival of heart allografts from SpD to Wistar rats. The ALS showed blocking activities on mixed lymphocyte culture (MLC) but had no effect on cell-mediated cytotoxicity (CMC). The enhancing activity was thus considered to be mediated by an afferent blockage of immune responses.

Absorption↗
PubMed1980

Hemobilia after percutaneous transhepatic biliary drainage.

Hemobilia after the inception of percutaneous transhepatic biliary drainage (PTBD) has been reported as an uncommon, but sometimes fatal, complication. We examined the incidence, pathogenesis, and management of hemobilia in 94 patients who received PTBD. There were seven cases (7.4%) with transient and six (6.4%) with severe hemobilia; one patient (1.1%) of the latter group died. There was no correlation between hemobilia and hemostatic or hepatic insufficiency. Angiography during PTBD was performed in 47 patients, and abnormalities restricted to arterial changes were noted in nine (19.1%). All but one patient with hemobilia showed angiographic abnormalities. Our findings indicate that hemobilia occurs more often than has been suspected and that it is usually due to intrahepatic vessel injury rather than to hemorrhagic diathesis or hepatic insufficiency. The primary management of hemobilia consists of maintaining continuous patency of the drainage catheter.

Adult↗
PubMed1980

Hepatocellular carcinoma in a case of Dubin-Johnson syndrome treated successfully with right extended lobectomy.

A 57-year-old man with hepatocellular carcinoma and liver cirrhosis combined with Dubin-Johnson syndrome was successfully treated by extensive right hepatic lobectomy. While the preoperative serum bilirubin level is one of the criteria in determining the indication for radical hepatic resection, it does not play a decisive role in the case of combined Dubin-Johnson syndrome.

Bilirubin↗