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Biomedical subjects

Y Higashi

Publications and source records attributed to Y Higashi.

At least 235 records · Page 13Linked to original sources
PubMed1990

In vitro inhibition by ketoconazole of human testicular steroid oxidoreductases.

An oral antimycotic agent, ketoconazole has been demonstrated to be an inhibitor of cytochrome P-450-dependent monooxygenases. To investigate its effect on steroid oxidoreductases, in vitro studies were carried out using subcellular fractions of human testes. Ketoconazole competitively inhibited activities of 3 beta-hydroxy-5-ene-steroid oxidoreductase/isomerase and NADH-linked 20 alpha-hydroxysteroid oxidoreductase for steroid substrate and the Ki values were 2.9 and 0.9 microM, respectively. In contrast, ketoconazole inhibited neither 17 beta-hydroxysteroid oxidoreductase nor NADPH-linked 20 alpha-hydroxysteroid oxidoreductase, indicating that the two 20 alpha-hydroxysteroid oxidoreductases are distinct. Further, ketoconazole inhibited non-competitively the above enzyme activities for the corresponding cofactors of NAD and NADH. From the binding mode of ketoconazole to cytochrome P-450 and the present findings, it appears likely that the agent binds to a site which is different from that of steroids or pyridine nucleotides.

20-Hydroxysteroid Dehydrogenases↗
PubMed1990

Inhibitory effect of testosterone on gap junctional intercellular communication of human transitional cell carcinoma cell lines.

A dye transfer method was applied to investigate the effect of testosterone on gap junctional intercellular communication (IC) of two kinds of human transitional cell carcinoma cell lines, JTC-30 and JTC-32. When JTC-30 cells were cultured with testosterone at nontoxic concentrations (17-69 microM), a dose and time dependent inhibition of dye transfer was observed. More than 90% inhibition occurred after exposure to 69 microM testosterone for 96 h. The inhibition was reversed rapidly after testosterone deprivation. Similar results were obtained with JTC-32 cells. 17 beta-Estradiol showed no inhibitory effect on IC of both transitional cell carcinoma cell lines even at toxic levels. Testosterone exhibited no inhibitory effect on IC of human fibroblasts. The inhibitory effect of 5 alpha-dihydrotestosterone was almost similar to that of testosterone. At concentrations examined, cyproterone acetate influenced neither dye transfer nor the inhibitory effect of testosterone, suggesting a mechanism of testosterone action different from that of the known receptor system. Since blockage of IC has been indicated as one reliable evidence for tumor promotion, current results suggest that testosterone is a possible endogenous promoter of the bladder carcinoma and may therefore possibly play a role on the sexually different incidence of bladder carcinoma.

Carcinoma, Transitional Cell↗
PubMed1990

Immunohistochemical demonstration of nuclear S1 proteins in various cells.

S1 proteins are present in the nuclear structures sensitive to DNases and RNase. To examine localization of these proteins, an antibody was raised in a rabbit. Indirect immunofluorescence staining revealed that S1 proteins located in the extranucleolar nuclear regions of quiescent myocardial and cerebellar cells as well as actively duplicating mouse 3T3 fibroblasts. They located in euchromatin regions of thymus lymphocytes, with a characteristic aster-like immunofluorescence pattern, and on the border of condensed chromatin areas by deposition of immunogold particles in ultrathin sections of thymus. Thus, S1 proteins may be in a nuclear function assigned to the border of heterochromatin areas, and other than synthesis of DNA or of ribosomal RNA. Possible involvement of S1 proteins in the extranucleolar RNA synthesis is discussed.

Animals↗
PubMed1990

Two splenic soluble tyrosine kinases from the rat.

Tyrosine kinase was extracted from rat spleen. Some 60% of the activity with angiotensin as the substrate was found in the cytoplasmic supernatant obtained at 100,000g. Two kinases in the supernatant, TKI and -II were purified 170- and 600-fold, respectively, by column chromatography. The molecular weights of TKI and -II were estimated to be 38,000 and 30,000 by Sephacryl S-200 gel filtration, and to be 42,000 and 36,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Experiments with various protease inhibitors suggested that these kinases were not the artifacts of proteolysis. Both kinases autophosphorylated their tyrosine residues. They had different Kms for angiotensin II, and for ATP, but similar dependencies on temperature and on divalent metal ions.

Animals↗
PubMed1990

Possible mechanism of gastric mucosal protection by epidermal growth factor in rats.

The mechanism of the protection by human epidermal growth factor (hEGF) against the gastric mucosal lesions induced by acidified ethanol was studied in rats. At different times following the subcutaneous administration of hEGF (30 micrograms/kg), intragastric acidified ethanol (EtOH: 0.125 M HC1 = 50:50 v/v%) was administered to induce an experimental gastric mucosal lesion. Mean length of the lesion in the gastric mucosa was used as a lesion index. Extravasation of intravenously injected Evans blue into the gastric wall and gastric contents was used as an indicator of vascular permeability. Pretreatment with hEGF decreased both the gastric mucosal lesions and the increase of vascular permeability caused by acidified ethanol with similar time profiles relative to pretreatment with hEGF. Maximal protective actions of hEGF occurred about 10 to 30 min after the observed peak plasma concentration of hEGF. Indomethacin and N-ethylmaleimide, but not iodoacetamide, blocked the protective action of hEGF, indicating that endogenous prostaglandins and/or sulfhydryls may participate in the protective action of hEGF. The content of endogenous nonprotein sulfhydryls in the gastric mucosa decreased markedly after acidified ethanol. However, pretreated hEGF did not restore the sulfhydryl contents. Thus, it seemed that endogenous prostaglandins, but not sulfhydryls, are the probable mediators for protection against gastric mucosal injury caused by acidified ethanol.

Animals↗
PubMed1990

Protective effect of human epidermal growth factor against the experimental gastric mucosal lesions in rats.

The protective effect of human epidermal growth factor (hEGF) on the gastric mucosal lesions in rats was examined in relation to the immunoreactive concentration of plasma. Human EGF (30 micrograms/kg) was administered intravenously, intraperitoneally or subcutaneously. At different times following the administration of hEGF, rats received acidified ethanol solution to induce an experimental gastric mucosal lesion. Sum of lesion length in the gastric mucosa was used as a lesion index. Human EGF administered parenterally markedly decreased the gastric mucosal lesions in 10 min after administration of necrotizing solution, and 10 to 30 min delay was observed in the development of maximal protective action. Profiles of protective potency against the hEGF dose administered intraperitoneally or subcutaneously 30 min before administration of necrotizing solution revealed that the effective dose of hEGF (ED50) was about 5.2 and 2.6 micrograms/kg, for intraperitoneal and subcutaneous administrations, respectively.

Animals↗
PubMed1990

Phosphatidylserine as a determinant for the tissue distribution of weakly basic drugs in rats.

Interogan variation in tissue distribution of weakly basic drugs such as quinidine, propranolol, and imipramine was investigated as a function of binding to phosphatidylserine (PhS) in tissues. Tissue distributions of these drugs were determined using 10 different tissues at a steady-state plasma concentration and were expressed as tissue-to-plasma partition coefficients (Kp values). The concentration of PhS in the tissue was determined by two-dimensional thin-layer chromatography. Plotting of Kp values, except for brain, against the tissue PhS concentrations showed a linear relationship, indicating that PhS is a determinant in the interorgan variation of these tissue distributions. Further, differences in tissue distribution among the drugs was considered to be due to the difference in binding potency to PhS. Drug binding parameters to individual standard phospholipid were determined using a hexane-pH 4.0 buffer partition system. Binding was highest to PhS, and a linear relationship was found between the log nK [product of the number of binding sites (n) and the association constant (K) for PhS binding] obtained in vitro and Kp values of drugs in tissues in vivo. The empirically derived equation, Kp = 14.3 x (log nK) x (PhS conc.) - 8.09, was found to predict Kp values in vivo of weakly basic drugs. Thus, a determinant of interorgan variation in the tissue distribution of the weakly basic drugs studied was the tissue concentration of PhS and the drug binding affinity to PhS.

Animals↗
PubMed1990

An antibody to S1 proteins from rat liver.

S1 proteins (A, B, C and D) are a group of nuclear proteins, isolated by lowering pH to 4.9 of the reaction supernatant of hepatocyte nuclei that had been mildly digested with DNase I. Protein B, apparently ubiquitous in vertebrate cells, was prepared from rat liver and used to immunize a rabbit. The raised antiserum specifically reacted with S1 proteins; it reacted not only with protein B, but also with C and D. Immunoblotting demonstrated that these proteins occurred exclusively in the nucleus, being absent in the cytosol, microsome and mitochondrial fractions. Indirect immunofluorescence of liver tissue sections confirmed their nuclear localization, and further showed that the antibody selectively stained extranucleolar regions of the cell nucleus. These findings suggest that the anti-S1 antibody is specific to S1 proteins and may be useful for their structural and functional studies.

Animals↗
PubMed1990

Functional expression of microsomal and mitochondrial cytochrome P-450 (d and SCC) in COS-7 cells from cloned cDNA.

Using full length cDNA introduced into COS-7 cells, two species of P-450 with entirely different physiological functions have been expressed in enzymatically active form. One is P-450d, which is known to reside in the microsomes of rat hepatocytes where it acts as a drug-metabolizing enzyme; the other is P-450(SCC), which catalyzes the conversion of cholesterol to pregnenolone in the rate-limiting reaction of steroidogenesis in mitochondria of adrenal cortex cells. Northern blot and immunoblot analyses revealed that the mRNA and protein of these P-450 species were efficiently produced in COS-7 cells. The protein contents amounted to nearly 0.1% of the total cell protein as estimated from immunoblotting and low temperature CO difference spectra. The subcellular localization of the products indicated that they were correctly sorted to the microsomes and mitochondria, respectively. We have succeeded in eliciting most of the activity of the expressed microsomal P-450d by reconstruction with NADPH-cytochrome P-450 reductase, while the optimal conditions for the mitochondrial enzyme in the COS cells remain to be studied. These results show the applicability of the COS-7 expression system to investigations of the functions of members of the P-450 superfamily whose cDNA has been newly isolated.

Animals↗
PubMed1990

Dose-dependent pharmacokinetics and first-pass metabolism of acetaminophen in rats.

In order to investigate the in vivo first-pass metabolism of acetaminophen (AAP) following the oral and intraduodenal administration in rats, a pharmacokinetic compartment model including absorption process was developed. Using the parameters for the disposition kinetics of AAP and its metabolites, sulfate and glucuronide, which were determined in the separate study, the extent of the first-pass metabolism and the contribution of sulfation and glucuronidation to the total first-pass metabolism in vivo were quantitatively estimated. As for the results, the first-pass metabolism of AAP following the oral and intraduodenal administration was mainly attributable to the sulfo-conjugation pathway in rats. The sulfation of AAP in the intestine and/or in the liver during the first-pass was proved to be a saturable process. Then, the sulfation in the first-pass metabolism showed the dose- and absorption rate-dependent kinetics. Thus, the pharmacokinetic model including the absorption process proposed in the present study was proved to be valid and useful for the estimation of in vivo first-pass metabolism of AAP in rats.

Acetaminophen↗
PubMed1990

[A study of cytokeratin in human normal bladder epithelium and bladder carcinoma cell lines].

Normal epithelial and carcinoma cells of human bladder were investigated for the cytokeratin which is one of the intermediate filaments and comprises cytoskeleton using the immunofluorescence method. Carcinoma cell lines used were JTC-30, JTC-32, HUB-41 and T-24. In normal urothelium, keratin fibers were fine and straight with unchanged diameter and distributed regularly in the cytoplasm. By contrast, keratin fibers in bladder carcinoma cells were kinked and changed in diameter and were distributed irregularly in the cytoplasm. The above findings were most obvious in T-24 which formed undifferentiated carcinoma when transplanted to nude mice, and keratin fibers were dominantly located in the perinuclear area. The changes of keratin fibers appeared to be parallel to the grade of histological anaplasia of the tumor formed by implantation of bladder carcinoma cell line cells to nude mice. These observations suggest that the morphology of cytokeratin is a useful indicator for evaluating the grade of malignancy in transitional cell carcinoma.

Animals↗
PubMed1990

[A mitochondrial encephalomyopathy due to partial cytochrome c oxidase deficiency with giant evoked potentials--a case report].

A case of mitochondrial encephalomyopathy with a partial cytochrome c oxidase deficiency was reported with special reference to electrophysiological studies. A 56-year-old man was readmitted to Himeji Central Hospital due to mental deterioration and character change. At the age of 44 when he was attacked by his first epileptic seizure, he was admitted to Himeji Central Hospital, where EEG abnormalities and cerebral atrophy were found. Anticonvulsants helped to relieve his generalized convulsions but the EEG abnormalities persisted. At age 46, he had the second generalized seizure, so he quit his job as a crane operator. His family began to notice deterioration of his intellectual function and hyperaggressive behavior. His daily activities, intellectual performance and mental condition gradually deteriorated (WAIS FIQ less than 60). Other clinical and laboratory findings are as follows: bilateral impaired hearing, no optic nerve atrophy, no disturbance of extra ocular muscle movements, mild wasting and weakness of his extremities, normal coordination and sensation, no myoclonus or other involuntary movements, normal laboratory data of serum creatinine kinase, lactate dehydrogenase and aldolase, and increased amount of lactate and pyruvate in serum and cerebrospinal fluid (CSF), no abnormal amino acids in urine. A biopsy specimen of right biceps brachii muscle revealed numerous ragged-red fibers in frozen sections stained by the Gomori trichrome method. These fibers did not react to a cytochrome c oxidase staining. An ATPase staining demonstrated an atrophy of type-2 fibers. An electron micrograph showed many mitochondria in the sarcoplasm but few paracrystalline inclusions. A biochemical analysis of the muscle biopsy also revealed a significant decrease in the cytochrome c oxidase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain Diseases↗
PubMed1990

Prognostic significances of estrogen and progesterone receptors in primary operable breast cancer.

Both estrogen and progesterone receptors have been determined in 613 primary breast cancer patients treated by radical mastectomy. At the cut-off value of 5 fentomoles (fmol) cytosol protein/mg for both receptors, patients with estrogen or progesterone receptor-positive breast cancer showed significantly favorable disease-free, overall and post-recurrence survival curves to those of receptor-negative breast cancer patients. In the patient subgroups: premenopausal, stage III, more than four positive lymph node metastases, postoperative adjuvant tamoxifen therapy, a significantly favorable prognosis was recognized in either estrogen or progesterone receptor-positive patients. Both receptors are thought to be useful prognostic indicators for patients with advanced tumors or for those receiving postoperative adjuvant tamoxifen therapy. When the cut-off value was changed, the maximum significant difference in prognosis between receptor-positive and receptor-negative patients was observed at 5 fmol cytosol protein/mg for the estrogen receptor or 10 fmol/mg cytosol protein for the progesterone receptor. A more detailed examination should be made on the cut-off values of both receptors.

Adult↗