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Biomedical subjects

K Shibata

Publications and source records attributed to K Shibata.

At least 343 records · Page 19Linked to original sources
PubMed1995

Solution structure of endothelin B receptor selective antagonist RES-701-1 determined by 1H NMR spectroscopy.

The three-dimensional structure of the endothelin B receptor (ETB) selective antagonist RES-701-1 has been determined by 1H NMR in deuterated dimethyl sulphoxide. RES-701-1 consists of 16 amino acid residues with a novel internal linkage between the beta-carboxyl group of Asp9 and the alpha-amino group of Gly1. The structural calculations were carried out with the combined use of distance geometry and simulated annealing. The result indicates that RES-701-1 adopts an extraordinary folding; the 'tail' (Trp10-Trp16) passes through the 'ring' region (Gly1-Asp9). Several critical NOEs directly support this extraordinary folding. The folding of RES-701-1 turned out to be the same as that Frèchet et al. calculated for RP 71955 which possesses the same internal linkage as RES-701-1. The obtained structure suggested that the region consisting of Thr6, Ala7, Tyr14 and Tyr15 and/or, the region consisting of Asn2, Tyr14 and Tyr15 are involved in a binding with ETB.

Amino Acid Sequence↗
PubMed1995

Picture imperfect: hidden problems among Asian Pacific islander elderly.

Asian Pacific Islander (API) elderly represent the fastest growing group of ethnic elderly in the United States, yet their social and health needs remain little understood in the field of ethnogerontology. Existing literature generally portrays API elderly as in equal or better health compared to whites. However, aggregate API data cloud the bimodal distribution in socioeconomic and health status. We review existing literature on API elderly, and examine selected national data to illustrate the effects of a bimodal distribution on our understanding of API elderly socioeconomic and health status. Implications for research and policy are discussed.

Activities of Daily Living↗
PubMed1995

Induction of heat shock protein 70 and nucleolin and their intracellular distribution during early stage of liver regeneration.

Our previous work demonstrated a simultaneous induction of Hsp70 and nucleolin mRNA during the prereplicative stage of hepatocytes after partial hepatectomy [Ohmori, H. et al. (1990) Exp. Cell Res. 189, 227-232]. In the present study, changes of intracellular localization of these proteins were examined. Nucleolin, which mainly localized in the nucleus, increased with time and accumulated in the nucleolus around 12-18 h after partial hepatectomy. Hsp70 protein also increased slightly around 6-12 h after the operation. In accordance with this increase, immunohistochemical staining revealed that almost all nuclei of hepatocytes became Hsp70-positive, although Hsp70 was seen to be dispersed throughout the nucleoplasm and nucleolus at all times examined. Next, we isolated a cDNA clone of ribosomal protein (S-17) and examined its behavior. Induction of S-17 mRNA was observed to be essentially similar to that of nucleolin mRNA in regenerating rat liver, although inductions of histone H2A and H4 occurred at a later time, that is, in parallel with DNA synthesis. Furthermore, we observed a simultaneous induction of Hsp70 and nucleolin mRNA by serum-stimulation after serum-depletion in HeLa and IAR-20 (rat) culture cells. These results suggest that the induction of Hsp70, in addition to nucleolin, was not fortuitous but may be involved in the early events of liver regeneration.

Animals↗
PubMed1995

MAT-1, a monoclonal antibody that specifically recognizes human tyrosinase.

There is no available monoclonal antibody which reacts specifically recognizes human tyrosinase. Employing a synthetic peptide, MEKEDYHSLYQSHL, corresponding to the carboxyl terminus of human tyrosinase as an immunogen, we produced a mouse monoclonal antibody MAT-1 of the IgG1 isotype. The epitope for MAT-1 was determined to be EDYH, the sequence of which is not present in human tyrosinase-related protein-1 (TRP-1) or tyrosinase-related protein-2 (TRP-2). By transient expression assays and immunofluorescence technique, we show that MAT-1 reacts specifically with cells expressing human tyrosinase cDNA but not with cells expressing TRP-1 or TRP-2 cDNA. The results of immunohistochemical staining also confirmed that MAT-1 reacts specifically with epidermal melanocytes in human skin sections. MAT-1 should be invaluable for studying the interaction between tyrosinase and TRPs and for detecting the changes in the levels of tyrosinase expression. In addition, MAT-1 should be useful as a sensitive immunohistochemical tool for investigation of various pigmentary disorders and possibly for the diagnosis of melanoma.

Amino Acid Sequence↗
PubMed1995

Establishment and characterization of non-small cell lung cancer cell lines resistant to mitomycin C under aerobic conditions.

To elucidate the mechanisms of acquired resistance to mitomycin C (MMC) in non-small cell lung cancer (NSCLC), we established two MMC-resistant NSCLC sublines by continuous exposure to MMC, using PC-9 as a parent cell line. The sublines, PC-9/MC2 and PC-9/MC4, were 6.4- and 10-fold more resistant to MMC than their parent cell line, respectively, at the IC50 value as determined by MTT assay. They exhibited cross-resistance to EO9, but were not resistant to cisplatin, vindesine, etoposide, carboquone, or KW-2149, a novel MMC derivative. They were collaterally sensitive to adriamycin and menadione. Accumulation of the drug was decreased in the resistant sublines to about 60% of that in the parent cells. Cytosolic DT-diaphorase (DTD) activities were decreased to 13.5 +/- 3.2 in PC9/MC2 and 1.3 +/- 0.6 in PC-9/MC4 from 261.5 +/- 92.7 nmol/min/mg protein in the parent PC-9. NADH:cytochrome b5 reductase activities in both of the resistant cell lines were significantly decreased as compared to that in the parent cell line. Addition of dicumarol resulted in a two-fold increase in IC50 value in PC-9, whereas the IC50 value showed no change in PC-9/MC4. Moreover, dicumarol did not affect the sensitivities to KW-2149 but decreased the sensitivities to EO9 in both the parent and the resistant cell lines. Formation of an alkylating metabolite was significantly decreased in the resistant cells, in parallel to the degree of resistance. We concluded that deficient drug activation due to decreased DTD activity was important as a mechanism of resistance to MMC in PC-9, a relatively DTD-rich NSCLC cell line.

Aerobiosis↗
PubMed1995

Epidural anesthesia modifies cardiovascular responses to severe hypoxia in dogs.

Hypoxia is a critical and sometimes fatal complication of anesthesia. Since there is little information on the cardiovascular response to hypoxia during epidural anesthesia, we assessed the effects of epidural anesthesia on the cardiovascular response to hypoxia and on survival in dogs. We randomly assigned 36 mongrel dogs to one of three groups according to the anesthetic technique used: the thoracic group (n = 12) received thoracic epidural anesthesia plus general anesthesia, the thoracolumbar group (n = 12) received thoracolumbar epidural anesthesia plus general anesthesia, and the control group (n = 12) received general anesthesia alone. We monitored hemodynamics and plasma catecholamine concentrations and assessed survival in these groups during normocapnic hypoxia (FiO2, 0.09 for 120 min). During hypoxic challenge, PaCO2 and PaO2 values were similar in all groups. In both groups that received epidural anesthesia, heart rate, systolic and diastolic arterial pressures, and plasma epinephrine and norepinephrine concentrations were lower and arterial pH was greater than in the control group. There was no significant difference in survival among groups. Epidural anesthesia modified both the physiologic cardiovascular and catecholamine responses to hypoxia. Epidural anesthesia of the thoracic region did not appear to accelerate cardiac arrest, but it attenuated the development of metabolic acidosis during hypoxia.

Anesthesia, Epidural↗
PubMed1995

Bacterial activity of a new antiulcer agent, ecabet sodium, against Helicobacter pylori under acidic conditions.

Helicobacter pylori NCTC 11637, which is nonviable at pH 3.0, became viable after addition of 10 mM urea owing to ammonia production by urease. In a buffer supplemented with urea, ecabet sodium decreased both the production of ammonia and the number of viable cells of H. pylori NCTC 11637 and changed the bacteria from the bacilliform to the horseshoe or doughnut shape in a concentration-dependent manner. In particular, ecabet sodium (2 and 4 mg/ml) decreased the number of viable cells below the control level. Benzohydroxamic acid, a urease inhibitor, also caused a decrease in ammonia production accompanied by a decrease in the number of viable cells and changed the morphological form at pH 3.0, but the number of viable cells was not lowered below the control level. In buffers at various pHs without urea, ecabet sodium showed a concentration-dependent bactericidal effect on H. pylori at pHs 4.0 and 5.0 but not at pHs 6.0 and 7.0 while benzohydroxamic acid caused only a slight decrease in the number of viable cells at pH 4.0. These results suggest that ecabet sodium has strong bactericidal activity in addition to its urease-inhibiting activity under acidic conditions.

Abietanes↗
PubMed1995

AIDS-associated mycoplasmas possess phospholipases C in the membrane.

Phosphatidylinositol- and phosphatidylcholine-hydrolyzing activities existed in the cell lysates of AIDS-associated Mycoplasma species, including Mycoplasma fermentans IID 812, M. fermentans incognitus, and M. penetrans GTU-54-6A1. These activities were found to be attributable to phospholipases C, because the water-soluble product from phosphatidylcholine digested by the cell lysate of M. fermentans IID 812 was phosphorylcholine. M. fermentans IID 812 was examined for localization of these enzymes, and it was found that they were associated with the membrane.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Negative chronotropic effect of endothelin 1 mediated through ETA receptors in guinea pig atria.

Endothelins exert potent excitatory cardiac effects by acting on specific receptors on myocytes. In this study, we have examined the signal transduction mechanism for the chronotropic effect of endothelins in guinea pig atria. A competition binding of [125I]endothelin 1 ([125I]ET-1) using the recently developed ETA receptor-selective antagonist BQ123 showed the presence of almost equal populations of ETA (44%) and ETB (56%) receptors in the guinea pig right atria. In a concentration-response study, endothelin 3 (ET-3), an agonist with higher affinity to ETB receptors than to ETA receptors, and sarafotoxin S6c (STXS6c), an ETB receptor-selective agonist, increased the rate of spontaneous beating at all concentrations tested (10 pmol/L to 100 nmol/L). In contrast, ET-1, a nonselective agonist, increased the heart rate at lower concentrations (10 pmol/L to 10 nmol/L) but decreased it at higher concentrations (30 to 100 nmol/L). When ET-1 (100 nmol/L) was applied in a single amount, heart rate was strongly increased; however, this increase was followed by a rapid decline in the response. ET-1 (100 nmol/L) but not ET-3 or STXS6c significantly reduced the heart rate when it was raised by isoproterenol (ISO, 300 nmol/L) either in the absence or presence of a phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX). Correspondingly, ET-1 significantly reduced the ISO-induced elevation of cAMP accumulation (19.1 +/- 1.7 pmol/mg protein [n = 8] and 12.6 +/- 1.2 pmol/mg protein [n = 7] in the absence and presence of ET-1, respectively; P < .01), which was also observed even in the presence of IBMX.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Effects of vitamin B6 deficiency on the conversion ratio of tryptophan to niacin.

To investigate how vitamin B6 (B6) deficiency affects the whole metabolism of tryptophan-niacin, rats were fed for 19 days with each of the following four kinds of diets; a complete 20% casein diet (control diet), the control diet without B6, the control diet without nicotinic acid, and the control diet without nicotinic acid and B6, and the urinary excretion of such tryptophan metabolites as kynurenic acid, xanthurenic acid, nicotinamide, N1-methylnicotinamide, N1-methyl-2-pyridone-5-carboxamide, and N1-methyl-4-pyridone-3-carboxamide each and the enzyme activities involved in tryptophan-niacin pathway were measured. The urinary excretion of kynurenic acid decreased while that of xanthurenic acid increased drastically in the two B6-deficient groups, when compared with the B6-containing groups. These results indicate that the rats fed with the B6-free diets were in the vitamin-deficient state. The conversion ratio was calculated from the ratio of the urinary excretion of sum of nicotinamide, N1-methylnicotinamide, N1-methyl-2-pyridone-5-carboxamide, and N1-methyl-4-pyridone-3-carboxamide, to the Trp intake. The ratio was statistically lower in the B6-free diet than in the B6-containing diet under the niacin-free conditions.

Animals↗
PubMed1995

Effects of adrenalin on the conversion ratio of tryptophan to niacin in rats.

The administration of glycemia-affecting chemicals such as alloxan, streptozotocin, and 6-aminonicotinamide decreases the conversion ratio of tryptophan to niacin. Adrenalin is also known to increase the glucose level. For this reason, the effects of adrenalin on the conversion ratio were investigated. We found that the conversion ratio of tryptophan to niacin was reduced to half by the intraperitoneal injection of adrenalin at 75 micrograms/day/rat (body weight, about 250 g) every day for 7 days. Niacin decreases adrenalin-stimulated glycogenolysis via stimulating phosphodiesterase activity or depressing adenyl cyclase activity. Accordingly, in urgent need of energy, animals would have to decrease the concentration of niacin within the body.

Animals↗
PubMed1995

Conversion ratio of tryptophan to niacin in rats fed with a nicotinic acid-free, tryptophan-limiting diet.

The effects of amino acid composition on the conversion ratio of Trp to niacin in rats were investigated. The ratio in the group fed with a nicotinic acid-free, 9% casein-sucrose diet (basal diet) was 3.5%. This ratio was statistically decreased to 0.2% by the addition of 2% glycine, 0.078% L-threonine, and 0.2% L-cystine, and restored to 3.2% by the further addition of 0.1% tryptophan. From these results and our previous findings, it was considered that Trp imbalance might be a manifestation of niacin deficiency.

Animals↗
PubMed1995

Assessment of genetic variations within populations of Sika deer in Japan by analysis of randomly amplified polymorphic DNA (RAPD).

Random amplified polymorphic DNA (RAPD) was exploited as a genetic marker to assess the level of genetic variation in populations of Sika deer, Cervus nippon, in Japan. DNA samples were collected from three local populations in Japan, namely, Kinkazan, Goyozan and Ashoro populations. Four arbitrary primers, when used individually, amplified an average of five RAPD fragments in the polymerase chain reaction (PCR). The number of polymorphic bands was scored to calculate band-sharing coefficients within populations. Average band-sharing coefficients revealed a higher degree of homogeneity in the Kinkazan population. Samples collected from larger populations, namely, Ashoro and Goyozan, revealed greater polymorphism than samples from the Kinkazan deer. Our data suggest that RAPD is useful as a marker for detecting genetic variations in populations of Sika deer with reduced levels of genetic diversity.

Animals↗
PubMed1995

Metabolism of essential amino acids in growing rats at graded levels of soybean protein isolate.

The metabolic fates of the carbon skeletons of essential amino acids were investigated in growing rats fed on diets containing graded percentages of protein calories (5, 10, 15, 20, 30, and 40 PC%) using soybean protein isolate at 4,100 kcal of metabolizable energy per kg of diet. The incorporation of 14C into the body protein 12 h after the intraperitoneal injection of labeled essential amino acids was more than 60% of the dose in the 5 to 10 PC% groups, but it began to decline gradually in the higher PC% groups. The expired 14CO2 production from labeled threonine, tryptophan, leucine, isoleucine, valine, phenylalanine, and lysine increased linearly with increasing levels of dietary soybean protein, but the rate of increase in the 14CO2 production was lower in the higher PC% groups. In comparison, the 14CO2 production from methionine, histidine, and arginine decreased in the 5 to 15 PC% groups, and it increased linearly in the higher PC% groups. The extent of 14CO2 production varied among the essential amino acids in each dietary group. These results indicate that the carbon skeletons of essential amino acids are mainly utilized for body protein synthesis, but significant amounts of their carbons are oxidized to expired carbon dioxide for energy production, and that the metabolic responses of these amino acids to dietary protein level change at around 20 PC%, where the growth rate reached its approximate maximum. The utilization of individual essential amino acids in rats fed on the soybean protein diets changed markedly as compared to those on purified whole egg protein diets, the results of which have been reported elsewhere.

Amino Acids, Essential↗
PubMed1995

AKD-2A, B, C and D, new antibiotics from Streptomyces sp. OCU-42815. Taxonomy, fermentation, isolation, structure elucidation and biological activity.

An antibiotic complex, AKD-2, was isolated from the mycelial cake of Streptomyces sp. OCU-42815. The lipophilic substances in this complex were further purified by a recycling HPLC procedure and were designated AKD-2A, C and D. AKD-2B was obtained as a mixture of AKD-2B1 and AKD-2B2. These substances were identified as monoglycerides having branched chain fatty acids and exhibited both antibacterial and antifungal activities.

Antifungal Agents↗