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Biomedical subjects

H Hayashi

Publications and source records attributed to H Hayashi.

At least 811 records · Page 45Linked to original sources
PubMed1994

The role of Na+/H+ exchange and the Na+/K+ pump in the regulation of [Na+]i during metabolic inhibition in guinea pig myocytes.

To investigate the mechanisms of Na+ loading during metabolic inhibition (MI), [Na+]i and pHi were measured in quiescent guinea pig myocytes using fluorescent probes, sodium-binding benzofuran isophthalate and 2,7,bis(carboxyethyl)-5,6-carboxyfluorescein. When myocytes were exposed to MI (3.3 mM amobarbital and 5 microM carbonyl cyanide m-chlorophenylhydrazone, without glucose) for 20 min, [Na+]i increased from 8.3 +/- 0.7 mM to 17.7 +/- 1.3 mM (p < 0.01) and pHi decreased from 7.22 +/- 0.03 to 7.00 +/- 0.04 (p < 0.05). The inhibition of Na(+)-H+ exchange by hexamethylene amiloride (HMA) significantly attenuated the increase in [Na+]i during MI (9.3 +/- 0.9 mM; p < 0.01 vs MI without HMA). When a K(+)-free solution was perfused to inhibit the Na+/K+ pump in the presence of HMA, there was an immediate increase in [Na+]i during MI. Perfusion of a K(+)-free solution after 10 min of MI caused no change in the rate of the increase in [Na+]i. We concluded that 1) Na+/H+ exchange was an important mechanism for Na+ elevation during MI, and 2) the Na+/K+ pump was functional during the early phase of MI, but was inhibited 10 min after MI in this model.

Amiloride↗
PubMed1994

Peroxisomal cholesterol synthesis in vivo: accumulation of 4-methyl intermediate sterols after aminotriazole inhibition of cholesterol synthesis.

To clarify the importance and pathway of peroxisomal cholesterol synthesis in vivo, we have examined whether or not 4,4-dimethyl-5 alpha-cholest-8-en-3 beta-ol and 4 alpha-methyl-5 alpha-cholest-7-en-3 beta-ol are accumulated in hepatic peroxisomes of aminotriazole-treated rats (we have shown that these intermediate steroids accumulate in rat liver when cholesterol synthesis is inhibited by aminotriazole: Hashimoto, F. and Hayashi, H. (1991) Biochim. Biophys. Acta 1086, 115). Differential centrifugation and Nycodenz gradient centrifugation showed that these intermediate steroids were localized in peroxisomes and microsomes. Cholestyramine (3-hydroxy-3-methylglutaryl-CoA reductase activator) pretreatment of aminotriazole-treated rats increased the contents of the intermediate steroids in both peroxisomes and microsomes. In peroxisomes, both 4 alpha-methyl-5 alpha-cholest-7-en-3 beta-ol and 4,4-dimethyl-5 alpha-cholest-8-en-3 beta-ol were increased to about 3 times the control (aminotriazole-treated rat), and they were predominantly (about 70%) recovered in the membrane fraction after treatment with 0.05% deoxycholate or 100 mM Na2CO3. Gemfibrozil (peroxisomal proliferator) pretreatment enhanced the contents of 4 alpha-methyl-5 alpha-cholest-7-en-3 beta-ol and 4,4-dimethyl-5 alpha-cholest-8-en-3 beta-ol of peroxisomes to 4.5 times and 37 times the control, respectively. The effects of aminotriazole, cholestyramine and gemfibrozil on the intermediate contents were different between peroxisomes and microsomes. We suggest that peroxisomes in addition to microsomes participate in cholesterol synthesis in vivo, and the biosynthetic pathway includes 4 alpha-methyl-5 alpha-cholest-7-en-3 beta-ol and 4,4-dimethyl-5 alpha-cholest-8-en-3 beta-ol.

Amitrole↗
PubMed1994

High-level expression of Mycoplasma arginine deiminase in Escherichia coli and its efficient renaturation as an anti-tumor enzyme.

The arginine deiminase (AD) gene was cloned from Mycoplasma arginini and expressed in the cytosol of Escherichia coli as inclusion bodies with an expression level of at least 20% of the total bacterial proteins. The inclusion bodies were solubilized with 6 M guanidine hydrochloride (Gdn-HCl) under reducing conditions, in order to avoid incorrect disulfide-bond formation of the recombinant (r-) AD molecules, and renaturation was performed under various refolding conditions. The optimum renaturation conditions were found to be incubation for 90 h at pH 7.5 and 15 degrees C. The resulting completely refolded r-AD was purified to homogeneity by anion-exchange and arginine-affinity chromatography and its activity yield was 72.5%. The specific activity of the purified r-AD was comparable to and its amino acid composition was identical to those of Mycoplasma AD, and NH2-terminal sequence analysis revealed that its methionine residue corresponding to the translation initiation codon had been removed completely. Anti-tumor activity analyses showed that r-AD inhibited the growth of two mouse cell lines, hepatoma MH134 and fibrosarcoma Meth A, strongly in vitro at concentrations in excess of 10 ng ml-1. Moreover, when MH134-implanted mice were given single intravenous injections of r-AD at doses of 50 mg kg-1 and higher, their survival times were prolonged significantly. These results, taken together, indicate that the enzymatic properties and biological actions of r-AD were highly consistent with those of Mycoplasma AD.

Amino Acid Sequence↗
PubMed1994

Enzymic O-sulfation of tyrosine residues in hirudins by sulfotransferase from Eubacterium A-44.

The enzymic O-sulfation of Tyr residues in a recombinant hirudin variant-1 (rHV-1) and its analog in which Glu61 and Glu62 were replaced by Tyr, [E61Y, E62Y]rHV-1, was carried out by use of sulfotransferase isolated from an anaerobic bacterium from the human intestine, Eubacterium A-44. Although rHV-1 was not sulfated by this enzyme, the sulfation of [E61Y, E62Y]rHV-1 was observed, and three kinds of sulfated analog, whose C-terminal six amino acid residues were -PYY(SO3H)YLQ, -PYYY(SO3H)LQ, and -PYY(SO3H)Y(SO3H)LQ, were obtained. Among the sulfated hirudin analogs tested here, the Tyr62 and Tyr63 bisulfated [E61Y, E62Y]rHV-1 showed the strongest thrombin inhibition with the inhibition constant (Ki) of 0.0430 pM, followed by the Tyr63 monosulfated analog (Ki = 0.0593 pM) and the Tyr62 monosulfated one (Ki = 0.158 pM). The Tyr63 monosulfated analog and Tyr62 and Tyr63 bisulfated one were more potent inhibitors of thrombin than unsulfated rHV-1. The increase in affinity caused by sulfation was predominantly due to an increase in the association-rate constant.

Amino Acid Sequence↗
PubMed1994

Oxygen free radicals and calcium homeostasis in the heart.

Many experiments have been done to clarify the effects of oxygen free radicals on Ca2+ homeostasis in the hearts. A burst of oxygen free radicals occurs immediately after reperfusion, but we have to be reminded that the exact levels of oxygen free radicals in the hearts are yet unknown in both physiological and pathophysiological conditions. Therefore, we should give careful consideration to this point when we perform the experiments and analayze the results. It is, however, evident that Ca2+ overload occurs when the hearts are exposed to an excess amount of oxygen free radicals. Though ATP-independent Ca2+ binding is increased, Ca2+ influx through Ca2+ channel does not increase in the presence of oxygen free radicals. Another possible pathway through which Ca2+ can enter the myocytes is Na(+)-Ca2+ exchanger. Although, the activities of Na(+)-K+ ATPase and Na(+)-Ca2+ exchanger. Although, the activities of Na(+)-H+ exchange are inhibited by oxygen free radicals, it is not known whether intracellular Na+ level increases under oxidative stress or not. The question has to be solved for the understanding of the importance of Na(+)-Ca2+ exchange in Ca2+ influx process from extracellular space. Another question is 'which way does Na(+)-Ca2+ exchange work under oxidative stress? Net influx or efflux of Ca2+?' Membrane permeability for Ca2+ may be maintained in a relatively early phase of free radical injury. Since sarcolemmal Ca(2+)-pump ATPase activity is depressed by oxygen free radicals, Ca2+ extrusion from cytosol to extracellular space is considered to be reduced. It has also been shown that oxygen free radicals promote Ca2+ release from sarcoplasmic reticulum and inhibit Ca2+ sequestration to sarcoplasmic reticulum. Thus, these changes in Ca2+ handling systems could cause the Ca2+ overload due to oxygen free radicals.

Adenosine Triphosphate↗
PubMed1994

Metaphase and anaphase in the artificially induced monopolar spindle.

By using monopolar spindles artificially induced in sea urchin embryos, we examined whether or not the presence of two opposing poles was an indispensable condition for keeping chromosomes at a fixed distance from the pole at metaphase and for the anaphase chromosome movement. Chromosomes were stained with Hoechst dye 33342 and their behavior was followed in the monopolar and the control bipolar spindles. In the monopolar spindle, chromosomes were first arranged on a curved metaphase plate and then spread on a part of the imaginary surface of a sphere whose center was the monopole. The estimated chromosome-to-pole distance was similar to that of bipolar spindles at metaphase and remained fixed until chromosomes started to move toward the pole. The average duration of metaphase in the monopolar spindle was 6 times longer than that in the bipolar spindle. The poleward movement of chromosomes in the monopolar spindle was similar to the anaphase A (chromosome-to-pole movement) in the bipolar spindle with respect to the velocity, duration, distance, and synchronization of migration. These results show that even half of the normal spindle has capacities for the arrangement of chromosomes at metaphase and for the anaphase A chromosome movement. Based on these results, we were able to exclude some existing theories of metaphase, such as the one based on the balance of forces between the two poles.

Anaphase↗
PubMed1994

pS2 gene especially expressed in the late G1/S phase of mouse astrocytes.

By the reverse transcription-polymerase chain reaction we investigated the localization of pS2 mRNA, which encodes a secreted polypeptide of 60 amino acids with unknown function, in the adult mouse. This method revealed that the expression of pS2 mRNA was not restricted to the stomach as previously reported but was also found in various other tissues such as brain, heart, spleen, and muscle. The pS2 mRNA was additionally detected in astrocytes cultured from the whole brain of the newborn mouse. The pS2 expression in these astrocytes increased with cell growth and sharply declined after the cells reached the stationary phase. In the cells synchronized by the serum deprivation-refeeding technique, the expression of pS2 mRNA was only found at late G1 and S phase. These results suggest that the transcripts of pS2 gene are widely distributed throughout the entire body of the mouse and that they play some important cell cycle-related role in these tissues.

Animals↗
PubMed1994

[Usefulness of dynamic subtraction CT for intracranial high density lesions].

Dynamic subtraction CT (DSCT) using a high speed Rotate/Rotate CT Scanner (Toshiba Xforce) was performed on 10 patients with intracranial high density lesions such as brain tumors and vascular malformations. In comparison with conventional contrast enhanced CT, the technique of dynamic subtraction CT enabled us to evaluate more clearly the contrast enhancement of high density lesions and to separate more easily the lesions from hematoma and calcification, which are shown as avascular areas. The results suggest that DSCT is a valuable method for evaluating the contrast enhancement of intracranial high density lesions.

Adult↗
PubMed1994

Expression of the gene encoding the tyrosine kinase-deficient human insulin receptor in transgenic mice.

Defects in the insulin receptor (IR) in diabetic patients have been given much attention. To address the role of such defects, we generated a transgenic (TG) mouse carrying the cDNA encoding a tyrosine-kinase (TK)-deficient human IR (hIR), under the control of the native promoter. The TG mouse expressed the transgene (TG) mRNA in the liver, as identified in Northern blots. Analyses of various tissues by reverse transcription-polymerase chain reaction revealed that expressions of the TG mRNA in brain, heart, kidney, lung, stomach, skeletal muscle and adipose tissue were higher than those seen with the endogenous mouse IR (mIR), but expression in small intestine, colon, spleen, testis and ovary were approximately half those seen with the endogenous mIR. In the liver, the expression of the TG was about one tenth that of the endogenous mIR. In analyses of insulin binding and IR autophosphorylation, using a human-specific anti-IR antibody, the TK-deficient hIR was synthesized in the tissues of the TG mice. Despite the expression of TK-deficient hIRs in various tissues, including the major insulin-target tissues, muscle and adipose tissues, of the TG mice, no glucose intolerance was observed as assessed by the intraperitoneal glucose tolerance test, before and after sucrose feeding for 55 weeks. Our results suggest that a higher expression of the mutated IR, especially in the liver which is another major insulin-target tissue, or additional pathogenic factors, environmental or genetic, might be required for glucose intolerance.

Animals↗
PubMed1994

Modulation of coagulation and fibrinolysis in hepatic resection: a randomized prospective control study using antithrombin III concentrates.

A randomized prospective control trial for determining the efficacy of antithrombin III concentrates in hepatic resection was performed using 24 patients with hepatocellular carcinoma. Thirteen patients were given antithrombin III concentrates (1,500 IU) immediately before operation, during hepatectomy and immediately after operation. Coagulant and fibrinolytic profiles were determined by molecular markers such as thrombin-antithrombin III complex and plasmin-alpha 2plasmin inhibitor complex. During hepatic resection, both hypercoagulability and mainly primary hyperfibrinolysis occurred. Regarding the effectiveness of antithrombin III concentrates, in the antithrombin III treatment group, only a significant lower incidence of positive soluble fibrin monomer complex at postoperative days 1 and 5 was found among all the parameters studied. Therefore, no definite evidence of clinical usefulness of the perioperative administration of antithrombin III concentrates in hepatic resection was proved.

Aged↗
PubMed1994

Eclosion hormone-mediated signal transduction in the silkworm abdominal ganglia: involvement of a cascade from inositol(1,4,5)trisphosphate to cyclic GMP.

The neuropeptide eclosion hormone triggers ecdysis behavior in lepidopteran insects. We have previously shown that the eclosion hormone stimulates the formation of two intracellular second messengers, cGMP and inositol(1,4,5)trisphosphate in the abdominal ganglia of Bombyx mori. In order to elucidate the intracellular signaling pathway involving these second messengers, we studied the eclosion hormone-mediated signal transduction using saponin-treated abdominal ganglia. We obtained the following results; i) eclosion hormone activated nitric oxide synthase, ii) the eclosion hormone-induced cGMP increase was inhibited by various enzyme inhibitors such as NG-nitro-arginine; a nitric oxide synthase inhibitor, EGTA; a calcium chelating reagent, W-5; a calmodulin inhibitor and compound 48/80; a phospholipase C inhibitor and iii) the inositol(1,4,5)-trisphosphate stimulated the formation of cGMP, in the Bombyx abdominal ganglia. Based on these findings we tentatively propose a hypothetical pathway: The signal initially triggered by eclosion hormone and eclosion hormone receptor complex induces activation of phospholipase C which produces inositol(1,4,5)trisphosphate. Inositol(1,4,5)trisphosphate increases intracellular Ca2+, followed by subsequent activation of nitric oxide synthase through the formation of Ca(2+)-calmodulin complex. The reaction product, nitric oxide acts on soluble guanylate cyclase to stimulate cGMP formation which induces the ecdysis behavior in Bombyx pharate adults.

Amino Acid Oxidoreductases↗
PubMed1994

Multiple hepatic hemangiomas with significant arterioportal venous shunting.

A patient with multiple hepatic hemangiomas and significant arterioportal shunting who was successfully treated by a left-hepatic lobectomy is presented herein. In hemangiomas with significant arterioportal venous shunting, it is essential to differentiate between hepatocellular carcinoma and hypervascular metastatic tumors because few typical findings of hemangioma can be recognized. Moreover, an increased hepatic arterial flow can increase the risk of spontaneous rupture as well as portal hypertension due to the increased inflow to the portal vein. Therefore, a definitive diagnosis should be made by liver biopsy when imaging alone is not sufficient to rule out malignancy. Furthermore, hepatic resection for hemangiomas with significant arterioportal venous shunting may be indicated due to the higher risk of rupture and the possibility of progressive portal hypertension.

Angiography↗
PubMed1994

Resistance to the anti-proliferative effect of IL-1 on human melanoma cell line is associated with endogenous production of IL-1 and IL-6.

A human melanoma cell line (A375-6) became resistant to the anti-proliferative effect of human IL-1 after a long period of culture. Two stable resistant sub-clones were obtained, and the mechanism of the IL-1 resistance was investigated. Resistant cells, but not sensitive cells, appeared to produce constitutively IL-1 activity. The activity was neutralized by anti-IL-1 alpha antibody but not by anti-IL-1 beta antibody. Resistant cells expressed IL-1 alpha but not IL-1 beta mRNA. Therefore, the resistant cells appeared to produce IL-1 alpha mRNA for IL-1 receptor antagonist (IL-1Ra) was not detected in resistant cells, indicating that the resistance is not attributable to IL-1Ra. These resistant cells were also resistant to the anti-proliferative effect of human IL-6, but not to that of human TNF. Resistant cells appeared to produce constitutively IL-6 more than sensitive cells, and IL-6 production both in sensitive and in resistant cells was augmented by exogenous IL-1. Furthermore, constitutive production of IL-6 in resistant cells was inhibited by IL-1Ra. Type I IL-1 receptor (IL-1R) mRNA was expressed equally in resistant and sensitive cells. These data indicate that the resistance is not the result of loss of functional IL-1R and that IL-1 induces IL-6 in an autocrine manner. It is, therefore, conceivable that endogenous IL-1 and IL-6 contribute to IL-1 resistance.

Cell Division↗
PubMed1994

Detection of minus-strand hepatitis C virus RNA in tumor tissues of hepatocellular carcinoma.

BACKGROUND: Recently, the detection of hepatitis C virus (HCV) antibody has been widely performed for clinical serum testing of HCV infection and can be identified in most hepatocellular carcinoma (HCC) cases in Japan. In the current study, the authors detected not only plus-strand but also minus-strand HCV RNA as a template for RNA replication in hepatocytes in the resected tumors of HCC, and they investigated those significant for HCC. METHODS: The plus-strand and minus-strand HCV RNA were detected using reverse transcription-polymerase chain reaction after the extraction of RNA from the tumor and nontumor tissues of hepatectomized liver, respectively. RESULTS: The detection of HCV RNA in liver tissues from hepatectomized specimens of 20 cases was as follows: in nontumor regions, both of the plus- and minus-strand HCV RNA were detected in 14 cases. Among those cases, plus- and minus-strand HCV RNA were detected in 11 cases, and in another 2 cases, only plus-strand HCV RNA was found in the tumor regions. CONCLUSIONS: These results suggest that HCV RNA is able to replicate in tumor tissues of HCC and may be involved in the development of HCC and also that HCV in remnant hepatocytes may cause the recurrence of HCC as secondary carcinogenesis after hepatectomy.

Adult↗
PubMed1994

Functioning of the intrathoracic stomach after esophagectomy.

OBJECTIVE: To investigate acid secretion and motility of the intrathoracic stomach with truncal vagotomy after esophagectomy. DESIGN: Case-control study of patients undergoing esophagectomy, with average follow-up of 3.2 months, compared with health controls. SETTING: Yamaguchi University School of Medicine, Kogushi, Japan. PATIENTS: A random sample of 21 patients selected from 79 patients with esophageal cancer during the period from May 1988 to August 1993 received the intrathoracic stomach after subtotal esophagectomy. A control sample consisted of 14 men. INTERVENTIONS AND MAIN OUTCOME MEASURES: For acid secretion, a pH probe was placed in the intrathoracic stomach to measure the average pH value (average of total monitoring values) and pH holding time (ratio of the period during which the pH value was 3 or higher based on the entire continuous monitoring periods). For motility, digestive tract scintigraphy was performed to obtain the time activity curve from the analog image observed when patients ate meals labeled with indium 111. In addition, hemorrhagic ulcers in the intrathoracic stomachs of three patients were reported. RESULTS: A pH value below 3 was recognized after surgery, and there was no significant difference between pH values in patients and normal volunteers (average pH value, 3.9 +/- 1.5 vs 3.3 +/- 1.9; pH holding time, 52.2 +/- 20.2% vs 57.1 +/- 24.4%, respectively). The time activity curve of the intrathoracic stomach observed by scintigraphy underwent no change after surgery. Among three patients with hemorrhagic ulcers, two exhibited improvements after receiving a histamine blocker, while in the other, it was not effective. CONCLUSION: Acid secretion ability and motility of the intrathoracic stomach with truncal vagotomy may be unchanged after esophagectomy.

Case-Control Studies↗
PubMed1994

The utility of Nitroderm TTS in angina pectoris: long-term treatment after switching from long-acting oral isosorbide dinitrate.

Long-acting oral isosorbide dinitrate (ISDN) was replaced by Nitroderm TTS, and the utility of this drug in long-term treatment was assessed in 69 patients with angina pectoris. The frequency of attacks (p < 0.001) and the consumption of sublingual nitrate tablets (p < 0.01) were found to be significantly lower at 2 weeks to 6 months than in the observation period in patients who experienced attacks or received sublingual tablets during the observation period. On the other hand, no significant time-lapse changes from the observation period were noted in patients who experienced no attacks or received no sublingual tablets during the observation period. The symptoms of adverse effects were mild. The improvement rates (improved) of subjective symptoms and electrocardiogram (ECG) in Group A were about 50% after 6 months. On the other hand, the improvement rates (not aggravated) of subjective symptoms and ECG in Group B were more than 90%. Nitroderm TTS is considered a useful plaster preparation which can be used for sufficiently extended periods of time because its efficacy was as high as, or higher than, that of oral ISDN when this drug was administered over a long period of time after a switch from long-acting oral ISDN in angina pectoris patients.

Administration, Cutaneous↗
PubMed1994

Anticancer chemosensitivity profile of freshly separated human pancreatic cancer cells assessed by DNA synthesis inhibition assay.

The chemosensitivity of 49 freshly separated human pancreatic cancers to seven kinds of anticancer agents were assessed by a DNA synthesis (3H-thymidine incorporation) inhibition assay. DNA synthesis is higher in involved lymph nodes (n = 7), malignant effusion (n = 15), liver metastasis (n = 7), primary cancer (n = 15), and skin metastasis (n = 5). Chemosensitivity assay demonstrates that etoposide, 4-epirubicin, carboquone, and 5-fluorouracil are more effective than cisplatin, mitomycin-C, and Adriamycin. In general, metastatic lesions of pancreatic cancer tend to show higher chemosensitivity than primary lesions. Pathological analysis demonstrates that small primary pancreatic cancers tend to be more responsive than large primary cancers, and primary pancreatic cancers with no regional lymph node involvement also tend to be more responsive than those with nodal involvement. No significant differences are seen in terms of tumor spread, vascular involvement, sex of patient, and histological type. When chemosensitivity assay is not available, the results of the present study may be beneficial to choose the regimens.

Adult↗