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Biomedical subjects

H Hayashi

Publications and source records attributed to H Hayashi.

At least 721 records · Page 40Linked to original sources
PubMed1995

Methylmercury induces Ca(2+)-dependent hyperpolarization of mouse thymocytes: a flow cytometric study using fluorescent dyes.

The effect of methylmercury on mouse thymocytes was examined using fluorescent dyes for membrane potential and intracellular Ca2+. Methylmercury at concentrations of 1 microM or higher (up to 30 microM) produced hyperpolarization in a dose-dependent fashion. Charybdotoxin and quinine, but not 4-aminopyridine and tetraethylammonium, greatly suppressed methylmercury-induced hyperpolarization. Removal of external Ca2+ reduced the degree of hyperpolarization. Pretreatment of thymocytes with A23187 under Ca(2+)-free conditions abolished the hyperpolarization induced by methylmercury. Under both normal and Ca(2+)-free conditions methylmercury increased the intracellular concentration of Ca2+. The results suggest that the increase in intracellular Ca2+ is mediated through a Ca2+ release from intracellular stores as well as through influx of external Ca2+. Therefore, it is likely that methylmercury increases the intracellular concentration of Ca2+, resulting in activation of Ca(2+)-dependent K+ conductance of mouse thymocytes.

Animals↗
PubMed1995

Rate of release and retentivity of prostaglandin E1 in lipid emulsion.

The rates of release of prostaglandin E1 (PGE1) from lipid particles into aqueous solution were obtained by the dialysis method, for parenteral lipid emulsion (Lipo-PGE1) diluted 10-times with buffered solutions of various pH. The findings, which were the rates of release of PGE1, were used to calculate the amount of PGE1 distributed in lipid particles when Lipo-PGE1, diluted 100-times with various pH levels of the buffered solution, was administered by intravenous drip infusion. More than 90% of PGE1 was retained in the lipid particles and intravenously infused when transfusion fluid pH was less than 5.5 and 2 ml of Lipo-PGE1 and 198 ml of transfusion fluid had been mixed and were administered over 2 h. Results from simulation showed that half of the PGE1 was retained in lipid particles and was infused, if Lipo-PGE1 was diluted 100-times with pH 8 transfusion fluid. Though PGE1 was sparingly soluble in an aqueous solution, these findings demonstrated that a significant amount of PGE1 was retained in lipid particles. Thus, this dosage form is expected to be highly effective for a drug delivery of PGE1 in clinical treatment.

Alprostadil↗
PubMed1995

Effect of gemfibrozil on lipid biosynthesis from acetyl-CoA derived from peroxisomal beta-oxidation.

The effect of gemfibrozil, a peroxisome proliferator, on lipid biosynthesis from acetyl-CoA derived from peroxisomal beta-oxidation was studied. The specific activity of the peroxisomal fatty acyl-CoA beta-oxidation system of rats fed a chow containing 0.2% gemfibrozil for 2 weeks was approximately five times higher than that of control rats. When [1-14C]lignoceric acid, a very-long-chain fatty acid which is degraded exclusively by the peroxisomal beta-oxidation system at first, was injected into rats treated with gemfibrozil, radioactivity and content of bile acid in the bile were enhanced to approximately 2.2 and 3.5 times the control, respectively. Gemfibrozil increased the radioactivity and content of chenodeoxycholic acid more than that of cholic acid. The incorporation of radioactivity into cholesterol in the bile was as much as 4.5 times greater than the control, and content was 2.6 times greater. In the liver, incorporation of [14C]lignoceric acid into the simple lipids phosphatidylethanolamine and phosphatidylcholine was unaffected by gemfibrozil. The radioactivity and content of cholesterol separated from the simple lipids were also virtually unaffected. However, the specific activities of 3-hydroxy-3-methylglutararyl-CoA reductase (rate-limiting enzyme of cholesterol synthesis) of peroxisomes and microsomes were remarkably stimulated by gemfibrozil treatment. These results suggest that biosyntheses of cholesterol and bile acid from acetyl-CoA derived from peroxisomal beta-oxidation are stimulated by gemfibrozil, due at least in part to activation of the peroxisomal beta-oxidation system and 3-hydroxy-3-methylglutaryl-CoA reductase of peroxisomes and/or microsomes. Most peroxisomal proliferators (e.g. clofibrate) have been known to inhibit 3-hydroxy-3-methylglutaryl-CoA reductase activity. Therefore, gemfibrozil is expected to be a very useful tool for elucidating the relationship between peroxisomes and the biosyntheses of cholesterol and bile acid.

Animals↗
PubMed1995

Sialyllactose-mediated cell interaction during granulosa cell differentiation. Identification of its binding proteins.

The present study was designed to prove the carbohydrate-binding proteins interacting with cell surface sialyllactosylceramide (GM3, NeuAc alpha 2-->3Gal beta 1-->4Glc beta 1-->1'Cer), which is highly expressed during differentiation of rat ovarian granulosa cells. As a specific ligand for the sialyllactose (SL)-binding proteins on granulosa cells, we used a radioiodinated multivalent SL-linked albumin (Alb-(SL)17). The specific association of the ligand to the putative proteins on the intact cells was competitively inhibited by GM3 more effectively than other gangliosides, sialyllactotetraosylceramide, sialylneolactotetraosylceramide, and several glycoproteins with N-linked oligosaccharides. However, the proteins had no specificity for the side chain (N-acetyl or N-glycolyl forms) of sialic acid in GM3. Scatchard analysis of Alb-(SL)17 binding showed high (Kd = 6.4 x 10(-10)M) and low (Kd = 3.1 x 10(-8)M) affinity population of binding sites. By direct binding of 125I-Alb-(SL)17 to SL-binding proteins on Western blots, the putative proteins with molecular masses of 35, 18, and 14 kDa were detected. The interaction of the multivalent derivative with these binding proteins was differently modulated by Ca2+ and Mn2+. The SL-binding proteins occurred in immature granulosa cells and progressively decreased during differentiation, whereas their endogenous ligand GM3 increased. These results indicate that relatively low molecular weight SL-binding proteins exist on the surface of immature granulosa cells and that they may serve as receptor sites for newly synthesized GM3 during differentiation.

Animals↗
PubMed1995

A human erythrocyte-derived growth-promoting factor with a wide target cell spectrum: identification as catalase.

We have reported previously that a factor with a molecular weight of 53,000 under SDS-polyacrylamide gel electrophoresis purified from human erythrocyte extracts promoted the growth of a wide variety of cell types from different species, including T cells, B cells, myeloid leukemia cells, melanoma cells, and mastocytoma cells, as well as normal and transformed fibroblast cells. In the present study, amino acid sequence analysis revealed that this factor has homology with human catalase. The purified factor exhibited catalase activity. Catalases derived from human erythrocytes, bovine liver, Aspergillus niger, and recombinant rat liver catalase are all able to promote the growth of cells. Antibody against human catalase absorbed both the growth-promoting activity and the enzyme activity of the purified factor. In addition, treatment of the factor with an irreversible enzyme inhibitor, aminotriazole, resulted in abrogation of both the growth-promoting activity and enzyme activity. These results indicate that the growth-promoting factor is catalase, and its activity is associated with the decomposition of hydrogen peroxide.

Amino Acid Sequence↗
PubMed1995

Sodefrin: a female-attracting peptide pheromone in newt cloacal glands.

A decapeptide called sodefrin was isolated from the abdominal gland of the cloaca of the male red-bellied newt, Cynops pyrrhogaster. The native peptide, as well as the synthetic one, had a female-attracting activity. Sodefrin was found in the apical portion of the epithelial cells of the abdominal gland. Sodefrin is apparently species specific because it did not attract females of Cynops ensicauda. This is the first amphibian pheromone to be identified and the first peptide pheromone identified in a vertebrate.

Amino Acid Sequence↗
PubMed1995

Immunohistochemical evidence that tumors elicit the synthesis of estrogen receptors in the submandibular gland of female rats.

We have demonstrated the presence of estrogen receptor mRNA and the mature protein in the cytoplasm and nucleus, respectively, of a 9,10-dimethyl-1,2-benzathracene-induced submandibular gland tumor in female rats. We have previously shown that progesterone receptors are also present in human salivary gland tumors. These results suggest that endocrine therapy may be effective in treatment of submandibular gland tumors.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1995

Isolation and the gene cloning of an alkaline shock protein in methicillin resistant Staphylococcus aureus.

The growth of Staphylococcus aureus occurs at a wide range of pH(5-10), while the optimal is pH 7.0-7.5. The molecular mechanism of such pH tolerant properties should be elucidated because the production of the virulence factors was greatly affected by environmental pH. The effect of pH shift on the composition of cytosolic proteins in S. aureus was examined. A protein with a molecular mass of 23 kDa was remarkably enhanced by a pH upshift from 7 to 10. This alkaline shock protein (ASP23) was isolated and purified by ion-exchange chromatography. The N-terminal sequences of the purified protein and the protease-digested peptides were analyzed. The 320-bp DNA fragment that was designed from the peptide analysis was amplified. Using the amplified fragment as a probe, the ASP gene, asp23, was cloned. The deduced primary sequence of ASP23 comprised 169 amino acids with a calculated molecular weight of 19,191. Northern analysis revealed that asp23 was positively regulated at the transcription level by alkaline shock. Homology search revealed that asp23 is a novel gene. Although the physiological role of ASP23 has yet to be further analysed, we suggest that ASP23 plays a key role in alkaline pH tolerance of S. aureus.

Amino Acid Sequence↗
PubMed1995

Platelet-derived growth factor triggers translocation of the insulin-regulatable glucose transporter (type 4) predominantly through phosphatidylinositol 3-kinase binding sites on the receptor.

Insulin is the only known hormone which rapidly stimulates glucose uptake in target tissues, mainly by translocation to the cell surface of the intracellular insulin-regulatable glucose transporter (glucose transporter type 4, GLUT4). We have developed a cell line for direct, sensitive detection of GLUT4 on the cell surface. We have suggested that insulin-activated phosphatidylinositol (PI) 3-kinase may be involved in the signaling pathway of insulin-stimulated GLUT4 translocation. We report that platelet-derived growth factor (PDGF), which stimulates PI 3-kinase activity, triggers GLUT4 translocation in Chinese hamster ovary (CHO) cells stably overexpressing the PDGF receptor and in 3T3-L1 mouse adipocytes. Using mutant PDGF receptors that cannot bind to Ras-GTPase-activating protein, phospholipase C-gamma, and PI 3-kinase, respectively, we obtained evidence that PI 3-kinase binding sites play a key role in the signaling pathway of PDGF-stimulated GLUT4 translocation in the CHO cell system.

3T3 Cells↗
PubMed1995

Incorporation of acetyl-CoA generated from peroxisomal beta-oxidation into ethanolamine plasmalogen of rat liver.

We have reported that peroxisomal beta-oxidation has an anabolic function, supplying acetyl-CoA for biosyntheses of bile acids and phospholipids. Here we deal with its role in the biosynthesis of the subclasses of ethanolamine- and choline-containing phosphoglycerides (EPG, CPG, respectively). Rats were fed for 2 weeks on chow containing 0.25% clofibrate, which inhibits cholesterol and bile acid biosyntheses, but stimulates peroxisomal beta-oxidation. [1-14C]Lignoceric acid, which is exclusively degraded by peroxisomal beta-oxidation to acetyl-CoA, was intravenously injected, and 3 h later the rats were killed. The EPG-rich and CPG-rich fractions were prepared from the liver. When they were treated with phospholipase A2, the radioactivity was predominantly recovered in the 1-radyl group. The radioactivity in EPG was easily dissociated with HCl vapor, and the lipid containing radioactivity was found to be a fatty aldehyde mixture consisting of steary aldehyde (approx. 58%) palmityl aldehyde (approx. 40%) and oleyl aldehyde (approx. 2%). Thus, in the case of EPG, acetyl-CoA from peroxisomal beta-oxidation is incorporated mainly into the 1-alkenyl group of ethanolamine plasmalogen. The radioactivity in CPG, however, was found in fatty alcohol (formed from fatty acid), but not in alkylglycerol after reduction of the fraction with Vitride. Thus, in the case of CPG, acetyl-CoA from peroxisomal beta-oxidation is exclusively incorporated into the 1-acyl group of diacyl glycerophosphocholine, but not into the 1-alkyl group. The above results were supported by the results of phospholipase C treatment. The above data indicate that peroxisomal beta-oxidation plays a role in supplying acetyl-CoA for 1-alkenyl group of plasmalogen-type phospholipid, but this channel may open only to synthesis of EPG, and almost not to CPG.

Acetyl-CoA C-Acyltransferase↗
PubMed1995

Involvement of preferential formation of apurinic/apyrimidinic sites in dimethylarsenic-induced DNA strand breaks and DNA-protein crosslinks in cultured alveolar epithelial cells.

We previously found that lung-specific DNA damage induced by administration of dimethylarsinic acid (DMAA), a main metabolite of inorganic arsenics in mammals, in mice might be due to dimethylarsenic peroxyl radical [(CH3)2AsOO.] produced in the further metabolic processing of DMAA. Further analysis of DNA damage was performed in the present study using a human embryonic cell line of alveolar epithelial (L-132) cells. Alkali-labile sites in DNA were produced prior to DNA single-strand breaks (SSB) and DNA-protein crosslinks (PC) in L-132 cells by exposure to 10mM DMAA. An experiment using methoxyamine (MA), an agent reacting with the aldehyde group of apurinic/apyrimidinic (AP) sites in DNA, indicated that, of the alkali-labile sites formed by exposure to DMAA, major ones were AP sites. These findings suggest that SSB and PC induced by exposure of L-132 cells to DMAA occurred via the formation of AP sites in DNA. That is, SSB were produced by a beta-elimination reaction on AP sites in the DNA and PC by a Schiff-base reaction between amino groups of nuclear proteins and aldehyde groups of AP sites.

Cacodylic Acid↗
PubMed1995

Evaluation of QRST isointegral maps in detecting posterior myocardial infarction with and without conduction disturbance.

We investigated the usefulness of QRST isointegral maps (I-maps) for detecting posterior myocardial infarction (MI) with and without conduction disturbance. The I-maps were recorded during sinus rhythm and right ventricular (RV) pacing, which simulated left bundle-branch block (LBBB) in 19 patients with and in 20 patients without MI. Data on 608 normal subjects were used as controls. The "-2 SD area," where the QRST integral value was less than the lower limit of the normal range, was assessed by sigma DM (sum of QRST integral values below the normal range). Posterior MI was diagnosed with a sensitivity of 84%, a specificity of 90%, and a diagnostic accuracy of 87%, assuming that MI was present if sigma DM exceeded 50 mVms. During simulated LBBB, when the criterion sigma DM more than 250 mVms was used, the sensitivity, specificity, and diagnostic accuracy were 79, 75, and 77%, respectively. Thus, I-maps may be useful in detecting posterior MI in patients with and without an intraventricular conduction disturbance.

Adult↗
PubMed1995

Transformation of Synechococcus with a gene for choline oxidase enhances tolerance to salt stress.

Choline oxidase, isolated from the soil bacterium Arthrobacter globiformis, converts choline to glycinebetaine (N-trimethylglycine) without a requirement for any cofactors. The gene for this enzyme, designated codA, was cloned and introduced into the cyanobacterium Synechococcus sp. PCC 7942. The codA gene was expressed under the control of a strong constitutive promoter, and the transformed cells accumulated glycinebetaine at intracellular levels of 60-80 mM. Consequently the cells acquired tolerance to salt stress, as evaluated in terms of growth, accumulation of chlorophyll and photosynthetic activity.

Adaptation, Physiological↗
PubMed1995

Thioredoxin h is one of the major proteins in rice phloem sap.

Sieve tubes play important roles in the transfer of nutrients as well as signals. Hundreds of proteins were found in pure phloem sap collected from rice (Oryza sativa L. cv. Kantou) plants through the cut ends of insect stylets. These proteins may be involved in nutrient transfer and signal transduction. To characterize the nature of these proteins, the partial amino-acid sequence of a 13-kDa protein, named RPP13-1, that was abundant in the pure phleom sap was determined. A cDNA clone of 687 bp, containing an open reading frame of 122 amino acids, was isolated using corresponding oligonucleotides as a probe. The deduced amino-acid sequence was very similar to that of the ubiquitous thiol redox protein, thioredoxin. The consensus sequences of thioredoxins are highly conserved. No putative signal peptide was identified. Antiserum against wheat thioredoxin h cross-reacted with RPP13-1 in the phloem sap of rice plants. RPP13-1 produced in Escherichia coli was reactive to antiserum against wheat thioredoxin h. Both E. coli-produced RPP13-1 and the phloem sap proteins catalyzed the reduction of the disulfide bonds of insulin in the presence of dithiothreitol. These results indicate that an active thioredoxin is a major protein translocating in rice sieve tubes.

Amino Acid Sequence↗
PubMed1995

Effects of hypophysectomy on soleus muscle fibers and spinal motoneurons in rats.

The fiber type distribution of the soleus muscle in male and female rats was investigated 4 weeks after hypophysectomy. Oxidative enzyme activity of the soleus motoneurons in the spinal cord was also examined by enzyme histochemical assay. In male rats, the total number of fibers in the soleus muscle was not changed after hypophysectomy, but the percentage of intermediate (INT) fibers (with intermediate adenosine triphosphatase activity following alkaline preincubation, and high succinate dehydrogenase and alpha-glycerophosphate dehydrogenase activities) was increased. All types of fibers in the soleus muscle of hypophysectomized rats showed high adenosine triphosphatase activity following acid preincubation. Oxidative enzyme activity of the motoneurons innervating the soleus muscle was not changed after hypophysectomy. Similar results were obtained in female rats. It is suggested that the increased percentage of INT fibers in the rat soleus muscle after hypophysectomy is due to a lack or reduced levels of growth hormones, and that the metabolic capacities of the muscle fibers and of the innervating motoneurons are affected independently by hypophysectomy.

Animals↗
PubMed1995

Surgical treatment of an enormous aneurysmal portahepatic venous fistula: report of a case.

We report herein the case of a 20-year-old woman in whom an enormous aneurysmal portahepatic venous fistula was found. The portal aneurysm developed in the anterior inferior segment of the right hepatic lobe, and communicated with the right portal vein and the right hepatic vein. Due to the enormous size of the shunt, and because the patient's venous blood ammonia level increased by about twofold after eating, a right lobectomy of the liver was performed. A review of the available literature and a discussion of the most appropriate treatment follows the presentation of this case.

Adolescent↗
PubMed1995

Effects of hypobaric hypoxia on histochemical fibre-type composition and myosin heavy chain isoform component in the rat soleus muscle.

Histochemical fibre-type composition and myosin heavy chain isoform component in the soleus muscle were studied in normoxic rats at postnatal ages of 5, 10, 15, and 20 weeks and in rats exposed to hypobaric hypoxia (460 torr) for 5 weeks from postnatal ages of 5, 10, and 15 weeks. The increase in the percentage of type I fibres and the concomitant decrease in that of type IIa fibres in the soleus muscle of normoxic rats were observed until 15 weeks of age. On the other hand, no change in the fibre-type composition of the muscle during postnatal development was observed in hypoxic rats, irrespective of the age at which they were exposed to hypoxia. The changes in the myosin heavy chain isoform component (MHC I and MHC IIa) of the muscle during postnatal development and by hypoxia corresponded well with those in the muscle fibre-type composition. It is concluded that hypobaric hypoxia inhibits the growth-related shift of muscle fibre-types from type IIa to type I and of myosin heavy chain isoforms from MHC IIa to MHC I in the rat soleus muscle, and that there are no changes in the muscle fibre-type composition or the myosin heavy chain isoform component caused by hypoxia after the shifts in these parameters which occur during postnatal development are completed.

Aging↗