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T Ichida

Publications and source records attributed to T Ichida.

At least 73 records · Page 4Linked to original sources
PubMed1997

Evidence for the putative docking/fusion complex of exocytosis in parotid acinar cells.

In lysates of the rat brain, the SNARE complex, a putative membrane fusion machinery of synaptic exocytosis, is extremely stable and is detected after SDS-PAGE. Applying this technique to parotid acinar cells, however, we could only detect the monomeric VAMP-2, but not the high molecular forms associated with other components of the SNARE complex. Parotid acini did not contain brain-type t-SNAREs, but contained NSF and alpha SNAP. When VAMP-2 was immunoprecipitated from parotid acinar cell lysates, NSF and alpha SNAP were coprecipitated with it. Since NSF and alpha SNAP are unable to bind directly to VAMP-2 but indirectly bind via t-SNAREs, the immunoprecipitate very likely contained unidentified t-SNAREs.

Animals↗
PubMed1997

Amplification of BCR protein associated with oncogenesis in human hepatocellular carcinoma.

The BCR gene is located on human chromosome 22. The normal cellular BCR gene encodes a 160,000-dalton phosphoprotein associated with a serine/threonine kinase activity. The BCR protein is involved in signal transduction. We investigated the expression of the BCR protein in hepatocellular carcinoma (HCC), surrounding noncancerous liver tissue, liver cirrhosis (LC), chronic hepatitis (CH), and normal liver with immunohistochemistry and a western blot analysis. BCR immunoreactivity was detected using a monoclonal antibody. In normal liver, and both CH and LC without association of HCC, the immunoreactivity of the BCR protein was minimal. In contrast, 73% (22 of 30) of noncancerous liver tissue adjacent to the HCC and 40% (12 of 30) of HCC expressed BCR protein; this difference was statistically significant (P < 0.01). The expression of the BCR protein expression correlated with the degree of histological differentiation of HCC (P < 0.05). In addition, the amplification of BCR protein in noncancerous cells was supported by the detection of specific protein using a western blot analysis. In two cases, the expression of BCR protein occurred only in overtly malignant HCC cells. As a result, the expression of the BCR protein may be associated with oncogenesis in human HCC.

Aged↗
PubMed1997

Preventive and therapeutic effects in rats of hepatocyte growth factor infusion on liver fibrosis/cirrhosis.

Liver fibrosis/cirrhosis is characterized by hyper-accumulation of fibrous tissue components and is commonly observed in later or terminal states of chronic hepatic diseases. In ongoing work, we found that the administration of human recombinant hepatocyte growth factor (hrHGF) suppressed the onset of liver fibrosis/cirrhosis in several distinct models and accelerated the recovery from liver fibrosis/cirrhosis in rats. Repeated administration of porcine serum for 10 weeks to rats induced liver fibrosis without any accompanying hepatocellular injuries; in addition, the intravenous (i.v.) administration of hepatocyte growth factor (HGF) to these rats suppressed increases in fibrous components and hydroxyproline contents in the liver, thus preventing the onset of liver fibrosis. Repeated administration of dimethylnitrosamine (DMN) for four weeks induced liver cirrhosis, as characterized by the hyper-accumulation of fibrous components, infiltration of mononuclear leukocytes, and hepatic dysfunction. When HGF was injected daily for four weeks along with DMN-treatment, the onset of DMN-induced hepatic fibrosis/cirrhosis was suppressed; the numbers of infiltrating mononuclear cells, fibrous tissue components, and hydroxyproline content in the liver were decreased. When HGF was injected for two weeks following four weeks of DMN-treatment, HGF accelerated the recovery from liver cirrhosis and prevented death due to hepatic dysfunction. Likewise, HGF-injection suppressed the onset of liver fibrosis, when liver fibrosis had been induced by long-term treatment with carbon tetrachloride (CCl4). Thus, the administration of HGF holds great promise for treating subjects with liver fibrosis/cirrhosis as a result of chronic hepatic injury.

Alanine Transaminase↗
PubMed1997

Regulation of CREB phosphorylation by cAMP and Ca2+ in parotid acinar cells.

Since various secretory stimuli regulate not only secretion but also protein, RNA, and DNA syntheses in salivary glands, we evaluated the effect of secretory stimuli on the phosphorylation state of CREB (cAMP response element-binding protein). Isoproterenol, forskolin, and CPS-cAMP markedly stimulated the phosphorylation of CREB in parotid acinar cells, and PKA inhibitors H-8 and H-89 dose-dependently inhibited it. In contrast, carbachol (CCH) and A23187 decreased CREB phosphorylation, but CCH did not decrease it in the absence of extracellular Ca2+. Although protein phosphatase inhibitor calyculin A alone markedly increased the phosphorylation, it could not prevent CCH-induced dephosphorylation of CREB. CaM kinase IV, a putative protein kinase for CREB in response to Ca2+ elevation, was undetectable in parotid acinar cells.

Adrenergic beta-Agonists↗
PubMed1997

Role of Ca2+-independent phospholipase A2 in exocytosis of amylase from parotid acinar cells.

We evaluated the role of cytosolic phospholipase A2 (PLA2) in the exocytosis of amylase from parotid acinar cells. The exocytosis stimulated by isoproterenol was dose-dependently inhibited by bromoenol lactone (BEL), a potent suicide inhibitor of Ca2+-independent cytosolic PLA2. The IC50 value of BEL was approximately 7 microM. AACOCF3, a selective inhibitor of Ca2+-dependent cytosolic PLA2, did not inhibit the exocytosis at least up to 30 microM. BEL also inhibited amylase release evoked by forskolin and membrane-permeable cAMP, but it did not inhibit cAMP-dependent protein kinase activity. PLA2 activity in parotid acinar cells was found to be predominantly Ca2+-independent, and was strongly inhibited by BEL, whose IC50 value was approximately 2 microM when it was applied to intact acini. Although isoproterenol scarcely enhanced [3H]arachidonic acid release from intact acinar cells, BEL dose-dependently decreased the basal arachidonic acid release to approximately one half of the control value. These results suggest that the cytosolic Ca2+-independent PLA2 activity plays a role in the membrane fusion process of exocytosis in parotid acinar cells.

Amylases↗
PubMed1997

Risk factors and the effect of interferon therapy in the development of hepatocellular carcinoma: a multivariate analysis in 343 patients.

The aims of the present study were to clarify the risk factors for the development of hepatocellular carcinoma (HCC) in chronic hepatitis C virus (HCV) infection and to investigate the effectiveness of interferon (IFN) therapy. We retrospectively studied 343 patients who had been admitted to our hospital; 161 with chronic hepatitis, 49 with liver cirrhosis, 42 with chronic hepatitis bearing HCC and 91 with liver cirrhosis bearing HCC. The mean (+/- SD) observation period was 41.6 +/- 31.1 months. The mean age of HCC and non-HCC patients was 63.5 +/- 7.6 and 56.9 +/- 12.5 years, respectively (P < 0.001). The HCV genotype II (1b) was the most prevalent genotype (92.5%) in HCC patients and the mean age was higher among patients with this genotype (63.6 +/- 7.7 years). Multivariate analysis identified age (P < 0.001), the male gender (P < 0.01), HCV genotype II (1b) (P < 0.05) and excessive alcohol intake (P < 0.05) as independent factors associated with the development of HCC. There was no relationship between the development of HCC and serum HCV levels as quantified by branched DNA assay or competitive reverse transcription polymerase chain reaction. The incidence of HCC in patients who had not received IFN therapy was 10.4/100 person-year, while that of patients who had received IFN therapy was 1.2/100 person-year (P < 0.01) by the person-year method. The low incidence of HCC in patients treated with IFN suggests that IFN may prevent the development of HCC.

Aged↗
PubMed1997

Metallothionein expression and concentrations of copper and zinc are associated with tumor differentiation in hepatocellular carcinoma.

Metallothionein is the carrier protein of heavy metal ions, such as copper (Cu) and zinc (Zn). In this study, the relationships among immunohistochemical expression of metallothionein, concentrations of Cu and Zn, histological differentiation and proliferative activity of hepatocellular carcinoma were investigated in 51 cases. The concentrations of Cu and Zn in both tumor and non-tumor tissues were determined using electron probe microanalysis. Immunohistochemical expression of metallothionein in tumor tissues decreased with the degree of differentiation, whereas the number of hepatocytes positive for Ki-67 increased. Furthermore, the concentrations of Cu and Zn in tumor tissues decreased with the degree of histological differentiation in human hepatocellular carcinoma.

Biomarkers, Tumor↗
PubMed1997

A case of idiopathic thyrotropin (TSH) deficiency.

The first case of idiopathic thyrotropin (TSH) deficiency in an old woman with thyroid functioning adenoma was reported. She got subtotal thyroidectomy before about four years of her admission to our hospital because of fatigability, puffy face and leg edema. At time, she had low TSH and free T4 levels despite replacement therapy with desiccated thyroid. No response of only serum TSH after administration of combined stimulant containing TRH and repeated TRH suggested the failure of TSH secretion. CT MRI did not show any abnormality. These results indicated that her hypothyroidism was due to acquired idiopathic TSH deficiency.

Adenoma↗
PubMed1996

Effect of genistein on amylase release and protein tyrosine phosphorylation in parotid acinar cells.

We evaluated the role of protein tyrosine phosphorylation in amylase exocytosis from parotid acinar cells by using genistein, a tyrosine kinase inhibitor. Amylase release stimulated by isoproterenol was dose-dependently inhibited by genistein. Genistein also inhibited the exocytosis evoked by dibutyryl- or 8-chlorophenylthio-cAMP. Daidzein, a negative control agent of genistein, elicited no inhibitory effect. Isoproterenol had dual effects on protein tyrosine phosphorylation; it increased that phosphorylation of 190- and 210-kDa proteins and decreased that of a 90-kDa one. The phosphorylation was dose-dependently inhibited by genistein but not by daidzein. These results suggest that protein tyrosine phosphorylation plays a role in the process of amylase exocytosis from parotid acinar cells.

Amylases↗
PubMed1996

Induction of amylase release from rat parotid acinar cells by cooling in vitro.

As amylase exocytosis from parotid acinar cells is an energy-dependent process, it was supposed that it could be terminated by cooling on ice. Unexpectedly, however, the cooling itself markedly induced amylase release from parotid acini. The release finished within 1 min and prolonged incubation on ice did not cause further release. The cold-induced amylase release was observed in the absence of extracellular calcium, and calcium ionophore A23187 neither enhanced nor inhibited it. Treatments with cytochalasin D, phalloidin, or taxol did not disturb the release. Cold treatment did not increase the leakage of lactate dehydrogenase, a cytosolic enzyme, and the acini still maintained normal responsiveness to isoproterenol. Electron-microscopic observation revealed that the plasma membrane and zymogen granules of cold-exposed acini were intact, but many acinar lumina were distended with secretory materials. These results suggest that the cold treatment induces transient amylase release by the fusion of plasma membrane and the zymogen granules that have been closely docked at the luminal membrane.

Amylases↗
PubMed1996

Age-related decrease of gamma-aminobutyric acid (GABA) release in brain of spontaneously hypertensive rats.

We studied the developmental alteration of GABA release in spontaneous ly hypertensive(SHR) and normotensive Wistar-Kyoto rat(WKY) brain. The release of [3H]GABA observed under high potassium(30 mM) in eleven-week-old(hypertensive) SHR hippocampus and the spontaneous release of [3H]GABA in the same aged SHR medulla oblongata were lower than those of age-matched WKY. We conclude that the GABAergic mechanisms may be different in SHR and WKY brain and may be associated with the development of hypertension.

Age Distribution↗
PubMed1996

GABAB-ergic stimulation in hypothalamic pressor area induces larger sympathetic and cardiovascular depression in spontaneously hypertensive rats.

To determine whether central GABA (gamma-aminobutyric acid) B receptor stimulation would affect the sympathetic and cardiovascular activities, baclofen (a GABAB receptor agonist) was injected into lateral cerebral ventricles (intracerebroventricularly, ICV) in urethane-anesthetized normotensive rats. Intracerebroventricular injections of GABAA agonist (muscimol, 1 microgram) consistently decreased blood pressure and heart rate. In contrast ICV injections of baclofen (2 micrograms) increased blood pressure (BP) and heart rate with initial transient cardiovascular depression, and these effects of baclofen were abolished by ICV pretreatment with GABAB antagonist (saclofen, 100 micrograms). To determine whether the cardiovascular effects of ICV injections were elicited by activating GABA receptors in the hypothalamus, we injected baclofen or muscimol directly into various hypothalamic areas. Baclofen (100 and 800 ng) injected into the ventromedial hypothalamus (VMH) or posterior hypothalamus (PH) of normotensive rats produced dose-related decreases in sympathetic nerve activity, blood pressure, and heart rate. These effects of baclofen were larger in VMH injections than in PH injections. The depressor responses elicited by VMH injections of baclofen were abolished by intravenous pretreatment with alpha-blocker, but unaffected by parasympathetic blocker, further indicating that the depressor responses of baclofen (VMH) were not due to parasympathetic activation, but due to peripheral sympathetic depression. Muscimol (400 ng) and baclofen (800 ng) injected into VMH produced similar amplitude of sympathetic-depressant, depressor and bradycardic responses. In contrast, BP was increased by the same dose of baclofen injected into the hypothalamic depressor area (anterior hypothalamus, AH), but was unaffected by muscimol. Final experiments were performed to determine whether these sympathetic and cardiovascular effects to hypothalamic GABAB stimulations would be altered in hypertension. In spontaneously hypertensive rats (SHR), basal BP and heart rate were already higher than in normotensive controls (Wistar-Kyoto rat, WKY). Baclofen injected into VMH reduced sympathetic nerve activity, BP, and heart rate in both groups of rats, and these effects were significantly larger in SHR than in WKY. This enhanced depressor response induced by baclofen (VMH) in SHR persisted even after sinoaortic denervation, which indicates that the enhanced depressor response is not due to reduced peripheral baroreflex sensitivity in SHR. On the other hand, baclofen injected into AH increased BP and heart rate in both WKY and SHR, but the magnitude of these responses did not differ between two groups. In summary, GABA reduces sympathetic nerve activity, BP, and heart rate through both GABAA and B receptors in VMH. The GABAB system acts on the depressor area, AH, to further regulate the cardiovascular activities. In SHR, the GABAB-ergic system in VMH but not in AH is altered, and this might contribute to the development of hypertension.

Animals↗
PubMed1996

Inhibitory guanine nucleotide regulatory protein alpha-subunits in brain of spontaneously hypertensive rats.

Previously we have reported a decreased GABAB receptor expression in brain of spontaneously hepertensive rats (SHR). Moreover, decreased receptor numbers were accompanied by depressed stimulation of cAMP formation. We have now quantified Gi alpha protein by immunoblotting in cerebral membranes from 11-week-old normotensive Wistar-Kyoto rats (WKY) and hepertensive SHR. The levels of the alpha-subunit in the two sets of membranes were similar. In conclusion, the reduced response in adenylate cyclase activity to agents that function via the Gi protein, e.g., GABAB receptor agonists, in SHR brain is not a consequence of altered level of Gi alpha protein.

Adenylyl Cyclases↗
PubMed1996

Disappearance of gamma-aminobutyric acid (GABA)B receptor-mediated cAMP suppression in mouse cerebrum after chronic treatment with morphine.

The effects of chronic morphine administration (dependence) and naloxone-induced withdrawal on cerebral GABAB receptor and its signal transduction system were examined. Alterations in receptor affinity and number and in the amount of Gi protein were determined by radioligand binding assay and immunoblotting with Gi protein antibody, respectively. [3H]GABA binding to GABAB receptors in the brain of morphine-dependent and -withdrawn mice showed no significant change in either high or low affinity sites. Similarly, no alterations were noted in the coupling between GABAB receptor and Gi protein or in the amount of protein. However, the suppressive effect of baclofen, a GABAB agonist, on forskolin-stimulated cAMP formation in cerebral cortical slices of these animals was abolished. These results indicate that chronic morphine administration may induce functional deterioration in the coupling between Gi protein and the adenylate cyclase system.

Animals↗
PubMed1996

Dephosphorylation of cofilin in parotid acinar cells.

Cofilin is an actin-depolymerizing protein, whose depolymerizing activity is supposed to be regulated in part by phosphorylation and dephosphorylation. Thus, we studied the phosphorylation states of cofilin in rat parotid acinar cells during stimulation for amylase exocytosis. Isoproterenol and carbachol induced rapid and extensive dephosphorylation of cofilin; 60-70% dephosphorylation was clearly detectable within 1 min. Membrane-permeable cyclic AMP (CPS-cAMP), phorbol ester (PMA), and Ca ionophore A23187 mimicked the effect of isoproterenol and carbachol. Protein phosphatase inhibitors (calyculin A or FK506 plus cyclosporin A) did not block the dephosphorylation in response to isoproterenol or carbachol. Furthermore, calyculin A alone strongly dephosphorylated cofilin. Although no exogenous protein phosphatases tested dephosphorylated cofilin in the homogenate, the cofilin that was isolated by immunoprecipitation was clearly dephosphorylated by protein phosphatases 1, 2A, and 2C.

Actin Depolymerizing Factors↗
PubMed1996

Localization of hyaluronan in human liver sinusoids: a histochemical study using hyaluronan-binding protein.

Circulating hyaluronan is mostly derived from lymph, fibroblast and Ito cells in the liver, and more than 90% of hyaluronan is degraded in hepatic sinusoidal endothelial cells. Thus, elevated serum hyaluronan is regarded as an indication of hepatic fibrosis with activated Ito cells and dysfunctional sinusoidal endothelial cells. We studied the distribution of hyaluronan in human liver sinusoids to determine the influences on elevated hyaluronan levels in sera. Histochemical examination was made using hyaluronan-binding protein (HABP) and serial sections of liver tissue for staining of alpha-smooth muscle actin (ASMA) (an indicator of activated Ito cells) and of ulex europaeus agglutinin I lectin (UEA-1) (closely related to hepatic sinusoidal capillarization). Positive staining, indicating the presence of hyaluronan, was noted in fibrous regions around the portal tracts, areas of focal necrosis in the liver parenchyma, and walls of the sinusoids in chronic hepatitis. In this group, hyaluronan-positive areas corresponded to positive ASMA staining and faint staining of UEA-1. On the contrary, in liver cirrhosis, UEA-1-positive areas were essentially identical to hyaluronan-positive areas and to ASMA-negative areas in sinusoidal walls. Hyaluronan and ASMA could be detected in the same areas of sinusoidal walls in chronic hepatitis, but not in liver cirrhosis. Hyaluronan appears to be mainly related to the staining of activated Ito cells in chronic hepatitis. Therefore, we concluded that in chronic hepatitis, the production of hyaluronan was accelerated in Ito cells; however, degradation of hyaluronan by sinusoidal endothelial cells continued. On the contrary, in liver cirrhosis, hyaluronan production decreased in Ito cells, and a marked transformation of sinusoidal endothelial cells with hepatic sinusoidal capillarization indicated loss of the ability to degrade hyaluronan. These different mechanisms in chronic hepatitis and liver cirrhosis may operate in the sinusoidal walls and may cause the elevation of hyaluronan in sera.

Biomarkers↗