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J Yamada

Publications and source records attributed to J Yamada.

At least 163 records · Page 9Linked to original sources
PubMed1997

Effects of aldose reductase inhibitor CT-112 on the corneal epithelial barrier of galactose-fed rats.

PURPOSE: To investigate whether the barrier function of the corneal epithelium is disrupted in galactosemic rats, and to assess the effects of the aldose reductase inhibitor CT-112, in the form of eyedrops, on the corneal epithelial barrier in galactosemic rats. METHODS: Forty rats were divided into 3 groups based on their diet: a control group, a galactose group and a CT-112 treated galactose group (CT-112 group). After 3 weeks, 31 rats from the 3 groups were subjected to fluorophotometry, in which fluorescein (F) was instilled into one eye and carboxyfluorescein (CF) was instilled into the other eye in a random fashion. The F and CF uptakes were then measured at the central cornea by a slit-lamp fluorophotometer. Three rats from each group were exposed to a horseradish peroxidase (HRP) solution for one hour, and the HRP-reactive substances within the corneal epithelium were also examined via electron microscopy. RESULTS: There was significantly higher F uptake in the galactose group than in the control (p = 0.003) and CT-112 groups (p = 0.028). There were no significant differences in CF uptake between the 3 groups. Histologically, HRP-reactive substances were found in much greater quantities within the superficial corneal cells of the galactose group than in the control or CT-112 groups. CONCLUSIONS: These results suggest that cell membrane disruption, as detected by F uptake and HRP penetration, was found in the superficial corneal cells of galactose-fed rats, and that intercellular junction integrity can be assayed by CF uptake and histological evaluation. Moreover, CT-112 eyedrops were effective in improving the corneal epithelial barrier dysfunction of galactose-fed rats.

Aldehyde Reductase↗
PubMed1997

Molecular mechanisms for somatostatin inhibition of c-fos gene expression.

We reported previously that somatostatin inhibits the expression of the immediate early gene c-fos. Accordingly, we characterized the molecular mechanisms by which somatostatin inhibits c-fos gene expression. Because growth factors activate c-fos through a region of its promoter known as the serum response element [SRE; base pairs (bp) -357 to -276] we transfected rat pituitary adenoma cells (GH3) with plasmids containing the SRE or the SRE core fragment (bp -320 to -298) upstream of the luciferase reporter gene. Epidermal growth factor (EGF) stimulated SRE-luciferase activity, and this effect was inhibited by somatostatin and by the analog MK-678. Identical results were obtained with the SRE core plasmid, demonstrating that the sequence between bp -320 and -298 of the c-fos promoter is a somatostatin response element. Because the extracellular signal-regulated protein kinases (ERKs) induce the SRE via phosphorylation of transcription factors such as Elk-1, we examined the effect of somatostatin on ERK phosphorylation and activation. EGF stimulated tyrosine phosphorylation of ERK2, and MK-678 attenuated this effect. In experiments using in-gel kinase assays, MK-678 also inhibited EGF-stimulated ERK activity via a pertussis toxin sensitive pathway, and this effect resulted in inhibition of Elk-1 transcriptional activity. Our data suggest that one mechanism of somatostatin action involves inhibition of ERK activity, Elk-1 phosphorylation and transcriptional activation, and ultimately c-fos gene transcription.

Animals↗
PubMed1997

Molecular mechanisms for the growth factor action of gastrin.

We have previously observed that gastrin has a cholecystokinin B (CCK-B) receptor-mediated growth-promoting effect on the AR42J rat pancreatic acinar cell line and that this effect is paralleled by induction of expression of the early response gene c-fos. We undertook these experiments to elucidate the mechanism for induction of c-fos and the linkage of this action to the trophic effects of gastrin. Gastrin (0.1-10 nM) dose dependently induced luciferase activity in AR42J cells transfected with a construct consisting of a luciferase reporter gene coupled to the serum response element (SRE) of the c-fos promoter. This effect was blocked by the specific CCK-B receptor antagonist D2 but not by the specific CCK-A receptor antagonist L-364,718 or by pertussis toxin, indicating that gastrin targets the SRE via specific CCK-B receptors through a mechanism independent of Gi. Inhibition of protein kinase C (PKC) either by prolonged (24 h) exposure of the cells to the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (100 nM) or by incubation with the selective inhibitor GF-109203X (3.5 microM) resulted in an 80% reduction in luciferase activity. Similar results were observed in the presence of the specific extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor PD-98059 (50 microM). We measured ERK2 activity in AR42J cells via in-gel kinase assays and observed that gastrin (1 pM-100 nM) induced ERK2 enzyme activity in a dose-dependent manner. Addition of GF-109203X and PD-98059, either alone or in combination, produced, respectively, partial and total inhibition of gastrin-induced ERK2 activity. Gastrin induction of ERK2 activity also resulted in a threefold increase in the transcriptional activity of Elk-1, a factor known to bind to the c-fos SRE and to be phosphorylated and activated by ERK2. PD-98059 blocked the growth-promoting effect of gastrin on the AR42J cells, demonstrating that this effect depends on activation of MEK. Our data lead us to conclude that the trophic actions of gastrin are mediated by ERK2-induced c-fos gene expression via PKC-dependent and -independent pathways.

Animals↗
PubMed1997

Functional role of extracellular signal-regulated protein kinases in gastric acid secretion.

Epidermal growth factor (EGF) has acute inhibitory and chronic stimulatory effects on gastric acid secretion. Because a cascade of intracellular events culminating in the activation of a family of serine-threonine protein kinases called extracellular signal-regulated protein kinases (ERKs) is known to mediate the actions of EGF, we undertook studies to explore the functional role of the ERKs in gastric acid secretion. ERK2 was immunoprecipitated from cell lysates of highly purified (> 95%) gastric canine parietal cells, and its activity was quantified using in-gel kinase assays. Of the primary gastric secretagogues, carbachol was the most potent inducer of ERK2 activity. Gastrin and EGF had weaker stimulatory effects, whereas no induction was noted in response to histamine. The effect of carbachol appeared to be independent of Ca2+ signaling. PD-98059, a selective inhibitor of the upstream ERK activator mitogen-activated protein kinase/ERK kinase, dose-dependently inhibited both carbachol- and EGF-stimulated ERK2 activity, with a maximal effect observed between 50 and 100 microM. ERKs activation is required for induction of the early gene c-fos via phosphorylation of the transcription factor Elk-1 which binds to the c-fos serum response element (SRE). Carbachol stimulated a two- to threefold induction of luciferase activity in cultured parietal cells transfected with either a SRE-luciferase reporter plasmid or with a chimeric GAL4-ElkC expression vector and the 5 x GAL-luciferase reporter plasmid. To examine the significance of ERK activation in gastric acid secretion, we tested the effect of PD-98059 on carbachol-stimulated uptake of 14C-labeled aminopyrine (AP). Acute inhibition of the ERKs by PD-98059 led to a small increase in AP uptake and a complete reversal of the acute inhibitory effect of EGF on AP uptake induced by either carbachol or histamine. In contrast, exposure of the cells to PD-98059 for 16 h led to a reversal of the chronic stimulatory effect of EGF on AP uptake induced by carbachol. Our data led us to conclude that carbachol induces a cascade of events in parietal cells that results in ERK activation. Although the acute effect of the ERKs on gastric acid secretion appears to be inhibitory, the activation of transcription factors and of early gene expression could be responsible for its chronic stimulatory effects.

Aminopyrine↗
PubMed1997

Inhibitory effects of a nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), on 2-deoxy-D-glucose-induced hyperglycemia in rats.

The inhibitory effects of a potent nitric oxide (NO) synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), on 2-deoxy-D-glucose (2-DG)-induced hyperglycemia were investigated in rats. L-NAME significantly inhibited 2-DG-induced hyperglycemia, although N(G)-nitro-D-arginine methyl ester (D-NAME) did not affect it. A similar NO synthase inhibitor, N(G)-monomethyl-L-arginine (L-NMMA), also inhibited 2-DG-induced hyperglycemia. The antagonistic effects of L-NAME are unrelated to the cholinergic system, since the muscarinic receptor antagonist scopolamine did not affect 2-DG-induced hyperglycemia. The neuronal NO synthase inhibitor 7-nitroindazole (7-NI) did not reduce 2-DG-induced hyperglycemia, but rather enhanced it. Our results suggest that NO may be involved in glucose homeostasis and that the inhibitory effects of L-NAME on 2-DG-induced hyperglycemia are not related to muscarinic receptors or neuronal NO synthase.

Animals↗
PubMed1997

Histological study of the seminiferous epithelium in the Japanese rat snake, Elaphe climacophora: identification of spermatogonium.

To clarify the features of the seminiferous epithelium of the Japanese rat snake, Elaphe climacophora, the identification of spermatogonium and the examination of features of cell to cell junctions were performed in the present study. As for the identification, 5-bromo-2-deoxyuridine (BrdU) incorporation was examined immunohistochemically to mark spermatogonia. The seminiferous epithelium was observed throughout a year at the electron microscopic level. BrdU immunoreactivity was detected not only in the cells of the first layer of the seminiferous epithelium but also in the second and/or third layers. The cells immunoreactive in the first layer did not seem to attach to the basement membrane and were recognized throughout a year. To investigate cell to cell junctions, we performed actin filament detection by phalloidin staining. Distribution of actin filaments was different from that in mammalian species. At the ultrastructural level, Sertoli-Sertoli cell junctions were observed. Sertoli cells formed junctional complexes. Tight junctions were clearly found, but lacked the backing by actin filaments. These results indicate that the blood-testis barrier of the Japanese rat snake was structurally different from that of mammalian species. In conclusion, the seminiferous epithelium of the Japanese rat snake is intermediate in morphology between amphibians and mammals.

Actins↗
PubMed1997

Induction of anterior chamber-associated immune deviation by corneal allografts placed in the anterior chamber.

PURPOSE: Although mice with long-accepted orthotopic corneal allografts display donor-specific anterior chamber-associated immune deviation (ACAID), this deviant response is not detected until well after the fate of the grafts is decided. To determine the efficiency with which corneal tissue itself can induce ACAID, allogeneic corneal segments were inserted into anterior chambers (AC) of normal mouse eyes. METHODS: Central corneas from normal eyes of C57BL/6 (allogeneic) and BALB/c (syngeneic) donors were cut into wedge-shaped fragments measuring approximately 0.3 x 2.0 mm (in some experiments the corneal epithelium was removed) and inserted into the AC adjacent to recipient endothelium. Recipients of these fragments were evaluated for donor-specific delayed hypersensitivity (DH) and ACAID, and fragment-containing eyes were tested for their capacity to support ACAID to an irrelevant antigen. RESULTS: Syngeneic and allogeneic corneas survived indefinitely in the AC without evidence of inflammation or rejection. Although fragments of cornea (with or without epithelial layers) placed at extraocular sites were potent inducers of DH, within the eye only epithelium-bearing grafts induced DH. Moreover, this DH response was short-lived. Recipients of allogeneic corneal fragments in the AC developed ACAID by 8 weeks, but not at 1 week. Moreover, fragment-containing eyes supported ACAID induction when bovine serum albumin was injected into the AC. CONCLUSIONS: Anterior chamber-associated immune deviation can be induced by allogeneic corneal tissue inserted into the AC, but its onset is delayed. The delay may be dictated by persistence of donor epithelium on the graft, which promotes DH. Once the epithelium is lost, DH disappears and ACAID emerges. Anterior chamber-associated immune deviation may contribute to the maintenance of corneal allograft viability.

Animals↗
PubMed1997

[Efficacy and safety of intramuscular imipenem/cilastatin (IPM/CS) for complicated urinary tract infections].

An intramuscular preparation of imipenem/cilastatin (IPM/CS, 500 mg/500 mg) was administered to 59 patients with complicated urinary tract infections (UTI; cystitis and pyelonephritis) to evaluate its efficacy and safety. The obtained results are summarized as follows: In patients with cystitis, evaluations based on daily frequencies of administration were also performed. 1) According to the treating doctors, the drug showed an overall efficacy rate of 80% (45/56 patients). The efficacy rate was 89% in patients with cystitis treated by a u.i.d. regimen. Among patients treated by a b.i.d. regimen, the efficacy rate was 67% for cystitis cases and 84% for pyelonephritis cases. 2) When clinical efficacy was assessed according to the criteria for UTI drug efficacy evaluation, the drug was 'markedly effective' in 14 patients, 'effective' in 23, and ineffective in 11 patients, for an efficacy rate of 77% (37/48 patients). 3) The microbiological eradication rate was 88% (59/67 strains). The rate was 95% (20/21 strains) for Gram-positive bacteria and 85% (39/46 strains) for Gram-negative bacteria. The efficacy for Enterobacter faecalis and Pseudomonas aeruginosa was 100% and 73%, respectively. 4) As side effects, pain at the injection site was reported by one patient and abnormal laboratory test values were observed in 2 patients. All of these reactions were mild and resolved shortly after the completion of treatment. Based on these findings, it is concluded that this intramuscular preparation of IPM/CS is effective for treating complicated urinary tract infections.

Adolescent↗
PubMed1996

Effects of a nitric oxide synthase inhibitor on 5-HT1A receptor agonist 8-OH-DPAT-induced hyperphagia in rats.

We investigated nitric oxide (NO) involvement in the hyperphagia induced by the 5-HT1A receptor agonist 8-hydroxy-2-di-n-(propylamino)tetralin (8-OH-DPAT). A NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), dose dependently inhibited 8-OH-DPAT-induced eating in freely feeding rats. However, the inactive isomer D-NAME was without effect. The inhibitory effects of L-NAME on 8-OH-DPAT-induced hyperphagia were reversed by simultaneous administration of L-arginine. These results suggest that NO participates in the 8-OH-DPAT-induced hyperphagia which is elicited by activation of the 5-HT1A receptor.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1996

Effects of peripheral 5-HT2 and 5-HT3 receptor agonists on food intake in food-deprived and 2-deoxy-D-glucose-treated rats.

Peripherally administered, the 5-HT2 receptor agonist, alpha-methyl-5-hydroxytryptamine (alpha-methyl-5-HT), significantly suppressed the food intake of food-deprived rats. alpha-Methyl-5-HT also inhibited 2-deoxy-D-glucose-induced hyperphagia in rats. The alpha-methyl-5-HT-induced hypophagia was antagonized by the 5-HT2A receptor antagonist, ketanserin. The alpha-methyl-5-HT-induced decrease in food intake of food-deprived rats was not inhibited by prior adrenodemedullation. The peripheral 5-HT3 receptor agonist, 2-methyl-5-HT, did not affect food intake in food-deprived or 2-deoxy-D-glucose-treated rats. These results suggest that the peripheral 5-HT2A receptor may participate in the regulation of food intake and that its hypophagic effects are not associated with its adrenaline-releasing effects from the adrenal gland. Lastly, the peripheral 5-HT3 receptor did not participate in feeding control.

Adrenal Medulla↗
PubMed1996

Effects of the 5-HT2C/2B receptor agonist 1-(3-chlorophenyl) piperazine on plasma glucose levels of rats.

Acute administration of the 5-HT2C/2B receptor agonist 1-(3-chlorophenyl)piperazine (mCPP, 5-10 mg/kg i.p.) induced hyperglycemia in rats. These changes were diminished in a dose-dependent manner by the 5-HT1/5-HT2 receptor antagonist methysergide and the 5-HT2A/2B/2C receptor antagonist ritanserin. In addition, mCPP-induced hyperglycemia was dose dependently diminished by the ganglionic blocker hexamethonium and was prevented by prior adrenodemedullation. Neither the 5-HT2A receptor antagonist ketanserin nor the 5-HT3/5-HT4 receptor antagonist (3-alpha-tropanyl)-1 H-indole-3-carboxylic acid ester (ICS 205-930) proved effective against mCPP-induced hyperglycemia. Lastly, administration of the 5-HT2A/2C receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)2-aminopropane (DOI) increased plasma glucose levels through ketanserin- and ritanserin-sensitive processes. Our results suggest that hyperglycemia elicited by mCPP is mediated by 5-HT2C and/or 2B receptors, and in turn adrenomedullary catecholamine release, whereas that elicited by DOI involves 5-HT2A receptors.

Amphetamines↗
PubMed1996

Effects of adrenodemedullation and adrenalectomy on the 5-HT2 receptor agonists DOI-and mCPP-induced hypophagia in rats.

Effects of adrenodemedullation and adrenalectomy on the serotonin2 (5-HT2) receptor agonists-induced hypophagia were investigated. Hypophagia induced by both the 5-HT2A/2C, receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and the 5-HT2C-receptor agonist 1-(3-chlorophenyl)piperazine (mCPP) were not affected by adrenodemedullation. In adrenalectomized rats. DOI did not induce hypophagia, while mCPP elicited apparent effects. These results suggest that neither DOI- nor mCPP-induced hypophagia was not associated with adrenaline release from the adrenal medulla. Moreover, our results suggest that DOI-induced hypophagia is involved in corticosterone-sensitive feeding, although other mechanisms which are not related to corticosterone are involved in mCPP-induced anorexia.

Adrenal Medulla↗
PubMed1996

Long-chain acyl-CoA hydrolase from rat brain cytosol: purification, characterization, and immunohistochemical localization.

Long-chain acyl-CoA hydrolase (EC 3.1.2.2), which is found primarily in the brain in rats, catalyzes the hydrolysis of fatty acyl-CoA thioesters. We purified this enzyme, referred to as ACH, from the rat brain cytosol. The molecular masses of the native enzyme and the subunit were estimated to be 104 and 36 kDa, respectively. The enzyme showed high activity with long-chain acyl-CoAs, e.g., with maximal velocity of 262 mumol/min/mg and Km of 5.7 microM for palmitoyl-CoA, but acyl-CoAs with carbon chain lengths of C8-18 were also good substrates. The enzyme was refractory to the inhibitory effect of diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride, but sensitive to p-chloromercuribenzoate. In the rat brain cytosol, about 90% of palmitoyl-CoA hydrolase activity was titrated by anti-ACH antibody, which accounted for over 70% of the enzyme activity found in the brain tissue. Immunoblots of the cytosol prepared from rat brain regional blocks indicated the broad distribution of ACH over the brain, with a relatively high level in the pons and medulla. Immunohistochemically, ACH was localized to neurons. In addition to various nuclei, some neuronal cells, such as mitral cells in the olfactory bulb, pyramidal cells in the cerebral cortex, and Purkinje cells in the cerebellum, were also immunostained with anti-ACH antibody. Brain cytosols prepared from ten mammalian species including human contained a single polypeptide reactive to anti-ACH antibody with molecular masses of 34-36 kDa, together with high activities of palmitoyl-CoA hydrolase. These findings suggest the physiological significance of ACH in the brain, although its precise role remains to be determined.

Animals↗