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Biomedical subjects

N Inagaki

Publications and source records attributed to N Inagaki.

At least 19 recordsLinked to original sources
PubMed1992

Leukotriene receptors in the skin of rats differ from those of mouse skin or rat stomach strip.

To compare the receptors for cysteinyl-leukotriene (cys-LT) in rat skin with those in other tissues, we investigated the effects of specific cys-LT receptor antagonists (FPL 55712, LY171883, MCI-826 and L-648051) on cys-LT-induced cutaneous reactions in rats and mice, and on cys-LT-induced contractile responses in rat stomach smooth muscle. We also studied the effects of these drugs on homologous passive cutaneous anaphylaxis. The four cys-LT receptor antagonists dose dependently inhibited cys-LT-induced cutaneous reactions in mouse ear, but failed to inhibit passive cutaneous anaphylaxis and the histamine-induced cutaneous reaction. In rats, only MCI-826 inhibited cys-LT-induced cutaneous reactions although the other three drugs failed to inhibit these reactions. In contrast, the cys-LT-induced contractile responses of rat stomach smooth muscle were inhibited by all these drugs in a concentration-dependent manner. These results suggest that cys-LT receptors in rat skin have an affinity different from that of receptors in mouse skin and rat stomach. They also suggest that cys-LTs are not involved in passive cutaneous anaphylaxis in mice and rats.

Acetophenones↗
PubMed1992

Distribution of the glucose transporters in human brain tumors.

In the present study, we have investigated the expression of both the erythrocyte-type (GLUT1) and the brain-type (GLUT3) glucose transporter isoforms in primary human brain tumors. In situ hybridization made it possible to localize and semiquantify both GLUT1 and GLUT3 mRNAs of individual cells in all 18 samples examined. More signals for GLUT3 mRNA than for GLUT1 mRNA were found over astrocytoma cells, while the reverse was the case in all 6 meningiomas. In astrocytomas, for both mRNAs, the density of silver grains over tumor cells was well correlated with the malignancy of the cells. This correlation was, as was also confirmed by Northern blot analysis, more marked with GLUT3 mRNA than with GLUT1 mRNA. In 2 of 5 anaplastic astrocytomas and in all 3 glioblastomas, numerous tumor cells with large amounts of both mRNAs tended to surround the perivascular regions. "Tumor vessels" with endothelial proliferation, an almost pathognomonic feature of glioblastomas, expressed much GLUT3 mRNA but no significant GLUT1 mRNA, while a single- or a few-layered capillary endothelium expressed much GLUT1 mRNA. The distribution of both mRNAs was in good accordance with that of both proteins. Our results suggest that the expression of both glucose transporter isoforms may contribute to the maintenance of human brain tumors and that the expression of the GLUT3 isoform may be closely related to the malignant change of astrocytomas and particularly related to the aberrant neovascularization which accompanies glioblastomas.

Astrocytoma↗
PubMed1992

Tyrosine phosphorylation is required for mast cell activation by Fc epsilon RI cross-linking.

We investigated the possible role of tyrosine phosphorylation in the activation process of mast cells by cross-linking of cell-bound IgE antibodies. Bone marrow-derived mouse mast cells (BMMC) were sensitized with mouse IgE antiDNP mAb and then challenged with multivalent Ag DNP conjugates of human serum albumin. Analysis of phosphotyrosine-containing proteins in their lysates by SDS-PAGE and immunoblotting revealed that cross-linking of cell-bound IgE antibodies induced a marked increase in tyrosine phosphorylation of several proteins. To obtain direct evidence for activation of protein-tyrosine kinases (PTK), phosphotyrosine-containing proteins in lysates of mast cells were affinity purified, and kinase activity of the immunoprecipitates was assessed by an in vitro kinase assay. The results clearly showed activation of PTK upon cross-linking of Fc epsilon RI. Activation of PTK was not detected by the same assay when the sensitized BMMC were challenged with monovalent DNP-lysine. Treatment of sensitized BMMC with either Ca2+ ionophore or PMA failed to induce the activation of PTK. A representative IgE-independent secretagogue, thrombin, induced histamine release from BMMC but failed to induce activation of PTK. The results excluded the possibility that PTK activation is the consequence of an increase in intracellular Ca2+ or activation of protein kinase C. Addition of genistein, a PTK inhibitor, to sensitized BMMC before Ag challenge inhibited not only Ag-induced PTK activation, but also inositol 1,4,5-trisphosphate production, and histamine release in a similar dose-response relationship. Other PTK inhibitors, such as lavendustin A and tyrphostin RG50864, also inhibited the Ag-induced activation of PTK and histamine release. The results collectively suggest that activation of PTK is an early event upstream of the activation of phospholipase C, and is involved in transduction of IgE-dependent triggering signals to mediator release.

Animals↗
PubMed1992

Accumulation of a translation intermediate of D1 protein by light-dark transition in isolated spinach chloroplasts.

In an in vitro translation experiment using spinach chloroplasts, a novel protein band of about 17.5 kDa appeared by light to dark transition. The protein never accumulated in detectable amounts either in continuous illumination or in continuous darkness. The 17.5 kDa protein accumulated upon light-dark transition, on the other hand, disappeared by the subsequent illumination. Accumulation of the protein in light, however, was observed when stromal level of ATP in chloroplasts was lowered after preillumination by the addition of various chemical compounds which, irrespective of the mode of action, eventually decrease the ATP level, e.g. atrazine, carbonyl-cyanide-m-chlorophenyl hydrazone and glycerate. The dark-accumulated protein was concluded to be a translation intermediate of D1 protein based on the facts that this component precipitates with specific antibodies and is resistant to lysylendopeptidase treatment. The suppression by chloramphenicol of both appearance upon light-dark transition and disappearance by the subsequent illumination of the protein also supported this conclusion. The phenomenon was discussed in terms of pausing in the translation of psbA mRNA.

Chloramphenicol↗
PubMed1992

c-Jun represses the human insulin promoter activity that depends on multiple cAMP response elements.

Glucose is known to increase the cAMP concentration in pancreatic beta cells. To determine the mechanism by which cAMP augments insulin gene expression, we first identified the cAMP response elements (CREs) of the human insulin gene. In DNase I footprint analysis, the bacterially synthesized CRE-binding protein, CRE-BP1, protected four sites: two sites in the region upstream from the insulin core promoter, one site in the first exon, and one site in the first intron. To examine the roles of those four sites, we constructed a series of DNA plasmids in which the wild-type and mutant insulin promoters were linked to the chloramphenicol acetyl-transferase gene. Studies of the transcriptional activity of these plasmids after transfection into hamster insulinoma (HIT) cells showed that these four sites contributed additively to the cAMP inducibility of the insulin promoter. Surprisingly, the c-jun protooncogene product (c-Jun) repressed the cAMP-induced activity of the insulin promoter in a cotransfection assay with the c-Jun expression plasmid. Northern blot analysis demonstrated that the level of c-jun mRNA was dramatically increased by glucose deprivation in HIT cells. These results suggest that glucose may regulate expression of the human insulin gene through multiple CREs and c-Jun.

Animals↗
PubMed1992

Regional distribution of histamine in the brain of non-mammalian vertebrates.

The histamine contents in the brains of various species of non-mammalian vertebrates were determined by an HPLC-fluorometric method. The whole brain contents of histamine in birds (200-500 pmoles/g) were comparable to those in mammals, but were higher in reptiles (1000-13500 pmoles/g) and amphibia (1600-2200 pmoles/g) and lower in teleosts (10-50 pmoles/g). In all species, histamine was unevenly distributed, being present at highest concentrations in the diencephalon, except in teleosts, in which its content was highest in the telencephalon. The brain histamine contents were proportional to the reported densities of histamine-immunoreactive fibers.

Animals↗
PubMed1992

Type-1 and type-2 astrocytes are distinct targets for prostaglandins D2, E2, and F2 alpha.

Accumulating evidence has revealed that astrocytes are potential targets for various neurotransmitters. Here we investigated the effects of prostaglandins (PGs) on signal transduction in purified primary cultures of rat type-1 and type-2 astrocytes. PGF2 alpha, PGD2, and 9 alpha,11 beta-PGF2, a metabolite of PGD2 and a stereoisomer of PGF2 alpha, evoked a rapid rise in the intracellular Ca2+ concentration ([Ca2+]i) in type-1, but not in type-2, astrocytes. STA2, a stable analogue of thromboxane A2, was less effective, and PGE2 showed little effect. The PG-induced rise in [Ca2+]i was not blocked by an antagonist of either PGD2 receptor or thromboxane A2 receptor. PGF2 alpha and 9 alpha,11 beta-PGF2 stimulated rapid formation of inositol trisphosphate followed by inositol bisphosphate and inositol monophosphate. On the other hand, PGE2 increased the intracellular level of cyclic AMP in type-2 astrocytes, rather than in type-1 astrocytes. The potency of PGs for cyclic AMP formation was in the following order: PGE2 greater than PGE1 greater than or equal to STA2 much greater than iloprost, a stable analogue of PGI2. PGD2 and PGF2 alpha had no effect on cyclic AMP formation. These results demonstrate that type-1 astrocytes preferentially express PGF2 alpha receptors, the activation of which leads to phosphoinositide metabolism and [Ca2+]i elevation, whereas type-2 astrocytes possess PGE receptors that are linked to cyclic AMP formation.

Animals↗
PubMed1992

The effect of prednisolone on substance P-induced vascular permeability in mice.

The effect of prednisolone on the substance P (SP)-induced vascular permeability increase in male ddY, WBB6 F1(-)+/+ (control) and WBB6 F1-W/WV (no mast cell in skin or internal organs) mice was investigated. 1) SP (1-10,000 pg/site) increased vascular permeability in ddY, WBB6 F1(-)+/+ and WBB6 F1-W/WV mice ears. 2) SP (100 pg/site)-induced vascular permeability was inhibited by prednisolone (10 mg/kg) administered intraperitoneally 3 to 12 hours prior to the elicitation of the reaction in ddY mice. When dexamethasone at a dose of 1 mg/kg was administered intraperitoneally 2 to 24 hours prior to the elicitation of the reaction, significant inhibition was observed. When prednisolone was administered intraperitoneally 8 hours prior to the elicitation of the reaction, the SP-induced capillary permeability increase in both ddY and WBB6 F1-W/WV mice was clearly inhibited by the drug at doses of 5 and 10 mg/kg. 3) Diphenhydramine (1 and 10 mg/kg) inhibited SP-induced vascular reaction in ddY mice but not in WBB6 F1-W/WV mice. 4) Atropine (10 mg/kg) inhibited SP-induced vascular reaction in both ddY and WBB6 F1-W/WV mice. But acetylcholine did not cause an increase of vascular permeability in ddY and WBB6 F1-W/WV mice ears. 5) Prednisolone (5 mg/kg) inhibited histamine- and serotonin-induced vascular permeability in ddY and WBB6 F1-W/WV mice ears. 6) Prednisolone (5 and 10 mg/kg) inhibited the SP-induced histamine release from ddY mice peritoneal mast cells. These results suggest that the vascular effect of SP is mediated by both mast cell dependent (release of histamine from mast cells) and mast cell independent mechanisms. Prednisolone inhibits the SP-induced vascular permeability mediated by both mechanisms in mice.

Animals↗
PubMed1992

Antiallergic mechanisms of beta-adrenergic stimulants in rats.

Antiallergic mechanisms of beta-adrenergic stimulants were investigated in rats. Isoproterenol administered intravenously inhibited IgE antibody-mediated homologous passive cutaneous anaphylaxis (PCA) and histamine-induced cutaneous reaction (HCR) elicited at the same time in the same rats significantly. The inhibition of PCA was more potent than that of HCR, suggesting that PCA is inhibited by at least 2 mechanisms. One is the inhibition of vascular permeability increase. In vivo histamine release in the rat peritoneal cavity caused by intravenous antigen was inhibited by the intravenous administration of isoproterenol or salbutamol dose-dependently. On the contrary, when the histamine release in the peritoneal cavity was caused by intraperitoneal antigen, isoproterenol or salbutamol administered simultaneously with antigen failed to inhibit the reaction. Furthermore, antigen-induced histamine release from sensitized peritoneal exudate cells in vitro was not inhibited by isoproterenol or salbutamol. These results indicate that the primary target of beta-adrenergic stimulants is the vascular endothelium, and that the direct inhibition of chemical mediator release from mast cells does not play an important role for the inhibition of PCA and in vivo histamine release in the peritoneal cavity in rats. Beta-adrenergic stimulants therefore may prevent intravenously administered antigen from activating sensitized mast cells through affecting endothelial cells.

Albuterol↗
PubMed1992

Circadian rhythm of histamine release from the hypothalamus of freely moving rats.

Using an in vivo microdialysis technique coupled with HPLC-fluorometry, the release of neuronal histamine from the anterior hypothalamic area was monitored continuously in conscious, freely moving rats under a 12:12 h light:dark cycle. Spontaneous locomotor activity of the rats was measured simultaneously using a locomotor activity counter. Histamine release gradually increased in the second half of the light period (1400-2000) and the average histamine release during the dark period (2000-0800, 0.20 +/- 0.02 pmol/30 min) was significantly higher than that during the light period (0.12 +/- 0.01 pmol/30 min). This clear circadian change in the release suggests that the central histaminergic system is related to the circadian rhythm of rats.

Animals↗
PubMed1992

Studies on the anti-allergic mechanism of glucocorticoids in mice.

Glucocorticoids inhibit IgE antibody-mediated passive cutaneous anaphylaxis (PCA) and chemical mediator-induced cutaneous reactions elicited in the mouse ear. In the present study, we investigated the effect of actinomycin D, a protein synthesis inhibitor, on dexamethasone-caused inhibition of PCA and histamine-induced cutaneous reaction in the mouse ear. Tyrosine aminotransferase (TAT) activity in the liver, which was estimated as an index for protein synthesis, significantly increased by the administration of hydrocortisone, prednisolone and dexamethasone. Significant increase in TAT activity was observed from 2 h after glucocorticoid administration and peaked at 4 h, and declined gradually thereafter. Cycloheximide even at high doses of 100 and 300 mg/kg failed to affect the increase in TAT activity by dexamethasone. On the contrary, actinomycin D at doses of 1 and 10 mg/kg abrogated the TAT activity increase by dexamethasone almost completely. Treatment with 1 mg/kg of actinomycin D, however, failed to affect the inhibition of PCA and histamine-induced cutaneous reaction by dexamethasone. These results suggest that glucocorticoids exhibit their inhibitory action of PCA and chemical mediator-induced cutaneous reactions in mice through a mechanism resistant to actinomycin D treatment.

Animals↗
PubMed1992

Active cutaneous anaphylaxis (ACA) in the mouse ear.

Active cutaneous anaphylaxis (ACA) was studied in the ear of female BALB/c mice. Mice were immunized with ovalbumin in the presence of aluminium hydroxide gel or complete Freund's adjuvant (CFA). Two weeks after the immunization, ACA was elicited in the mouse ear by injecting 10 microliters of antigen solution intradermally into the ear lobe. ACA was assessed by the amount of extravasated dye, which was given intravenously just after the antigen injection. Antiallergic drugs (tranilast, ketotifen and azelastine), antihistamines (chlorpheniramine, diphenhydramine and mequitazine), beta-stimulants (isoproterenol and salbutamol), theophylline and glucocorticoids (hydrocortisone, prednisolone and dexamethasone) inhibited the reaction significantly. These drugs inhibited both ACA in mice immunized with alum-precipitated antigen and ACA in mice injected with CFA-emulsified antigen similarly. ACA in the mouse ear might be a useful tool for studying drugs for allergy.

Animals↗
PubMed1992

Mechanisms for glucocorticoid inhibition of immediate hypersensitivity reactions in rats.

The inhibitory mechanisms of immediate hypersensitivity reactions by glucocorticoid (GC) were studied in rats. Homologous passive cutaneous anaphylaxis (PCA) mediated by IgE antibodies and cutaneous reactions caused by histamine, serotonin and leukotriene C4 were elicited at the same time in the same rats. Three kinds of GC, hydrocortisone, prednisolone and dexamethasone, inhibited all these reactions significantly. Although mediator-induced cutaneous reactions were inhibited transiently around 2 hours after GC administration, inhibition of PCA was more potent and lasted longer. A time lag seemed to be essential for both inhibitions. IgE antibody-mediated histamine release in vivo in the rat peritoneal cavity was also inhibited by GC administration significantly, and the inhibition was long lasting when compared to those of the mediator-induced cutaneous reactions. Tyrosine amino-transferase (TAT) activity in the rat liver increased significantly by GC administration, and the increased TAT activity was completely abrogated by simultaneous administration of 5 mg/kg of cycloheximide (CH). In the same experimental condition, although inhibition of histamine-induced cutaneous reaction by GC was completely abrogated, the inhibition of PCA elicited at the same time in the same rats was only partially attenuated. Furthermore, the same dose of CH little affected the dexamethasone inhibition of histamine release in the rat peritoneal cavity, although the increase of TAT activity in the liver of the same rats was completely abrogated. These results demonstrate that PCA is inhibited by GC through at least 2 mechanisms, inhibition of mediator release from mast cells and non-specific inhibition of vascular permeability increase caused by released mediators. Although the latter action of GC is dependent upon protein synthesis, the former seems to be mediated by a unique mechanism independent of protein synthesis.

Animals↗
PubMed1992

Expression of GLUT1 and GLUT2 glucose transporter isoforms in rat islets of Langerhans and their regulation by glucose.

Previous studies revealed that rat islets express the GLUT2-liver facilitative glucose transporter isoform, a glucose carrier with a low affinity for glucose but a high capacity for glucose transport. These studies indicated the presence of a second glucose transporter in rat islets; however, they did not indicate to which of the five known facilitative glucose transporters it corresponded. In this study, we isolated RNA from rat islets of Langerhans and confirmed the presence of GLUT2 mRNA. In addition, we present data indicating that the second isoform expressed in islets is the GLUT1-erythrocyte isoform. The effect of culturing islets in 5.5, 8.3, or 11.1 mM glucose on the levels of GLUT1 and GLUT2 mRNA also was examined. The levels of GLUT1 and GLUT2 mRNA were two- and threefold higher, respectively, in islets cultured for 24 h in 11.1 mM glucose compared with those incubated in the presence of 5.5 mM glucose. Therefore, the previously observed increase in GLUT2 mRNA levels in the islets of rats made hyperglycemic by chronic infusion of glucose can be mimicked in vitro, implying that glucose regulates GLUT2 mRNA expression.

Animals↗
PubMed1992

Glucose as regulator of glucose transport activity and glucose-transporter mRNA in hamster beta-cell line.

To investigate the role of glucose in regulating glucose transporters in pancreatic beta-cells, we studied the hamster clonal beta-cell line HIT-T15, which retains responsiveness to glucose. Northern blot analysis demonstrates that GLUT2 and GLUT1 mRNA are abundant in HIT cells. After a 24-h culture with various concentrations of glucose (0-22.2 mM [0-400 mg/dl]), the GLUT2 mRNA level in HIT cells increased by 40% at 22.2 mM (400 mg/dl) glucose compared with 11.1 mM (200 mg/dl) without a change in mRNA stability. It also decreased proportionally to the reduction of glucose concentration. Glucose deprivation resulted in a decrease of GLUT2 mRNA to an almost undetectable level, with a marked increase in the degradation rate of mRNA. In contrast, the GLUT1 mRNA was not affected by glucose. We show that glucose uptake is highest in HIT cells incubated at 2.8-5.5 mM (50-99 mg/dl) glucose for 24 h, and that levels in cells cultured at 0 mM (0 mg/dl) and 22.2 mM (400 mg/dl) glucose decrease to approximately 20% of the maximum level. This decrease is consistent with the effects of glucose on glucose-stimulated insulin secretion in HIT cells. Our results indicate that glucose is involved in regulating GLUT2 mRNA and glucose uptake activity and that the glucose responsiveness of the insulin secretion correlates with the glucose-induced change in glucose uptake activity in HIT cells.

Animals↗
PubMed1991

Histamine-induced cyclic AMP accumulation in type-1 and type-2 astrocytes in primary culture.

Histamine-induced cyclic AMP (cAMP) accumulation was studied in purified primary cultures of type-1 and type-2 astrocytes from neonatal rat brain. Histamine induced remarkable cAMP accumulation in type-1 astrocytes in a dose-dependent manner (EC50 = 1.2 x 10(-5) M, Emax = 1100% of control). In contrast, histamine had no significant effect on cAMP accumulation in type-2 astrocytes. Famotidine, an H2-antagonist, dose-dependently inhibited histamine-induced cAMP accumulation in type-1 astrocytes (Ki = 3 x 10(-8) M), but mepyramine (10(-6) M), an H1-antagonist, had no effect. Dimaprit and impromidine, H2-agonists, stimulated cAMP accumulation, but 2-pyridylethylamine, an H1-agonist, did not stimulate it nor augment the H2-agonist-induced cAMP accumulation. These results indicate that (1) histamine induces cAMP accumulation in type-1 astrocytes but not in type-2 astrocytes, and that (2) histamine-induced cAMP accumulation in type-1 astrocytes is mediated by H2-receptors without significant augmentation via H1-receptors.

Animals↗
PubMed1991

Arachidonic acid metabolism during antigen and ionophore activation of the mouse bone marrow derived mast cell.

This study has examined the metabolism of arachidonic acid in the mouse bone marrow-derived mast cell (BMMC) during immunologic and nonimmunologic activation. The predominant pools of endogenous arachidonate in the mast cells were found in ethanolamine (46%), choline (39%) and inositol (14%) containing glycerolipids. Initial studies established conditions where equilibrium labelling of these major phospholipids in the BMMC could be reached. Upon challenge, arachidonate was lost from all major phospholipid classes (phosphatidylethanolamine greater than phosphatidylcholine greater than phosphatidylinositol). There was a small but significant increase in the amount of label associated with phosphatidic acid during cell activation. Arachidonate was distributed among 1-acyl, 1-alkyl and 1-alk-1-enyl-linked subclasses of PC and PE. The rank order of loss of labelled arachidonate from the major PE and PC subclasses during antigen and ionophore activation was 1-alk-enyl-2-arachidonoyl-GPE greater than 1-acyl-2-arachidonoyl-GPC greater than 1-acyl-2-arachidonoyl-GPE greater than 1-alkyl-2-arachidonoyl-GPC. Labelled products released into the supernatant fluids and free arachidonic acid within the cell accounted for the bulk of arachidonate lost from phospholipids. Labelled products in the supernatant fluids were composed of LTB4, LTC4, PGD2 and free arachidonic acid. BMMC phospholipids were also labelled for 24 hr with [3H]choline, [3H]myoinositol or [14H]ethanolamine and labelled 2-lyso phospholipids were measured after cell activation. Radioactivity in lysophospholipids from PC, PE and PI increased significantly between 30 s and 2 min after antigen activation and then declined. Taken together, these studies suggest that arachidonate is mobilized predominantly from PE and in particular 1-alk-1-enyl-2-arachidonoyl-GPE by the direct removal of arachidonate from the sn-2 position of the molecule. Most of this arachidonate is then released from cells as eicosanoids or free fatty acid.

Animals↗