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Biomedical subjects

T Osugi

Publications and source records attributed to T Osugi.

At least 37 records · Page 2Linked to original sources
PubMed1986

Bradykinin-induced intracellular Ca2+ elevation in neuroblastoma X glioma hybrid NG108-15 cells; relationship to the action of inositol phospholipids metabolites.

The effect of bradykinin on the intracellular Ca2+ concentration ([Ca2+]i) in NG108-15 cells was studied using a Ca2+ indicator quin 2. Bradykinin induced two phases of change in [Ca2+]i. Bradykinin induced a spike phase of [Ca2+]i increase which was detectable within 15 s and decayed to near-basal concentration in 3 min and then a prolonged plateau phase of [Ca2+]i increase which continued for 15 min. The bradykinin-induced spike phase was not diminished by decreasing extracellular Ca2+ concentration ([Ca2+]o) to 1 microM. On the contrary, the plateau phase was dependent on [Ca2+]o and inhibited by Ca2+ blockers, verapamil (50 microM), nifedipine (1 microM). The iontophoretic injection of inositol-trisphosphate (IP3) into the single cell induced the increase of [Ca2+]i, which was independent of [Ca2+]o. These results indicate that the bradykinin-induced spike phase is mediated by the release of intracellular Ca2+ stores induced by IP3, while the plateau phase is mediated by influx of extracellular Ca2+ probably through voltage-sensitive Ca2+ channels.

Animals↗
PubMed1986

1-Oleoyl-2-acetyl-glycerol and phorbol diester stimulate Ca2+ influx through Ca2+ channels in neuroblastoma x glioma hybrid NG108-15 cells.

The effect of 1-oleoyl-2-acetyl-glycerol (OAG) and the phorbol diester 12-O-tetradecanoyl-phorbol-acetate (TPA) on the intracellular Ca2+ concentration ([Ca2+]i) in NG108-15 cells was studied using a Ca2+ indicator, quin 2. OAG and TPA induced an increase in [Ca2+]i from 100 +/- 19 to 187 +/- 24 nM and 192 +/- 15 nM, respectively, within 15 min. The increase in [Ca2+]i induced by activators of protein kinase C was dependent on the extracellular Ca2+ concentration [Ca2+]o) and was inhibited by the Ca2+ blockers, verapamil and nifedipine. These results indicate that the OAG- and TPA-induced [Ca2+]i increase is mediated by the influx of extracellular Ca2+ through voltage-sensitive Ca2+ channels.

Calcium↗
PubMed1985

Multiple agonist binding sites of muscarinic acetylcholine receptors and their relation to the negative inotropic action of agonists in guinea-pig heart.

The Kd values of the multiple agonist binding sites in cardiac muscarinic receptors (mAChR) and pD2 values for negative inotropic actions were determined independently and their relation was examined. The guinea-pig cardiac mAChR is known to have three agonist binding sites (super-high (SH), high (H) and low (L) affinity agonist binding sites) for carbachol (CCh). Pilocarpine (Pilo) and oxotremorine (Oxo) distinguished two sites (higher (Ho/p) with pKd of 5.88 and 8.20, respectively, and lower (Lo/p) affinity agonist binding sites with pKd of 5.08 and 6.17, respectively). The effects of guanine nucleotide and sulfhydryl reagent indicated that the Ho/p site corresponded with the SH site for carbachol, and the Lo/p site with the H + L sites for carbachol. The pD2 values of CCh, Pilo and Oxo for negative inotropic actions on autocontraction of right atria were 5.38, 5.30 and 6.80, respectively. The pD2 values of CCh and Oxo on electrically stimulated contraction of left atria in the presence of isoproterenol were 5.80 and 6.46, respectively, thus being closely related to H or Lo/p agonist binding sites of mAChR.

Animals↗
PubMed1984

Differences in Ca2+ mobilization induced by alpha-adrenergic agonist and phosphatidic acid in cultured hepatocytes.

In an attempt to elucidate the relationship between phosphatidylinositol breakdown and alpha-adrenergic responses, effects of phosphatidic acid and phosphatidylinositol related metabolites on Ca2+ mobilization and glucose output in cultured hepatocytes were examined. Norepinephrine induced the net 45Ca2+ efflux from preloaded cells and stimulated glucose output via alpha-adrenergic receptor stimulation, whereas phosphatidic acid caused 45Ca2+ uptake to cells and did not stimulate glucose output. Myo-inositol-monophosphate, diglyceride and arachidonic acid, which are released by phosphatidylinositol breakdown, had no effect on 45Ca2+ efflux and glucose output in cells. These results suggest that phosphatidic acid and phosphatidylinositol related metabolites can not mimic the alpha-adrenergic actions in cultured hepatocytes.

Animals↗
PubMed1984

Effects of guanine nucleotide and sulfhydryl reagent on subpopulations of muscarinic acetylcholine receptors in mammalian hearts: possible evidence for interconversion of super-high and low affinity agonist binding sites.

Multiple site models of muscarinic acetylcholine receptors (mAChR) for agonist binding were applied to curves for the inhibition of QNB binding by carbachol by using nonlinear least square regression analysis. The effects of a guanine nucleotide guanyl-5'-yl imidodiphosphate (Gpp(NH)p) and a sulfhydryl reagent 5,5'-dithiobis(2-nitrobenzoic acid (DTNB) on the curves were also analyzed. The results suggested that mAChR of dog and guinea pig heart had three types of sites with different affinities for carbachol (super-high (SH), high (H) and low (L]. In the presence of Gpp(NH)p, SH sites were eliminated and L sites increased, indicating conversion of SH sites to L sites. On the contrary, in the presence of DTNB, L sites were converted to SH sites. These results were obtained at both 37 degrees C and 0 degrees C incubation although the affinity of each site was high at 0 degrees C than at 37 degrees C. These data suggest the interconversion of SH and L sites. The possible existence of two subtypes (GTP-regulated mAChR(SH-L type) and GTP-independent mAChR (H type] is discussed.

Animals↗
PubMed1982

Japanese summer-type hypersensitivity pneumonitis: studies using Cryptococcus antigen.

Sixty-six patients, diagnosed as Japanese summer-type hypersensitivity pneumonitis at Osaka Prefectural Habikino hospital between 1973 and 1980, were studied. The diagnosis was based on the clinical features and summer-seasonal nature of the disease. The presence of an aetiological agent within patients' home environment was suggested by the recurrence of acute symptoms of high fever, cough and dyspnoea 5-8 hr after coming home from hospital, and by spontaneous improvement on leaving home. Immunological studies revealed the presence of anti-Cryptococcus antibody in sixty-four of sixty-five patients' sera, by indirect immunofluorescence against Cryptococcus neoformans. Precipitating antibody against culture supernatant protein-antigen of Cr. neoformans was detected in more than 80% of sera obtained from patients during the active stage of the disease. The positive result on inhalation provocation-challenge, using culture supernatant protein-antigen, suggested that Cr. neoformans or antigenically related Cryptococcus species may cause Japanese summer-type hypersensitivity pneumonitis.

Adolescent↗
PubMed1981

Potassium stimulated 45Ca uptake by cortical slices of rat brain: effects of cyclic nucleotide derivatives.

The effects of dibutyryl cyclic GMP (db-cGMP) and dibutyryl cyclic AMP (db-cAMP) on potassium-stimulated 45Ca uptake by cortical slices of rat brain were investigated. db-cGMP specifically inhibited the initial rate of potassium-stimulated 45Ca uptake in a dose-dependent manner. Our findings supported the suggestion that cyclic GMP may play a regulatory role in depolarization-elicited Ca2+ influx in nerve endings in situ.

Animals↗
PubMed1981

[The fine structure of endothelial cells in meningiomas (author's transl)].

The fine structure of the endothelial cells in meningiomas was studied by the electron microscopy. There were an increased number of pinocytotic vesicles and fenestrations especially at the attenuated portion of the endothelial cells. Intraluminal infoldings of the plasma membrane were frequently found. Those were certainly abnormal and all probably related to the increased vascular permeability of the endothelial cells. Usually large number of tubular bodies and associated tubule-containing vacuoles were found. The constituent tubules seemed identical but the various bodies differed in terms of their size, matrix, and the packing of the tubules within them. The significance of those structures is unknown.

Brain↗
PubMed1977

[Fibrinolytic activity of cerebrospinal fluid in subarachnoid hemorrhage (author's transl)].

This study was aimed to investigate the correlation between recurrent hemorrhage of ruptured intracranial aneurysm and local fibrinolytic activity of aneurysmal fibrin plug. The fibrinolytic activity of cerebrospinal fluid (CSF) was investigated in 63 patients with various neurological diseases by means of modified fibrin plate method. No plasmin was elicited in normal CSF, however, it was confirmed that CSF contained an incomplete activator which became a complete activator inthe presence of streptokinase, and plasminogen was identified in the presence of urokinase. In 26 cases of subarachnoid hemorrhage, the fibrinolytic activity of CSF occurred in the patients within two weeks following hemorrhagic ictus. In almost cases, the fibrinolytic activity of CSF was not increased in the first three weeks after the onset of hemorrhage. This result agreed with the fact that rebleeding of intracranial aneurysm tended to occur within two weeks after the hemorrhage. Therefore, intensive antifibrinolytic therapy for two weeks after onset of hemorrhage is necessary in order to prevent recurrent hemorrhage of intracranial aneurysm, and its doses should be sufficient to inhibit local fibinolysis. It has been suggested that the local fibrinolysis after subarachnoid hemorrhage would be caused by activators released from damaged surrounding brain tissues. Furthermore, it is strongly suggested from the result of our in vitro experiments that coexistence of CSF and blood play an important role to increase local fibrinolysis.

Fibrinolysis↗