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T Dohi

Publications and source records attributed to T Dohi.

At least 127 records · Page 7Linked to original sources
PubMed1990

Bis-oxonol experiment on plasma membrane potentials of bovine adrenal chromaffin cells: depolarizing stimuli and their possible interaction.

Changes of plasma membrane potential of isolated bovine adrenal chromaffin cells were monitored by fluorescent probe, bis-[1,3-diethyl-thiobarbiturate]trimethineoxonol (bis-oxonol), which responds to depolarization, resulting in increase of its fluorescence. Excess K+, gramicidin D, veratridine and ouabain all increased bis-oxonol fluorescence. Cells challenged with acetylcholine (ACh) or gamma-aminobutyric acid (GABA) produced a steady-state increase of bis-oxonol fluorescence, reflecting that averaged depolarization occurred continuously. Both effects were dependent on concentration with similar range, and mediated via nicotinic ACh receptor and GABAA receptor, respectively. Application of GABA with ACh or veratridine not only simultaneously but also pretreatedly caused an additive increment of bis-oxonol fluorescence. These results suggest that chromaffin cells in vitro reveal an additively enhanced change of plasma membrane potential in response to the combination of depolarizing stimuli.

Acetylcholine↗
PubMed1990

GABAA receptor-mediated increase of cytosolic Ca2+ in isolated bovine adrenal chromaffin cells.

We have studied the effects of GABA on cytosolic free Ca2+ concentration ([Ca2+]i) as a means of investigating the role of GABA in adrenal catecholamine (CA) secretion. It was demonstrated that GABA caused an elevation of [Ca2+]i via the GABAA receptor in a concentration-dependent manner, which was well correlated with an increase of 45Ca uptake, an increase of CA release and a depolarization of chromaffin cells assessed with bis-oxonol fluorescence. Since the GABA-induced rise of [Ca2+]i was absolutely dependent on the presence of extracellular Ca2+ and partly sensitive to nifedipine, at least one entry route for Ca2+ facilitated by GABA via a voltage-sensitive Ca2+ channel was suggested. When extracellular Cl- was lowered, GABA-induced CA release, depolarization, and rise of [Ca2+]i were all markedly enhanced. It is possible that GABA plays a modulatory role in the regulation of adrenal CA secretion as a facilitatory modulator.

Adrenal Glands↗
PubMed1990

Sialylpentaosylceramide detected with anti-GM2 monoclonal antibody. Structural characterization and complementary expression with GM2 in gastric cancer and normal gastric mucosa.

The ganglioside fraction of human gastric mucosa was analyzed with a newly established anti-GM2 monoclonal antibody KM531. Using this antibody, accumulation of GM2 was observed in all of four cases of gastric carcinoma. In all ganglioside fractions extracted from normal gastric mucosa obtained from eight cases of peptic ulcer GM2 itself was not detected, but three kinds of glycolipid showing slower mobility than GM2 on thin-layer plates were detected by immunostaining with KM531. These glycolipids were assigned as NGM-1, -2, and -3. They were completely lost in all carcinoma tissues and in non-cancerous gastric mucosa from two cases of gastric cancer, and they were also not detected in the ganglioside fraction of small or large intestine. Of these glycolipids, the major one, NGM-1, was isolated from the pooled ganglioside fraction of normal gastric mucosa obtained from cases of peptic ulcer. The structure was determined by proton nuclear magnetic resonance, negative ion fast atom bombardment-mass spectrometry, gas chromatography-mass spectrometry, and treatment with exoglycosidases and mild acid hydrolysis. The structure was GalNAc beta 1----4(NeuAc alpha 2----3) Gal beta 1----4GlcNAc beta 1----3 Gal beta 1----4Glc beta 1----1Cer, which has the same terminal sequence as GM2 but has internal neolacto series structure. This epitope was previously identified as Cad blood group antigen. The decrease of this glycolipid and the increase of GM2 was considered to be a cancer-associated change in gastric mucosa.

Antibodies, Monoclonal↗
PubMed1990

Enhancement by GABA of the stimulation-evoked catecholamine release from cultured bovine adrenal chromaffin cells.

The possible involvement of GABAergic mechanisms in the catecholamine (CA) release from adrenal medulla was investigated in a primary culture of bovine adrenal chromaffin cells. GABA elicited CA release and enhanced acetylcholine (ACh)-, excess K(+)- and veratridine-evoked CA release. Muscimol, a selective GABAA receptor agonist, mimicked the action of GABA on CA release. On the other hand, baclofen, a GABAB receptor agonist, failed to affect basal or evoked CA release. Furthermore, bicuculline and picrotoxin blocked the enhancement by GABA of veratridine-evoked CA release without affecting basal CA release and CA release evoked by veratridine. In Ca2(+)-free medium, GABA failed to affect basal and caffeine-evoked CA release. ACh-evoked CA release was slightly reduced by bicuculline, whereas excess K(+)-evoked CA release was not, suggesting the involvement of endogenous GABA in CA release evoked by ACh. These results suggest a facilitatory modulation by GABA of basal and evoked release of CA from bovine adrenal medulla through GABAA receptor-mediated mechanisms.

Acetylcholine↗
PubMed1990

GABAergic modulation of catecholamine release from cultured bovine adrenal chromaffin cells. Evidence for the involvement of Cl(-)-dependent Ca2+ entry.

The mode by which GABA facilitates the basal and stimulation-evoked catecholamine (CA) release from cultured bovine adrenal chromaffin cells was investigated. Muscimol, a GABAA receptor agonist, facilitated 45Ca uptake in a concentration-related manner. When GABA and acetylcholine (ACh) were simultaneously applied, additive increase in 45Ca uptake was observed. Similar effect on 45Ca uptake was observed in the presence of GABA and veratridine, although 45Ca uptake induced by a rather low concentration of veratridine was more than additively enhanced by GABA. GABA-evoked CA release was also more than additively enhanced by BayK 8644 whereas there was only an additive effect on 45Ca uptake. Substitution of extracellular Cl- by sucrose ("low Cl- medium") during the stimulation with GABA enhanced GABA-evoked CA release. Substitution of extracellular Cl- for more than 1 h abolished GABA-evoked CA release and 45Ca uptake. At this time, the concentration-response curve for veratridine-evoked CA release was shifted to left and GABA no longer enhanced veratridine-evoked CA release at any concentration of veratridine. GABA-induced facilitation of 45Ca uptake in the presence of low concentration of veratridine was also inhibited by long-term treatment with low Cl- medium. These results suggest that the Cl(-)-dependent process linked to GABAA receptor acts on voltage-sensitive Ca2+ channels in chromaffin cells to elicit and modulate CA release.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1990

An enormous shunt between the portal and hepatic veins associated with multiple coronary artery fistulas.

A 9-year-old boy with a rare combination of multiple coronary artery fistulas and congenital shunt between the portal and hepatic veins (portal-systemic shunt) is presented. The most likely pathogenesis for the portal-systemic shunt in this case was persistence of the ductus venosus as a bypass tract of the portal vein. This shunt is considered as one cause of cardiomegaly and dilatation of the hepatic vein in this case, and careful follow-up is mandatory because this shunt could induce portal-systemic encephalopathy. There are a few reports of an anomalous portal venous connection to the hepatic vein as a result of abnormal portal embryogenesis. We experienced a unique case of congenital portal-systemic shunt associated with coronary artery fistulas. The present paper reports angiographic findings in this case and the etiological importance of the congenital portal-systemic shunt.

Cardiomyopathies↗
PubMed1990

Some properties of gingival 12-lipoxygenase activity in human and dog.

Arachidonate lipoxygenase activity in gingival tissue was investigated and compared with that of enzymes from other sources. 12-lipoxygenase activity was detected in homogenates of human and dog gingiva after 2 min incubation with exogenous arachidonic acid. 12-HETE was the major metabolite in both species. The 12-lipoxygenase activity in homogenates of human gingiva and in platelets was inhibited by EDTA; it recovered after the addition of a divalent cation such as Ca2+. Its activity in dog gingiva and platelets was not affected by the chelator. Gingival 12-lipoxygenase, unlike platelet 12-lipoxygenase, was inhibited by AA861, a possible 5-lipoxygenase inhibitor. These findings suggest that gingival tissue has high levels of 12-lipoxygenase activity, but the enzyme in human gingiva differs from that in the dog in its dependency upon divalent cations, and gingival 12-lipoxygenase differs from the same enzyme in platelets in its sensitivity to an inhibitor.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1990

A new approach for the filtrate regeneration system in the wearable artificial kidney.

In the filtrate and/or dialysate regeneration system, which is expected to miniaturize the artificial kidney, ammonium ion decomposed from urea by immobilized urease is removed competitively by ion-exchangers from coexisting cations. Since divalent cations such as Ca2+ and Mg2+ are more favorably exchanged than ammonium ion, this system needs supplementation of these cations and, thus, additional amount of ion-exchanger. To minimize these requirements, we utilized positively charged membrane to process cation-free filtrate in which urea is dialyzed. Positively charged membranes were tested in vitro to evaluate separation efficiency between urea and cations. Equilibrium adsorption of ammonium ion to ion-exchanger with or without co-existing cations demonstrates that this filtrate regeneration system can reduce the amount of ion-exchanger up to one-half to one-third of that of the conventional system. In an ex vivo experiment with a mongrel dog, blood urea nitrogen (BUN) concentration was maintained at the same level or up to 23% less than the initial value.

Aluminum Silicates↗
PubMed1990

Development of computer-aided motion analyzing (CAMA) system for radiopaque implanted tilting disk heart valves.

The newly developed semiautomatic data acquisition and processing system allows progress in quantitative evaluation of functions of implanted tilting disk valves. In the new system, data acquisition could be carried out semiautomatically by utilizing image processing methods, and the data analysis time was shortened. The system consists of a computer-controlled cinefilm loading device, a CCD camera, a frame memory, a superimposer, and CRT displays. Since series of the open- and shut-mode frames are commonly observed by turns in normal subjects, data acquisition was carried out manually at the first frame of each mode and semiautomatically from the second frame to the last. By processing the image data with the binarization method, the valve contours were detected, and an open angle and other motion properties can be obtained. Analyzing 90 frames of the cinefilm, this system analyzes data in a time period 20 min shorter than the manual procedure. With the implanted Medtronic Hall valve, a 60 to 65 degrees open angle was calculated.

Cineradiography↗
PubMed1990

Inhibition of lipoxygenase of rat dental pulp and human platelets by phenolic dental medicaments.

The effects of phenolic dental medicaments on lipoxygenase activities of rat dental pulp and human platelets were studied. The major product derived from [14C] arachidonic acid by the homogenate of rat dental pulp was 12-HETE (15-HETE). Eugenol and p-chlorophenol dose-dependently inhibited HETEs formation. The IC50 values of eugenol and p-chlorophenol were 0.62 and 0.34 mM respectively. The concentrations of these compounds that inhibit lipoxygenase were similar to those required to inhibit cyclooxygenase. These compounds also inhibited 12-lipoxygenase of human platelets with a similar range of concentrations. The results show that phenolic dental medicaments inhibit pulpal and platelet lipoxygenase. Thus, inhibition of arachidonic acid metabolism by phenolic dental medicaments via the lipoxygenase pathway may be involved in the analgesic and anti-inflammatory effects of the medicaments in endodontic therapy.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1989

Immunohistochemical study of carbohydrate antigen expression in gastric carcinoma.

The expression of carbohydrate antigens in malignant and non-malignant gastric mucosa was studied immunohistochemically using the monoclonal antibody AH6 directed to Ley antigen, FH2 directed to Lex antigen, and FH6 directed to sialyl-Lex antigen. Formalin-fixed gastric tissue resected from 54 patients with gastric cancer and 20 patients with gastric ulcer were tested. The incidence of positive cases in gastric cancer patients with each antibody was as follows: AH6;85%, FH2;74%, FH6;74%. The Lex antigen was expressed in 81.5% of cases histologically classified as undifferentiated type, and 66.7% of cases classified as differentiated type. It was expressed in a higher incidence in early stage cancer (93.3%) than in advanced stage cancer (66.7%). Sialyl-Lex antigen was detected in more cases of differentiated type (88.9%) than in those of undifferentiated type (59.3%), whereas none of 8 early cancers of undifferentiated type expressed the antigen. The incidence of the expression of Ley antigen did not differ in relation to histological type or invasiveness. Lex and Ley antigens were detected in noncancerous gastric epithelium. Sialyl-Lex antigen was not detected in the normal fundic gland region. These results demonstrate that Lex antigen may be a differentiation-associated antigen, and sialyl-Lex antigen might be useful as a marker of differentiated cancer and an indication for invasion of undifferentiated cancer.

Adult↗
PubMed1989

[Cytotoxicity of Corylifoliae fructus. I. Isolation of the effective compound and the cytotoxicity].

The ethanol extract of Psoraleae Fructus (Psoralea corylifolia L.) was found to have cytotoxic activity against L929-cells in cell culture. The active compound was isolated by column chromatography on silica gel and identified as bakuchiol by means of spectral evidence. The cytotoxic activity of bakuchiol in cell culture was observed in short time and found to be unreversible. The mechanism of the cytotoxic activity was considered to be due to an injury of cell membrane from electron microscopic observation and hemolytic activity.

Animals↗
PubMed1989

[Cytotoxicity of corylifoliae fructus. II. Cytotoxicity of bakuchiol and the analogues].

Bakuchiol is a major component of Corylifoliae Fructus (Psoralea corylifolia L.) and has been clarified to have cytotoxic activity. The chemical structure-cytotoxic activity relationship of bakuchiol was investigated by means of cytotoxic activity of synthesized analogues of bakuchiol and phenol. It was proved that an alkyl group was necessary for cytotoxic activity. But the double bonds in the unsaturated hydro-carbon group exerted but little influence on the cytotoxic activity. The cytotoxic activity of bakuchiol was the strongest as compared with that of the analogues examined.

Cells, Cultured↗
PubMed1989

The anti-inflammatory effects of phenolic dental medicaments as determined by mouse ear edema assay.

The anti-inflammatory effects of phenolic dental medicaments were evaluated by mouse ear edema assay. p-Chlorophenol (PCP) inhibited edema when applied topically in dosages of 0.2 and 0.5 mg per site at 15 min before or 1.0 and 2.0 mg per site at 60 min after the application of croton oil. The inhibitory effects were also noted with eugenol, guaiacol, o-cresol, phenol and orally administered indomethacin (10 mg/kg). The involvement of the effects on prostaglandin biosynthesis in the anti-inflammatory effects of these compounds is discussed.

Animals↗
PubMed1989

Coarctation restenosis after isthmosubclavioplasty. A consideration on operative procedure and intraluminal balloon angioplasty.

We describe a case of a six-month-old boy in whom an aortic coarctation restenosis had developed three months after isthmosubclavioplasty. The restenosis was successfully relieved by means of intraluminal balloon angioplasty. At the isthmosubclavioplasty operation, extensive mobilization of the aorta to facilitate the anastomosis should be avoided. From anatomic and operative viewpoints, coarctation restenosis after the isthmosubclavioplasty operation was considered to be amenable to the intraluminal balloon angioplasty.

Angioplasty, Balloon↗
PubMed1988

An IgG3 monoclonal antibody established after immunization with GM3 lactone: immunochemical specificity and inhibition of melanoma cell growth in vitro and in vivo.

In previous studies, an IgM monoclonal antibody (M2590), established after immunization of C57BL/6 mice with syngeneic B16 melanoma cells, was found to react with melanoma cells, but not with various normal cells and tissues (Taniguchi, M., and Wakabayashi, S., Jpn. J. Cancer Res., 75:418-426, 1984). The structure defined by this antibody was identified as GM3 (Hirabayashi, Y., et al., J. Biol. Chem., 260:13328-13333, 1985) organized in membranes at high density, although the real immunogen was suggested to be GM3 lactone (Nores, G. A., et al., J. Immunol., 139:3171-3176, 1987). Since GM3 lactone was found to be highly immunogenic, we subsequently immunized C57BL/6 mice with GM3 lactone coated on Salmonella minnesotae and established hybridoma DH2, secreting an IgG3 antibody showing preferential reactivity with GM3 lactone over GM3 under certain conditions. The reactivity of the DH2 antibody was competitively inhibited by M2590, and it showed a preferential reactivity with melanoma cells and displayed various immunochemical and immunobiological properties similar to those of M2590. However, DH2 antibody inhibited melanoma cell growth in vivo, induced antibody-dependent cytotoxicity in vitro, and showed a preferential accumulation in melanoma growth in vivo. These properties are characteristic of the IgG3 subclass, in striking contrast to IgM antibody M2590, which does not inhibit cell growth in vivo or in vitro and does not induce antibody-dependent cytotoxicity. Thus, immunization with lactone forms of tumor-associated ganglioside antigens might be useful in the production of antibodies and prevention of tumor cell growth in vivo (antitumor vaccines).

Animals↗
PubMed1988

A novel ganglioside, de-N-acetyl-GM3 (II3NeuNH2LacCer), acting as a strong promoter for epidermal growth factor receptor kinase and as a stimulator for cell growth.

A novel ganglioside, de-N-acetyl-GM3 (neuraminyllactosylceramide, II3NeuNH2LacCer), was found in the monosialoganglioside fraction of A431 cells and B16 melanoma cells by high-performance liquid chromatography, thin-layer chromatography, and immunoblotting with its specific monoclonal antibody DH5. This novel type of membrane ganglioside strongly enhanced the kinase activity associated with the epidermal growth factor (EGF) receptor, and it showed 32, 35, and 12% growth stimulation as compared with control cultures of A431, Swiss 3T3, and B16 melanoma cells, respectively. Exogenously added de-N-acetyl-GM3 did not alter the affinity of EGF binding to its receptor. These properties of de-N-acetyl-GM3 are in striking contrast to those of GM3 and its lyso derivative (lyso-GM3) which were previously shown to inhibit EGF receptor kinase activity and to inhibit growth in the same cells. These data indicate that de-N-acetylation at the sialic acid moiety of GM3 ganglioside is an important mechanism for modulation of EGF-dependent cell growth. The mechanism is antagonistic to that of GM3-dependent modulation of receptor function.

Animals↗