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Biomedical subjects

T Tsuda

Publications and source records attributed to T Tsuda.

At least 559 records · Page 31Linked to original sources
PubMed1986

Possible involvement of cyclic AMP and calcium ion in prostaglandin E1-induced elevation of c-myc mRNA levels in Swiss 3T3 fibroblasts.

Prostaglandin E1 (PGE1) caused a rapid and dose-dependent increase in cAMP levels, followed by elevation of c-myc mRNA levels and then increased DNA synthesis in quiescent cultures of Swiss 3T3 fibroblasts. The dose-response curves of PGE1 were nearly the same for each of these three processes. Both 8-bromo-cAMP and forskolin increased c-myc mRNA levels to 40-50% and DNA synthesis to 70-80% of those caused by a maximally effective dose of PGE1. Under the comparable conditions, PGE1 did not stimulate diacylglycerol formation or activate protein kinase C. However, PGE1 did elevate cytoplasmic free Ca2+ concentration as measured with the fluorescent Ca2+ indicator quin 2. 8-Bromo-cAMP and forskolin were inactive in this capacity. The Ca2+ ionophore A23187 increased the level of c-myc mRNA. Diacylglycerol and Ca2+ mediate the elevation of c-myc mRNA levels which is caused by platelet-derived growth factor and fibroblast growth factor (Kaibuchi, K., Tsuda, T., Kikuchi, A., Tanimoto, T., Yamashita, T., and Takai, Y. (1986) J. Biol. Chem. 261, 1187-1192). In contrast, the present results suggest that both cAMP and Ca2+ are involved in this PGE1-induced response in Swiss 3T3 cells.

Alprostadil↗
PubMed1986

Involvement of three intracellular messenger systems, protein kinase C, calcium ion and cyclic AMP, in the regulation of c-fos gene expression in Swiss 3T3 cells.

In quiescent cultures of Swiss 3T3 cells, platelet-derived growth factor or fibroblast growth factor known to induce both protein kinase C activation and Ca2+ mobilization raised c-fos mRNA. This action of the growth factors was mimicked by the specific activators for protein kinase C, such as phorbol esters and a membrane-permeable synthetic diacylglycerol, and also by the Ca2+ ionophores, such as A23187 and ionomycin. Prostaglandin E1 known to elevate cyclic AMP also raised c-fos mRNA, and this action was mimicked by 8-bromo-cyclic AMP, dibutyryl cyclic AMP and forskolin. These results suggest that expression of the c-fos gene is regulated by three different intracellular messenger systems, protein kinase C, Ca2+ and cyclic AMP, in Swiss 3T3 cells.

Alprostadil↗
PubMed1986

Determination of phosphatidylglycerol in amniotic fluid for prediction of foetal lung maturity by microbore-column liquid chromatography.

Phosphatidylglycerol (PG) has been determined in amniotic fluid from 55 patients by using a microbore-column liquid chromatographic system. The present analysis time is 1 h 40 min for pretreatment of amniotic fluid and 20 min for a chromatographic run. From 2 ml of amniotic fluid, the PG content has been determined between 1.0 and 0.05 mg/dl. The detection limit of PG is 10 ng. As the injection volume (0.5 microliter) is small, repeated analyses are possible if necessary. It is concluded that, in the case of PG values over 0.10 mg/dl, a mother can deliver an infant without respiratory distress syndrome. This method is useful not only for the prenatal evaluation of lung maturity, but also for the assessment of any therapeutic effect.

Amniotic Fluid↗
PubMed1986

Activation of protein kinase C by the action of 9,11-epithio-11,12-methano-thromboxane A2 (STA2), a stable analogue of thromboxane A2, in human platelets.

Incubation of human washed platelets with 9,11-epithio-11, 12-methano-thromboxane A2 (STA2), a stable analogue of thromboxane A2, caused the activation of protein kinase C and myosin light chain (MLC) kinase to the same extents as those induced by thrombin as judged by measuring the phosphorylation of a 40-kilodalton protein and MLC, respectively. However, STA2 stimulated much less phosphoinositide turnover than thrombin. Furthermore, the doses of STA2 necessary for protein kinase C activation and phosphoinositide turnover were higher than those necessary for MLC kinase activation, although the doses of thrombin necessary for these three reactions were nearly the same. These results suggest that protein kinase C may be activated at the Ca2+ concentrations higher than those required for MLC kinase activation by the action of STA2, presumably due to the inability of this agonist to produce diacylglycerol in an amount enough to increase the affinity of the enzyme for Ca2+.

Blood Platelets↗
PubMed1986

Possible involvement of protein kinase C and calcium ion in growth factor-induced expression of c-myc oncogene in Swiss 3T3 fibroblasts.

The addition of platelet-derived growth factor and fibroblast growth factor to quiescent cultures of Swiss 3T3 fibroblasts rapidly induced protein kinase C activation and Ca2+ mobilization and afterwards markedly increased c-myc mRNA levels. 1-Oleoyl-2-acetylglycerol, a membrane-permeable synthetic diacylglycerol, and 12-O-tetradecanoylphorbol 13-acetate, a tumor-promoting phorbol ester, stimulated protein kinase C activation without Ca2+ mobilization. Inversely, Ca2+ ionophores, A23187 and ionomycin, elicited Ca2+ mobilization without protein kinase C activation. Both protein kinase C-activating and Ca2+-mobilizing agents were able to increase c-myc mRNA levels in an additive manner. Prolonged treatment of the cells with phorbol 12,13-dibutyrate, another protein kinase C-activating phorbol ester, led to the down-regulation and complete disappearance of protein kinase C. In these cells, 1-oleoyl-2-acetylglycerol and 12-O-tetradecanoylphorbol 13-acetate did not increase c-myc mRNA levels, but platelet-derived growth factor, fibroblast growth factor, and the Ca2+ ionophores, all of which still induced Ca2+ mobilization, stimulated the increase of c-myc mRNA levels. These results strongly suggest that both protein kinase C and Ca2+ may be involved in platelet-derived growth factor- as well as fibroblast growth factor-induced expression of the c-myc oncogene in Swiss 3T3 cells.

Animals↗
PubMed1986

Adrenergic modulation of pancreatic glucagon and insulin secretion in goats.

Five goats were used to investigate adrenergic influences on the secretion of both glucagon and insulin. The secretion of glucagon was augmented via alpha-adrenergic stimulation. The secretion of insulin was enhanced by stimulation of beta-adrenergic receptors and inhibited by alpha-adrenergic stimulation.

Animals↗
PubMed1986

Effects of Chinese herbal medicine "kanbaku-taiso-to" on transmembrane ionic currents and its local anesthetic action.

The Chinese herbal medicine, "Kanbaku-taiso-to" (KT) which is a mixture of Glycyrrhizae Radix, Triticii Semen and Zizyphi Fructus, sometimes shows marked effects on insomnia, infantile convulsions and emotional irritability. To elucidate the mechanism of the sedative effect of KT, effects of KT on the transmembrane ionic currents and local anesthetic action were examined and the following results were obtained. KT showed an inhibition of sodium, calcium and potassium currents in snail neurons. KT showed an inhibitory effect on pentylenetetrazol-induced bursting activity. KT had local anesthetic action on frog nerve fibers. Together with our previous study, these results suggest that KT has an inhibitory effect on hyperexcitability of the neuronal membrane and this is the main cause of the sedative effect of KT.

Action Potentials↗
PubMed1986

Effect of Chinese herbal medicine "kanbaku-taiso-to" on neuropharmacological tests.

The "Kanbaku-taiso-to" (KT), mixture of three herbal drugs, Glycyrrhizae Radix, Tritici Semen and Zizyphi Fructus, sometimes shows a marked effect on insomnia and infantile convulsions. The ancient Chinese medical book "Kinkiyoryaku" described the effectiveness of KT on emotional irritability. To elucidate the mechanism of action of KT, neuropharmacological screening tests were performed and the following results were obtained. KT lengthened the hexobarbital sleeping time; KT showed a marked prolongation of time to death in pentylenetetrazole (PTZ)-induced convulsions; locomotor activity was inhibited by 7-day continuous administration of KT. These results suggested that KT had a sedative effect on the nervous system.

Animals↗
PubMed1986

Influence of microinjection of insulin into hippocampus on hepatic acetate metabolism in rabbits.

Insulin was injected directly into the dorsal hippocampus (DHPC) of rabbits, and changes in hepatic acetate metabolism were studied. The injection of 50 microU insulin into the DHPC decreased the rates of 14C transfer from 14C-1-acetate into glucose and ketone bodies, and increased 14C transfer into cholesterol ester, triglyceride, free cholesterol and free fatty acids. But after insulin injection into the DHPC of rabbits with lesions of dorsal fornix (DFX), hepatic acetate metabolism did not differ from that of control rabbits, which received saline injection into the same brain region. From these results it might be suggested that the DHPC are parts of insulin-sensitive brain regulator system in the hepatic acetate metabolism.

Acetates↗
PubMed1986

Epidermal growth factor increases c-myc mRNA without eliciting phosphoinositide turnover, protein kinase C activation, or calcium ion mobilization in Swiss 3T3 fibroblasts.

Incubation of quiescent cultures of Swiss 3T3 cells with epidermal growth factor (EGF) caused an increase in c-myc mRNA. Under these conditions, EGF did not induce phosphoinositide turnover, formation of diacylglycerol, formation of inositol tris-, bis-, and monophosphates, protein kinase C activation, or Ca2+ mobilization. Although it has been reported that both protein kinase C and Ca2+ may be responsible for the platelet-derived growth factor- and fibroblast growth factor-induced increases in c-myc mRNA in Swiss 3T3 cells (Kaibuchi, K., Tsuda, T., Kikuchi, A., Tanimoto, T., Yamashita, T., & Takai, Y. (1986) J. Biol. Chem. 261, 1187-1192), these results indicate that neither protein kinase C nor Ca2+ is involved in the EGF-induced increase in c-myc mRNA, and that an unidentified system may be involved in this reaction.

Calcium↗
PubMed1986

Determination of L-ascorbic acid in tomato by isotachoelectrophoresis. Application of computer simulation system for setting of determination conditions to avoid the mixed-zone problem.

When the isotachoelectrophoretical method is used with HCl-beta-alanine as the leading electrolyte solution (pH 3.6), ascorbic acid forms a mixed zone with glutamic acid, and it is difficult to separate the two. Therefore, the application of a computer simulation system to separate the two acids was investigated. This system can be used with compounds for which the absolute electrophoretical mobility and dissociation constant have already been determined. Values for glutamic acid alone were entered in the data bank "SIPS-1", and then those for ascorbic acid were estimated from the values of similar compounds. Values for aspartic acid were used, and the electrophoretical behavior of ascorbic and glutamic acids was simulated at pH range from 3 to 9.9. Based on this simulation, separation appeared possible at pH 9.0 to 10.0, and indeed, experimental determination of ascorbic acid was successfully performed with a leading electrolyte solution composed of HCl-ethanolamine (pH 9.4) without any glutamic acid interference. Even though ascorbic acid is highly susceptible to oxidation in an alkaline medium, because the ascorbic acid solution is injected at the interface of the leading and terminal electrolyte solutions in the electrophoretical procedure, it does not come in contact with air during electrophoresis. This explains why ascorbic acid can be determined in an alkaline medium.

Ascorbic Acid↗
PubMed1986

Effects of monensin and salinomycin on amylase release from the superfused parotid segments of sheep and rat.

The effects of monensin and salinomycin (ionophorous antibiotics) on amylase release in the parotid glands were investigated in the superfused segments of sheep and rat. Monensin and salinomycin as well as acetylcholine and isoprenaline caused enhanced amylase release in a dose-dependent manner. Salinomycin was significantly more effective than monensin in both animals. The enhanced amylase release evoked by these ionophores and acetylcholine was significantly reduced in a calcium-free solution containing EGTA. From these results it is concluded that monensin and salinomycin transport calcium ions into the cytosol of parotid acinar cells from the extracellular fluid, resulting in amylase release.

Acetylcholine↗
PubMed1986

[Possible modes of action of growth factors and tumor promoters in the activation of the c-myc gene in Swiss 3T3 fibroblasts].

It has been suggested that the c-myc gene may play an important role in the regulation of cell proliferation. We have investigated the transmembrane signaling mechanisms of various growth factors and tumor promoters in Swiss 3T3 fibroblasts and have examined the causal relationship between these mechanisms and c-myc gene activation. Platelet-derived growth factor and FGF (fibroblast growth factor) induced the activation of diglyceride-protein kinase C and Ca2+ systems through phosphoinositide turnover, resulting in the activation of the c-myc gene. Epidermal growth factor did not activate these two systems but stimulated gene activation. Prostaglandin E1 elicited Ca2+ mobilization and cyclic AMP generation followed by c-myc gene activation. In contrast to these growth factors, tumor-promoting phorbol esters induced the direct activation of protein kinase C which led to c-myc gene expression. Bile acids, which are known to be colon tumor promoters, were inactive by themselves but enhanced FGF-induced diglyceride formation and thereby potentiated protein kinase C activation. It has not yet been examined whether bile acids potentiate FGF-induced activation of the c-myc gene. The growth factors described above and the phorbol esters stimulated DNA synthesis in the presence of insulin, whereas the bile acids potentiated FGF-induced DNA synthesis. These results strongly suggest that three messenger systems, diglyceride, Ca2+ and cyclic AMP, may be involved in c-myc gene activation which may be implicated in DNA synthesis in Swiss 3T3 cells.

Animals↗