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Biomedical subjects

S Kigoshi

Publications and source records attributed to S Kigoshi.

At least 73 records · Page 4Linked to original sources
PubMed1986

Ryanodine has no effect on the Ca current in single ventricular cells of guinea-pig.

The Ca current was isolated and the effects of ryanodine were examined in Cs-loaded guinea-pig ventricular myocytes. The time course, amplitude and voltage dependence of the Ca current were not affected by the external or internal application of ryanodine, thereby suggesting that this alkaloid has no direct action on the Ca channel and that the inactivation of the Ca channel is not affected by Ca released from sarcoplasmic reticulum, at least under the present experimental conditions.

Alkaloids↗
PubMed1986

Mechanisms of tetraethylammonium-induced contraction in the canine coronary artery.

Tetraethylammonium chloride (TEA) at concentrations over 10(-3) mol/l produced a concentration-dependent contraction in the isolated canine coronary artery. We investigated mechanisms of the contractile response and the effects of various vasodilators on the contraction. While phentolamine, propranolol, guanethidine, atropine and tetrodotoxin did not affect the TEA response, the response was attenuated by a reduction in the extracellular potassium concentration and was augmented by an increase in the concentration of potassium. The response was also augmented by other potassium conductance blockers (CsCl and 4-AP). On the other hand, the contractile response to phenylephrine used as a control drug was not affected by the extracellular potassium concentration or by CsCl. Verapamil or removal of extracellular calcium abolished the TEA, but not the phenylephrine response. Nicorandil, isoproterenol, adenosine or glyceroltrinitrate produced an equipotent relaxation in the coronary arteries contracted by TEA and by phenylephrine, whereas acetylcholine relaxed to a lesser extent the arteries contracted by TEA than those contracted by phenylephrine. These results suggest that the TEA-induced contractions are strictly dependent on the reduction of potassium conductance and extracellular calcium while the phenylephrine-induced contractions are not and that the relaxing effects of tested vasodilators, except for acetylcholine, may not be affected by such different contractile mechanisms.

4-Aminopyridine↗
PubMed1986

Copper-induced alteration of muscarinic binding in bovine adrenal medulla.

In microsomes of bovine adrenal medulla, there were two affinity binding sites for carbamylcholine with a high and a low affinity. Copper (1-10 microM) largely enhanced the affinity of carbamylcholine at the low affinity binding site, with a slight increase in the affinity at the high affinity binding site. On the other hand, copper slightly decreased the binding affinity of pirenzepine and atropine. Thus, low concentrations of copper modulate the muscarinic receptors in the adrenal medulla by selectively increasing agonist affinity.

Adrenal Medulla↗
PubMed1986

DJ-7141, a new alpha-2 agonist with only a mild hypotensive action.

The pharmacological profile of a newly synthesized imidazole derivative, DJ-7141, was examined with special reference to alpha-2 adrenoceptors. In the rat vas deferens and dog mesenteric artery, DJ-7141 at concentrations over 10(-9) M selectively acted on the presynaptic alpha-2 adrenoceptors on the sympathetic nerve terminals and inhibited the contractions induced by electrical transmural stimulation. The potency of DJ-7141 was almost the same as those of clonidine and guanabenz. DJ-7141 also acted on the postsynaptic alpha-2 adrenoceptors to contract the dog saphenous vein. However, no alpha-1 agonist and antagonist actions were found at concentrations showing presynaptic alpha-2 agonist activity. In contrast to DJ-7141, clonidine produced an apparent contraction in the dog mesenteric artery, and the response was inhibited by prazosin. In urethane-anesthetized rats, clonidine at doses ranging from 0.003 mg/kg to 0.03 mg/kg produced a marked and prolonged hypotension, while DJ-7141 at such doses failed to produce a reduction of blood pressure. From these results, it is suggested that, in contrast to clonidine and other alpha-2 agonists, DJ-7141 is a unique alpha-2 agonist which shows high affinity to peripheral alpha-2 adrenoceptors but only a mild hypotensive activity.

Adrenergic alpha-Agonists↗
PubMed1985

Contractile action of yohimbine in the dog basilar artery.

Yohimbine (10(-8) to 10(-4) M) produced a concentration-dependent contraction of the isolated dog basilar artery. The maximal amplitude of the contraction induced by yohimbine was approximately 50% of that induced by 5-hydroxytryptamine (5-HT) and twice as large as that of noradrenaline. This response to yohimbine (3 X 10(-7) M) was attenuated by 5-HT receptor antagonists such as 5-methoxygramine, methysergide and ketanserin. Phentolamine also antagonized the yohimbine response but prazosin and DG-5128 did not. The 5-HT antagonists and phentolamine produced similar inhibition of the response to 5-HT. Propranolol, atropine and diphenhydramine did not modify the contractile responses to yohimbine and 5-HT. These results suggest that the contractile response to yohimbine is mediated through 5-HT receptors. In addition to the contractile action, yohimbine at concentrations over 10(-6) M inhibited the contractile response to 5-HT. Thus, the possibility that yohimbine is a partial agonist on 5-HT receptors in the dog basilar artery has to be considered.

Animals↗
PubMed1985

Selective interaction of DG-5128 with a low agonist affinity state of alpha-2 adrenoceptor.

Using rat cerebral cortex membranes, the inhibitory effect of DG-5128 against (3H)-clonidine binding was compared between low (alpha 2L) (in the presence of EDTA) and high (alpha 2H) affinity states (in the presence of excess magnesium) of alpha 2-adrenoceptor for agonists. The Ki value (pKi=6.79) of DG-5128 in the alpha 2L state was 6.4 times higher than the value in the alpha 2H state. Thus, DG-5128 produces alpha 2-adrenoceptor antagonism through the selective interaction with an alpha 2L state of the receptor.

Animals↗
PubMed1985

Cytotoxicity of cortisone-resistant lymphocytes from mice treated with a group A streptococcus or Freund's complete adjuvant against tumor cells.

The cortisone-resistant lymphocytes (CR lymphocytes) of mice treated with a group A streptococcus, Su strain, or Freund's complete adjuvant (FCA) were examined for their cytotoxicity on Ehrlich carcinoma cells and sarcoma-180 cells. Female mice of the ddY strain, 7-8 weeks of age, were injected subcutaneously with streptococci or FCA in emulsion, and they were killed 14 days later. To obtain CR lymphocytes, mice treated with and without agents were injected intraperitoneally with hydrocortisone acetate (125 mg/kg) 2 days before killing. Tumor cells and CR lymphocytes from thymus, spleen or mesenteric lymph node were suspended in Hanks balanced salt solution supplemented with 2% bovine albumin. The cytotoxicity of CR lymphocytes on tumor cells was examined by the Winn test: Tumor growth was observed in mice inoculated s.c. with the mixture of tumor cells (T) and CR lymphocytes (L) at a T/L ratio of 1/10 (10(6) tumor cells/mouse). The mesenteric and thymic CR lymphocytes of mice treated with streptococci or FCA were more effective than the corresponding lymphocytes of untreated mice in suppressing the tumor growth in animals given the cell mixture. This suggests that the treatment of mice with streptococci or FCA results in an enhancement in the cytotoxicity of mesenteric and thymic CR lymphocytes against the tumor cells.

Animals↗
PubMed1984

The selectivity of DG-5128 as an alpha 2-adrenoceptor antagonist.

DG-5128 (2-[2-(4,5-dihydro-1H-imidazol-2-yl)-1-phenylethyl]pyridine dihydrochloride sesquihydrate) at concentrations up to 10 microM inhibited [3H]clonidine binding more effectively than it did [3H]prazosin binding in rat cerebral cortex membranes. The mode of inhibition was homogeneous and consistent with the law of simple mass action. DG-5128 exhibited a 7.4 times higher affinity (pKi = 6.28) toward alpha 2-adrenoceptors than alpha 1-adrenoceptors. The results indicate that DG-5128 is a preferential alpha 2-antagonist.

Adrenergic alpha-Antagonists↗
PubMed1984

Conduction-block induced by capsaicin in crayfish giant axon.

The effects of capsaicin on the crayfish giant axon were examined by using microelectrode and double sucrose gap-voltage clamp methods. Capsaicin (1-3 X 10(-4) M), when applied externally, had no effect on the resting membrane potential but gradually suppressed the action potential. The rate of rise of the action potential was simultaneously decreased. Voltage clamp experiments revealed the following: capsaicin (10(-4) M) reduced more effectively the transient sodium current than the steady-state potassium current. Inhibition of the sodium current was derived from a decrease in maximum sodium conductance, as the equilibrium potential remained much the same. The inhibitory effects of capsaicin on action potentials and membrane ionic currents were slowly reversible after removal of capsaicin. These results indicate that capsaicin seems to produce a conduction block in the crayfish giant axon due to an inhibition of sodium channels. The significance of these findings is discussed in relation to the sensory neurone-blocking action of capsaicin.

Action Potentials↗
PubMed1984

Nonadrenergic nature of prazosin-resistant, sympathetic contraction in the dog mesenteric artery.

Electrical transmural stimulation of the isolated dog mesenteric artery produced a contractile response which was abolished by guanethidine and 6-hydroxydopamine but not by prazosin. Approximately 60% of the response seen with a frequency of 3 Hz remained after the treatment with prazosin. The prazosin-resistant contraction induced by electrical transmural stimulation was potentiated by other alpha adrenoceptor antagonists (phentolamine, phenoxybenzamine, tolazoline and DG-5128). Alpha-2 adrenoceptor agonists (including norepinephrine) attenuated the prazosin-resistant contraction and this attenuation was antagonized by the alpha antagonists mentioned above. Cocaine slightly inhibited the prazosin-resistant contraction, whereas this drug markedly augmented the contractile response to electrical stimulation before treatment with prazosin. In reserpine-treated mesenteric arteries also, electrical transmural stimulation produced a contraction and this was neither suppressed nor potentiated by prazosin and other alpha antagonists but was attenuated by alpha-2 agonists. Guanethidine and 6-hydroxydopamine abolished the prazosin-resistant contraction in reserpine-treated arteries. Nicotine, but not tyramine, also produced such prazosin-resistant contraction in reserpine-treated and untreated arteries. Exogenous norepinephrine produced a concentration-dependent contraction in reserpine-treated and untreated arteries and the responses were competitively antagonized by prazosin. These results indicate that the prazosin-resistant contractions of the dog mesenteric artery induced by electrical transmural stimulation and nicotine are sympathetic in origin but not adrenergic in nature. Such prazosin- resistant contraction was observed in the dog mesenteric vein but not in carotid and femoral arteries, thereby suggesting that the nonadrenergic component may play an important role in the regulation of visceral blood flow.

Animals↗
PubMed1983

Effect of the centrally acting antitussives on ascites tumor cells.

Dextromethorphan, dimemorfan, dihydrocodeine and oxymethebanol, centrally acting antitussives, were examined for their effect on Ehrlich carcinoma cells and sarcoma-180 cells in vitro or in vivo. The tumor cells were suspended in Hanks balanced salt solution (pH 7.4) supplemented with 2% bovine albumin, and they were incubated with and without 1 mM drugs at 37 degrees C for 120 min. The incubation of the tumor cells with dextromethorphan or dimemorfan resulted in a decrease in the proportion of the viable cells (less than 25% after 120 min). However, no significant change was observed in the proportion of the viable tumor cells during the incubation with and without the other drugs (80-83% after 120 min). In addition, mice given the tumor cells i.p. were injected intraperitoneally with drugs (20-80 mg/kg/day) once daily for 5 successive days, and their survival time was observed. There was a slight difference in the survival time between mice treated with and without dextromethorphan or dimemorfan. However, a significant difference was found in the survival time between mice treated with and without dextromethorphan when mice given Ehrlich carcinoma cells were injected with the drug (40 mg/kg/time) twice a day for 5 days (about 18 days and 29 days). These results indicate that dextromethorphan and dimemorfan are cytotoxic to the tumor cells in vitro and in vivo.

Animals↗
PubMed1982

Effect of pentazocine and related compounds on the lipid composition of Ehrlich ascites tumor cells.

The effect of pentazocine and its related compounds on the lipid composition of Ehrlich ascites tumor cells was examined. Ehrlich tumor cells were suspended in Hanks balanced salt solution (pH 7.4) supplemented with 2% bovine albumin (2 x 10(6) cells/ml) and incubated at 37 degrees C for 120 min with and without 10(-3) M of pentazocine, morphine or dihydrocodeine. After incubation, the tumor cell lipids were extracted with chloroform-methanol (2:1, v/v), and they were analyzed quantitatively by the dichromate reduction procedure of Amenta. The tumor cells treated with pentazocine contained lower levels of triglycerides and cholesterol esters as compared with the tumor cells incubated alone. The amounts of triglycerides and cholesterol esters in the tumor cells treated with and without pentazocine were about 82 and 23 mg/10(10) cells and 182 and 55 mg/10(10) cells, respectively (P less than 0.01), whereas there was only a slight difference in the contents of these neutral lipids between the tumor cells treated with and without (10(-3) M morphine or dihydrocodeine. In addition, the fatty acid pattern of triglycerides and cholesterol esters from the pentazocine-treated tumor cells differed markedly from that of the corresponding lipids from the tumor cells incubated alone.

Animals↗
PubMed1981

Effect of streptococcal lipids on Ehrlich ascite tumor cells.

The lipids extracted from group A hemolytic streptococci (strain Su, Blackmore and C203U) were examined for their antitumor effect against Ehrlich ascites carcinoma in mice. Total lipids were extracted from streptococcal cells according to the method of Folch et al, and separated into 9 lipid fractions by thin-layer chromatography, using various solvent systems. Three fractions were compound lipids (diphosphatidyl glycerols, monoglucosyl diglycerides and diglucosyl diglycerides), and the remaining 6 fractions were neutral lipids such as free fatty acids, glycerides, sterols and sterol esters. For biological testing, the lipid fractions suspended in physiological saline containing Tween 20 (0.02%) were incubated with Ehrlich tumor cells at 37 degrees C for 90 min, and the cell mixture was given intraperitoneally into mice thereafter. Among 9 lipid fractions, free fatty acids and monoglycerides from the streptococci examined were highly active in suppressing the depressing the development of ascites carcinoma in mice. Diphosphatidyl glycerols from two strains of streptococci (BLackmore and C203U) were also effective in suppressing the tumor growth in mice. However, the other lipid fractions had little effect on the tumor growth.

Animals↗
PubMed1981

Effect of pentazocine on Ehrlich ascites tumor cells.

The effect of pentazocine, a non-narcotic analgesic, on Ehrlich ascites tumor cells was examined in vitro and in vivo. To test the in vitro effect of pentazocine, Ehrlich tumor cells suspended in Hanks balanced salt solution (BSS, pH 7.4) supplemented with 2% bovine albumin were incubated with various concentrations of the drug (0.10-1.0 mM) at 37 degrees C for 120 min. After incubation, the tumor cells in BSS were inoculated subcutaneously into the right flank of mice (10(6) cells/mouse). All mice given the tumor cells incubated alone developed solid tumor. However, no tumor growth was observed in groups of mice given the tumor cells pretreated with 0.3 or 1.0 mM pentazocine. The in vivo effect of pentazocine was then examined against Ehrlich ascites carcinoma in mice. Mice inoculated intraperitoneally with Ehrlich tumor cells in BSS (2 x 10(6) cells/mouse) were given various doses of pentazocine (20-80 mg/kg/day) intraperitoneally once a day for 5 successive days. The average survival time in a group of mice given the tumor cells alone was about 19 days, and the survival time was about 29 days in a group of animals treated with pentazocine in a dose of 80 mg/kg/day (p less than 0.01).

Animals↗
PubMed1980

Comparative experiments with hemolytic streptococcus and its anticancer preparations (OK-431 and OK-432) for their cytolytic activity.

The comparative in vitro cytolytic effects of living hemolytic streptococcus, a low virulent su-strain, and its streptococcal preparations (OK-431 and OK-432) on Ehrlich ascites carcinoma cells were investigated. It was shown that living cocci and OK-431 released 51Cr from 51Cr-labeled tumor cells by contact in vitro, but OK-432 did not release 51Cr at all. Moreover, the effects of living cocci, OK-431 and OK-432 were also examined by assay of the release of RNA and DNA from the tumor cells. It was confirmed that living cocci released RNA and DNA, but OK-431 released slightly RNA, not DNA from the tumor cells, whereas OK-432 did not cause these release at all. Consequently, it appeared that living cocci of Su-strain have more cytolytic activity than OK-431, and that OK-432 have no cytolytic activity in tumor cells.

Animals↗
PubMed1979

Cytolytic action of 60-F derived from live hemolytic streptococci against Ehrlich carcinoma cells.

The effect of 60-F, a fraction obtained by 0.5 approximately 0.6 saturation of ammonium sulfate of streptomycin-pretreated cell-free extract from live hemolytic streptococci (avirulent Su strain), on release of 51Cr from the 51Cr-labeled Ehrlich ascites carcinoma cells was studied with following results: a) 60-F was found to be highly effective in releasing 51Cr from 51Cr-labeled Ehrlich ascites carcinoma cells. b) Additionally, destructive picutres of the tumor cells contacted with 60-F in vitro was observed by phase-contrast microscopic examination. c) Indication was that the 51Cr-releasing assay method is also useful for the study of the direct cytolytic effect of 60-F.

Animals↗