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Biomedical subjects

S Imai

Publications and source records attributed to S Imai.

At least 559 records · Page 31Linked to original sources
PubMed1987

[Effects of vasodilators on cyclic contraction induced by 3,4-diaminopyridine in isolated porcine coronary arteries].

3,4-Diaminopyridine (3,4-DAP), which is known to decrease K conductance, produced spontaneous repetitive phasic contractions of a regular (28/60) and an irregular (15/60) cycle or tonic contraction (16/60) following a latent period of 5-100 min in isolated porcine coronary arteries. Effects of pinacidil, a newly-synthesized vasodilator, were investigated using the preparation in which 3,4-DAP produced phasic contractions of the regular cycle in comparison with those of various vasodilators. Pinacidil produced dose-dependent prolongation of the cycle and reduced the peak tension and the tension at the relaxation phase, a mode of action that closely resembles that of nicorandil, suggesting the increase in K conductance and hyperpolarization. Nifedipine (10(-8) M) and dilazep (10(-4) M) markedly reduced the peak tension, while adenosine, dipyridamole and nitroglycerin did not produce such effects. The latter three drugs produced a prolongation of the cycle and reduced the tension of the relaxation phase. These data suggest that reduction of K conductance and activation of the voltage-dependent Ca channel may play an important role in initiation of the spontaneous repetitive phasic contraction in porcine coronary artery.

4-Aminopyridine↗
PubMed1987

Effects of bunitrolol on adrenergic and serotonergic receptors.

To assess the importance of anti-adrenergic and anti-serotonergic activities of bunitrolol for its efficacy as an antihypertensive and antianginal agent, effects of this substance on the binding of adrenergic and serotonergic agents to the respective receptors of the rat brain, rat heart, dog brain, and/or dog aorta were examined using the radioligand binding assay methods. In addition, the pA2 values of bunitrolol as an antagonist against the positive chronotropic and inotropic actions (beta 1-adrenoceptor) of isoproterenol were also determined by pharmacological methods using the isolated guinea pig atria. To assess the specificity, pA2 values were also obtained in the isolated trachea (beta 2-adrenoceptor) using isoproterenol as an agonist and in the isolated aorta from the guinea pig and the rat using phenylephrine as an agonist (alpha 1-adrenoceptor). A strong inhibition by bunitrolol of 3H-dihydroalprenolol (3H-DHA) binding to beta-adrenoceptors was observed, while the inhibition of 3H-prazosin binding to alpha 1-adrenoceptors, 3H-serotonin binding to 5HT1-receptors. 3H-p-aminoclonidine binding to alpha 2-adrenoceptors, and 3H-ketanserin binding to 5HT2-receptors were found to be very weak. The rank order of antagonistic potencies of bunitrolol against the adrenergic receptors as assessed with pA2 values were beta 1 greater than beta 2 much greater than alpha 1. From these two different types of experiments, it is clear that the antihypertensive and antianginal effects of bunitrolol are mainly due to its beta-blocking actions, with the alpha 1-blocking action of this drug playing a minor role.

Animals↗
PubMed1987

Ventricular pressure-heart rate product before induction of ischemia as a determinant of the reperfusion-induced accumulation of calcium within myocardium.

Using the product of heart rate (HR) and left ventricular developed pressure (LVP) as a measure of the total mechanical energy required for contraction (TMEFC), experiments were performed with isolated perfused heart preparations of the guinea pig to establish the importance of TMEFC before induction of ischemia for induction of calcium accumulation within ischemic reperfused myocardium. Two calcium antagonists, diltiazem and nicardipine, and prazosin produced a dose-related suppression of the calcium accumulation when given prior to induction of ischemia (except for the highest dose of nicardipine), while they were ineffective when given only during the period of reperfusion, and the suppression was found to be closely correlated with the decrease in HRxLVP before induction of ischemia. The failure of the highest dose of nicardipine to suppress calcium accumulation (while producing a dose-related decrease in HRxLVP) was not associated with an increase in cyclic AMP. These findings are compatible with the idea that TMEFC before induction of ischemia is a prime determinant of calcium accumulation within the ischemic reperfused myocardium.

Animals↗
PubMed1987

Immunoreactive epidermal growth factor in mouse digestive organs. Use of a sensitive enzyme immunoassay.

A sandwich enzyme immunoassay (ELISA) system for mouse epidermal growth factor (EGF), which has a high sensitivity (500 fg/tube), has been established. It makes it possible to measure minute amounts of immunoreactive EGF in various mouse tissue without pretreatment. The immunoreactive EGF concentrations in digestive tissues of adult mice were much lower than previously reported. A significant sex difference was detected not only in the submandibular gland, but also in the oesophagus and forestomach. Although sialoadenectomy decreased the immunoreactive EGF contents in the alimentary tract to 4.2-23.8% of the pre-operative levels, the duodenal immunoreactive EGF was unaffected. Positive immunostaining was observed in the submandibular and sublingual gland, but not in the other digestive tissues, including the duodenum. These data implied that most of the EGF in the digestive tissues was derived mainly from the saliva and that a small amount of endogenous EGF existed in the duodenum. The physiological role of exogenous salivary EGF in the alimentary tract and the origin of endogenous duodenal EGF are discussed.

Animals↗
PubMed1987

Effects of nicorandil on the conductive coronary artery of the dog.

The effects of nicorandil (2-nicotinamidoethyl nitrate, SG-75) on the conductive coronary artery were studied and compared with the effects of nitroglycerin and nifedipine. In isolated perfused canine heart preparations with a support dog, nicorandil produced a decrease in the resistance of the conductive coronary artery at reduced perfusion pressures, whereas nitroglycerin had similar effects even at normal perfusion pressures. In anesthetized closed-chest dogs, nicorandil and nitroglycerin produced an increase in the diameter of the conductive coronary artery (nicorandil less than nitroglycerin). Nifedipine failed to produce dilatation of the conductive coronary artery in both preparations. In isolated ring preparations of conductive coronary artery, all three compounds produced relaxation of the potassium-induced contracture, but only nicorandil and nitroglycerin reversed the lanthanum-induced contracture.

Animals↗
PubMed1987

[Placental specific findings in twin pregnancies with hydramnion].

Eleven of 157 twin pregnancies were complicated with polyhydramnios. Chorionicity, vascular anastomosis and insertion of the umbilical cord were analyzed with relation to polyhydramnios. 1. Polyhydramnios was found commonly in monochorionic placentation. 2. Vascular anastomosis was found in 40% of monochorionic polyhydramnotic placentas, which was lower than the anastomosis of monochorionic non-polyhydramniotic placentas. 3. The placentas with hydramnios had a higher incidence of abnormal umbilical insertion (marginal or velamentous insertion). These data indicate that incompetent vascular connections between the two fetoplacental circulations may be the pathogenesis of polyhydramnios.

Female↗
PubMed1987

Effects of the new dihydropyridine derivative 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid methyl 6-(5-phenyl-3-pyrazolyloxy)hexyl ester on the cardiohemodynamics and the energy metabolism of ischemic myocardium.

To characterize the effects of a new calcium antagonist of the dihydropyridine type, 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic++ + acid methyl 6-(5-phenyl-3-pyrazolyloxy) hexyl ester (CV-159) on the cardiovascular system, experiments were performed in the anesthetized open-chest dogs and in the heart-lung preparation with a support dog in comparison with those of nicardipine. In the anesthetized dog CV-159 (1-30 micrograms/kg) produced a dose-related decrease in mean blood pressure with a decrease in total peripheral resistance, and an increase in coronary flow. There was a reflex increase in heart rate, aortic flow and left ventricular dP/dtmax. Nicardipine (1-30 micrograms/kg) produced qualitatively similar changes in these parameters, although the onset of action was quicker and the duration shorter. Hypotensive effects of CV-159 were approximately three times less potent than those of nicardipine. In doses above 3 micrograms CV-159 produced a long-lasting increase in coronary flow and slight negative inotropic and chronotropic effects in the heart-lung preparation. In doses above 1 microgram nicardipine produced an increase in coronary flow without producing any change in the cardiac functions. The increase in coronary flow produced by these two compounds was not associated with an increase in myocardial oxygen consumption. Studies conducted with 31P-NMR in the isolated perfused heart preparation of the rat demonstrated no improvement of the ischemic derangement of the myocardial energy metabolism with doses of CV-159 and nicardipine producing an increase in coronary flow rate, but no change in myocardial oxygen demand as assessed by heart rate X left ventricular pressure.

Animals↗
PubMed1987

Thymosin-alpha 1 increases the capability to produce interleukin-3 but not interleukin-2 in nu/nu mice.

Thymosin-alpha 1 increased the capability of nu/nu mice to produce interleukin (IL)-3 but not IL-2 when administered intraperitoneally at doses of 0.5 and 5.0 micrograms/kg twice a week for 3-6 weeks. Thy-1-positive cells were responsible for the production of IL-3, which was determined by proliferation of the IL-3-dependent cell line (FDC-P2) as well as by augmentation of the in vitro growth of hematopoietic stem cells (colony-forming unit S [CFU-S]). The IL-3 activity released by nu/nu splenocytes emerged in fractions coincidentally with IL-3 released by WEHI-3 cells on Mono Q anion-exchange chromatography. However, IL-2 activity determined by proliferation of the IL-2-dependent cell line was not detected in any fractions of the same chromatography. These findings indicate that IL-2 is not always coproduced with IL-3 by Thy-1-positive cells. This suggests, taken together with results from previous studies about the cells producing IL-2 and IL-3 by other investigators, that thymosin-alpha 1 exerts its effect at an early stage of T cell differentiation to induce a T cell subpopulation capable of producing IL-3 (but not yet IL-2). Based on the present findings, we discuss the mechanism of action by which thymosin-alpha 1 exerts its diverse effects in immunosuppressed hosts but not a potentiating effect in healthy normal animals or in in vitro assays of T cell function.

Animals↗
PubMed1987

Complement activation in fetuses: assessment by the levels of complement components and split products in cord blood.

The whole complement activity (CH50) and concentrations of components (C1q, C3, and C4) and C3 split product (C3d) were determined in the cord blood of 172 newborns between 16 and 42 weeks of gestation. Histological examination of their placentas revealed that the extent of complement activation was significantly higher in those with some degree of inflammation in the amnion than in those with normal amnion. The correlation between the complement levels and gestational age was higher in those with no amnionitis. In some cases the level of C3d at an early gestational age was as high as that in adults. The C3 activation system seems to be well developed even before week 25 of gestation. Among the complement components, C3d was the most sensitive indicator of placenta inflammation. As placenta inflammation may reflect intrauterine infection, the measurement of C3d levels may be of diagnostic value.

Adult↗
PubMed1987

A case report of cysticercosis caused by Cysticercus longicollis, a larval form of Taenia crassiceps in a woodchuck (Marmota monax).

Cysticercosis was found in one of 18 woodchucks imported from the United States and maintained in our laboratory for study of hepatitis and hepatocellular carcinoma. The lesions found in subcutaneous area, lungs and maxillary sinus were multiple cysts containing numerous cysticerci identified as Cysticercus longicollis, a larval form of Taenia crassiceps.

Animals↗
PubMed1987

[Seasonal changes in the course of atopic eczema].

To investigate seasonal changes of the course of atopic dermatitis, questionnaires were sent to patients treated for this condition in 1984. The replies obtained from 506 patients indicated that in most of them the skin condition deteriorated in winter and improved in summer. However, among patients older than 5 years the proportion of those with deterioration in summer was higher. It is suggested that seasonal factors greatly influence the skin condition of patients with atopic dermatitis and that these seasonal variations often depend on age and environment.

Adolescent↗