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Biomedical subjects

A Narimatsu

Publications and source records attributed to A Narimatsu.

At least 55 records · Page 3Linked to original sources
PubMed1987

Does the positive inotropic action of a novel cardiotonic agent, MCI-154, involve mechanisms other than cyclic AMP?

MCI-154 is a new positive inotropic agent with vasodilating property. Experiments were carried out in the canine isolated right ventricular muscle in order to elucidate whether or not cyclic AMP is involved in the positive inotropic effect (PIE) of MCI-154. MCI-154 (10(-7) to 10(-4) M) produced a concentration-dependent PIE amounting to 75% of the maximal effect of isoproterenol. MCI-154 did not affect the time to peak tension and had a tendency to shorten the relaxation time and total duration of contraction. Pindolol, reserpine-pretreatment or tetrodotoxin did not modify the PIE of MCI-154. MCI-154 increased the cyclic AMP levels only at 3 X 10(-4) M, whereas CI-914, of which chemical structure is similar to that of MCI-154, elevated definitely the cyclic AMP at the lower concentrations (10(-5) to 10(-4) M). Carbachol at a concentration known to decrease markedly the PIE of amrinone, milrinone and papaverine, did not affect the PIE of MCI-154. MCI-154 inhibited the activity of a crude phosphodiesterase (PDE) from the canine ventricular muscle and it enhanced the PIE of isoproterenol, which implied the involvement of cyclic AMP. However, the maximal inhibition of PDE by MCI-154 remained less than 18%. Amrinone, milrinone and papaverine inhibited more potently the PDE activity than MCI-154. These results suggest that the elevation of cyclic AMP levels is only partially involved in the PIE of MCI-154 in the canine right ventricular muscle, and that MCI-154 may have novel mechanisms of action different from those of amrinone, milrinone and CI-914 that are largely cyclic AMP-dependent.

Animals↗
PubMed1987

Increase in Ca++ sensitivity of the contractile system by MCI-154, a novel cardiotonic agent, in chemically skinned fibers from the guinea pig papillary muscles.

The effects of MCI-154, a novel cardiotonic agent, on the contractile protein system and the sarcoplasmic reticulum (SR) were investigated by using thin bundles of chemically skinned fibers from the guinea pig papillary muscles. In the skinned muscle fibers treated with 50 micrograms/ml of saponin, MCI-154 shifted the -log[Ca++]M-tension relation curve to the left and upward in the concentration-dependent manner (10(-7) to 10(-4) M). This was confirmed also in the skinned muscle fibers treated with 250 micrograms/ml of saponin which destroyed not only the surface membrane but also the function of SR. Sulmazole (10(-4) M) shifted the -log[Ca++]M-tension relation curve to the left but the effect was about 100 times less potent than that of MCI-154. Unlike MCI-154, sulmazole had little effect on the maximum tension development induced by -log[Ca++]M 4.4. Milrinone did not affect the Ca++-induced tension development in the skinned cardiac fibers. Higher concentration of MCI-154 (10(-4) M) also increased amplitude of -log[Mg-ATP]M-tension-curve in the absence of free Ca++ ion (bell-shaped curve) to the upward. Initial rate and plateau phase of Ca++ uptake by the SR in the skinned fibers treated with 50 micrograms/ml of saponin was increased slightly by MCI-154 at the concentrations of 10(-6) and 10(-4) M. MCI-154 had no effect on the Ca++-induced Ca++ release mechanism in the SR. These results suggest that an increase in Ca++ sensitivity of the contractile protein system is responsible for, at least in part, the mechanism of the positive inotropic action of MCI-154.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1987

Cardiovascular pharmacology of 6-[4-(4'-pyridyl)aminophenyl]-4,5-dihydro-3(2H)-pyridazinone hydrochloride, a novel and potent cardiotonic agent with vasodilator properties.

The cardiovascular profile of 6-[4-(4'-pyridyl)aminophenyl]-4,5-dihydro-3(2H)-pyridazinone hydrochloride (MCI-154), a novel cardiotonic agent structurally different from cardiac glycosides and beta-adrenoceptor agonists, was investigated in vivo. In anesthetized, open-chest dogs, MCI-154 (0.3-100 micrograms/kg i.v., bolus injection) produced dose-dependent increases in dP/dtmax and cardiac output, and decreases in arterial blood pressure and total peripheral resistance with a relatively small increase in heart rate. The positive inotropic effect of MCI-154 was more potent than those of amrinone and milrinone. In anesthetized, intact-chest dogs, infusion of MCI-154 (0.3-3 micrograms/kg/min i.v.) also exerted a positive inotropic effect. P.o. administrations of MCI-154 (10-300 micrograms/kg) increased dP/dtmax in conscious beagle dogs. The cardiotonic effect of MCI-154 was not attenuated by blockade of autonomic receptors, catecholamine depletion and prostaglandin synthesis inhibition. MCI-154 (0.3-30 micrograms i.a.) produced a direct vasodilator effect in the canine hind-limb. MCI-154 (3 and 30 micrograms/kg i.v.) was effective in heart failure models induced with high doses of propranolol or verapamil. The potent cardiotonic and vasodilator activities of MCI-154 revealed by the present study suggest that this agent would be an effective remedy for the treatment of heart failure.

Anesthesia↗
PubMed1986

[General pharmacological action of 4-(o-benzylphenoxy)-N-methylbutylamine hydrochloride (MCI-2016, bifemelane hydrochloride). Influence on respiratory and cardiovascular systems, renal function, autonomic nervous system, isolated smooth muscle and digestive organs].

MCI-2016 at 3 mg/kg, i.v., caused slight changes in systemic blood pressure (SBP), heart rate (HR), respiratory rate (RR) and ECG but at 10 mg/kg, i.v., it caused a significant increase in RR, decrease in SBP, increase or decrease in HR and a moderate change in ECG. Biphasic changes in SBP, HR and blood flow were sometimes observed after high doses. MCI-2016 also decreased SBP at 30 mg/kg, i.p., in SHR. MCI-2016 (50 mg/kg, p.o./day) showed little influence on SBP, HR and ECG in conscious beagle dogs. In isolated hearts, MCI-2016 decreased HR and contractility at the concentrations above 10(-5) g/ml, and 30 micrograms, i.a. MCI-2016 prolonged the AVCT at 10 mg/kg, i.v. MCI-2016 (i.v. or i.a.) moderately increased cerebral and femoral artery blood flows. MCI-2016 did not change CMRO2, but decreased MVO2. Coronary and renal artery flows were moderately increased by 10 mg/kg, i.v., of MCI-2016. Renal function was suppressed after 10 mg/kg, i.v., or 300 mg/kg, p.o., of MCI-2016. MCI-2016 potentiated the action of NE (increase in SBP, contractions of nictitating membrane and vas deferens), but showed little anti-cholinergic action. In contrast, MCI-2016 moderately increased gastrointestinal motility and salivatory response. As for the influence on isolated smooth muscles, MCI-2016 antagonized the contraction of blood vessels by high K+ at 10(-6) g/ml, or more, and it depressed the contractions by ACh, 5-HT, histamine and BaCl2 and also depressed spontaneous movements of uterus and ileum at 10(-5) M or more, in a nonspecific manner. MCI-2016 had no influence on liver damage and bile secretion, but inhibited stress ulcer and gastric acid secretion on the one hand, and caused gastric damage (125 mg/kg p.o., or more) on the other hand.

Animals↗
PubMed1986

[General pharmacological action of tritoqualine (TRQ; (+/-)-(R*)-7-amino-4, 5, 6-triethoxy-3-[(R*)-5, 6, 7, 8-tetrahydro-4-methoxy-6-methyl-1, 3-dioxolo [4, 5-g] isoquinolin-5-yl] phthalide].

The general pharmacological action of TRQ was investigated, and the following results were obtained: With regard to its influence on the central nervous system, TRQ moderately potentiated the actions of hexobarbital (sleeping time) and methamphetamine (stereotyped behavior) at doses above 100 mg/kg, p.o. TRQ, however, had little influence on behavioral changes, EEG and motor function. TRQ only had slight influence on the respiratory and cardiovascular system at doses ranging from 0.1 to 3 mg/kg, i.v. Significant decrease in SBP and increases of HR, FAF and respiratory rate were observed after high doses (10-30 mg/kg, i.v.) of TRQ. TRQ also had little influence on contractility and pacemaker in isolated hearts, but moderately increased the coronary flow. The inhibitory effect of TRQ on the isolated smooth muscle was observed at high concentration and was non-specific. Furthermore, TRQ exhibited little influence on the autonomic nervous system. Among the effects of TRQ on the gastrointestinal system, it was shown that TRQ moderately increased the outflow of bile after doses above 1 mg/kg, i.v. TRQ also showed no remarkable actions on other aspects of the gastrointestinal system and blood coagulation system. Considering the present results, it may be suggested that there should be no serious problems in the application of TRQ as a hepatoprotective agent.

Animals↗
PubMed1982

[Effectiveness of CT in the diagnosis and therapy of malignant thoracic cancer].

Since 1975 computed tomography (CT) has become available for the study of the body. In the thorax CT proves to be valuable to evaluate the lesions of the mediastinum, pleura and chest wall. However, the great difference in attenuation between air-filled lung and other soft tissue structures contributes greatly to the success of conventional diagnostic modalities, i.e. plain chest radiography and conventional tomography in the diagnosis and evaluation of the mass lesions in the lung parenchyma. And the role of CT is less valuable than in the other areas. However, CT is useful to diagnose and evaluate the chest wall or mediastinal invasion as well as mediastinal lymph node involvement. In radiotherapeutic managements of the malignancies in the thorax CT is valuable for the definition of the target volume and physical dose planning because CT provides information on patient outline and other internal structures of interest in addition to the size and shape of the tumor. CT is useful to estimate the efficacy of the conservative treatment, such as chemotherapy or radiotherapy for the thoracic malignancies, especially those in the mediastinum and chest wall. During follow-up study of the pulmonary malignancy conventional radiographic techniques may not be as valuable as before treatment because there is great change of the pulmonary architecture due to fibrosis and/or atelectasis secondary to the treatment. And CT may give valuable information in such cases.

Humans↗