Biomedical subjects

M X Jiang

Publications and source records attributed to M X Jiang.

At least 37 records · Page 2Linked to original sources

PubMed1990

[Effects of benzyltetrahydropalmatine on ischemia reperfusion with monophasic action potential].

The changes of monophasic action potential (MAP) in ischemic and reperfused feline ventricle in situ were studied. When the feline coronary artery was ligated the MAPD50 was found to be markedly shortened, the T wave and S-T segment were elevated evidently. Within seconds of releasing the coronary occlusion ventricular fibrillation and death occurred in all animals. Intravenous injection of BTHP markedly prolonged the MAPD50 and MAPD90 and reduced the heart rate, while no influence on T wave and S-T segment were observed. After occlusion of the coronary artery, the T wave and S-T segment only increased slightly and the MAPD50 recovered to its control level. During reperfusion the occurrence of ventricular fibrillation was significantly reduced. In contrast, prazosin, verapamil and propranolol did not show significant effect on changes of MAP, but BTHP and Pra, Ver and Pro all showed protective effect on feline ischemic and reperfused myocardia by ligation and reperfusion of the coronary artery with decrease of the number of arrhythmia, ventricular fibrillation and death. The order of antiarrhythmic action of these agents was BTHP = Pra greater than Ver greater than Pro. The total incidence of ventricular fibrillation reduced from the control values of 100% in ischemia/reperfusion heart to 0% (BTHP and Pra), 20% (Ver) and 40% (Pro).

Action Potentials↗

PubMed1989

Blocking action of berberine on various receptors in rat anococcygeus muscle.

The contractile responses of rat anococcygeus muscle to phenylephrine, acetylcholine and 5-hydroxytryptamine in relation to berberine and to their specific antagonists were studied separately. The effects of phenylephrine and acetylcholine were blocked by berberine as well as by atropine. But the alpha-blocking action of atropine was exhibited only at high concentration. The anococcygeus muscle response to phenylephrine was competitively inhibited by berberine with a PA2 value of 6.4. The contraction induced by acetylcholine was competitively inhibited by atropine (PA2 = 8.7), whereas berberine, which differs basically from atropine, shifted the dose-response curve for acetylcholine non-parallelly to the right with its maximal response reduced concomitantly. Its pD2(1) value was 4.6. This suggests that the antagonistic action of berberine may be exerted non-specifically through a site beyond the M-cholinergic receptor. Berberine also relaxed the contraction of anococcygeus muscle induced by 5-hydroxytryptamine. The contractile responses to histamine and isoprenaline were seen only at high concentration. In addition, the response to isoprenaline was little affected by propranolol in our experiment.

Acetylcholine↗

PubMed1989

Studies on the calcium antagonistic action of tetrandrine: X VI. Hemodynamic effects of tetrandrine on conscious rats.

Hemodynamic study of tetrandrine (Tet) in conscious rats showed that 15 mg/kg i.v. lowered BP, LVSP, +/- dp/dtmax, and (dP/dt)P-1. The degree of diminutions was nearly equal to that of BP during the initial period, while the LVEDP was elevated. But all these parameters (except -dp/dtmax) recovered gradually and earlier than BP, and LVEDP decreased to a level slightly lower than that of control. These results indicate that the hypotensive action of Tet is mainly due to its inhibition of cardiac contractility at the early period, but due to vasodilatation in the later stage. The HR was slowed down abruptly followed by a reflex acceleration, and than a gradual but sustained decrease in HR supervened with i.v. Tet. When large dose (40 mg/kg) of Tet i.v. caused a cardiac standstill with the R wave of ECG persisting for a few minutes, it means that an excitation-contraction decoupling occurred as that found on isolated myocardial preparation treated with verapamil and Tet.

Alkaloids↗

PubMed1989

[Effects of 7-bromoethoxybenzene-tetrahydro-palmatine on isolated working guinea pig heart].

The effective period of isolated working guinea pig heart perfused with Tris-sodium-pyruvate solution (Tris-SP) was shown to be 70 min. Perfluorotributylamine at a concentration of 0.5% added to Tris-SP prolonged the effective time to 90 min. 7-Bromoethyoxybenzene-tetrahydropalmatine (EBP) 10 mumol/L, and prazosin 0.1 mumol/L showed no obvious influence on the parameters in the isolated working guinea pig heart. Methoxamine 1 mumol/L and dopamine 1 mumol/L produced marked changes on LVP, ABF, +/- dp/dtmax and T-CO. It is suggested that the alpha 1-adrenoceptor was partially associated with the positive chronotropic action of the heart. Effects of methoxamine and dopamine on the parameters were antagonized by EBP. It shows that the antagonistic affects of EBP on methoxamine and dopamine are concerned with its antagonistic effect on alpha 1-adrenoceptor and dopamine receptor. This is consistent with previous results in rabbit aortic strips and rat anococcygeus muscles.

Alkaloids↗

PubMed1988