IHC-66对犬心室肌和浦顷野纤维的电生理作用

目的:观察IHC66(3,6dimethylaminodibenzopyriodoniumofferricEDTA)对离体犬心室肌与浦顷野纤维的电生理影响。方法:采用心肌细胞内玻璃微电极技术。结果:IHC66可缩短犬心室肌动作电位复极20%和50%的时程,降低动作电位零相最大除极速率、缩短浦顷野纤维APD50。在较高浓度时,IHC66还降低犬心室肌与浦顷野纤维动作电位振幅和延长动作电位APD90。结论:IHC66对犬心室肌细胞APD20和Vmax的抑制作用明显较浦顷野纤维强,对浦顷野纤维动作电位Vmax呈现频率依赖性抑制作用。

MECHANISM OF PATHOLOGICAL CHANGES OF INTRAVENTRICULAR HEMORRHAGE IN DOGS

Objective To probe the mechanism of pathological changes of intraventricular hemorrhage(IVH). Methods The evaluation of neurological status,serial CT scans and pathological examination were applied on the canine model of IVH. The ventricular volume and blood clot volume were measured based on the CT images. Results The normal adult canine ventricle tend to be slitlike. After injection, the ventricle was obviously dilated by the blood clot. The linear regression of ventricular volume against blood clot volume was significant in the first week. From then on, however, while the clots continued to shrink, the ventricular volume showed progressive enlargement. The clots were lysed completely within 3 to 4 weeks. The linear regression of the degree of ventricular dilatation against the first clot volume was also significant. In the pathological examination, we found the ependymal lining of ventricular system was destroyed and neurons in the subependymal areas developed acidophil necrosis, which was prominent around Sylvian aqueduct. Conclusion Hemorrhagic ventricular dilatation(HVD) is a prominent feature of IVH and also is a strong indicator for poor prognosis. Ischemic changes of periventricular neurons in some important structures may be the most direct cause for poor outcome of IVH. It may be induced by periventricular vascular structures compressed by HVD, increased intracranial pressure, cerebral vasospasm and others.

Ion mechanism of isoproterenol on delayed afterdepolarization and triggered activity in the infarcted ventricle

Objectives This study aimed at investigating the cellular mechanism of isoproterenol （ISO） on delayed afterdepolarizations （DADs） and triggered activity （TA） of the noninfarcted myocardium in the myocardial infarcted rabbit model.Methods Rabbits with the left anterior descending coronary artery occlusion were prepared and recovered for 8 wk （healed myocardial infarction, HMI）. Myocytes were isolated from regions of the noninfarcted left ventricular free wall. ISO was added to cellular surface by perfusion way. Action potentials and ion currents were recorded with whole-cell patch clamp. Results The results showed that treatment with ISO induced more DADs and TA events in HMI myocytes. Iti and IC,_L of myocytes treated with ISO were increased significantly compared with HMI cells, which contributed to DADs-related triggered arrhythmia. Conclusions The results suggested that more arrhythmia events of DADs and TA developed in myocytes with ISO treatment. The underlying mechanism was associated with the augment of I6 and calcium influxing

Spontaneous Coronary Artery Dissection with Clinical Presentation of Acute Myocardial Infarction

SCAD （spontaneous coronary artery dissection） proves to be a pathology of several manifestations, whose clinical diagnosis is a challenge for emergency departments. Therefore, their early identification and knowledge of the various forms of presentation are mandatory for optimal medical therapy. We present a case report of a 45-year-old patient who was admitted to the coronary unit showing symptoms and laboratory tests compatible with myocardial infarction. Complete diagnosis was obtained only with more specific exams. The manifestations of the disease in the case described and the main features of the disease are discussed.

CHANGES OF PLASMA ENDOTHELIN AND ATRIAL NATRIURETIC PEPTIDE DURING THE ONSET AND AFTER TERMINATION OF PAROXYSMAL SUPRAVENTRICULAR TACHYCARDIA

Radioimmunoassays were used to measure the concentration changes of plasma endothelin(ET) and atrial natriuretic peptide(ANP) during the onset and after termination of paroxysmal supraventricular tachycardia(SVT). 30 cases were reviewed and compansons with 42 normal subjects were made. There are very significant differences(P<0.0001) in the concentration changes of both plasma ET and ANP during the onset and 30 minutes after the termination of SVT. During the onset period of SVT. the plasma ET and ANP were markedly elevated and 30 minutes after its termination they were lowered significantly, but their concentrations were still 2-fold higher than ihose of the control group. As the biological effects of ANP and ET are antagonistic to each other. their parallel elevation and lowering of plasma concentrations during and.after the termination of SVT reveal that these 2 hormones parucipate in the pathophysiological process of SVT. This phenomenon is possibly one of the homeostatic regulatory functions in the organism.

COMPARATIVE EFFECTS OF LOSARTAN AND CAPTOPRIL ON VENTRICULAR REMODELING AND FUNCTION AFTER MYOCARDIAL INFARCTION IN THE RAT

Objective. To determine the effects of losartan and captopril treatment on ventricular remodeling and function after myocardial infarction in rats. Methods. Thirty-two rats with MI induced by coronary ligation after seven days were divided into four groups randomly and treated with captopril(2 g. liter-1, group A), losartan(10 mg. kg-1. d-1, group B), losartan(30 mg. kg-1. d-1,group C) and placebo (no drug, group D) for six weeks, respectively. Shamoperated rats(group E)served as controls. Echocardiography was performed at 1 and 7 weeks after MI, re- spectively. Results. Compared with the results before treatment,both LV end-diastolic internal diameter and volume decreased significantly and the thickened Posterior wall was reversed in group A, B and C; the peak early filling velocity decreased whereas the peak velocity was increased in these three groups. There are no significant difference among the three treated groups. However,LV end-diastolic internal diameter and the E/A were still increased,whereas the thickness of anterior wall and the peak velocity of LV outflow were decreased in group A,B,and C after treatment comparing with group E. Conclusion. Both angiotensin converting enzyme inhibitor and angiotensin II receptor antagonist can prevent the ventricular remodeling and improve the ventricular function.

Research on FRP bolt-end failure mechanism

Given the fact that FRP bolts for roadway support are often under a certain amount of eccentric load,we studied the problems of failure of FRP bolt-ends using mechanical analysis,numerical simulation and a laboratory experiment to reveal the FRP bolt-end failure mechanism.The results show that bolt-end stress increases rapidly,making the maximum stress under an eccentric load to be 5 to 7 times greater than that under a normal load,resulting first in the formation of some fractures at the bolt-end,which then spreads to the entire cross-section of the bolt.

The Mechanisms of Flame Stabilization and Low NO_x Emission in an Eccentric Jet Pulverized Coal Combustor

The mechanisms of flame stabilization and low NO_x emission features of an eccentric jet pulverized coal com- bustor were studied through numerical modelling and experimental investigation.The results show that the formation of the unique flowfield structure is closely related to the interaction among combustor configuration, the primary jet and the control jet;and that certain rules should be followed in order to obtain the optimum condition for flame stabilization.The distributions of temperature and concentrations of NO,O_2,CO and CO_2 inside the combustor were experimentally measured.The effects of structural and operational parameters on combustion and NO formation were studied.It was found that reduction of primary air,suitable use of control jet and reasonable uptilt angle of the primary jet all contributed to the reduction of NO_x at the combustor exit. A new hypothesis,that reasonable separation of oxygen and fuel within the fuel-rich zone is beneficial to further reduction of NO_x emission,is given.The study showed that good compatibility existed between the capability of flame stabilization and low NO_x emission for this type of combustor.