人心房肌细胞特殊颗粒的电镜酶细胞化学和免疫电镜研究

本研究应用电镜CMP酶细胞化学和心钠素免疫电镜胶体金,分别标记人心房肌细胞中初级溶酶体和心钠素,进行鉴别定位观察和定量分析。心钠素颗粒数量居多,占78.7～79.3％,大小均一,直径0.20±0.05μm(x±s),分布于整个细胞质内,多成簇,尤以肌膜下,核极区多见。而溶酶体大小不一,直径0.30±0.19μm(x±s),显著大于心钠素颗粒(P<0.001),一般在核极区成簇分布,也见肌原纤维之间和肌膜下单个散在分布。     

Metabolic depression and myocardial potassium

Summary The action potential duration (APD) of guinea pig atrial muscle responded qualitatively to metabolic depression and altered glucose concentration as shown previously for papillary muscle. Both preparations lost potassium and gained sodium during 8 h anoxic incubations and these changes were partially prevented by 50 mM glucose. Experiments with potassium⁴² indicated that anoxia-induced loss of potassium was not primarily due to an increased efflux but to a decreased influx. Stimulation did not increase potassium⁴² efflux from atria but caused some increase in potassium loss. The ATP content of atria and ventricular muscle decreased rapidly during anoxic incubation but was maintained at a significantly higher level in the presence of 50 mM glucose. Since muscle potassium levels following 8 h of anoxic incubation were incompatible with observed resting potentials, the results support the concept of either an electrogenic sodium pump or the intracellular compartmentalization of potassium. In addition, the anoxia-induced reduction of action potential duration does not appear to be associated with an increase in potassium⁴² efflux.This work was supported by grants from the Medical Research Council of Canada and the Canadian Heart Foundation.     

Age-related reductions in rat atrial high affinity choline uptake, ACh synthesis, and ACh release. A brief note

We have developed a rat atrial mince preparation that can take up choline, acetylate it, and then release acetylcholine in a depolarization-dependent manner. We demonstrate that aging appears to reduce the functional cholinergic activity in this tissue, which may be important for understanding how senescence alters the regulation of cardiac activity.     

Assessment of the left atrial volume index and plasma NT-proANP level in patients with acute ST-elevation myocardial infarction

OBJECTIVES:

Acute ST-elevation myocardial infarction is associated with ventricular dysfunction due to ischemia-induced progressive myocardial damage. The decrease in ventricular compliance causes left atrial dilatation and stretching of the atrial myocardium, which are the main stimuli for the secretion of atrial natriuretic peptide. The aim of this study was to evaluate left atrial dimensions and atrial natriuretic peptide levels in patients early after their first acute ST-elevation myocardial infarction and assess the probable interaction between coronary lesions and these measurements.

METHODS:

A total of 110 patients with acute myocardial infarction and 50 controls were studied. Plasma atrial natriuretic peptide was measured at admission. Left ventricular function, diameter, and volume index were evaluated using transthoracic echocardiography. Gensini and vessel scores of the patients who underwent coronary angiography were calculated.

RESULTS:

Plasma atrial natriuretic peptide in the patients with myocardial infarction was increased compared with that in controls (3.90±3.75 vs. 1.35±0.72 nmol/L, p<0.001). Although the left atrial diameter was comparable in patients and controls, the left atrial volume index was increased in patients with acute myocardial infarction (26.5±7.1 vs. 21.3±4.9 mL/m², p<0.01). Multivariate regression analysis showed a strong independent correlation between the left atrial volume index and the plasma atrial natriuretic peptide level (β = 0.23, p = 0.03).

CONCLUSIONS:

The left atrial volume index and plasma atrial natriuretic peptide level were correlated in patients with acute myocardial infarction.     

螺内酯对慢性心力衰竭患者胶原代谢和心功能的影响

目的观察螺内酯对慢性心力衰竭(CHF)患者心肌细胞外基质及心功能的影响。方法将84例CHF患者随机分为常规组(40例)和螺内酯组(44例)(螺内酯40mg/d)。测定两组治疗前及治疗后3、6个月血清Ⅲ型前胶原(PCⅢ)、Ⅳ型胶原(CⅣ)、透明质酸(HA)及醛固酮(Aldo)水平;同时超声心动图测定左心室功能参数。结果①两组患者治疗后细胞外基质含量下降,螺内酯组PCⅢ及CⅣ低于常规组(P<0.05,P<0.01)。②两组血清Aldo3个月后均下降(P<0.05),6个月时回升至治疗前水平,螺内酯组高于常规组(P<0.05)。③两组左室射血分数(LVEF)及VE/VA升高,以螺内酯组明显(P<0.05)。④血清PCⅢ、CⅣ、HA与LVEF呈负相关(P<0.05)。结论螺内酯可抑制心肌细胞外基质重塑,改善心功能。     

Changes in the sensitivity to cholinomimetic drugs of smooth and cardiac muscle in the rat induced by subacute administration of di-isopropyl phosphorofluoridate

The effect of subacute administration to rats of di-isopropyl phosphorofluoridate (DFP) on the sensitivity of the cardiovascular system to carbachol and on the sensitivity of various isolated tissues to acetylcholine, methacholine and carbachol was investigated. Cholinesterase inhibition produced by DFP in the isolated tissues was also determined.In the cardiovascular experiments both the magnitude of responses and the slope of the dose-response curves for hypotension and bradycardia produced by carbachol in the anaesthetized rat were reduced in the DFP-treated group.In experiments with isolated tissuesfrom DFP-treated animals it was found that sensitivity to methacholine and acetylcholine increased in the bladder to a greater extent that in the atria or ileum. The sensitivity to carbachol decreased to a similar extent in all 3 tissues. Acetylcholinesterase and butyrylcholinesterase levels in the bladder were inhibited to a greater extent than in the other 2 tissues.The results show that the degree of enzyme inhibition produced by DFP in the tissues after subacute administration for 10 days does not correlate with the decrease in the sensitivity of the tissues to carbachol. It is suggested that the association between accumulation of transmitter and enzyme inhibition is a more important factor than the degree of enzyme inhibition itself in the development of subsensitivity to carbachol.The release of cholinergic transmitter from the electrically stimulated isolated rat bladder may also be impaired following subacute administration of DFP.     

The evolution and genesis of supraventricular waltz & duet

Objective. This study documents and traces the evolution of triple rhythm (Waltz) linking the great veins, corresponding systemic or pulmonary venous sinuses and pectinated right or left atrium in frog, turtle, snake and human hearts. Alternating rhythm (duet) between systemic and pulmonary veins has also been documented in these hearts. Material Studied. The hearts of six dead hammer-head sharks were examined with the naked eye. Air-breathing, fresh-water fish (three Channa striata and three Indian catfish) were anaesthetised with ketamine and their pharynx insufflated with oxygen. Six frogs, three turtles, and two snakes were anaesthetised, intubated and ventilated. Contractions of the exposed hearts of these animals were correlated with their electrocardiograms using superimposed videos. The human heart was observed carefully during surgery through median sternotomy or anterolateral thoracotomy by visual inspection especially during instillation of or recovery from cardioplegia. Digital videos were taken and studied in slow motion replay later. Observations. In the air-breathing fish, Channa striata and Indian catfish and presumably the shark, the cardinal veins and thin walled sinus venosus do not contract. In the frog, turtle, and snake there is sequential contraction of the systemic veins, systemic venous sinus and pectinated right atrium. Likewise, there is waltz on the arterial side. There is a duet between systemic and pulmonary veins, contractions of the former preceding the latter in the frog, turtle and snake. The observations are similar in the human heart except that the inferior vena cava does not contract. Conclusions. There is sequential contraction of the superior vena cava, the systemic venous sinus and the pectinated part of the right atrium in the human heart. Likewise, there is a waltz linking the terminal pulmonary veins, pulmonary venous sinus and pectinated part of the left atrium in the human heart. This waltz or triple rhythm, as well as a duet between the systemic and pulmonary veins are seen in frog, turtle and snake. The duet is also observable in the human heart, during recovery from cardioplegia. It is likely that the waltz and duet are conducted by a neurogenic mechanism. Clinical Implications. The understanding, preservation and restoration of the mechanism sustaining supraventricular waltz and duet is relevant to surgical and interventional procedures for control of atrial arrhythmia, Fontan circulation, technique for cardiac transplantation and planning atriotomies.     

应变率成像评价冠心病患者冠状动脉支架置入术后左心房功能的变化

目的:应用应变率成像(SRI)技术评价冠心病患者冠状动脉支架置入术前、后的左心房功能的变化。方法:分别于冠状动脉支架置入术前、术后1周和术后1月应用SRI技术对28例冠心病患者左心房功能进行定量评价。结果:与术前比较,术后1周左心房收缩期前容积(LAVp)、最大左心房容积(LAVmax)、右心房被动排空分数(LAVmin)、最小左心房容积(LAPEF)、左心房射血力(AEF)及左室射血分数(LVEF)变化差异无统计学意义(P>0.05);术后1月,LAVp、LAVmax、LAVmin和AEF减小,LAPEF和LVEF增加,差异均有统计学意义(P<0.05)。与术前比较,术后1周左心房SRs、SRe和SRa差异无统计学意义(P>0.05);术后1月SRs和SRe升高,SRa降低,差异均有统计学意义(P<0.05)。结论:SRI可定量评价左心房功能,动态观察冠状动脉支架置入术前、后左心房功能的变化。     

N—[4—[2—[乙酰基[2—萘氧基]乙基]氨基]—乙基]苯甲磺酰胺对离体豚鼠心房肌的影响

目的　考察 N-[4-[2 -[乙酰基 [2 -萘氧基 ]乙基 ]氨基 ]-乙基 ]苯甲磺酰胺 (MS0 0 49)对离体豚鼠心房肌的影响对心肌电生理特性 :收缩性、自律性、兴奋性的影响 ,并初步探讨其作用机制。方法　采用离体豚鼠心房肌 ,测定 MS0 0 49对心房收缩力、心率、功能不应期、兴奋性、自律性、静息后增强及正阶梯现象的影响。结果　MS0 0 491 0 - 8～ 1 0 - 5mol/L可延长左心房功能不应期 ,降低右心房收缩性及心率。MS0 0 49(1× 1 0 - 6 mol/L)对肾上腺素诱发左心房自律性无明显影响 ,对兴奋性亦无显著影响。但可显著抑制左心房正阶梯现象及静息后增强效应。结论　 MS0 0 49可能作用于心肌钾通道 ,同时对心肌钙内流亦有非选择性的抑制作用。