2型糖尿病血管病变时血浆ANP、BNP及CNP的变化及临床意义

目的：探讨血浆心钠素(ANP)、脑利钠肽(BNP)、C型利钠肽(CNP)在2型糖尿病血管病变时的变化及其临床意义。方法:应用酶联免疫吸附法(ELISA)测定正常对照组(9例)、2型糖尿病无血管病变组(34例)及2型糖尿病血管病变组(23例)血浆proANP、BNP fragment及NT-proCNP浓度，分析各组间血浆利钠肽水平的变化及相关因素。结果:2型糖尿病血管病变组血浆ANP、BNP明显高于另外2组（P<0.01），而血浆CNP明显降低（P<0.01），2型糖尿病血管病变组各亚组(微血管病变组、大血管病变组及微血管合并大血管病变组)间血浆利钠肽水平无明显差异（P>0.05）。2型糖尿病血管病变组血浆ANP与BNP间存在显著正相关（r=0.309, P<0.05），ANP与CNP（r=-0.374, P<0.05）以及BNP与CNP（r=-0.653, P<0.01）间存在显著负相关。结论:血浆ANP、BNP及CNP的联合检测可以作为简便、价廉、可靠的糖尿病血管病变的筛选指标。     

继发孔型房间隔缺损介入治疗及其疗效评价

目的：评价双盘封堵器介入治疗继发孔型房间隔缺损(ASD)的临床疗效及安全性。方法：在X线透视和经食道超声心动图(TEE；13岁以下儿童经胸超声心动图，TTE)监视下，采用经皮穿刺放置封堵器方法治疗继发孔型ASD16例，术后立刻、24h、1月、3月进行TEE或TTE和X线胸片检查，以评价其疗效。结果：本组16例封堵器置入均获成功。其中9例术后胸闷症状立即消失，第2天即能下床活动，无特殊不适主诉；另7例症状任2周后逐渐好转。1例术后仍有微量分流，3个月后分流才消失；术后1个月有8例右房及右室内径较术前缩小。14例术后3个月TTE显示ASD无残余分流，封堵器位置良好；另2例失访。结论：经皮封堵治疗继发孔型ASD，是一种有效的介入治疗方法，具有安全、有效、操作简便，成功率高的特点。     

Spontaneous arterial baroreflex control of the heart rate during head-down tilt in heat-stressed humans

The purpose of this study was to elucidate the effect of raised body temperature per se during acute heat stress on the spontaneous arterial baroreflex control of heart rate (f _c) in humans. To investigate whether unloading of cardiopulmonary baroreceptors during whole-body heating would alter the arterial baroreflex control of f _c, we controlled loading of the cardiopulmonary baroreceptors by head-down tilt (HDT) at angles of 5°, 10°, 15°, and 30° during heat stress produced by hot-water-perfused suits. The sensitivity of the arterial baroreceptor-cardiac reflex was calculated from the spontaneous changes in beat-to-beat arterial pressure and f _c. As an index of cardiopulmonary baroreceptor loading, the left atrial diameter (LAD) was measured by echocardiography. During whole-body heating, the LAD decreased with the rising body core temperature and increased with the HDT. The decreased LAD during heating almost recovered to the normothermic control level by 10° HDT. In the supine position, cardiac baroreflex sensitivity remained unchanged during heating. Arterial pressure, f _c and cardiac baroreflex sensitivity were not changed by HDT ranging from 5° to 30° during heating. These results suggest that cardiac baroreflex sensitivity remain unchanged during graded loading of the cardiopulmonary baroreceptors in heat-stressed humans. Also, we conclude that the sensitivity of the spontaneous arterial baroreflex controlling the f _c is not influenced by raised body temperature per se during acute heat stress. Electronic Publication     

Hormone changes induced by 37.5-h head-down tilt (−6°) in humans

Endocrine regulation of hormones and electrolytes during 37.5 h of –6° head down tilt (HDT) was studied in 13 men. The acute effects of simulated weightlessness are today well documented, but no study has been made concerning the hormone changes between 12 h and 2 days of HDT. Plasma volume showed a maximal increase of 9.23 (SEM 1.97) % after 6.5 h (P<0.01) and had returned to prestudy levels after 13.5 h of HDT. From 1.5 h to 4 h of HDT, C-terminus and N-terminus atrial natriuretic peptide (ANP) concentrations in plasma were increased by about 50% (P<0.01) and thereafter declined to pre-HDT levels. Plasma renin activity (PRA) was decreased by 47% (P<0.05) after 4 h of HDT; PRA increased after 23.5 h to 60%; noradrenaline concentration decreased immediately and remained low up to 37.5 h. Diuresis and natriuresis were evident during the 1st day of HDT, resulting in a marked increase in the urinary Na⁺. These results showed that the initial hormone (ANP, PRA) changes during HDT did not last more than 13.5 h and that after 24 h a new state would seem to have been established to adapt the body to hypovolaemia.     

Large left atrial myxoma presented as fever of unknown origin: a challenging diagnosis and a review of the literature

Myxoma is the most common type of primary tumors of the heart in adults. The majority of patients with myxomas may experience symptoms due to central or peripheral embolism or intracardiac obstruction, while in some cases, they may be completely asymptomatic. Rarely, patients develop unusual symptoms that complicate the diagnostic evaluation. Herein, we describe the case of a 70-year-old patient with a long-lasting low-grade fever due to a large left atrial myxoma revealed during a transthoracic echocardiography.     

Development of immunoreactive atrial natriuretic peptide in fetal hearts of spontaneously hypertensive and Wistar-Kyoto rats

Summary The development of immunoreactive atrial natriuretic peptide (ANP) was studied in fetal hearts of spontaneously hypertensive (SHR) and compared to normotensive Wistar-Kyoto (WKY) rats. While SHR fetal hearts were noticeably less developed than those of WKY at 10 and 11 days gestation, both strains showed ANP immunoreactive cells in some but not all primitive heart tubes. At 12 days additional ANP immunoreactive cells appeared in formative trabeculae of the ventricle and atrium. ANP cells were also observed in the myogenic layer of the truncus and bulbus arteriosus and their derivatives from 11 through 16 days, but not at 18 days. In both strains, there were more ANP cells in the left ventricle than in right beginning at day 13. There were no obvious strain differences in the developmental pattern and timing of ANP producing cells. However, on the day of birth, staining was reduced in hearts from some WKY newborn pups compared with hearts from SHR newborns and ventricular staining was reduced in both strains when compared to fetal hearts. These observations indicate that ANP is one of the earliest peptide hormones produced and that the predisposition to genetic hypertension does not appear to influence the development of ANP.     

Action of ANG II and ANP on colon epithelial cells

The interaction of angiotensin II (ANG II) and atrial natriuretic peptide (ANP) on intracellular pH (pH_i) and calcium ([Ca²⁺]_i) was investigated in T84 cells (a permanent cell line derived from human colon epithelium) using the fluorescent stains BCECF/AM and Fluo 4/AM, respectively. pH_i recovery rate mediated by the Na⁺/H⁺ exchanger (NHE) was examined following an NH₄Cl pulse. Under control conditions pH_i recovered at 0.114±0.005 pH units/min (n=35). ANG II (10^–12 or 10^–9 M) increased this value, whilst ANG II (10^–7 M) decreased it. These effects of ANG II were impaired by simultaneous addition of 1 M or 25 M HOE-694, indicating that the stimulatory and inhibitory effects of ANG II on pH_i recovery are mediated in part via the NHE1 and NHE2 isoforms. ANG II increased [Ca²⁺]_i concentration-dependently. ANP (10^–6 M) or dimethyl-BAPTA/AM (50 M) blocked the effects of ANG II on [Ca²⁺]_i and on the rate of pH_i recovery. Thapsigargin (10^–5 M) enhanced the effect of ANG II on [Ca²⁺]_i and reversed its stimulatory effect on the rate of pH_i recovery to an inhibitory one. External Ca²⁺-free solution did not affect the effects of ANG II on these parameters. These data suggest that the [Ca²⁺]_i increase induced by ANG II is dependent on intracellular calcium stores. They are compatible with the demonstration of two sites on the C-terminal of the Na⁺/H⁺ exchanger, one stimulating Na⁺/H⁺ activity by increases of [Ca²⁺]_i in the lower range (at 10^–12 or 10^–9 M ANG II) and the other inhibiting this activity at high [Ca²⁺]_i levels (at 10^–7 M ANG II). ANP or dimethyl-BAPTA/AM, by impairing the pathway mediating the increase in [Ca²⁺]_i, block both the stimulatory and inhibitory effects of ANG II.     

Atrial fibrillation: a new explanation of the old phenomenon

We propose a new mechanism of atrial fibrillation basing on the results of 30 series of acute experiments on anesthetized cats. In brief, combination of two or more arrhythmogenic factors shortens the interval between the inward and outward ionic currents in cardiomyocytes to a critical value. Under these conditions repolarization of cardiomyocyte membrane reaches the excitation threshold before complete inactivation of the depolarizing currents. This inevitably results in autoexcitation of myocytes (or extrasystole), that in turn promotes repolarization. Once occurred, autoexcitation turns into self-triggering activity resembling tachyarrhythmia paroxysm.     

Atrial natriuretic peptide in human urine

Summary A highly sensitive radioimmunoassay to measure atrial natriuretic peptide (ANP) concentration in urine has been established, and its clinical usefulness is presented. ANP in urine was stable at 4° C for several days and was easily measured by our radioimmunoassay. The average ANP excretion in 65 healthy persons was 25.0±1.4 ng/day (mean ± SEM) and the fractional excretion of ANP was 0.7±0.05%. In 14 patients with congestive heart failure, the average ANP excretion was 119.2±29.4 ng/day, which decreased to 53.3±11.0 after successful treatment.Abbreviations ANP atrial natriuretic peptide - hANP human atrial natriuretic peptide - RIA radioimmunoasay - NSB non specific bound - FE_ANP the fractional excretion of atrial natriuretic peptide - FE_Na the fractional excretion of sodium - SIADH the syngrome of inappropriate secretion of antidiuretic hormone     

非接触标测和频谱分析迷走神经介导的心房颤动

目的： 对在体犬迷走神经介导的心房颤动（房颤）进行非接触标测和频谱分析，以探讨其发生和维持机制。方法: 测定8只犬基础情况及双侧迷走神经刺激时心房有效不应期及其离散度，非接触标测和频谱分析房颤时左、右房的电活动。结果: 迷走神经刺激与基础情况相比，左、右心房有效不应期缩短，但有效不应期离散度增大仅见于左房。迷走神经刺激时房颤易诱发和维持，房颤显示反复有序的激动经优先传导路径传播仅见于左房；频谱分析显示左房的主导频谱高于右房［（12.5±1.5)Hz vs (9.3 ±1.2) Hz，P<0.05］。停止迷走神经刺激，左、右房房颤频谱降低［（9.2±0.5)Hz vs (8.5±0.6)Hz， P>0.05］，房颤自发终止。结论: 左、右房电生理特性改变、激动模式差异以及频谱梯度提示迷走神经介导的房颤发生和维持依赖于左房。