VASOCONSTRICTION IN THE RENAL VASCULAR BED DURING EXERCISE: STUDIES IN CONTROL AND HEART FAILURE RABBITS

1. The effects of graded treadmill exercise on renal blood flow (RBF) were examined in seven rabbits, in which congestive heart failure (CHF) was produced by the administration of doxorubicin, 1 mg/kg, twice weekly for 8 weeks, and in seven controls. A third group of five rabbits underwent doxorubicin treatment with the addition of surgical section of the left renal sympathetic nerve. 2. During submaximal exercise, there was a small reduction in RBF in controls, which was greatly exaggerated in CHF. 3. In both control and heart failure rabbits, there was a precipitous fall in RBF as exercise fatigue developed. 4. Renal sympathectomy ablated these changes in RBF during exercise. 5. It is concluded that in heart failure there is an exaggerated, sympathetically mediated, diversion of blood flow away from the kidney. The onset of exercise fatigue in both normal and heart failure rabbits is accompanied by a marked intensification of this process.     

Risk factors for coronary heart disease among inpatients who have mild intellectual disability and mental illness

Background Coronary heart disease (CHD) is a major cause of morbidity and mortality in the UK. The aim of this study was to screen inpatients with mild or borderline intellectual disability, many of whom also have mental illness, for risk factors for CHD. Methods Cross sectional survey. Participants were interviewed, measured and had blood samples taken. Results Of the 53 participants, 20 (37.7%) were overweight and 18 (34.0%) obese. The mean body mass index (BMI) of those participants prescribed regular antipsychotics was higher than those who were not. Nine (20.9%) had waist circumference measurements placing them at increased risk of CHD and 21 (48.8%) were at substantially increased risk. Twenty-eight (52.8%) were current smokers. Of the 49 participants who had their blood pressure measured, 3 (6.1%) had readings above the reference range. Of the 19 participants who had random blood tests, one (5.3%) had an elevated cholesterol level. Conclusions In this population there was a high prevalence of two risk factors for CHD (obesity and smoking), requiring ongoing monitoring and long-term measures to reduce risk.     

猪心脏移植缺血再灌注损伤中NO和NOS的表达

①目的　了解猪同种原位心脏移植术后早期一氧化氮 (NO)、一氧化氮合酶 (NOS)含量的变化 ,及其与早期缺血再灌注损伤的关系。②方法　建立猪同种原位心脏移植模型。供心在移植前低温保存 (Thomas液 ,4℃ ) 4h ,移植成功心脏复搏后 2h取材。应用组织化学方法测定心肌组织中NO、NOS的含量 ,应用核酸原位末端标记法 (TUNEL)测定心肌细胞凋亡指数 ,作为评价心肌缺血再灌注损伤的指标。以正常心肌及单纯缺血心肌组织作为对照。③结果　移植后心肌组织NO、NOS的含量较缺血组与正常组低 ,差异有显著意义 (F =2 7.2 2 9、16 .2 0 3,q =5 .716～ 6 .4 12 ,P <0 .0 1)。移植组心肌细胞凋亡指数与正常组及缺血组比较明显升高 ,差异有显著性(F =16 3.884 ,q =7.4 82、6 .975 ,P <0 .0 1)。心肌组织NO、NOS含量与心肌细胞凋亡指数呈负相关关系 (r =- 0 .886、- 0 .795 ,P <0 .0 1)。④结论　猪心脏移植后早期心肌缺血再灌注损伤所致的细胞死亡主要表现为心肌细胞凋亡 ;再灌注期间内源性NO、NOS的减少参与了心脏移植后早期缺血再灌注损伤的发生     

Transfer of 45Ca and 36Cl at the blood-nerve barrier of the sciatic nerve in rats fed low or high calcium diets

Unidirectional fluxes of 45Ca, 36Cl, and of [3H]mannitol from blood into the sciatic nerve and cerebral cortex were determined from 5- and 15-min uptakes of these tracers after an intravenous (i.v.) bolus injection in awake rats. Rats were fed diets for 8 wk, that had either a low (0.01% wt/wt), normal (0.67%), or high (3%) Ca content. Plasma [Ca] was 32% less and 11% more in rats fed low (LOCA) and high Ca diets (HICA), respectively, than in rats fed a normal Ca diet (CONT). The mean permeability-surface area product (PA) of 45Ca at the blood-nerve barrier was about eightfold higher than at the blood-brain barrier in the same animals and did not differ significantly between groups (greater than 0.05). Mean PA ratios of 45Ca/36Cl for the blood-nerve and blood-brain barriers in CONT rats, 0.52 +/- 0.04 and 0.40 +/- 0.02, respectively, were not significantly different from corresponding ratios in LOCA and HICA groups, and corresponded to the aqueous limiting diffusion ratio (0.45). Our results show no evidence for concentration-dependent transport of Ca over a plasma [Ca] range of 0.8-1.4 mmol/liter at the blood-nerve barrier of the rat peripheral nerve, and suggest that Ca and Cl exchange slowly between nerve and blood via paracellular pathways.     

Glutamergic Action on Alpha-Melanocyte-Stimulating Hormone Release from the Rat Hypothalamus

Release of α-melanocyte-stimulating hormone (α-MSH) synthesized in the hypothalamus is regulated by monoaminergic neuronal systems. An endogenous dopaminergic system inhibits α-MSH release (1, 2) whilst serotoninergic systems exert a biphasic effect on peptide release (3). The toxic effects of neonatal peripheral administration of monosodium glutamate on hypothalamic neurons containing proopiomelanocortin- (POMC-) derived peptides (4, 5) suggest additionally the presence of glutamate receptors on or indirectly influencing the POMC neuron. By comparison of the effect of the excitatory amino-acid agonists N-methyl-D-aspartate (NMDA), quisqualate and kainate on the release of α-MSH from superfused slices of rat hypothalamus, we have demonstrated a stimulatory glutamergic action on α-MSH release mediated through NMDA-type receptors.     

Heart rate response to breathing: dependency upon breathing pattern

Summary. Heart rate responses to stepwise and periodic changes in lung volume were studied in seven young healthy males. Stepwise inspiration and expiration both resulted in an increase in heart rate followed by a rapid decrease in heart rate. The fastest heart rate was reached in 1·6 ± 0·5 s and in 3·6 ± 1·4 s in response to inspiration and expiration, respectively (P < 0·01). The slowest heart rate was reached in 4·8± 1·0 s and in 7·6± 1·9 s in response to inspiration and expiration, respectively (P < 0·01). Following this biphasic change the heart rate returned to a steady level. The difference between the fastest and the slowest heart rates was significantly larger in response to inspiration (21·7 ± 7·3 beats per minute) than in response to expiration (12·0±7·3 beats per minute; P < 0·01). Periodic changes in lung volume were performed with frequencies from 3·0 to 12·0 respirations per minute (r.p.m.). The changes in heart rate showed a constant amplitude in the frequency range below 5·5 r.p.m. Maximal heart rate changes were found at frequencies of 5·5 to 7·0 r.p.m. Changes in heart rate decreased in a linear manner on a log-log scale in the frequency range above 7·0 r.p.m. The relation between frequency and changes in heart rate is explained by interference between the transient changes in heart rate induced both by inspiration and by expiration. It is concluded that if heart rate changes in response to periodic changes in lung volume are to be used as a measure of vagal function a number of factors have to be taken into consideration and to simplify the analysis of heart rate responses to breathing we recommend, instead, the use of the transient changes in heart rate induced by stepwise changes in lung volume.     

Inadequate dietary magnesium intake increases atherosclerotic plaque development in rabbits

Epidemiological studies have shown dietary magnesium (Mg) intake and serum Mg levels to be inversely correlated with the development of atherosclerosis. We hypothesized that low levels of Mg would promote atherosclerotic plaque development in rabbits. New Zealand white rabbits (4 months old, n = 22) were fed an atherogenic diet containing 0.12% (−Mg), 0.27% (control), or 0.43% (+Mg) Mg for 8 weeks. Blood samples were obtained at baseline, 2, 4, 6, and 8 weeks and were assayed for total cholesterol, high-density lipoprotein (HDL), non-HDL, triglycerides (TG), C-reactive protein, serum Mg, and erythrocyte Mg. Aortas from −Mg had significantly more plaque, with an intima thickness 42% greater than control and 36% greater than +Mg. Serum cholesterol levels rose over time, and at 8 weeks, −Mg had the highest and +Mg the lowest total and non-HDL cholesterol and TG levels, although these results did not reach significance. Over time, serum Mg levels increased, and erythrocyte Mg levels decreased. C-reactive protein significantly increased in all groups at 4 and 6 weeks but returned to baseline levels by 8 weeks. This study supports the hypothesis that inadequate intake of Mg results in an increase in atherosclerotic plaque development in rabbits.     

成年大鼠纹状体海人藻酸损伤后nestin的表达

目的　 研究成年大鼠纹状体海人藻酸 (kainicacid,KA)损伤后不同时间点nestin的表达并探讨其机制。方法　向成年SD大鼠纹状体内立体定位注射 0 .5 μlKA(1mg/ml) ,分别于手术后第 1、3、7、14天用免疫组织化学法检测纹状体内nestin表达的变化。结果　 正常纹状体内可观察到微弱的淡染nestin样免疫活性阳性细胞 ;大鼠纹状体KA损伤后 1d ,nestin样免疫活性增强 ;第 3天nestin样免疫活性达峰值 ,nestin样免疫活性阳性细胞的胞体肥大 ,突起粗大 ,分支增加 ;此后nestin样免疫活性阳性细胞染色强度减弱 ,其胞体和突起逐渐变小变细。 结论　 成年大鼠纹状体内注射海人藻酸可诱导nestin的大量表达 ,该表达可能与脑损伤后的自身修复相关。     

Non-invasive estimation of the diastolic elastic and viscoelastic properties of the left ventricle

The present study applies a non-invasive method to the quantitative evaluation of left ventricular stiffness in normal subjects and in patients with ischaemic heart disease (IHD). We have studied 20 patients with IHD and 25 healthy subjects. The third heart sound (S3) was detectable in all patients. We have correlated the energy spectrum of S3, divided into 15 Hz bands, with a series of echocardiographic parameters. The existence of a significant correlation between the spectrum energy and the diameter and thickness of the left ventricle at the moment of S3 allowed us to explore the possibility of interpreting the origin of S3 based on a mathematical model. Our hypothesis has been that, once the left ventricle starts vibrating, it behaves as a simple physical model composed of a mass and an elastic element. To this purely elastic model one can add a factor accounting for viscosity, with a damping effect, to obtain a more complex viscoelastic model. The stiffness coefficient 'k' was computed in both models from the peak frequency of S3 and the left ventricular mass at the moment of S3. Furthermore, in the viscoelastic model, the damping element 'c' was also computed. Both parameters--k and c--were significantly increased in the group with IHD compared with the control group. Although a simplification of the vibrating system, these models make it possible to obtain non-invasively information on the characteristics of the left ventricle through the combined use of echocardiography and spectral analysis of S3.