摘要:

The methods published for fabrication of double‐barrelled ion‐selective micro‐electrodes are often difficult to follow and give inconsistent results. We describe here a new improved way of making double‐barrelled ion‐selective micro‐electrodes from theta‐style glass capillaries that offers several refinements which improve reproducibility: (1) good control of silanization and (2) dry‐bevelling to assure no inter‐barrel silane contamination and to minimize the signal‐to‐noise ratio by increasing the tip diameter, without compromising the

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.00178.x

出版商:Blackwell Science Ltd.    

年代:1997

数据来源: WILEY

摘要:

We investigated the effects of hydralazine on renal sympathetic nerve activity in anaesthetized heart failure rats. Sham‐operated rats (group 1) received 0.5 mg kg−1of hydralazine as bolus and were then infused with 0.3–0.5 mg kg−1 h−1for 3 h intravenously. Heart failure rats received either the same regime (group 2) as group 1, or the same volume of vehicle (group 3). Heart failure rats exhibited lower mean blood pressure (P<0.05) and elevated renal sympathetic nerve activity (P<0.01) in the basal state. In group 2, the mean blood pressure decreased 26% after 30 min of hydralazine administration and remained lower for 3 h, with unchanged renal sympathetic nerve activity. In group 1, the mean blood pressure decreased 36%, and the heart rate and renal sympathetic nerve activity were significantly inhibited. Bilateral vagotomy did not alter renal sympathetic nerve response to hydralazine, but resulted in tachycardia. The results indicate that hydralazine, despite its profound hypotensive effect, did not activate renal sympathetic nerve activity in heart failure rats and inhibited renal sympathetic nerve activity in sham‐operated rats. This inhibition was not media

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.00151.x

出版商:Blackwell Science Ltd.    

年代:1997

数据来源: WILEY

摘要:

The present study was designed to identify an interaction between the renin–angiotensin system and noradrenergic transmission in the human heart. It is still under debate whether angiotensin II facilitates noradrenaline release in the heart. Clinical studies of congestive heart failure, involving systemic angiotensin‐converting enzyme (ACE) inhibitor administration, have indicated anti‐adrenergic effects, without giving a clear mechanistic picture. The influence on cardiac sympathetic transmission by local intracardiac administration of an ACE inhibitor has not been determined. Seven angina patients with normal left ventricular function, who underwent control coronary angiography after successful percutaneous transluminal coronary angioplasty were studied. Baseline measurements of haemodynamics and total and cardiac noradrenaline spillover were followed by handgrip exercise in the absence and presence of intracoronary enalaprilat infusion (0.05 mg min−1, 1 mL min−1). Baseline total body and cardiac noradrenaline spillover remained unchanged following intracoronary enalaprilat infusion, being 3745 ± 349 and 3896 ± 257 pmol min−1, and 148 ± 56 and 149 ± 55 pmol min−1, before and after drug administration, respectively. Mean arterial pressure, peripheral plasma renin activity and angiotensin II levels were also unaffected by enalaprilat infusion. During handgrip exercise procedures, both total body and cardiac noradrenaline spillover increased substantially, showing no reduction in the presence of intracardiac enalaprilat.Direct administration of the ACE inhibitor enalaprilat to the human heart failed to attenuate cardiac sympathetic drive during baseline conditions or following cardiac adrenergic activation by handgrip exercise. Thus, in the non‐failing heart, without chronic adrenergic activation, no angiotensin II‐facilitated effect

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.00199.x

出版商:Blackwell Science Ltd.    

年代:1997

数据来源: WILEY

摘要:

The aim of this study was to determine the MHC profile of regenerated soleus muscles in control (C,n = 8) and hindlimb suspended rats (HS,n = 8). After muscle degeneration was induced by injection of snake venom containing notexin, male rats were either tail suspended for 21 days or submitted to normal weight‐bearing activity. Separation and detection of MHCs by sodium dodecyl sulphate–polyarcylamide gel electrophoresis (SDS–PAGE) showed that regenerated soleus muscles from C rats contained only type I and type IIa MHCs. The relative amount of type I MHC was higher in regenerated (93.9 ± 1.7%) than in untreated muscles (86.5 ± 2.3%) (P < 0.01). In the HS group, the immunohistochemical analysis showed that the majority of regenerated myofibres reacted positively with the antibody against fast MHCs. SDS–PAGE analysis demonstrated that HS resulted in a shift toward faster MHCs in both intact and regenerated myofibres. Regenerated soleus muscle from HS rats contained ≈34% type IIa MHC, ≈37% type IIx/d MHC and ≈18% type IIb MHC, when type I MHC contributed to only ≈12% of total myosin. The proportions of fast MHC isoforms in regenerated muscles were higher than those recorded in untreated muscles. Collectively, these results suggest that the shift in the MHC profile associated with hindlimb unweighting in adult undamaged soleus muscles is also related to

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.00193.x

出版商:Blackwell Science Ltd.    

年代:1997

数据来源: WILEY

摘要:

The effect of physical conditioning on skeletal muscle of individuals with spinal cord injuries (SCI) has been investigated. The anterior portion of the deltoid muscle (active in wheel‐chair propulsion) of untrained and endurance‐trained paraplegics and tetraplegics, as well as that of untrained able‐bodied subjects, was studied. The characterization involved fibre type distribution, capillarization, fibre areas and also oxidative and glycolytic enzyme levels. A general trend towards a successively higher proportion of type I fibres and lower proportion of type IIB fibres was noted in the order of able‐bodied subjects (type I, 42%; type IIB, 41%,n=8), paraplegics (type I, 57%; type IIB, 13%,n=13) and tetraplegics (type I, 74%; type IIB, 4.5%,n=11). The trained SCI groups had significantly higher levels of the citric acid cycle marker enzyme citrate synthase (34% and 63%) than the untrained SCI groups and able‐bodied subjects, respectively. The glycolytic marker enzyme 6‐phosphofructokinase was 32% lower in the tetraplegic groups than in the other groups. In contrast, the fatty acid oxidation marker enzyme 3‐hydroxyacyl‐CoA dehydrogenase was markedly higher in the tetraplegic group than in the able‐bodied subjects (58%) and tended to be higher (21%,P<0.1) than in the paraplegic group. The trained SCI groups displayed significantly higher (28%) levels of capillaries per fibre than the untrained SCI groups, which had about the same levels as the untrained able‐bodied subjects. It is concluded that several of the findings are in line with normal muscular adaptation, whereas others are unexpected and support a hypothesis that some of the findings might be due to differences between the groups in, for instance, hormone levels or in typ

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.201371000.x

出版商:Blackwell Science    

年代:1997

数据来源: WILEY

摘要:

Vasoconstrictor effects of noradrenaline were compared in 6‐ to 7‐month‐old spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats. A cylindrical segment was dissected from the proximal part of tail artery, cannulated at both ends and perfused alternately either at constant flow or constant pressure. Two series of experiments were performed. In the first series, vessels were perfused/superfused with Krebs‐Henseleit solution. In the second one a modified salt solution was used, in which NaCl was totally replaced by an equimolar amount of KCl. Under constant flow conditions noradrenaline evoked a more prominent resistance increase in SHR compared with WKY independently of the composition of solution (normal or high‐K+) used. At constant pressure perfusion with normal solution, the vasoconstrictor response to noradrenaline was more prominent in WKY. Under application of high‐K+solution, vasoconstriction at constant pressure in SHR became more pronounced than that in WKY. We suggest that there is greater wall thickness:lumen diameter ratio in SHR vessels and thus different contribution of distension‐activated myogenic response is of primary importance for the

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.00182.x

出版商:Blackwell Science Ltd.    

年代:1997

数据来源: WILEY

摘要:

New Zealand male rabbits were anaesthetized with thiopental, tracheotomized, curarized by vecuronium bromide and mechanically ventilated. Six rabbits receivedL‐NAME 10 mg kg−1i.v., six rabbitsL‐NAME 15 mg kg−1iv, and six rabbits received saline i.v. (controls), 5 min before a histamine aerosol (2% solution during 5 min). Six others rabbits received an injection ofL‐NAME 15 mg kg−1iv, 5 min before the histamine aerosol, followed by an infusion ofL‐arginine over a 60‐ min period. Total respiratory resistance (Rrs) and elastance (Ers) were derived by least square analysis of the relationship between tracheal pressure and flow, and computed every minute before and over a 1‐h period after the histamine aerosol. Oxygen free radicals (OFR) were measured with a luminometer, in microsomes from lung homogenates at the end of the experiment. Compared with the histamine response of the control group, the Rrs response in theL‐NAME 10 group was slightly less, while Ers changes were the same in the two groups. In contrast,L‐NAME 15 was responsible for an increased Rrs response, the difference being significant (P < 0.05) only between 15 and 40 min after the aerosol (+114% vs. + 85% in controls at the 20th min). The increase in Ers withL‐NAME 15 was stronger and significantly larger (+71% vs. +42% in controls at the 20th min after the histamine aerosol,P < 0.001). The relatively greater effect ofL‐NAME on Ers than on Rrs suggests that NO predominantly modulates the response to histamine of the peripheral lung rather than that of the large airways. Furthermore, the effect ofL‐NAME on Rrs was completely abolished byL‐arginine, while its effect on Ers was only partially reversed. This suggests that the changes in Ers are partly related to a hardly reversible phenomenon. Possibly, the mechanical changes are linked with the rise of OFR in the lung parenchyma, which were significantly higher in theL

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.00180.x

出版商:Blackwell Science Ltd.    

年代:1997

数据来源: WILEY

摘要:

The effect of a new nitric oxide (NO) donor, a meso‐ionic 3‐aryl substituted oxatriazole‐5‐imine derivative, GEA 3162 was studied on constant flow‐perfused ischaemic Langendorff rat heart. The perfusion was kept constant at a rate of 16 mL min−1. Ischaemia was induced by a low flow rate of 0.8 mL min−1for 30 min, and was followed by a 40‐minute reperfusion. In the first set of experiments the effects of GEA 3162‐infusion were examined on perfusion pressure, left ventricular pressure, heart rate and left ventricular dP/dt. GEA 3162 infusion did not affect the pre‐ischaemic maximum of left ventricular pressure. During reperfusion, maximal left ventricular pressure, maximal and minimal dP/dt values in the GEA 3162‐treated group significantly exceeded those of the untreated controls (by 19.3, 36.0 and 18.0%, respectively). During reperfusion, perfusion pressure increased continuously in the control group indicating an increasing coronary resistance, but it was kept at a continuous low level with GEA 3162 treatment. In a second set of experiments bradykinin was infused in order to test the endothelial function before ischaemia and during late reperfusion. Bradykinin elicited significant vasodilation in the control group during reperfusion, meanwhile it did not cause further change in coronary resistance in the GEA 3162‐infused group. We suggest, that GEA 3162 may have a protective effect on isolated rat heart in ischaemia and reperfusion, that results in an improved cardiac performance c

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.00196.x

出版商:Blackwell Science Ltd.    

年代:1997

数据来源: WILEY

摘要:

The effects of long‐term altitude training on altitude and sea‐level physiological characteristics in elite endurance athletes were investigated. Seven Swedish elite cross‐country skiers (five men, two women; mean age 27 years) spent 1 month training at 1900 m above sea level in Italy. Rollerski treadmill tests were performed before and 5 and 11 days after the altitude sojourn; three tests were also performed at altitude. Before and 1, 11 and 35 days after the altitude camp, echocardiographic and blood volume measurements were performed. The heart rates at both maximal (P < 0.05) and submaximal (P < 0.01) work loads were decreased by 5–9 beats min−1at altitude. The haemoglobin concentration and haematocrit increased quickly at altitude with a corresponding decrease on return to sea level. The blood volume (7%) and total haemoglobin (3%) tended to be higher day 11 post‐altitude (NS). There were no significant changes in diastolic internal diameter or wall thickness of the left ventricle, but the calculated cardiac left ventricular muscle mass was increased post‐altitude (9–10%,P < 0.01). The maximal oxygen uptake increased in six of the seven skiers after the altitude training (day 11, mean 3%, NS). In conclusion, training at moderate altitude may cause a reduction in heart rates during exercise. Moreover, after long‐term training at altitude, there may be an increase in the car

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.00204.x

出版商:Blackwell Science Ltd.    

年代:1997

数据来源: WILEY

摘要:

Head‐down tilted bedrest is a ground‐based microgravity simulation model. Since in this position the influence of chief external determinants of circadian blood pressure variation, i.e. activity and posture, are reduced, it may reveal endogenous oscillatory factors. The effects of 42 days of 6° head‐down tilt on the circadian profiles of continuous finger blood pressure, heart rate, stroke volume, cardiac output and total peripheral resistance were analysed. In seven healthy volunteers (25–31 years) twelve 22 h Portapres registrations were performed: two in an ambulatory baseline period, eight during 42 days of head‐down tilt, and two during recovery. Stroke volume was estimated by a pulse contour method (`Modelflow') from the finger arterial blood pressure tracing. Head‐down tilt rapidly reduced circadian BP variation, especially for diastolic blood pressure. No effect of long‐term head‐down tilt on blood pressure level was observed. The day‐night difference in heart rate was essentially unaffected. Cardiac output was maintained through an increase of heart rate and simultaneous decline of stroke volume. Our observations confirm the overriding importance of physical activity and orthostatic load on the diurnal variation of BP. The time‐frame of the changes in stroke volume and heart rate during head‐down tilt might point to a contribution of other factors besides a reduction of circulating blood volume affecting cardiovascular performanc

ISSN:0001-6772    

DOI:10.1046/j.1365-201X.1997.00203.x

出版商:Blackwell Science Ltd.    

年代:1997

数据来源: WILEY