摘要:

The role of endothelium‐derived nitric oxide in the regulation of vascular resistance (tonus) in cat skeletal muscle was studied with the use ofNG‐monomethyl‐l‐arginine (L‐NMMA), a specific inhibitor of nitric oxide formation from l‐arginine. The study was performed with a whole‐organ technique which permits simultaneous, continuous and quantitative recordings of resistance reactions in the whole vascular bed (R25 μm;Ra. prox) small arterioles (<25 μm; Ra,miero) and veins (Rv. NG‐monomethyl‐L‐arginine (3–100 mg kg‐1tissue, i.a.) induced a dose‐dependent increase in resistance that was preferentially, but not selectively, confined to the large‐bore arterial resistance vessels. At a maximally effective dose (100 mg kg‐l), the nitric oxide inhibitor caused a marked constriction, within 5 min, on average increasingRtby 99%,Ra,proxby 138%,Ra,mieroby 18% andRvby 23%. The constrictor response toNg‐monomethyl‐L‐arginine was long‐lasting but disappeared gradually over a period of about 1 h. However, it could be abruptly abolished by excess L‐arginine (300 mg kg‐1, i.a.). The vasodilator response (Rt) to acetylcholine was significantly attenuated in the presence of N'‐monomethyl‐L‐arginine compared with the control response. The results suggested that nitric oxide formation from L‐arginine by the vascular endothelium plays a fundamental role in the regulation of vascular resistance (tone)in vivo, with its main site of action

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb09004.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The changes in endothelin‐like immunoreactivity in plasma during various provocations in the pig were investigated and related to those of neuropeptide Y, noradrenaline and adrenaline. Release as revealed by overflow was determined in the spleen, kidney and femoral vascular bed (skeletal muscle) simultaneously by collecting local venous and arterial blood samples. Under basal conditions there was no net release of endothelin‐like immunoreactivity from any region but a net removal (negative overflow) over the kidney. Endotoxin administration (20 μgkg‐1h‐1for 4 h) increased arterial endothelin‐like immunoreactivity, neuropeptide Y‐like immunoreactivity, noradrenaline and adrenaline seven‐, 27–, 100– and 166‐fold respectively, as well as splenic and renal vascular resistance. An increased overflow of endothelin‐like immunoreactivity, neuropeptide Y‐like immunoreactivity and noradrenaline, indicating local release, was observed in the spleen during endotoxin administration. The arterial plasma endothelin‐like immunoreactivity during endotoxaemia correlated significantly with the splenic and renal vasoconstriction (r =0.75 and 0.68 respectively). Chromatographic characterization revealed that the main portions of arterial plasma endothelin‐like immunoreactivity collected during endotoxaemia corresponded to synthetic endothelin‐1 and big endothelin. A similar uptake (50–90%) and plasma half‐life (1–2 min) of exogenous endothelin‐L‐like immunoreactivity was observed both under control conditions and after endotoxin, suggesting that elevated plasma endothelin‐like immunoreactivity after endotoxin was the result not of reduced clearance but rather of enhanced release. Asphyxia for 2 min did not increase arterial endothelin‐like immunoreactivity but evoked an increased overflow of endothelin‐like immunoreactivity, neuropeptide Y‐like immunoreactivity and noradrenaline as well as vasoconstriction in the spleen. Capsaicin induced a release of neuropeptide Y‐like immunoreactivity and noradrenaline from both the spleen and the kidney and of adrenaline from the adrenal, but no detectable overflow of endothelin‐like immunoreactivity from any of the vascular regions. Renal nerve stimulation, renal artery occlusion for 30 min, haemorrhagic shock, hypotension induced by nitroprusside infusion or serotonin did not cause any detectable increase in arterial plasma levels or local overflow of endothelin‐like immunoreactivity.It is concluded that plasma levels of endothelin‐like immunoreactivity are increased, suggesting release in the pig in response to endotoxin administration and asphyxia. The possible involvement of endothelin as a mediator of the peripheral vasoconstrictor responses d

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb09005.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A treated carbon fibre electrode was used to measure by differential normal pulse voltammetry or differential pulse amperometry the release of noradrenaline from the sympathetic nerve terminals innervating the smooth muscle in rat tail artery. On calibrationin vitrowith exogenous noradrenaline in phosphate‐buffered saline solution the electrode recorded an oxidation current at +0.1 V, the oxidation potential of noradrenaline. This signal was proportional to the noradrenaline concentration in the solution. When the electrode was apposed to the wall of the artery there was no oxidation current at +0.1 V under resting conditions, but electrical nerve stimulation for 1–100 s at 1–10 Hz induced a current with a peak at this potential. This signal was suppressed by tetrodotoxin, guanethidine or cadmium, or by omission of calcium; it was strongly enhanced by tetraethylammonium and potentiated by the noradrenaline uptake blockers desipramine or cocaine. The results indicate that the carbon fibre electrode method described here may be used to monitor on‐line the nerve stimulation‐induced increase in the local noradrenaline concentration at the surface of the muscle layer in a blood vessel such as the rat ta

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb09006.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

5‐Hydroxytryptamine has been suggested to be a mediator in peripheral cold‐induced vasospasm. In order to investigate the contribution of different 5‐hydroxytryptamine receptor subtypes in the contractile response during cooling, segments of subcutaneous hand veins obtained from 50 patients undergoing hand surgery were examinedin vitroin organ baths. The temperature in the bath was initially 37 ±C and was either continuously lowered to 10 ±C or kept constant at 37 ±C, 29 ±C or 20 ±C. Cooling to 25 ±C augmented the contractile response to 5‐hydroxytryptamine in intact as well as in endothelium‐denuded segments. The 5‐hydroxytryptamine2receptor antagonist ketanserin antagonized the contractile response to 5‐hydroxytryptamine at 37 “C, and in addition abolished the cold‐induced enhancement of the response during cooling. This points to a major role of the 5‐hydroxytryptamine2receptor in the cold‐induced augmentation of the response to 5‐hydroxytryptamine2which was further supported by increased contractions to the 5‐hydroxytryptamine2receptor agonist α‐methyl‐5‐hydroxytryptamine during cooling. Contractile responses were also obtained by the selective 5‐hydroxytryptamine1‐like receptor agonist GR43175 interpreted to indicate the presence of a smaller 5‐hydroxytryptamine1‐like receptor population. However, the response to GR43175 was unaffected by cooling. These results warrant further investigations of the role of 5‐hydrox

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb09007.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The purpose of the present study was to investigate the effects of 8 months of a specific and controlled sprint training programme on three groups of young athletes (two groups of males and one of females). Biopsies of vastus lateralis were taken before and after the period of training. The type percentage and diameter of the fibres, as well as the glycogen content and the activities of the enzymes of glycogen metabolism (glycogen synthase and glycogen phosphorylase), glycolysis (phosphofructokinase, pyruvate kinase, aldolase and lactate dehydrogenase), oxidative metabolism (succinate de‐hydrogenase) and creatine kinase and aminotransferases were studied. The results show an increase in the percentage of type I fibres and an increase in the diameter of both fibre types. A significant increase was also observed in glycogen content, and in the activities of glycogen synthase, glycogen phosphorylase, phosphofructokinase, pyruvate kinase, succinate dehydrogenase, aspartate aminotransferase and alanine aminotransferase. We conclude that a long period of sprint training induces a biochemical muscle adaptation to anaerobic exercise. This metabolic adaptation is followed by a morphological adaptation, although this is probably not as specific as the biochemical on

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb09008.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

In a previous study, prolonged low‐frequency muscle stimulation, inducing dynamic contractions in the hind leg of unanaesthetized rats, was shown to give rise to a hypoalgesia. The increase in pain threshold, measured as squeak threshold to noxious electric pulses, lasted 3 h.In the present study, the involvement of the endogenous opioid system in the post‐stimulatory analgesia was investigated using selective opioid receptor antagonists. The post‐stimulatory analgesia was completely reversed back to prestimulatory control levels by naloxone, 1 mg kg‐1. ICI 154, 129 and MR 2266 BS, selective δ‐ and ±‐receptor antagonists respectively, did not significantly influence the post‐stimulatory analgesia, although ICI 154, 129 had a minor pain threshold‐lowering effect. Rats pretreated with β‐funaltrexamine, a μ‐preceptor antagonist, did not exhibit any post‐stimulatory analgesia.These results suggest that opioid systems are involved in the increase in pain threshold after muscle stimulation and that the analgesic response is both elicited and main

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb09009.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Fifteen male physical education students were studied. The subjects trained for 4–6 weeks, 2–3 days per week, on a mechanically braked bicycle ergometer. A training session consisted of repeated 30‐s ‘all‐out’ sprints on a Wingate bicycle ergometer, on which the brake band of the flywheel was loaded with 75 g kg‐1body wt, with rest periods of 15–20 min between consecutive sprints. Thigh muscle biopsies were taken before and after the training period and were analysed for fibre types using a myofibrillar ATPase stain. The proportion of type I fibres decreased from 57 to 48% (P<0.05) and type IIA fibres increased from 32 to 38% (P<0.05). This study indicates that it is possible to achieve a fibre type transformation with high‐intensity training. The effect of two‐legged ‘sprint’ training on muscle fibre type composition may be related to a changed pattern of muscle fibre activation (e.g. an increased stimulation frequency). A change in fibre activation frequency may induce an increased synthesis of type II fibre myosin (fast myosin). Hormonal influences such as enhanced adrenergic stimulation of the muscle fibres cannot be excluded as a contr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb09010.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The influence of muscle type on functional responses of the female rat urethra was investigated using morphological and functionalin‐vitrotechniques. The urethral submucosa was found to contain longitudinally or obliquely oriented smooth muscle cells. The muscularis layer is composed of circularly oriented muscle cells. Near the bladder orifice smooth muscle fibres dominate, but in the mid‐urethra the vast majority is circularly oriented striated muscle cells.Circular preparations responded to electrical field stimulationin vitrowith a rapid contraction. Stimulation with single impulses resulted in a twitch response; frequencies exceeding 5–10 Hz induced a summation and tetanus. The response was unaffected by phenoxybenzamine, propranolol and scopolamine and had a low sensitivity to calcium‐free solution but was sensitive to suxamethonium and tetrodotoxin. Using longer impulse trains stimulation evoked also a slow contraction, sensitive to calcium‐free solution.In longitudinal preparations stimulation induced a relaxation followed by a contraction, responses much smaller than those seen in the circular preparations.Both preparations relaxed on addition of calcitonin gene‐related peptide or capsaicin. The relaxation to calcitonin gene‐related peptide was larger than that to capsaicin in longitudinal preparations but equally large in the circular ones. Substance P and 5‐hydroxytryptamine contracted both preparations. The longitudinal urethra showed a larger contraction to 5‐hydroxytryptamine than to substance P, whereas both substances induced similar responses in the circular preparations.The study shows a similar muscle arrangement in the female rat urethra as described in humans and further points to a functional differentiation between the differen

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb09011.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

We have previously described a substantial regional heterogeneity both in blood flow and in glucose uptake within single skeletal muscles in anaesthetized rabbits. These heterogeneities could be related to effects of anaesthesia. The main goal of the present study was therefore to study regional muscle blood flow and muscle glucose uptake in awake rabbits.We used the microsphere method and the deoxyglucose technique for assessment of regional blood flow and regional glucose uptake respectively. The measurements were performed in 0.25‐g regions from hind leg muscles. Some rabbits were first studied while awake and then during anaesthesia. Others were studied while either awake or anaesthetized.The degree of regional heterogeneity in blood flow and in glucose uptake was similar in awake and anaesthetized rabbits. Both temporal and spatial heterogeneity in blood flow were present. Evidence was found for vasomotion with a cycle time exceeding 45 min in awake rabbits. This perfusion pattern was similar in rabbits in which either the motor or sympathetic vasomotor nerves or both had been blocked.We conclude that regional perfusion and glucose uptake within single muscles are also markedly heterogeneous in awake rabbits. Regional, non‐synchronized fluctuations in blood flow with a long cycle time seem to be an important part of this perfusion heterogene

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb09012.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A membrane fraction containing ‐ATPase (EC 3.6.1.36) was prepared from pig gastric mucosa and found to contain phospholipase A, (EC 3.1.1.4) and lysophospholipase (EC 3.1.1.5) activities. Washing the membranes decreased their protein content by 25%. Recovery profiles of ‐ATPase, phospholipase A, and lysophospholipase were similar for membranes washed either with water or with 0.15 or 1.5 m KCI. Nearly identical distribution profiles were obtained for the three enzyme activities after centrifugation of washed vesicle membranes on a linear sucrose gradient. The phospholipase A2activity was stimulated by calcium and increased further in the presence of calmodulin.The amount of cellular radioactively labelled lysophosphatidylcholine was doubled upon cholinergic stimulation of isolated parietal cells prelabelled with [3H]glycerol or32P1. The liberated lyso(32P]phosphatidylcholine had its acyl chain in thesn‐1 position, which implies an activation of a phospholipase A2. These findings indicate that secretagogues which increase the cytosolic Ca2+concentration, i.e. acetylcholine, histamine and gastrin, may activate a phospholipase A2in the parietal

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1990.tb09013.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY