摘要:

It has been speculated upon that the sympathetic activity might be of significance for fiber composition in skeletal muscle and by similar features indirectly affecting muscle contractility and regulation of circulation. To further study this hypothesis unilateral lumbar sympathectomy from L‐2 and down was applied on 5 female beagle dogs. After 14 weeks the gracilis muscle on the sympathectomized and the control side as well were examined for their muscle fiber compositions, endurance capacity and how heart rate and blood pressure responses were affected. Muscle fiber composition decreased to 28% slow twitch fibers as compared to 41 % on the control side (p<0.01). The relative cross‐sectional area of the fast twitch fibers increased simultaneously from 57 (control side) to 71 % (p<0.05). Endurance performance measured as contraction time at 50% of peak tension decreased from 55 to 29 s (p<0.05). On an individual bases including both control and sympathectomized muscles it was found that heart rate increased with percent fast twitch muscle fibers (p<0.01) and a tendency was present for a similar relationship between blood pressure and fiber types (p<

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07298.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

High threshold stimulation of the trigeminal nerve in sympathectomized cats caused an atropine and hexamethonium resistant vasodilation in the nasal mucosa. Stimulation of efferent parasympathetic neurons to the nose caused a partially atropine sensitive vasodilation which was abolished by hexamethonium. Combined trigeminal and parasympathetic nerve stimulation did not reveal any obvious functional interactions between these two systems. Local intra‐arterial infusions of substance P, VIP and acetylcholine caused a dose dependent vasodilation in the nasal mucosa. The relative vasodilatory potencies were substance P VIP>acetylcholine. Local infusions of capsaicin, known to release substance P from nerve endings, caused a marked longlasting biphasic vasodilation which was atropine and hexamethonium resistant. In conclusion, the present findings illustrate the presence of two vasodilator mechanisms of different nervous origin in the nasal mucosa. The trigeminal response is probably mediated via release of substance P, while the parasympathetic effect seems to be caused by acetylcholine and VI

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07299.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Adenosine appears to regulate resting blood flow in canine subcutaneous adipose tissue. Sympathetic nerve stimulation has been shown to enhance the adenosine production in this tissue. This study therefore tested the possibility that adenosine may influence the vascular responses to sympathetic nerve stimulation. Intraarterial infusion of adenosine (5–20 μM in arterial blood) increased the resting vascular conductance (from 0.048 ± 0.007 to 0.095 ± 0.013 ml ± min‐1100 g‐1± mmHg‐1) and the percental reduction in vascular conductance due to sympathetic nerve stimulation (4 Hz) by 34 per cent (p<0.05) and to i. a.noradrenaline by 27 per cent (p<0.05). The vasodilator response due to nerve stimulation after α‐blockade was reduced by adenosine. Dipyridamole (0.5–1.5 μM) + EHNA (3–10 μM), which increases plasma adenosine levels, had similar effects to adenosine, while theophylline (30–80 μM) decreased the vasoconstrictor response. The vasoconstrictor escape was enhanced by EHNA alone and in combination with dipyridamole, but was reduced by theophylline. On the other hand, the poststimulatory hyperemia was unaffected by adenosine, dipyridamole and EHNA, and theophylline. The results show that adenosine does not reduce the magnitude of the initial vasoconstrictor response in proportion to the increase in resting blood flow. The autoregulatory escape in adipose tissue during nerve stimulation appears to be mediated both by adenosine and by noradrenaline acting on β‐adrenoceptors. Poststimulatory hyperemia does not seem to be greatly influenced by exoge

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07300.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

We studied the responses of six healthy volunteers to standard 70° head‐up tilt tests before exhaustive exercise of short duration (control) and after 5, 25, 50, 80, and 110 min of recovery, all tests lasting for 6 min except when impending syncope (IS) necessitated premature termination of a test. Marked impairment of orthostatic tolerance was apparent during the first half‐hour of recovery as manifested by symptoms of IS in five subjects in one or both of the first two postexercise tilt tests. In none of the subjects who developed symptoms of IS did central venous pressure fall to a lower level than it did in the control test. From the central venous and arterial pressure reactions we conclude that when IS developed, declining systematic resistance rather than diminished cardiac filling was the responsible factor. The increased tendency for orthostatic collapse occurred during a period of recovery marked by persistent postexercise acidemia and hyperthermia suggesting interference of these conditions and associated events with the normal ability to vasoconstrict during orthos

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07301.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The aim of the present study in the rat was to localize the gastrointestinal site(s) of NTLI release and to investigate the importance of bile and pancreatic juice for fat‐induced NTLI release. Administration of Intralipid (2 ml) into the stomach and oleic acid (0.5 ml) into the duodenum increased the plasma concentration of NTLI (p‐NTLI). The increase in p‐NTLI levels occurred only when the jejunum and ileum were exposed to Intralipid but not when the exposure was limited to the stomach and duodenum. Exclusion of pancreatic juice significantly reduced the p‐NTLI response and exclusion of both bile and pancreatic juice completely abolished the p‐NTLI response to duodenally‐administered oleic acid. The results indicate that neurotension is released by a direct luminal exposure of the neurotensin containing N‐cells to fatty acids. It seems probable that fatty acids have to be transformed to a micellar form in order t

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07302.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The effect of sympathetic nerve stimulation or close i. a.infusion of noradrenaline on net fluid transport was investigated on anesthetized cats. In the presence of glucose in the solution perfusing the intestinal lumen the adrenergic mechanisms increased net fluid absorption in normal intestines. Substituting glucose with mannitol in the perfusate abolished this effect of adrenergic stimulation on the net fluid uptake. Furthermore, the effect of noradrenaline on net fluid transport in normal or choleraic intestines was abolished by tetrodotoxin (TTX), a nerve conductivity blocking agent. This suggests that the sympathetic influence is dependent on intraluminal glucose and that noradrenaline exerts its effect mainly via nerves. TTX significantly increased fluid uptake from normal intestines perfused with an isotonic electrolyte solution containing glucose while a considerably smaller effect was seen in intestinal segments perfused with a solution with mannitol. Based on these findings it is proposed that glucose in some way activates intramural nervous reflex(es) in the intestinal wall. According to this hypothesis the enhancement of fluid transport induced by adrenergic stimuli is explained by an inhibition of the glucose‐activated nervous secreti

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07303.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Substance P induced a dose‐dependent contraction of human segmental bronchi in vitro with a threshold dose of about 10‐6M. These preparations were obtained from patients undergoing lung tumor surgery. The substance P‐induced contractions were resistant to mepyramine and atropine, suggesting a direct effect on the bronchial smooth muscle. Capsaicin (10‐5M) also induced a slowly developing strong atropine‐resistant contraction of human bronchi in vitro. A rapid tachyphylaxis developed for the response to capsaicin. Both substance P and capsaicin were less potent than acetylcholine and histamine in inducing contractions of human bronchi. This finding may however be partly due to the experimental conditions and both substance P and capsaicin were comparatively much more potent in guinea‐pig preparations. Transmural field stimulation of the bronchial preparations in man resulted in contractions that were largely sensitive to atropine. The presence of capsaicin‐induced bronchial contractions however indicates the existence of a local non‐cholinergic axon‐reflex control of bronchial smooth muscle tone by

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07304.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Slow EEG shifts preceding voluntary self‐paced plantar flexions of hand and foot were studied in five healthy right handed subjects. The EEG was recorded from a coronal electrode chain at the central areas. The movements were preceded by slow negative shifts beginning even as early as one second before the movement and culminating in fast slopes during the early EMG activity at the onset of the movements. The EEG shifts preceding hand and foot movements were differently distributed over the scalp: hand movements were preceded by contralaterally maximal shifts a few hundred milliseconds before the movement, whereas the potential distributions preceding foot movements were symmetrical or ipsilaterally dominant. It is suggested that the differences in the scalp distributions are due to the different orientation of the current dipoles at the cortical motor areas of hand and fo

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07305.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

One hundred and twenty consecutive maximal leg extensions at a constant angular velocity of 1.5 radians. s‐1were performed by nine physical education students. Integrated electromyographic (IEMG) activity and power spectrum density function (PSDF) of the EMG were recorded from m. vastus lateralis, m. vastus medialis and m. rectus femoris using bipolar surface electrodes. Muscle biopsies were obtained from m. vastus lateralis before and after exercise. Tissue samples were analyzed for muscle fiber type distribution and lactate and glycogen concentration. Muscle force and IEMG decreased in parallel over the exercise period. Thus, the IEMG/force ratio was unchanged. Mean power frequency (MPF) of PSDF of the three muscles decreased by 10% (p<0.001) during the initial 25 contractions with no further decline during the latter part of exercise. The relative contribution of the highest bandwidth (130–500 Hz) of the PSDF decreased (p<0.001) between the first and final contractions. Muscle glycogen concentration decreased from 85 ± 23 to 68 ± 22 mmol ± kg‐1w. w.during the exercise. Muscle and blood lactate concentration averaged 12.1 ± 8.8 mmol ± kg‐1w. w.and 3.8 ± 0.8 mmol ± l‐1, respectively. The relative changes in MPF and in the highest bandwidth were correlated with muscle lactate concentration and fiber type distribution: in individuals with a high proportion of fast twitch muscle fibers and/or the greatest lactate accumulation, MPF and high frequency components of EMG PSDF decreased most markedly. Reductions in muscle force and IEMG are suggested to be partly due to a decreased motor neuron firing rate. It is discussed whether lactate or associated metabolic changes are influencing the motor unit action potential through f

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07306.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The effect of apamin, a polypeptide from bee venom, on the release of vasoactive intestinal polypeptide (VIP) during active neurogenic vasodilatations in the intestines was studied in vivo in anesthetized cats. Three non‐adrenergic, non‐cholinergic mechanisms were investigated, i. e. the vasodilatations seen upon transmural electrical field stimulation, pelvic nerve activation and stimulation of the intramural nerves with 5‐hydroxytryptamine (5‐HT) infused i. a. Apamin given close i. a.abolished the three vasodilator responses. Concomitantly, the increase of VIP release was also markedly diminished although apamin increased the rate of VIP release seen in the “resting” control period. The results are in agreement with the hypothesis that VIP is the neurotransmitter in the three investigated vasodilato

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07307.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY