摘要:

A mixture of the three branched‐chain amino acids (BCAAs) was supplied to subjects during two types of sustained intense exercise, a 30 km cross‐country race and a full marathon, and the effect on plasma and muscle concentrations of aromatic and BCCAs was studied. When BCAAs (7.5–12 g) were taken during exercise, the plasma and muscle (vastus lateralis) concentration of these amino acids increased, while in the placebo groups the concentration of BCAAs decreased in the plasma and remained unchanged in the muscle. In the placebo group, both types of exercise caused a 20–40% increase in the muscle concentration of the aromatic amino acids, tyrosine and phenylalanine, and the plasma concentration of these amino acids was increased after the marathon. Since tyrosine and phenylalanine are neither taken up nor metabolized by skeletal muscle, the increases in their concentrations in muscle might indicate net protein degradation during exercise. However, when the subjects were supplied with BCAAs during exercise, the increases in tyrosine and phenylalanine concentrations in both muscle and plasma were prevented. These results suggest that an intake of BCAAs during exercise can prevent or decrease the net rate of protein degradation caused by heavy e

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09422.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Compensatory, net fluid transfer across the capillaries was studied in the arm of man with plethysmographic technique during experimental hypovolaemia induced by lower body negative pressure (LBNP). Thirty, 60, and 110 cmH2O LBNP evoked rapid transfer of fluid from tissue to blood at average rates of 0.053, 0.088 and 0.147 ml min‐1100 ml‐1soft tissue, i.e. graded responses typical for a true homeostatic regulation. Other experiments demonstrated a net fluid absorption not only from the arm but also from a wide range of skeletal muscle and skin regions in the body during experimental hypovolaemia, i.e. the more or less generalized response required if the absorption process is to contribute importantly to plasma volume regulation. In a third series of experiments it was shown that gradually applied LBNP was a much less efficient stimulus for fluid gain into the circulation than rapidly instituted LBNP, tentatively explaining the fairly slow plasma volume refill in man in previous literature after experimental, true and necessarily slow blood loss. Taken together, the findings described warrant the conclusion that the described process of fluid gain into the circulation may be a very important component in the overall homeostatic circulatory regulation in states of hypovolaemia. The data in fact suggest that the process might be capable of increasing plasma volume by as much as 600 ml within only 10 min, suggesting that such plasma volume control might be much more potent than previously belie

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09423.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The impact of environmental factors on hypertension depends to a certain extent on the individual's genetic background. Environmental temperature is one of the known modulators of blood pressure. We have previously demonstrated abnormal expression of a major environmentally‐controlled gene, hsp70, in hypertensive mice and rats. We have developed a simpleex vivomethod for the evaluation of hsp genes expression in humans. In the present study, we investigated the accumulation of hsp70 mRNA in lymphocytes from normotensive and hypertensive humans. The data showed a higher accumulation of hsp70 mRNA in lymphocytes from hypertensivesvsnormotensives (2.04±0.35vs1.48±0.29 OD mm2,P<0.05) submitted to heat stress (15 min at 42 °C). Basal levels were the same in both groups (0.11 ±0.01vs0.10±0.01 OD mm2, respectively). These results support our hypothesis that alterations in the expression of a major environmentally‐controlled gene, hsp70, may be involved in enhanced environmental responses even in human hype

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09424.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Our previous studies strongly indicate that the capillary filtration coefficient (CFC) in skeletal muscle and skin of man is much larger than previously believed, or about 0.050 ml min‐1100 ml‐1mmHg‐1. The hypothesis that this large capillary fluid permeability is a factor of primary importance for plasma volume control was approached. Experimental hypovolaemia induced by lower body negative pressure (Lbnpof 70–95 cmH2O) was associated with a rapid net fluid gain from the studied upper arm into the circulation of 0.17 ml min‐1100 ml‐1tissue. The transcapillary driving force for this fluid transfer, probably caused by adrenergic adjustment of vascular resistance, with a decline of capillary pressure, was relatively small, or 1.7 mmHg on average. CFC was instead very high during LBNP, increasing from a control value of 0.054±0.004 (SE) to no less than 0.097±0.007 ml min‐1100 ml‐1mmHg‐1, probably reflecting an increased number of effectively perfused capillaries. It is suggested that the large capillary fluid permeability in skeletal muscle and skin of man, with large tissue mass and fluid reservoir, may be of great functional importance for plasma volume control after blood loss and also in other (patho)physiological situations. As demonstrated, it can thus permit rapid transfer of large fluid volumes into the circulation and, perhaps of special importance, with only small transcapillary driving force (capillary pressure decline). If capillary permeability were to be more limited, reasonably rapid fluid transfer instead might have required pronounced and, for tissue nutrition, necessarily undue adjustments of vascular resistance in order to cause more marked decline in

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09425.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Changes in cardiac output and in superior mesenteric arterial flow were followed with Doppler ultrasound techniques in five young, healthy persons for 2 h after ingestion of medium‐sized (4 MJ), fluid meals containing either carbohydrate, protein, fat or water only. Measurements were carried out before meals and at regular post‐meal intervals, during which mean arterial blood pressure was also followed.All energy‐containing meals caused marked and gradually developing post‐prandial increases in cardiac output as well as in superior mesenteric arterial flow. The maximum flow levels were reached in the course of 30–60 min and maintained until the observations ended after 2 h. The intake of water caused no such flow increases.There were considerable interpersonal variations in the size and in the speed of development of the flow increases after the three types of energy‐containing meals. The flow‐increasing effects of the three meal types were not significantly different, even if the most marked increases (median values about 1 1 min‐1for both cardiac output and superior mesenteric arterial flow) occurred after carbohydrate meals.The marked effects on circulation of the three food components were also revealed in the calculated, integrated amounts of ‘extra’ cardiac output and superior mesenteric arterial flow observed in the course of the 2 h following the meal. Values of more than 100 1 for such ‘extra’ flows were seen after carbohydrate meals.The marked ingestion‐released increase in blood flow to the splanchnic organs is apparently partly met by an increase in cardiac output, and partly by some redistribution of flow, which bene

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09426.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The regional distribution of coronary perfusion within the left ventricle is markedly heterogenous. The perfusion pattern is composed of both spatial and temporal variations in perfusion among single myocardial samples. Previous investigators have mostly studied short‐term (<1 min) temporal variability. The aim of this study was to quantify long‐term fluctuations in perfusion to single samples within the rabbit left ventricle.Coronary perfusion was estimated from the deposition of microspheres in myocardial samples (range 32–96 mg). Two batches of microspheres were infused either simultaneously or sequentially over specified periods of time. The paired values for regional perfusion were compared and Kendalls correlation coefficient (T) calculated. The assumption being that the lowerT, the higher degree of temporal perfusion variability was present.TheTfor paired values of regional myocardial perfusion based on two sequential infusions lasting either 10 s, 5, 10 or 30 min, averaged 0.40, 0.55, 0.80 and 0.80, respectively. No difference was detected between awake and anaesthetized animals. TheTfor two simultaneous infusions averaged 0.95 irrespective of the duration of the infusion, indicating negligible methodological error. The coefficient of variation for spatial perfusion heterogeneity ranged from 0.3 to 0.4 irrespective of the infusion duration.The findings suggest that regional coronary vasomotion is characterized by a wide range of cycle times, some of which have cycle times of more than 30‐min duration. Although part of the regional perfusion heterogeneity was due to long‐term fluctuations in perfusion, temporal variations with cycle times less than 5 and 10 min, respectively, were more

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09427.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Rats were exposed to short‐term restraint (held by the tail for 1 min), injected s.c. with saline or subjected to the combination of these treatments. Fifteen and 30 min after these treatments the means serum corticosterone level was significantly increased by more than four times, compared to rats taken directly from their home cages, indicating a stress response. In the peri‐aqueductal grey, the level of substance P‐like immunoreactivity was increased by 45% (P<0.01) and 65% (P<0.01) 30 and 60 min after the combined treatment, respectively. Significant increases of the level of substance P‐like immunoreactivity in the peri‐aqueductal grey were also found after restraint only and after a s.c. saline injection. Similar, but less marked, changes in the level of cholecystokinin‐like immunoreactivity in the PAG were also seen. In the accumbens a significantly decreased level of substance P‐like immunoreactivity was encountered at 15 and 30 min after treatment, while the levels of cholecystokinin‐ and neuropeptide Y‐like immunoreactivity were not significantly changed. In other regions studied, no effects on peptide levels were seen. The changes in peptide levels had a time course similar to that of the increase in serum corticosterone. Also the successive removal of rats from a common cage was found to increase significantly the serum corticosterone and the substance P‐like immunoreactivity in the peri‐aqueductal grey in the animals that were taken late in sequence from the cage. The present results demonstrate that apparently innocuous treatment may induce rapid and marked changes of brain peptide levels, the changes being different depending on the peptide and region investigated. Further on, the effects encountered are similar in magnitude to those previoush demonstrated after va

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09428.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The aim of the present study was to investigate whether gastrin, cholecystokinin (CCK) and somatostatin secretion can be influenced by sensory stimulation and if so, whether such effects are mediated via the vagal nerves. Male rats anaesthetized with chloral hydrate were exposed to three different stimuli, i.e. to low frequency (2 Hz) electrical stimulation of muscles via needles (electro‐acupuncture), to thermal stimulation at 40 °C or to vibration at 100 Hz. The two former stimuli activate mainly small and medium sized myelinated fibres from muscles and skin respectively, whereas vibration activates large myelinated fibres from skin, subcutaneous tissue and muscles. Experiments were also performed on animals that were vagotomized or exposed to prior treatment with atropine (0.5 mg kg‐1). Blood was collected at various time intervals and plasma levels of gastrin, CCK and somatostatin were measured with radioimmunoassay (RIA).All three stimuli, i.e. electro‐acupuncture, vibration and thermal stimulation caused significant elevations of gastrin (103 ± 11–151 ± 16 pm, 105 ± 8–140 ± 12 pmand 105 ± 14–162 ± 4 pm) and cholecystokinin (9 ± 0.8–15 ± 2.8 pm, 8 ± 0.5–10 ± 1.5 pmand 8.0 ± 0.5–10.5 ± 1.5). Somatostatin was raised in response to electro‐acupuncture (10 ± 1–14 ± 3 pm). Vagotomy and atropinization abolished the release of gastrin and CCK in response to all three stimuli. CCK levels were significantly reduced following electro‐acupuncture in atropinized rats. In conclusion, gastrin and cholecystokinin release is stimulated by activation of sensory afferent, originating in skin, subcutaneous tissue as well as in muscle. Some

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09429.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

We have studied the effects of acute and long‐term treatment of cats and rats with atropine on the levels, release and effects of two peptides, vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI), that probably co‐exist with acetylcholine in the parasympathetic nerves supplying the submandibular gland.Atropine treatment (progressively increasing doses from 2 to 15 mg kg‐1injected s.c.) for 14 days did not alter the contents of VIP‐ or PHI‐like immunoreactivity (‐IR) in the cat submandibular gland or in three other tissues (nasal mucosa, trachea and tongue). Acute as well as long‐term atropine treatment decreased the vasodilatation following low‐, but not high‐, frequency parasympathetic nerve stimulation. During prolonged stimulation (60 min) there was a decreased vasodilatation response following both acute and long‐term atropine treatment. The overflow of VIP‐IR and PHI‐IR following parasympathetic nerve stimulation was markedly increased by acute, but not by long‐term atropine treatment. The VIP‐ or PHI‐induced stimulation of cyclic AMP (cAMP) accumulation in the cat submandibular gland was not altered after long‐term atropine treatment.Similarly, treatment of male Sprague‐Dawley rats with atropine (20 mg kg‐1) or imipramine (20 mg kg‐1) for 14 days did not alter the sensitivity to VIP or to PHI of cAMP accumulation in the submandibular gland, nor was there any change in VIP‐IR or PHI‐IR content.In conclusion, although atropine treatment causes an acute increase in the overflow of VIP and PHI evoked by parasympathetic nerve stimulation, there is no depletion of peptide stores upon long‐term treatment, nor is there any change in the effect of

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09430.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Secretin‐dependent ductular HCO‐3secretion into bile may involve secretion of H+to interstitial fluid and HCO‐3to bile by the ductular epithelium. To determine whether secretin causes bile ductules to secrete H+, we have examined the effect of secretin on the elimination of an intracellular acid load from bile ductular epithelium during pharmacological blockade of Na+‐H+exchange and in the absence of HCO‐3. Microdissected bile ductules from pigs were suspended in HCO‐3free HEPES buffer and loaded with acid using an NH4Cl prepulse technique. Intracellular pH was measured using dual‐wavelength excitation of BCECF fluorescence. Na+‐H+exchange was defined as a Na+‐dependent and amiloride‐ and 5‐(N,N‐hexamethylene)‐amiloridesensitive efflux of H+‐ions following acid loading. We found that secretin stimulated ductular H+secretion independent of Na+‐H+exchange. Blockade of Na+‐H+exchange by hexamethylene‐amiloride did not affect secretin‐dependent ductular HCO‐3choleresisin vivo. We conclude that secretin stimulates bile ductules to secrete H+‐ions to interstitial fluid as well as HCO‐3ions to bile by

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09431.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY