摘要:

AbstractRadioactively labelled adenosine and adenine were rapidly taken up by isolated rat fat cells, and incorporated into nucleotides, of which ATP dominated. The overall process had an apparent Kmof 1–5 μM. During incubation, especially in the presence of lipolytic agents, there was a reduction in labelled ATP with a compensatory increase in ADP, AMP, cAMP and nucleosides. The build‐up of adenosine during incubation was inhibited by theophylline, which inhibits 5′‐nucleotidase. Radioactivity released from perifused fat cells consisted mainly of nucleoside material, of which adenosine predominated. Lipolytic stimulation caused no significant increase in nucleoside outflow from perifused cells, whereas oxygenation was capable of reducing this outflow. It is concluded that adenosine is formed by fat cells as a consequence of ATP breakdown. Stimulation of lipolysis during activation of the sympathetic nerves leads to reversible ATP breakdown and adenosine release. Adenosine might therefore act as a modulator of lipolysisin vivounder these conditions, even though it does not serve as a feed back regulator in the prop

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06340.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractSeasonal changes in serum levels of growth hormone, Cortisol and thyroxine in calves and adult Spitzbergen reindeer(Rangifer taranilus platyrynehus)were measured and compared to those previously found in Norwegian reindeer(R.t. tarandus).Cortisol did not differ significantly between summer and winter, or between the subspecies. Growth hormone and thyroxine exhibited highly significant seasonal changes and subspecific differences: winter levels of growth hormone were much higher than summer levels in the Spitzbergen reindeer, while Norwegian reindeer differed very little from season to season. Both Spitzbergen and Norwegian reindeer had markedly reduced thyroxine levels during winter, but the values from the former were much lower than those from the latter. In summer, however, the levels were equal. The high levels of growth hormone and low levels of thyroxine in the Spitzbergen reindeer during winter are indicative of high lipolytic activity and a reduced metabolic rate, respectively.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06341.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe cerebral blood flow (CBF) and cerebral oxygen consumption (CMRO,) in the rat during normocapnia and hypercapnia were investigated by means of the intraarterial133Xenon injection technique; measurements were performed during normocapnia and hypercapnia and the effect of propranolol upon CBF and CMRO2was studied. The CBF technique applied to rat yield reliable results even in high flow situations. A steady state period of only 10–15 s is all that is necessary to obtain the initial slope of the133Xenon clearance curve from which CBF is calculated and measurements may be repeated within minutes. Hypercapnia caused an increase in CMRO2of 35% which confirms the findings of other investigators. The beta‐adrenergic receptor blocker propranolol (2 rag per kg i.v.) prevented this increase and could eliminate an increase in CMRO2already induced; this indicates that CO2affects adrenergic mechanisms. Although propranolol eliminated the CMRO2response to hypercapnia, it only reduced the CBF response; this dissociation of CBF and CMRO2response occurred probably because the beta‐receptor blockage only eliminated a CBF increase mediated through an increased CMRO2(cellular response) whereas a direct CO2effect upon the arterioles (vascular response) pers

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06342.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractIn maximally vasodilated SHR and NCR kidneys, perfused with filtrable and non‐filtrable perfusates, analyses have been performed concerning the extent of average renal tissue pressure (Pt) elevation which occurs upon glomerular filtration and causes passive autoregulation of flow. The results illustrate the great importance of distinguishing between ‘apparent’ (PA— PV/flow) and ‘true’ (PA— Pt/flow) renal resistance to flow. This is particularly so when the compared SHR and NCR renal vascular beds differ not only in true total renal resistance but also concerning the structurally determined ratio between the pre‐ and postglomerular resistances. The combined results show that this ratio is considerably elevated in adult SHR kidneys because of structural vascular changes, which is perhaps the most efficient way of resetting the ‘long term barostat function’ of the kidneys in hypertension. It is also illustrated how the altered pre‐/post‐glomerular ratio in SHR in combination with Ptrises can so markedly distort the results of apparently precisein vitrocomparisons of SHR and NCR renal vascular beds as to give entirely misleading results, with underestimations of the structurally based vascular hyperreactivity of the pregl

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06343.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe characteristics of 22 atrial receptors in 15 normotensive adult male Wistar rats were investigated. AH the receptor afferents were included in the C‐fibre group with conduction velocities from 0.4 to 1.2 m/sec. No atrial medullated receptors or ventricular C‐fibre endings were found. Two receptors were located in right atrium and 2 receptors throughout left atrium. Upon elevation of the left atrial pressure the receptor discharge was markedly elevated with thresholds from 2.5 to 9 mmHg in mean left atrial pressure. Ten of the atrial receptors displayed a clear cardiac rhythmicity upon activation and the discharge correlated with the v‐wave, indicating distension as the cause of receptor activation. The maximal firing rate in most receptors was very high (up to 70 Hz), but 8 receptors had maximal firing rates below 25 Hz. These low frequency receptors had higher threshold and showed a more irregular firing. Thus, there is a substantial population of atrial receptors with vagal non‐medullated afferents in the rat heart and the thresholds for many of these receptors are so low that they are likely to be active during normal con

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06344.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractAnesthetized rats were prepared with catheters in the hepatic portal (HPV) and femoral (FEM) veins and in the bladder or ureters. In some experiments the left kidney was denervated. HPV infusion of 1 M glucose at 2 ml/h for 20 min increased Na excretion by the kidney when given as a second infusion. Bilateral cervical vagotomy eliminated the increase in Na excretion during glucose infusion and uncovered a delayed decrease in Na andKexcretion. Renal denervation attenuated the increase in Na excretion to HPV glucose. FEM infusion of glucose had variable effects, increasing Na excretion only after vagotomy. The results are interpreted to suggest that central and vagal receptors tend to enhance Na excretion whereas splanchnic nerve afferents and humoral mediator(s) have the opposite effect.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06345.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractSeven young, healthy subjects performed bicycle exercise with a working load leading to exhaustion after one hour of work. The tests were done in the afternoon in the fed state. The serum insulin concentrations decreased from 22 to 4 mU/1 and plasma glucagon increased from 241 to 340 pg/1 already after 30 min of work. The level of adipose tissue lipoprotein lipase activity (LPLA) did not fall as had been expected, but increased. The skeletal muscle LPLA was unchanged. The results indicate that during the first hour of heavy exercise the heparin‐releasable LPLA in tissues is not influenced by the work induced changes in serum hormone level

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06346.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe axonal transport of adrenaline, noradrenaline and phenylethanolamine‐N‐methyl transferase (PNMT) has been studied in vivo in sympathetic neurons of the splanchnic nerve in the cod,Gadus morhua.Adrenaline and noradrenaline are transported at a mean axonal transport rate of 16 mm/day. After correction for a non‐mobile fraction of adrenaline and noradrenaline, which does not contribute to the amine accumulation proximal to a ligature, a maximal rate of transport was calculated to about 45 mm/day for both amines. The increased level of catecholamines in front of a ligature could be depleted by reserpine treatment, which strongly suggests that both amines are stored in granules. PNMT is transported at a slow rate of 2 mm/day. The subcellular distribution of the cod PNMT was exclusively non‐particular. The cod PNMT was further characterized by studying substrate specificity, temperature and pH optima. It is concluded that adrenaline and noradrenaline, stored in granules, are transported in a proximo‐distal direction at a high rate compare

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06347.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe relationship between thermoreception, hormonal secretion and muscular activity was studied. 6 men swam 60 min in 21, 27 and 33°C water at a speed requiring 68 % of Voamax (determined in 27°C water). Rectal temperature increased in 33°C (1.3 ± 0.2°C, mean and S.E.) and 27°C (0.7 ± 0.1°C) expts. but decreased in 21°C expts. (0.8 ± 0.3°C). Changes in esophageal and muscle temperatures parallelled changes in rectal temperature. Plasma noradrenaline was higher in 33°C than in 27°C expts. and growth hormone, Cortisol and glucagon concentrations increased in 27°C and 33°C expts. only. Insulin concentrations were uniformly depressed during swimming at the different water temperatures. In 21°C expts. noradrenaline and adrenaline concentrations were higher than in 27°C expts. VO2, carbohydrate combustion and peak lactate were slightly lower in 33°C expts. Plasma glucose decreased slightly and FFA and glycerol concentrations increased identically in all expts. Heart rate increased continuously during swimming in 27°C and 33°C expts., but not in 21°C expts. In conclusion the rise in body temperatures normally observed during exercise enhances the exercise induced increases in the plasma concentrations of noradrenaline, Cortisol, growth hormone and glucagon. Decreased body temperatures may elicit catecholamine secretion as a direct consequence of thermoreception. Shivering may account for previously observed decreases in insulin secretion during cold stress but not for increases in Cortiso

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06348.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe release of3H‐(‐)‐noradrenaline (NA) from rat vas deferensin vitrowas examined under various experimental conditions. It was found that in normal and reserpinized vas deferens the release of NA evoked by (+)‐amphetamine (5 times 10−6M) or low external Na+(26 mM) was antagonized by imipramine methiodide and desipramine, inhibitors of the NA uptake, but was not dependent on the presence of Ca2+in the medium and was not antagonized by the potent local anaesthetic agent bethoxycaine. The release evoked by veratridine in reserpinized tissue was antagonized by the uptake inhibitors but was in normal tissue only partially inhibited in presence of Ca2+but almost completely in absence of Ca2+. The release by high K+(117 mM) + low Na+(26 mM) in normal tissue was dependent on the presence of Ca2+and was antagonized by the muscarinic agonists carbacholine and metacholine and by high concentrations of desipramine. In the reserpinized vasa the corresponding release was not dependent on Ca2+and was not antagonized by the muscarinic agents but was inhibited by high concentrations of de

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06349.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY