bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of α‐adrenoceptor blockade by phentolamine on basal and stimulated insulin secretion in the mouse
Authors: AHRÉN BO , LUNDQUIST INGMAR
Published: December 2008

The sympathetic nervous system is known to innervate the pancreatic islets and to have the capability to influence islet hormone release. The effects are, however, complex since the islet nerves contain catecholaminergic as well as peptidergic fibres, and the catecholamines stimulate α‐ as well as β‐adrenoceptors. The present study was undertaken to establish the possible influence of the a‐adrenoceptors on basal and stimulated insulin secretion under in vivo conditions. The α‐adrenoceptor blocker phentolamine was injected at various dose levels i.p. to mice and a dose‐dependent increase in plasma concentrations of insulin was seen. The maximal plasma insulin levels were observed 10 min after injection and were accompanied by decreased plasma glucose concentrations. Additionally, plasma glucose levels fell in response to phentolamine by an apparent insulin‐independent manner, since at the low dose of 2.6 μmol kg‐1, plasma glucose levels did decrease without any apparent increase in plasma insulin levels. After injection of a low dose of phentolamine 10 min prior to a rapid i.v. injection of one of four different insulin secretagogues, the following effects on insulin release were observed. Glucose (+ 55%) and the cholinergic agonist carbachol (+ 140%) displayed a potentiated insulin secretory response after phentolamine pretreatment, whereas the β2‐adrenoceptor agonist terbutaline (‐45%) had a blunted, though not abolished, insulin response. The absolute insulin secretory response to CCK‐8 was unaffected by phentolamine despite the fact that plasma glucose levels were lowered by phentolamine. In conclusion, phentolamine enhanced insulin secretion and depressed plasma glucose levels in mice. Further, it influenced stimulated insulin secretion by a manner dependent on the nature of the secretagogue. The results thus suggest that α‐adrenoceptors are involved in the precise regulation of basal and stimulated insulin secretion, and that a‐adrenoceptor blockade does not always result in a potentiated insulin secretion.
Contractile properties, fatiguability and glycolytic metabolism in fast‐ and slow‐twitch rat skeletal muscles of various temperatures
Authors: BLOMSTRAND EVA , LARSSON LARS , EDSTROM LARS
Published: December 2008

The influence of muscle temperature (28 and 36 °C) on fatiguability and glycolytic metabolism was studied during 5 min of intermittent stimulation of motor nerves of the tibialis anterior, extensor digitorum longus (fast‐twitch) and soleus (slow‐twitch) muscles in the rat at 100 Hz (200 ms per s). The decline in isometric tension was not affected by muscle temperature either in fast‐ or in slow‐twitch muscles. In fast‐twitch muscles the utilization of glycogen during stimulation was the same at 28 and 36 °C, while in the soleus muscle it was lower at 28 °C. The concentration of glucose‐6‐phosphate immediately after stimulation was higher in the muscles at 28 °C than in those at 36 °C, whereas no difference in lactate concentration was found between the two temperature groups. These observations indicate that compared with the rate at 36 °C, the rate of glycogenosis at 28 °C is unchanged in fast‐twitch, but decreased in slow‐twitch muscle. This might imply increased economy of ATP turnover during contraction in the soleus muscle at 28 °C.
Nuclear zinc in human epididymal and ejaculated spermatozoa
Authors: KVIST ULRIK , BJÖRNDAHL LARS , ROOMANS GODFRIED M. , LINDHOLMER CHRISTER
Published: December 2008

Sperm nuclear zinc content (expressed as zinc/phosphorus and zinc/sulphur ratios) was determined with X‐ray microanalysis in individual, air‐dried, epididymal spermatozoa from elderly men, and in ejaculated spermatozoa from healthy donors. Ejaculated sperm nuclei contained (also after treatment with sodium dodecyl sulphate) more zinc than epididymal spermatozoa. The results indicate that the human spermatozoon accumulates zinc from the prostatic fluid upon ejaculation.
The influence of purified somatomedins and insulin on foetal rat brain DNA synthesis in vitro
Authors: ENBERG GÖSTA , THAM ANNE , SARA VICKI R.
Published: December 2008

The two main forms of somatomedins, termed insulin‐like growth factor I and II (IGF‐I and IGF‐II), have been isolated from human plasma.
Autonomic nervous control of endometrial secretion in the guinea pig
Authors: HAMMARSTRÖM MARGARETA
Published: December 2008

HAMMARSTRÖM, M. Autonomic nervous control of endometrial secretion in the guinea pig. Acta Physiol Scand125, 461–469. Received 22 March 1985, accepted 6 May 1985. ISSN 0001–6772. Department of Physiology I, Karolinska Institute, Stockholm, Sweden.

Secretory responses of the guinea pig endometrium to field stimulation of nerves and/or drugs were studied throughout oestrous cycle. Secretory responses are dependent on the hormonal state of the animals and are seen at oestrus, metoestrus and at implantation time. The cholinergic nature of the secretory innervation was confirmed. Optimal secretory response was found at 0.5 or 1 Hz continuous stimulation. Adrenergic inhibition was revealed at metoestrus (day 3–5), The α‐adrenergic inhibitory influence had its optimal frequency at 0.5 Hz. The inhibition seemed to be both prejunctional and postjunctional. VIP increased endometrial secretion, the effect was probably preterminal. Burst stimulation at any frequency gave less (or no) secretory responses under these experimental conditions. The complex organization of the endometrial innervation is apparent.
Effects of amrinone on the contractile behaviour of frog striated muscle fibres
Authors: MÅNSSON ALF , EDMAN K. A. P.
Published: December 2008

MANSSON, A. & EDMAN, K. A. P. 1985. Effects of amrinone on the contractile behaviour of frog striated muscle fibres. Acta Physiol Scand125, 481–493. Received 18 March 1985, accepted 10 May 1985. ISSN 0001–6772. Department of Pharmacology, University of Lund, Sweden.

The effects of amrinone (0.005–2.1 mM) were studied on isolated single muscle fibres of the frog (0.6–4.3 °C). In the concentrations used amrinone potentiated the isometric twitch, increased the initial rate of force development and prolonged the time to peak twitch force and the time from peak force to half relaxation. There was a moderate but statistically significant (P < 0.001) enhancement of the maximum tetanic force and a marked slowing of the relaxation phase of the tetanus. Amrinone depressed the velocity of unloaded shortening by 33 ± 2% (mean ± SE, π= 6) and reduced the curvature of the force‐velocity relation leading to an increase of a/PO in Hill's (1938) hyperbolic equation. In accordance with the effects of amrinone on the force–velocity relation, there was a decrease in the rate of redevelopment of force after the fibre was released to zero tension during the tetanus plateau. The evidence suggests that the drug affects the contractile properties of frog muscle fibres by two different mechanisms: (1) amrinone affects the excitation–contraction coupling causing enhanced calcium release in response to membrane excitation and (2) amrinone exerts a direct effect on the kinetics of turnover of the myosin cross‐bridges. The latter aspect of the drug effect was evaluated in terms of A. F. Huxley's (1957) cross‐bridge model by means of a computer program.
Effects of 5‐hydroxytryptamine and related agents on endothelial cell oxidative metabolism in vitro
Authors: KJELLSTRÖM B. THOMAS , ÖRTENWALL PER , RISBERG BO
Published: December 2008

KJELLSTRÖM, B.T., ÖRTENWALL, P. & RISBERG, B. 1985. Effects of 5‐hydroxytryptamine and related agents on endothelial cell oxidative metabolism in vitro. Acta Physiol Scand 125, 501–504. Received 10 April 1985, accepted 21 May 1985. ISSN 0001–6772. Department of Surgery I, University of Göteborg, Sweden.

A recently described microrespirometric method was used to determine the influence of 5‐hydroxytryptamine (5‐HT), nialamide, imipramine and ouabain alone and in combinations on oxidative metabolism in monolayer cultures of endothelial cells from the rat pulmonary artery. It was found that exposure to 5‐HT increased oxygen uptake in the cultures, while imipramine or ouabain decreased respiration; nialamide had no obvious effect. When used in combinations, the effect of ouabain or imipramine dominated over the 5‐HT effect.

The explanation for this 5‐HT stimulating effect on endothelial cell oxidative metabolism, previously undescribed, is suggested to be that 5‐HT exposure stimulated individual cells to contract. This active contraction resulted in an increased energy demand reflected in elevated oxygen consumption, an effect inhibited by ouabain or imipramine.
Effects of adrenaline infusion on cAMP and glycogen phosphorylase in fast‐twitch and slow‐twitch rat muscles
Authors: CHASIOTIS D.
Published: December 2008

CHASIOTIS, D. 1985. Effects of adrenaline infusion on cAMP and glycogen phosphorylase in fast‐twitch and slow‐twitch rat muscles. 1985 Acta Physiol Scand125, 537–540. Received 15 February 1985, accepted 28 May 1985. ISSN 0001–6772. Department of Clinical Chemistry II, Karolinska Institutet, Huddinge University Hospital, Huddinge, Sweden.

This study investigated the effect of adrenaline infusion on the cAMP content, glycogen phosphorylase activity and the rate of glycogen breakdown in rat extensor digitorum longus (EDL) and soleus muscles. Adrenaline was constantly infused in a dose of 0.15 μg kg‐1 body wt min‐1. The cAMP content increased approximately 2.8‐fold in both muscles after 2 min of infusion. Phosphorylase a 4‐ b activity was six times higher in fast‐twitch muscle (EDL) than in slow‐twitch (soleus) and remained unchanged during the infusion. Phosphorylase a activity increased by 8.4‐fold in EDL and 2.4‐fold in soleus muscles during the infusion period. Glycogen content decreased in EDL muscle by 10% whereas no change was observed in soleus. It is concluded that β‐adrenergic stimulation by adrenaline results in a similar cAMP increase in both muscles. The low rate of glycogen breakdown in EDL and the unchanged content of glycogen in soleus muscle suggest that cAMP mediated transformation of phosphorylase b to a in itself is not adequate for a rapid glycogenosis in muscle phosphorylase.
Interstitial fluid pressure in the isolated perfused rabbit lung
Authors: WIIG HELGE , OPDAHL HELGE , NICOLAYSEN ANNE , NICOLAYSEN GUNNAR
Published: December 2008

WIIG, H., OPDAHL, H., NICOLAYSEN, A. & NICOLAYSEN, G. 1985. Interstitial fluid pressure in the isolated perfused rabbit lung. Acta Physiol Scand 125, 601–607. Received 10 March 1985, accepted 9 May 1985. ISSN 0001–6772. Department of Physiology, University of Bergen and Institute of Physiology, University of Oslo, Norway.

Interstitial fluid pressure was measured in nine isolated perfused rabbit lungs with the servonull micropipette method. Bevelled glass micropipettes, with tip diameter 2–6 μm (o.d.) were inserted 2–6 mm into the left lung. At alveolar pressures of 3 to 5 cm H2O we found mean interstitial fluid pressures of 1.0 (SD 1.0) and 1.6 (SD 1.0) cm H2O relative to pleural pressure in the upper (n = 19) and lower (n = 21) lobes respectively. The vertical distance between the measuring sites in the upper and lower lobes was about 3 cm. Net filtration caused by elevated left atrial pressure caused practically no change in interstitial fluid pressure. Increased alveolar pressure either increased or decreased interstitial fluid pressure. The measured pressures probably represent interstitial fluid pressure in alveolar junctions or in the interstitium around small pulmonary arteries or veins. We conclude that interstitial fluid pressure in these sites is between alveolar and pleural pressure, and that it is only moderately affected by changes in alveolar pressure. The interstitial compliance appears to be high and there seem to be little or no vertical gradients in interstitial fluid pressure within the lung.
Plasma lipoprotein distribution, faecal cholesterol excretion, and activities of lipoprotein lipase, hepatic lipase and lecithin:cholesterol acyltransferase in rats fed diets rich in sucrose or sunflower oil
Authors: HAUG ANNA , HØSTMARK ARNE T. , SPYDEVOLD ØYSTEIN
Published: December 2008

HAUG, A., HØSTMARK, A.T. & SPYDEVOLD, Ø. 1985, Plasma lipoprotein distribution, faecal cholesterol excretion, and activities of lipoprotein lipase, hepatic lipase, and lecithin: cholesterol acyltransferase in rats fed diets rich in sucrose or sunflower oil. Acta Physiol Scand 125, 609–617. Received 10 January 1985, accepted 10 May 1985. ISSN 0001–6772. Department of Preventive Medicine and Institute for Medical Biochemistry, University of Oslo, Norway.

Plasma HDL2 has been suggested to carry cholesterol to the liver for subsequent excretion in the bile and faeces. The enzymes lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin: cholesterol acyltransferase (LCAT) have been implicated in the centripetal cholesterol transport. Activities of these enzymes, the amount of faecal cholesterol excretion and the level of plasma lipoproteins were determined in male rats fed for 4 weeks on purified diets in which the sunflower oil: sucrose ratio was either 0.03 (group a) or 1.01 (group b). Whole plasma triacylglycerols (TG), unesterified cholesterol (UC) and phospholipids (PL) were highest in group (a). The concentration of cholesteryl esters (CE) was similar in the two groups. Protein, TG and UC of VLDL, and TG, UC, CE and PL of HDL2 were higher in group (a) than in group (b). The HDL3‐protein and TG were lowest in group (a). Thus, total weight of VLDL and HDL2 were increased, and HDL3 reduced in group (a), which had also increased activities of HL and adipose tissue LPL. Activity of LCAT was lower, and faecal excretion of cholesterol was reduced by about 50% in group (a) compared to group (b). Accordingly, in the rat increased plasma levels of HDL2 are not necessarily indicative of increased faecal cholesterol excretion.
Influence of thyroid hormones on transport function and Na+‐K+‐ATPase activity in the rat choroid plexus
Authors: LINDVALL‐AXELSSON M. , HEDNER P. , OWMAN CH. , WINBLADH B.
Published: December 2008

LINDVALL‐AXELSSON, M., HEDNER, P., OWMAN, CH., & WINBLADH, B. 1985. Influence of thyroid hormones on transport function and Na+‐K+‐ATPase activity in the rat choroid plexus. Acta Physiol Scand 125, 627–632. Received 11 February 1985, accepted 28 May 1985. Departments of Histology and Internal Medicine, University of Lund, Lund, and Department of Pediatrics, Sachs' Children Hospital, Karolinska Institute, Stockholm, Sweden.

The sympathomimetic stimulation of choroid plexus transport and secretion in rat seems to be mediated by β‐adrenergic receptors. In the present report the effect of induced changes in thyroid function on transport mechanisms in the rat choroid plexus was studied. Following induction of hyperthyroidism (treatment with T3 for 10 days) the tissue/medium ratio (T/M) for choline uptake in choroid plexus in vitro decreased significantly by 68%. The Na+‐K+‐ATPase activity showed a statistically significant increase of about 16%. Also following cervical sympathectomy, T3 caused a reduction of the T/M for choline, to the same level as in the non‐sympathectomized animals, while the effect of T3 on the Na+‐K+‐ATPase activity was changed into a 22% decrease. Hypothyroidism (administration of PTU in the drinking water) had little or no effect on the uptake and accumulation of choline in the choroid plexus. The Na+‐K+‐ATPase activity was reduced by 40%, in contrast to the stimulating effect of T3. There is, hence, reason to believe that the transport of choline in the choroid plexus is only partly regulated by adrenergic mechanisms acting via Na+‐K+‐ATPase. The major effect of T3 on the choline uptake may be exerted by a mechanism different from the ATPase activity and not involving adrenergic receptors.
Effects of intra‐arterially infused adenosine triphosphate (ATP) on release of vasoactive intestinal polypeptide (VIP) from the gastrointestinal tract of the cat
Authors: SJÖQVIST A. , FAHRENKRUG J. , HEMLIN M. , JODAL M. , LUNDGREN O.
Published: December 2008

SJÖQVIST, A., FAHRENKRUG, J., HEMLIN, M., JODAL, M. & LUNDGREN, O. 1985. Effects of intra‐arterially infused adenosine triphosphate (ATP) on release of vasoactive intestinal polypeptide (VIP) from the gastrointestinal tract of the cat.Acta Physiol Scand125, 693–698. Received 28 February 1985, accepted 26 June 1985. ISSN 0001–6772. Department of Physiology, University of Göteborg, Sweden.

Close i.a. infusions of ATP were made to the stomach, the small intestine or the colon in the cat. The vascular reactions were followed by recording arterial pressure and total venous outflow continuously and the release of VIP was estimated intermittently from arterio‐venous concentration differences and blood flow. In all experiments ATP caused a vasodilatation and an increased release of VIP into blood. In control experiments it was shown that evoking a vasodilatation of the same magnitude by close i.a. infusions of isoprenaline or papaverine did not evoke any similar release of VIP. It is concluded that the infused ATP released VIP from the different parts of the gastrointestinal tract. Possible mechanisms underlying this effect are tentatively discussed.
Turnover rate of interstitial albumin in rat skin and skeletal muscle. Effects of limb movements and motor activity
Authors: REED ROLF K. , JOHANSEN STEINAR , NODDELAND HARALD
Published: December 2008

REED, R.K., JOHANSEN, S. & NODDELAND, H. 1985. Turnover of interstitial albumin in rat skin and skeletal muscle. Effects of limb movements and motor activity. Acta Physiol Scand 125, 711–718. Received 6 December 1984, accepted 19 July 1985. ISSN 0001–6772. Department of Physiology, University of Bergen, Bergen, Norway.

Fractional removal rate (FRR) of radioactive‐labelled human serum albumin (I‐HSA) injected subcutaneously or intramuscularly was determined by external gamma‐detecting equipment. Radioactivity over the injection site fell monoexponentially during registration periods up to 6 h. The FRR was calculated as the turnover rate constant of the radioactivity removal. The FRR fell into one of two ranges: in anaesthetized rats FRR was 0.02–0.03 h‐1, and in awake and freely moving rats FRR was 0.08–0.11 h‐1. Inawake rats, FRR was similar during day and night (spontaneous motor activity is four times higher during the night). Passive limb movements at 1 Hz in anaesthesia increased FRR in skin to that in awake rats, while FRR in skeletal muscle was unchanged. Immobilization resulted in FRR similar to that in anaesthesia. Interstitial albumin mass did not change during 6 h of anaesthesia. It is concluded that the observed FRR reflects steady state changes in albumin turnover. In the awake and freely moving rats at least 3/4 of the removal of albumin is by the lymphatics. Calculated lymph flow was 10 μl g‐1 h‐1 and 40 μg‐1 h‐1 in skeletal muscle and skin respectively with corresponding figures during anaesthesia of 3 μg‐1 h‐1 and 10 μg‐1 h‐1 respectively.
Effect of intragastric pH, prostaglandins and prostaglandin synthesis inhibitors on the release of gastrin and somatostatin into the gastric lumen of anaesthetized rats
Authors: ALINO S. F. , GARCIA D. , UVNÄS‐MOBERG K.
Published: December 2008

The object of the present work was to study the influence of antral pH, of aspirin and indomethacin, and of prostaglandins A2, E, and Ea on the intragastric output of somatostatin and gastrin induced by electrical vagal stimulation (5 V, 2 ms, 2, 5 and 10 Hz). Experiments were performed on anaesthetized rats in which the stomach was perfused with a dextran solution (pH ‐ 1.5 or ‐ 6). To assess the effect of vagal stimulations on gastric acid secretion and on gastrin and somatostatin release, pH as well as somatostatin and gastrin levels was recorded in the perfusate effluent. During perfusion of the stomach with dextran solution, pH ‐6, vagal stimulation at 10 Hz decreased perfusate pH to 1.3 and gastrin and somatostatin were released at a ratio of 2:1. Less gastrin and more somatostatin (ratio 0.1:1) was released by the same stimulation when the stomach was pre‐perfused with acid solution (pH ‐ 1.5), although also in these experiments the pH of the perfusate fell to 1.3. When vagal stimulations were performed after the rats had been pretreated with aspirin or indomethacin, more somatostatin than gastrin was detected in the perfusate independently of the perfusate pH. The vagally induced intraluminal release of somatostatin occurring in aspirin‐treated animals was abolished by a low dose of atropine (0.05 mg kg‐1) or by a simultaneous infusion of prostaglandin E, (30 μg kg‐1 h‐1).
Effects of hay‐feeding on acid/base balance, renal sodium excretion, aldosterone and vasopressin secretion in the goat
Authors: ANDERSSON B. , ANDERSSON H. , AUGUSTINSSON O. , FORSGREN M. , HOLST H. , JÓNASSON H.
Published: December 2008

Effects of 30 min intense hay‐feeding on acid/base and sodium homeostasis were studied in semi‐starved goats during hyper‐ and euhydration. Parallel analyses of carotid and jugular blood samples revealed that feeding induced metabolic acidosis, which to some extent was subjected to respiratory compensation. The acidosis was accompanied by renal sodium retention and urinary acidification persisting for 2–3 h. The sodium retention was succeeded by an increase in renal Na excretion above the initial level. This natriuresis was most accentuated during hyperhydration. Blood samples taken for hormone assays during euhydration revealed a 15% increase in haematocrit and a significant rise in plasma aldosterone at termination of feeding. Inhibition of the water diuresis in hyperhydrated animals, and moderate increases in renal arginine vasopressin (AVP) excretion and plasma AVP were inconsistent effects of feeding. It is concluded, that simply jugular vein blood provides reliable information on the acid/base status of goats, but that the feeding schedule has to be considered in all experiments where small ruminants are used to investigate the integrated control of acid/base and sodium homeostasis.
Influence of water‐diuresis or saline volume expansion on deep nephron tubuloglomerular feedback
Authors: MÜLLER‐SUUR ROLAND , PERSSON A. ERIK G.
Published: December 2008

We have recently demonstrated the existence of a tubuloglomerular feedback mechanism in juxtamedullary nephrons in rat kidneys during antidiuresis. In the present experiments, we have investigated the influence of water‐diuresis on Munich Wistar rats and in homozygote Brattleboro rats. We have also observed the effect of saline volume expansion on the tubuloglomerular feedback of juxtamedullary nephrons in Munich Wistar rats. For comparison, the feedback mechanism was also studied in surface nephrons during water‐diuresis in Munich Wistar rats. Measurements of flow rate in the descending limb of Henle and single nephron glomerular filtration rate (GFR) using micropuncture at the renal papilla were performed, while the ascending limb was microperfused at varying perfusion rates with a modified Ringer solution. In surface nephrons early proximal flow rate, single nephron GFR and stop‐flow pressure was measured during microperfusion of the end‐proximal loop. No significant changes were measured in surface nephrons during water‐diuresis: the tubular flow rates, feedback responses, stop‐flow pressure and stop‐flow pressure changes were similar to those during anti‐diuresis. In juxtamedullary nephrons, Henle loop flow rate increases during water‐diuresis but the feedback‐mediated flow and single nephron GFR response curves obtained during microperfusion were unaltered compared to controls. Together, these results indicate that the feedback could be more activated during water‐diuresis than during control conditions. On the other hand, during saline volume expansion, reduced tubuloglomerular feedback sensitivity was found as shown earlier for surface nephrons. The reduction of tubuloglomerular feedback sensitivity therefore seems to be important in maintaining salt‐, but not water‐balance.
Is swimming exercise or cold exposure for rats?
Authors: HARRI M. , KUUSELA P.
Published: December 2008

Rats were trained by daily swimming sessions (up to 3 h per day) for at least 6 weeks in water at30, 36 and 38 oC. After this training, the adaptive changes obtained were compared with those typical of cold‐acclimated (cold‐specific changes) and running‐trained (training‐specific changes) rats. The most typical training‐specific change, an increased activity of oxidative muscle enzymes was negligible for swimming‐trained rats, while the lowered activity of muscle lactate dehydrogenase was evident for all trained groups. Cold‐specific changes, such as increased food intake, increased calorigenic response to injected noradrenaline, an increase both in mass and metabolic capacity of brown adipose tissue, and maintenance of the stores of ascorbic acid and muscle glycogen during cold exposure, were observed for rats trained at 36 and 30 oC. The cold tolerance test in cold air did not make any distinct difference between the rats trained at different water temperatures, while in cool water the 30 oC ‐swimmers were clearly superior to other groups, that is, their cooling rate was slowest. Other adaptive changes were found, to a variable extent, for all trained groups. These included loss of body fat, cardiac hypertrophy, reduced urinary catecholamine excretion after test swimmings either in cold or warm water, increased tail‐skin temperature response to isoprenaline, and a higher tail‐skin temperature in response to cold. Generally, however, the adaptive changes observed for 30‐ and 36 oC‐swimmers were similar, while the changes observed for 38 oC‐swimmers were different. The latter group neither displayed any cardiac enlargement nor any cold‐specific changes. The present results support the conclusion that the adaptive changes produced by swimming‐training in rats, more closely resemble those produced by cold‐acclimation rather than those resulting from running exercise.
TGF‐mediated oscillations in the proximal intratubular pressure: differences between spontaneously hypertensive rats and Wistar‐Kyoto rats
Authors: HOLSTEIN‐RATHLOU N.‐H. , LEYSSAC P. P.
Published: December 2008

A highly sensitive oscillatory tubulo‐glomerular feedback (TGF) response has previously been demonstrated in normotensive Sprague‐Dawley rats. The purpose of the present study was to examine whether such an oscillating TGF‐response could be elicited in Wistar‐Kyoto rats (WKY) and genetically hypertensive rats (SHR) and furthermore if any differences in the TGF‐response characteristics between SHR and WKY rats could be detected. The closed loop function of the TGF‐system was studied. In 12–18‐week‐old WKY rats regular oscillations in the intratubular pressure occurred spontaneously. The median frequency were 29.7 mHz (range 20–46.7 mHz). In SHR rats, spontaneous oscillations also occurred, but these were highly irregular. Spontaneous oscillations were more frequent in WKY than in SHR (88% vs. 54%). In both strains, oscillations could be elicited by free flow microperfusion with artificial tubular fluid (ATF). When furosemide was added to the ATF in a concentration of 0.1 mM, the oscillations were abolished in both strains of rats. It is concluded that, in both strains of rats, the oscillatory phenomena depend upon TGF activity. It is suggested that the irregular pattern of the oscillations observed only in SHR rats may represent a chaotic process.
Stimulation of acid formation by histamine, carbachol and pentagastrin in isolated pig parietal cells
Authors: NORBERG LAGE , LJUNGSTRÖM MAGNUS , VEGA FÉLIX V. , MÅRDH SVEN
Published: December 2008

Free cells were obtained by sequential incubations of pig gastric mucosa with pronase and collagenase. Approximately 10–15 % of the cell population represented parietal cells. Accumulation of aminopyrine (AP) in the acid compartments of parietal cells was used as an index of their acid production. Histamine, carbachol and pentagastrin each independently stimulated aminopyrine accumulation. The initial rate of aminopyrine accumulation, observed after addition of 10‐4 M carbachol or 10‐6 M pentagastrin, were 32% and 10%, respectively, of that observed with 10‐4 M histamine. Steady‐state aminopyrine accumulation in the presence of 10‐4 M histamine, 10‐4 M carbachol or 10‐6 M pentagastrin were 6.2 ± 3.3, 2.6 ± 0.6 and 3.0 ± 1.5 pmol APper 104 parietal cells, respectively (mean ± SD, n = 5). The EC50 value for histamine was 3.4 ± 1.4 ± 10‐7 M, AND for pentagastrin 5.9 ± 4.2 ± 10‐8 M (mean ± SD, n = 5). The dose‐response curve for carbachol was biphasic. A plateau was reached at 10‐5‐10‐4 M carbachol, and for this phase an apparent EC50 of 2.1 ± 1.4 ± 10‐6 M carbachol was calculated (mean ± SD, n = 5). A further increase to 10‐3 M carbachol increased the aminopyrine accumulation. Atropine (10‐6 M) inhibited the response to concentrations up to 10‐4 M carbachol, but was without effect on the histamine‐ and pentagastrin‐stimulation. The H2‐receptor antagonist, cimetidine, right‐shifted the dose‐response curve for histamine. Also, the pentagastrin‐stimulated aminopyrine accumulation was inhibited by cimetidine. In highly enriched parietal cells (80%) histamine, carbachol and pentagastrin separately stimulated the aminopyrine accumulation. It is therefore concluded that the pig parietal cells have receptors for these secretagogues.
The effects of tenotomy and compensatory hypertrophy on the postnatal development of soleus motor units in the cat
Authors: GOLLVIK L. , KELLERTH J.O. , ULFHAKE B.
Published: December 2008

Kittens, 5–7 days old, were subjected to tenotomy of either the soleus muscle or all its Achilles tendon synergists. When the cats had reached the adult stage, the physiological properties of the soleus motor units were investigated in both the atrophic and hypertrophic situations. Tenotomy resulted in a marked muscle weight loss, and overload due to tenotomy of synergists in a marked gain in muscle weight compared to the contralateral side. The motor units of the tenotomized soleus muscles exhibited a moderate shortening of the twitch contraction time, and also a change in twitch shape, related to the degree of atrophy. In the motor units of the hypertrophic soleus muscles, an increased fatiguability could be demonstrated. Further, in this group, there was a tendency towards differentiation of the normally uniform motor units into two groups with different features. The functional implications of this process are discussed. The development of motor units in both the tenotomized and the hypertrophic muscles were only marginally influenced by the operations, and it is concluded that the basic features of their development are largely unaffected by the functional manipulations imposed in the present study.
Evidence indicating trophic importance of IGF‐1 in regenerating peripheral nerves
Authors: HANSSON H. A. , DAHLIN L. B. , DANIELSEN N. , FRYKLUND L. , NACHEMSON A. K. , POLLERYD P. , ROZELL B. , SKOTTNER A. , STEMME S. , LUNDBORG G.
Published: December 2008

The mechanisms influencing regeneration of peripheral nerves are incompletely known, but growth factors are supposed to play a key role. In the present study, we demonstrate, with the aid of immunohistochemical methods, that somatomedin C (Sm‐C/insulin‐like growth factor I/IGF‐I) rapidly increased from low to high concentrations, reaching peak values in 2 weeks, in regenerating sciatic nerves of adult rats. In addition, IGF‐I was demonstrated extracellularly, never observed in the control nerves. Reactive Schwann cells appeared to be the major source for IGF‐synthesis. Higher concentrations were seen in tubulated nerves as compared to sutured ones. It is proposed that IGF‐I exerts important growth supporting effects on regenerating peripheral nerves.
Inhibitory effects of desmethylimipramine, metanephrine and normetanephrine on the neuronal and extraneuronal accumulation of catecholamines in fish spleen
Authors: UNGELL A.‐L.
Published: December 2008

The effect of desmethylimipramine, metanephrine and normetanephrine on the neuronal and extraneuronal accumulation of radiolabelled adrenaline and noradrenaline were studied in the perfused spleen of the teleost fish, Atlantic cod, Gadus morhua. Desmethylimipramine was found to be a potent inhibitor for the neuronal accumulation of both adrenaline and noradrenaline in the cod spleen, suggesting similarities with the neuronal uptake mechanism in mammals. Metanephrine was found to inhibit the extraneuronal accumulation of noradrenaline, though not that of adrenaline, while normetanephrine did not change the extraneuronal accumulation of any of the catecholamines. Both metanephrine and normetanephrine were more potent neuronal uptake blockers than extraneuronal. Metanephrine inhibited only the neuronal accumulation of adrenaline, while normetanephrine inhibited neuronal accumulation of both catecholamines. It is concluded that adrenaline and noradrenaline accumulate differently in the adrenergic neurons of the cod spleen as was suggested earlier for noradrenaline and tyramine (Nilsson & Holmgren 1976). It is also evident from the study that the uptake mechanisms or accumulation of catecholamines in lower vertebrates such as fish may be different from corresponding mechanisms in mammals.
Repeated exercise regulates glucose transport capacity in skeletal muscle
Authors: WALLBERG‐HENRIKSSON H.
Published: December 2008

The present study was undertaken to test the hypothesis that a muscle's habitual level of contractile activity might act as a long‐term regulator of glucose transport capacity. Rats were rendered severely diabetic by injection of streptozotocin, 125 mg kg‐1 body wt. Three days after the injection, insulin‐stimulated and contraction‐induced 3‐methylglucose transport in the in vitro epitrochlearis muscle preparation was reduced to 25% and 52% of control capacity, respectively (P < 0.001). However, when repeated i‐h swimming sessions (twice a day) were introduced during the 3 days of insulin deficiency, the reduction in contraction‐induced glucose transport capacity was completely abolished. This indicates that the habitual level of contractile activity of a muscle regulates its capacity for exercise‐stimulated glucose transport. Furthermore, one exercise session and a maximal insulin stimulus had an additive effect on 3‐methylglucose transport, suggesting that there are two pools of intracellular glucose transporters or two mechanisms for mobilizing the same pool.
Sympathetic nerve activity and central haemodynamics during mechanical ventilation with positive end‐expiratory pressure in rats
Authors: SELLDÉN H. , SJÖVALL H. , RICKSTEN S.‐E.
Published: December 2008

The aim of this study was to examine the effects of mechanical ventilation with increasing levels of positive end‐expiratory pressure (PEEP) on sympathetic nerve activity (SNA), cardiac output (CO), stroke volume (SV), heart rate (HR), central blood volume (CBV), total peripheral resistance (TPR), mean arterial pressure (MAP), pulse pressure (PP) and right and left atrial transmural pressure in chloralose anaesthetized rats before and after vagotomy. Changing ventilatory pattern from spontaneous breathing (SB) to artificial ventilation with to cm H2O PEEP in intact animals caused a significant fall in CO, SV and CBV (42,48 and 17%, respectively) and an increase in SNA, HR and TPR (90, 13 and 83%, respectively). The MAP increased slightly but significantly from 103 ± 4 to 107 ± 4 mmHg while PP decreased from 48 ± 2 to 37 ± 3, from spontaneous breathing (SB) to 10 cm H2O PEEP. Transmural left atrial pressure decreased significantly from 4.5 ± 0.3 to 3.0 ± 0.4 mmHg. After vagotomy, MAP and CO were significantly lower at 10 cm H2O PEEP and PP and SV were significantly lower at all levels of positive end‐expiratory pressure than the corresponding prevagotomy values. In spite of a greater fall in MAP and PP during PEEP after vagotomy, the absolute and relative increase of SNA was significantly lower compared to corresponding prevagotomy values. We conclude that reflex cardiovascular adjustments elicited by ventilation with PEEP are not solely due to unloading of arterial baroreceptors as has been claimed by others. Unloading of cardiac receptors with tonically active inhibitory afferents in the vagi is probably also of great importance for the excitation of the sympathetic nervous system during mechanical ventilation with PEEP.
Relaxation time during intermittent isometric contraction in subjects with different capacity for oxidative work
Authors: BERGSTRÖM M. , HULTMAN E.
Published: December 2008

Force and relaxation time were measured during intermittent electrical stimulation of the quadriceps muscle on 14 volunteers. Each stimulation had a duration of 1.6 s and the work to rest ratio was 1:1. Relaxation times increased during the first 20–30 contractions and then reached a plateau. The rate of increase in relaxation time during the first contractions as well as the plateau levels were found to correlate to maximal oxygen uptake capacity, predicted from submaximal cycle ergometer tests. Since slow‐twitch fibres are known to produce work at a lower energy cost it is suggested that studies of relaxation time changes could provide functional estimates of fibre‐type proportions in the quadriceps muscle.
Lack of effect of moderate hypoxaemia on human postural reflexes to skeletal muscle
Authors: HENRIKSEN O. , ROWELL L. B.
Published: December 2008

The effect of moderate hypoxaemia upon postural sympathetic vasoconstrictor reflexes in skeletal muscle was studied in five healthy young students, aged 20–30 years. The vasoconstrictor response to head‐up tilt was studied in brachio radial muscle kept at heart level and in the anterior tibial muscle. The local sympathetic veno‐arteriolar axon reflex was studied in the anterior tibial muscle placed at heart level and lowered 30–50 cm below heart level. Muscle blood flow was measured by the local 133Xe wash‐out technique. The measurements were carried out with the subject breathing atmospheric air and with the subject breathing 10–11% oxygen. No sign of orthostatic intolerance was seen during hypoxaemia as arterial blood pressure remained constant in the tilted position. Hypoxaemia did not alter the head‐up tilt induced vasoconstriction in brachio‐radial and anterior tibial muscles. The vasoconstriction elicited by the local veno‐arteriolar reflex was slightly reduced during hypoxaemia. The results suggest that central orthostatic vasoconstrictor reflexes to muscle are essentially normal during moderate hypoxaemia, but local veno‐arteriolar reflexes are slightly attenuated. This does not, however, significantly alter blood pressure control during head‐up tilt.
The influence of morphine, loperamide and naloxone on gallbladder response to prostaglandin E2 in the anaesthetized cat
Authors: JIVEGÅRD L. , SVANVIK J.
Published: December 2008

In experimental cholecystitis there is a net fluid secretion into the gallbladder lumen and an increased release of prostaglandins. Indomethacin and opiates are known to inhibit this mucosal fluid secretion. Intraluminal or intra‐arterial administration of prostaglandin E2 reduces basal gallbladder fluid absorption or induces a net fluid secretion to the lumen and also contracts the normal gallbladder. The use of a continuous perfusion technique in anaesthetized cats in this study shows that the effects of prostaglandin E2 on gallbladder function are blocked by intravenous morphine and loperamide. Naloxone does not affect the gallbladder responses to PGE2 administration. As a mechanism of action it is suggested that opiates inhibit secretory and contractile nerves that are activated by prostaglandins in the gallbladder wall. The findings suggest that the pain relieving effects of opiates in cholecystitis and biliary pain partly are due to blocking of the effects by prostaglandins on gallbladder function.
Carbon dioxide narcosis: influence of short‐term high concentration carbon dioxide inhalation on EEG and cortical evoked responses in the rat
Authors: FORSLID A. , INGVAR M. , ROSÉN I. , INGVAR D. H.
Published: December 2008

The effects of 1 min exposure to 80% CO2 inhalation was studied in rats under light general anaesthesia with N2O. It was found that 80% CO2 gave a rapid slowing of the EEG as well as a rapid decrease of the amplitude of cortical somatosensory evoked potentials. Only minor influences upon the blood pressure and heart rate were seen. The changes were found to be transient and most of the EEG effects had disappeared about 2–3 min following the end of the CO2 exposure. The findings are related to current procedures for preslaughter anaesthesia in swine using 80% CO2. The present experiments show that 80% CO2 rapidly induces an interruption of afferent sensory transmission to the cortex as well as slowing of the EEG. Both findings indicate that 80% CO2 is an effective agent for inducing adequate anaesthesia for slaughter procedures. However, the transient nature of the CO2 effects upon the central nervous system revealed here has to be taken into account to optimize the slaughter house procedures.
Adenosine potentiates the effects of LH and isoproterenol on luteal cells but not on isolated intact corpora lutea
Authors: BAUM M. SENDER , AHRÉN K.
Published: December 2008

Adenosine potentiated the stimulatory effect of luteinizing hormone (LH) in a dose‐dependent way on the production of cyclic AMP (cAMP) in isolated cells from heavily luteinized rat ovaries and from individual rat corpora lutea of various ages (2‐ and 5‐day‐old). Such an effect has earlier been reported only for cells from heavily luteinized ovaries (Behrman et al. 1983). A similar potentiating effect of adenosine was now seen on catecholamine‐stimulated cAMP production in isolated cells from 2‐day‐old corpora lutea. Adenosine did not, however, potentiate LH‐ or catecholamine‐stimulated cAMP production in isolated intact corpora lutea.,
Localized neural control of blood flow in the renal cortex of the anaesthetized baboon
Authors: SPELMAN F. A. , ÖBERG P.‐Å. , ASTLEY C.
Published: December 2008

Localized neural control of renal cortical blood flow was observed in five chloralose‐anaesthetized baboons. Renal artery blood flow was measured with an electromagnetic flowmeter, while superficial renal cortical blood flow was measured with a laser Doppler flowmeter. Stimulation of all renal nerve bundles isolated produced significant reductions in total renal blood flow, but reduced the superficial renal cortical blood flow only in localized areas. Systemic arterial blood pressure did not vary significantly, which suggests that the changes in renal cortical blood flow were neurally mediated and not the result of autoregulation. The renal cortical blood flow response was delayed 1–4 s with respect to the total renal blood flow response. The localization of flow control is consistent with the neuroanatomy of the kidney, and the delayed renal cortical blood flow response is consistent with the vascular anatomy of the kidney and with previous measurements of red cell transit times through the renal cortex.
Effects of synthetic human atrial natriuretic peptide (hANP) in conscious dogs
Authors: JOHANNESSEN A. C. , SCHÜTTEN H. J. , TORP‐PEDERSEN C. , WARBERG J. , BIE P.
Published: December 2008

The effects of synthetic human atrial natriuretic peptide (hANP) on arterial blood pressure, heart rate, and renal functions were evaluated in conscious trained dogs in moderate sustained water diuresis. Synthetic hANP was given i. v. over 3 min at doses of 0.27–2.16 μg kg‐1 body wt. It did not cause significant changes in blood pressure or heart rate. The rate of sodium excretion increased 20‐fold following 2.16 μg kg‐1 and 2.5‐fold after 0.54 μg kg‐1. Natriuresis was immediate and vanished after 10 min, regardless of dose. The concomitant increase in diuresis was less than 50%, but significant for a longer period of time. Increases in potassium excretion were significant, but small, that is, by a factor of 1.5–2.8. All natriuretic doses of hANP increased PAH clearance (at constant blood pressure), but some did so without measurably affecting creatinine clearance.
The effect of sodium load on the development of hypertension, plasma renin and kininogen in rats with renal artery constriction
Authors: PYYKÖNEN M.‐L. , YLITALO P. , KARP M. , NURMI A.‐K. , TIKKANEN I.
Published: December 2008

Effects of sodium load on the development of hypertension, plasma renin activity (PRA) and kininogen were studied in rats with renal artery constriction and untouched contralateral kidney. After the operation or sham‐operation, 0.9% NaCl or water were given as drinking fluid. A marked hypertension (systolic pressure > 150 mmHg) developed in all operated rats on saline, but only in 2/3 of operated rats on water. In none of the sham‐operated controls did systolic pressure exceed 150 mmHg during 7 postoperative weeks. Within the operated group on water, hypertensive rats had significantly higher PRA values than normotensive animals (P < 0.05). Salt load slightly suppressed the PRA in sham‐operated rats but not in animals with constricted renal artery, compared to sham‐operated controls on water. The operated rats on salt excess had higher plasma kininogen levels than the operated normotensive rats on water (P < 0.05), but there were no other significant differences in kininogen values between different study groups, regardless of whether blood pressure was increased or not. The results indicate that in this form of hypertension, the high blood pressure can be maintained without any increase in PRA if animals are subjected to a sodium load which sensitizes vascular beds to angiotensin. The increase in plasma kininogen, suggesting suppression of kallikrein‐kinin system, is unlikely associated with the increase of blood pressure.
The automatic computation of pressure‐derived maximal shortening velocity (Vmax) of the unloaded contractile element in the intact canine heart left ventricle
Authors: KETTUNEN R. , TIMISJÄRVI J. , KOUVALAINEN E. , RÄMÖ P. , LINNALUOTO M.
Published: December 2008

Estimation of the maximum velocity (Vmax) of the contractile element of the intact left ventricular wall muscle demands extrapolation of the force–velocity curve to zero load. The present paper describes our on‐line computation system for measuring and analysing pressure derived Vmax using both linear (Vmax_lin) and exponential (Vmax_exp) extrapolation methods. The developed pressure during isovolumetric phase of systole was used as an equivalent of the force. Testing on anaesthetized artificially ventilated dogs showed the exponential function to fit pressure‐velocity data better than the straight line did. The Vmax_exp attained 15–35% greater values than Vmax_lin, but both responded almost equally when considered on the basis of linear regression analysis (r= 0.991, n= 725). Changes of contractility caused by i. v. infusion of isoproterenol, calcium chloride or propranolol were practically similar when assessed by either method of Vmax computation, or by dP/dtmax. Volume loading by dextran infusion increased not only dP/dtmax, by 33 ± 13%, but also Vmax, up to 24 ± 11%. When arterial pressure was raised by phenylephrine infusion, or heart rate by atrial pacing, dP/dtmax increased significantly while Vmax remained unaltered. Hence, the linear and exponential extrapolation procedures provided comparable values for Vmax, but the linear one due to its simplicity is more suited for on‐line computation. The Vmax thus obtained is, however, not independent of the changes in preload.