bluuebunny/crossref_metadata_2025 huggingface dataset:
Nervous control of pancreatic exocrine secretion in pigs
Authors: HOLST JENS J. , De MUCKADELL OVE B. SCHAFFALITZKY , FAHRENKRUG JAN
Published: December 2008

The pancreatic secretion of fluid, bicarbonate and protein in response to electrical stimulation of the vagus and splanchnic nerves, to exogenous and endogenous secretin and to various pharmacological agents was studied in anesthetized young pigs (21 kg). Vagal stimulation increased flow, bicarbonate output and protein output in a frequency dependent manner; the half maximal effective frequency was 2–4 Hz and the maximal effective frequency 12 Hz. The secretory response to vagal stimulation was potentiated by physiological elevations of the arterial concentration of secretin brought about by injection of secretin or by acidification of the duodenal bulb. Simultaneous stimulation of the splanchnic nerves strongly inhibited the response to vagal stimulation; splanchnic nerve stimulation alone had no demonstrable effect. The flow and bicarbonate response to vagal stimulation was unaffected by atropine, but abolished by hexa‐methonium. Protein output was strongly inhibited by both agents. The response to intraarterial infusion of acetylcholine resembled that elicited by vagal stimulation but it was smaller and it was completely abolished by atropine and unaffected by hexamethonium. Alpha‐ and beta‐adrenergic blockade stimulated rather than inhibited the secretory response to vagal stimulation. The portal vein plasma concentration of secretin was not affected by vagal stimulation. The results indicate that the protein response, and the flow and bicarbonate response to vagal stimulation are not brought about by the same mechanism. An increased release of secretin is not involved. Peptidergic (VIP‐containing) nerves may contribute.
Decline and disappearance of taste response after interruption of the chorda tympani proper nerve of the rat
Authors: HELLEKANT G. , GOPAL V. , NINOMIYA Y.
Published: December 2008

The response amplitude in the chorda tympani proper nerve of rats to taste stimulation has been studied at different times after interruption of the nerve in the middle ear. The results show that the response in the nerve declined and disappeared completely within 15 h after the nerve was interrupted. As a first sign of deteriorating function a stage of hypersensitivity was observed. Results obtained during applications of local anesthetic or colchicine and section at different distances from the tongue indicate that the decreased response was the result of an interruption of axoplasmic flow from the nerve cell bodies in the geniculate ganglion to the taste buds.
In mice aggressive behaviour provokes vast increase in plasma renin concentration, causing only slight, if any, increase in blood pressure
Authors: BING JENS , POULSEN KNUD
Published: December 2008

In mice aggressive behaviour causes a vast release of renin, which can result in about 600‐fold increase in plasma renin concentration, reaching 6 Goldblatt Units, corresponding to 15μg renin per ml. This increase is mainly due to release of submaxillary renin, but there is also a significantly increased renal renin release. The degree of renin release is influenced by the duration of the aggression and by previous contact with other mice. Contrasting with the vast increase in plasma renin the blood pressure is normal or only moderately increased. This disproportion is not due to the depletion of renin substrate, caused by the increased renin, as shown by the increased calculated renin activity, as well as by decrease in blood pressure elicited by blockade of the renin system. Nor is the disproportion due to change in the sensitivity of the vessels to angiotensin II, the cause of this lack of tachyphylaxis being unknown. By way of exclusion the lack of pronounced increase in blood pressure can be explained by homeostatic function of the cardiovascular reflexes, which may also account for the fact that the pressor response after injection of pure submaxillary renin is only short, contrasting with a prolonged marked increase in plasma renin concentration.
Gastric acid secretion and water balance in the marine teleost Gadus morhua.
Authors: HOLSTEIN BJÖRN
Published: December 2008

Gastric acid secretion was measured in unanaesthetized codfish surgically equipped with a catheter draining the stomach. The pylorus was ligated. Without perfusion of the intestine, or during perfusion with pure sea water (100% SW) or slightly diluted (67%) SW, gastric acid secretion was low (< 10 μmol H+/kg‐h) and the fishes became dehydrated during the experiment. Perfusion of the intestine with 50% or 33% SW enabled the fishes to compensate for the water loss to the environment and greatly enhanced gastric acid secretion. Acid secretion was elevated also in fishes in which the dehydration was prevented by an intramuscular infusion of saline. Perfusion of the intestine (8.5 ml/h) decreased the hourly effluent volume (‘drinking rate’) from the stomach to almost zero within 2 h. The effect was independent of the degree of dilution of the perfusing SW, but was less pronounced when the perfusion rate was lowered. Intra‐muscular saline also depressed ‘drinking rate’. The acid secretion prevailing during perfusion of the intestine with SW at a dilution preventing dehydration–suggested to represent the basal acid secretion of the codfish– was inhibited by atropine, hexamethonium, and metiamide.
Synthesis of3H‐acetylcholine in the rabbit lacrimal gland and its release by electrical field stimulation
Authors: WIKBERG JARL E. S.
Published: December 2008

Electrical field stimulation was applied to the rabbit lacrimal gland during incubationin vitrowith3H‐choline, after which the efflux of tritiated metabolites was studied. In the presence of physostigmine3H‐acetylcholine was released into the incubation medium when the gland was stimulated electrically. The identity of the3H‐acetylcholine synthesized by the preparation was established by its identical ion exchange chromatographic properties to native acetylcholine. The tissue contents of3H‐acetylcholine and3H‐choline were 14.4 and 3.6%, respectively, of the total activities found in the gland. This study demonstrates that the rabbit lacrimal gland is innervated cholinergically. It is suggested that the method developed might be of value for studying effects of drugs on cholinergic neurotransmission in this organ.
PCO2 of the proximal tubular fluid and the efferent arteriolar blood in the rat kidney
Authors: Sohtell Morgan
Published: December 2008

Recordings in vivo of the carbon dioxide tension of the proximal tubular fluid and of the efferent arteriolar blood were performed with PCO2 microelectrodes in the rat kidney. The buffer lines of the efferent arteriolar blood and systemic arterial blood were determined with an ultramicro equilibration system and the acid‐base status of the systemic arterial blood was measured. The intratubular PCO2 was significantly higher than the PCO2 of the arterial blood, and the PCO2 of the efferent arteriolar blood was significantly lower than that of the arterial blood. The buffer capacity was higher and the bicarbonate concentration slightly lower for the efferent arteriolar blood than for the arterial blood. It is concluded that a PCO2 difference exists across the tubular wall and that the high intratubular PCO2 favours a chemical equilibrium of the carbonic acid‐bicarbonate system in the proximal tubular fluid. It is supposed that the slightly lowered bicarbonate concentration in the efferent arteriolar blood is an effect of the glomerular ultrafiltration process.
CO2 along the proximal tubules in the rat kidney
Authors: Sohtell Morgan
Published: December 2008

The proximal intratubular pH of the rat kidney was measured in vivo with an antimony electrode system. PCO2 and bicarbonate concentration of the proximal tubular fluid were determined with an ultramicro equilibration system. The tubular fluid to plasma inulin concentration ratio was evaluated by a microscope fluorometric method. The acid‐base parameters and the inulin concentrations were determined under control conditions and during acetazolamide treatment. The intratubular PCO2., was higher than the PCO2 of the systemic arterial blood under control conditions and the difference in PCO2 was increased during acetazolamide treatment. In acetazolamide treated rats the rate of fractional bicarbonate reabsorption was decreased in the early part of the proximal tubule, while it was of about the same in the middle and late parts as compared with control rats. The total bicarbonate reabsorption in the proximal tubule was reduced by 50% due to the carbonic anhydrase inhibition. It seems possible that the bicarbonate is still reabsorbed as CO2 after carbonic anhydrase inhibition, as hydrogen ion secretion is not totally stopped by this treatment. The increase in intratubular PCO2 after acetazolamide treatment is assumed to be due to an inhibition of the carbonic anhydrase facilitating effect on outward diffusion of CO2 from the tubular lumen across the cell wall.
Interrelationships between skeletal muscle adaptations and performance as studied by detraining and retraining
Authors: Houston Michael E. , Bentzen Henning , Larsen Henrik
Published: December 2008

The effects of 15 days of detraining and 15 days of retraining were studied in 6 well‐trained runners. Detraining resulted in significant decreases in the mean activities of succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) of 24 % and 13 %, respectively, but no significant increases in these enzyme activities occurred with retraining. Maximal oxygen uptake (VO2 max) decreased by 4% with detraining (p < 0.05), and increased by a similar amount with retraining. Performance time in an intense submaximal run decreased by 25% (p < 0.05) with inactivity, but still averaged 9% below the initial level after retraining. Maximal heart rate and peak heart rate during the performance run were higher after detraining by 4 and 9 beats per min, respectively (p < 0.05). With retraining, these heart rate values were decreased by 7 and 9 beats per min (p < 0.05). Blood lactate concentrations after the VO2 max and performance run were approximately 20% lower after detraining and retraining (p < 0.05). Muscle fibre areas for three subjects tended to be larger in biopsy samples taken after detraining and retraining. These data suggest that even short periods of detraining result in significant changes in indices of physiological capacity and function in subjects near their upper limit of adaptation, and that a longer period of retraining is necessary for muscle to re‐adapt to its original trained state.
Transcapillary passage of albumin, effects of tissue cooling and of increases in filtration and plasma colloid osmotic pressure
Authors: Rippe Bengt , Kamiva Akira , Folkow Björn
Published: December 2008

‘Initial’ clearance of radiolabeled serum albumin was measured in the perfused, maximally vasodilated muscle vascular bed of rat hindquarters during tissue cooling, during increases in filtration and during changes in serum colloid osmotic pressure. Albumin clearance during ordinary serum perfusion at iso‐gravimetry amounted to 0.03 ml/min x 100 g, increasing linearly with filtration rate to some 0.07 ml/minx 100 g at 0.5 ml/minx 100 g of filtration. During cooling from 36°C to 14°C both CFC and initial albumin clearance at isogravimetry decreased some 40%, in due proportion to the increased viscosity of the fluid. Increases of the colloid osmotic pressure of the perfusate correspondingly increased both the isogravimetric capillary pressure and ‘initial’ albumin clearance during isogravimetry. – It is concluded that even during isogravimetry the transmicrovascular albumin passage is to about 70 per cent due to filtration, and only some 30 per cent of transport at ordinary serum colloid osmotic pressures takes place by diffusion, both events presumably via ‘large pores’. There was no evidence that transendothelial vesicular transport should to any significant extent contribute to the passage of albumin from vessels to tissue.
ECG‐changes in the fetal Iamb during asphyxia in relation to beta‐adrenoceptor stimulation and blockade
Authors: Hökegård K.‐H. , Karlsson K. , Kjellmer I. , Rosen K. G.
Published: December 2008

Progressive changes in the S‐T interval of the fetal electrocardiogram (FECG) were studied in 14 lamb fetuses, acutely exteriorized and subjected to graded hypoxia. The aims of the study were to investigate whether beta‐adrenoceptor stimulation and hypoxia exerted additive or potentiating effects on the FECG and several cardiovascular parameters and whether the hypoxic changes of the FECG could be blocked by beta‐adrenoceptor blocking agents. The FECG changes were studied in order to correlate them with cardiovascular function, as measured by heart rate, mean arterial pressure, end diastolic pressure, maximum dP/dt and combined cardiac output, estimated by the thermodilution method, as well as with blood gases, acid base status, blood lactate and glucose. Injections of small doses (0.02 to 0.4 μg kg‐1 min‐1) of isoprenaline induced the same pattern of changes in the FECG as we have previously recorded during hypoxia. By increasing the isoprenaline dose an increase in the duration of the FECG changes and amplitude of the T‐wave changes was obtained. Propranolol was found to completely abolish the FECG changes induced by isoprenaline, as well as by mild hypoxia. During severe hypoxia the FECG changes could not be abolished by propranolol. Our previous findings indicated that the hypoxic changes could be regarded as a sign of myocardial glycolysis. Thus, the present finding that even small doses of isoprenaline given to the fetus, initiates the same pattern of FECG changes corroborate this hypothesis.
Metabolic effects of blood flow restriction in adipose tissue
Authors: Belfrage E. , Hjemdahl P. , Fredholm B. B.
Published: December 2008

The metabolic effects of blood flow restriction were studied in isolated blood‐perfused canine subcutaneous adipose tissue. Blood flow restriction (on the average to 20 per cent of control flow) was caused by either mechanical clamping of the arterial inflow or by i.a. injections of methoxamine or angiotensin. Glucose uptake in the adipose tissue was reduced during blood flow restriction. This was partially compensated for by a period of increased glucose uptake following restoration of flow. Blood flow restriction also caused an increase in the venous lactate/pyruvate ratio. The basal lipolytic rate was decreased during blood flow restriction. Lipolysis induced by brief (5 min) sympathetic nerve stimulation (4 Hz) was not inhibited by blood flow restriction as the total amount of glycerol released from the tissue was unaffected. The outflow rate was reduced during blood flow restriction, but glycerol trapped within the tissue was apparently not reutilized by the fat cells as it was released upon flow restoration. FFA outflow following nerve stimulation was, however, inhibited suggesting increased reutilization of FFA within the tissue. This increased reutiliza‐tion may ultimately be caused by the observed change in red./ox.‐balance and/or by the limited carrier capacity (albumin) available during blood flow restriction. Three main conclusions may be drawn from the present results. Firstly, plasma levels of glycerol and FFA do not necessarily reflect adipose tissue lipolysis at a given moment. Secondly, the decreased adipose tissue blood flow seems to be a major cause of the lowered FFA‐levels during hemorrhage. Thirdly, in contrast to hemorrhage, even severe reduction of adipose tissue blood flow is insufficient to cause irreversible ischemic damage.
Lack of specific prostaglandin antagonistic effects of 7‐oxa‐13‐prostynoic acid on ovarian metabolism in vitro
Authors: Magnusson Claes , Selstam Gunnar , Ahrén Kurt
Published: December 2008

Prostaglandins (PGs) have been proposed to function as obligatory intermediates in the action of luteinizing hormone (LH) (Kuehl et al. 1970). This was based on experiments on isolated mouse ovaries where the substance 7‐oxa‐13‐prostynoic acid (7‐oxa‐13‐PA) was found to block the effect of both PGE1 and LH on ovarian cyclic AMP formation and progesterone synthesis. We have studied whether 7‐oxa‐13‐PA acts as a PG antagonist also on the isolated rat ovary, where PGs of the E type have many effects. Prepubertal rat ovaries were incubated up to 4 h in modified Krebs bicarbonate buffer containing glucose with PGE1 and 7‐oxa‐13‐PA, alone and in combination. PGEj stimulated the uptake of the non‐utilizable amino acids a‐aminoisobutyric acid (AIB) and cycloleucine in an equally wide dose‐range as has earlier been found for the stimulation of lactic acid and cyclic AMP production as well as protein synthesis. 7‐oxa‐13‐PA alone, in concentrations exceeding 25 μMg/ml, stimulated lactic acid production, but inhibited the incorporation of labelled leucine and the uptake of AIB. The uptake of cycloleucine was slightly stimulated. 7‐oxa‐13‐PA did not antagonize the PGE1 effect on lactic acid production. 7‐oxa‐13‐PA diminished the PGE1 effect on the uptake of amino acids and the incorporation into protein, but only in concentrations where it in itself inhibited the protein synthesis. These results show that 7‐oxa‐13‐PA does not act as a PG‐antagonist in the prepubertal rat ovary, since it cannot block the effects of PGs without having marked inherent effects.
Apparent and true vascular resistances to flow in SHR and NCR kidneys as related to the pre/postglomerular resistance ratio
Authors: GÖTHBERG GUNNAR , LUNDIN STEFAN , RlCKSTEN SVEN‐ERIK , FOLKOW BJÖRN
Published: December 2008

In 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 Pt rises can so markedly distort the results of apparently precise in vitro comparisons of SHR and NCR renal vascular beds as to give entirely misleading results, with underestimations of the structurally based vascular hyperreactivity of the preglomerular section in SHR.
Lipoprotein‐lipase activity of human skeletal‐muscle and adipose tissue after intensive physical exercise
Authors: LITHELL HANS , HELLSING KRISTOFFER , LUNDQVIST GUDMAR , MALMBERG PER
Published: December 2008

Seven 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 levels.
Axonal transport of adrenaline, noradrenaline and phenylethanolamine‐N‐methyl transferase (PNMT) in sympathetic neurons of the cod, Gadus morhua
Authors: ABRAHAMSSON TOMMY
Published: December 2008

The 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 compared to PNMT.
Release of3H‐noradrenaline from the rat vas deferens under various in vitro conditions
Authors: ROSS SVANTE B. , KELDER DIANA
Published: December 2008

The 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 desipramine.
Different effects of furosemide on urinary excretion of prostaglandin E2and F2αin rabbits
Authors: OLIW ERNST , ÄNGGÅRD ERIK
Published: December 2008

The effect of a constant infusion of furosemide (130 μg/min i.v. for 60 min, n = 8) was studied on urinary excretion of water, electrolytes and immunoreactive prostaglandin E2(iPGE2) and iPGF2αin chloralose‐urethane anesthetized rabbits. During the furosemide infusion sodium and water excretion increased tenfold and the excretion of potassium and iPGE2two to three times. The excretion of iPGF2α(0.06 ± 0.03 μg/min/100 g kidney weight) was not significantly changed during the furosemide infusion but increased markedly after the infusion and reached a maximum (1.0 ± 0.6 μg/min/100 g) 30 to 45 min later, while the small increase in iPGE2excretion at this time could be attributed to cross‐reaction with PGF2αThe results indicate that PGE2might possibly be involved directly in the action of furosemide, while PGF2αmight participate in sodium and water conserving mechanisms in the rabbit kidney, activated by the drug induced diuresis.
Inhibition of renal sympathetic nerve traffic from cardiac receptors in normotensive and spontaneously hypertensive rats
Authors: RICKSTEN S.‐E. , NORESSON E. , THORÉN P.
Published: December 2008

The reflex inhibition of the sympathetic outflow to the kidney was examined during volume load with horse plasma in 6 normotensive rats (NCR) and 6 spontaneously hypertensive rats (SHR). The rats were anesthetized with chloralose and urethane. The arterial baroreceptors were denervated. The renal nervous inhibition was mediated via the vagal nerves and was mainly due to activation of receptors in the left side of the heart. The average thresholds in mean left atrial pressure for renal nervous inhibition was 5.4 mmHg for NCR and 9.2 mmHg for SHR indicating a clear resetting of the reflex arch in the hypertensive animal: The reason is probably a decreased distensibility of the wall of the left atrium due to a chronic elevation of left atrial pressure. This resetting of the atrial receptors in the hypertensive animals is probably of importance to allow an adequate filling pressure of the hypertrophied left ventricle and might also be of importance for the reflex neural control of renal function in these animals.
The effect of glucagon, dibutyrylic cyclic AMP and theophylline on bile production in the cat
Authors: LARSEN JENS ANKER , KRARUP NIELS , THOMSEN OLE Ø.
Published: December 2008

The effect of glucagon, dibutyrylic cyclic AMP and theophylline on bile production and liver metabolism was studied in fasting, chloralose anesthetized cats. After 45 min infusion of glucagon (0.1 μg/kg/min) total bile flow started to increase and finally reached a level 32% above control bile flow. The rise in flow was accompanied by a parallel increase in the biliary clearance of erythritol and the rate of biliary excretion of inorganic ions, whereas the bile acid excretion remained constant. Glucagon therefore appears to stimulate selectively the bile acid–independent canalicular production of bile. In contrast to the delayed action on bile production, glucagon caused an immediate change in liver metabolism as judged from the elimination rate of ethanol and the rise in plasma glucose concentration. Dibutyrylic cyclic AMP or theophylline also caused similar immediate changes in liver metabolism but neither substance influenced bile production or the biliary excretion of electrolytes or bile acids. It thus appears that glucagon cholere–sis in the cat is either independent of cAMP release or that an increase in intracellular cAMP is not in itself sufficient to influence bile secretion. The results also seem to exclude that an increase in insulin production induced by hyperglycemia, or hemodynamic changes in the liver, can explain glucagon choleresis.
Metabolic responses in feline “red” and “white” skeletal muscle to shock and ischemia
Authors: JENNISCHE EVA , AMUNDSON BJÖRN , HALJAMÄE HENGO
Published: December 2008

In order to investigate possible differences in the reaction to hypoxic conditions between “red” and “white” skeletal muscle, cats were subjected to a 2 h period of either hemorrhagic shock or hind limb tourniquet ischemia, and the hypoxia induced changes were studied in the soleus and lateral gastrocnemius muscles. Muscle biopsies were analysed for ATP, CP, glucose, G 6–P and lactate. Using microelectrodes, the resting membrane potential was repeatedly measured. Both experimental models resulted in increased tissue lactate levels and a successive decrease in the membrane potential of both muscles studied. No reduction of the high energy phosphagen content (ATP+CP) occurred in any of the muscles during shock. The tourniquet ischemia resulted in a 40% reduction of the ATP+CP content in the soleus muscle, whereas in the gastrocnemius muscle no significant reduction occurred. A significant correlation was found between the tissue lactate content and the membrane potential under both conditions and in both muscles studied. It is concluded that “red” muscles are more susceptible to metabolic derangement than “white” muscles during total ischemia, whereas during hypovolemia “red” muscles appear to be protected from early hypoxic damage, probably due to a redistribution of skeletal muscle blood flow.
Local versus regional cerebral blood flow in the rat at high (hypoxia) and low (phenobarbital anesthesia) flow rates
Authors: ABDUL‐RAHMAN ALI , DAHLGREN NILS , INGVAR MARTIN , REHNCRONA STIG , SIESJÖ BO K.
Published: December 2008

Local cerebral blood flow (CBF) was measured in rats, using an autoradiographic technique with 14C‐iodoantipyrine as diffusible tracer, in situations with low, normal and high flow rates (phenobarbital anesthesia, analgesia with 75% N2O, and hypoxia, respectively). A comparison of the results with previous data obtained in conscious rats (Sakurada et al. 1978) demonstrates that 75 % N2O moderately reduces local CBF in some, but not all, cortical and subcortical areas, that phenobarbital anesthesia reduces local CBF to between 30 and 65 % of (conscious) control, and that pronounced hypoxia (arterial Po2 about 25 mmHg) increases local CBF 3‐ to 4‐fold. A comparison of the values obtained for cortical structures with those previously measured with a technique based on the Fick principle shows that the autoradiographic technique gives similar values at low and normal flow rates but that it moderately underestimates CBF at high flow rates, probably due to diffusion limitation.
The effect of vasodilatation and sympathetic nerve activation on net water absorption in the cat's small intestine
Authors: BRUNSSON INGEMAR , EKLUND STEFAN , JODAL MATS , LUNDGREN OVE , SJÖVALL HENRIK
Published: December 2008

The rate of net water uptake from the feline small intestine has been investigated during control conditions, during graded infusions of the vasodilator drug isopropylnoradrenaline, and during electrical stimulation of the regional sympathetic nerve fibres to the gut. Net water absorption rate was largely unaffected by intestinal vasodilatation. The fraction of the absorbate transported via the lymphatics remained also constant at 20–40% of the total absorption regardless of blood flow rate. Stimulating the sympathetic nerve fibres to the small intestine increased, however, net water absorption rate. The increase was particularly pronounced when blood pressure was kept constant during the period of stimulation. The absorption rate was on an average almost doubled at a stimulation frequency of 8 Hz during constant pressure conditions. The mechanism(s) explaining this nervous control of water absorption are tentatively discussed.
Renin, aldosterone and Cortisol during ethanol intoxication and hangover
Authors: LINKOLA JAAKKO , FYHRQUIST FREJ , YLIKAHRI REINO
Published: December 2008

The effect of ethanol intoxication and hangover on plasma renin activity (PRA), plasma aldosterone (PA) and plasma Cortisol (PC) concentrations was studied in 7 healthy supine men in controlled clinical conditions during 18 h beginning at 6 p.m. Large individual variation was observed in the response of PRA, PA and PC to ethanol. Following ethanol, stimulation of PRA was observed at the 14th and the 16th hour (P<0.05), of PA at the 4th and the 6th hour (P<0.01 and P<0.05, respectively) and of PC at the 4th and the 14th hour (P<0.01 andP<0.05, respectively). Ethanol ingestion suppressed PC during the first hour (P<0.02). Water ingestion at 8 a.m. suppressed PA between the 14th and the 16th hour (8–10 a.m.) in control and ethanol experiment (P<0.01 and P<0.005, respectively). There was a dissociation between PRA and PA, but intra‐individually PRA and PA correlated fairly or well. Plasma arginine vasopressin (AVP) and PC were also significantly correlated. The results suggest that changes in PA and PC as well as the dissociation of PRA and PA after ethanol ingestion might be partly related to dehydration and to the increased secretion of hypothalamic and pituitary hormones as well as to sodium and potassium balance. There was a biphasic effect of ethanol, including an initial suppression of PC and a subsequent increase of PC, PRA and PA. Upright posture appears to exaggerate the stimulating effect of ethanol on PRA, PA and PC.
The effect of centrally administered TRH on blood pressure, heart rate and ventilation in rat
Authors: KOIVUSALO F. , PAAKKARI I. , LEPPÄLUOTO J. , KARPPANEN H.
Published: December 2008

Different doses (3, 16, 80, 400 and 2000 ng per rat) of TRH or alternatively saline were infused into the lateral ventricle of urethane‐ahaesthetized rats and blood pressure, heart rate, respiration rate and tidal volume were recorded. A dose of 3 ng TRH caused a significant elevation of blood pressure and heart rate, whereas 16 ng was needed for respiration rate to be elevated. There was no change in respiratory minute volume during the experiment. We conclude that TRH has profound physiological effects and that TRH, given centrally, is a potent hypertensive, chronotropic and tachypnoeic agent.
‘Distensibility’ of the papaverine‐relaxed vascular bed in human subcutaneous tissue
Authors: HENRIKSEN O. , KRISTENSEN J. K.
Published: December 2008

The effect of an increase in vascular transmural pressure upon the blood flow in two subcutaneous vascular beds, maximally dilated by papaverine was studied in 6 healthy humans. Blood flow was measured on the dorsum of the hand and at the lateral malleolus by the local133Xe washout technique. Increase in vascular transmural pressure was induced by lowering the labelled area various distances below heart level. Lowering the area caused an increase in blood flow. The increase was less pronounced in the legs than in the hand. As arterial perfusion pressure head remained constant during lowering, this indicates that the relative decrease in vascular resistance was smaller in the leg than in the hand. Experimental edema did not influence the relative decrease in vascular resistance. The results suggest that ‘distensibility’ of the resistance vessels is smaller in the leg than in the hand. This might be due to a structural adaptation of the vascular wall in vessels often subjected to increased hydrostatic pressure.
Regional blood flow in canine myocardium as determined by local washout of a freely diffusible radioactive indicator
Authors: HAUNSØ STIG , AMTORP OLE , LARSEN BJØRN
Published: December 2008

The aim of this study has been to examine the utility of the washout of a freely diffusible radioactive indicator as a measure of regional myocardial blood flow in open‐chest anesthetized dogs. The method employed was direct intramyocardial injection of Xenon‐133 followed by measurement of its gamma‐radiation. The experimental washout curves show, after a short acceleration period, monoexponential washout of the indicator over two decades. We found indications of insignificant veno‐arterial shunting by diffusion of the blood flow level measured, insignificant arterial recirculation of the indicator, and minimal radioactive contribution to precordial residue versus time curves arising from right heart or non‐myocardial tissue. We suggest that diffusion equilibrium between the tissue in the counting field and the blood leaving it is maintained during the linear down slope of two decades of the clearance curve, and that local blood flow can be calculated from washout rate constant obtained from this part of the curve. The method employing intramyocardial injection of Xenon‐133 was found to give the same results as atraumatic epicardial labelling indicating negligible effect of the injection trauma and supporting the validity of the local injection method using small volumes (2–10 μl).
Regional changes in monoamine synthesis in the developing rat brain during hypoxia
Authors: HEDNER T. , LUNDBORG P.
Published: December 2008

4, 14 and 28 days old rats were exposed to a hypoxic environment of 6% O2‐94% N2 for 30 min. Tyrosine hydroxylase and tryptophan hydroxylase acivity was studied in different brain regions (hemispheres, striatum, midbrain and brainstem) in vivo by measuring the accumulation of dihydroxyphenylalanine (Dopa) and 5‐hydroxytryptophan (5‐HTP) respectively, after inhibition of aromatic L‐amino acid decarboxylase with NSD 1015. Tyrosine and tryptophan levels in the different brain regions were measured simultaneously. The tyrosine and tryptophan levels in the various brain parts were generally not influenced during exposure to hypoxia. Tyrosine hydroxylase activity decreased in most areas in the 4 and 14 days old rats, and all brain areas studied in the 28 days old rats. Tryptophan hydroxylase activity decreased markedly in all brain areas at all ages studied. It is concluded that the enzymes tyrosine hydroxylase as well as tryptophan hydroxylase seem to be equally affected during hypoxia in the different brain regions studied.
Renal proximal tubular acidification. Role of brush‐border and cytoplasmic carbonic anhydrase
Authors: KARLMARK BERTIL , ÅGERUP BENGT , WISTRAND PER J.
Published: December 2008

Carbonic anhydrase is found in the cytoplasm and brush border membranes of renal proximal tubular cells. Both the soluble and the membrane‐bound enzyme have been assigned roles for the secretion of hydrogen ions into the tubular fluid and hence also for the reabsorption of bicarbonate. Attempts were made to differentiate between the roles of these enzymes for the rate of proximal tubular acidification. Proximal tubules of rats were instilled and perfused with bicarbonate solutions containing carbonic anhydrase inhibitors, especially designed to be impermeable to cell membranes. The acidification rate was measured with an antimony micro‐electrode system–the only instantly responding micro‐pH electrode. The membrane impermeable inhibitors had no effect on this rate in contrast to acetazolamide, which markedly inhibited the acidification rate when administered in‐traluminally. It is therefore concluded that the cytoplasmic carbonic anhydrase is the important enzyme for the proximal tubular acidification rate, and hence the rate of bicarbonate reabsorption. The function of the brush border enzyme remains an outstanding problem.
Temperature compensation of sodium transport and ATPase activity in frog skin
Authors: LAGERSPETZ K. Y. H. , SKYTTÄ M.
Published: December 2008

Na+ transport across frog skin, measured as short‐circuit current (SCC) shows perfect temperature compensation in frogs acclimated to 6°, 12°, and 23°C as SCC values observed at the acclimation temperatures are equal (about 13 μA/cm2). Reacclimation experiments show that this is not a starvation effect. While very little temperature compensation is seen in the activity of Na+, K+‐ATPase in epidermal homogenates from frog skins, the activity of Mg2+‐ATPase shows inverse compensation at assay temperatures from 4o to 48oC. This ATPase is apparently activated either by Mg2+ or by Ca2+ and it probably controls the passive permeability of epidermal cells. It is suggested that the inverse temperature compensation in the activity of this enzyme is the main mechanism by which the observed perfect temperature compensation of Na+ transport across frog skin occurs.
Cardiovascular ‘reactivity’ to graded splanchnic nerve stimulation in spontaneously hypertensive and normotensive control rats
Authors: NORESSON EDDY , FOLKOW BJÖRN , HALLBÄCK‐NORDLANDER MARGARET A
Published: December 2008

Cardiovascular ‘reactivity’ to graded splanchnic nerve stimulations was compared in adult spontaneously hypertensive rats (SHR) and normotensive controls (NCR), during abolished adrenal medullary secretion and neurogenic cardiac control and depressed reflex vascular adjustments. Arterial pressure, heart rate and cardiac output were measured, and total peripheral resistance (TPR) and stroke volume (SV) computed before, during and after nerve stimulation. The neurogenic resistance increases in the major gastrointestinal‐renal‐hepatic circuits expressed themselves as TPR elevations, which were much accentuated in SHR. This reflects an increasedw/r1of SHR resistance vessels rather than any altered effector sensitivity, since the responses were particularly accentuated at high discharge rates when noradrenaline junction concentrations approach maximal levels. The splanchnic capacitance responses expressed themselves as SV increases, being the most relevant aspect of capacitance control. SV increased less in SHR, mainly reflecting the reduced diastolic compliance of the hypertrophied SHR left ventricle and the consequent rightward shift of its Frank‐Starling curve. The results indicate that an elevated resistance may well be maintained by a normal sympathetic discharge in established SHR hypertension. There seems, however, to be an increasing need for accentuated discharge to the capacitance side to maintain proper cardiac filling of the hypertrophied left ventricle.
Renal function in hypercalcemic dogs during hydropenia and during saline infusion
Authors: LINS LARS‐ERIC
Published: December 2008

The effects of calcium‐gluconate infusions on renal function were studied in unanesthetised dogs. Each dog was studied during hydropenia and saline infusion. Hypercalcemia, mean serum calcium 3.85 mmol/1 (hydropenia) and 3.62 mmol/1 (saline infusion), increased fractional excretion of sodium (CNa/CIn), calcium (CCa/CIn), and magnesium (CMgCIn). The increase was significantly higher in saline‐expanded dogs than in hydropenic dogs. Fractional excretion of potassium (CK/CIn) was increased in hydropenia but remained unchanged in saline‐expanded animals. Fractional excretion of phosphate (CP/CIn) was not consistently changed by hypercalcemia. Fractional excretion of chloride (CCl/CIn) was markedly increased in saline‐expanded dogs but was not changed in hydropenia. Urine osmolality was reduced in hydropenic dogs but unchanged in saline‐expanded dogs. In hydropenic as well as in saline‐expanded dogs tubular reabsorption of solute‐free water (TcH2O/CIn) increased during the first hour of hypercalcemia. In hydropenic dogs hypercalcemia caused a slight but significant decrease in blood pH, standard bicarbonate, and base excess. In hydropenic as well as in saline‐expanded dogs glomerular filtration rate (CIn), renal plasma flow (CPAH), and filtration fraction were unaffected.
Adrenergic and novel non‐adrenergic neuronal mechanisms in the control of smooth muscle activity in the human oviduct
Authors: LINDBLOM B. , LJUNG B. , HAMBERGER L.
Published: December 2008

The isthmic portion of human Fallopian tubes was excised during surgery and the ampullary‐isthmic junction was identified. The external, longitudinal and the inner, circular muscle layers of this structure were then mechanically separated. The contractile activity of thin strips from these layers was studied isometrically in organ bath experiments. Administration of various adrenoceptor agonists and antagonists revealed that the responses of the longitudinal smooth muscle are primarily mediated by a‐adrenoceptors while there is a marked dominance of β‐adrenoceptor‐mediated effects in the circular layer. Transmural nerve stimulation caused neurogenic responses similar to those caused by exogenous noradrenaline, although nerve‐mediated inhibition of circular muscle activity was not abolished entirely by propranolol, atropine or guanethidine, but by tetradotoxine, indicating the existence of a hitherto unknown non‐adrenergic, non‐cholinergic, inhibitory neurogenic mechanism. The results support the concept of a specific sphincter‐like function controlling ovum transport at the human oviductal isthmus, and that this sphincter may be controlled by both adrenergic nerves and nerves liberating an unidentified transmitter substance.
Electromechanical delay in skeletal muscle under normal movement conditions
Authors: NORMAN ROBERT W. , KOMI PAAVO V.
Published: December 2008

Electromechanical delays (EMD), the time from onset of EMG activity to change in acceleration or deceleration of the forearm, were studied in concentric and eccentric contractions of biceps and triceps brachii muscles. Horizontal flexion and extension movements were performed at varying speeds by 10 subjects. EMD time in concentric contractions for biceps was 41 ± 13 ms and for triceps was 26± 11 ms and was not influenced by the velocity of the movement. In eccentric contractions at the slower velocity the biceps EMD time was 38±13 ms and shortened to 28±10 ms at the faster velocity. The eccentric triceps EMD, however, was not significantly altered by movement velocity and averaged 30±7 ms. The data provided support for the hypothesis that stretching of the series elastic component, to a point where muscle force can be detected, is the primary determinant of the EMD phenomenon. However, there are complex interactions of the effects on EMD of muscle fiber type composition, whether the contraction is concentric or eccentric, and the velocity of the movement as well as possible gamma system influence. These complications require that consideration of electromechanical delay be made when phasic relationships between muscle force or joint torque generation from different muscles are inferred from EMGs.
Release of gastrin from the skeletal muscles and from the antral mucosa in cats induced by sulfonuric drugs
Authors: UVNÄS‐WALLENSTEN KERSTIN , EFENDIC SUAD , UVNAS BÖRJE , LUNDBERG JAN M.
Published: December 2008

The present observations indicate that sulfonuric drugs release gastrin both from peripheral nerves in striated muscles and from endocrine‐like cells in the gastrointestinal tract. Gastrin appears in perfusates of extirpated cat legs after administration of tolbutamide or glibenclamide (5–50 μg/kg or 5–500 μg/kg perfused tissue respectively) to the perfusion medium. Furthermore gastrin is released into the portal vein of cats after i.v. administration of glibenclamide (5–50 μg/kg). The finding that sulfonuric drugs not only release insulin from β‐cells in the pancreas, but also gastrin from gastrin producing cells in the stomach as well as from nerve fibers in the skeletal muscles, indicate that sulfonuric drugs have more wide spread effects than previously assumed. Possible consequences of the drug induced release of peptides from peripheral nerves as well as of the release of gastrin from the gastrointestinal tract are discussed.
Dynamics of beta adrenoceptor induced amylase release and cyclic AMP accumulation in the guinea pig submandibular gland
Authors: CARLSÖÖ BENGT , DANIELSSON ÅKE , HENRIKSSON ROGER , IDAHL LARS‐ÅKE
Published: December 2008

The dynamics of amylase release from the guinea pig submandibular gland were studied in vitro by applying a multi‐channel microperifusion set. This technique makes it possible to measure time related enzyme release more accurately and to take samples of perifused tissue at short intervals. Stimulation of the ^‐adrenoceptor with norepinephrine gives rise to a rapid initial enzyme discharge, detectable within 15 s. Administration of propranolol inhibits enzyme release, which is not restored after removal of the agent. Simultaneous measurements of tissue cyclic AMP during norepinephrine stimulation at various time intervals display a significant increase of cAMP as early as 15 s after stimulation of secretion. This increase of cAMP thus coincides with the discharge of amylase. In addition, cAMP continuously accumulates during 30 min of norepinephrine perifusion of the slices. The present study describes a valuable tool with high sensitivity for visualizing the relations between enzyme secretion from the salivary gland and the intracellular biochemical processes. The data obtained further indicate a close correlation between amylase and cAMP during the initial phase of enzyme discharge.
Effect of substance P on CCK‐ or VIP‐induced choleresis in anesthetized dogs
Authors: (HOLM) INGER MAGNUSSON , THULIN LARS
Published: December 2008

10 anesthetized dogs were provided with acute common bile duct fistulas and the gallbladder was excluded. Hepatic bile output and biliary content of sodium, potassium and amylase were studied. 6 caval infusions were administered of CCK, 0.3 Ivy U‐kg‐1 min‐1, with a superimposed infusion of SP, 20 ng kg‐1 min‐1. 7 caval infusions were given of VIP, 50 ng‐kg‐1 min‐1, with a superimposed infusion of SP, 20 ng·kg‐1 min‐1. CCK increased bile output and biliary content of sodium, potassium and amylase by 78–110%. The corresponding increase induced by VIP was 55–85%. Biliary pH was not influenced. SP abolished the effects of both CCK and VIP. It is suggested that all peptides studied influenced canalicular bile secretion by changing the electrolyte excretion.