bluuebunny/crossref_metadata_2025 huggingface dataset:
Sodium balance during development of hypertension in the spontaneously hypertensive rat (SHR)
Authors: LUNDIN STEFAN , HERLITZ HANS , HALLBÄCK‐NORDLANDER MARGARETA , RICKSTEN SVEN‐ERIK , GÖTHBERG GUNNAR , BERGLUND GÖRAN
Published: December 2008

Sodium balance was studied in 7 and 16 week old male spontaneously hypertensive rats (SHR), in matched normotensive Wistar rats (NCR) and in Wistar Kyoto rats (WKR). The animals were placed in metabolic cages and given diets with either normal sodium content (5.35 mmol sodium/100 g food) or with a sodium content 3 or 10 times the normal. Whether on normal or increased sodium diet we did not observe any increased sodium retention in either SHR age group. However, in both SHR groups urinary sodium excretion was significantly decreased, while faecal sodium excretion was correspondingly increased compared with the controls. This shift of sodium excretion from kidneys to gastrointestinal tract in SHR did not reflect any ‘primary’ inability of the SHR kidneys to excrete sufficient sodium amounts since on high sodium diet they excreted the increased sodium load as readily as the normotensive controls. The present results do not support the concept that a primary renal retention of sodium and water should be of pathogenetic importance for the SHR variant of primary hypertension.
Spontaneous contractility of isolated muscle layers of the pig oviductal isthmus
Authors: RODRIGUEZ‐MARTINEZ HERIBERTO , EINARSSON STIG
Published: December 2008

A new dissection technique for the mechanical separation of the smooth muscle layers of the pig oviductal isthmus is described. The spontaneous contractility of the isolated muscle layers was recorded using transducers designed to reflect the proper force development of the tubal muscle tissue specimens under in vitro conditions. A series of well defined stages of the entire estrual cycle was surveyed, and the isolated tubal muscle contractility was compared with that of the intact isthmus, according to previous work. The circular and longitudinal layers are both active during the estrual cycle, showing definite patterns in each stage explored. The circular layer revealed a changing pattern similar to, but of lower activity than, the intact isthmus, specially during the heat, post ovulation and luteal phases. The periods are considered relevant because, during heat, the spermatozoa might be actively transported through the isthmus by the concerted contractions and relaxations of the circular muscles. The same would happen during the luteal phase, specially during the time the ova are descending into the uterus. As important would be the postovulation time, during which the sustained contraction of the circular layer could “lock” the ithmic lumen, thus preventing improper timing of ova descent. The longitudinal layer follows the intensity of the contraction patterns of the circular layers, being specially active during the periovulatory period.
Electrical and mechanical responses of the intact rabbit heart in relation to the excitation interval A Comparison with the Isolated Papillary Muscle Preparation
Authors: WOHLFART BJÖRN , ELZINGA GIJS
Published: December 2008

Experiments were performed on anesthetized open thorax rabbits with complete heart block and on isolated papillary muscles from rabbit hearts. Both preparations were basically paced at 1.0 Hz. Two consecutive test stimuli (denoted 1 and 2, respectively) were applied at various intervals. Action potentials were recorded; using suction electrodes in the intact heart and microelectrodes in the isolated tissue. Peak rate of rise of left ventricular pressure (DP) and of isometric force (DF, in vitro) were taken as measures of the contractile response. Action potential duration (AP), at 50% repolarization, were longer in vivo (175 ms) than in vitro (130 ms). AP and DP (DF) of the test contractions were similarly related to the test pulse intervals in the two preparations. DP2was significantly correlated with DP1and AP1(r: 0.92–0.96). The regression coefficient for the dependence of DP2on DP1was significantly greater in vivo (0.61) than in vitro (0.21). This was interpreted to mean that recirculation of activator calcium from one heart beat to another was greater in vivo than in vitro. The isolated tissue would therefore be more dependent on calcium entering during the action potential. This could explain the greater postextrasystolic potentiation in vitro than in vivo (255% and 141% of steady state‐responses, respectively).
The importance of an intact sympathetic innervation for the differentiation of the β‐adrenoceptor subtypes in the rat parotid gland
Authors: DANIELSSON ÅKE , HENRIKSSON ROGER , LINDSTRÖM PER , SEHLIN JANOVE
Published: December 2008

Acinar cells of the rat parotid gland are in intimate contact with adrenergic nerves, arousing from the ganglion cervicale superior (Bloom et al. 1977). The sympathetic nerves or circulating catecholamines exert their effects by activating α‐adrenoceptors (electrolyte and water secretion) or β‐adrenoceptors (enzyme secretion) (Batzri et al. 1971, Carlsöö et al. 1981). It is now well established that the β‐adrenoceptors can be divided in two subclasses, β1and β2, present in different proportions depending on the tissue examined (Lands et al. 1967, Carlsson et al. 1972, Barnett et al. 1978, Minneman et al. 1979a). The concentrations of the two subtypes are regulated independently (Minneman et al. 1979b) and their molecular structure seems to be different (Venter et al. 1981). The β1, ‐subtype is dominating in normal rat parotid glands (Carlsöö et al. 1981, Ludford & Talamo 1980). Supersensitivity occuring in salivary glands after interruption of the sympathetic nerve supply in adult animals is usually associated with an increased number of the β‐adrenoceptors (Ludford & Talamo 1980, Stefano & Perec 1981). In the present work we have studied the effect of neonatal sympathetic denervation of the rat parotid gland on the binding of the β‐adrenoceptor radioligand3H‐dihydroalprenolol (3H‐DHA) and on the β‐adrenoceptor‐induced amylase secretion. The results suggest that the normal dominance of the β1‐adrenoceptors is lost after neonatal sympathetic denervation. Hence, an intact sympathetic nervous system may be of major importance during the development of the β‐adrenoceptor population.
Intracisternal administration of avian pancreatic polypeptide lowers respiration rate and enhances the clonidine induced reduction of respiration rate in α‐chloralose anesthetized rats: Possible interactions with an α2‐adrenergic receptor
Authors: FUXE KJELL , AGNATI LUIGI F. , HÄRFSTRAND ANDERS , LUNDBERG JAN , HÖKFELT TOMAS , CALZA LAURA , KIMMEL JOE , BERNARDI PASQUALE
Published: December 2008

Avian pancreatic polypeptide (APP) is a 36 amino acid peptide isolated from chicken pancreas (Kim‐mel et al. 1975) and there exists a wide‐spread distribution of APP‐like immunoreactive nerve cell bodies and terminals in the central and peripheral nervous systems (Lorén et al. 1979, Hökfelt et al. 1981). Furthermore, it has recently been discovered (Lundberg et al. 1980a) that an APP‐like immunoreactive substance (Kimmel et al. 1975) is present in central phenylethanolamine‐N‐methyltransferase (PNMT) immunoreactive neurons and in some noradrenaline (NA) neurons. Thus, an APP‐like peptide and adrenaline (A) may coexist in some A nerve cells in the central nervous system (see also Hunt et al. 1981). This coexistence appears to exist in A nerve cells of both cell groups C1 and C2 (Hökfelt et al. 1974, Lundberg et al. 1980a). Evidence exists that many of the A neuron systems of the brain represent vasodepressor pathways, and it has been suggested that clonidine may produce at least part of its hypotensive actions via activation of postsynaptic α2‐adrenergic receptors linked to A synapses in the brain, especially in the medulla oblongata (Bolme et al. 1974, Fuxe et al. 1975, Fuxe et al. 1980). It has also been suggested that certain A neurons regulate respiration rate and the clonidine induced reduction of respiration rate may therefore at least in part be mediated via α2‐adrenergic receptors linked to A synapses in the medulla oblongata (Bolme et al. 1974). In order to understand the possible functional significance of co‐storage of APP‐like material and A we have now investigated the effects of APP and for comparison also bovine pancreatic polypeptide (BPP) (Chance & Jones 1974), which differ in only one or two positions from other mammalian forms of the peptide, on cardiovascular parameters and on respiration rate and on clonidine induced reduction of arterial blood pressure and respiration rate. BPP differs in 21 positions from APP, but BPP‐like and APP‐like immunoreactive neurons are distributed in the rat brain in a similar way and seem to represent one and the same neuronal system (Ol‐schowska et al. 1981). Thus, APP/BPP‐like immunoreactive material exists in the A neurons, but its exact identity is unknown.
Effect of fasting on the metabolism in rat aorta
Authors: DAHLKVIST HANS H. , ARNQVIST HANS J.
Published: December 2008

The oxidation of 14C‐labelled glucose, β‐hydroxybutyrate and palmitate to CO2 and the incorporation of 14C‐labelled amino acid into alkali‐soluble protein were studied in aorta from fed and fasted male Sprague‐Dawley rats, weighing about 200 g. Substrate oxidation and amino acid incorporation were measured during incubation of rat aorta in vitro for 2–3 h. After fasting for 6 h there was a slight but significant increase in the plasma concentration of β‐hydroxybutyrate. Blood glucose was lowered after 12 h while an increase in the plasma concentration of free fatty acids was found after 24 h. A decrease in the oxidation of glucose in rat aorta was found after fasting for 12 h and with prolonged fasting a further decrease in the aortic glucose oxidation was found. After fasting for 4 days the oxidation of β‐hydroxybutyrate and the incorporation of 14C‐leucine and 14C‐phenylalanine into protein were reduced in rat aorta while the oxidation of palmitate was not altered. The effects of fasting on substrate oxidation and amino acid incorporation in rat aorta, found in this study are similar to the known effects of diabetes on vascular metabolism.
Capillary permeability to sulphate‐substituted and neutral dextran fractions in the rat hindquarter vascular bed
Authors: HARALDSSON B. , MOXHAM B. J. , RIPPE B.
Published: December 2008

In order to investigate the impact of molecular charge on capillary permeability to macro‐molecules, capillary reflection coefficients (a) for various concentrations of two neutral dextran fractions (M̄w 70 000 and 139 000) and one negatively charged, sulphate‐substituted dextran fraction (M̄w 109 000) were determined in the isolated perfused rat hindquarter preparation, during stable haemodynamic conditions. The capillary reflection coefficient was calculated as the ratio between the estimated colloid osmotic pressure in vivo, determined by an osmotic transient technique, and that in vitro, measured with an osmometer. Despite its intermediate size the sulphated dextran (D 109‐S) showed a markedly higher a than the two neutral ones (D 70 and D 139) and, further, whereas o for D 70 and D 139 decreased with increasing dextran concentration, o for D 109‐S remained constant over the whole range of concentrations investigated. At dextran concentrations equivalent to an in vivo colloid osmotic pressure of 23.5 mmHg, s̀ averaged 0.901 for D 109‐S, compared with 0.547 and 0.693 for D 70 and D 139, respectively, and with 0.87 for albumin in normal plasma. It is suggested that capillary macromolecular permeability is due to both structural and electrophysical properties of the microvascular barrier, where negative charges of the endothelial glycocalyx and of wall‐adsorbed plasma proteins cause repulsion of circulating large poly anions.
A low continuous positive airway pressure induces regular breathing and increased inspiratory activity in newborn lambs
Authors: JONZON A. , SEDIN G.
Published: December 2008

To determine the lowest continuous positive airway pressure (CPAP) at which breathing becomes regular and to determine whether the phrenic nerve activity changes simultaneously, breathing pattern and phrenic nerve activity were studied in spontaneously breathing newborn lambs at various levels of CPAP. A CPAP of 0.25 kPa decreased the variability of phrenic burst interval, i.e. made the breathing regular. This CPAP also increased the mean impulse frequency within the phrenic nerve bursts, indicating greater inspiratory activity. A high CPAP did not offer any further advantages to the breathing pattern or to the inspiratory activity.
The effect of carotid occlusion on the rate of net fluid absorption in the small intestine of rats and cats
Authors: SJÖVALL H. , JODAL M. , REDFORS S. , LUNDGREN O.
Published: December 2008

The effect on net intestinal fluid absorption of unloading the baroreceptors by bilateral carotid occlusion was studied in rats and cats. It was shown that net fluid uptake from the intestine increased 30–40% upon carotid occlusion. This effect was eliminated by cutting the splanchnic nerves (cats) or by severing the nerves surrounding the superior mesenteric artery (rats). In fact, these denervation procedures resulted in a decreased net fluid absorption upon carotid occlusion. Cutting the vagal nerves did not significantly influence the response to carotid occlusion. It is concluded that the arterial baroreceptors influence net fluid transport in the small intestine, a reflex compensatory mechanism that may be important in different hypotensive situations.
Mechanism of blood pressure elevation during angiotensin infusion
Authors: STOKLAND OLAV , THORVALDSON JØRGEN , ILEBEKK ARNFINN , KIIL FREDRIK
Published: December 2008

The mechanism of increased preload and its contribution to the rise in blood pressure during intravenous angiotensin infusion were studied in anesthetized dogs. In open‐chest dogs angiotensin increased mean aortic blood pressure by 58±12 mmHg. Left ventricular end‐diastolic dimension, measured as myocardial chord length (MCL) by ultrasonic technique, increased by 7±1 %. By inflating a balloon in the inferior vena cava, end‐diastolic MCL was reduced to control value and the rise in mean aortic blood pressure was almost halved to 32±10 mmHg above control value. A similar preload effect was recorded in closed‐chest dogs using end‐diastolic left ventricular pressure as an estimate of left ventricular volume. During angiotensin infusion to the upper body only, end‐diastolic MCL did not increase. When redistribution of the splanchnic blood volume was prevented, the effect of angiotensin on end‐diastolic MCL was reduced to 1/3. Angiotensin reduced liver but not splenic dimension measured by ultrasonic technique. We conclude that about half of the rise in blood pressure during angiotensin infusion is due to increased end‐diastolic volume caused by blood redistribution. About 2/3 of this increase in preload is due to redistribution from the splanchnic bed, mainly from the liver.
The distribution of somatomedins in the nervous system of the cat and their release following neural stimulation
Authors: SARA VICKI R. , UVNÄS‐MOBERG KERSTIN , UVNÄS BÖRJE , HALL KERSTIN , WETTERBERG LENNART , POSLONCEC BRANKA , GOINY MICHEL
Published: December 2008

Recent evidence suggests a regulatory role in the nervous system for somatomedins. The present study, using a somatomedin radioreceptorassay which primarily detects insulin like growth factors 1 and 2, shows that somatomedins are widely distributed throughout the nervous system of the cat. Whilst somatomedins were present in all CNS regions, the highest concentration occurred in the hypothalamus followed by cerebral cortex. In the spinal cord, the dorsal roots contained twice the concentration found in the ventral roots. Activity was also present in the sympathetic ganglia, vagus nerve and sciatic nerves. Following electrical stimulation of the brachial and sciatic nerves somatomedins were released into perfusates from extirpated cut limbs. These findings suggest that somatomedins may be neuroregulatory hormones.
Occurrence of an insulin‐like peptide in extracts of peripheral nerves of the cat and in extracts of human vagal nerves
Authors: UVNÄS‐MOBERG KERSTIN , POSLONCEC BRANKA , HAGERMAN MAGNUS , CASTENSSON STAFFAN , RUBIO CARLOS , UVNÄS BÖRJE
Published: December 2008

Biopsies from various peripheral nerves were collected from living cats. The biopsies were extracted with acid ethanol and the insulin‐like immunoreactivity (ILI) content of the extracts determined with radioimmunoassay. The vagal, sciatic and radial nerves contained on the average 90, 3 and 28 ng of ILI per gram nerve tissue (wet weight), respectively. In the sympathetic trunc no ILI was found. In order to partly purify and characterize the nerve ILI extracts these were run on an HPLC system. The ILI coeluted with standard bovine insulin. The same amounts of ILI were found in the nerve extracts whether run on the HPLC system or not. It can be concluded that all of the immunoreactive material of the nerve extracts corresponds to insulin or to a peptide very similar to insulin. In two cats the radial and sciatic nerves were ligated for 24 h. Two to ten times more ILI occurred in biopsies taken proximal to the site of ligation than in those from corresponding distal biopsies, indicating that the insulin‐like material is transported distally within the nerves. ILI was found in extracts from vagal nerves taken from 3 days old human autopsy material. Also this human ILI coeluted with the bovine insulin standard in the HPLC system.

We propose that insulin or a very similar peptide is synthetized in peripheral nerves of cats and humans and we suggest that this neurogenic “insulin” might act as a neurotransmitter or neuromodulator.
Role of calcium in muscarinic autoinhibition of3H‐acetylcholine secretion in guinea‐pig ileum myenteric plexus
Authors: ALBERTS P. , STJÄRNE L.
Published: December 2008

The stores of acetylcholine (ACh) of the cholinergic neurons of guinea‐pig myenteric plexus were labelled by preincubation with3H‐(methyl)‐choline, to examine the dependence of the secretory mechanisms in these nerves, and of their muscarinic ‘autoinhibition’, on the extracellular calcium concentration. The curves describing the secretion of labelled transmitter evoked by electrical field stimulation at 1 Hz, as a function of external calcium, were essentially hyperbolic, except at very low calcium levels. Double reciprocal plots of the secretory responses vs. the external calcium concentration, within the 2–8 mM range, yielded straight lines, permitting estimation of apparent vCamax(height of asymptote parallel to abscissa=the maximal secretory response, at an infinitely high calcium level) and KCam(the calcium concentration yielding half‐maximal secretion). Neither addition of eserine, to indirectly activate muscarinic autoinhibition, nor of atropine to block it, markedly affected VCamax. In the absence of these drugs KCamabout 3.5 mM. Eserine raised it about 7‐fold, while further addition of atropine reversed this effect. The competitive pattern of interaction of drugs altering muscarinic autoinhibition, with the calcium dependence of the secretory mechanisms, suggest that this control is exerted by restriction of the ability of the nerve terminals to utilize external calcium.
Increase in duodenal tissue gastrin in dogs following antrectomy with gastroduodenostomy and after total gastrectomy with oesophagoduodenostomy1
Authors: BRODIN KERSTIN , NILSSON GÖRAN
Published: December 2008

The gastrin concentration in plasma and duodenal tissue was determined in dogs following antrectomy and total gastrectomy as well as in unoperated control animals. The first week after both types of operations, during which time the dogs were parenterally fed the basal plasma gastrin concentration was markedly reduced, and then it slightly increased. The increase in plasma gastrin concentration from the second postoperative week until sacrifice was found to be statistically significant in one of six antrectomized dogs and in two of three dogs in which the whole stomach had been resected. In unoperated controls the gastrin concentration in the proximal third of the duodenum was found to be 6.8±0.8 pmol/g tissue wet weight (mean value ± SE, n=11). Following antrectomy a time dependent increase was seen, the corresponding values being 11.0±2.5 (n=4), 36.4±15.7 (n=6) and 136.1±44.2 (n=6) pmol/g at 3, 9–10 and 14–16 weeks after operation, respectively. A similar increase was seen following total gastrectomy. 8 weeks after this type of operation the concentration was 22.2±12.5 (n=3) pmol/g. The gastrin concentration of the middle and distal thirds of the duodenum was not changed by the operations. The results show that removal of the main source of gastrin, i. e. the pyloric antrum, induces an increase in the tissue level of gastrin in the upper portion of the duodenum.
Effect of prostaglandin E1, dopamine and dibutyryl cyclic AMP on the fluidity of synaptosome membranes
Authors: HEINONEN ERKKI , GRIPENBERG JOHAN , JANSSON STEN‐ERIK
Published: December 2008

The membrane fluidity of synaptosomes, isolated from rat brain and spin‐labelled with doxyl derivatives of stearic acid, was studied using electron spin resonance techniques. Prostaglandin E1fluidized while dopamine ordered both the surface and intermediate lipid layers of the synaptosome membranes. At corresponding concentrations these substances have been shown to modulate synaptic transmission. A possible thermal phase transition of the membrane lipid bilayer was observed at about 35°C (the abrupt change in the Arrhenius plot). Dopamine abolished this thermal change. Dibutyryl cyclic AMP had no significant membrane effects.
Inhibition of gastric acid secretion by intestinal and parenteral administration of a mixture of L‐amino acids in the Atlantic cod, Gadus morhua
Authors: HOLSTEIN B. , HAUX C.
Published: December 2008

The effect on basal gastric acid secretion in the cod of a mixture of L‐amino acids (AA) was studied. Acid secretion was measured during a 5 h treatment period when the AA was administered intestinally, i. m. or i. v., and plasma α‐amino nitrogen following the treatment period. Acid secretion was inhibited, the depression related to the plasma level of AA but unrelated to the administration route. It is suggested that acid secretion is inhibited by absorbed AA acting from the blood side, without involvement of an intestinal mechanism.
Gastrin in duodenal and jejunal tissue and in plasma following antrectomy with gastrojejunostomy
Authors: BRODIN KERSTIN , NILSSON GÖRAN
Published: December 2008

The gastrin concentration in the proximal third of the duodenum was found to be increased in dogs following antrectomy with gastrojejunostomy. The level found 13–15 weeks after operation was, using a COOH‐terminal directed antiserum, 27.8±4.5 pmol/g tissue wet weight (mean value ± SE, n=5), which is approximately 4 times higher than the concentration found in the same tissue of unoperated dogs. In the middle and distal thirds of the duodenum the gastrin concentrations were 6.1±0.6 and 5.2±0.2 pmol/g (n=5), respectively. These values are not significantly different from those of the corresponding tissues of unoperated dogs. The gastrin concentration was also determined in different parts of the jejunum. In specimens taken close to the gastrojejunostomy, the gastrin level was 1.9±0.2 pmol/g,‐which was not significantly different from that in more proximal (3.0±0.3) or distal (1.7±0.2) parts of the jejunum in the same animals. Basal plasma gastrin concentration as measured with the same COOH‐terminal directed antiserum, was reduced after surgery to 35% (mean value) of the preoperative level and remained low throughout the postoperative period. In contrast to this, using an antiserum directed against the NH2‐terminal portion of gastrin‐17, the plasma gastrin concentration was found to be decreased to 70% 1–2 days after antrectomy and then to increase again and remain at approximately the preoperative level. The plasma gastrin concentrations measured with this antiserum, were consistently much higher than those measured with the COOH‐terminal directed antiserum. In a previous study we have shown that the gastrin concentration in the proximal third of the canine duodenum is increased 20‐fold at 14–16 weeks after antrectomy with gastroduodenostomy. In the present study it is shown that there is a less prominent increase after antrectomy with gastrojejunostomy. These results indicate that the presence of food and gastric juice in the duodenum might be of importance for the increase in duodenal gastrin after antrectomy.
Influences on central hemodynamics in hemorrhage of β2‐adrenergic vascular control mechanisms
Authors: GUSTAFSSON DAVID , HILLMAN JAHN , LUNDVALL JAN
Published: December 2008

Central hemodynamic responses evoked by standardized hemorrhage (exsanguination of 20 ml×kg bwt‐1) were followed during 2 h in cats with intact and blocked vascular β2‐adrenoceptors using the ‘selective’β2‐blocker, ICI 118, 551. In the first 10 min after bleeding blood pressure and cardiac output (CO) decreased and total peripheral resistance (TPR) increased by the same amount in the ‘intact’ and β2‐blocked animals. Whereas blood pressure later on reached approximately the same hypotension level in both groups, other hemodynamic variables were distinctly different. In the ‘intact’ animals there was a gradual, partial recovery of stroke volume (SV) and CO in the face of a restoration to control of TPR. In the β2‐blocked animals TPR continued to increase in the face of a maintained low CO and declining SV. The lower SV in the latter group was ascribed to abolition of β2‐adrenergic restoration of plasma volume via absorption of tissue fluid into the circulation. The gradual decline of TPR in the ‘intact’ animals was attributed to β2‐adrenergic dilator interaction with constrictor influences on the resistance vessels. It is concluded that β‐adrenergic vascular control mechanisms help to improve nutritional tissue blood flow during hemorrhage by increasing plasma volume, and hence venous return and CO, and by decreasing TPR. These reflex, β2‐adrenergic circulatory events are similar to those aimed at in current shock therapy by transfusion and vasodilator treatment.
Alpha and Beta adrenergic effects on metabolism in contracting, perfused muscle
Authors: RICHTER ERIK A. , RUDERMAN NEIL B. , GALBO HENRIK
Published: December 2008

The role of α‐ and β‐adrenergic receptor stimulation for the effect of epinephrine on muscle glycogenolysis, glucose‐ and oxygen uptake and muscle performance was studied in the perfused rat hindquarter at rest and during electrical stimulation (60 contractions/min). Adrenergic stimulation was obtained by epinephrine in a physiological concentration (2.4 × 10‐8M) and α‐ and β‐adrenergic blockade by 10‐5M phentolamine and propranolol, respectively. Epinephrine enhanced net glycogenolysis during contractions most markedly in slow‐twitch red fibers. In these fibers the effect was mediated by α‐ as well as by β‐adrenergic stimulation, the latter involving production of cAMP, phosphorylase activation and synthase inactivation. In contrast, in fast‐twitch fibers only β‐adrenergic mechanisms were involved in the glycogenolytic effect of epinephrine. Moreover, inactivation of synthase was less in these fibers. Epinephrine also increased the net release of lactate from the hindquarter, an effect abolished by combined α‐ and β‐adrenergic blockade but by neither α‐ nor β‐adrenergic blockade alone. Epinephrine increased uptake of oxygen and glucose by stimulation of α‐adrenergic receptors and had a positive inotropic effect during contractions which was abolished by α‐ as well as by β‐adrenergic blockade. The results indicate that epinephrine has profound effects on contracting muscle, and that these effects are elicited through different combinations of α‐ and β‐adrenergic receptor stimulation.
Central cardiovascular and thermal effects of prostaglandin E2in rats1
Authors: SIRÉN ANNA‐LENA
Published: December 2008

Prostaglandin E2(PGE2) increased the blood pressure, heart rate and body temperature, when administered at the doses of 0.001–10 μg into the lateral cerebral ventricle (i. c. v.) of the urethane‐anesthetised rat. The highest dose of 10 μg/rat induced a strong initial hypotensive effect. Intravenously (i. v.), PGE2at the doses of 0.01–10 μg/rat caused a biphasic blood pressure response with dose‐related initial decreases followed by slight increases in blood pressure. The heart rate and body temperature were slightly increased by i. v. administrations of PGE2. The highest i. v. dose of 10 μg/rat initially decreased also the heart rate. Central pretreatment with indomethacin (1 mg/rat i. c. v.) partly antagonised all of the recorded central effects of PGE2, while sodium meclofenamate (1 mg/rat i. c. v.) abolished the hypertensive response to i. c. v. administered PGE2but failed to significantly affect the PGE2‐induced rises of heart rate and body temperature. The results support the previous suggestions that PGE2may participate in the central cardiovascular and thermoregulatory control. The results also suggest that indomethacin and sodium meclofenamate antagonize the effects of exogenous prostaglandins. Since sodium meclofenamate, unlike indomethacin, affected preferentially the hypertensive response to centrally administered PGE2, there may be differences in the sites and/or modes of action between these drugs.
51Cr EDTA determinations of the extracellular fluid volume in hemorrhage: a study with fed and starved rats
Authors: WARE JAMES , NORBERG KARL‐AXEL , NORMAN MIKAEL , NYLANDER GUNNAR
Published: December 2008

Extracellular fluid volumes have been determined in fed and 24–30 h starved rats, before and after 60 min of hemorrhagic hypotension at 70 mmHg. Bilateral renal vascular ligation was carried out to prevent clearance of the isotope tracer used, 51Cr EDTA. The time taken for a bolus of the tracer to distribute itself in its space, was determined in fed and starved animals after the standard period of hypotension. This was found to be 37 min for fed animals, and 50 min for those which had been starved. When the isotope ECF space was compared before and after hemorrhage in fed animals, it was unchanged, despite an estimated blood volume loss of 39%. The isotope ECF space was reduced 5.5% after hemorrhage in animals which had been starved. It is concluded that fed rats mobilised intracellular fluid to the interstitium in hemorrhage, whereas, starved animals did not. This finding of variable fluid homeostasis is ascribed to the different nutritional status of the animals investigated, and has considerable implications.
Autoregulation of total and local renal blood flow in the rat during acute unilateral ureteral pressure elevation
Authors: HOPE ARVID , CLAUSEN GUNNAR
Published: December 2008

The rat kidney autoregulates its blood flow (RBF) when renal arterial blood pressure (RAP) is lowered, but less efficiently than does the dog kidney. We wanted to investigate to what extent acute unilateral elevation of ureteral pressure (UP) in the Sprague‐Dawley rat would interfere with the renal vasodilatory responses elicited by RAP reduction and by intraarterial infusion of acetylcholine (Ach). RBF was significantly better autoregulated before than during UP elevation to 43 mmHg (p<0.001), as measured electromagnetically in an extracorporal flow circuit. However, RBF decreased within the autoregulatory pressure range: Closely similar RBF reductions, 3–4% per 10 mmHg, were obtained both by increasing UP and by decreasing RAP by 10 to 50 mmHg. These RBF reduction did not involve active renal vasoconstriction since maximal dilation by i. a. Ach infusion (∽1.0 μg/min) increased RBF significantly more before and after than during UP elevation (p<0.01). The proportional responses to changes in intra and extra‐vascular pressures therefore suggest that a mechanism controlled by transmural pressure is responsible for RBF autoregulation. UP increase had no effect on contralateral RBF. The effect of UP elevation on intrarenal blood flow distribution, as determined by zonal uptake rates of the diffusible tracer125I‐iodoantipyrine, was studied in a second group of rats at an UP averaging 32 mmHg. Fractional zonal blood flow decreased in outer third (p<0.05) and increased in inner third of the cortex and outer half of the outer medullap<0.05). This redistribution was not detected if cortex was divided in halves only.
Dynamics of the interventricular septum and free ventricular walls during blood volume expansion and selective right ventricular volume loading in dogs
Authors: MOLAUG MÅLFRID , GEIRAN ODD , STOKLAND OLAV , THORVALDSON JØRGEN , ILEBEKK ARNFINN
Published: December 2008

To examine whether the right ventricle responds differently to blood volume expansion and selective right ventricular volume loading, segment lengths in the interventricular septum and the free walls of both ventricles and right ventricular septal‐to‐free‐wall‐ distance were measured by an ultrasonic technique in open‐chest dogs. Blood volume expansion increased segment lengths at all recording sites in proportion to stroke volume, Selective right ventricular volume loading induced by opening a shunt between the pulmonary artery and the superior vena cava increased right ventricular stroke volume by 40–80%; end‐diastolic segment length and myocardial shortening increased in the septum and free wall of the right ventricle whereas left ventricular stroke volume and segment length decreased. Comparison of data obtained before and after opening of the shunt indicated that changes in myocardial dynamics of the right ventricle and septum accounted for approximately 30% of the increase in right ventricular stroke volume. However, both end‐diastolic dimension and systolic shortening of the right ventricular septal‐to‐free‐wall distance were larger during right ventricular volume loading than during blood volume expansion. Thus, most of the increase in stroke volume during selective right ventricular volume loading is caused by a change in the configuration of the right ventricle.
Pancreatic polypeptide family (APP, BPP, NPY and PYY) in relation to sympathetic vasoconstriction resistant to α‐adrenoceptor blockade
Authors: LUNDBERG J. M. , TATEMOTO K.
Published: December 2008

Electrical stimulation of the cat cervical sympathetic trunk caused submandibular salivary secretion and vasoconstriction simultaneously with a contraction of the nictitating membrane. Following α‐ and β‐adrenoceptor blockade by phentolamine or phenoxybenzamine combined with propranolol, the salivary response and the nictitating membrane contraction upon sympathetic stimulation were almost abolished. A considerable vasoconstrictor response (up to 40% of control) however still remained in the submandibular gland. This yasoconstriction, which persisted after α‐adrenoceptor blockade, was rather slow in onset and had a long duration without any poststimulatory hyperemia. Local intra‐arterial infusions of noradrenaline caused submandibular vasoconstriction, salivary secretion and nictitating membrane contraction. The blood flow response to exogenous noradrenaline did, however, not mimic the effects of sympathetic nerve stimulation with regard to vascular escape. Whereas the vascular escape after nerve stimulation was followed by a prolonged vasoconstriction with a gradual decline, the escape after noradrenaline infusions was accompanied by a normalization of blood flow. Local intra‐arterial infusions of pancreatic polypeptide (PP)‐related peptides caused a slowly developing vasoconstriction with a long duration in the submandibular gland, but no salivary secretion or contraction of the nictitating membrane. The relative molar potencies as vasoconstrictory agents were about PYY: 1, neuropeptide Y (NPY): 5, avian and bovine pancreatic polypeptid 100. The vasoconstrictor effects of PP‐related peptides were resistant to α‐adrenoceptor blockade and present also in sympathectomized animals, suggesting a direct action on vascular smooth muscle. Combined local infusions of noradrenaline and NPY caused a vascular response in the submandibular salivary gland which was similar to that seen upon sympathetic nerve stimulation. PYY and NPY caused increase in systemic arterial blood pressure upon systemic administration which indicates general vasoconstrictor actions. This effect was accompanied by a transient bradycardia which was due to inhibition of sympathetic tone, since it was absent in animals treated with propranolol.

In conclusion, the present findings illustrate the differential sensitivity to α‐adrenoceptor antagonists of the submandibular vasoconstriction and salivation as well as smooth muscle contraction of the nictitating membrane induced by sympathetic nerve stimulation. This remaining vasoconstriction may be explained by release of a nonadrenergic, PP‐related transmitter such as NPY which may be present together with noradrenaline in the vascular nerves. Release of an additional vasoconstrictory factor may also account for the finding that infusions of noradrenaline do not mimic the vascular effects of sympathetic nerve stimulation in vivo.
Effects of adrenergic blockade on the release of insulin, glucagon and somatostatin from the pancreas in response to splanchnic nerve stimulation in cats
Authors: ANDERSSON PER‐OLOF , HOLST JENS , JÄRHULT JOHANNES
Published: December 2008

The effects of α‐,β‐ or α+β‐adrenergic blockade on arterial plasma concentrations of insulin, glucagon and somatostatin in response to splanchnic nerve stimulation were studied in anesthetized cats. In control experiments splanchnic nerve stimulation caused a marked rise in plasma glucose and glucagon concentrations and a marked fall in insulin but somatostatin was unaffected. Pretreatment with phentolamine significantly increased basal plasma insulin concentration but the response pattern to splanchnic nerve stimulation was not altered. Propranolol attenuated both the glucose and insulin responses. Combined α‐and β‐blockade abolished the hyperglycemia and hypoinsulinemia induced by splanchnic nerve stimulation, whereas the rise in plasma glucagon was not affected. It is concluded that insulin release from the pancreas and glucose release from the liver is controlled by adrenergic mechanisms whereas pancreatic glucagon and somatostatin secretion is relatively insensitive to splanchnic nerve stimulation in cats.
The influence of vascular β‐adrenoceptors on the position and mobility of the rabbit incisor tooth
Authors: AARS HARALD
Published: December 2008

The influence of vascular β‐adrenoceptors on the tooth‐supporting functions of the periodontal ligament were studied in 30 anesthetized rabbits. Propranolol and the β2‐adrenoceptor antagonists ICI 118,551 and H 35/25 induced a marked extrusion of the incisor, probably due to reduced vasodilator tone in periodontal postcapillary blood vessels. Isoprenaline reversed the movement. β1‐ and β2‐receptor antagonists decreased the intrusive responses to sympathetic nerve stimulation in teeth close to control position, but had no effect on responses in fully extruded teeth. Intrusive mobility, as tested by intermittent loading with 5–10 g, remained unaffected by β‐adrenoceptor blockade. The results suggest that vascular β2‐adrenoceptors are important in the regulation of tooth position by their control of periodontal postcapillary resistance. Prejunctional β‐receptors enhancing the vasoconstrictor ‐ and intrusive ‐ responses to sympathetic nerve stimulation are probably a mixture of β1‐ and β2‐receptors. It would seem that the periodontal vasculature is important for the position of the rabbit tooth but, due to rapid adaptive mechanisms of the tooth‐supporting tissues, the vasculature contributes little to the resistance against loadinduced intrusive movements of the tooth.
Acetylcholine synthesizing activity and nicotinic binding sites in rat hind limb muscles during reinnervation
Authors: ASKMARK HÅKAN , AQUILONIUS STEN‐MAGNUS , FAWCETT PETER , NORDBERG AGNETA , ECKERNÄS SVEN‐ÅKE
Published: December 2008

Acetylcholine synthesizing (ACh‐s) activity and binding of the nicotinic ligands 3H‐α‐bungarotoxin (α‐Btx) and 3H‐d‐tubocurarine (d‐TC) were analysed in rat hind limb muscles for up to 6 months after a cryolesion of the sciatic nerve. Muscles of the contralateral leg served as controls. After cryolesion there was a rapid decrease in ACh‐s activity parallel to a considerable increase in α‐Btx binding. A clearcut increase in ACh‐s activity was first seen at 32 days and complete restoration in ACh‐s activity was seen from 2–3 months postoperatively. From the 16th day there was a rapid decrease in α‐Btx binding sites and initial values were seen at the 32nd day postoperatively. D‐TC binding sites were relatively unchanged during the experimental period. The first neurophysiological signs of reinnervation were seen at 16 days. The rats were observed to move normally about 2 months postoperatively. Normalization of α‐Btx binding sites seems to be an earlier sign of reinnervation than normalization of ACh‐s activity.
The cellular uptake of 5‐hydroxytryptamine in the rat lung in vivo–a histochemical study
Authors: KJELLSTRÖM THOMAS , AHLMAN HÅKAN , DAHLSTRÖM ANNICA , RISBERG BO
Published: December 2008

The cellular uptake of 5‐hydroxytryptamine (5‐HT, serotonin) in the rat lung was studied in vivo after bolus injection of the amine (1 mg/100 g b. w. i. v.). The cells responsible for the 5‐HT uptake were visualized by fluorescence microscopy according to the Hillarp‐Falck technique and further identified as mast cells by Astra Blau staining. The quantitative aspects of the 5‐HT uptake were studied by a specific cytofluorimetric method. A significantly increased intracellular content of 5‐HT was found in interstitial pulmonary mast cells 1 min after injection. No 5‐HT uptake was demonstrated within epithelial cells of the bronchiolar mucosa or within the pulmonary vascular endothelial cells; not even in animals pretreated with monoamine oxidase inhibitor. This finding is in contrast to the endothelial uptake earlier demonstrated by autoradiography in artificially perfused lungs. One explanation for this discrepancy may be a rapid transport of the amine across the vast endothelial area in the lung in vivo resulting in low 5‐HT concentrations within the endothelium, not detectable by fluorescence microscopy. After endothelial passage the amine was rapidly taken up and stored in interstitial mast cells, which normally have the amine handling properties.
Estrogen inhibition of noradrenaline release in the rabbit oviduct1
Authors: BENGTSSON BENGT , MARSHALL JEAN M.
Published: December 2008

In the present study, we investigated the influence of estrogen on3H‐noradrenaline (3H‐NA) release induced in the oviductal isthmus by electrical stimulation, potassium and calcium. The fractional release of3H‐NA was measured in oviducts isolated from ovariectomized rabbits and from ovariectomized rabbits treated with estradiol cypionate, 70 μg/kg im 72 h before an experiment. Electrical field stimulation of the intramural nerves induced muscle contraction and augmented the release of labelled NA from the muscle. The3H‐NA release was reduced after estrogen treatment when reuptake of NA into the nerve terminals was blocked by desipramine, 10‐6M. Estrogen also reduced the3H‐NA release evoked by exposure of the oviducts to 121 mM KCI in the presence of calcium (2.5 mM) and in a high potassium, calcium‐free medium upon the addition of 2.5 mM calcium. In the presence of desipramine a small fraction of3H‐NA was released in high potassium, calcium‐free medium. This release was unaffected by estrogen. These results suggest that estrogen reduces the release of NA from the adrenergic nerves within the oviduct and that this action is exerted primarily on the calcium‐dependent release. It therefore might be due to a reduction in the entry of calcium into the nerve terminal.
Acidification in the distal tubule of the Amphiuma kidney
Authors: PERSSON BO‐ERIC , PERSSON A. ERIK G.
Published: December 2008

The acidification of the urine within the distal tubule of Amphiuma means was studied with micropuncture techniques. Antimony microelectrodes calibrated in vivo were used for measuring the intratubular pH and samples were taken for the determination of Na+‐ and Cl‐‐concentrations and for determining buffer lines within the HCO‐3‐CO2 buffer system. The TF/P Na+ was used as a relative length determinator and a significant acidification along the length of the tubule was found. The pH in the tubule was more acid than samples equilibrated at blood Pco2. This disequilibrium can be described in terms of an imbalance within the Henderson‐Hasselbach formula or/and as a Pco2‐gradient across the tubular wall. The calculated Pco2‐gradient was found to be correlated to the arterial Pco2 and the acidification to the arterial pH. The greatest pH‐gradient is generated in the collecting duct and in the bladder.
The effect of splanchnic nerve stimulation on blood flow distribution, villous tissue osmolality and fluid and electrolyte transport in the small intestine of the cat
Authors: SJÖVALL HENRIK , REDFORS STAFFAN , HALLBÄCK DAN‐AXEL , EKLUND STEFAN , JODAL MATS , LUNDGREN OVE
Published: December 2008

The effect of splanchnic nerve activation on intestinal fluid transport and intramural blood flow distribution was examined in the cat. Previous reports from our laboratory have demonstrated that splanchnic nerve activation increases fluid absorption. The present study was performed to elucidate the mechanisms behind this effect. The results showed an increase in net sodium and chloride transport on splanchnic nerve activation whether intestinal blood flow decreased or not. The effect on sodium transport was due to a decrease in lumen to tissue flux. The effect could not be explained by a decrease in local blood flow, as it was present despite constant blood flow in both the villous and crypt regions. No change was seen in the villous osmolality gradient on splanchnic nerve activation. On the basis of these findings, it is proposed that the in vivo effect of splanchnic nerve activation is due to a decrease in fluid and electrolyte secretion, probably occurring in the intestinal crypts.
Modification of cardio‐vascular responses to hemorrhage by induced hyperosmolality in the rat
Authors: QUIROS G. , WARE J.
Published: December 2008

Starved rats sedated with a neurolept analgesic were subjected to hemorrhagic hypotension while receiving infusions of iso‐osmolar and hyperosmolar solutions. The hemorrhage model used resulted in similar residual blood volumes and hematocrits in all groups. The non‐metabolizable pentose, xylose, and glucose were used to induce a state of hyperosmolality, which was absent in those animals which received iso‐osmolar infusions (0.29 M xylose). After 45 mins hemorrhagic hypotension and a blood loss equal to 40% of the initial blood volume, the animals receiving the hyperosmolar infusions had a better cardiovascular status compared to those which received the iso‐osmolar infusions. The cardiac outputs and stroke volumes were higher and heart rate lower in the hyperosmolar groups. Evidence of better tissue perfusion was obtained in those animals with the induced state of hyperosmolality.
An oscillating intratubular pressure response to alterations in Henle loop flow in the rat kidney
Authors: LEYSSAC P. P. , BAUMBACH L.
Published: December 2008

We describe in gas anesthetized rats an oscillating intratubular pressure response, probably of vascular origin, sensitive to small physiological changes in fluid delivery to the distal tubule. The oscillation appararently indicates that an adjustment of vascular resistance is in operation, but at present it reveals neither the effector site (afferent and/or efferent arteriole) nor the effector mechanism (vasoconstriction and/or dilatation). The renin‐angiotensin system seems to be involved in this phenomenon.