bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of β‐receptor blockade on adrenaline‐induced changes in redox and energy state in m. vastus lateralis and m. soleus of the rat in vivo
Authors: FELLENIUS ERIK , HEDBERG ROLAND , KARLSSON NILS
Published: December 2008

The metabolic changes in blood, red (m. soleus) and white (m. vastus lateralis) skeletal muscle fibres were investigated after short‐term (3 min) infusion of adrenaline with or without prior treatment with propranolol or metoprolol. The adrenaline‐induced increase in plasma lactate levels was totally prevented by prior treatment with metoprolol or propranolol, whilst the β‐blockers had no effect on blood glucose levels. Similar effects on lactate levels were found in the m. soleus, while metoprolol was less effective than propranolol in m. vastus lateralis. Adrenaline decreased the level of muscle creatinine phosphate and ADP, causing the equilibrium of the creatinine kinase reaction to change in the direction of ATP synthesis, although the level of ATP usually decreased. This effect was more pronounced in m. vastus lateralis compared with m. soleus. The [ATP]/[ADP] [Pi]‐ratio tended to increase during infusion of adrenaline. This effect was counteracted by metoprolol but not by propranolol. The effects on the “phosphate potential” ([ATP]/[ADP] [Pi]) and the equilibrium within the creatine kinase were more pronounced in m. vastus lateralis than in m. soleus. The results demonstrate the possible role of receptors other than β‐receptors, i.e. α‐receptors, in mediating changes in plasma glucose levels, while plasma lactate levels are regulated by the β‐adrenergic system. The role of β‐receptors in mediating changes in muscle lactate levels may differ in m. soleus and m. vastus lateralis, with a relative predominance of β2‐‐receptors in m. vastus lateralis. Quantitative and qualitative differences in the adrenergic control of the energy state in the two types of muscle fibre were obvious, although it was not possible to distinguish clearly between the relative importance of α1β1and β2‐receptors.
Effects of short‐term and prolonged infusions of somatostatin on endocrine pancreas, body weight and food intake in rats
Authors: LINS P. E. , PETERSSON B. , EFENDIC S.
Published: December 2008

Infusion of cyclic somatostatin (700 ng/kg/min) for 4 h in rat fed ad libitum suppressed basal insulin but not glucagon release. It was accompanied by hypoglycemia during the first hour whereas, at the end of the infusion, hyperglycemia was present. The same dose of somatostatin applied 60 min prior to and during a 30 min load of glucose or arginine significantly inhibited their effects on insulin and glucagon release. In contrast, when this dose of somatostatin was given during a 24 h period by the i.v. route it did not inhibit glucose induced insulin release though circulating somatostatin levels were constantly and markedly elevated. Furthermore, in rats continuously infused with somatostatin for 4 days, no effect was found either on plasma concentrations of glucose. insulin, glucagon, growth hormone and cyclic AMP, or on body weight gain, food consumption or water intake. The pancreases of these animals showed normal concentrations of insulin and glucagon and a normal nuclear area of D‐cells. Our experiments demonstrate that, in short‐term experiments in rats, somatostatin influences insulin and glucagon release as well as glucose homeostasis. Furthermore, they suggest that during prolonged i.v. administration of somatostatin, rats develop mechanisms counteracting the effect of the peptide, e.g., peripheral tachyphylaxis.
Degradation of TRF immunoreactivity in rat hypothalamus, extrahypothalamic brain and pancreas
Authors: KOIVUSALO F.
Published: December 2008

The endogenous TRF as measured in radioimmunoassays of chromatographically purified extracts of excised hypothalami, extrahypothalamic brains and pancreas was shown to be stable in intact organs and homogenates. However, synthetic TRF added to tissue homoge‐nates was degraded. Sonication of the homogenates liberated endogenous TRF for degradation. Chromatographically purified tissue extracts of hypothalamus, extrahypothalamic brain and pancreas were degraded similarly by rat serum. These results suggest that the major portion of endogenous TRF occurs in a protected form in tissues and hence the physiologically effective amount of TRF must be very low when compared to its total content in tissues.
Central interaction between reflex responses to activity in aortic nerve A‐ and C‐fibres
Authors: AARS HARALD
Published: December 2008

The question of whether or not activity in myelinated (A) and non‐myelinated (C) afferents in a baroreceptor nerve shows interaction of their reflex effects, was investigated in 10 anesthetized rabbits. The central end of the cut left aortic nerve was stimulated by two sets of electrodes, one for selective high‐frequency excitation of A‐fibres (A‐stimulation) and one for low‐frequency activation of C‐ (and A‐) fibres by another pulse generator (C‐stimu‐lation). The pulse rates in C‐stimulations were too low to evoke reflex effects via A‐fibres. The hypotensive response to combined stimulations of A‐ and C‐fibres (AC‐stimula‐tion) was found to exceed the sum of responses to separate A‐ and C‐stimulations in 21 of 22 stimulation series. For sympathetic activity to the kidney, a greater than additive effect was observed in 16 of 24 series (P= 0.08), while in 6 of the series, the responses were equal. Median values of the ratio AC/(A+C) were 1.28 for the reflex changes in pressure and 1.11 for the effects on renal nerve activity. Similarly, C‐stimulation, which in comparison to A‐stimulation affected sympathetic activity relatively more than blood pressure, in 13 of 16 series (P=0.01) produced a greater sympathetic inhibition when added to a background of A‐fibre activity than when alone. These results suggest that a synergistic interaction exists between central effects of afferent discharge in aortic nerve A‐ and C‐fibres.
Estimation of capillary permeability of inulin, sucrose and mannitol in rat brain cortex
Authors: AMTORP OLE
Published: December 2008

The present study analyzed the brain uptake of the differently sized hydrophilic molecules 14C‐inulin, 14C‐sucrose and 14C‐mannitol. Constant tracer concentrations were maintained in blood plasma after renal ligation. Accumulation of the indicators was measured in brain cortex during the approach to steady‐state. At the conclusion of infusion periods of 5, 10, 15, 30 and 60 min, samples of cerebral cortex were analyzed for radioactivity. Fractions attributable to blood in the tissue were subtracted and time‐dependent apparent distribution volumes of the indicators in the tissue were estimated. The brain level did not rise to more than 1–2% of that in the plasma for inulin and sucrose and to 6–7% for mannitol. The explanation for this could be a combination of restricted penetration from blood into brain and a sink effect of cerebrospinal fluid (csf). To determine the removal of the indicators into csf, ventriculo‐cisternal perfusion was performed during the period of tracer uptake in the tissue; the rate of passage of the indicators into perfusion fluid was found to be negligible in comparison to the rates of uptake in the tissue. As diffusion in the extracellular space could limit uptake rates from blood to brain, estimates of diffusion limited half‐times were also made. Calculations showed that the major hindrance to indicator uptake in the tissue is located in the wall of the brain capillaries; thus the uptake data permit calculation of brain capillary permeability. The half‐times for the distribution of the indicators in their equilibrated tissue distribution spaces were used to estimate brain capillary permeability. By comparison with the aqueous diffusion coefficients of the indicators it is concluded that the substances in the molecular weight range of 182 to 5 500 daltons are subjected to restricted diffusion during the passage of the blood‐brain barrier and that in addition non‐discriminative transendothelial pathways are available.
Blood flow changes in the duck during thermal panting
Authors: BECH CLAUS , JOHANSEN KJELL
Published: December 2008

Carotid and sciatic blood flow have been measured in resting and panting Pekin ducks using electromagnetic flowmeters. Panting induced by high ambient temperature caused the carotid blood flow to increase from 9.6 to 26.0 ml min‐1, while the sciatic flow declined slightly from 41.6 to 38.1 ml min‐1. During panting breathing rate increased 10–20 times, but there were no significant changes in heart rate and mean arterial blood pressure. The carotid peripheral resistance was therefore greatly reduced, whereas sciatic resistance remained unchanged or increased slightly. The vascular beds perfused by the sciatic (legs) and carotid (upper respiratory tract) arteries are both important for heat dissipation. This study shows that when heat dissipation from the naked legs becomes inefficient due to high ambient temperature, blood flow in the sciatic tended to decline while conversely panting was associated with a large increase in carotid flow.
Relation between cell length and force production in urinary bladder smooth muscle
Authors: UVELIUS BENGT , GABELLA GIORGIO
Published: December 2008

Guinea‐pig and rabbit urinary bladders were fixed in glutaraldehyde at different volumes. Strips were dissected out, embedded and cut for phase contrast and electron microscopy. Muscle wall thickness decreased with increased bladder volume as did the radial number of muscle cells. Cell length, measured by a morphometric method increased linearly with bladder radius, indicating that no slippage between the muscle cells occurred. Number of cells per mm2 cross sectional area increased linearly with bladder radius. Volume‐active force relations were obtained by pelvic nerve stimulations of guinea pig bladders filled to different volumes. Maximum pressure was obtained at 0.15 ml bladder volume, and maximum wall tension at a volume of 2.5 ml which corresponds to a cell length of 400 μm and a cell packing density of about 107000×mm‐2. Estimation of the length‐active tension curve for the average muscle cell in the guinea‐pig bladder indicated a maximum active force of 5.5 μN/cell. Maximum active force per cm2 muscle bundle was calculated to be about 59 N. No compensation for extracellular space and nonmuscular tissue within the muscle bundle was made.
Vanadate‐induced oliguria and vasoconstriction in the cat
Authors: LARSEN JENS ANKER , THOMSEN OLE ØSTERGAARD
Published: December 2008

The effect of sodium orthovanadate (vanadate) on kidney function and hemodynamics was tested in chloralose anesthetized, fasting cats. Vanadate given i.v. caused a reversible, marked decrease in glomerular filtration rate and urine production without significantly affecting the fractional water excretion rate. In the recovery period, after administration of vanadate, urine flow and the urinary excretion rate of electrolytes were only slightly different from control values. This action of vanadate appears to be due mainly to constriction of the renal blood vessels leading to a fall in glomerular capillary pressure. Vanadate likewise caused a dose dependent decrease in arterial conductance and blood flow of other vessels in the splanchnic area, whereas the femoral and carotid arteries were reversely and less affected. The vascular effect appears to be caused by a direct action of vanadate on vascular smooth muscle, but the mechanism of action is still unsettled.
Characterization of contractions in mechanically disaggregated myocardial cells from the rat
Authors: LEHTO H. , TIRRI R.
Published: December 2008

Myocardial cell groups, mechanically disaggregated from the rat heart, beat spontaneously in a medium which resembles intracellular fluid. The cells, initially functioning in an uncoordinated way, i.e. each cell in its own rhythm, gradually become coordinated as a function of time. After 90 min of incubation at 15°C all the cell groups were functioning in a coordinated way. The initiation of coordination was temperature‐dependent. Lowering the temperature from 15°C to 10°C significantly delays the coordination, only 75% of the cell groups being coordinated after 90 min. The contraction wave in coordinated cell groups was very slow; 90±7 μm/s at 20°C. 100±6 μm/s at 30°C and 100±7 μmls at 35°C. The velocity of contraction waves was not significantly temperaturedependent, suggesting a neonenzymatical type of propagation. It also seems too slow to be an electrical event. Apparently the contraction waves are propagated by diffusion of Ca2+. The addition of caffeine to the medium hastened the coordination of contractions, but Na‐aide strongly inhibited it. The results indicate that the sarcoplasmic reticulum functions in the coordination of contractions, probably by releasing Ca2+ for the activation of the myofilaments.
Effect of intraluminal pH on the release of somatostatin and gastrin into antral, bulbar and ileal pouches of conscious dogs
Authors: UVNÄS‐WALLENSTEN KERSTIN , EFENDIC SUAD , JOHANSSON CATJA , SJÖDIN LARS , CRANWELL PETER D.
Published: December 2008

Experiments were performed on conscious dogs with chronic pouches of the antrum, the duodenal bulb or the ileum, which were perfused with solutions of varying pH. Gastrin and somatostatin levels were measured in the perfusates. When the pouches were perfused with 0.15 M NaCl only small amounts of gastrin and somatostatin (1 pmoll min) were released into the lumen of the antrum and of the duodenal bulb. By lowering pH of the perfusion fluid a pH dependent release of somatostatin was induced into the lumen of the antrum and the duodenal bulb. Perfusion with 0.I M HCI caused a large output of somatostatin (6–60 μmol/min) into the pouches. The upper pH limit for stimulation of the intraantral or intrabulbar somatostatin release appeared to be ˜pH 3–4. Somatostatin was also released into ileal perfusates at intraluminal pHs below 3–4. Lowering of pH in the antral pouches caused an increased intraluminal gastrin release, which was quantitatively less impressive than that of somatostatin. Occasionally also the gastrin release into the duodenal bulb increased during perfusion with 0.1 M HCI, whereas no such release was induced by acidification of the lumen of the ileum. It is suggested that the inhibition of gastrin release observed at low intraantral pH is mediated by a local effect of somatostatin, since this peptide is released in a pH dependent manner in the antropyloric region. It is also suggested that acidification of any region of the gastrointestinal tract will stimulate the release of peptides from all endocrine cells of the open type, probably by an unspecific effect on the membrane. Thus both gastrin and somatostatin are released by acidification of the antrum, but in the presence of high local levels of somatostatin, the release of gastrin is substantially inhibited.
Stimulation of gastric acid and bicarbonate secretions by calcium in guinea pig stomach and amphibian isolated mucosa
Authors: FLEMSTRÖM GUNNAR , GARNER ANDREW
Published: December 2008

Administration of Ca++ (1.5 mg/kg i.v.) increased the output of both H+ and HCO3‐ from the stomach of the anesthetized guinea pig as determined by measurement of gastric intraluminal pH and pCO2. The rise in HCO3‐ secretion was slightly greater than that in H+, resulting in a decrease in net acidity. Fundic mucosa isolated from frogs was used to study the mechanisms of the stimulatory actions. An increase in Ca++ concentration in the nutrient (serosal) bathing solution from 1.8 to 7.2 mM stimulated H+ transport in this preparation. The effect of raising Ca++ concentration was inhibited by the histamine H2 receptor antagonist Metiamide and by increasing nutrient Mg++. Stimulation of H+ transport, sensitive to Metiamide, was also observed with the calcium ionophore A23187 (4 μg/ml, nutrient side). The results indicate that at the mucosal level, Ca++ stimulates H+ transport by release of histamine from mucosal stores with properties similar to those of mast cells. Transport of HCO‐3 in isolated mucosae was studied after inhibition of H+ transport my metiamide. An increase in nutrient Ca++ concentration stimulated the HCO‐3 transport but the calcium ionophore had no effect. This action of Ca++ was abolished by atropine (10‐‐6 M) and by raising nutrient Mg++, suggesting that it reflects release of acetylcholine from intramucosal nervous tissue. Thus Ca++ stimulated gastric transport of both H+ and HCO‐3 in vivo and in vitro but evidence for a direct action on the transporting (parietal and epithelial) cells was not obtained.
Nervous control of pancreatic endocrine secretion in pigs
Authors: HOLST JENS J. , GRØNHOLT RIKKE , de MUCKADELL OVE B. SCHAFFALITZKY , FAHRENKRUG JAN
Published: December 2008

The glucose dependent glucagon and insulin responses to electrical vagal stimulation in anesthetized splanchnicotomized young pigs were studied after administration of various pharmacological blocking agents. Hexamethonium completely abolished the responses, regardless of the glucose level. Atropine was without effect on the glucagon as well as the insulin response, regardless of stimulation frequency, glucose level, or dose of atropine. Neither propranolol nor a combination of propranolol and phenoxybenzamine inhibited the response. Our findings indicate that neither adrenergic fibres nor fibres impinging on muscarinic cholinergic receptors are involved in the pancreatic endocrine response to vagal stimulation.
Studies on the endoanesthetic effects of lidocaine and benzonatate on non‐medullated nerve endings in the left ventricle
Authors: THORÉN P. , ÖBERG B.
Published: December 2008

The blocking (endoanesthetic) effects of lidocaine (Xylocaine®) and benzonatate (Tessa‐Ion®) on cardiac ventricular, non‐medullated endings were tested in cats. Lidocaine was found to cause an effective and long‐lasting partial blockade of the cardiovascular reflex responses to stimulation of the ventricular receptors. This effect was obtained at plasma concentrations of 2.5‐4.7 μg/ml, which is within the concentration range seen in patients with myocardial infarction treated with lidocaine because of its antiarrhythmic properties. Tessalon also markedly attenuated the reflex response, normally obtained when the ventricular receptors are excited, but the effect was very shortlasting when doses, producing no side effects, were used. Recordings of impulse traffic from the left ventricular receptors showed that the impaired reflex responses after lidocaine and Tessalon were due to a blockade at the receptor level. Thus both the receptor response to ventricular distension and to injection of protoveratline (Bezold‐Jarisch reflex) was markedly attenuated after infusion of lidocaine (2–4 mg/kg) or a bolus injection of Tessalon (0.2‐1 mg/kg).
Influence of acid‐base changes on carbachol‐ and potassium‐induced contractions of taenia coli of the rabbit
Authors: LÖFQVIST JOHAN , NILSSON ERIK
Published: December 2008

The influence of acid‐base changes (variations of extracellular pH within the range 6.2–8.2 and parallel changes in (HCO3‐) and PCO2 at constant external pH) on contractions induced by carbachol and K+ was studied on preparations from taenia coli of the rabbit. Extracellular acidosis increased the concentration of carbachol necessary to evoke a given muscle tension and reduced the maximum response. During a carbachol‐induced contraction acidosis reduced and alkalosis enhanced muscle tension. Changes in extracellular pH within the range 6.2–8.2 did not affect the initial, rapid phase of the contraction induced by 145 mmol/1 of K+. However, with 40–80 mmol/1 of K+ acidosis reduced the phasic response. The tonic contraction following the initial phasic response in 145 mmol/1 K+ was enhanced by extracellular acidosis and decreased by alkalosis, whereas at a K+ ‐concentration of 70 mmol/l the amplitude of the tonic contraction was greater at pH 7.4 than at pH 6.2. Propranolol 10‐6 mmol/1 did not affect the influence of extracellular pH upon the K+ ‐contracture. An increase of both PCO2 and (HCO3‐) at constant extracellular pH did not alter the response of the muscle to carbachol. The tonic contraction during K+ ‐stimulation was diminished by a parallel increase in PCO2 and (HCO3‐) and at 47 mmol/l (HCO3‐) it was almost abolished. A rise in PCO2 from 5 to 14 kPa without changes in (HCO3‐), which caused extracellular pH to drop from 7.4 to 6.3, increased the tonic contraction in the same way as a fall in extracellular pH alone. These results seem to indicate that extracellular acidosis within the pathophysiological range (1) decreases the sensitivity of the polarized smooth muscle membrane to cholinergic stimulation, (2) reduces: the rate of release of stored Ca++, the transmembrane flow of Ca++ into the muscle cell, and the rate of Ca++ inactivation or extrusion during K+‐contraction. The reduction of the tonic contracture with increasing PCO2 and (HCO3‐) at constant extracellular pH is most likely attributable to the (HCO3‐) ion.
The effect of physical training on insulin secretion of rat pancreatic islets
Authors: GALBO H. , HEDESKOV C. J. , CAPITO K. , VINTEN J.
Published: December 2008

Rats were either physically trained by a 12‐wk swimming program or were freely eating or weight matched, sedentary controls. Islets of Langerhans were isolated and incubated at various glucose concentrations. Within the range of physiological glucose concentrations the rate of insulin release from islets of trained rats was lower than that from islets of sedentary controls. The DNA content of the islets was similar in the different groups. The demonstrated decreased glucose sensitivity of the insulin secretory mechanism within the β‐cells of trained rats may partly explain the finding of lower plasma insulin concentrations during intravenous glucose tolerance test in these rats compared with sedentary rats. Epididymal fat pads of trained rats were smaller than those of weight matched controls which in turn were smaller than those of freely eating controls, these differences being due to differences in fat cell size. The lower glucose sensitivity of the β‐cells in trained rats was probably not a consequence of the low body weight and small fat depots in these rats.
Quantitative aspects of electrical and mechanical responses to anisosmolar solutions in the smooth muscle of the rat portal vein
Authors: SIGURDSSON STEFAN B. , JOHANSSON BÖRJE
Published: December 2008

The electrical and mechanical activity of the rat portal vein were studied quantitatively under prolonged exposure to solutions in which osmolality was varied by changes in sucrose content. Reducing osmolality by 15 or 30 mosm/kg below the control value of 290 mosm/kg caused enhanced electrical and mechanical activity whereas hyperosmolality up to 390 mosm/kg led to inhibition as demonstrated earlier. These responses faded under prolonged exposure. In hypoosmolality integrated mechanical activity returned to control after about 10–15 min while spike activity remained somewhat increased. Prolonged hyperosmolality was associated with return of spike discharge towards control frequency whereas the integrated contractile force reverted from initial inhibition to levels above control after some 10–15 min. Therefore, the integrated force per spike was increased by prolonged hyperosmolality and decreased by hypoosmolality. Variations in osmolality had similar effects on the amplitude of K+contractures. The time course of the osmotic responses are discussed in relation to the dynamic effects of passive stretch and shortening in the portal vein. The relation that may exist between “inotropic” effects of osmolality and the contractures obtained in strongly hypertonic media is considered.
Caecal decomposition of uric acid in captive and free ranging willow ptarmigan (Lagopus lagopus lagopus)
Authors: MORTENSEN A. , TINDALL A. R.
Published: December 2008

Urine entering the caeca of birds contains significant amounts of uric acid. The discovery of great numbers of bacteria utilizing uric acid in the caeca has encouraged the discussion about nitrogen recycling in birds. In this work caecal decomposition of uric acid in wild and captive willow ptarmigan has been investigated using radioactively labelled uric acid injected directly into one of the caeca. The appearance of radioactive CO2 in the expired air was taken as an indication of uric acid breakdown. The decomposition occurred at a rate corresponding to a half‐life of 26 min (11–36 min). The results are in accordance with the previously reported observations of huge numbers of uric acid utilizing bacteria in the caeca of a variety of birds, and also with the nitrogen recycling theory. However, no conclusion concerning the nitrogen recycling can be drawn.
Prestretch potentiation of human skeletal muscle during ballistic movement
Authors: BOSCO CARMELO , KOMI PAAVO V. , ITO AKIRA
Published: December 2008

The conditions associated prior to and during the transition from prestretch to shortering may have considerable influence on the final performance of muscle. In the present study male subjects of good physical condition performed vertical jumps on the force‐platform with and without preliminary counter movement. In the counter movement jump (CMJ) the amplitude of the knee bending, velocity of the prestretch and the force attained at end of prestretch were the primary parameters of interest. In addition the coupling time indicating the transition from the eccentric (prestretch) phase to the concentric phase was recorded from the angular displacement and reaction force curves. In the final calculation the mechanical performance parameters of CMJ were always compared with those of the jumps performed without counter movement. The results indicated in general first that CMJ enhanced the average concentric force and average mechanical power by 423 N (66%) and 1158 W (81%), respectively. This potentiation effect was the higher the higher was the force at end of prestretch (p<0.001). Similarly, the prestretch speed (p<0.001) and short coupling time (p<0.01) were associated with enhanced performance during the concentric phase. The average coupling time was 23 ms. The results are interpreted through changes in the prestretch conditions to modify the acto‐myosin cross‐bridge formation so that the storage and utilization of elastic energy is associated with high prestretch speed, high eccentric force and short coupling time. The role of the reflex potentiation is also suggested as additional enhancement of the final performance.
Flow resistance of the interlobular artery in the rat kidney
Authors: BOKNAM L. , ERICSON A.‐C. , ÅBERG B. , ULFENDAHL H. R.
Published: December 2008

The afferent and efferent arterioles are considered to be the most important resistance vessels within the renal vasculature, but there are indications that a pressure drop occurs along the interlobular artery. This pressure drop was investigated from two aspects: 1) In rat kidneys the “stop‐flow pressure” in the efferent arterioles was measured with the micropuncture technique. At arterial pressures between 100 and 130 mmHg the stop‐flow pressure did not exceed 85 mmHg, which means that the highest pressure at the end of the interlobular artery was 85 mmHg; 2) A mathematical model was constructed, assuming that the diameter of the interlobular artery decreased stepwise from 60 to 10/μm. The artery was divided into 20 segments, each segment containing one afferent arteriole. The flow in the afferent arterioles increased linearly from 100nl · min‐1 in the first segment to 130nl · min‐1 in the last segment. When the pressure in the first segment was 120 mmHg, it was calculated that the pressure in the last segment was 85 mmHg. These findings strengthen the theory that the interlobular artery may participate in the regulation of the intracortical blood flow in the rat kidney. We conclude that the afferent arteriole of the most superficial nephron is nearly maximally dilated and that the juxtamedullary nephron is able to either dilate or constrict its arteriole in normotensive and normohydrated rats.
Acetylcarnitine as a contamination in the radiochemical assay of acetylcholine synthesis in salivary glands and urinary bladders
Authors: BANNS HEATHER , EKSTRÖM JÖRGEN
Published: December 2008

It was previously shown that in a radiochemical assay using anion exchange resin the capacity to synthesize acetylcholine in salivary glands was markedly overestimated unless suitable controls were introduced. By the use of paper electrophoresis of the incubation mixture it is shown that the labelled acetyl group is not only transferred from acetyl‐Coenzyme A to choline but also to carnitine in both salivary glands and urinary bladders. The two enzymes responsible for these processes, choline acetyltransferase and carnitine acetyltransferase, are shown to behave differently following denervation of the glands and bladders. Further, the adequacy of the introduced controls is demonstrated.
Neuronal and extraneuronal uptake of3H‐noradrenaline in rat portal vein in vitro
Authors: HEDNER J. , ALMGREN O. , JONASON J. , LUNDBERG D.
Published: December 2008

Rat portal veins were incubated with 3 different concentrations of3H‐l‐noradrenaline (3H‐I‐NA) and the radioactive material retained in the tissue as well as that present in the postincubation medium was analyzed after a postincubation period in substrate‐free medium. Inhibition of the neuronal amine uptake mechanism (by preincubation with LU 3–010) reduced the retention of radioactivity in the tissue more at low than at high substrate concentrations. At increasing substrate concentrations the relative role of the extraneuronal amine uptake was increased. Corticosterone and hydrocortisone reduced extraneuronal accumulation whereas betametasone and methylprednisolone in the concentrations used were ineffective, indicating that the inhibition of extraneuronal uptake by the corticosteroids is unrelated to their glucocorticoid potency. When the composition of the retained radioactivity was analyzed, NA was found to be the major component of the retained radioactivity after inhibition of extraneuronal uptake, whereas tritiated catabolites were found to be the predominating constituent of the retained radioactivity after neuronal uptake inhibition. The possible role of inactivation of the adrenergic transmitter by the extraneuronal uptake mechanism in different situations is discussed.
Effects of high oxygen tension on the metabolism of vasoactive hormones in isolated perfused rat lungs
Authors: TOIVONEN HANNU , HARTIALA JAAKKO , BAKHLE Y. S.
Published: December 2008

The effect of exposure of rats to high concentrations of oxygen (90–95%, normobaric) on the activation of angiotensin I to angiotensin II and on the inactivation of bradykinin, prostaglandin E2(PGE2) and 5‐hydroxytryptamine (serotonin) in the pulmonary circulation of isolated perfused rat lungs was investigated. After 36 h exposure, PGE2survival in the pulmonary circulation increased and reached 3 times the control value after 48 h exposure. A decrease in the conversion of angiotensin I to angiotensin II was seen after 48 h exposure. No decrease in the inactivation of 5‐hydroxytryptamine was seen until after 60 h exposure. At this time bradykinin inactivation was also decreased. The decrease in metabolism of angiotensin I and PGE2following 48 h exposure to oxygen was reversed by a subsequent exposure to room air for 12 h. In these experiments, therefore, the earliest sign of oxygen toxicity was a decrease in PGE2metabolism, a reaction associated with cells other than endothelial cells.
Cerebral circulation in acute arterial hypertension—protective effects of sympathetic nervous activity
Authors: BEAUSANG‐LINDER MARIANNE , BILL ANDERS
Published: December 2008

The cervical sympathetic chain was stimulated electrically at 6 or 3 Hz on one side in anesthetized cats. Acute arterial hypertension was induced by ligation of the aorta. Evans blue was given as tracer for protein leakage. The regional blood flow in the brain was determined by using labelled microspheres. At high blood pressures there was a multifocal breakdown of the blood‐brain barrier. The regions with breakdown had 10–20 times the normal flow rates. With a maintained hypertension regions which were overperfused at 5 min were still overperfused at 10 min, but there was little addition of new overperfused areas. Normalization of the pressure resulted in almost twice the normal flow rates in previously overperfused regions. The breakdown of the blood‐brain barrier was restricted to the non‐stimulated side, or more marked on that side. The protective effect of the sympathetic stimulation lasted more than 10 min. The results indicate that acute arterial hypertension tends to cause forced and long‐lasting vasodilation in some areas in the brain but regions which are resistant to the acute rise have an increase in the vascular tone. Sympathetic activity helps in developing this tone. Normalization of the blood pressure results in partial recovery of the vascular tone in previously overperfused regions and normalization in other areas.
Effects of diethyl‐stilboestrol on contractile response and action potential of rabbit papillary muscle
Authors: KHAN A. RAUF. , WOHLFART BJÖRN
Published: December 2008

The effects of diethyl‐stilboestrol (DES) were studied on isolated papillary muscles from rabbits (37°C). The preparation was paced at a frequency of 0.67 Hz and the muscle length was adjusted to 95 % of the length of optimum force production. Membrane potenitals and the isometric force production were recorded. DES (10 μM) reduced peak isometric force by 44.5% (mean of 6 preparations) and maximum rate of force development was reduced to approximately the same degree. The time to peak force, the time from peak force to half relaxation and the action potential duration were not significantly affected by DES. The results are consistent with the idea that DES reduces the calcium influx during the cardiac action potential without significantly influencing the calcium reuptake during relaxation. The data are compared to the effects of DES on uterine and skeletal muscles and the differences in metabolism of activator calcium in different kinds of muscles are discussed.
Influence of adenosine on responses to vagal nerve stimulation in the anesthetized rabbit
Authors: GUSTAFSSON LARS
Published: December 2008

The influence of local adenosine infusion into the celiac artery on the gastric contractile responses to centrifugal vagal nerve stimulation was studied in anesthetized rabbits, and was compared with the effects of systemic administration of equivalent amounts of adenosine. Close arterial infusion of adenosine caused a marked reduction of gastric contractions induced by nerve stimulation, whereas corresponding responses to close arterial infusions of acetylcholine were enhanced during adenosine. The comparison with systemic adenosine administration revealed that the influence on gastric neurotransmission was not related to the hypotensive effect of the compound. No effects of adenosine were seen on bronchial activity as measured by insufflation pressure. Variable effects were obtained on cardiac responses to vagal stimulation. Gastric smooth muscle contractions elicited in vitro by transmural nerve stimulation were affected by adenosine in a biphasic manner, initial inhibition followed by potentiation of the apparently cholinergic responses. It is suggested that adenosine may modulate cholinergic neurotransmission in vivo by a dual effect, prejunctional inhibition and postjunctional enhancement.
Secretory potentials in the submaxillary gland of the cat
Authors: THESLEFF PETER
Published: December 2008

Sympathetic nerve stimulation caused biphasic secretory potentials in cat submaxillary gland cells. The initial phase was a transient hyperpolarization. It was seldom seen after single shocks but nearly always occurred at high stimulation frequencies (10–20 Hz). It was imitated by phenylephrine and completely eliminated by dihydroergotamine or phentolamine and thus considered to be mediated via α‐adrenoceptors. The late phase, a depolarization, was seen even at low stimulation frequencies and could often be evoked by single shoocks. Both α‐ and β‐block reduced this response. Parasympathetic nerve stimulation evoked transient hyperpolarizations. The secretory potentials mediated via all the three receptors classes were parallelled by decreased input resistances across the acinar cell membranes.
Cerebral sodium/angiotensin interaction studied by RIA‐determination of urinary arginine vasopressin in the hydrated goat
Authors: LISHAJKO F. , APPELGREN B. , ERIKSSON S.
Published: December 2008

Radioimmunoassay determination of urinary arginine vasopressin (AVP) was employed to study quantitatively cerebral Na+/angiotensin II (A II) interaction in the hydrated goat. The solutions infused for 30 min at 0.02 ml/min into the lateral cerebral ventricle were:a) Hypertonic (0.25 M) NaCl,b) A II (0.3 ng/kg min) in isotonic (0.15 M) NaCl, andc) A II (dose as inb) in 0.25 M NaCl. The mean amounts of AVP detected in the urine in response to the various infusions were:a) 2.8 ng,b) 3.6 ng, andc) 13.3 ng. Thus, the A II/NaCl stimulation induced a detected renal excretion of AVP that was two times as large as the sum of the effects recorded in response to the separate stimuli. Infusionc) invariably induced a pronounced, long‐lasting inhibition of the water diuresis, intense thirst, and natriuresis. The corresponding effects of infusionsa) andb) were much weaker and, as regards thirst and natriuresis, inconsistent. The determinations of renal AVP excretion provide additional, and rather direct evidence for the concept of a synergistic action of elevated cerebrospinal fluid [Na+] and A II as concerns cerebral control of fluid balance. With regard to this kind of interaction, the observed dipsogenic and natriuretic effects mainly confirm earlier observations.
The isolation of endogenous modulators of the affinity of acetylcholinesterase to cholinergic ligands
Authors: HOLLUNGER E. G. , NIKLASSON B. H.
Published: December 2008

By help of a batchwise affinity chromatographic procedure the binding of cholinergic ligands to AChE obtained from caudate nucleus from calf brain was studied. The affinity of edrophonium to a crude as compared to a pure enzyme was about 50 times higher. After addition of material isolated from the crude preparation the enzyme was changed to the high affine form. The dissociation constant of the crude enzyme‐edrophonium complex determined in the affinity chromatographic experiments was 1.5×10‐5M and in enzymatic experiments 1.1×80‐7M. It is proposed that there is present in mammalian neuronal tissue a factor that increases the affinity of certain cholinergic ligands to a site other than the catalytic site on AChE.
Quantitative changes in ouabain binding after denervation and during reinnervation of mouse skeletal muscle
Authors: CLAUSEN T. , SELLIN L. C. , THESLEFF S.
Published: December 2008

Among the earliest changes following denervation of mammalian skeletal muscle fibres is a reduction of the resting membrane potential. This depolarization has been attributed to (a) a loss of the electrogenic effect of the active Na‐K‐transport across the plasma membrane (Locke & Solomon 1967); (b) a decrease in the potassium permeability of the resting plasma membrane (Klaus, Lüllmann & Muscholl 1969); (c) an increase in its sodium permeability (Robbins 1977). The purpose of the present study was to examine whether denervation affected the number of active Na‐K‐transport sites by determining the specific oubain binding to innervated, denervated and reinnervating muscles in vitro
A gonadotrophin‐releasing hormone agonist stimulates oxygen consumption and maturation of follicle‐enclosed rat oocytes in vitro
Authors: MAGNUSSON CLAES , LeMAIRE WILLIAM J.
Published: December 2008

Rat oocytes were induced to resume meiosis by incubating isolated preovulatory follicles with LH or a gonadotrophin‐releasing hormone (GnRH) agonist. Oocyte maturation was accompanied by a 32% increase in oxygen consumption by the denuded oocyte after incubation with LH and a 67% increase after incubation with the GnRH agoinst.
Inhibition of antidromic and substance P‐induced vasodilatation by a substance P antagonist
Authors: ROSELL SUNE , OLGART LEIF , GAZELIUS BERTIL , PANOPOULOS PANAGIOTIS , FOLKERS KARL , HÖRIG JOACHIM
Published: December 2008

Indirect evidence has abundantly been presented to support the view that substance P (SP) is involved in the vasodilatation following activation of fine calibre pain fibres (Lembeck & Holzer 1979). In this respect, the dental pulp is interesting since it is richly supplied with SP‐immunoreactive nerves originating from the trigeminal system (Olgart et al. 1917b, Brodin et al. 1980). These nerves are in all probability related to nociception (Henry et al. 1980). Recent observations in the cat showing that electrical stimulation of the inferior alveolar nerve produces an atropine resistant vasodilatation (Gazelius & Olgart 1980), and a release of substance P‐like immunoreactivity in the pulp (Olgart et al. 1977a, Brodin et al. 1980) are in accord with the suggested role of SP. In the present study, the availability of an antagonist to SP has made possible the further elucidation of the role of SP as a mediator of antidromic vasodilatation in the dental pulp and in the oral mucosa of the cat. We have also determined whether (D‐Pro2, D‐Phe7, D‐Trp9)‐SP specifically blocks the vascular effects of SP.
Activity of dopamine‐β‐hydroxylase (DBH) and phenylethanolamine‐N‐methyl transferase (PNMT) in heart, lung and chromaffin tissue from the Florida spotted gar, Lepisosteus platyrhincus (Holostei)
Authors: ABRAHAMSSON TOMMY , JÖNSSON ANN‐CATHRINE , NILSSON STEFAN
Published: December 2008

The activities of dopamine‐β‐hydroxylase (DBH; E.C. 1.14.17.1) and phenylethanolamine‐N‐methyl transferase (PNMT; E.C. 2.1.1.10) were estimated in homogenates from the heart. the lung and the posterior cardinal veins from Lepisosteus platyrhincus. Both enzymes could be detected in all three tissues, the activity being highest in the chromaffin tissue of the posterior cardinal veins. The activity of DBH estimated in the present in vitro experiments was about 100‐fold higher than the PNMT activity. Preliminary experiments with substrate specificity for the PNMT shows a low (heart) or undetectable (lung and cardinal veins) methylation of phenylethylamine, and the specific PNMT inhibitor SK&F 64139 (1μM) lowered the PNMT activity in all three tissues by 55–75%. The presence of PNMT in the adrenergically innervated tissues puts Lepisosteus with the teleosts and the amphibians among vertebrates with capacity for truly adrenergic, as opposed to noradrenergic, transmission.
On the adrenergic system of ganoid fish: the beluga,Huso huso(Chondrostei)
Authors: BALASHOV N. V. , FÄNGE R. , GOVYRIN V. A. , LEONT'EVA G. R. , NILSSON S. , PROZOROVSKAYA M. P.
Published: December 2008

The adrenergic system of the beluga,Huso huso, was studied by glyoxylic acid fluorescence histochemistry, analyses of catecholamine content in various organs and studies of the effects of acetylcholine and adrenaline on isolated strip preparations from blood vessels, spleen, atrium and ventricle. Chromaffin cells were found mainly in the walls of the posterior cardinal veins, and to some extent also in the wall of the celiaco‐mesenteric artery. The plasma concentration of adrenaline was high enough to affect the contraction force of the isolated atrial and ventricular strips, thus adding an adrenergic component to a possible cholinergic inhibitory vagal control of the heart. Fluorescence histochemistry revealed no direct adrenergic innervation of the heart, but blood vessels in the heart and elsewhere received a rich supply of adrenergic nerve terminals. Adrenaline contracted the celiaco‐mesenteric artery and the spleen, and produced positive inotropic effects on the paced atrial and ventricular strip preparations. Acetylcholine contracted the ventral aorta and the celiaco‐mesenteric artery, and reduced the contraction force of paced ventricular and, especially, atrial preparations. It is concluded that the beluga has a well developed adrenergic system consisting of both chromaffin cells and adrenergic neurons with varicose nerve terminals of the type found in the higher vertebrates.
Release of adenosine from rat lung by antigen and compound 48/80
Authors: FREDHOLM BERTIL B.
Published: December 2008

The mechanism by which theophylline inhibits anaphylactic constriction of the airways is not known (Bowman & Rand 1980). Part of its activity may be due to inhibition of cyclic nucleotide breakdown, part to antagonism of endogenous adenosine since theophylline is a potent inhibitor of adenosine actions in therapeutic concentrations of the drug (Fredholm 1980). Adenosine is known to potentiate mediator release from mast cells (Marquardt et al. 1978, Fredholm & Sydbom 1980) and it antagonizes the direct tracheorelaxant effect of theophylline (Fredholm et al. 1979). I have examined the possibility that lung is capable of releasing adenosine and that the release is enhanced by anaphylactic and pseudoanaphylactic reactions.
Arterial baroreceptor reflex function during elevation of intracranial pressure
Authors: LITTLE R. A. , ÖBERG BENGT
Published: December 2008

The ability of the arterial baroreceptor reflex to buffer the blood pressure responses elicited by increasing the intracranial pressure (ICP) has been studied in chloralose anesthetized cats. Standardized elevations of ICP induced pressor responses of similar magnitude irrespective of whether the baroreceptor inhibitory activity was high or very low. When ICP was elevated baroreceptor activation induced a reflex reduction of flow resistance and blood pressure, but never to the same levels obtained when ICP was normal. Thus when ICP was elevated there was an upward displacement of the curve relating carotid sinus pressure to mean arterial blood pressure.
Evidence against a role of cyclic nucleotides in the regulation of anaphylactic histamine release in isolated rat mast cells
Authors: SYDBOM ANITA , FREDHOLM BERTIL , UVNÄS BÖRJE
Published: December 2008

The effect of different phosphodiesterase (PDE) inhibitors on the antigen or 48/80 induced histamine release from isolated Hooded Lister rat mast cells was tested. The unselective PDE inhibitors theophylline (2.5 mM) and IBMX (0.2 mM) and the selective cyclic GMP PDE inhibitor M & B 22948 (0.1 mM) inhibited the antigen induced histamine release by 50% while 48/80 induced release was inhibited by about 25%. The cyclic AMP selective PDE inhibitors ICI 63197 (0.5 mM) or Ro 20–1724 (0.2 mM) had no effect on 48/80 induced histamine release but tended to enhance antigen induced release. There was no correlation between the measured levels of cyclic AMP and the effect on histamine release by the
VIP nerve fibres around peripheral blood vessels
Authors: UDDMAN ROLF , ALUMETS JAN , EDVINSSON LARS , HÅKANSON ROLF , SUNDLER FRANK
Published: December 2008

By immunocytochemistry nerve fibres containing vasoactive intestinal polypeptide (VIP) were demonstrated around many peripheral blood vessels in the cat. Such nerve fibres were particularly numerous around arteries in the upper respiratory, gastrointestinal and genito‐urinary tracts. They were less numerous around large arteries and veins and seemed to be absent from blood vessels in the liver, spleen and kidney. VIP nerve fibres were few around blood vessels in skeletal muscle and absent in coronary arteries. Administration of VIP in vitro relaxed all arteries tested provided they had been given an increased tone, for instance by preincubation with PGF2α. It is likely that VIP in vascular nerve fibres may participate in the regulation of systemic and local blood flow.