bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lowered Sensitivity to Acetylcholine in Hearts from Cold‐Acclimated Rats and Frogs
Authors: Harri M. N. E. , Tirri R. 
Published: December 2008

AbstractThe sensitivity of the heart to the negative chronotropic effect of acetylcholine (ACh) was measuredin vivofrom denervated hearts of the rat and frog before and after they were acclimated to cold. In the frog the possible seasonal changes in sensitivity were also observed. In the rat, cold acclimation lowered the sensitivity to ACh. This change was significant already at 3 days after cold exposure. Cold acclimation lowered the sensitivity to ACh also in the frog, but only during the winter. On the other hand, summer frogs were much niore sensitive to ACh than winter frogs. It was concluded that it is the increased parasympathetic activity in the cold‐acclimated rat and in the winter frog which results in the lowering of sensitivity to ACh.
On the Mechanism of the Enhancement by Smooth Muscle Stimulants of the Motor Responses of the Guinea‐pig Vas Deferens to Nerve Stimulation
Authors: Sjöstrand Nils O. , Swedin Göran 
Published: December 2008

AbstractLow concentration of various agonists: acetylcholine, adrcnaline, noradrenaline, histamine, serotonin, barium chloride, bradykinin, eledoisin, substance P and angiotensin enhance the motor responses of the nerve stimulated guinea‐pig vas deferens considerably. A similar effect can also be obtained by prostaglandins E1 and E2 although these drugs generally depress the responses of the nerve stimulated vas deferens. By a comparison with the actions of the agonists on the contractions of nerve stimulated vasa deferentia and on contractions of electrically stimulated denervated or tetrodotoxin paralyzed vasa deferentia it is concluded that with the exception of angiotensin and the prostaglandins, the agonists have their main action post‐junctionally on the smooth muscle cells. Angiotensin has mainly a prejunctional action but acts also in part postjunctionally. The prostaglandins have a depressant prejunctional action but a stimulant postjunctional action.
The Effects of Intestinal Vasodilator Mechanisms on the Rate of 85Kr Absorption in the Cat
Authors: Biber Björn 
Published: December 2008

AbstractThe absorption rate of 85Kr from the small intestine of the cat was estimated during intestinal vasodilatation induced by transmural electrical field stimulation or by local i.a. infusions of cholecystokinin and secretin. As blood flow increased, a considerably augmented rate of absorption was observed, the absorption rate being increased in excess of that observed during corresponding hyperemia induced by isopropylnoradrenaline. An increased fraction of the intramural blood flow became fully equilibrated with luminal contents during the vasodilatory procedures.
Some Chemical and Biological Properties of a Protein Fraction from Nigerseed (Guizotia Abyssinica Cass.) Soluble in Hot Aqueous Ethanol
Authors: Eklund Anders 
Published: December 2008

AbstractA nigerseed protein fraction soluble in a hot water‐ethanol solution of sodium chloride was isolated. It contained high levels of cystine and chlorogenic acid and inhibited the proteolytic digestion of casein by trypsin in vitro. Weanling male rats failed to grow when fed on this protein fraction as the sole source of protein. Histo‐pathological examinations of the main animal organs did not show any abnormalities.
Rates of Transvascular Fluid Filtration in Lungs from Normal and Thrombocytopenic Rabbits
Authors: Aursnes I. , Hauge A. , Waaler B. A. 
Published: December 2008

AbstractThe rate at which fluid is filtered out of the vessels on standardized elevations of left atrial pressure (Pla) has been tested in isolated lungs from normal and thrombocytopenic rabbits. Higher filtration rates were found in the lungs from normal than in the lungs from thrombocytopenic animals both during plasma and during blood perfusion. The filtration rates from the two groups of lungs were significantly different both at Pla elevations of 10 mm Hg (p = 0.008, two‐sided test) and at Pla elevations of 15 mm Hg. The reason for this difference is not clear. One possibility is that lungs in thrombocytopenic animals may be protected against changes occurring during the surgical procedures necessary for removal of the organ.
Effect of TRH, and Short‐term Exposure to Experimental Stress or Cold on the Serum Immunoassayable TSH Concentration in the Rat
Authors: Leppäluoto J. , Ranta T. , Lybeck H. , Varis R. 
Published: December 2008

AbstractThe influence of TRH, transfer and sampling stress and cold on the blood TSH level was studied in female rats using a specific radioimmunoassay for rat TSH. The maximum response to TRH increased with the dose of TRH and occurred at 5 min with 10 and 50 ng. With a TRH dose of 250 ng the niaxirnum response occurred at 10 min. Transfer stress caused a significant rise in serum TSH level at 5 min. After this, the serum TSH level gradually decreased and the decrease at 30 min was significant compared with 5 min value. Sampling stress caused a slight increase in the serum TSH level at 5 min, and at 30 and 60 min the serum TSH level was significantly lower than ir. controls. The maximum effect of cold on the blocd TSH level was seen in animals kept for 30 min at 5° C. These studies clearly demonstrate the effect of TRH on the serum TSH level in rats. The activation of the secretion of TSH in the cold is physiologically relevant, and the inhibition of TSH secretion in response to stress refutes the hypothesis that stressful stimuli activate the thyroid gland.
The Neuromuscular Blocking Action of an Isolated Toxin from the Elapid (Oxyuranus scutellactus)
Authors: Kamenskaya Marina A. , Thesleff S. 
Published: December 2008

AbstractIntravenous administration of the neurotoxin (taipoxin) to mice caused after a latent period death by respiratory paralysis. The length of the latent period varied with dose, the dose‐response relation being bilogarithmic. Taipoxin failed to affect the resting membrane potential and the action potential of muscle. It caused a slight reduction in the acetylcholine sensitivity of the muscle membrane. The main effect of taipoxin on neuromuscular transmission was to reduce spontaneous and evoked transmitter release. The frequency of spontaneous miniature end‐plate potentials (m.e.p.p.s) was reduced to complete stop and depolarization of nerve terminals by a high potassium concentration (20 mM) failed to cause a marked and sustained increase in m.e.p.p. frequency. With nerve stimulation the amplitude of end‐plate potentials (e.p.p.s.) was reduced and with repetitive stimulation the amplitude of e.p.p.s. rapidly fell to a low level. Post‐tetanic facilitation of m.e.p.p. frequency and of e.p.p. amplitude were absent. The shape of evoked e.p.p.s. indicated asynchronous release of transmitter quanta. The effects of the toxin on neuromuscular transmission progressed even when the muscle was removed from the animal and placed in toxin‐free bathing fluid. In vitro experiments showed that the rate of onset of neuromuscular block depended on the temperature of the bathing solution and on the degree of activity at the neuromuscular junction. Thus, incubation in toxin solution during 4 hr at 28° C failed to produce a neuromuscular block while at 37° C the block was complete within 1 h. With nerve stimulation at 10 Hz for 2 s every 2 min the rate of blockade was more rapid than in unstimulated preparations, similarly 20 mM potassium in the bathing fluid enhanced the rate of blockade.
Lactate Production and Anaerobic Work Capacity after Prolonged Exercise
Authors: Asmussen E. , Klausen K. , Nielsen L. Egelund , Techow O. S. A. , Tønder P. J. 
Published: December 2008

AbstractIt has been found that previous heavy or long‐lasting exercise results in a diminished ability to raise the blood lactate concentration by exhaustive supermaximal work (Hedman 1957, Astrand et al. 1963, and others). No definitive explanation for this phenomenon has been given. It was the purpose of the present experiments to throw light on the question whether a diminishing store of carbohydrates in the body could be the cause for the declining ability to liberate energy anaerobically by breakdown of glycogen to lactic acid. In 3 subjects the stores of glycogen were presumed to be varied 1) by repeated bouts of supermaximal and submaximal exercise on the bicycle‐ergometer, and 2) by diet after previously depleting the carbohydrate stores by exercise. It was found that in all cases the ability to work anaerobically and to produce lactate decreased with decreasing amounts of available carbohydrate. Disturbances in water or electrolyte balance were avoided. It is tentatively suggested that the velocity of the enzymatic process glycogen—glucose‐1‐phosphate is the limiting factor, and that this process is slowed down by lactic acid accumulation, the more the lower the substrate (glycogen) concentration is. Glucose, which enters the glycogenolytic chain as glucose‐6‐phosphate, can partly restore the ability for lactate production.
Changes in the Concentration and Fatty Acid Composition of Phospholipids in Rat Skeletal Muscle during Postnatal Development
Authors: Bruce ÅKe 
Published: December 2008

AbstractRat skeletal muscle was analysed at different ages, from birth to 90 days, for its concentration of phospholipids and individual phosphoglycerides, and for the fatty acid pattern of cardiolipin, choline phosphoglyceride (CPG), ethanolamine phosphoglyceride (EPG), inositol phospho‐glyceride and serine phosphoglyceride (SPG). The concentration of phospholipids was found to increase between birth and two weeks of age, after which it decreased slightly to 14 μmol/g fresh weight at the age of 90 days. The relative amount of CPG and EPG varied but little with age, while that of cardiolipin increased to three times its original value. The concentration of polyenoic acids increased with age in all phosphoglycerides except SPG. The concentration of the sum of the fatty acids of the linoleic acid series in CPG increased rapidly during the first weeks of life, while that of the linolenic acid series increased throughout the period studied. In EPG the concentration of the sum of the fatty acids of the linolenic acid series increased, while that of the linoleic acids decreased and the concentration of linoleic acid in cardiolipin increased. In the muscles of 90‐day‐old rats, the fatty acid pattern of cardiolipin showed a high level of linoleic acid and no fatty acids of the linolenic acid series. The fatty acid pattern of CPG was characterized by rather high levels of both linoleic and arachidonic acids and that of EPG by a high concentration of the fatty acids of the linolenic acid series.
Glycogen Storage and Glycogen Synthetase Activity in Trained and Untrained Muscle of Man
Authors: Piehl K. , Adolfsson S. , Nazar K. 
Published: December 2008

AbstractBilateral biopsies from “one‐leg” trained subjects were analysed for glycogen content (G), total glycogen synthetase activity (GST), synthetase I‐form (GSI) and hexokinase (HK). Histochemical estimations were made of G, GST and GSI in slow twitch (ST) and fast twitch (FT) muscle fibres. Samples from the trained (T) and the untrained (U) legs were taken before and after acute exhaustive exercise and at different intervals during a 46 h recovery period when a carbohydrate enriched diet was given. Prior to exercise G levels were higher (32 %) in T‐leg than in U‐leg. Throughout the experiment T‐leg showed higher activity for GST (35%) and HK (18%). In both U‐ and T‐legs GSI activity increased (from 16 to 48 %) after exercise. The increase in GSI was histochemically found mainly in ST fibres in both T‐ and U‐leg, while the staining intensity for GST was similar in ST and FT fibres. During the recovery period, G was restored and GSI gradually declined to resting values. The rate of synthesis was the same in T‐ and U‐legs and in the two fibre types.
Regional Cerebral Blood Flow in the Rat Measured by the Tissue Sampling Technique; a Critical Evaluation Using Four Indicators C14‐Antipyrine, C14‐Ethanol H3‐Water and Xenon133
Authors: Eklöf B. , Lassen N. A. , Nilsson L. , Norberg K. , Siesjö B. K. , Torlöf P. 
Published: December 2008

AbstractThe validity of the assumptions inherent in the tissue sampling technique for measuring cerebral blood flow was tested in the rat, using the 4 indicators C14‐antipyrine, C14‐ethanol, H3‐water and Xenon133. Each one of the indicators was infused i.v. during either 30, 60 or 120 s and the blood flow was calculated from the integrated arterial curve and from the tracer concentration in the tissue. The calculated flows varied with the time of infusion, and at high perfusion rates all tracers gave flow values that were lower than those obtained with the Kety and Schmidt technique. For C14‐antipyrine, the method gives an error already at normal perfusion rates. It is concluded that the cerebral uptake of the tracers is diffusion‐limited, and that the tissue sampling technique cannot be used for quantitative measurement of cerebral blood flow in high flow situations. However, the error of the method is considerably reduced if C14‐ethanol is used and if the time of infusion is limited to 30 s.
Distribution of Renal Cortical Blood Flow during Hemorrhagic Hypotension in Conscious Dogs
Authors: Kirkebö A. , Tyssebotn I. 
Published: December 2008

AbstractThe effect of hemorrhagic hypotension on distribution of renal cortical blood flow was investigated in 9 conscious dogs. 6 platinum electrodes were chronically implanted in inner and outer renal cortex and local cortical blood flow measured by hydrogen clearance. Urine was collected through a catheter implanted in the split bladder and total renal blood flow f RBF) determined by PAH clearance. In anesthetized dogs control blood flow averaged 3.72 ± 0.74 ml/min‐g in outer cortex and 3.60 ± 0.53 ml/rnin g in inner cortex. Local blood flow in conscious dogs fell to 30–60 % of control in the course of 11 days after implantation of the electrodes, though RBF was almost constant and filtering glomeruli were demonstrated in the small fibrotic zone (20–50 μ) close to the electrode tip. No change in local flow was found by induction of Nembutal anesthesia. Bleeding of conscious dogs 1–3 days after implantation, to mean arterial pressure 50 mm Hg, reduced local blood flow to 10–30 % of prebleeding control. The local blood flow in outer and inner cortex decreased near proportionately. Typically, flow at all electrode sites in outer and inner cortex showed a similar fall. A marked redistribution of cortical blood flow during hemorrhagic hypotension was never observed. Bilateral clamping of carotid arteries at normal and at low arterial pressures did not change outer or inner cortical blood flow.
Autoregulation of Capillary Hydrostatic Pressure in Skeletal Muscle during Regional Arterial Hypo‐ and Hypertension
Authors: Järhult Johannes , Mellander Stefan 
Published: December 2008

AbstractNet transcapillary fluid movements in the sympathectomized cat skeletal muscle were observed in response to regional mean arterial pressure variations in the range from 30 to 170 mm Hg. The transcapillary Starling fluid equilibrium prevailing at normal perfusion pressure was found to be roughly maintained over the entire range of arterial hypo‐ and hypertensions, indicating an approximate constancy of capillary hydrostatic pressure (pc). This “autoregulation of pe” was mainly due to active changes of vascular tone in the precapillary resistance vessels causing a resetting of the pre‐ to postcapillary resistance ratio (ra/rv), but disappeared after abolition of vascular tone by papaverine. In the lowest pressure range, a passive rise of postcapillary resistance contributed to the resetting of ra/rv. By this autoregulation of pc the muscle tissue is protected against undue redistributions of fluid between the intra‐ and extravascular spaces when arterial pressure per se is changed.
Effect of Lowered CSF Sodium Concentration on the Central Control of Fluid Balance
Authors: Eriksson Lea 
Published: December 2008

AbstractIsotonic and hypertonic non‐electrolyte solutions were slowly infused into the cerebral ventricular system of conscious goats in normal water balance. Infusions of all the isotonic solutions induced water diuresis. When the infusions were made into the anterior part of the lateral ventricle, the response was more delayed than when the solutions were infused into the third ventricle. Also, hypertonic (0.45 M or 0.6 M) solutions of d‐glucose, d‐fructose, glycerol, and sucrose turned renal CH2O positive. Hypertonic urea, instead, gave inconsistent responses. The observed increase in renal CH2O obviously resulted from an inhibition of the normal release of ADH. Firstly, there was no increase in renal C0sm; and secondly, intravenous injection of ADH interrupted this water diuresis. No obvious changes occured in renal electrolyte excretion, blood pressure, and heart rate during infusions. After infusions, when CH2O returned to the preinfusion level, there was sometimes a slight increase in sodium excretion and blood pressure. Infusions of isotonic saccharides in physiologic saline did not induce water diuresis under infusions, but after infusions there was (in 4 out of 6 cases) some increase in urine flow and CH2O could become positive for 10 to 20 min.These results indicate that, instead of osmolality, the ionic composition of CSF is important for ADH release, and support the concept of a Na+ sensitive receptor system near the third ventricle.
The Effect of Glycerol on the Postexercise Lactate Clearance
Authors: Olsen Christian , Petersen Ebbe Strange 
Published: December 2008

AbstractThe effect of increased glycerol concentrations induced by peroral intake of glycerol on the concentrations of lactate and pyruvate in blood was investigated in 7 young adults at rest and after exercise. 10 mill of work on a bicycle ergometer induced a small but statistically significant rise in the glycerol concentration. The concentration of lactate at rest was significantly higher after than before glycerol intake. The lactate/pyruvate ratio was significantly higher after than before glycerol intake both at rest and after 15 min of recovery and onwards. The metabolic clearance of lactate after exercise was reduced by the glycerol intake to about 70% of the control value. The effect of glycerol on the metabolic clearance of lactate was the same whether estimated at rest or after exercise. These observations are in accordance with the concept, that glycerol metabolism influences the lactate/pyruvate ratio in the liver and thereby reduces the clearance of lactate.
Morphology and Storage Properties of Rat Mast Cell Granules Isolated by Different Methods
Authors: Anderson Per , Röhlich Pál , Slorach Stuart A. , Uvnäs Börje 
Published: December 2008

AbstractPure granule fractions were obtained from rat mast cells by sonication in sucrose for different times and at different amplitudes. Two types of mast cell granule were found. One type appeared dark blue in the light microscope when stained with toluidine blue–azur A and was homogeneous, electron dense and surrounded by a trilaminar membrane when observed in the electron microscope; thus this type had the same appearance as mast cell granulesin situ.The second type appeared pink after staining with the above dye and had a swollen, reticular appearance with a reduced electron density and no surrounding membrane when observed in the electron microscope. With increasing sonication time and amplitude there was an increase in the proportion of the swollen, less electron dense granules with no surrounding membrane and a concomitant decrease in the amount of histamine retained (as shown by the histamine/ heparin and histamine/protein ratios) after washing in isotonic sodium chloride. Granules isolated from water‐lysed mast cells or mast cells treated with compound 48/80 were all of the second type with no perigranular membrane: they released their histamine when suspended in isotonic sodium chloride solution.
The Effect of Barbiturate on Retinal Functions. II. Effects on the c‐wave of the Electroretinogram and the Standing Potential of the Sheep Eye
Authors: Knave Bengt , Persson Hans E. , Nilsson Sven Erik G. 
Published: December 2008

AbstractThe present work is the second in a series of investigations on the effect of barbiturate on retinal functions. The changes in the c‐wave of the conventional ERG and in the standing potential (SP) of the intact sheep eye were studied after i.v. administration of an ultra‐short‐acting barbiturate, thiopental. The c‐wave was transiently decreased or abolished after a small dose (< 10 mg/kg), whereas a negative shift could be observed in the SP. Larger doses resulted in negative‐positive cyclic variations of the c‐wave amplitude and the SP resembling damped oscillations. There was an increase of the a‐ and b‐waves after barbiturate administration, not related to the SP‐changes. The effect of barbiturate on the components of the conventional ERG and the SP was also studied after selective blocking of the function of the pigment epithelial cells with sodium iodate. Hereby, the barbiturate induced changes of the c‐wave and the SP disappeared, whereas those of the a‐ and b‐waves remained. On the basis of these results, the possibility that barbiturate has a dual site of action on the retina, namely on the neuroretina and on the pigment epithelial cells, cannot be excluded.
The Effect of Barbiturate on Retinal Functions. III. Effects on the Isolated Receptor Responses and the Inner Nuclear Layer Components in the Low‐intensity Electroretinogram of the Sheep Eye
Authors: Knave Bengt , Persson Hans E. 
Published: December 2008

AbstractThe present study is the third in a series of investigations on the effects of barbiturate on retinal functions. The changes in the isolated receptor responses and inner nuclear layer components of the low‐intensity electroretinogram (ERG) of the intact sheep eye were studied after i.v. administration of an ultra‐short‐acting barbiturate, thiopental. The low‐intensity ERG, i.e. the electroretinographic responses below the b‐wave threshold, have recently been shown to consist of a slow corneanegative receptor potential and two d.c. responses of opposite polarity presumably generated in the inner nuclear layer. The administration of small doses of thiopental (5 mg/kg) had no effect on the receptor response, whereas larger doses (10 mg/kg) increased its amplitude. The most striking effect of thiopental was an enhancement of the positive d.c. response, which could be observed already at barbiturate doses of 5 mg/kg. The results are consistent with the assumption that barbiturates primarily influence the cells of the inner nuclear layer and secondly the receptors. It is suggested that the functional mechanism behind the barbiturate effect on the inner nuclear layer (as expressed in the increase of the positive d.c. component) constitutes an intraretinally mediated disinhibition of the “on‐type”‘ bipolar cells i.e. the presumed generators of the positive d.c. component.