bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Arterial Hypoxia and Unilateral Carotid Artery Occlusion upon Regional Blood Flow and Metabolism in the Rat Brain
Authors: Salford Leif G. , Siesjö Bo K. 
Published: December 2008

AbstractThe influence of marked arterial hypoxia combined with unilateral carotid artery clamping upon regional cortical metabolites and blood flow was studied in the rat brain. When the arterial Po, was reduced to about 20 mm Hg the hemisphere on the clamped side showed a marked lactic acidosis and a fall in phosphocreatine but the adenylate energy charge remained close to normal. In this hemisphere, the cortical blood flow increased about 4‐fold. On the clamped side there was an excessive lactic acidosis and a marked fall in energy charge. However, since the levels of glucose, glucose‐6‐phosphate and pyruvate did not fall below normal, and since the regional blood flow was at least doubled, it is concluded that the derangement of the energy metabolism was due to cellular hypoxia, exaggerated by the relative ischemia induced by the carotid artery clamping. The biochemical lesion was most pronounced in the distribution territory of the middle cerebral artery that also showed the largest degree of relative ischemia. It is suggested that the pronounced lactic acidosis may contribute to the neuronal damage observed with this model of hypoxia and relative ischemia.
Effects of Alpha‐ and Beta‐Receptor Blocking Agents on Catecholamine and 5‐Hydroxytryptamine Induced Peroxidase and Amylase Secretion from Guinea Pig Submandibular Gland
Authors: Carlsoo Bengt , Danielsson Ake , Marklund Stefan , Stigbrand Torgny 
Published: December 2008

AbstractEnzyme secretion from incubated guinea pig submandibular gland slices was induced by adrenaline, noradrenaline, dopamine, 5‐hydroxytryptamine or dibutyryl cyclic AMP combined with theophylline. Effects of alpha‐ and beta‐blocking agents on stimulated peroxidase and amylase discharge were studied. Propranolol (beta‐blocker), but not phenoxybenzamine (alpha‐blocker), markedly inhibited the secretion of both enzymes induced by adrenaline or noradrenaline. Dopamine and 5‐hydroxytryptamine were found to be potent enzyme secretagogues. Both propranolol and phenoxybenzamine antagonized the effects of these two amines. The secretagogic effect of dibutyryl cyclic AMP in combination with theophylline was not affected by either propranolol or phenoxybenzamine. L‐DOPA and 5‐hydroxytryptophan were without effect on enzyme secretion. It is concluded that peroxidase and amylase are secreted in parallel from guinea pig submandibular gland and that enzyme release is mainly mediated via the beta‐adrenergic receptor.
Transient and Steady State Effects of C02 on Mechanisms Determining Rate and Depth of Breathing
Authors: Bradley G. W. , Euler C. von , Marttila Irja , Roos B. 
Published: December 2008

AbstractBreath‐by‐breath analysis of tidal volume, VT, inspiratory duration, Tr, and expiratory duration, TE, was performed on cats under light pentobarbitone anesthesia or after decerebra‐tion before and after vagotomy. In response to step changes in inspired CO2 VT changes earlier and more rapidly than the corresponding changes in the timing. The VT–Tj points may thus form a ‘hysteresis loop’ embracing the volume threshold curve of Clark and Euler (1972). The transient responses were present also after peripheral chemodenervation and after bilateral vagotomy. In contrast to earlier papers vagotomized cats under pentobarbitone anesthesia often showed some decrease of T(with increased steady state CO2 levels. In decerebrate vagotomized cats T[was more independent of variations in steady state PCO2 levels, but after administration of pentobarbitone Ti showed some steady state shortening of Tj with increased CO2. It is concluded that the controller of depth and rate of breathing contains at least 2 functional components which depend on PCO2 in such a way that they exert opposite effects on Ti which cancel out to a great extent and that this relative match can be disturbed by pentobarbitone. It is postulated that the transient increase in mismatch is due to the fact that the 2 (or more) CO2 effects have slightly different dynamic features.
Steady State Effects of CO2 and Temperature on the Relationship between Lung Volume and Inspiratory Duration (Hering‐Breuer Threshold Curve)
Authors: Bradley G. W. , Euler C. von , Marttila Irja , Roos B. 
Published: December 2008

AbstractThe time course of the volume threshold curve for the inspiratory off‐switch, i.e. the relationship between volume, (Vx) and inspiratory duration (Tj) with intact vagus nerves, was determined in steady conditions at different inspired CO2 concentrations and body temperatures in lightly anesthetized cats by means of ‘ramp’‐shaped inflations and deflations of different rise times. With intact vagal feedback the Vx–TT data points could be very well fitted to hyperbolas in all conditions studied. Changes in steady state FACO2 never caused any detectable influence on the volume threshold curves. Changes in body temperatures, in a range below the panting threshold, caused pronounced effects on the volume threshold curve which could best be characterized as a shift of the whole curve along the volume axis to lower values with increased temperature. Thus, at each rate of volume expansion the threshold for inspiratory off‐switch was reached earlier the higher the temperature. Also in the absence of vagal volume feed‐back Ti became correspondingly shorter with increased temperature which indicates that these temperature effects are mainly of central origin. The mechanisms for the CO2 and temperature effects on tidal volume and inspiratory duration are discussed.
Single‐Nephron Filtration during Hemorrhagic Hypotension in the Conscious Rat
Authors: Clausen Gunnar , Tyssebotn Ingvald 
Published: December 2008

AbstractTo decide whether redistribution of filtrate between superficial (S) and deep (D) nephrons takes place when GFR is reduced by hemorrhagic hypotension (HH) the amount of filtered 14C ferrocyanide precipitated as Prussian blue in single S and D nephrons was determined in rats during HH of 80, 65 and 50 mm Hg mean arterial pressure (AP). Marked filtration and urine flow persisted only in the AP 80 mm Hg group, whereas the major fraction of nephrons had ceased filtration in four out of live rats at AP 50 mm Hg. The distribution of radioactivity between S and D proximal tubules was not altered in any of the HH groups as compared to normotensive controls.
Afferent G Units Responding to Mechanical, Thermal and Chemical Stimuli in Human Non‐Glabrous Skin
Authors: Torebjörk H. Erik 
Published: December 2008

AbstractC unit activity was recorded with microelectrodes from intact sensory fascicles in the human peroneal nerve. The analysis includes 46 afferent units with receptive fields predominantly on the dorsum of the foot and ankle. 16 units were tested quantitatively. Another 30 units were tested qualitatively by a combination of electrical and natural stimuli in the skin. This method was valuable for a reliable identification of activity in individual afferent C elements, when several C units with similar potential amplitudes responded to testing in the skin. The units were not spontaneously active at normal skin temperatures but one unit showed a low frequency discharge at a skin temperature of 22o C. Cooling by ether evaporation was an inefficient stimulus except for 2 units. Gentle mechanical stimuli did not activate any of the units, whereas afferent C unit impulses were induced by moderately intense mechanical stimuli, noxious heat and various chemical irritants. The sensations produced by stimuli inducing intense afferent C unit activity were reported as “burning or delayed pain”, whereas stimuli eliciting low frequency activity often were reported as “itch”. It is concluded that polymodal C receptors, similar with “polymodal nociceptors” in the cat and monkey, are numerous in skin areas sparsely covered with hairs on the dorsum of the foot and ankle in man, whereas no low threshold C mechanoreceptors were identified. The experiments do not exclude the possibility that both delayed pain and burning itch sensations may be mediated by different impulse patterns from polymodal C receptors.
A Serum Factor Influencing the Physiological Activity of Thyrotropin‐Releasing Hormone (TRH) I. Studies with human serum
Authors: Virkkunen Pekka 
Published: December 2008

AbstractThyrotropin‐releasing hormone was incubated at 2° C, 37° C and 60° C with varying dilutions of human serum and with serum fractions obtained by gel filtration. The amount of TRH left after incubation was measured by bioassay. The inactivation of TRH was shown to be complete by 90 min, the half‐time being 18 min. Dilution of serum more than 1: 16 did not abolish TRH. Binding of TRH to serum proteins could not be detected. Instead of this evidence is submitted for the enzymic nature of the serum protein which inactivates TRH. In gel filtration this protein migrates between the globulins and albumin, which suggests a molecular weight of about 100,000.
The Effect of Angiotensin on Isosmotic Fluid Absorption by the Rabbit Gail‐Bladder In Vitro
Authors: Leyssac P. P. , Kristensen L. Østergaard , Christensen P. , Frederiksen O. 
Published: December 2008

AbstractThe rabbit gall‐bladder in vitro preparation was used for studying the effect of angiotensin‐11 on isosmotic fluid transport. Angiotensin inhibited net fluid transfer at serosal concentrations between 10‐9‐10‐8 M. Maximum inhibition (about 25 %) was obtained at a concentration of 5 times 10˜* M. No significant effect was demonstrable at concentrations of 10‐10 M or lower, and the effect disappeared at higher concentrations (10 and 20 × 10‐9 M). The inhibitory effect was due to a depression of the unidirectional Na+‐efflux (from mucosal to serosal side); Na+‐influx (from serosal to mucosal side) was unaffected. Maximum effective doses of angiotensin had no effect on transepi‐thelial potential difference (PD), while ohmic resistance (R) increased slightly (about 10 %). The inhibitory effect of angiotensin was significantly reduced by incubating gall‐bladders with indomethacin (10 μg/ml) which effectively blocks prostaglandin biosynthesis. Addition of indo‐methacin alone had no effect on either net fluid transfer rate, PD, or R. It is concluded that angiotensin inhibits isosmotic fluid transport in the gall‐bladder by an effect on the active component of the transfer process; and the data suggest that the effect is indirect and mediated, in part at least, by release of endogenous prostaglandins. Alternatively indomethacin might interfere with the angiotensin receptor.
A Serum Factor Influencing the Physiological Activity of Thyrotropin‐Releasing Hormone (TRH) II. Studies with rat serum in vivo and in vitro
Authors: Virkkunen Pekka , Lybeck Harry , Ranta Tapio , Leppäluoto Juhani 
Published: December 2008

AbstractThe mid‐fractions in gel filtration of rat serum proteins were shown to be the most potent in abolishing the biological activity of TRH during incubation in vitro. The kidneys were not able, in vitro or in vivo, to restore the biological activity of inactivated TRH. Biologically active TRH, labelled TRH and serum‐inactivated labelled TRH were excreted in the urine in equal amounts.
Pulmonary Responses to Intravascular Platelet Aggregation in the Cat
Authors: Vaage J. , Bø G. , Hognestad J. 
Published: December 2008

AbstractPlatelet aggregation has been induced in cats by intravenous infusions of ADP, collagen or platelet antiserum, and the airway and pulmonary vascular responses subsequent to such infusions have been studied. Dynamic lung compliance (dyn CL), pulmonary resistance (RL) and the number of circulating platelets were followed together with pulmonary vascular resistance (PVR). Induction of platelet aggregation caused temporary and parallel increases in PVR and in RL and a simultaneous decrease in dyn CL. The major part of these effects was apparently due to active smooth muscle constriction. It could be shown that airway and vascular responses declined and finally disappeared in a characteristic way after repeated episodes of platelet aggregation. The total number of circulating platelets is apparently not the key factor in this connection. The way in which aggregation is induced, as well as the functional state of the circulating platelets, appear to be more important factors. It may be that the platelet release recation is mandatory for the lung responses to intravascular platelet aggregation.
Comparative Studies on the Effects of Bradykinin and Vagal Stimulation on Motility in the Stomach and Colon
Authors: Fasth S. , Hultén L. , Jahnberg T. , Martinson J. 
Published: December 2008

AbstractThe effect of bradykinin on gastric and colonic motility was studied in anaesthetized cats with volume recording devices and compared with the effects of vagal nerve stimulation. When administered intra‐arterially bradykinin caused a profound and prolonged gastric relaxation. Simultaneously there was a marked and likewise prolonged colonic contraction. The gastric relaxation closely mimicked the atropine resistant relaxation elicited by vagal nerve stimulation. These effects could not be blocked by antiadrenergic drugs and it is suggested that bradykinin and the unknown transmittor substance(s) released on vagal stimulation act in a similar way on the gastric smooth muscles and that a kinin mechanism may be involved in the vagal response. As regards the colonic motor response it was shown that bradykinin does not reproduce the vagal motility effects on colon smooth muscle but mimicks closely the atropine resistant expulsive contraction elicited by activation of the pelvic nerves.
Circulatory Effects Evoked by ‘Physiological’ Increases of Arterial Osmolality
Authors: Jkrhult Johannes , Hillman Jan , Mellander Stefan 
Published: December 2008

AbstractThe effects of moderate arterial hyperosmolality (+ 20 mOsm/kg H2O), produced by short term intravenous hypertonic infusion, on vascular resistance in skin, skeletal muscle, intestine, and kidney were analysed in the anesthetized cat. Vascular resistance decreased in all four regions in response to the hypertonicity both before and after regional sympathectomy and the effects were not significantly altered by β‐adrcno‐ceptor blockade. Arterial blood pressure rose during the hypertonic infusion despite the decreased vascular resistance and an unchanged heart rate, indicating an increased stroke volume and cardiac output. Similar increases of arterial osmolality are known to occur in heavy exercise and in hemorrhage. The present results may therefore suggest that blood borne hyperosmolality is a factor which can contribute to the overall cardiovascular adjustments in these situations.
Relationship between Isometric Endurance and Fibre Types in Human Leg Muscles
Authors: Hultén B. , Thorstensson A. , Sjödin B. , Karlsson J. 
Published: December 2008

AbstractRelationship between isometric endurance performance at 50% of maximal voluntary isometric contraction (MVC) and skeletal muscle fibre composition has been elucidated in 19 physical education students. This was found to be linear and the equation corresponded to: y=9.35 + 1.093x; r= 0.70 (endurance time expressed in seconds and fibre composition as percent slow twitch muscle fibres (ST) of the vastus lateralis muscle). As it is assumed from previous studies that similar isometric tensions preferentially recruit fast twitch muscle fibres (FT) and that the muscle at the point of exhaustion exhibits maximal values for lactate accumulation, it is suggested that lactate formed in FT fibres is released and stored in nonrecruited ST fibres. The ability to sustain similar isometric tension would then be depending on how large the fraction of ST fibres is that can serve as a lactate recipient for lactate producing FT fibres.
Acid‐Base Changes and Excitation‐Contraction Coupling in Rabbit Myocardium. I. Effects on Isometric Tension Development at Different Contraction Frequencies
Authors: Jóhannsson M. , Nilsson E. 
Published: December 2008

AbstractThe effects of changes in acid‐base parameters on the active force of isolated rabbit papillary muscles were studied at contraction frequencies of 12, 60 and 120/min. When extracellular pH was lowered from 7.4 to 7.0 and 6.7 in a bathing solution buffered with 10 mM histidine, the active force decreased at all contraction frequencies studied. After parallel increases of HCO3concentration (up to 47 mM) and Pco2at a constant extracellular pH of 7.4 the active force of the muscle increased at low and decreased at high contraction frequencies. None of these effects can be attributed to catecholamine release or to altered extracellular concentration of ionized calcium. The inotropic effects produced by bicarbonate were not reproducible by methyl sulfate (47 mM) or propionate (47 mM). It is concluded that: 1. a lowering of the extracellular pH has a negative inotropic effect at all frequencies, 2. HCO3has a positive inotropic effect that is most pronounced at low contraction frequencies and 3. CO2has a negative inotropic effect exceeding that produced by the mere reduction in extracellular pH. The cellular mechanisms involved in the various inotropic effects are discussed.
Signal Characteristics of EMG with Special Reference to Reproducibility of Measurements
Authors: Viitasalo Jukka H. T. , Komi Paavo V. 
Published: December 2008

AbstractReliability and constancy of recordings of EMG signal characteristics were investigated from the measurements taken with minitature size surface electrodes during submaximal and maximal contraction of the rectus femoris muscle. The following EMG variables were studied: integrated EMG (IEMG) various band‐widths of the power spectral density function, mean power frequency (MPF), and rise time, amplitude and number of spikes of the averaged motor unit potential (AMUP). The results indicated that for most of the variables studied the reproducibility of measurements was better within the test session (reliability) than between the different test days (constancy). The reliability values for IEMG, MPF and AMUP amplitude were rather high (r = 0.77–0.92). MPF and number of spikes in AMUP showed good constancy values (r=0.73–0.93) and it is suggested that these parameters can be recommended for use in EMG studies where recordings are repeated over a period of several days.
Biogenic Amines in Carotid Body of Adult and Infant Rats —a Gas Chromatographic‐Mass Spectrometric Assay
Authors: Hellstrom Sten , Koslow Stephen H. 
Published: December 2008

AbstractA gas chromatographic‐mass spectrometric method was used for the determination of biogenic amines in carotid body of adult and 10 days old rats. The method is ideally suited for this measurement since only small amounts of tissue were available (dry weight carotid body: adult 8.3 μg;infant 5.6 μg). In adult carotid body large amounts of dopamine (1 950 pmol/mg protein) and norepinephrine (1 140 pmol/mg protein) were found together with a comparatively small concentration of serotonin (505 pmol/mg protein). The carotid bodies of infant rats contained 1 065 pmol dopamine/mg protein and 410 pmol norepinephrine/ mg protein. Epinephrine could not be detected. Surgical sympathetic denervation and chemical sympathectomy (6‐hydroxydopamine) of adult carotid bodies did not significantly change the catecholamine content as compared to the controls. Reserpine depleted the catecholamines dosedependently. Administration of L‐Dopa and pargyline (a monoamineoxidaseinhibitor) drastically increased the concentration of catecholamines. Treatment with a dopamine‐β‐hydroxylase‐inhibitor resulted in a decreased amount of norepinephrine without a simultaneous increase of dopamine. This may indicate that certain storage sites in this tissue may store dopamine while in other sites dopamine is a precursor of norepinephrine. Probably most of the dopamine and norepinephrine are stored in different cells.
Inefficiency of Isoprenaline to Induce Drinking in the Goat
Authors: Olsson Kerstin , Rundgren Mats 
Published: December 2008

AbstractIsoprenaline, which acts as a potent dipsogen in water‐satiated rats and dogs, did not elicit water intake when infused intravenously at 0.1 or 0.3μg/kgmin‐1in non‐hydrated goats. Even the low dose of the drug caused a marked reduction of parotid salivary flow. The possibility is discussed that reduced salivary secretion might be the particular effect which makes isoprenaline dipsogenic in prandially drinking species. The intravenous infusion of isoprenaline at the high dose level caused an inhibition of the water diuresis of hydrated goats, concomitant with reduced renal Na+excretion and a marked, sustained fall in the arterial blood pressure. Significant amounts of ADH were recovered from the urine secreted during the antidiuresis. This ADH‐release was apparently not due to central β‐adrenergic stimulation since no inhibition of the water diuresis was observed during intraventricular infusions of isoprenaline. Rather, the ADH‐release appears to have been secondary to the isoprenaline‐induced fall in arterial blood pressure.
Reduced Urinary Noradrenaline Excretion during Rest, Exercise and Cold Stress in Trained Rats: a Comparison between Physically‐Trained Rats, Cold‐Acclimated Rats and Warm‐Acclimated Rats
Authors: ÖStman Ingegerd , Sjöstrand Nils O. 
Published: December 2008

AbstractPhysically trained rats were compared with cold‐acclimated rats. Trained as well as cold‐acclimated rats showed cardiac and adrenal hypertrophy. Cardiac noradrenaline (NA) content was increased in both groups of rats but only the trained rats had an increased cardiac NA concentration. The adrenal NA content was increased in both groups but only the trained rats had an increased adrenal content of adrenaline (A). The spleen of trained rats had an increased NA content, while that of cold‐acclimated rats had a decreased NA content. The submandibular glands of cold‐acclimated rats were enlarged and had an increased NA content. Trained as well as cold‐acclimated rats had lower urinary NA excretions during rest, after exercise and during cold stress when compared with controls. However, only the trained rats had a reduced net increment in NA excretion after exercise, whereas there was no difference between the increments of cold‐acclimated and control rats. Six months after cessation of training, ex‐trained rats still had an increased heart ratio and a reduced urinary NA excretion after exercise. It is suggested that physical training induces “cross tolerance” to cold stress, while cold‐acclimation does not lead to “cross tolerance” to acute exercise.
Effects of Hypoxia of 10–45 Seconds Duration on Energy Metabolism in the Cerebral Cortex of Unanesthetized and Anesthetized Rats
Authors: Norberg Karin , Quistorff Björn , Siesjö Bo K. 
Published: December 2008

AbstractGlycolytic and citric acid cycle intermediates, as well as organic phosphates, were measured in the cerebral cortex of unanesthetized rats following arterial hypoxia (administration of 6–8 % 0,) of 10 and 20 s duration. There were decreases in glucose‐6‐phosphate and fructose‐6‐phosphate, and increases in fructose‐1,6‐diphosphate, dihydroxyacetone phosphate and 3‐phosphoglycerate, even before pyruvate accumulated. Since measurements of the lactate concentration showed that there was an increased glycolytic rate, the results demonstrate that phosphofructokinase was activated. The glycolytic changes were accompanied by, and probably due to, minor changes in phosphocreatine, ATP, ADP and AMP. Experiments of anesthetized animals showed that hypoxia for 45 s was accompanied by signs of phosphofructokinase activation, even if tissue Pco2 was kept constant. It is concluded that, irrespective of the tissue CO2 tension, hypoxia is accompanied by activation of phosphofructokinase which, at least initially, is responsible for the increased glycolytic rate.