bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties of a conductive cellular chloride pathway in the skin of the toad (Bufo bufo)
Authors: Larsen Erik Hviid , Kristensen Poul 
Published: December 2008

AbstractTwo types of chloride current response to a step‐wise hyperpolarization of the toad skin is demonstrated: (1) An “instantaneous” response observed immediately upon voltage change, and (2) a subsequent slow response, the time course of which is sigmoidal. The slow response is due to an increase of a transcellular conductance which is specific to chloride ions. The time constant of the conductance increase is dependent on the amplitude of the transepithelial voltage displacement, the smallest time constants are obtained for the highest amplitudes and are in the order of 30 s. The voltage dependences of the steady‐state conductance and the steady‐state chloride current reveal that the chloride pathway has maximum conductance for V≅‐80 mV (outside of the skin being negative) and approaches a non‐conducting state for V > 0 mV. This strong outward going rectification is a steady‐state phenomenon: In skins hyperpolarized for a few minutes, the “instantaneous” I‐V curves show that the chloride pathway in the conducting state allows a large inward chloride current (outward chloride flux) to pass in the voltage range 40 mV > V > 0 mV. Calculations based on a three‐compartment model indicate that the strong steady‐state chloride current rectification cannot be obtained if only the intracellular chloride concentration and the membrane potentials are allowed to vary (“Goldman‐rectification”). It is suggested, therefore, that the permeability of the chloride pathway varies reversibly with the transepithelial potential difference. The variable which controls the chloride permeability may be a membrane potential or the concentration of an intracellular ion.
On the neuromuscular effects of pindolol and sotalol in the rat
Authors: Larsen Andreo 
Published: December 2008

AbstractThe effects of pindolol and sotalol on neuromuscular transmission were tested using intracellular micro‐electrode recording of resting membrane potentials, miniature end‐plate potentials and end‐plate potentials, and recording of muscle contractions upon nerve stimulation of rat phrenic nerve‐hemidiaphragm preparations. Both pindolol and sotalol reduced the amplitudes of miniature end‐plate potentials and end‐plate potentials in a dose‐dependent manner without significantly affecting their time‐courses. Pindolol, but not sotalol, also increased the frequency of the miniature end‐plate potentials and decreased the number of acetylcholine quanta released by nerve impulses. Neither of the drugs significantly affected resting membrane potentials of the muscle fibres or excitability of the motor nerve to electric stimulation.
Cardiovascular reactivity and design in rats with experimental “neurogenic hypertension”
Authors: Jones John Vann , Hallbäck Margareta 
Published: December 2008

AbstractThe arterial baroreceptors were denervated in 20 normotensive Wistar rats. 2 1/2 months after the operation their cardiovascular responses to “mental stress” were compared to those of matched control rats (NCR). At the time of investigation the blood pressure of the baroreceptor denervated rats (BDR) was increased some 15 per cent above that of the control group. There was, however, no difference in response to “mental stress” between groups, if anything the BDR responded with less pronounced tachycardia. Two months subsequent to the stress‐test the mean blood pressure of the BDR was still significantly above normal levels, but the BDR did not exhibit structural cardiovascular adaptation, which has been documented in most types of stable hypertension as a response to the increased mean blood pressure. The results imply that hypertension induced by baroreceptor denervation is not of a stable and persistent type in which case structural changes in the cardiovascular system would have developed within the observation period (approximately 4 months). Emotional stimuli, however, do not seem to contribute to periodic blood pressure increases at the time of measurement, as earlier suggested.
Ultrastructure of synaptosomes from fetal rat brain
Authors: Kanerva Lasse , Hervonen Antti , Tissari Anja H. 
Published: December 2008

AbstractThe crude mitochondrial fraction P2 and subfractions of P2 were prepared from the brain stem, hemispheres and whole brain of 19‐day‐old fetal rats. Samples were fixed in glutaraldehyde‐osmium, NaMnO4 or by Tranzer's triple fixation method (aldehyde‐chromate‐dichromate‐osmium) and examined by electron microscopy. The C‐fraction from whole brain was the main synaptosome fraction, containing 3.2 % presynaptic terminals as counted from all membrane bound particles. The brain stem showed more presynaptic terminals than the hemisphere (2.8% versus 0.9%) suggesting a caudal‐rostral maturation gradient for synaptogenesis. The maturity of the nerve endings obtained was very variable in contrast to the rather uniform synaptosomes derived from adult tissue. They varied from profiles without any substructures to mature synaptosomes displaying asymmetric synaptic junctions. Monoamine synaptosomes containing small granular vesicles were not detected in the present study, suggesting immaturity of the granular monoamine pool at this stage of development.
Effect of chronic hypoxia on hepatic triacylglycerol concentration and mitochondrial fatty acid oxidizing capacity in liver and heart
Authors: Kinnula Vuokko L. , Hassinen Ilmo 
Published: December 2008

AbstractThe effect of moderate hypoxia (50.5 kPa air) and severe hypoxia (40.8 kPa air) in vivo on liver and heart triglyceride concentration and mitochondrial respiration rates was studied. Liver triglyceride concentrations increased in severe hypoxia from 7.3 μmol/g wet weight to 23.3 μmol/g wet weight over 7 days. After the period of seven days in severe hypoxia, the palmitate, octanoate and palmitoylcarnitine oxidation rates of mitochondrial suspensions were significantly reduced when the citric acid cycle was operative. No decrease in the fatty acid, fatty acyl‐CoA or carnitine derivative oxidation was observed when only the β oxidation system was studied. Mitochondria isolated from the heart or liver after seven days in severe hypoxia showed reduced respiratory control ratios, the decrease being from the normal 4.9 to 1.9 in the liver mitochondria using succinate as substrate. The reduction in respiratory control was mainly due to lowered State 3 respiration rates. Some reduction in the ratio was also observed in the fasting controls, from 5.8 to 3.4 with succinate. The respiratory control ratio could be partially normalized by the addition of albumin to the isolation medium for the liver mitochondria after severe hypoxia. Under these conditions, however, the State 4 respiration of the mitochondria from the hypoxic animals was higher than that for the controls.
Efflux of phenylalanine and tryptophan from cerebral cortex slices of adult and 7‐day‐old rats
Authors: Laakso M.‐L. 
Published: December 2008

AbstractAn equation of two exponential terms was found to adequately describe the efflux of phenylalanine and tryptophan from cerebral cortex slices of adult and 7‐day‐old rats. These exponential terms described two forms (components) of efflux taking place at different rates. The fast component of efflux was more prominent in the slices from young rats than in those from adults. In both age groups the contribution of the fast component increased with an increasing amino acid concentration in the superfusate, but there were no changes in the rate constants. The rate constants of the fast components were equal in all experimental conditions in both age groups. The rate constants for the slow components of both amino acids were lower in the slices from adult rats than in those from young rats. The reason for efflux occurring at two different rates is discussed. The fast component probably consisted of the amino acid originating from the extracellular space of the slices and of the intracellular amino acid released by exchange. The slow component consisted of the amino acid released from the cells by other mechanisms, e.g. by diffusion through the membranes or by some active efflux processes. The cerebral cortex slices from adult rats have greater ability to concentrate aromatic amino acids than the slices from young rats. This may partly be dependent on the more effective influx and partly on the slower efflux of amino acids in the slices from adults.
The function of baroreceptor C fibres in the rabbit's aortic nerve
Authors: Aars Harald , Myhre Lisbeth , Haswell Bruce A. 
Published: December 2008

AbstractThe participation of aortic nerve C fibres in the baroreflex was investigated by recording changes in renal nerve activity in response to acute increases in arterial pressure, in two experimental situations: with the A and C fibres of the left aortic nerve intact, and with the A fibres temporarily blocked by a hyperpolarizing current (anodal block). Pressure was increased by manual inflation of an intra‐aortic balloon, and interference from other baroreceptor areas was avoided by carotid occlusion and sectioning of the right aortic nerve. Rises in mean arterial pressure exceeding 20 mmHg, to levels above 110 mmHg, were needed to trigger sympathetic inhibition via C fibres. A rise of 45 mmHg caused 50% reduction in sympathetic activity, equal to that obtained by stimulation of aortic nerve C fibres at about 3 Hz. In contrast, a rise of 20–30 mmHg evoked more than 60% reduction in sympathetic activity when the A fibres were operative. Judged by these studies of peak reflex responses to brief pressure rises, baroreceptors with C fibres in the aortic nerve have a much higher threshold to pressure than their myelinated counterparts; the C fibres contribute to the baroreflex inhibition of sympathetic discharge only when pressure is increased well above normal resting levels.Preliminary presentations of this paper were given in June 1976 at the 7th European Congress of Cardiology, Amsterdam, The Netherlands, and at the 8th Nordic Hypertension Meeting, Marstrand, Sweden (Aars, Myhre and Haswell 1976).
Tissue osmolality in intestinal villi during luminal perfusion with isotonic electrolyte solutions
Authors: Jodal Mats , Hallbäck Dan‐Axel , Lundgren Ove 
Published: December 2008

AbstractA cryoscopic technique has been developed that makes it possible to determine tissue osmolality in the core of the intestinal villi. During absorption from an isotonic electrolyte solution containing glucose an osmolality gradient was demonstrated from tip to base of the villi in both the jejunum and the ileum. The tissue osmolality at the villous tips was measured to 1 000–1 200 mOsm/kg H2O while the osmolality at the villous bases was approximately isotonic with plasma. Increasing intestinal blood flow by i.a. administration of a vasodilator drug, or making the intestine ischemic by clamping the intestinal vascular supply while supplying the mucosa with oxygen, markedly decreased tissue osmolality. Substituting all sodium ions with choline in the luminal perfusate abolished almost completely the tissue hyperosmolality and the intestine became a secretory organ. These observations are consistent with the view that the observed villous tissue hyperosmolality was created by a countercurrent multiplication of sodium chloride. The physiological implications of this mechanism is discussed and it is, among other things, proposed that the hyperosmolar region represents the hyperosmotic compartment necessary for explaining intestinal water absorption.
An “on‐line” colorimetric method for repeated, rapid determinations of capillary diffusion capacity
Authors: Rippe Bengt , Stage Lars 
Published: December 2008

AbstractThe single injection indicator diffusion method for estimation of capillary diffusion capacity (Crone 1963) has been developed to provide directly visualized, continuous colorimetric recordings of the venous time‐concentration curves by means of a two‐colour densitometer system. Cardio‐Green, bound to albumin, is used as the non‐permeant (“reference”) tracer and Cr‐EDTA as the permeant one. The artificially perfused hindquarter muscle vascular bed of rats is used. Highly reproducible curve recordings can be obtained every fourth minute. Accidental disturbances of the recordings are readily detected. Thus, compared to the fractional venous sampling technique, the present technique has the great advantage of allowing immediately controlled and frequently repeated determinations of capillary diffusion capacity. It is therefore easily used together with measurements of filtration‐absorption events, e.g. for frequent quantitative comparisons of capillary diffusion and filtration capacities over a wide range of induced changes in perfused capillary surface area and/or capillary permeability. The main limitation is that the employed permeant tracer necessitates the use of erythrocyte‐free perfusates.
Short‐latency ventilatory responses to sudden withdrawal of hypoxia at normal and raised body temperature in man
Authors: Jensen J. Ingemann , Vejby‐Christensen H. , Petersen E. Strange 
Published: December 2008

AbstractApproximately isopnoeic conditions (VE=40 1/min) were achieved by the inhalation of asphyxial gas mixtures (PA1O2 60 torr, PA1CO2 40–45 torr) in normothermia and after a rise in rectal temperature of 1.6°C had been induced by a heated flying suit. Arterial chemoreceptor drive was transiently reduced by either isocapnic removal of hypoxia (type (1) tests: two breaths of CO2 in O2) or simultaneous withdrawal of both hypercapnia and hypoxia (type (2) tests: two breaths of O2). 8–13 tests of each type were performed at both temperature conditions in 6 expts. on 4 healthy human subjects. Expired volume, total breath duration and inspiralory time were recorded, and minute ventilation and expiratory time subsequently computed breath by breath. In hyperthermia the steady‐state ventilation of 40 1/min (at a relatively higher respiratory frequency and a correspondingly lower tidal volume) was achieved at a PA1CO2 which was 5 torr lower than in normothermia. Ventilation decreased significantly in all tests. Tested with a 3‐way analysis of variance significant differences between the ventilatory responses at the two temperature conditions, and between the two test types were found. The rate of change of ventilation was greater in hyperthermia than in normothermia, and also greater in type (2) tests than in type (1) tests. Since isopnoeic conditions existed prior to the tests, this implies that the arterial chemoreceptor contribution to the total ventilatory drive is increased in hyperthermia. In type (2) tests a significant lengthening of expiratory time was observed in the first test breath. This finding confirms the effect in man of changes in airway PCO2 on lung stretch receptor discharge.
The mechanism of histamine release induced by the ionophore X537A from isolated rat mast cells: 1. Significance of Monovalent Cations, Calcium, Metabolic Energy and Temperature
Authors: Kazimierczak W. , S. A. Patkar  , Diamant B. 
Published: December 2008

AbstractHistamine release induced by X537A from isolated rat mast cells was dependent on the presence of sodium or potassium but not on calcium in the incubation medium. The rate of release was faster in potassium than in sodium, but the final release was the same after prolonged incubation. Extracellular calcium as well as metabolic inhibitors depressed the rate of release induced by X537A. Pretreatment of mast cells with either EDTA or the ionophore A23187 in the absence of extracellular calcium did not influence subsequent release induced by X537A. The findings of release at 45°C and lack of release at 0°C distinguish the mechanism of action of X537A from calcium‐and energy‐dependent releasing agents like compound 48/80 and A23187 on the one hand and the simple lytic action of decylamine on the other.
Insulin‐stimulated bile formation in cats
Authors: Jens Anker Larsen  , Christensen Kent Dencker 
Published: December 2008

AbstractThe effects of insulin on bile flow and composition were examined in fasting, chloralose‐anesthetized cats. Insulin in doses from 0.01 to 2.00 U/kg increased bile flow and biliary erythritol clearance without any detectable change in the difference between them; thus insulin presumably had no effect on ductular fluid transport. Continuous infusion of insulin (0.8 U/kg + 0.05 U/kg/min or 0.05 Uykg + 0.002 U/kg/min) increased biliary erythritol clearance by 22%. The increase was caused by a rise in the bile acid‐independent fraction of bile production and accompanied by a parallel increase in the rates of biliary excretion of Na+and Cl‐. When ouabain, 80 μg/kg, was injected intraportally during insulin infusion the erythritol clearance, bile flow and the rates of biliary excretion of Na+ and Cl‐ were lowered towards but not to their pre‐ insulin levels. The effects of insulin on these parameters were unchanged after atropin or gastrectomy and 2‐Deoxy‐D‐Glucose was without effect on bile production. The results indicate that administration of insulin affects bile formation by stimulating the active transport of sodium across the canalicular membrane.
Circulatory and metabolic effects in the brain induced by amphetamine sulphate
Authors: Berntman Leif , Carlsson Christer , Magnus Hägerdal  , Siesjö Bo K. 
Published: December 2008

AbstractCerebral circulatory and metabolic effects of amphetamine sulphate (0.25–25 mg·kg‐1i.v. or 5–10 mg·kg‐1i.p.) were studied in anesthetized, paralyzed and artificially ventilated rats. Cerebral blood flow (CBF) was measured with a modification of the Kety and Schmidt (1948) technique, and oxygen consumption (CMRo2) was calculated from CBF and arteriovenous differences in oxygen content. Regional CBF was evaluated from the uptake of 14C‐ethanol. Cortical metabolites were analysed following freezing of tissue in situ. Amphetamine administration gave rise to a marked increase in CBF that was doubled following 0.25 mg·kg‐1 and increased 4‐fold following 15 mg·kg‐1. However, such excessive increases in flow were confined to frontoparietal cortical regions, while other cortical or subcortical areas showed more moderate hyperemia. The increase in CBF was unrelated to changes in arterial Pco2, blood pressure, or tissue lactate content. CMRo2 increased by 30% to 95% depending on dose and rat strain used. At all doses employed, amphetamine gave rise to glycogenolysis in cerebral cortex but, in animals studied within the first 30 min after 5 mg‐kg‐1, or less, the only other changes were increases in glucose‐6‐phosphate and α‐ketoglutarate concentrations. When the dose was increased to 15 mg·kg‐1, there were moderate increases in lactate concentration and lactate/pyruvate ratio. Sixty min after 5 mg·kg‐1 there were increases in tissue concentrations of pyruvate, citric acid cycle intermediates and alanine, as well.
Urinary cyclic AMP and vasopressin excretion in rat strains selected for their alcohol intake
Authors: Jaakko Linkola  , Fyhrquist Frej 
Published: December 2008

AbstractUrinary excretion of adenosine 3′,5′‐cyclic monophosphate (cAMP) and immunoreactive arginine vasopressin (AVP) were investigated after water loading and following ethanol loading in two rat strains selected for their voluntary ethanol intake. After ethanol loading ethanol preferring (AA) rats excreted more cAMP but less AVP than water preferring (ANA) rats. The results suggest that the strain difference in cAMP excretion is of renal origin and is not due to vasopressin or parathormone. Differences in the sympathetic nervous activity may be responsible for the difference in cAMP excretion.
Polyamines and nucleic acids in the mouse kidney induced to growth by testosterone propionate
Authors: Henningsson Stig , Persson Lo , Rosengren Elsa 
Published: December 2008

AbstractDaily injections of testosterone propionate to castrated mice resulted in a striking increase in kidney weight. Renal putrescine rose sharply and the amounts of spermidine and spermine were also increased. The activity of ornithine decarboxylase was enhanced to values of more than 1 000 times the control level within a few days of testosterone substitution. A moderate and temporary increase in the activity of the putrescine‐activated S‐adenosyl‐L‐methionine decarboxylase was observed. Testosterone injections produced a large increase of renal RNA but only a minor change in DNA. It is apparent that in mice distinct alterations in polyamine metabolism occur during the development of renal hypertrophy induced by testosterone administration.
Time course of light induced changes in pilocarpine sensitivity of rat iris
Authors: Claesson Heléan , Báaráany Ernst 
Published: December 2008

AbstractPigmented rats were kept under different light regimens for 1–20 days. Supramaximal light was used. The response of the iris sphincter in enucleated eyes with their cornea intact was tested in vitro. Pilocarpine at 6 × 10‐5M was used as a standard stimulus. In agreement with previous authors there was a marked difference between constant light treated (subsensitive) eyes and dark treated (supersensitive) ones. Animals pretreated to reach maximal sub‐ and supersensitivity and then shifted to the opposite regimen, showed that reversal was a gradual process starting within a few hours. Full reversal had not been reached at 72 h. The two curves of sensitivity vs time intersected around 24 h. The time constants of the two curves were approximately equal. Light regimens using intermittent light shifting every 1, 3, 6 or 12 h gave intermediate results.
Inhibition of vasopressin‐release during developing hypernatremia and plasma hyperosmolality: An effect of intracerebroventricular glycerol
Authors: Olsson K. , Fyhrquist F. , Larsson B. , Eriksson L. 
Published: December 2008

AbstractIn non‐hydrated goats prolonged (3 h, 0.02 ml/min) intracerebroventricular (IVT) infusion of 0.35 M glycerol depressed the plasma vasopressin level during the entire infusion period which resulted in a conspicuous water diuresis outlasting the infusion by about 20 min. Since no compensatory drinking occurred during this sustained water diuresis it gradually induced pronounced dehydration (loss of > 1 liter of total body water causing 5% increase in plasma [Na+] and osmolality). The same degree of dehydration was in other experiments induced by water deprivation. It then caused a 5‐fold increase in plasma vasopressin level.Corresponding IVT infusions of 0.35 M d‐glucose depressed plasma vasopressin level only during the first half of the 3 h infusion period. Consequently, the resulting water diuresis was transient and subsided before the glucose infusion was finished.Plasma renin activity increased during the IVT glycerol infusion and during water deprivation, but was largely unaffected by IVT glucose. Both IVT glycerol and glucose decreased renal sodium excretion.The possibility is discussed that the pronounced ability of IVT glycerol to depress the vasopressin release and thirst is not only due to dilution induced reduction of CSF [Na+], but also to an influence of glycerol on choroidal and/or transependymal Na+‐transporting mechanisms.