bluuebunny/crossref_metadata_2025_split huggingface dataset:
Difference in Sensitivity of Parotid Glands brought about by Disuse and Overuse
Authors: Ekström Jörgen , Templeton David 
Published: December 2008

AbstractThe sensitivity to methacholine of the parotid glands in rats maintained on a liquid diet (aiming at sensitization) for a period of 2 weeks or 3–4 weeks was compared with that of the parotid glands in rats on a pelleted bulk diet (aiming at desensitization). In the rats on the liquid diet, it was found that the dose needed to evoke a just perceptible secretion of saliva was smaller, that the secretion started earlier and continued over a longer time period, and further that the amount of saliva secreted expressed per gland weight in response to submaximal doses of the sialogogue drug was bigger when compared with the rats on the pelleted bulk diet. These findings are interpreted as signs of a higher degree of sensitivity of the glands in the rats on the liquid diet than of those in the rats on the pelleted bulk diet.
Low Intensity Training, Inactivity and Resumed Training in Sedentary Men
Authors: ÖRlander Jan , Kiessling Karl‐Heinz , Karlsson Jan , Ekblom Björn 
Published: December 2008

AbstractThe effects of a low intensity training regimen, consisting of two 7‐week periods with an interspersed 8‐week inactivity period were investigated in 16 sedentary men. A follow‐up was made on 7 subjects after 38 additional weeks' training. Systemic as well as local effects were studied using exercise tests and leg muscle biopsies. The two 7‐week training periods both resulted in a 6% increase in Vo2 max and a lowered heart rate during submaximal work. No persisting training effects were detected by exercise tests after inactivity. In skeletal muscle, however, striking differences in enzyme activity pattern and ultrastructure were observed between the two periods, indicating that some training effect of importance for muscle metabolic adaptation might have persisted during inactivity. It is suggested that such an effect might be associated with the local oxygen supply. During the 38‐week training period there was a large increase in muscle metabolic capacity, but no change in maximal oxygen uptake. This separation of systemic and local training effects indicates a lack of a direct causal relationship between muscle metabolic potential and maximal oxygen uptake. It is suggested that the elevated muscle oxidative capacity is of importance for an increased endurance capacity.
Impulse Dependent Adaptation in Helix Pomatia Neurones: Effect of the Impulse on the Firing Pattern
Authors: Colding‐Jørgensen Morten 
Published: December 2008

AbstractIn neurones of the ventral ganglion of Helix pomatia an adaptation type is demonstrated, where the impulses contribute to the adaptation, as if a slowly changing outward current were associated to every impulse. The current appears to be accumulated from impulse to impulse and the accumulated current to decrease towards zero in the interval between the impulses. This type of adaptation is called impulse dependent. A method to distinguish between impulse dependent adaptation and impulse independent adaptation is described. Typical adaptation curves for the impulse dependent adaptation are shown. With a strong adaptation there is a linear relation between the steady state frequency and the applied stimulus. When stimuli of short duration are applied repetitively, neurones with impulse dependent adaptation respond with spikes on an increasing fraction of the stimuli as the stimulus strength is increased. A simplified model of the adaptation is proposed, and the firing pattern of the cells is compared with that of the model. In this way numerical values of the model parameters have been estimated.
Impulse Dependent Adaptation in Helix Pomatia Neurones: Demonstration of the Adaptation Conductance
Authors: Colding‐Jørgensen Morten 
Published: December 2008

AbstractBy conventional voltage clamp methods an increase in membrane conductance after a depolarizing pulse is demonstrated in neurones of Helix pomatia. This increase decays exponentially with a time constant in the range of 5–20 s. The rise of the conductance during the depolarization can be represented by 3 exponentials with time constants from 12 ms to 1 s. The steady state value of the conductance depends on the membrane potential in a sigmoid manner. The conductance gives rise to an outward current, which appears to be carried by potassium ions. The firing pattern of the cell is governed by the conductance. A short, rectangular potential change, a pulse clamp, is used to disturb the firing pattern of the freely firing cell. The effect on the firing pattern depends on the height and duration of the clamp pulse in the same manner as the conductance increase. The normal firing produces similar changes in the membrane conductance.
Angiotensin II: Intratubular and Renal Capillary Pressure Regulation in the Rat Kidney
Authors: Steven Kenneth , Thorpe Darrell H. 
Published: December 2008

AbstractExperiments were designed to test the hypothesis that angiotensin II, in its action on receptor sites in vascular smooth muscle and the proximal tubule, acts homeostatically to stabilize hydrostatic pressure in the proximal tubule, and as a consequence, maintains a constant flow of fluid to the distal tubule. Infusion, at 20 n1 min‐1, of Ileu5‐angiotensin II [(Ileu5)‐A II] (20 ng m1‐1) into peritubular capillaries adjacent to a proximal tubule was found to be accompanied by an increase in hydrostatic pressure in both the infused capillaries and the proximal tubule and by a decrease in the rate of proximal fluid reabsorption (RPFR). RPFR was derived from timed quantitative collections of tubular fluid from the last superficial proximal segments. Tubular pressure before infusion and pressures in noninfused capillaries were not related to plasma renin activity (PRA). 1‐Sarcosine, 8‐alanine‐angiotensin II [(Sar1, Ala8)‐A II] is known to be a competitive antagonist to the action of angiotensin II on vascular smooth muscle and on adrenocortical zona glomerulosa cells. Infusion, at 20 n1 min‐1, of (Sar1, Ala8)‐A II (333 ng m1‐1) into peritubular capillaries caused a decrease in hydrostatic pressure in the peritubular capillaries and adjacent proximal tubules. The most striking fall in pressure (‐4 cmH2O) occurred in rats with high levels of PRA. No pressure change resulted from infusion with a mixture of (Ileu5)‐A II and (Sar1, Ala8)‐A II. (Sar1, Ala8)‐A II in this mixture blocked the inhibitory effect of (Ileu5)‐A II on RPFR, but infusion of the angiotensin antagonist alone did not influence RPFR. It is concluded that angiotensin II is a physiological regulator of hydrostatic pressure in both the proximal tubule and the peritubular capillaries.
In Vivo Turnover Rate of Acetylcholine in Rat Brain Parts at Elevated Steady‐State Concentration of Plasma Choline
Authors: Eckernäs Sven‐Åke , Sahlström Lena , Aquilonius Sten‐Magnus 
Published: December 2008

AbstractCortical and striatal turnover rates of acetylcholine TRAchwere estimated by applying steady‐state tracer kinetics in rats killed by microwave irradiation following a constant i.v. infusion of3H‐Ch. In control rats TRAChwas 3.6 nmol · g‐1· min‐1in the cortex and 23.8 nmol · g‐1· min‐1in the striatum. When steady‐state plasma concentrations of Ch were increased from 17 to 140 μmol · 11by a 15‐min infusion of unlabeled Ch the corresponding TRAChwere 3.6 nmol · g‐1· min‐1and 21.4 nmol · g‐1· min‐1, respectively. These results indicate that increased plasma levels of Ch are not accompanied by increased synthesis of brain ACh.
Effect of the Preceding Day's Energy Intake on the Total Energy Cost of Light Exercise
Authors: Garby Lars , Lammert Ole 
Published: December 2008

AbstractThe effect of a variation in the preceding day's dietary energy intake‐4, 10 and 18 MJ‐on the oxygen consumption and respiratory quotient at rest and at work before and after a test meal (4 MJ) was investigated. 7 normal male subjects were studied at 3 different experimental situations. During the first day the subjects had an energy intake of 10 MJ and normal activity. The following morning measurements of V̇o2 and V̇co2 were performed at rest and at work on a bicycle ergometer (36 W) before and after the test meal. The same measurements were performed on the following day but the dietary intake between the two sets of measurement was then either 6, 0 or 14 MJ. No significant effect was found of the preceding day's dietary energy intake on the oxygen consumption or on the energy transformed during rest, during exercise before and after the test meal. The results do no support the conclusions of previously published studies, proposing a significant feed‐back mechanism tending to control the body energy content by regulation of the energy expenditure through chemical or mechanical uncoupling.
Capillary Pressure in Deep and Superficial Glomeruli of the Rat Kidney
Authors: Aukland K. , Tønder K. Heyeraas , Næss G. 
Published: December 2008

AbstractA new technique has been developed to make deep renal cortical structures in rats accessible for micro‐puncture: The left kidney is dissected free and immobilized in a lucite cup. A lense‐shaped slice, 1–2 mm thick and about 5×5 mm wide, is cut off from the dorsal aspect of the kidney. Blood oozing from the cut surface is removed by flushing with saline and suction by microsponges. The bleeding stops in 1–3 min and causes none or only transient fall in arterial pressure (PA). Up to 40 glomeruli become visible and remain circulated for several hours, as shown by injection of dye or silicone rubber. Glomerular capillary pressures (PG), measured with servocontrolled counter pressure (Wiederhielm), showed no consistent change with time and no correlation to PA. Average PG± S.E. in mmHg (number of glomeruli in parantheses) were: Wistar rats (WR), Inactin anesthesia, 57.8 ± 1.4 (41), Membumal anesthesia, 58.1 ± 1.3 (13). Sprague Dawley rats, Inactin, 58.1 ± 1.7 (14). In WR, PG was lower in deep than in midcortical glomeruli: ≤ 0.4 mm below kidney surface, 57.9 ± 1.8 (20); 0.5‐0.9 mm: 60.5+1.5 (20) and ≥ 1.0 mm: 53.8 ± 2.5 (13). Pressure in Bowman's capsule: 11.2 ± 0.6 (30). The observed PG is higher than previously reported on the Munich mutant strain of WR, and suggests that glomerular filtration equilibrium is not reached.
Catecholamines and Pancreatic Hormones during Autonomic Blockade in Exercising Man
Authors: Galbo H. , Christensen N. J. , Holst J. J. 
Published: December 2008

AbstractThe importance of autonomic nervous activity for the pancreatic hormonal response to exercise in man was studied. 7 men ran at 58% of V̇o2max (determined without administration of drugs) to exhaustion during a‐adrenergic blockade with phentolamine (P), during parasympathetic blockade with atropine (A), or without drugs (C). At rest phentolamine increased the plasma concentrations of both insulin and norepinephrine. During exercise norepinephrine concentrations increased and were in P experiments 3 times the concentrations in C experiments. Insulin always declined during exercise but in P experiments never decreased below basal levels. At identical times neither glucagon nor glucose differed significantly in the different expts. Thus during exercise α‐adrenergic blockade increased insulin concentrations but did not diminish the glucagon response. Nor was this response increased when β‐receptor stimulation in P experiments was intensified by the particularly high catecholamine concentrations. The concentrations of FFA, glycerol and lactate were highest in P experiments and identical in A and C experiments. These findings indicate that during prolonged moderate exercise in man insulin secretion is depressed by stimulation of α‐adrenergic receptors whereas glucagon secretion is not influenced by adrenergic receptors. Stimulation of β‐adrenergic receptors enhances lipolysis but neither lipolysis nor pancreatic hormonal secretion is influenced by cholinergic activity during exercise.
Transmembrane Potential Measurements as an Indicator of Heterogeneous Distribution of Nutritive Blood Flow in Skeletal Muscle during Shock
Authors: Haljämae Hengo , Jennische Eva , Medgeård Alf 
Published: December 2008

AbstractThe heterogeneity of nutritive skeletal muscle blood flow during shock was studied in terms of cellular transmembrane potential variations. Shock was induced in dogs by exteriorization of the small intestine for 3 h, whereafter the intestine was replaced and the dogs were studied for another 3–4 h. Transmembrane potentials of single skeletal muscle cells were recorded by the use of modified Ling‐Gerard microelectrodes. The mean resting transmembrane potential in control animals was ‐90.4 mV ± 0.7. The variation in transmembrane potential between adjacent fibers was small. During shock there was a significant decrease in the mean transmembrane potential and at the same time there was an increasing variation of up to 29 mV in the values between adjacent fibers. To exclude metabolic differences between red and white fibers as the main reason for this increasing heterogeneity of transmembrane potentials of adjacent fibers, complete tourniquet ischemia was also studied. The total tissue ischemia resulted in a marked reduction of the transmembrane potential in all cells with only small differences between adjacent fibers. After release of the tourniquet a marked spread of resting membrane potentials, with variations of 17–25 mV between adjacent fibers, occurred. This variation was similar to that observed during shock. It is concluded that repeated transmembrane potential registrations may reveal the variable state of adjacent cells subjected to a heterogeneous nutritive blood flow in shock.
Apnoea and Bradycardia from Submersion in “Chronically” Decerebrated Cats
Authors: Martner Jan , Wadenvik Hans , Lisander Björn 
Published: December 2008

AbstractIn “chronically” but not in acutely decerebrated cats, submersion of the head caused apnoea and marked bradycardia, associated with a maintained or slightly raised arterial pressure. Since these reflex adjustments, though very reproducible, occurred with a varying latency and could be induced also by nasal injection of water, they appeared to be, at least in part, elicited from the upper respiratory passages. Thus, a terrestrial mammal, reputed to shun any form of immersion, can exhibit adjustments during head submersion, similar to those in habitually diving species. This response pattern is basically organized at the lower brainstem level.
Role of the Adrenergic Nervous System in Development of Training‐Induced Bradycardia
Authors: Sigvardsson K. , Svanfeldt E. , Kilbom Å. 
Published: December 2008

AbstractSprague‐Dawley rats, normal and chemically sympathectomized with 6‐hydroxy‐dopamine, were trained by treadmill running. The normal rats, unlike the sympathectomized animals, showed reduction of the exercise heart rate after the training period. Compared to a sedentary control group the sympathectomized rats showed no difference in intrinsic heart rate after pithing and denervation and no increase in heart weight. The increase of the heart weight/body weight ratio after training was smaller in the sympathectomized group than in the normal one. The results show that a functioning adrenergic nervous system is necessary for an efficient adaptation to physical training. Administration of noradrenaline to pithed trained and untrained rats showed that betaadrenergic receptor sensitivity was not altered by physical training. The intrinsic heart rate of normal trained rats was lower than that of normal control rats.
Local Reflex in Microcirculation in Human Skeletal Muscle
Authors: Henriksen O. , Sejrsen P. 
Published: December 2008

AbstractThe effect of venous stasis of 40 mmHg upon blood flow in human skeletal muscle was studied in four normal subjects and in two chronically sympathectomized patients. Blood flow in skeletal muscle was measured by the local 133Xenon washout technique. Blood flow decreased about 30 per cent during venous stasis of 40 mmHg. In a “passive vascular bed” induced by means of histamine, blood flow decreased only by 16 per cent, indicating that the decrease in blood flow is due to a vasoconstrictor response to increase in vascular transmural pressure. The vasoconstrictor response was unaffected by a spinal sympathetic blockade, but was blocked in areas infiltrated with lidocaine or with phentolamine. The vasoconstrictor response was present in the nonoperated limbs used as a control, but abolished in the denervated arms in the two chronically sympathectomized patients. The findings strongly suggest that the vasoconstrictor response in skeletal muscle is due to a local nervous mechanism involving adrenergic fibres. Thus a local reflex mechanism, most likely a sympathetic axon reflex, seems to be present in human skeletal muscle as in cutaneous and subcutaneous tissue. This indicates that about 45 per cent of the change in total vascular conductance, when a person changes from supine to upright position, is due to this local reflex mechanism operating independently of the central nervous system.
Efflux of 5‐Hydroxytryptamine from Synaptosomes of Rat Cerebral Cortex
Authors: Ross Svante B. , Kelder Diana 
Published: December 2008

AbstractThe efflux of3H‐5‐HT from a crude synaptosome preparation of the cerebral cortex of reserpinized rats was examined. The synaptosomes were loaded with3H‐5‐HT by pre‐incubation of the homogenate in presence of pargyline and desipramine in order to inhibit deamination of 5‐HT and uptake into noradrenergic neurones. The synaptosomes were collected by centrifugation, washed and resuspended in 0.25 M sucrose. No spontaneous efflux of 5‐HT was detectable at 0°C but marked efflux was observed at 27°C and 37°C. 4‐Chloroamphetamine, low external Na+concentration, ouabain and the depolarizing agent veratridine markedly accelerated the initial (5 min) efflux. Inhibitors of the neuronal 5‐HT uptake,e.g.chlorimipramine, H 102/09 and A 23189, antagonized the 5‐HT efflux evoked by these means, whereas desipramine, which is a poor inhibitor of the 5‐HT uptake, had only slight effect on the 5‐HT efflux. It is suggested that 5‐HT can be actively transported out from the synaptosomes by the reversed 5‐HT uptake mechanism.
The Effect of Teeth Amputations on the Choline Aeetyltransferase Activity of Rat Submaxillary Glands
Authors: Ekström Jörgen 
Published: December 2008

AbstractThe choline aeetyltransferase activity in parasympathetically decentralized glands was unaffected by repeated teeth amputations over a period of 2 weeks, while after the same period of time the treatment caused the enzyme activity to increase in innervated glands. It appears that the enzyme in the postganglionic nerve is for its activity dependent on an intact connection with the central nervous system. The increase in enzyme activity is attributed to an enhanced reflex stimulation of the glands from pulpal receptors.
Carbonic Anhydrase in the Intestinal Tract of the Guinea‐pig
Authors: LöNNERHOLM GUDMAR 
Published: December 2008

AbstractThe distribution of carbonic anhydrase activity in the intestinal tract of the guinea‐pig was studied by the histochemical method of Hansson. Enzyme activity was demonstrated in epithelial cells, erythrocytes and capillary walls. In the gastric mucosa parietal cells, surface mucous cells and neck mucous cells were highly active. In the small intestine only a few epithelial cells on the villi and in the upper part of the crypts showed enzyme activity. They seemed to be randomly scattered among inactive ones. It is not clear at present if they represent a distinct cell type or specialized absorptive cells. In the proximal colon most surface epithelial cells were highly active (goblet cells were inactive), whereas the surface cells in the distal colon showed less activity with a more varying degree of staining. In the cecum enzyme activity was found in the surface epithelium and in the upper part of the crypts, the staining being most marked at the luminal border of the surface cells. The staining reaction was completely inhibited in all tissues by 10 μM acetazolamide, except for the luminal staining of the cecum, which was inhibited only by 100 μM acetazolamide. This indicates the presence of high concentrations of carbonic anhydrase, probably of the “low activity” form, at this locus. Mucosal scrapings were taken from the intestinal tissues, homogenized and assayed for carbonic anhydrase activity by a changing‐pH indicator method. The results confirm those of previous studies and correlate well with the histochemical findings.
Potentiation by Carbachol and Aminophylline of Histamine‐ and db‐cAMP‐Induced Parietal Cell Activity in Isolated Gastric Glands
Authors: Berglindh Thomas 
Published: December 2008

AbstractThe response to combinations of gastric acid secretagogues was studied in isolated glands from the rabbit gastric mucosa in terms of changes in oxygen consumption and accumulation of the weak base aminopyrine (AP). The latter reflects the acid secreting status of the glands. The following secretagogues were investigated: histamine, carbachol, aminophylline and db‐cAMP. The histamine respiratory dose‐response curve was shifted to the left in the presence of the phosphodiesterase inhibitor aminophylline. Both ED‐50 and maximum response were significantly increased. Histamine‐induced AP accumulation was also strongly enhanced by aminophylline (5 × 10‐4 M). These results are consistent with the hypothesis that histamine stimulation of acid secretion is mediated by cyclic AMP. Carbachol‐stimulated oxygen consumption could not be potentiated by aminophylline and the combined effect was only additive. The response to a combination of histamine and carbachol was a significant increase in oxygen consumption above what could be expected from an additive effect alone. Carbachol addition to glands prestimulated with histamine gave a rapid increase in the respiratory rate resulting in a new steady state level within 10–15 min, as compared with a time constant of about 40 min when both drugs were added simultaneously. Likewise AP accumulation increased more rapidly and reached a higher value after addition of histamine + carbachol as compared with histamine alone. The db‐cAMP‐stimulated oxygen consumption was in all respects equally affected by carbachol as was histamine stimulation. This indicates that the well known cholinergic potentiation of histamine stimulation is not due to an increased sensitivity of the histamine receptor but is of a more general nature. A mechanism involving intracellular availability of Ca2+ is proposed as one possible explanation of this potentiation.
The Effect of Plasma Proteins on the Capillary Permeability in the rete mirabile of the Eel (Anguilla vulgaris L.)
Authors: Myhre Kjell , Steen Johan B. 
Published: December 2008

AbstractMeasurements of transcapillary exchange of high‐molecular dextrans, K+ and THO in the rete mirabile of the eel (Anguilla vulgaris L.) have been made under steady‐state conditions while varying the amounts of plasma proteins in the perfusates. When the perfusates contained 20% or less horse serum the permeabilities of D‐75 000. K. and THO increased significantly. The effect on the K+ permeability was irreversible while that on D‐75 000 and THO was not. The permeability was unaffected when the perfusate contained 30% serum or more. Adding 1.3g/100 ml bovine albumin to the perfusate maintained the D‐75 000 and THO permeabilities unchanged while that of K˜ appeared to increase. At an albumin content of 0.33 g/100 ml the effect was similar to that produced by low serum perfusates. Our main conclusion is that lack of the albumin fraction of the plasma proteins reversibly increases the intercellular pore area and irreversibly changes the K permeability of the cell membrane.