bluuebunny/crossref_metadata_2025_split huggingface dataset:
Peripheral nerve activity in response to heating the cat's skin
Authors: Stolwijk Jan A. J. , Wexler Ira 
Published: December 2014

1. The sensitivity of the cat hind‐limb skin to non‐noxious heating was studied. Neural activity was recorded with micro‐electrodes from intact multifibre fascicles of the saphenous nerve while the skin was actively heated or passively cooled.2. Moderate warming from indifferent temperatures of 30–34° C to temperatures of 38–39° C produced a reduction in the total rate of firing of the integrated discharge. Firing picked up sharply again at skin temperatures above 39° C. A considerable fraction of the impulse activity elicited above 39° C was carried by C‐fibre afferents.3. Prolonged heating to temperatures in excess of 45° C rendered the skin insensitive to further non‐noxious heating or to touch.4. The neural response to a step increase in skin temperature consisted of a delayed overshoot and then a steady‐state level of firing. Steady‐state firing was proportional to the level of skin temperature.5. Nerves whose C‐fibre input to the spinal cord had been selectively blocked showed a potentiation of the neural response to skin heating.6. The sensitivity of hind‐limb skin to heating, as judged by the character of the multifibre discharge, appears similar to that reported for a highly warm‐sensitive region of the nose.
Analysis of the effluxes of sodium, potassium and chloride ions from smooth muscle in normal and hypertonic solutions
Authors: Brading Alison F. 
Published: December 2014

1. Efflux curves of 24Na, 42K and 36Cl from the guinea‐pig taenia coli were obtained in normal Krebs solution, and in hypertonic Krebs solution in which the osmolarity had been doubled by the addition of sucrose.2. The efflux curves were complex, and in order to get average curves each was analysed as the sum of three exponential terms, and average curves were constructed from the means of the constants found.3. In order to estimate the membrane permeability to the ions, it was necessary to make assumptions as to the distribution of ions in the tissue. Several models have been examined and the predictions of the models with respect to the membrane properties were compared with the data obtained by using electrophysiological methods by other workers.4. It was found that reasonable predictions of membrane properties could only be made using models in which the majority of the rapidly exchanging sodium is considered to be extracellular. This amount of sodium is more than can be accounted for as freely dissolved in the extracellular water.5. A possible interpretation of the ion exchange and distribution would be to suppose that some proportion of the three ions is contained in an extracellular compartment not available to the normal extracellular markers, and limited in its exchange by the rate of diffusion in the extracellular phase, and that the truly intracellular fractions of the tissue ions do not exchange with the external solution in a simple exponential manner, but in a manner described by an aggregate of exponential terms due to inherent variation in the permeabilities of the individual cell membranes.6. There is no evidence for any change in the membrane permeabilities to sodium and potassium in hypertonic solution, but there is evidence for a decrease in chloride permeability in this solution.
Heat production in the gastro‐intestinal tract of the dog
Authors: Durotoye A. O. , Grayson J. 
Published: December 2014

1. Mean temperature from the lumen of the dog duodenum was 0·6° C hotter than aorta. Ileum, stomach and large intestine were slightly cooler but still about 0·5° C hotter than aorta.2. Portal vein averaged 0·35° C hotter than the aorta.3. From portal blood flow data and aortic—portal temperature differentials heat production was calculated for the 10 kg dog as 3·4 kcal/hr.Evidence is adduced to show in these experiments that the gastro‐intestinal tract produced 60% more heat than the liver.Total splanchnic heat production was about 33% of the total bodily heat production.4. The following procedures were carried out: adrenergic neurone blockade, atropine administration, vagotomy, prior starvation, bowel sterilization. All were without effect. It was concluded that smooth muscle activity, active transport or microbiological activity were unlikely to be sufficient to account for the high level of heat production.5. It was suggested that mucosal activity was the most likely source of heat. The possible involvement of unidentified metabolic pathways was discussed but oxidative mechanisms alone were shown not to be sufficient explanation.6. Since the rectal temperature was not significantly different from aortic it was concluded that the rectum was metabolically inactive and usually passively assumed the temperature of its blood supply.
The influence of the chloride gradient across red cell membranes on sodium and potassium movements
Authors: Cotterrell D. , Whittam R. 
Published: December 2014

1. A study has been made to see whether active and passive movements of sodium and potassium in human red blood cells are influenced by changing the chloride gradient and hence the potential difference across the cell membrane.2. Chloride distribution was measured between red cells and isotonic solutions with a range of concentrations of chloride and non‐penetrating anions (EDTA, citrate, gluconate). The cell chloride concentration was greater than that outside with low external chloride, suggesting that the sign of the membrane potential was reversed. The chloride ratio (internal/external) was approximately equal to the inverse of the hydrogen ion ratio at normal and low external chloride, and inversely proportional to external pH. These results show that chloride is passively distributed, making it valid to calculate the membrane potential from the chloride ratio.3. Ouabain‐sensitive (pump) potassium influx and sodium efflux were decreased by not more than 20 and 40% respectively on reversing the chloride gradient, corresponding to a change in membrane potential from −9 to +30 mV. In contrast, passive (ouabain‐insensitive) movements were reversibly altered — potassium influx was decreased about 60% and potassium efflux was increased some tenfold. Sodium influx was unaffected by the nature of the anion and depended only on the external sodium concentration, whereas ouabain‐insensitive sodium efflux was increased about threefold. When external sodium was replaced by potassium there was a decrease in ouabain‐insensitive sodium efflux with normal chloride, but an increase in low‐chloride medium.4. Net movements of sodium and potassium were roughly in accord with the unidirectional fluxes.5. The results suggest that reversing the chloride gradient and, therefore, the sign of the membrane potential, had little effect on the sodium pump, but caused a marked increase in passive outward movements of both sodium and potassium ions.
The synthesis, turnover and release of surplus acetylcholine in a sympathetic ganglion
Authors: Collier B. , Katz H. S. 
Published: December 2014

1. Surplus acetylcholine (ACh) is the extra ACh that accumulates in cholinergic nerve endings when they are exposed to an anticholinesterase agent. The synthesis and turnover of this ACh was examined in the cat's superior cervical ganglion.2. Surplus ACh did not accumulate in chronically decentralized ganglia perfused with eserine‐choline‐Locke solution, and this shows that it is stored in presynaptic nerve terminals.3. Surplus ACh accumulated more rapidly in ganglia perfused with eserine than in ganglia perfused with neostigmine or with ambenonium; accumulation was delayed by 45–60 min when a quaternary anticholinesterase was used. However, the release of ACh upon preganglionic nerve stimulation was the same during perfusion with eserine, neostigmine or ambenonium. It is concluded that intracellular acetylcholinesterase normally destroys surplus ACh, whereas extracellular enzyme destroys released ACh.4. When ganglia were perfused with [3H]choline and eserine, the surplus ACh that accumulated was labelled but its specific radioactivity was only 38% of that of the choline added to the perfusion fluid.5. Surplus ACh was not released by nerve stimulation and was not mobilized for release during, or after, prolonged nerve stimulation. It is concluded that ACh released by nerve impulses is replaced by synthesis at the site of ACh storage and not by movement of ACh from the surplus pool.6. The accumulation of surplus ACh no more than doubled the total ACh content of ganglia, but turnover of ACh continued when the total amount was constant. Surplus ACh may contribute to spontaneous ACh output from eserinized preparations.7. When ganglia were perfused with a medium containing high K+ (56 m
M), surplus ACh was released.
The transfer of free α‐amino nitrogen across the placental membrane in the guinea‐pig
Authors: Reynolds Margaret L. , Young Maureen 
Published: December 2014

1. Transfer of endogenous α‐amino nitrogen from the maternal to foetal side of the placental membrane was studied in the foetal guinea‐pig placenta perfused, in situ via the umbilical vessels, with an artificial fluid. Changes in maternal placental blood flow were followed by measuring the transfer of antipyrine into the perfusate.2. Active transport by the membrane was demonstrated under these conditions by observing the increased ratio of
L/D leucine appearing in the perfusate in comparison with the maternal plasma ratio.3. Reduction in maternal placental flow following haemorrhage was associated with a fall in transfer of amino nitrogen to about half of the control values.4. The concentration of α‐amino nitrogen in the perfusate was inversely proportional to the foetal placental flow which had a smaller influence on amino nitrogen transfer per min than did the maternal blood flow.5. Hypoxia and some inhibitors of oxidative metabolism were without influence on the transfer of α‐amino nitrogen in this preparation.
Effect of injury on shivering thermogenesis in the rat
Authors: Stoner H. B. 
Published: December 2014

1. Shivering in response to changes in ambient or core temperature has been measured in control rats and rats injured by bilateral hind‐limb ischaemia, both with and without fur.2. Removal of the fur increased the threshold ambient temperature for the onset of shivering.3. This threshold was lower than in uninjured controls during the latter half of a 4 hr period of bilateral hind‐limb ischaemia in rats with or without fur.4. The threshold was also lower than in uninjured controls after the period of bilateral hind‐limb ischaemia but was not significantly different from that during the period of ischaemia.5. The alterations in threshold were not accompanied by any significant changes in the slope of the regression line relating intensity of shivering and ambient temperature.6. When the core temperature fell after limb ischaemia to levels which provoked shivering in uninjured controls, no shivering was seen in the injured rats.7. These results are interpreted as further evidence for the lowering of the ‘set‐point’ for thermogenesis after injury in the rat and are discussed in relation to the changes in body temperature after injury in that species.
The effects of electrical stimulation of the distal end of the cut sinus and aortic nerves on peripheral arterial chemoreceptor activity in the cat
Authors: Neil E. , O'Regan R. G. 
Published: December 2014

1. In anaesthetized cats, stimulation of efferent components of the carotid sinus or aortic nerves depressed chemoreceptor discharge from the relevant chemoreceptor afferents. The local application of 2% procaine hydrochloride to the sinus nerve trunk, peripheral to the site of the stimulating electrodes and proximal to that of the afferent nerve twig, abolished the depression of afferent chemoreceptor discharge caused by electrical stimulation; on washing the procaine away electrical stimulation once more induced depression of chemoreceptor discharge.2. The depressant effect of efferent stimulation on carotid chemoreceptor activity was still seen during complete carotid glomeral ischaemia. Atropine given by close intra‐arterial injection to the carotid body did not affect the depressant influence of efferent sinus nerve stimulation on carotid body chemoreceptor discharge.3. Stimulation of the sinus nerve efferents usually increased carotid body blood flow. Close arterial injection of atropine abolished this effect.4. The responses of glomeral blood flow and carotid chemoreceptor activity to efferent stimulation of the cut sinus nerve were not temporally related. It seems improbable that the depressant effect of such stimulation on chemoreceptor discharge was due to alterations of glomeral blood flow.5. Stimulation of the peripheral end of the cervical vagus in atropinized cats reduced chemoreceptor activity recorded in the ipsilateral aortic nerve.
The uptake of [14C]glycine by slices of mammalian spinal cord
Authors: Neal M. J. 
Published: December 2014

1. The accumulation of [14C]glycine by slices of mammalian spinal cord has been measured.2. When slices of rat cord were incubated at 37° C in a medium containing [14C]glycine, tissue:medium ratios of about 30:1 were attained after a 40 min incubation.3. After incubations at 37° C for 40 min, almost all (98%) the radioactivity in the tissue was present as unchanged [14C]glycine.4. The process responsible for [14C]glycine uptake showed many of the properties of an active transport system: it was temperature sensitive, required the presence of sodium ions in the external medium, was inhibited by dinitrophenol and ouabain and showed saturation kinetics.5. The estimated Km value of glycine was 3·1 × 10−5
M, and Vmax was 0·48 μ‐mole/min.g cord.6. The uptake of [14C]glycine was not affected by the presence of large molar excesses of
L‐histidine,
L‐proline,
L‐aspartate,
L‐glutamate,
L‐valine or GABA, but was inhibited in the presence of
L‐alanine and
L‐leucine.7. The uptake of [14C]glycine was not reduced by strychnine, but a significant reduction in uptake was produced by p‐hydroxymercuribenzoate.8. The uptake of [14C]glycine by the grey matter of rabbit spinal cord was 2 to 6 times greater than the uptake by slices of white matter incubated under the same conditions.9. Rat cerebral cortex, cerebellar cortex and medulla also accumulated [14C]glycine, and the uptake by the tissue slices in vitro appeared to parallel the concentration of glycine in these areas in vivo.10. It is suggested that the glycine uptake system may represent a possible mechanism for the inactivation of glycine at inhibitory synapses in the spinal cord.
Rapid changes and hysteresis in spatial integration for human rod vision
Authors: Hallett P. E. 
Published: December 2014

1. Two previous papers (Hallett, 1969a, b) were concerned with the visual threshold appropriate to a peripheral retinal point and in particular with the rapid changes in point threshold produced by illuminating the dark‐adapted eye with large brief duration backgrounds. This paper extends this approach to testing signals of larger subtense.2. Spatial integration for the rods can rapidly diminish and recover within a few hundred milliseconds.3. A brief duration background which raises the threshold at a retinal point as much as some steady background is more effective than the steady background in reducing the extent of spatial integration.4. Hysteresis can be substantial; the extent of spatial integration varies, even for a given point threshold, according to whether the threshold is rising or falling, or temporarily or permanently steady.5. A possible type of non‐linear model is discussed in the next paper (Hallett, 1971).
Release of endogenous noradrenaline from an isolated muscular artery
Authors: Bell C. , Vogt Marthe 
Published: December 2014

1. The release of noradrenaline by field stimulation of vasoconstrictor nerves has been studied in isolated preparations of the main uterine artery of the guinea‐pig.2. In preparations from virgin animals stimulation with trains of 3000 square pulses at 5 and 25 pulses/sec resulted in mean overflows of 0·56 ng/g.pulse and 1·53 ng/g.pulse respectively.3. Inhibition of monoamine oxidase and catechol‐O‐methyltransferase had no consistent effect on overflow at either stimulation frequency.4. Desmethylimipramine (10−5
M) caused, on the average, a 2·4‐fold increase in overflow following stimulation at 5 pulses/sec while phenoxybenzamine (10−5
M) caused a 3·8‐fold increase. Neither of these drugs caused a significant alteration of the overflow during stimulation at 25 pulses/sec.5. Treatment of the tissues with desmethylimipramine plus normetanephrine (4·5 × 10−4
M) caused no more increase in overflow than treatment with desmethylimipramine alone.6. It is concluded that enzymatic metabolism of noradrenaline at the synapse is of little functional importance in this tissue, and that the most important mechanism of transmitter inactivation is by nervous re‐uptake. Although phenoxybenzamine was more effective than desmethylimipramine in increasing transmitter overflow, no evidence was obtained to support the view that this effectiveness was due partly to blockade of ‘Uptake 2’.7. There was sometimes very low overflow of noradrenaline from arteries taken from animals in the last week of pregnancy. In these instances overflow following stimulation at 5 pulses/sec was not increased by phenoxybenzamine treatment of the tissue.8. Methylene blue and fluorescence microscopic techniques indicated that the terminal adrenergic axons in each artery possess approximately 8·74 × 105 varicosities. The mean tissue content of noradrenaline was found to be 9·6 μg/g or 29 ng/artery. These results have been correlated with known morphological and electrophysiological data to derive a peak post‐junctional concentration of noradrenaline during transmission of about 4 × 10−4
M.9. The fraction of total noradrenaline content of the artery released per pulse (under the influence of phenoxybenzamine) had a mean value of 2·2 × 10−4.
Action potentials and release of neurohypophysial hormones in vitro
Authors: Dreifuss J. J. , Kalnins Ilva , Kelly J. S. , Ruf K. B. 
Published: December 2014

1. Isolated rat neurohypophyses were studied in vitro and the hormones released on electrical stimulation of the pituitary stalk or on exposure to excess potassium were estimated by a milk‐ejection assay.2. The stalk was stimulated with trains of 500 stimuli, or multiples thereof, applied at different frequencies. Below frequencies of ca. 35 c/s, hormone release was found to depend on the total number of stimuli applied as well as on the frequency of stimulation. Above ca. 35 c/s, identical numbers of stimuli were progressively less effective as the frequency of stimulation was increased, and the dependence of the hormone output on the total number of stimuli was less apparent.3. The amplitude of the compound action potential recorded from the neurohypophysis following electrical stimulation of the stalk was found to decrease as a function of the frequency of stimulation. Stimulation at 50 c/s reduced its amplitude about sevenfold within 30 sec.4. The addition of tetrodotoxin (TTX) to the incubation media abolished the compound action potential recorded from the neural lobe as well as the release of hormones evoked by electrical stimulation. Resting release, however, was unaffected by TTX.5. In TTX‐treated neural lobes, excess potassium was still effective in eliciting graded secretory responses. This indicates the independence of the release process from the action potential generating mechanism and suggests that TTX‐paralysed preparations represent a useful model for the study of hormone release in the absence of conducted action potentials.6. The release of hormones from the neurohypophysis and the release of neurotransmitters at chemical synapses both depend on the entry of calcium into the nerve terminals following their depolarization by invading action potentials. In both systems, experimental separation of the release mechanism can be achieved by the use of TTX. These and other parallels suggest that the release process is similar.
Effects of cold, eating, efferent nerve stimulation and angiotensin on heart rate in sheep before and after autonomic blockade
Authors: Hays F. L. , Webster A. J. F. 
Published: December 2014

1. Effects of the natural stimuli of cold exposure and feeding on heart rate were tested in conscious sheep in which blockade of the cardiac efferent nerves was achieved by administration of propranolol and atropine. Effects of direct nerve stimulation, isoproterenol and angiotensin on heart rate before and after autonomic blockade were studied in acute preparations anaesthetized with pentobarbitone sodium.2. Propranolol reduced the extent of cardioacceleration induced both by exposure to cold and by eating. Heart rate in propranolol treated animals exposed to cold did not exceed about 120 beats/min. During eating, heart rate in propranolol treated animals showed no upper limit and increased on occasions to over 170 beats/min.3. Heart rate in conscious sheep following administration of atropine and propranolol was about 110 beats/min; in anaesthetized sheep following vagal section and propranolol it was usually about 120 beats/min. This was taken as intrinsic heart rate.4. Angiotensin administered to normal anaesthetized sheep usually reduced heart rate. After vagal section and propranolol, angiotensin injection usually, and angiotensin infusion invariably, increased heart rate.5. It was concluded that there exists in sheep a mechanism which during eating elevates heart rate by a means other than through the parasympathetic and sympatho‐adrenal systems. It is suggested that this mechanism involves a direct chronotropic effect of angiotensin secreted in association with eating.
The accumulation of [14C]5‐hydroxyindol‐3‐ylacetic acid by the rabbit choroid plexus in vitro
Authors: Pullar I. A. 
Published: December 2014

1. The lateral and fourth ventricular choroid plexuses of the rabbit have been shown to be capable of the in vitro accumulation of 5‐hydroxyindol‐3‐ylacetic acid (5‐HIAA).2. The accumulation of 5‐HIAA occurs against a concentration gradient and is dependent on metabolic energy.3. It is possible to inhibit the accumulation of 5‐HIAA by the presence of the dopamine metabolite, 3‐methoxy‐4‐hydroxyphenylacetic acid (HVA) or of probenecid in the incubation medium.4. It would appear that the characteristics of the accumulation of 5‐HIAA by the isolated choroid plexuses are consistent with the involvement of this tissue in the in vivo active transfer of 5‐HIAA from the c.s.f. to the blood.
A comparison of the spindles in two different muscles of the frog
Authors: Brown M. C. 
Published: December 2014

1. The responses of spindles in the iliofibularis muscle of frogs to stretch during either small motor nerve fibre stimulation or the application of suxamethonium were compared.2. All spindles which were excited by small motor nerve fibre stimulation were also excited by suxamethonium, and their responses to these two methods of excitation were very similar. The drug dose was usually 5‐10 μg/ml. but smaller and larger doses were effective. Large doses (> 100 μg/ml.) could sometimes lead to a reversible partial block of the spindle response to stretch.3. Suxamethonium also caused a prolonged contraction in extrafusal slow muscle fibres. This contraction was not responsible for the effect on the spindle, because the time course of its action on the muscle tension and on the spindle afferent was different.4. It was concluded that suxamethonium stimulated prolonged contraction in the small intrafusal muscle fibres, which are known to be innervated by the small motor nerve fibres.5. Only about half of the spindles in the iliofibularis muscle were excited by suxamethonium.6. In the sartorius muscle which has no slow extrafusal muscle fibres, no spindles were found to be excited by suxamethonium in the way characteristic of that due to small intrafusal muscle fibre contraction.7. It is concluded that, in frog muscles which have no slow extrafusal fibres, the muscle spindles do not have small intrafusal muscle fibres of the kind found in the iliofibularis muscle.