bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantal independence and uniformity of presynaptic release kinetics at the frog neuromuscular junction
Authors: Barrett Ellen F. , Stevens C. F. 
Published: December 2014

1. Amplitude and latency fluctuations of the end‐plate potential at the frog neuromuscular junction were studied simultaneously at low temperatures, using intracellular or focal extracellular recording techniques and average quantal contents between 0·5 and 3.2. At the release rates studied, the evoked release of one quantum has in most cases no significant effect on the probability of subsequent quantal release to the same stimulus, confirming the mutual independence of quantal releases in this preparation.3. An equation derived from Poisson's law was applied to a histogram of the latencies of the first quantum released on each of a series of trials, to predict the average quantal content of end‐plate responses originating at various times after nerve stimulation. The shape of the predicted time distribution of quantal contents usually agreed closely with that of the experimentally observed time distribution of end‐plate response amplitudes. This agreement demonstrates that both the amplitude and the latency fluctuations of the end‐plate response result from one presynaptic stochastic process that is uniform in magnitude and time course after each stimulus.4. Analysis of extracellular records from synaptic regions with a history of extensive activity often suggested the existence of depressive interaction among quantal releases, perhaps caused by depletion of the supply of releasable quanta.
On the mechanism of barbiturate anaesthesia
Authors: Richards C. D. 
Published: December 2014

1. The effects of pentobarbitone (0·05–0·6 m
M in saline solution) on the evoked field potentials of in vitro preparations of guinea‐pig olfactory cortex were studied.2. The evoked field potentials comprised an initial diphasic wave — the lateral olfactory tract (l.o.t.) compound action potential — followed by a surface negative wave (e.p.s.p) of 1–3 mV amplitude and about 10 msec duration. Superimposed on the negative wave were a number of positive peaks (population spikes).3. Pentobarbitone depressed the e.p.s.p. but not the l.o.t. compound action potential. The number and size of the population spikes were progressively reduced as the e.p.s.p. became depressed, indicating a failure of transmission through the cortical relay. The e.p.s.p. depression increased with increasing concentrations of pentobarbitone.4. Pentobarbitone had no effect on the threshold to electrical stimulation of the l.o.t. fibres or on that of the post‐synaptic cells to synaptic excitation.5. Post‐tetanic potentiation and frequency potentiation were either of normal magnitude or were enhanced in the presence of 0·2–0·3 m
M pentobarbitone.6. It is concluded that pentobarbitone probably reduces the output of transmitter from the presynaptic nerve terminals of the olfactory cortex and that this mechanism could be the basis of the depressant action of the barbiturates.
The effect of stretching the superior vena caval—right atrial junction on right atrial receptors in the dog
Authors: Kappagoda C. T. , Linden R. J. , Snow H. M. 
Published: December 2014

1. Action potentials were recorded from fibres in the right cervical vagus, the receptor endings of which were localized to the endocardial surface of the superior vena caval—right atrial junction.2. Stretching the junction between the superior vena cava and the right atrium without obstructing venous return caused an increase in the discharge of these fibres. This increase in impulse frequency was similar to that caused by small changes in mean right atrial pressure (range 0–13·5 cm H2O).3. This evidence supports the earlier suggestion that stimulation of the right atrial receptors by stretching the superior vena caval—right atrial junction causes a reflex increase in heart rate.
Compensatory renal growth after unilateral nephrectomy in the new‐born rat
Authors: Dicker S. E. , Shirley D. G. 
Published: December 2014

1. The right kidney in a series of control rats aged between 5 days and 115 days was weighed. The kidney weight/body weight ratio was greater in young than in older rats, but decreased linearly with increasing age.2. After unilateral nephrectomy of rats 5 days old, the remaining kidney underwent compensatory growth. The rate and extent of this growth were greater than in adult rats.3. The concentrations of RNA and DNA in the renal cortex and medulla of rats 5 days old were higher than in adult animals. The concentrations of the two nucleic acids fell with age, and reached adult levels after approximately 6 weeks.4. After unilateral nephrectomy of rats 5 days old, the concentrations of RNA and DNA in the medulla were not significantly different from those in control animals. In the cortex, however, there was a delayed increase in the RNA/DNA ratio, which reached a level some 12% higher than that in control rats. This increase was smaller than that observed in unilaterally nephrectomized adult rats.5. The cortical QO2 of the remaining kidney of unilaterally nephrectomized new‐born rats was elevated by some 20% within 1 day of unilateral nephrectomy. Cortical QO2's remained higher than those of control animals for 3–4 weeks.6. Since after unilateral nephrectomy, the increase in renal mass in new‐borns was greater than that in adults, whereas the degree of cortical cellular hypertrophy (as estimated by the RNA/DNA ratio) was smaller than in adults, it is likely that in new‐born animals a significant contribution to compensatory growth comes from cellular hyperplasia.
Delayed release of transmitter at the frog neuromuscular junction
Authors: Rahamimoff R. , Yaari Y. 
Published: December 2014

1. After the end‐plate potential (e.p.p.) there is an increase in the frequency of the miniature e.p.p.s. This delayed release of transmitter was studied at the frog neuromuscular junction, using conventional intracellular and extracellular recording techniques. E.p.p. amplitude was kept subthreshold by subnormal concentrations of activating divalent ions.2. The ratio delayed release: initial release had values between 2 and 140%, depending on the experimental conditions; it decreased with an increase in Ca concentration and quantal content.3. Delayed release is larger at low temperature than at room temperature.4. Delayed release is statistically independent of the amplitude of the preceding e.p.p.5. The time course of the decay of the delayed release is monotonic when strontium is the activating divalent ion; it shows a ‘dip’ in more than 50% of the cases when Ca activated release.6. The results were discussed in terms of the residual Ca ion hypothesis.
Cutaneous convergence on to the climbing fibre input to cerebellar Purkyně cells
Authors: Leicht Rolf , Rowe Mark J. , Schmidt Robert F. 
Published: December 2014

1. In cats anaesthetized with Nembutal, the cutaneous receptive fields of individual cerebellar climbing fibres were assessed by recording the climbing fibre responses of single Purkyně cells following controlled mechanical stimulation (air jets, vibration, taps, pressure) of the foot pads of all four limbs and of the hairy skin of the limbs and the body.2. Three major types of cutaneous receptive fields of individual climbing fibres were recognized: (a) restricted fields generally confined to the distal areas of one limb only; (b) circumscribed fields on the distal areas of two to four limbs (discontinuous fields); and (c) widespread continuous fields extending over all or almost all of the body surface. A fourth group appears to receive cutaneous inputs from one limb and sensory input from deeper structures in other limbs.3. Thresholds for tapping of the foot pads were often quite low (< 100 μm indentation), and there was no noticeable difference in the distribution of thresholds between the climbing fibres having restricted or more widespread cutaneous receptive fields. Similarly, the latencies of climbing fibre responses evoked by vibration and tapping were in the same ranges for climbing fibres with receptive fields restricted to one limb only and for those having more widespread fields.4. In regard to location in the anterior lobe of the cerebellum it was found that those climbing fibres receiving inputs only from the ipsilateral forelimb projected to Purkyně cells located almost entirely in lobule V, whereas all other climbing fibres with restricted or more widespread receptive fields projected to Purkyně cells distributed widely within lobules II to V.
Thresholds of cortical activation of baboon α‐ and γ‐motoneurones during halothane anaesthesia
Authors: Koeze T. H. 
Published: December 2014

1. In the halothane anaesthetized baboon the threshold for cortically elicited primary and secondary spindle afferent discharge was compared to the threshold at the ‘best point’ for a cortically elicited tibialis anticus tension change.2. The cortical threshold for eliciting a tension change was greater than the cortical threshold for eliciting spindle afferent discharge for some afferents and less for other afferents.3. The pattern of cortically elicited spindle afferent discharge during muscle stretch suggested static γ‐motoneurone activation. No convincing evidence of dynamic γ‐motoneurone activation was seen.4. Inhibition of spindle afferent discharge was occasionally found and the ‘best point’ was the same as the cortical ‘best point’ for eliciting monosynaptic α‐motoneurone activity. This result suggested that the cortical projections which inhibit the pre‐existent activity of static γ‐motoneurones are in a close anatomical relation to those cortical projections which elicit activity of α‐ and static γ‐motoneurones.
The effect of lecithin on intestinal cholesterol uptake by rat intestine in vitro
Authors: Rampone Alfred J. 
Published: December 2014

1. Sacs 20 cm long were obtained from the upper half of the small intestine of bile fistula rats (bile duct cannulated 48 hours previously). The sacs were everted, filled with oxygenated phosphate buffer and incubated 1 hr at 37° C in 25 ml. of a buffered micellar solution of oleic acid (0·6 m
M), mono‐olein (0·3 m
M), sodium taurocholate (4·8 m
M) and 3H‐labelled cholesterol (0·15 m
M) plus glucose (28 m
M).2. After incubation the amount of [3H]cholesterol taken up by the mucosal tissue was measured. It averaged 200 n‐mole/hr.g tissue wet wt. ± 6 (
S.E.).3. Adding 3 ml. whole rate bile with other factors unchanged caused cholesterol uptake to decrease by 50% in confirmation of previous studies.4. Adding purified lecithin obtained from rat liver tissue, and from egg yolks, similarly decreased cholesterol uptake. A significant response was obtained with 2·5 mg liver lecithin (concentration 0·13 m
M) and a near maximum response with 15 mg (concentration 0·80 m
M). 10 mg lecithin decreased uptake by an amount equivalent to that obtained with 3 ml. whole bile.5. Lecithin is an active component of whole bile causing reduced intestinal cholesterol uptake from micelles.6. The decreased uptake of cholesterol in the presence of lecithin may have been the result of expansion of the cholesterol‐containing micelles with consequent reduction in cholesterol permeability.
The effect of adrenalectomy or pharmacological inhibition of adrenocortical function on macromolecule uptake by the new‐born rat intestine
Authors: Daniels V. G. , Hardy R. N. , Malinowska K. W. 
Published: December 2014

1. Bilateral adrenalectomy in 18‐day‐old rats resulted in an extension by approximately 4 days of the period during which the villous epithelial cells of the small intestine took up polyvinyl pyrrolidone (PVP) of mean mol. wt. 160,000.2. The eventual termination of PVP uptake (‘closure’) closely resembled normal closure in control animals: the time course of the decline in uptake and the histological changes indicated that more mature ‘PVP‐impermeable’ cells progressively ascended the villi.3. Injection of Metopirone was ineffective in animals 10 days after birth, but when injected after day 13 caused closure within 3 days.4. Metopirone injection significantly reduced the plasma concentration of corticosterone and caused a marked rise in the plasma concentration of deoxycorticosterone.5. Aminoglutethimide injection also produced precocious closure and had an effect similar to Metopirone on the plasma concentrations of corticosterone and deoxycorticosterone.6. Injection of Metopirone or aminoglutethimide increased the relative adrenal weight compared with control animals. Aminoglutethimide was more effective and caused approximately a 100% increase in adrenal weight.
Thermoregulatory changes induced during heat acclimatization by controlled hyperthermia in man
Authors: Henane R. , Valatx J. L. 
Published: December 2014

1. Heat acclimatization has been carried out by a controlled hyperthermia procedure, and induced thermoregulatory changes have been investigated for nine fit young men.2. During the experiments two types of thermal responses became apparent. The subjects tolerating the rise in the central temperature during hyperthermia displayed a marked improvement of their sweating capacity and their sweating performances, and a parallel shift towards lower body temperatures of the curves relating sweat rate to tympanic, rectal and mean skin temperatures.3. This shift occurred without any change in the slope, that is without any change in the gain of the central control system. It was accompanied by a concomitant shift of the threshold of sweating onset, so that for a given central temperature there was a higher sweat rate following treatment.4. The sweat decline appeared late in tolerant subjects. This decline was early in the intolerant subjects and appeared as early as the first day of heat treatment. Moreover, these subjects displayed no increase of sweat output with repeated sessions of heat treatment.5. The core—periphery temperature gradient measured during the cooling stage did not change in the tolerant subjects when acclimatization had developed. This gradient increased in the intolerant subjects because deep temperature decreased slowly whilst skin temperature decreased rapidly. The core of intolerant subjects retained the stored heat and dissipated it slowly. The tolerant subjects seemed on the contrary to display in the same conditions increased tissue conductance enabling rapid dissipation of the stored heat.
Electrophysiology of cardiac function in teleosts: cholinergically mediated inhibition and rebound excitation
Authors: Cobb J. L. S. , Santer R. M. 
Published: December 2014

1. A study has been made on the responses of the plaice (Pleuronectes platessa) heart, isolated and in situ to differential vagal stimulation using intra‐ and extracellular recording electrodes. The effects of direct application of acetylcholine and catecholamines and their respective blocking agents are also reported.2. Vagal stimulation at 7 Hz totally inhibits heart beat whilst stimulation at 2–3 Hz accelerates it. Both these effects are blocked by atropine (10−6 g/ml.). Bretylium (10−5 g/ml.) and pronethalol (10−6 g/ml.) have no effect upon either response to vagal stimulation.3. On cessation of prolonged inhibitory vagal stimulation there is a marked increase in the heart rate, and in quiescent hearts one or two beats are initiated after stimulation.4. Vagal stimulation gives rise to a hyperpolarization in atrial cells. It is proposed that all the excitatory effects of vagal stimulation are due to rebound excitation from an inhibitory hyperpolarization. At high frequencies the hyperpolarizations summate to give rise to total inhibition. At lower frequencies of stimulation the heart beat is increased to rates dependent on interaction between the time course of the hyperpolarization and the refractory period of the heart. Both effects are cholinergically mediated.5. The rebound excitation in response to vagal stimulation (post‐vagal tachycardia) persists in response to stimulation of the atrial myocardium in the presence of atropine (10−6 g/ml.) and bretylium (10−5 g/ml.). It is therefore suggested that this is a response of the muscle cell membrane to vagal stimulation and is not nerve‐mediated.
Spontaneous salivation in the rabbit submandibular gland
Authors: Smaje L. H. 
Published: December 2014

1. Salivation has been studied in the submandibular gland of the rabbit. A very slow spontaneous salivation took place when all possibility of nerve influence had been excluded. Salivation was not due to ultrafiltration.2. The ‘spontaneous’ saliva had a mean K concentration of 148 m
M and Na concentration of 46 m
M. With increasing salivation rate produced by parasympathetic nerve stimulation, K concentration fell to a plateau level of about 30 m
M whilst Na concentration fell rapidly to reach the low value of 3 m
M, then began to rise again at the higher flow rates.3. Ligation of the submandibular duct produced a reversal of the ion concentrations in spontaneous saliva. By 4 days K concentration was lower and that of Na higher than control values until by 2 weeks the effect was maximal with mean concentrations of 25 m
M for K and 153 m
M for Na.4. Ouabain increased the spontaneous salivation rate and ethacrynic acid slowed or prevented it altogether. On the basis of the known sites of action of these drugs it is postulated that two pumps are involved in the regulation of spontaneous salivation. There appears to be basal activity of an acinar mechanism pumping NaCl into the lumen, taking water with it. This pump is activated directly or indirectly by the intracellular Na concentration which itself is controlled by an Na—K exchange pump.5. Excitation of the sympathetic trunk produced a small, though definite, increase in salivation rate. There was evidence that myoepithelial cells might also be involved in the sympathetic response and that they were activated by α receptor stimulation. Salivation evoked by sympathetic nerve stimulation would seem to be a response to β receptor stimulation, but the possibility that activation of both α and β receptors was required could not be excluded entirely.
The interaction of sodium and potassium with the sodium pump in red cells
Authors: Garay R. P. , Garrahan P. J. 
Published: December 2014

1. At high internal K concentrations the efflux of Na from red cells increases with internal Na concentration following an S‐shaped curve. As internal K is reduced the S‐shaped region and the value of internal Na for which the Na efflux is half‐maximal are both shifted progressively towards zero.2. The effects of internal Na on the shape of the Na efflux curves can be quantitatively accounted for if it is assumed that the rate of Na efflux is linearly related to the number of pump units having three identical and non‐interacting sites occupied by Na.3. The effects of internal K on the shape of the Na efflux curves are fully explained if it is assumed that the inner sites for Na of the Na pump also behave as identical and non‐interacting sites for internal K, being the K‐carrier complexes unable to promote Na translocation. The apparent affinity of the Na pump for internal K is about 50 times less than for internal Na.4. Internal K not only alters the apparent affinity of the Na pump for Na, but also affects its turnover rate. The turnover rate of Na: K exchange increases with internal K following a curve which saturates at about 30 m
M internal K. The turnover rate for Na:Na exchange increases linearly with internal K.5. The linear dependence of the rate of Na:Na exchange on internal K explains why, when internal Na is increased at the expense of internal K, the rate of Na:Na exchange progressively decreases after passing through a maximum.6. The effects of external Na on the rate of Na:Na exchange can be satisfactorily explained assuming that they are due to the occupation by external Na of three identical and non‐interacting sites on each pump unit. The apparent affinity of the Na pump for external Na is about 160 times less than the apparent affinity for internal Na.7. Under all the experimental conditions tested, it was found that the relation between flux and cation concentration at one of the surfaces of the cell membrane is altered only by a constant factor by changes in the cation composition at the opposite surface of the cell membrane. This fact strongly suggests that there are no interactions between the inner and outer sites of the Na pump.8. The effects of inner and outer cations on both the Na:K and the Na:Na exchanges catalysed by the Na pump suggest that cation fluxes are proportional to the number of pump units having its inner and outer sites simultaneously occupied by the relevant cations. It seems therefore that sequential models for ion transort do not provide an adequate description of the molecular mechanism of active transport in red cells.
The effects of lung reflexes on laryngeal resistance and motoneurone discharge
Authors: Stransky A. , Szereda‐Przestaszewska Małgorzata , Widdicombe J. G. 
Published: December 2014

1. The reflex action of stimulation of alveolar J–receptors and of airway epithelial irritant receptors has been investigated on laryngeal resistance to airflow and on laryngeal motoneurone discharge in cats and rabbits.2. Resistance to airflow of the innervated larynx was measured (1) with the larynx isolated in situ with constant flow from the trachea to a pharyngeal opening; and (2) with the animal breathing through the larynx and the pharyngeal opening. With both methods resistance was determined from the relationship between translaryngeal pressure and airflow.3. In control conditions the laryngeal resistance was about one tenth of total lung resistance.4.
I.V. injections of phenyl diguanide (to stimulate J‐receptors) caused apnoea and complete closure of the larynx, followed by rapid shallow breathing with expiratory constrictions of the larynx. Expiratory laryngeal motoneurones were strongly stimulated.5. The laryngeal responses to phenyl diguanide were nearly abolished by bilateral vagotomy in the chest (below the origin of the recurrent laryngeal nerves), and were absent on injection of the drug into the left atrium; the motoneurone responses were abolished by vagotomy and lessened by paralysis and artificial ventilation.6.
I.V. injections of histamine acid phosphate or inhalation of an aerosol of the drug in solution (to stimulate lung irritant receptors) caused tachypnoea and expiratory constrictions of the larynx, and increased discharges in expiratory laryngeal motoneurones.7. The laryngeal responses to histamine were more than halved by bilateral intrathoracic vagotomy.8. Phenyl diguanide and histamine increased the frequency of the discharge of inspiratory laryngeal motoneurones, but reduced the number of impulses per inspiratory phase. Laryngeal resistance in inspiration was usually increased.
Phosphate excretion in the laying hen (Gallus domesticus)
Authors: Martindale L. 
Published: December 2014

1. The excretion of phosphate during the calcifying and non‐calcifying phases of egg formation was studied.2. The pattern of phosphate excretion was observed during increasing body loads of phosphate.3. A tubular mechanism for phosphate excretion is proposed in which tubular phosphate secretion occurs proximal to, or coincidental with reabsorption.4. Parathyroid extract increased the rate of phosphate excretion and appeared to inhibit both the reabsorptive and secretory mechanisms.5. The pattern of excretion of phosphate loads by hens in the calcifying phase was closely similar to that of birds in the non‐calcifying phase when treated with parathyroid extract.6. The relationship between shell calcification and the parathyroids is discussed.