bluuebunny/crossref_metadata_2025_split huggingface dataset:
The relation of membrane changes to contraction in twitch muscle fibres
Authors: Heistracher P. , Hunt C. C. 
Published: December 2014

1. Contractile responses in short twitch‐type snake muscle fibres have been studied. These fibres are sufficiently short to allow fairly uniform changes in membrane potential along their length when current is passed through an intracellular micropipette. Active sodium permeability changes were blocked with tetrodotoxin (TTX), procaine, or by using solutions low in sodium. Current and voltage micropipettes were used to voltage‐clamp these fibres. Depolarization steps to about −40 mV evoked contractile responses, maximal tension being developed between −10 and 0 mV. The relation between contraction and membrane potential was sigmoid.2. Depolarization beyond a critical threshold produced an increment of outward current which inactivated with time. The threshold for this delayed rectification was normally similar to the threshold for contractile activation. Fibres exposed to high potassium showed a reversal of this inactivating current to slightly super‐threshold depolarizing pulses. At membrane potentials near 0 mV, no inactivating current was noted, while stronger depolarizing pulses produced an inactivating current in the normal direction. Fibres in high potassium show the same threshold for initiation of contraction as in normal solution.3. Thiocyanate, nitrate, and caffeine shifted the relation between membrane potential and contraction toward higher levels of membrane potential. The threshold for inactivating rectifying current failed to shift to a corresponding extent, although some shift in rectification which did not inactivate was evident.4. When depolarization was maintained, contractile tension was maximal for several seconds, then gradually disappeared. The rate of this contractile inactivation depended upon the level of depolarization.
The effects of age and environmental temperature on the blood concentrations of glucose, free fatty acids and glycerol in new‐born rabbits
Authors: Hardman M. J. , Hull D. 
Published: December 2014

1. The concentration of blood glucose, free fatty acids and serum glycerol of the doe, new‐born and young rabbits have been measured in order to evaluate the effects of age, starvation and environmental temperature on the circulating concentrations of these metabolites.2. The blood glucose, free fatty acid and glycerol concentrations were lower in the new‐born than in the mother rabbit.3. Starvation for 24 hr of new‐born and young rabbits in a thermal neutral environment did not alter the serum free fatty acid or glycerol concentrations. The blood glucose of unfed rabbits fell during the first 24 hr of life.4. Cold exposure (15 or 25° C) for 1 hr caused a rise in the concentration of blood glucose, serum free fatty acids and glycerol.5. When the metabolic response of new‐born and young rabbits to cold exposure was measured, it was found that there was a direct correlation between the serum glycerol concentration and the metabolic response. The greatest rise in the serum free fatty acids occurred in the blood of rabbits with the poorest metabolic response to cold.6. It is suggested that in the steady state during cold exposure the serum glycerol concentration may indicate the rate of triglyceride hydrolysis in brown adipose tissue.
Types of nervous activity which may be recorded from the carotid sinus nerve in the sheep foetus
Authors: Biscoe T. J. , Purves M. J. , Sampson S. R. 
Published: December 2014

1. In the sinus nerve of mature foetal sheep (120–147 days gestational age) three types of nerve activity have been demonstrated: (a) baroreceptor afferent, in which the nerve activity was synchronous with the pulse pressure wave and which followed pressure changes in the carotid sinus including those caused by compressing the umbilical cord. The discharge of nine out of twelve baroreceptor afferents increased with sympathetic stimulation, (b) a subtype of (a) in which there was irregular activity from pressure receptors which most probably represented baroreceptors discharging at or about threshold, and (c) in the older foetuses (130–147 days), there was activity which was unaffected by changes in carotid sinus pressure, Pa, O2 or NaCN but which increased in discharge rate with compression of the umbilical cord or with stimulation of the cervical sympathetic; this activity then increased with injection of NaCN and was thus identified as chemoreceptor in origin. In addition, a pathway originating in the cervical sympathetic and which passed through the superior cervical ganglion was demonstrated by evoking a compound action potential on stimulation of the preganglionic cervical sympathetic nerve.2. Recordings from pre‐ or post‐ganglionic cervical sympathetic nerves showed that spontaneous activity was present and increased when the umbilical cord was compressed.3. These results suggest that the carotid body chemoreceptors in the foetus are relatively insensitive to chemical changes and that, in their activation at birth, the sympathetic could be involved. Possible neural pathways and the mechanism of activation are discussed.
The secretion of gastric acid in response to a lack of metabolizable glucose
Authors: Colin-Jones D. G. , Himsworth R. L. 
Published: December 2014

1. The onset of the secretion of acid from the stomach of rats during insulin‐induced hypoglycaemia has been found to correspond to a mean plasma glucose concentration of 72 mg/100 ml. (equivalent to a blood glucose concentration of 44 mg/100 ml.).2. Infusions of the non‐metabolizable sugar, 3‐O‐methylglucose, into rats with denervated adrenal glands caused a large and sustained rise in the gastric acid output. This gastric acid secretion could be prevented by prior vagotomy or stopped, when previously established, by cutting the vagi or by the administration of glucose.3. A consistent relationship was demonstrated between the plasma concentration of glucose and the total concentration of glucoses (glucose plus 3‐O‐methylglucose) in the plasma at the onset of gastric acid secretion during the infusion of 3‐O‐methylglucose into these rats. The theoretical basis for this relationship is discussed.4. 3‐O‐methylglucose did not cause the release of gastric acid when infused into rats with intact sympathetic nervous systems owing to the effects of the secretion of adrenaline provoked by this agent.5. The qualitative and quantitative similarities between the factors governing both the secretion of gastric acid and the release of adrenaline in the absence of a sufficiency of metabolizable glucose are discussed. It is suggested that the reactions of both these systems under such circumstances are determined by chemoreceptors which possess identical characteristics.
The effect of ambient temperature upon post‐natal changes in oxygen consumption of the guinea‐pig
Authors: Adamsons K. , Blumberg E. , Joelsson I. 
Published: December 2014

1. The effect of thermal environment and administration of progesterone upon minimal oxygen consumption and thermal stability of the new‐born guinea‐pig has been investigated.2. It was found that the ambient temperature at which the new‐born is reared does not influence minimal oxygen consumption although it modifies the response to cold.3. Thermal stability was decreased in animals raised in a warm environment.4. Minimal oxygen consumption per unit body weight during the neonatal period increased 25%, most of the increase taking place within 16 hr after birth.5. Decrease in the relative mass of brown adipose tissue was least in new‐borns maintained at a high ambient temperature.6. Administration of progesterone did not affect oxygen consumption, body temperature and thermal stability of the new‐born.
Correlation between transmission and structure in avian ciliary ganglion synapses
Authors: Hess A. , Pilar G. , Weakly J. N. 
Published: December 2014

1. Extracellular responses from post‐ganglionic axons of pigeon and chick isolated ciliary ganglia were elicited by stimulation of the presynaptic nerve. Intracellular recordings were also obtained from newly hatched pigeon and chick ganglion cells. The fine structure of ganglia from pigeons of various ages was examined with the electron microscope.2. In ganglia from chick embryos and pigeons up to 10 days old, the extracellular response was unimodal with a long latency and could be blocked by the addition of
D‐tubocurarine (
D‐TC) or hexamethonium to the bathing solution. A bimodal extracellular response appeared in pigeons about 10 days after hatching. Only the second peak of the response could be blocked by
D‐TC or hexamethonium. The response recorded from 22 to 26‐day‐old pigeons was similar to that seen in the adult.3. The intracellular recordings from ganglion cells of 2‐week‐old pigeons exhibit two post‐synaptic potentials elicited by presynaptic stimulation. The first post‐synaptic potential appears to be due to current flow through the ganglion cell during the presynaptic action potential. The second is chemically mediated. In pigeons from 1 to 6 days old, only the second post‐synaptic potential is observed.4. The presynaptic terminals in the 4‐day‐old birds were in the form of calyces. In pigeons 7 days old or older, boutons appeared. The boutons were presumably formed as a result of cleavage of calyciform nerve terminals. Myelin was seen first in the 7‐day‐old pigeon, was well developed in the 16‐day‐old bird, and persisted in the adults.5. In adult ganglia, the first component of the extracellular response decreased and was finally abolished after 10–12 hr of superfusion with Tyrode solution. The second component of the response increased concomitantly. The only anatomical change noted in the ganglia after soaking was the disruption and separation of the myelin lamellae from each other and from around the ganglion and presynaptic terminals.6. It is concluded that the myelin is necessary for electrical transmission in the pigeon ciliary ganglion.
Impulse functions for human rod vision
Authors: Hallett P. E. 
Published: December 2014

1. This paper presents accurate increment threshold data for human rod vision for a small number of experimental parameters. The test is small and brief and the large background is either steady or transient.2. The linear threshold disturbance due to an impulse background consists of an input dependent exponential growth phase and an exponential recovery phase of more or less fixed time constant (ca. 0·08 sec).3. The data are treated by applying signal/noise decision theory to a hypothetical filter with two shot noise inputs, viz. the testing signal and the background. The gain and time course of the impulse function of the filter are slightly affected by the magnitude of the input.4. A linear approach is useful since the impulse functions for dark or light‐adapted rod vision yield independent information about quantities which have previously only been used to describe the increment thresholds for small tests on steady backgrounds, viz. the integration time and dark light of the fully dark‐adapted eye and the gain changes (or changes in the signal/background ratio) which occur on progressive light adaptation.
A study of the parameters of electrical stimulation of unmyelinated fibres in the pituitary stalk
Authors: Harris G. W. , Manabe Y. , Ruf K. B. 
Published: December 2014

1. The milk‐ejection response in lactating rabbits has been used to study the effect of electrical stimuli of different types applied to the supraopticohypophysial tract in the pituitary stalk.2. Sine‐wave alternating‐current pulses were compared with balanced biphasic square‐wave pulses of the same frequency and peak‐to‐peak current strength. At a pulse duration of 2‐4 msec the square‐wave stimulation was less effective than the sine wave, but at a pulse duration of 8 msec and over, more effective.3. Above threshold levels of 0·12 mA for the current strength, and of 0·5 msec for the pulse duration, the response increased with increasing current strengths to 2·4 mA and increasing pulse durations to 10 msec.4. With constant and effective strength and duration of the pulse a slight diminution of the response was seen as the frequency was diminished from 100/sec to 50/sec. Further diminution in the frequency revealed that at some point between 50 and 10 c/s a sudden abrupt diminution in the magnitude of the responses occurred over a small range of frequency. This was a reversible phenomenon and it is suggested that it may be related to neurosecretory events occurring in the nerve terminals.5. Stimuli with parameters within the ranges mentioned above are effective in eliciting an oxytocic response on the uterus in the rabbit and ovulation responses (when applied to the hypothalamus) in rats and rabbits. It appears likely that stimuli with such parameters are suitable for experiments concerned with stimulation of the hypothalamus.
Modulation of noradrenaline incorporation by nerve activities in the rat submaxillary gland
Authors: Chang C. C. , Chiueh C. C. 
Published: December 2014

1. Rats were anaesthetized with chloralose and prepared for electrical stimulation of the cervical sympathetic trunk. The effect of such stimulation was studied on the incorporation of intravenously infused [3H]noradrenaline, [3H]adrenaline or [3H]dopamine by the submaxillary gland.2. A train of 200 stimuli every min for 30 min at 20/sec increased the total incorporation of [3H]noradrenaline by 92% over the unstimulated side of the gland, at 50/sec by about 200% and at 3·3/sec by about 30%. The incorporation of [3H]adrenaline and of [3H]dopamine was also increased by sympathetic stimulation.3. The increases in unaltered [3H]noradrenaline and its metabolites were proportional to the increase in total radioactivity.4. Mean venous outflow from the gland was decreased by 15–30% by the sympathetic stimulation.5. After elimination of extraneuronal binding of noradrenaline by ligation of the common excretory ducts, nerve stimulation still increased incorporation.6. Inhibition of normetanephrine production by pyrogallol did not antagonize the nerve impulse‐mediated increase of [3H]noradrenaline incorporation. α‐Methyltyrosine was also without effect.7. Desmethylimipramine and bretylium completely abolished the nerve impulse‐mediated increase of [3H]noradrenaline incorporation in concentrations which did not affect the control uptake or abolish adrenergic transmission.8. Reserpine, guanethidine and phenoxybenzamine antagonized both the control and nerve impulse‐mediated incorporations of [3H]noradrenaline.9. The results indicate that nerve impulses modulate the incorporation of transmitter amine at the neuronal membrane. Possible mechanisms for this modulation are discussed.
Changes in extracellular potassium concentration produced by neuronal activity in the central nervous system of the leech
Authors: Baylor D. A. , Nicholls J. G. 
Published: December 2014

1. Experiments were made on single neurones and glial cells in the central nervous system of the leech to study the accumulation of K that occurs in the extracellular spaces around neurones as a result of impulse activity.2. The resting potential of a neurone is too insensitive to be used for the estimation of small changes in K concentration. The undershoot of the action potential, however, provided a reliable indicator of the K accumulation that occurs around a neurone during activity.3. After a single impluse the amplitude of the undershoot of a second action potential was decreased; the effect corresponded to a peak increase in K concentration of about 0·8 m
M/l. immediately after the spike and declined exponentially with a time constant of about 100 msec. With trains of impulses the K concentration increased exponentially, again with a time constant of about 100 msec. The final value of K depended on the frequency and could build up to about double the normal concentration of 4 m
M/l.4. The build‐up of K was markedly reduced when the extracellular space surrounding a neurone was enlarged by removing its glial investment.5. Synchronous, repetitive activation of groups of neurones caused a slow depolarization of neighbouring glial cells in the
C.N.S. of the leech, similar to that observed in amphibia and mammals. The change in glial membrane potential was also used to estimate the changes in K concentration and these values agreed with measurements derived from the undershoot.6. Increases of K concentration in the bathing fluid of the same order as those caused by neural firing markedly affected the frequency of ‘spontaneous’ neuronal discharges and synaptic potentials occurring within certain neurones in the
C.N.S.7. The possible effects of physiologically occurring increases of K concentration on integration are discussed.
Chemical and electrical synaptic connexions between cutaneous mechanoreceptor neurones in the central nervous system of the leech
Authors: Baylor D. A. , Nicholls J. G. 
Published: December 2014

Experiments have been made to study the synaptic connexions between sensory cells in the
C.N.S. of the leech. Each segmental ganglion contains six neurones that respond specifically to light touch applied to the skin; each of these ‘touch cells’ innervates a discrete area on the surface of the body and has a characteristic set of properties by which it can be recognized. Using intracellular electrodes it has been shown that these sensory cells interact with one another through chemical and electrical synapses by way of a stereotyped set of pathways.1. Action potentials occurring in one touch cell gave rise to synaptic potentials in the five other touch cells in the same ganglion and also in the three ipsilateral touch cells in the adjacent ganglia. Thus, synaptic interactions took place between sensory cells whose receptive fields lay within the same segment and on the same side of adjacent segments.2. The post‐synaptic potentials consisted of a short‐latency coupling potential, followed by an excitatory potential and a number of inhibitory potentials. These delayed synaptic potentials occurred inconsistently and with a variable latency; they could also be recorded in the cell which had been stimulated. All of the touch cells appeared to be equally effective in initiating synaptic potentials.3. The short‐latency coupling potential was shown to be mediated through an electrical synapse by observing a voltage change in one touch cell when current was injected into its neighbour. It was not abolished by high concentrations of Mg in the bathing fluid, which blocked chemical synapses in this ganglion. This electrical synapse displayed remarkable rectification; a depolarization could spread from cell to cell in both directions, while a hyperpolarization could spread in neither.4. The inhibitory potentials were reversed by injecting Cl into the cell. In Cl‐free Ringer solution this effect was so marked that the reversed IPSPs caused long trains of impulses in touch cells, which tended to excite each other by a process of positive feed‐back.5. Synaptic potentials evoked by activation of a touch cell did not usually reach threshold since excitation and inhibition tended to cancel. The connexions between touch cells that mediated the delayed excitatory and inhibitory potentials are polysynaptic; the interneurones have not yet been found but some of their connexions could be inferred from electrical recordings.6. Action potentials in sensory cells of a different modality (responding to pressure) also initiated synaptic potentials in the same family of touch cells.7. The possible significance for integration of these synaptic interactions between sensory cells is discussed.
Hypothalamic temperature and the regulation of respiration of the ox exposed to severe heat
Authors: Findlay J. D. , Hales J. R. S. 
Published: December 2014

1. Thermodes have been chronically implanted in the hypothalamus of the ox.2. During exposure of the ox to severe heat stress, rapid shallow panting changed to slower deeper panting when hypothalamic temperature (Thy) was approximately 40·5° C. With subsequent rapid ambient cooling, hypothalamic temperature declined rapidly, and there was a reversion to rapid shallow panting before respiration slowly returned to normal.3. When hypothalamic temperature and rectal temperature (TR) had reached about 40° C, raising hypothalamic temperature to about 41·4° C did not cause the onset of slower deeper panting.4. When hypothalamic temperature and rectal temperature had exceeded about 41° C and slower deeper panting was well established, lowering hypothalamic temperature to about 40° C did not cause any reversion to rapid shallow panting.5. When hypothalamic temperature and rectal temperature had reached about 40° C, holding hypothalamic temperature at 40° C did not prevent the onset of the slower deeper phase of panting.6. Under moderate heat stress when hypothalamic temperature was approximately 39·9° C and rectal temperature was approximately 40·4° C, raising hypothalamic temperature at the same rate as that which was associated with the onset of slower deeper panting during severe heat stress, resulted in a parallel increase in the respiratory frequency and fall in rectal temperature; there was no change to the slower deeper form of panting.7. Holding hypothalamic temperature at 41·7–42° C during post‐heat cooling did not prevent the reversion to rapid shallow panting.8. It was concluded that the change from rapid shallow to slower deeper panting during severe heat stress, and the reversion to rapid shallow panting during subsequent cooling, were not the result of changes in temperature of the hypothalamic thermoregulatory centres.
Echo‐location and evoked potentials of bats after ablation of inferior colliculus
Authors: Suga N. 
Published: December 2014

1. Echo‐location and evoked potentials of blinded Yuma bats (Myotis yumanensis) were studied before and after ablation of the inferior colliculus (I.C.). A task of obstacle‐avoidance was given to the bats: hits and misses of strands in the flight path were counted. Orientation sounds emitted by the bats during flight were recorded.2. Bilateral ablation of the dorso‐medial region of I.C. including the internuclear cortex and commissure had no effect on obstacle‐avoidance performance. The bats avoided even strands of 0·2 mm diameter with orientation sounds.3. Bilateral ablation of the dorsal half of I.C. including the external nucleus (lateral cortex) also had no effect on echo‐location.4. Bilateral ablation of the ventral half of I.C. caused severe deficiency in ability to avoid obstacles. The main nucleus appeared to be very important for echo‐location. When bilateral ablation including the main nucleus was moderate, the bats failed to avoid strands of less than 0·5 mm diameter in spite of detecting them, but avoided large obstacles such as 3·7 mm strands. With severe bilateral ablation including the main nucleus, the bats did not avoid even the 3·7 mm strands in spite of frequent emission of orientation sounds, but often avoided crashing into the wall.5. Severe unilateral ablation of I.C. including the main nucleus and a part of the lateral lemniscus had no effect on ability to avoid obstacles. Since sound localization by such bats are not explained by Van Bergeijk's model based on Békésy's, a modification of Van Bergeijk's model has to be considered.6. Of the positive evoked potentials recorded with an active electrode placed at the dorsal surface of I.C., the slow component with a 7–9 msec peak latency reflected activity of inferior collicular neurones, while the fast component (N4) with a 3 msec peak latency represented activity of ascending lateral lemniscal fibres.