bluuebunny/crossref_metadata_2025_split huggingface dataset:
An electrophysiological analysis of the uptake of noradrenaline at sympathetic nerve terminals
Authors: Bennett M. R. 
Published: December 2014

1. An electrophysiological analysis has been made of the uptake of NAd in the sympathetic nerve terminals of the isolated vas deferens of the mouse. The amplitude of the excitatory junction potentials (e.j.p.s) recorded intracellularly in smooth muscle cells was taken as a measure of the NAd output per impulse from the terminals of sympathetic axons.2. Neuronal uptake blockers (desipramine and cocaine) greatly depressed the amplitude of all e.j.p.s after the first in a short train (< 100) at high frequencies (≥ 1 Hz).3. Blocking neuronal uptake did not affect the time course of decline in amplitude of the e.j.p. during long trains of stimulation over several minutes, apart from the immediate depression in the e.j.p. following the first few impulses.4. The time course of decline of the e.j.p. amplitude during continual stimulation, when both neuronal uptake and synthesis was blocked, was similar to that when only synthesis was blocked, apart from the immediate depression following the first few impulses.5. Phenoxybenzamine reversed the normal depression in e.j.p. amplitude observed at high frequencies (≥ 1 Hz) to facilitation. This facilitation lasted for several minutes of high frequency stimulation.6. A model has been proposed of the sympathetic nerve terminal, in which NAd is released by each nerve impulse in a train from a small pool in the nerve terminal, which is principally replenished by uptake of the NAd released by the immediately preceding impulses in the train. The pool is replenished to a less extent by transmitter located in two stores in the terminal which are in turn replenished by transmitter synthesis.
The effect of baroreceptors on the latency of evoked responses in sympathetic nerves during the cardiac cycle
Authors: Fussey I. F. , Kidd C. , Whitwam J. G. 
Published: December 2014

1. A rapid increase in pressure in a vascularly isolated perfused carotid sinus has been shown to inhibit a reflex response in efferent sympathetic nerves of the dog evoked by electrical stimulation of the radial nerve.2. In intact preparations with the carotid baroreceptors innervated, the mean latency and the variance of the latency of reflex sympathetic nerve responses was reduced when the stimuli evoking the responses were applied at one point of both cardiac and respiratory cycles. When the baroreceptors were denervated there were no significant differences in the responses to random and synchronized stimuli.3. In intact preparations the latency of evoked responses in sympathetic nerves was found to vary progressively during a cardiac cycle; the maximum increase in latency was observed with the responses that occurred at that phase of the cardiac cycle when the baroreceptors exert maximal inhibition on spontaneous sympathetic activity. After denervation of the carotid sinuses a much smaller change during the cardiac cycle was still present, possibly due to effects produced by baroreceptors of the aortic arch and elsewhere.4. It was concluded that changes in baroreceptor activity, due to beat to beat fluctuations of the systemic arterial pressure are a major factor causing variations in the latency of responses in sympathetic nerves evoked by stimuli applied to a cutaneous nerve.
The effect of amiloride on sodium and potassium fluxes in red cells
Authors: Aceves Jorge , Cereijido Marcelino 
Published: December 2014

1. The effect of amiloride on the influx and efflux of 24Na and 42K in red cells was studied. The drug was added to the bathing Ringer or else incorporated in resealed ghosts.2. Amiloride does not inhibit the active or the passive (ouabain insensitive) extrusion of 24Na.3. Amiloride inhibits the influx of 24Na into red cells by 70%.4. Whether added to the inside or to the outside of the cells amiloride has no effect on the efflux of 42K.5. Amiloride does not modify the uptake of 42K from control Ringer. This uptake is strongly inhibited by the removal of Na. Amiloride has no effect on the extent of this inhibition.6. It is concluded that amiloride specifically inhibits the passive penetration of Na, and has no effect on the Na‐K‐pumping mechanism. However, at the concentration which inhibits 70% of the influx, amiloride fails to produce an observable effect on the ouabain‐insensitive Na‐efflux.7. On the basis that the information obtained could be extrapolated to other membranes, the effect of amiloride on epithelial membranes is discussed.
Contour‐like phosphenes from electrical stimulation of the human eye: some new observations
Authors: Carpenter R. H. S. 
Published: December 2014

1. The contour‐like phosphenes that may be seen with electrical stimulation of the human eye are described.2. It is found that a moving edge is particularly effective in generating these patterns.3. The relation between the velocity of the edge, the frequency of the current and the resultant spatial frequency of the lines is as if one line were generated at the edge for every cycle of the current.4. The temperature‐dependence of the phase‐shift between phosphene and current is such as would be expected if the light was delayed by some 30 msec relative to the current at the site of interaction.5. Evidence is brought forward suggesting that this phenomenon is the result not of interference‐like processes, but of coupling interactions of the retinal neurones, dividing the population into domains responding in opposite phase to the electrical stimulation.
Changes in the statistics of transmitter release during facilitation
Authors: Zucker Robert S. 
Published: December 2014

1. The statistical nature of transmitter release during facilitation was studied at single synaptic sites by recording extracellular excitatory junctional potentials from the claw opener muscle in crayfish.2. At low temperatures, single quanta could be counted in the responses to nerve impulses. The distribution of the number of quanta observed (x) was most accurately described by assuming that x is a binomial random variable.3. A quantitative estimate was made of the effects of errors in counting quanta due to the simultaneous release of quanta and the release of quanta which were not individually detectable above the noise of the recording system. Such errors of observation cannot account for the deviation of quantal release from a Poisson distribution.4. Facilitated release occurred in the responses to the second of two closely following nerve impulses and in the responses to successive impulses in a tetanus. In both cases, the increase in the average number of quanta released (m) could be attributed entirely to an increase in the probability (p) that available quanta were released.5. The results can be interpreted most easily in terms of a model in which the maximum number of releasable quanta is limited by a finite number of discrete release sites within recording distance of the microelectrode. In this model, the binomial parameter n is an estimate of the number of these sites, and the statistical parameter p is a compound probability depending on the rate of re‐occupying sites after a nerve discharge and the probability that an impulse activates an occupied site.
Relationship between tubular net sodium reabsorption and peritubular potassium uptake in the perfused Necturus kidney
Authors: Giebisch G. , Sullivan L. P. , Whittembury G. 
Published: December 2014

1. K influx from peritubular space into renal tubular cells, ϕiK, was measured in doubly perfused Necturus kidneys by studying tissue uptake of 42K added exclusively to the portal circulation. Concomitantly, net tubular Na reabsorption, ϕnNa, was measured by clearance techniques. ϕnNa and ϕiK were varied widely by replacing solutions of physiological composition (controls) with solutions containing high K, low K, low Na, cyclamate instead of Cl, ouabain (10−7‐10−4
M) or ethacrynic acid (10−5‐10−4
M).2. The ratio of ϕnNa to ϕiK was found to vary with the experimental conditions, the control value of about 2 was maintained over a threefold variation in absolute Na reabsorption. This ratio increased with low K or ouabain to values near 4. With high K, ethacrynic acid, low Na or cyclamate the relationship was one or lower. Thus, net Na reabsorption can be uncoupled from peritubular K influx.3. These results can be best explained if there are two Na pumps working in parallel: pump A transporting Na (with Cl) and pump B, a Na‐for‐K‐exchange pump. The ratio of Na efflux to K influx could approach ∞ if only pump A works (if B is inhibited) and could approach one if only B works. It should vary between these limits in controls when both pumps are active, or when neither of the two pumps is completely inhibited.4. Alternatively, the experimental findings could be explained by a Na pump with a coupling ratio that varies within two extreme values, from high Na‐K ratios (with Na reabsorption at, or near, control values but with very low K influx values) to low ratios (with normal K influx values but with low Na reabsorption values).
Spinal interneurones involved in presynaptic controls of supraspinal origin†
Authors: Besson J. M. , Rivot J. P. 
Published: December 2014

1. Interneurones presenting heterotopic and heterosensory convergence have been identified in laminae VI–VII of the lumbar dorsal horn in the cat. Stimulation of the hind limbs sometimes induced a bimodal response, but we considered only the late convergent discharge.2. The fact that response latencies are longer to hind limb than to forelimb stimulation at this level suggests the intervention of a supraspinal loop in the activation of spinal convergent units. This hypothesis is supported by the relationship between the excitability of supraspinal structures and the discharge intensity of convergent cells as well as by the absence of long latency responses in the spinal preparation.3. Electrophysiological and pharmacological evidence discloses a strong relationship between convergent unit discharges and the occurrence of dorsal root potentials to cortical, heterosegmental and heterosensory stimulation.4. It is suggested that convergent units receive information of supraspinal origin and exert control over sensory input to the cord via primary afferent depolarization.
The muscle spindles in slow and twitch skeletal muscle of the lizard
Authors: Proske U. 
Published: December 2014

1. Responses from stretch receptors, identified as muscle spindles, were recorded in filaments of the nerve supplying a twitch muscle, semimembranosus, and a slow muscle, semitendinosus in the lizard Tiliqua.2. While recording afferent discharges in one filament of the motor nerve, several adjacent filaments were each in turn stimulated repetitively until one was encountered which on stimulation produced a powerful increase in spindle firing. Such an effect of the motor stimulus was interpreted as resulting from intrafusal contraction. Any interference with spindle firing patterns from extrafusal contraction produced by the motor stimulation was removed by differentially blocking the contraction with the drug curare.3. Discharge patterns of spindles in response to a slow stretch of the muscle were compared with the response to the same stretch, but during repetitive stimulation of the motor nerve filament which produced an intrafusal contraction.4. At the initial length, the firing rate of spindles in the twitch muscle was greatly increased by the motor tetanus. There was little further increase in the response during and following stretch of the muscle.5. While the spindles in the slow muscle were only moderately excited by the motor tetanus at the initial length of the muscle, a large increase was recorded during the dynamic component of the stretch. At the new length, the steady‐state firing continued at a rate well above that for the initial length.6. The effect of the motor tetanus on the response to stretch of muscle spindles in the slow muscle could be mimicked by adding succinyl choline (5 μg/ml.) to the perfusion solution. Spindles in the twitch muscle did not show a sustained sensitivity to the drug.7. It is suggested that while the different effects of motor stimulation on the responses to stretch of spindles in slow and twitch muscle can be explained by propositions based on the sliding filament theory of contraction, the sustained elevation, at the new length, of firing frequencies of spindles in slow muscle might require an additional explanation.
The effect of exercise on lactate metabolism
Authors: Hubbard Judith L. 
Published: December 2014

1. An
I.V. injection of 5 μc [U‐14C]sodium
L(+)‐lactate was given to four subjects at rest and again 10 min after beginning a 40–50 min period of heavy exercise at an estimated 62–72% of their maximum aerobic power (V̇O2 max.). Both blood lactate concentration and V̇O2 remained relatively constant after the first few minutes of exercise.2. In all subjects both at rest and during exercise blood lactate and total radioactivity were measured at frequent intervals after injection of [14C]lactate. Timed expired gas collections were made and the quantity of 14CO2 present in each collection measured. In two subjects the specific activity of lactate and of glucose isolated from blood was also measured.3. It was found that during 30 min of exercise 35–68% of the administered [14C]lactate was recovered as 14CO2 in the expired gas, whereas at rest only 3–7% was recovered in the same period.4. After injection of [14C]lactate the blood 14C concentration and the specific activity of the blood lactate declined very rapidly. This decline was more rapid during exercise than at rest.5. In the two subjects in whom it was measured the specific activity of blood glucose was lower during exercise than at rest.6. These results show that both at rest and during heavy exercise, lactate is removed from the blood and metabolized, and that during exercise this metabolism is much more rapid.7. In the light of these findings the sustained blood lactate concentration observed in these experiments is regarded as representing a dynamic equilibrium between the production and metabolism of lactate during exercise. The results give no support to the hypothesis that lactate is produced only during the first few minutes of submaximal work.
The permeation of human red cells by 4, 6‐O‐ethylidene‐α‐D‐glucopyranose (ethylidene glucose)
Authors: Baker G. F. , Widdas W. F. 
Published: December 2014

1. The glucose derivative 4, 6‐O‐ethylidene‐α‐
D‐glucopyranose (ethylidene glucose) was found to inhibit glucose exit competitively but its penetration into human red cells was unaffected by glucose in the medium.2. In penetrating red cells ethylidene glucose followed diffusion type kinetics without any evidence of saturation up to 360 m
M. Besides its penetration being unaffected by glucose, 10−5
M phloretin, which powerfully inhibits the facilitated transfer of hexoses, did not inhibit penetration.3. Red cells incubated with 1‐fluoro‐2, 4‐dinitrobenzene (FDNB) until glucose exit was reduced by 95% showed no slowing of penetration by ethylidene glucose.4. The potentiation of the development of FDNB inhibition by sugars in the incubating medium was absent when ethylidene glucose was used and there was a slight protective action. Cells pre‐incubated with 76 m
M ethylidene glucose did not show an uphill transfer from 4 m
M‐[14C]glucose in the outside medium in contrast to cells pre‐incubated in 76 m
M glucose or in 76 m
M 3‐O‐methyl glucose.5. The possibility that ethylidene glucose penetrated human red cells by simple diffusion was supported by its penetration of guinea‐pig red cells at similar rates, by the occurrence of osmotic haemolysis in isosmotic solutions which was unaffected by copper ions and by the relatively high ether/water partition of the compound.
The effects of heating and cooling the spinal cord and hypothalamus on thermoregulatory behaviour in the pig
Authors: Carlisle H. J. , Ingram D. L. 
Published: December 2014

1. The effects of warming and cooling the spinal cord and hypothalamus on operant thermoregulatory behaviour and posture have been studied in the pig at neutral and cold ambient temperatures.2. Cooling the spinal cord increased and warming decreased the rate of obtaining thermal reinforcement. The response to cooling began with the onset of the stimulus and persisted for up to 5 min followed by a diminution in rate during the remaining 15 min of cooling. The peak of this ‘on’ response was greater the lower the ambient temperature. The response to heating was a small reduction in rate of reinforcement.3. The ‘on’ response to cooling the spinal cord was related to changes in temperature of only the cervical region of the cord.4. Cooling the hypothalamus led to an increase in the rate of obtaining heat and this increase was sustained during the 20 min of central cooling. Termination of cooling was followed by a marked depression in rate. Heating the hypothalamus had only a weak inhibitory effect on rate of reinforcement.5. While working for external heat during periods when thermodes over the spine and in the hypothalamus were not being cooled, pigs lay in ‘cold defensive’ prone positions 25% of the time and lay on their sides 75% of the time. During cooling of the spinal cord the time spent in the prone position was 95% at 5 and 15° C ambients and 71% at a 25° C ambient. During cooling of the hypothalamus the prone posture was adopted 50% of the time.6. When the temperatures of the spinal cord and of the hypothalamus were changed in opposite directions, the operant response was determined by the temperature of the hypothalamus while the postural response was most frequently determined by the temperature of the spinal cord.
Effects of manganese and other agents on the calcium uptake that follows depolarization of squid axons
Authors: Baker P. F. , Meves H. , Ridgway E. B. 
Published: December 2014

1. The Ca‐sensitive photoprotein aequorin was injected into squid axons and the light response to stimulation or depolarizing voltage clamp pulses recorded.2. The effects of Mn2+, Co2+, Ni2+, La3+ and of the organic Ca antagonists D‐600 and iproveratril on the early tetrodotoxin‐sensitive and late tetrodotoxin‐insensitive components of the light response were studied.3. The late tetrodotoxin‐insensitive component can be blocked, reversibly, by concentrations of Mn, Co and Ni that reduce but do not block the tetrodotoxin‐sensitive component. The late component can also be blocked by La3+ and the organic Ca antagonists D‐600 and iproveratril.4. Mn2+, Co2+, Ni2+ and the drug D‐600 all reduce the Na currents, but have little effect on either outward or inward K currents. Tetraethylammonium blocks the outward K current but has no appreciable effect on the tetrodotoxin‐insensitive entry of Ca.5. Concentrations of Mn between 5 and 50 m
M substantially reduce the light output during a train of action potentials; they also slightly reduce the rate of rise of the action potential.6. On pharmacological grounds it is concluded that the tetrodotoxin‐insensitive component of Ca entry does not represent Ca ions passing through the K permeability channels. There must exist a potential‐dependent late Ca channel that is distinct from the well known Na and K channels of the action potential. A possible function for this late Ca channel in the coupling of excitation to secretion is discussed.
Effects of manganese on the electrical and mechanical properties of frog skeletal muscle fibres
Authors: Chiarandini D. J. , Stefani E. 
Published: December 2014

1. The effects of Mn on the electrical and mechanical properties of frog muscle fibres have been studied.2. In normal saline 10 or 20 m
M‐Mn hyperpolarized the fibres and had no effect on the membrane resistance. In isotonic K2SO4 saline, Mn increased the membrane resistance indicating that this agent reduced the conductance to K.3. The action potential is prolonged by Mn while the overshoot amplitude is unaffected. The threshold of the action potential is shifted to more positive values of membrane potential.4. The isometric twitch is reduced by 45% in 10 m
M‐Mn; this effect is observed within 8 sec of the application.5. Mn (10 m
M) reduced K contractures induced by 40 or 75 m
M‐K (constant [K].[Cl] product) and shifted to the right in a parallel manner the curve tension vs. log K concentration. The calculated mechanical threshold for K contractures was shifted from −48 to −33 mV.6. Caffeine contractures (3–4 m
M) and supramaximal K contractures (190 m
M‐K) were unaffected by 10 m
M indicating that contractile proteins and the ability of the sarcoplasmic reticulum to release Ca are not impaired.7. It is concluded that Mn is mainly affecting the excitation‐contraction coupling by altering the mechanical threshold. Since Mn reduces the permeability to Ca in several excitable membranes, it is suggested that the mechanical threshold depends on the entry of Ca to the muscle.
Effect of activation of α and β adrenergic receptors on the hepatic cell membrane potential in perfused dog liver
Authors: Lambotte L. 
Published: December 2014

1. The effect of stimulation of hepatic α‐ and β‐sympathetic receptors on the membrane potential of liver cells was studied utilizing the isolated perfused dog liver. In this preparation, potentials are maintained close to their normal values (around −50 mV) for several hours.2. The administration of adrenaline (0·5 μ
M) caused an immediate depolarization, which reached 23 mV in 2 min. The potential gradually returned to base line levels in less than 20 min. A slight hyperpolarization often followed, despite a fall in the K content of the tissues. Similar results could be obtained with a lower concentration (0·1 μ
M) of adrenaline.3. Potential changes after adrenaline injection are not altered by prior inhibition of the Na pump by ouabain. The adrenaline induced depolarization may be attributed to an increase in PNa and the repolarization to a decrease in PNa. An electrogenic mechanism does not seem to be involved.4. Administration of the β‐sympathomimetic agent isoprenaline (1 μ
M) is followed by hyperpolarization, the potential increasing from −45·7 ± 1·5 to −55·0 ± 2·7 mV. Isoprenaline also slows the potential drop produced by ouabain. The action of isoprenaline may be explained by a reduction in permeability to Na.5. Adrenaline also produces hyperpolarization in the presence of an α‐blocking agent, phenoxybenzamine. In the presence of a β‐blocking agent, propranolol, it causes more prolonged depolarization.6. In the dog, the effect of α‐stimulation appears to be a rapid increase in permeability to Na, producing depolarization and of Na for K exchange. Stimulation of β‐receptors results in a slower decrease in PNa and hyperpolarization. The combination of these two effects could explain the depolarization followed by repolarization produced by adrenaline.
Neurones in the dorsal horn of the rat responding to scrotal skin temperature changes
Authors: Hellon R. F. , Misra N. K. 
Published: December 2014

1. Micro‐electrode recordings have been made from single neurones in the dorsal horn of male rats anaesthetized with urethane. Scrotal temperature was altered within the range 13–43° C by means of a thermode. The mean firing rate of neurones was correlated with step and ramp changes of temperature.2. In the region where the scrotal nerve enters the cord, 47% of the neurones were responsive to scrotal temperature: half were excited by warming and half by cooling. Most of these thermally responding units were not affected when the scrotal skin was touched and only one‐fifth responded to both modalities.3. Both the ‘warm’ and ‘cold’ groups of neurones showed responses to step changes of temperature which were classified as dynamic plus static, dynamic only or static only. Comparison of these responses with those published for the scrotal thermoreceptors showed that the incoming thermal information was being processed in the dorsal horn.4. Histological examination of the cord showed that recording sites were in laminae I to V of the dorsal horn.