bluuebunny/crossref_metadata_2025 huggingface dataset:
The connexion between the ion‐binding sites of the sodium pump.
Authors: Chipperfield A R , Whittam R
Published: December 2014

1. A study has been made of K influx into human red blood cells in order to determine the influence of internal Na on the affinity of the Na pump for external K. Cells were prepared to contain minimal K and two Na concentrations (about 10 and 30 mueqiv/ml. cells) and incubated in solutions with a range of K concentrations. 2. In choline (Na‐free) Ringer, activation of K influx by external K was hyperbolic. The Km for external K increased as the internal Na concentration was raised. The increase was greater than the increase in K influx with saturating external K. The Km for external K increased towards a limiting value as the internal Na concentration was raised. 3. In contrast, in Na‐Ringer, the activation by external K was sigmoidal and the affinity for external K was independent of the internal Na concentration. 4. K influx was measured at two submaximal levels of external K with a range of internal Na. The affinity for internal Na fell as external K was raised. 5. The results suggest that in the absence of competition between Na and K on the same side of the membrane, there is a connexion between the ion‐binding sites of the Na pump.
The interaction between cutaneous and spinal therman inputs in the control of oxygen consumption in the rat.
Authors: Banet M , Hensel H
Published: December 2014

1. The effect of thermal stimulation of the spinal cord on the rate of oxygen consumption was studied in five unanaesthetized rats during exposure to various ambient temperatures. 2. In a warm environment, cooling the spinal cord had no effect on the rate of oxygen consumption but in thermoneutral and cold environments the rate of oxygen consumption increased proportionally to the intensity of spinal cooling. Heating the spinal cord decreased the level of oxygen consumption and, if intense enough, suppressed the thermoregulatory increase in metabolic rate. 3. It is concluded that, in the control of oxygen consumption in the rat, the afferent signals from thermal sensors in the spinal cord and skin are added.
The role of some small peptides in the transfer of amino nitrogen across the wall of vascularly perfused intestine.
Authors: Cheeseman C I , Parsons D S
Published: December 2014

The characteristics have been investigated of the transfer into the vascular bed of L‐leucine and glycine from free amino acids or peptides in the intestinal lumen of Rana pipiens. Over the concentration range 0‐5‐10 mM the transfer of L‐leucine is but little affected by the presence of equimolar concentrations of glycine but the transfer of glycine, in contrast, is greatly inhibited by the presence of L‐leucine. 2. With glycyl‐L‐leucine in the intestinal lumen, the rate of transfer of glycine into the vascular bed is much greater than from the mixture of the two amino acids and is equal to that of the L‐leucine. From L‐leucyl‐glycine the rates of transfer of leucine and of glycine are also higher than from the mixture of the two amino acids but the rate of transfer of glycine is somewhat lower than that of leucine. There is no evidence of the presence of the dipeptides in the effluent from the portal vein. 3. When the peptide glycyl‐L‐leucine is added to the lumen in the presence of 10 mM concentrations of the free amino acids, additional amounts of L‐leucine and of glycine are transferred in approximately equimolar quantities into the vascular bed. This additional transfer exhibits saturation with respect to concentration of peptide in the intestinal lumen. An additional transfer of amino acids was also found when L‐leucyl‐glycine was added to the lumen in the presence of saturating concentrations of the two amino acids. 4. Evidence is presented that the presence of the dipeptides in the intestinal lumen had little effect on the transfer of free amino acids from the lumen into the vascular bed. Although the transfer of free amino acids from the lumen into the vascular bed is significantly, but not completely, abolished when the Na in the intestinal lumen is replaced by K, the transfer of the amino acids from the dipeptides is but little affected. 5. The findings are discussed in relation to the view that the dipeptides are transported into the mucosal epithelium by a process that is distinct from those promoting uptake of the individual amino acids. Being completely hydrolysed, there is no evidence for an accumulative uptake of the peptides; it is suggested that this may be related to the fact that the peptide uptake occurs in the absence of Na in the intestinal lumen.
The relation between intercellular coupling and electrical noise in turtle photoreceptors.
Authors: Lamb T D , Simon E J
Published: December 2014

1. Intracellular recordings from cones and rods in the retina of the turtle, Pseudemys scripta elegans, revealed that in darkness the cell voltage fluctuated spontaneously about its mean level. The fluctuations were reduced during bright steady illmination of the cell often to a level close to that obtained with the electrode outside the cell where the noise did not change significantly during illumination. 2. The magnitude of the intrinsic dark noise (voltage variance in darkness minus voltage variance in strong light) varied widely from cell to cell. In the noisiest cones it was about 0‐4 mV2 while in quiet cones it was often as low as 0‐01 mV2. The noise appeared radom and could be fitted by a Gaussian probability density function. 3. The spread of voltage in the network of coupled photoreceptors was estimated by measuring the spatial profile of the response to a brief flash of constant intensity moved across the retina. For a light stimulus in the form of a long narrow slit, the peak flash response usually decayed exponentially with displacement from the centred position. 4. For maximum responses less than about 5 mV in cones, the length constant of exponential decay, lambda, varied from less than 10 mum to greater than 35 mum, and the values obtained in opposite directions were often unequal. Background illumination did not significantly change lambda. In cells with extremely narrow spatial profiles, an exponential fit to the decay could not be made reliably. 5. Occasionally the spatial profiles had definite secondary peaks. In the most pronounced examples in a red‐sensitive cone and in a rod the maxima were separated by about 20 and 50 mum respectively; for each, one peak was approximately as sharp as the optical stimulator while the second was broader. 6. Cones with short length constants displayed high dark noise while cones with long length constants were relatively quiet. 7. Three models of electrical coupling between cells were investigated: one based on a distributed network, one on a discrete square grid arrangement, and one on a discrete hexagonal array. Each model predicts a strong dependence of both noise and input resistance on length constant, and for tightly coupled cells each predicts that voltage variance is proportional to lambda‐2. 8. The measured relationship between voltage variance and lambda in a large sample of cones was well described by both discrete models when the average cell spacing was taken to be approximately 15 mum. 9...
On the analysis of nerve signals deduced from metacontrast experiments with human observers.
Authors: Wandell B A
Published: December 2014

1. This paper reviews Alpern, Rushton & Torii's (1970a‐d) derivation of the size of the inhibitory nerve signal arising from after flashes in the metacontrast experiment. 2. Their geometric argument is recast in terms of simple functional equations. This form of argument clearly displays the role of their assumptions in obtaining their main conclusion: nerve signal is linear in intensity over a range of 3‐4 log units. 3. Two disadvantages of their approach are discussed. First, it is noted that in the presence of the data the assumption they employ in their analysis is logically equivalent to their conclusion. 4. Secondly, accepting their claim that the nerve signal generated by the after flash is linear over a broad range of intensities, and that this inhibitory signal simply cancels the excitatory signal of the test flash, leads to the conslusion that over this same intensity range the excitatory nerve signal is a power function with an exponent of close to two. This is incompatible with the suggestion that photoreceptor signals have been measured.
Action potentials in the rat chromaffin cell and effects of acetylcholine.
Authors: Brandt B L , Hagiwara S , Kidokoro Y , Miyazaki S
Published: December 2014

1. Electrophysiological properties of the rat chromaffin cell were studied using intracellular recording techniques. 2. The resting potential in the chromaffin cell was ‐49 +/‐ 6 mV (mean +/‐ S.D., n = 14) in standard saline containing 10 mM‐Ca whereas that in Na‐free saline was ‐63 +/‐ 9 mV (n = 17). At rest, the membrane has a substantial Na permeability. 3. Action potentials were evoked by passing current through the recording electrode. In standard saline the major fraction of the action potential disappeared either upon omission of external Na ions from standard saline or addition of 1 muM tetrodotoxin (TTX). We conclude that action potentials in the chromaffin cell are due mainly to an increase in the permeability of the membrane to Na ions. 4. Small but significant regenerative action potentials were observed in Na‐free saline, and when Ca in Na‐free saline was replaced by Ba, prolonged action potentials occurred. We conclude that action potentials in the chromaffin cell also have a Ca component. 5. Iontophoretic application of acetylcholine (ACh) produced a transient membrane depolarization in standard saline. 6. Spontaneous action potentials were recorded extracellularly by microsuction electrodes. They occurred at a rate of 0‐05‐0‐1/sec in almost all cells. 7. When the perfusion fluid contained 3 x 10(‐7) M to 10(‐4) M ACh the spike frequency increased up to about 2/sec. This stimulatory effect of ACh was blocked by 10(‐7) M atropine but not by 10(‐3) M hexamethonium nor by 10(‐5) M‐d‐tubocurarine. 8. The importance of Ca entry during action potentials for catecholamine secretion is discussed
A large birefringence signal preceding contraction in single twitch fibres of the frog.
Authors: Baylor S M , Oetliker H
Published: December 2014

1. When a single muscle fibre was externally stimulated to give a propagated action potential, a large decrease in light intensity was measured with the fibre positioned between crossed‐polarizers oriented at +/‐ 45 degrees with respect to the fibre axis. This large optical signal begins just after stimulation and its man phase precedes the development of positive tension. 2. The peak (or plateau) amplitude of the signal, expressed as the peak (plateau) change in light intensity, delta I, divided by the resting light intensity, I, was typically (minus) 1 to 3x10‐3 and the time‐to‐peak (plateau) was 4 to 6 ms (20 degrees C). 3. When mechanical activity was minimized by stretch or Ringer replacement with D2O or hypertonic solution, the peak tension response was reduced in far greater proportion than the peak optical response, suggesting that the early optical signal is not due to changes in tension or gross fibre movement. 4. The magnitude of the optical response was increased by nitrate and double‐shock stimulatin, procedures which potentiate the twitch response. 5. The optical signal was shown to propagate along the fibre length with a conduction velocity appropriate to the surface action potential. 6. The above results suggest that the large, early birefringence signal reflects a step or steps in the sequence of events leading to contractile activation.
Control of dynamic and static nuclear bag fibres and nuclear chain fibres by gamma and beta axons in isolated cat muscle spindels.
Authors: Boyd I A , Gladden M H , McWilliam P N , Ward J
Published: December 2014

1. The behaviour of nuclear bag and nuclear chain intrafusal fibres in isolated cat muscle spindles with a blood supply, during stimulation of dynamic gamma axons, dynamic beta axons, or static gamma axons in ventral root filaments was observed and recorded on still and moving film. 2. Most spindles were controlled by one dynamic gamma axon (sometimes a beta axon) and three static gamma axons, one of which was often non‐selective in distribution. A large majority of fusimotor axons controlled one pole of the spindle only. 3. Dynamic gamma and beta axons produced focal contraction in only one of the two nuclear bag fibres in any spindle and this fibre was never activated by static gamma axons. Maximal tetanic contraction was attained slowly and the primary sensory spiral on this fibre was stretched by a small amount only. This fibre has been named the 'dynamic nuclear bag fibre'. 4. Static gamma axons produced either: (a) focal contraction in the second of the two nuclear bag fibres only; (b) local contraction in the bundle of nuclear chain fibres only; or (c) contraction in one nuclear bag fibre and the nuclear chain fibres together. Maximum tetanic contraction of this nuclear bag fibre stretched its primary sensory spiral considerably and the time to plateau was relatively short. This fibre has been named the 'static nuclear bag fibre'. 5. 'Driving' of the Ia afferent discharge could always be produced by non‐selective static gamma axons, frequently by static gamma axons controlling nuclear chain fibres alone, and was probably due to mechanical oscillation in nuclear chain fibres. It was never produced by dynamic gamma axons and on one occasion only by a static gamma axon controlling a nuclear bag fibre alone. 6. The conduction velocities of dynamic gamma and static gamma axons overlapped extensively, though dynamic gamma axons were absent from the lower end, and static gamma axons innervating nuclear chain fibres only were absent from the upper end, of the range of velocities. 7. The observations are correlated with spindle structure and histochemistry. Dynamic and static nuclear bag fibres are shown to correspond with 'bag1 fibres' and 'bag2 fibres', respectively (Ovalle & Smith, 1972). 8. The possible origin of the dynamic and static actions of fusimotor axons and the role of the dynamic and static intrafusal systems in motor control are discussed.
Metabolic energy dependence of glucose, water and sodium absorption in the presence and absence of 'downhill' sodium gradients across isolated rat small intestine.
Authors: Gardner M L
Published: December 2014

1. Absorption of glucose and water was studied in isolated perfused rat small intestine with arterial infusion under normal conditions and with a 'downhill' sodium gradient across the mucosa. 2. The effects of metabolic inhibitors, iodoacetate phenformin and dinitrophenol, on absorption were determined in the presence of normal and 'downhill' sodium gradients. 3. Glucose absorption was inhibited by each inhibitor, and the inhibition was independent of the direction of the sodium gradient. 4. Net sodium flux across the mucosa was also inhibited under 'downhill' sodium gradient conditions. 5. The simultaneous and parallel inhibition of both glucose and sodium transport is consistent with, but does not prove, the sodium gradient theory.
Axon‐collateral activation by dorsal spinocerebellar tract fibres of group I relay cells of nucleus Z in the cat medulla oblongata.
Authors: Johansson H , Silfvenius H
Published: December 2014

1. The problem whether the group I hind limb cerebral tract and the dorsal spinocerebellar tract (DSCT) have common spinal axons has been investigated in the present study. 2. Thirty‐two cells located in the nucleus Z of the cat medulla oblongata and activated by spinal fibres in the dorsolateral fascicle were selected for the study. 3. Extracellular recording from these neurones demonstrated that most of them were monosynaptically linked to spinal fibres excited by ipsilateral hind limb group I muscle afferents. The cells exhibited a restricted spatial convergence and had a limited excitatory convergence from group II muscle and from skin afferents. 4. Antidromic activation from the contralateral thalamus showed that they were bulbothalamic relay cells. 5. Cerebellar surface or depth stimulation activated 88% of the twenty‐six cells tested at a short latency. With a collision technique it was demonstrated that twelve out of twenty‐three (52%) of these group I relay neurones were activated by axon‐collaterals of the DSCT. 6. 43% of the cells activated from the cerebellum, but not proven to be linked to the DSCT, could, nevertheless, have been excited by DSCT axon‐collaterals, if it is assumed that different fibres converging with excitation on the group I relay cells were activated in the collision test.
Thermoregulatory responses as a function of core temperature in humans.
Authors: Cabanac M , Massonnet B
Published: December 2014

1. Six healthy humans were immersed sequentially in baths maintained at a steady temperature of either 28 +/‐ 1 or 38‐8 +/‐ 1 degree C. 2. Metabolic heat production was calculated by respiratory gas analysis. A ventilated capsule was placed on the forehead and sweat secretion was calculated from psychrometric recordings. Convective heat loss from one hand to water‐perfused glove provided a continuous measurement of vasomotor response. 3. Heat production, sweating, and vasomotor heat loss were proportional to core temperature. 4. Sweating and vasomotor response were parallel. Vasoconstriction was complete, before the onset of shivering. 5. The thresholds for heat loss and heat production were superimposed, without a 'dead band' core temperature.
The effect of calcium injection on the intracellular sodium and pH of snail neurones.
Authors: Meech R W , Thomas R C
Published: December 2014

1. Ion‐sensitive glass micro‐electrodes were used to measure the intracellular pH (pHi) and the intracellular sodium ion concentration, [Na+]i, in identified Helix aspersa neurones. 2. The injection of small volumes of 0‐1 McaCl2, which increased the membrane potential by 10‐15 mV for 1‐2 min, had little or no effect on [Na+]i. Increases of up to 1 mM in [Na+]i could be reversibly induced by larger injections. 3. Calcium injection caused an immediate decrease in pHi, which appeared to be directly proportional to the amount of calcium injected. Injections causing hyperpolarizations of 10‐20 mV which recovered in 2‐5 min caused pHi decreases of 0‐04‐0‐15 units. After each of these injections both pHi and the membrane potential recovered exponentially but with different time constants. 4. The injection of calcium at a low rate could decrease pHi without affecting the membrane potential. 5. Neither membrane potential nor pHi were affected by the injection of small volumes of 0‐1 M‐MgCl2, Injection of CoCl2 produced a large transient decrease in pHi but no significant change in membrane potential. 6. Exposure of the cell to saline equilibrated with 2‐5% CO2 greatly reduced the pHi decrease caused by calcium injection but had only small effects on the membrane potential response. 7. It is concluded that most of the injected calcium is exchanged for protons inside the cell.
Ionic currents through the membrane of the mammalian oocyte and their comparison with those in the tunicate and sea urchin.
Authors: Okamoto H , Takahashi K , Yamashita N
Published: December 2014

1. The action potential and the membrane current of the mouse oocyte were analysed by current‐clamp and voltage‐clamp techniques and they were compared with those of other animal oocytes. 2. The matured and unfertilized oocyte of the mouse in standard medium with 6 mM‐K showed the resting potential of ‐23‐1+/‐2‐9 mV. The resting potential was relatively large in the medium with 20 mM‐Ca or 10 mM‐Mn, being ‐35‐7+/‐2‐6 mV and further increased to ‐46‐9+/‐4‐8 mV with replacement of Na in the medium by choline. 3. At the cessation of large hyperpolarization below ‐90 mV in standard medium, a regenerative potential was often elicited in the form of an off‐response. The off‐response depended upon the external concentration of Ca. In 20 mM‐Ca medium it was constantly observed with hyperpolarization below ‐60 mV. Its critical level was ‐40 mV and its overshoot was +15 mV. 4. The time and potential‐dependent inward current was observed both in standard and 20 mM‐Ca media under voltage‐clamp condition. In 20 mM‐Ca medium the inward current was observed by depolarization beyond ‐40 mV and showed its maximum at ‐15 mV. It was greatly reduced by replacing the external Ca with Mn but retained by substituting Sr or Ba for Ca. The selectivity ratios among these alkali earth cations were Ca:Sr:Ba=1‐0:1‐4:0‐7. 5. The current‐voltage relation in Ca and Na‐deficient and 10 mM‐Mn medium was linear from ‐200 to +25 mV. The hyperpolarization below ‐200 mV revealed an inward‐going rectification. The depolarization above +50 mV under voltage‐clamp condition induced the outward surge current with activation and inactivation processes. 6. In contrast to the mouse oocyte, the matured and unfertilized oocyte of the sea urchin showed a large resting potential of ‐70 mV in 30 Ca ASW and the depolarization beyond ‐40 mV elicited an action potential with an overshoot of 20 mV. The action potential showed a notch in the rising phase and lasted about 1 to 2 sec. 7. Under the voltage‐clamp condition both Ca inward current and the outward surge current were observed in the sea urchin oocyte membrane just as in the mouse oocyte membrane. 8. The selectivity ratios among alkali earth cations, Ca:Sr:Ba, for 'Ca channels' of the oocyte membranes were 1‐0:1‐4:0‐7 in the mouse, 1‐0:1‐7:1‐1 in the tunicate and 1‐0:0‐7:0‐5 in the sea urchin. When the current density through Ca channels are revised in terms of the respective critical levels for Ca channels, the revised selectivity sequences become Ca greater than Sr greater than Ba, being common to all three species.
Appearance of new acetylcholine receptors on the baby chick biventer cervicis and denervated rat diaphragm muscles after blockade with α‐bungarotoxin
Authors: Chang C. Chiung , Su M. Jai , Tung L. Hsien
Published: December 2014

1. The recovery of contractile responses and appearance of new α‐bungarotoxin‐binding sites were studied in the baby chick biventer cervicis and the rat diaphragm muscles after saturating the existing acetylcholine (ACh) receptors (AChR) with α‐bungarotoxin in vitro.

2. Washout of α‐bungarotoxin restored gradually the response to exogenous ACh attaining about 30% recovery in 3 hr either in the chick muscle or in the denervated rat diaphragm. No recovery was obtained, however, for the response to nerve stimulation.

3. The recovery of ACh‐response was abolished by decreasing the bath temperature to 9° C during the washout of the toxin whereas the recovery was not reduced in the presence of cycloheximide.

4. The half‐life of [3H]acetyl α‐bungarotoxin bound specifically on the existing AChRs, junctional and extrajunctional receptors combined, was 16 hr in the chick muscle. That on the extrajunctional AChR was estimated to be 8 hr.

5. New toxin‐binding sites were found to be incorporated on the membrane of extrajunctional site rapidly after treatment with α‐bungarotoxin in the chick and the denervated rat muscles along the muscle fibres but not in the innervated rat diaphragm. Treatment with (+)‐tubocurarine, ACh or decamethonium did not cause an appreciable increase of the toxin‐binding sites.

6. The appearance of new binding sites was progressive during 5 hr at a rate of 24 sites/μm2.hr in the chick muscle and 42 sites/μm2.hr in the rat diaphragm denervated for 7 days. The existing extrajunctional AChR were about 50/μm2 and 192/μm2, respectively.

7. ACh effectively antagonized the binding of α‐bungarotoxin with the new sites whereas (+)‐tubocurarine was less effective than its effect on the existing AChR.

8. The new toxin‐binding sites appeared to have a reduced capacity to evoke ACh response.

9. The incorporation of new binding sites was reduced by lowering of the temperature, treatment with dinitrophenol, high K+, high Ca2+ and by the stimulation of either nerve or muscle. Cycloheximide, ACh, decrease of [Na+]o and increase of [Mg2+]o were without effect.

10. It is suggested that binding of the extrajunctional AChRs with α‐bungarotoxin cause a change of membrane architecture and trigger the incorporation of cytoplasmic AChR‐precursor or hidden AChR into the membrane.
Regenerative repolarization of the frog ventricular action potential: a time and voltage‐dependent phenomenon.
Authors: Goldman Y , Morad M
Published: December 2014

1. The regenerative repolarization process has been examined in frog ventricular myocardium using a single sucrose gap voltage clamp technique. 2. Application of brief (30‐150 msec) anodal voltage clamp pulses during the plateau of the action potential revealed a 'threshold' potential region for immediate repolarization. The response to anodal clamp pulses was not all‐or‐none but was graded. 3. The threshold potential was strongly dependent on the duration of the test voltage clamp pulses and was more negative for shorter clamps. 4. Regenerative repolarization was also observed in the presence of tetrodotoxin. 5. No threshold for immediate repolarization was observed with very short clamps (2‐20 msec in duration). Instead the membrane depolarized upon release of each clamp pulse. 6. Theoretical showed that the de‐ and repolarizations observed after test clamp steps are not due to geometrical properties or inhomogeneous potential distributions. 7. The results suggest that the instantaneous I‐V relation of the membrane during the plateau may be linear.
Effect of anoxia and ATP depletion on the membrane potential and permeability of dog liver.
Authors: Lambotte L
Published: December 2014

1. The mechanisms responsible for the depolarization of the hepatocytes secondary to anoxia have been studied in isolated perfused dog liver. It was attempted to elucidate the role of the inhibition of the sodium pump following exhaustion of the energy reserves and of the modifications of membrane permeability. Anoxia was compared to ouabain and to a reduction of the cellular ATP level. 2. Membrane potentials were measured with micro‐electrodes. Potassium, sodium and chloride were determined in plasma samples and liver tissues. Extracellular space was measured with tritiated inulin or with an electrical impedance method. Adenine nucleotides were also measured in liver biopsies. 3. The fall in membrane potential produced by administration of ouabain (0‐1 mM) is greater than the effect of the redistribution of sodium + potassium ions; this suggests that the sodium pump is functioning, at least partially, electrogenically. The administration of dinitrophenol (10 mM), which causes a 74% fall in the ATP level in 15 min, produces, as does ouabain, a depolarization which also corresponds to stopping an electrogenic pump. 4. A partial reduction in the level of ATP brought about by hypoxia, by an inhibitor of cellular respiration, antimycin (10 mM), or by fructose (20 mM) results in a hyperpolarization which may be attributed to an elevation of potassium permeability (PK) since it is concomitant to a loss of K from the liver. The change in membrane permeability could be related to a rise in the free calcium in the cells which has not been documented. Other possible hypothesis include a facilitated transport for potassium. 5. The administration of amobarbitone (10 mM) produces immediately a depolarization which is independent of the progressive reduction in the level of ATP. The depolarization has been attributed to a direct effect of amobarbitone on the membrane reducing the permeability for potassium ions. 6. The depolarization observed in ischaemic anoxia is greater than that produced by ouabain for the same variation in ions concentration. In addition to a likely inhibition of the electrogenic sodium pump, changes in membrane permeability inducing a rise in the PNa/PK ratio must also occur. 7. After ischaemic anoxia for 24 hr at 3 degrees C, the ratio of PNa/PK rises to 0‐68 which indicates abolishment of the selective character of membrane permeability. The augmentation in cell volume produced by anoxia might result in an opening of membrane pores, which could entail the augmentation of sodium permeability; the latter would be responsible in part for the depolarization produced by anoxia. 8. According to the severity and length of oxygen deprivation an increase in PK, a cessation of the sodium pump activity and finally an increase in PNa will occur.
Comparison of the effect of somatostatin on gastrointestinal function in the conscious and anaesthetized cat and on the isolated cat pancreas.
Authors: Albinus M , Blair E L , Case R M , Coy D H , Gomez-Pan A , Hirst B H , Reed J D , Schally A V , Shaw B , Smith P A , Smy J R
Published: December 2014

1. Somatostatin, 10 microgram kg‐1 hr‐1, inhibited gastric acid and pepsin secretion stimulated by pentagastrin, 8 microgram kg‐1 hr‐1, in conscious and anaesthetized cats with chronically implanted gastric fistulae. In the acutely surgically prepared anaesthetized cat, Somatostatin inhibited pepsin secretion but produced little inhibition of gastric acid secretion or mucosal blood flow. 2. Secretin stimulated pancreatic juice volume was not significantly reduced in acutely prepared anaesthetized cats, but there was a limited reduction of cholecystokinin‐pancreozymin stimulated pancreatic amylase secretion and gall bladder contraction. 3. Somatostatin had neither stimulatory nor inhibitory effects on electrolyte and amylase secretion in the isolated saline‐perfused cat pancreas. 4. The results suggest that some of the effects of Somatostatin may depend on the interaction on the target cell of other factors, nervous or humoral which may vary in different experimental preparations.
Responses of identified spinal neurones to acetylcholine applied by micro‐electrophoresis.
Authors: Myslinski N R , Randić M
Published: December 2014

1. The responses of identified cells in the cat Clarke's column and dorsal horn to micro‐electrophoretically applied cholinomimetics and anti‐cholinergic substances have been investigated. 2. Both antidromically identified (DSCT neurones) and synaptically activated neurones from the region of the Clarke's column of the spinal cord were excited by ACh. However, the proportion of ACh excited cells was greater in units synaptically activated by ipsilateral dorsolateral funiculus stimulation (78%) than in DSCT neurones (50%). In addition, about 55% of neurones activated either antidromically or synaptically by ipsilateral dorsal column stimulation were excited by ACh. 3. In contrast to a relatively weak excitatory potency on the DSCT neurones (maximum firing frequency did not exceed 130% of the control activated by ipsilateral dorsolateral funiculus stimulation (maximum firing frequency reached 430% of the control level). 4. ACh has a relatively quick and rapidly reversible excitatory effect on Clarke's column neurones and some types of dorsal horn interneurones, which can be obtained also with nicotine. However, the action of nicotine is frequently delayed in onset and recovery. This excitatory action of ACh can be blocked or markedly depressed by dihydro‐beta‐erythroidine. These results and those obtained with acetyl‐beta‐methylcholine and atropine seem to suggest that the receptors mediating excitation of the cholinoceptive spinal cells activated either antidromically or synaptically by ipsilateral dorsolateral funiculus stimulation besides predominantly nicotinic have also weak muscarinic properties. 5. Desensitization with repeated applications of ACh and nicotine has been observed in both DSCT neurones and units antidromically activated by ipsilateral dorsal column stimulation. 6. About 11% of units antidromically activated by ipsilateral dorsolateral funiculus stimulation were depressed by ACh. In addition, the depressant effect of ACh was more frequently encountered in the cells unresponsive either to the dorsolateral funiculus or dorsal column stimulation. ACh depression was also seen in units activated either antidromically or synaptically by ipsilateral dorsal column stimulation. In contrast, none of the units synaptically activated by the ipsilateral dorsolateral funiculus stimulation were depressed by ACh. The same was true for spinal neurones receiving convergent peripheral inputs activated either antidromically or synaptically by ipsilateral dorsolateral or dorsal column stimulation. 7. The findings that ACh depression of all tested DSCT neurones is blocked by atropine and readily evoked by acetyl‐beta‐methylcholine indicates that receptors mediating the effect are of muscarinic type.
Quantitative assessment of cardiac pump performance.
Authors: Bishop V S , Horwitz L D
Published: December 2014

1. A means of quantitating left ventricular performance in the conscious dog is presented. Changes in heart rate, stroke volume and cardiac output during elevation of left atrial pressure by acute volume expansion were measured in the conscious dog. 2. The changes in heart rate and stroke volume could be described by y = ym ‐ (ym‐yi)e‐kp, where yi and ym are initial and maximum values of the variable and p is the change in mean left atrial pressure. 3. Because cardiac output is a derived variable (stroke volume X heart rate) its response is described by a multiple exponential relationship. 4. For a given initial heart rate and inotropic state, the stroke volume response is determined by the Frank‐Starling mechanism and the pressure‐volume characteristics of the myocardium.
Post‐tetanic potentiation, habituation and facilitation of synaptic potentials in reticulospinal neurones of lamprey
Authors: Wickelgren Warren O.
Published: December 2014

1. Synaptic potentials evoked by electrical stimulation of cranial nerves were recorded in giant reticulospinal neurones (Müller cells) of lamprey. A variety of patterns of stimulation was employed to explore further the functional properties of the pathways intervening between the cranial nerve fibres and Müller cells.

2. Simultaneous low intensity stimulation of two different cranial nerves produced excitatory short‐latency synaptic potentials whose amplitudes summed linearly.

3. Tetanic (10/sec) stimulation of a cranial nerve depressed the evoked short‐latency synaptic response, but following the tetanus the synaptic response was potentiated above control amplitude for several minutes. Tetanic stimulation of one cranial nerve had no effect upon the synaptic responses evoked by stimulation of other cranial nerves.

4. Low‐frequency stimulation (1/sec to 1/20 sec) of a cranial nerve produced a progressive decrease in the amplitude of the evoked short‐latency synaptic response. This phenomenon was termed synaptic habituation because its characteristics were functionally similar to behavioural habituation in animals.

5. Habituation of the synaptic response to stimulation of one cranial nerve had no effect on the synaptic responses produced by stimulation of other cranial nerves.

6. Synaptic afterdischarges lasting from several seconds to several minutes were recorded in Müller cells. They occurred both spontaneously and in response to strong electrical stimulation of cranial nerves. For several minutes following an afterdischarge the amplitudes of short‐latency synaptic potentials produced by stimulation of any one of the cranial nerves were increased as much as twofold. This facilitation occurred equally well whether the short‐latency synaptic responses had been habituated or not.

7. A theoretical cell‐wiring diagram is proposed to account for the properties of short‐latency evoked synaptic responses and synaptic afterdischarges and for the facilitation of short‐latency responses by afterdischarges.
A potassium contribution to the response of the barnacle photoreceptor.
Authors: Hanani M , Shaw C
Published: December 2014

1. Intracellular recording from photoreceptors in the lateral eye of the barnacle show a brief negative‐going 'dip' shortly after the onset of the late receptor potential. This phase can sometimes result in a hyperpolarization relative to the resting membrane potential. 2. The dip is prominent in light‐adapted cells and is reduced by dark‐adaptation. Low extracellular Ca2+ also reduces it. 3. The amplitude of the dip changes inversely with the K+ concentration in the saline. 4. The amplitude of the dip depends on the membrane potential, with a reversal potential near ‐ 80 mV. 5. K+ blocking agents such as quinine and quinidine reduce or abolish the dip. 6. These observations indicate that the dip is due to a brief increase in K+ conductance which may be dependent on an influx of Ca ions. The fast decay of this phase may be brought about by a rapid uptake of Ca2+ by an intracellular mechanism.
Reduction of multiaxonal innervation at the neuromuscular junction of the rat during development.
Authors: Rosenthal J L , Taraskevich P S
Published: December 2014

1. A study was made of the functional and structural changes that occur during the decrease in multiaxonal innervation of neonate rat muscle fibres 2‐14 days after birth. 2. In day 8 to day 14 animals there was a constant daily loss in the average number of functionally transmitting axons/muscle fibre measured electrophysiologically. An investigation of synaptic transmission during this period revealed that the loss of functional contact from the supernumerary axons was not preceded by any sign of failing terminal conduction or a gradual decrease in transmission efficacy but rather appeared to occur abruptly. 3. Neonate end‐plates showing signs of abnormal ultrastructure were observed during the period of synapse elimination. Some axon terminals had a high cytoplasmic density and condensation of synaptic vesicles. Signs of Schwann cell encroachment into the synaptic cleft were readily found and large areas of post‐junctional membrane apposed only by Schwann cell were evident. 4. It is suggested that the mechanics of the process of synapse elimination in neonates is similar to that occurring during degeneration in the denervated adult. Transmission failure occurs abruptly at the supernumerary endings and they are disposed of by the Schwann cell.
Protection from habituation of the crayfish lateral giant fibre escape response
Authors: Bryan Joan S. , Krasne Franklin B.
Published: December 2014

1. Habituation of the lateral giant fibre escape response in the crayfish to repetitive tactile stimuli is believed to result from homosynaptic depression at the first synapse of the reflex, between tactile afferents and interneurones. Normally, habituation of escape responses to repeated innocuous stimuli is presumed to be adaptive. Experiments reported here were undertaken to determine whether habituation would occur under circumstances when it would presumably be maladaptive — in particular, when tactile receptors are stimulated by an animal's own tail‐flip movements.

2. Experiments were carried out on the crayfish isolated abdominal nerve cord, which contains the lateral giant reflex pathway.

3. Compound e.p.s.p.s elicited in the lateral giant by electrical stimulation of tactile afferents decline by from 25 to 36% over a series of eleven trials at 1/5 sec (control series).

4. To determine whether such a decline would occur when sensory afferents are stimulated during a ‘tail‐flip’, stimuli were given as in the control series but each stimulus occurred 20 msec after direct electrical stimulation of a medial giant or lateral giant escape‐command fibre at which time tail flexion movements of an intact animal would be in progress. Under these conditions% e.p.s.p. decline over 11 trials at 1/5 sec was only 16‐45% of that occurring on the control series.

5. This protective effect starts at about 10 msec after escape command neurone firing, is maximal at 20 msec, and thereafter declines, remaining weakly detectable at 100 msec. This time course is commensurate with that required for execution of a tail‐flip movement. Thus, sensory afferent‐to‐lateral giant transmission is protected from depression if stimuli occur when a tail‐flip movement is or should be occurring.

6. Giant fibre spikes do not superimpose facilitation upon a depressed reflex pathway, nor accelerate rate of recovery from depression; rather, protection is attributable to actual prevention of development of the depressed state.

7. Protection was also examined at the first synapse of the reflex, where the depression responsible for habituation is believed to occur, by recording intracellularly in the largest of the first‐order interneurones (interneurone A) of the pathway. In absence of protection, ten stimuli presented at 1/4 sec caused a mean decline of 32% in the e.p.s.p. in interneurone A. When such stimuli followed directly evoked escape command neurone firing by 20 msec this decline was reduced by 59‐100%.

8. We suggest that protection serves to prevent crayfish from habituating to stimuli produced by their own tail‐flip movements.
Calcium requirement for activation of intact aortic smooth muscle
Authors: Van Breemen C.
Published: December 2014

1. Elevation of [K+]e induced a contraction of rabbit aorta. If 10 m
M‐La3+ was applied to rabbit aortae prior to [K+]e elevation no contraction occurred. When 10 m
M‐La3+ was applied simultaneously with, or at short time periods after, elevation of [K+]e graded contractions were obtained whose magnitudes were higher if La3+ was added at a later stage.

2. Net cellular Ca fluxes associated with these graded contractions were measured using 45Ca as well as atomic absorption. Correlation of the graded contractions with the net inward Ca movements yielded a Ca activation curve for intact arterial smooth muscle cells. The curve was S‐shaped with half‐maximal activation at a net Ca uptake of 41 μmole/kg wet wt. of aorta and full activation at 64 μmole/kg. If corrections were made for the extracellular space, full activation occurred at a net Ca uptake of 102 μmole/kg smooth muscle cells or roughly 25 μmole in excess of the value calculated to bind to the activation sites on arterial smooth muscle myosin.

3. The contractile force of the smooth muscle cells not only depended on the magnitude, but also on the rate of the net Ca uptake.

4. Elevation of tissue c‐AMP through inhibition of phosphodiesterase greatly reduced both the rate and magnitude of contraction without affecting the size of the high K+ stimulated Ca influx. It was concluded that high K+‐induced depolarization activates the rabbit aorta by stimulating a net Ca uptake, and that the degree of activation is modified by c‐AMP sensitive Ca accumulation by intracellular organelles.
Atrial receptors in the dog and rabbit
Authors: Kappagoda C. T. , Linden R. J. , Mary D. A. S. G.
Published: December 2014

1. Action potentials were recorded from slips of the cervical vagi in anaesthetized dogs and rabbits. Single functional units with atrial patterns of discharge (Paintal Type A, B and intermediate) were obtained and then attempts were made to alter (i.e. convert) their patterns of discharge. Finally the points of origin of these action potentials were located.

2. Thirty unselected units were investigated in thirty dogs. Twenty‐seven of these were located in the endocardium of the vein‐atrial system and the ratio of the type A, type B and intermediate type receptors was 1:16:10; three units were located elsewhere in the chest. Conversion of the pattern of discharge was achieved in twenty of the twenty‐seven units; conversion was achieved in the single type A unit.

3. In a second series of experiments in dogs, eight Paintal Type A units were selectively studied in fifteen animals. Four of these were located in the endocardium and all were converted. The remaining four were located outside the endocardium and conversion could not be achieved in two of these. Thus in the entire investigation, the ‘type A’ units which could not be converted were all located at sites other than the atrial endocardium.

4. In the corresponding unselected study in the rabbit, eleven units were studied in eleven animals. Nine of these units were located in the atrial endocardium and the ratio of the type A, type B and intermediate type receptors was 2:1:6. Conversion was achieved in both type A units, the sole type B unit and two of the intermediate units. One of the two units found outside the atrial endocardium was a ‘type A’ unit and could not be converted.

5. The present investigation has shown that the atrial receptors with a Paintal Type A pattern of discharge are relatively rare in both dogs and rabbits. Conversion of the pattern of discharge is a relatively common phenomenon. Evidence for the proposition that there is one basic type of atrial receptor whose pattern of discharge is determined by its precise location in the vein‐atrial system is discussed.
The role of bicarbonate, chloride and sodium ions in the regulation of intracellular pH in snail neurones
Authors: Thomas R. C.
Published: December 2014

1. Intracellular pH (pHi), Cl− and Na+ levels were recorded in snail neurones using ion‐sensitive micro‐electrodes, and the mechanism of the pHi recovery from internal acidification investigated.

2. Reducing the external HCO3− concentration greatly inhibited the rate of pHi recovery from HCl injection.

3. Reducing external Cl− did not inhibit pHi recovery, but reducing internal Cl−, by exposing the cell to sulphate Ringer, inhibited pHi recovery from CO2 application.

4. During pHi recovery from CO2 application the internal Cl− concentration decreased. The measured fall in internal Cl− concentration averaged about 25% of the calculated increase in internal HCO3−.

5. Removal of external Na inhibited the pHi recovery from either CO2 application or HCl injection.

6. During the pHi recovery from acidification there was an increase in the internal Na+ concentration ([Na+]i). The increase was larger than that occurring when the Na pump was inhibited by K‐free Ringer.

7. The increase in [Na+]i that occurred during pHi recovery from an injection of HCl was about half of that produced by a similar injection of NaCl.

8. The inhibitory effects of Na‐free Ringer and of the anion exchange inhibitor SITS on pHi recovery after HCl injection were not additive.

9. It is concluded that the pHi regulating system involves tightly linked Cl−‐HCO3− and Na+‐H+ exchange, with Na entry down its concentration gradient probably providing the energy to drive the movement inwards of HCO3− and the movement outward of Cl− and H+ ions.
Non‐equivalence of impulse blockade and denervation in the production of membrane changes in rat skeletal muscle.
Authors: Cangiano A , Lutzemberger L , Nicotra L
Published: December 2014

1. A complete and long lasting blockade of nerve impulses was established in the sciatic nerve of rats, by implanting silastic cuffs of critical internal diameters. Either marcaine‐impregnated or plain cuffs were used. The contralateral sciatic nerve was sectioned. 2. At various days after the initial procedures, the extensor digitorum longus muscles of the two sides were examined with intracellular electrodes. 3. Decrease in resting membrane potential, fibrillatory activity and resistance of the action potential to tetrodotoxin developed not only in the denervated but also in the impulse‐blocked muscles. In the latter, the fibres were normally innervated since they displayed miniature end‐plate potentials and were excitable by nerve stimulation distal to the blocking cuff. 4. However, all of the above mentioned denervation‐like changes were significantly less pronounced in the blocked muscles than in the denervated ones. 5. It is concluded that in addition to loss of nerve impulses, some other neural factor must be taken into account to explain the origin of muscle changes induced by denervation. The possible relation of this additional factor with nerve degeneration is discussed.