bluuebunny/crossref_metadata_2025_split huggingface dataset:
Movements of labelled sodium ions in isolated rat superior cervical ganglia
Authors: Brown D. A. , Scholfield C. N. 
Published: December 2014

1. Isolated rat superior cervical ganglia were incubated in Krebs solution containing 24Na and carbachol for 4 min at 25° C. They were then washed at 3° C for 15 min to remove extracellular 24Na and the efflux of residual intracellular 24Na stimulated by warming to 25° C.2. During the 15 min wash at 3° C desaturation curves became exponential with a rate constant of 0·012 ± 0·001 min−1 (n = 24). This was assumed to represent loss of intracellular 24Na, and initial uptake of 24Na was calculated therefrom by back‐extrapolation to zero wash‐time. After 4 min in 24Na + 180 μ
M carbachol intracellular [24Na] so calculated was 61·6 ± 3·1 m
M (n = 18), representing 83% labelling of intracellular Na. In the absence of carbachol intracellular [24Na] was 10·0 ± 0·5 m
M, representing 49% labelling. Extracellular Na was labelled by > 90% after 4 min in 24Na. The apparent rate constant for washout of extracellular 24Na was 0·6 min−1 at 3° C and 0·95 min−1 at 25° C.3. The loss of the residual intracellular 24Na during temperature stimulation was interpreted quantitatively in terms of an exponential decline of the bulk of intracellular 24Na with an extrusion rate constant of 0·39 ± 0·1 min−1 (n = 18), efflux being delayed by passage through the extracellular space with an effective rate constant of 0·8–1·2 min−1.4. The peak rate constant (kC) for the desaturation curve at 25° C was 0·35 ± 0·01 min−1. An Arrhenius plot of log kC/T° K−1 yielded a two‐stage linear regression with a transition at 20° C. Activation energies of 8 and 31 kcal. mole−1 were calculated above and below this transition respectively.5. Omission of K from the 25° C temperature‐stimulating solution reduced kC by 62%. The K‐sensitive component of extrusion rate constant was a hyperbolic function of [K]e with half‐saturation at 5·6 m
M‐[K]e and maximum kC of 0·58 min−1.6. Cyanide (2 m
M), 2,4‐dinitrophenol (1 m
M) and ouabain (1·4 m
M) reduced kC by 50–90%. The half‐maximally inhibiting concentration of ouabain was about 60 μ
M.7. Substitution of sucrose, Li or choline for external Na did not reduce the extrusion rate of 24Na in either 6 m
M‐[K]e or 0 m
M‐[K]e. Li stimulated 24Na extrusion in Na‐free, K‐free solution.8. The properties of the ganglionic Na pump deduced from rates of temperature‐stimulated 24Na extrusion accord with the view that the ganglion hyperpolarization observed after Na loading by exposure to nicotinic depolarizing agents results from electrogenic Na extrusion. A comparable hyperpolarization is observed after temperature stimulation following Na loading.
Electrical impedance, ultrastructure and ion transport in foetal gastric mucosa
Authors: Wright G. H. 
Published: December 2014

1. The voltage transient developed across rabbit foetal gastric mucosa in response to rectangular current pulses was measured under in vitro conditions. The short‐circuit current was also measured.2. The voltage transients were used to calculate equivalent circuit parameters. The mucosa could be represented as two large capacitances in series, each shunted by a high conductance.3. Electron microscopy was carried out on some preparations after the electrical measurements had been made. An extensive smooth membrane tubular system was observed on the apical sides of the cells, with openings into the gastric lumen.4. Anoxia resulted in a reversible reduction in value of the large capacitance and short‐circuit current: the relative changes in these two quantities were very closely linked. Electron microscopy showed a large and reversible decline in the extent of the apical tubular system during anoxia.5. It was concluded that the apical tubular system plays an important role in ion transport in this preparation. Considerations of the magnitude of the capacitances and of membrane area suggest that the smaller capacitor represents the plasma membrane. The dieletric constant of the smooth membrane of the tubular system is an order of magnitude lower than that of the plasma membrane.
Gastric and pancreatic responses to meals varying in pH
Authors: Dembinski A. , Konturek S. J. , Thor P. 
Published: December 2014

1. Gastric acid response to a test meal of 10% peptone was measured in chronic gastric and pancreatic fistula cats using the Fordtran and Walsh method, monitoring the rate at which a solution of 0·5
M sodium bicarbonate had to be added to maintain constant pH of gastric content at pre‐selected values ranging from 5·0 to 1·0. Simultaneously, pancreatic secretion was determined by the standard collection technique. In this way the pH profile for the inhibition of gastric secretion and stimulation of pancreatic secretion has been established in cats.2. A peptone meal adjusted to pH 5·0 produced gastric acid output similar to the maximal response to histamine or pentagastrin. It provoked a negligible stimulation of pancreatic flow rate and bicarbonate output but a large protein output.3. Graded decrease of the peptone meal pH to below 4·0 resulted in inhibition of gastric acid production and in a concomitant stimulation of pancreatic secretory volume and bicarbonate output. A meal adjusted to pH 1·0 stimulated gastric secretion only about 30% of the response recorded at pH 5·0. Pancreatic secretion with a meal adjusted to pH 3·0 reached the highest level of about 70% of the maximal response to exogenous secretin.4. Since the observed changes in the secretory activity of the stomach and the pancreas induced by test meals adjusted to pH 3·0 can be fully reproduced by exogenous secretin, it is suggested that in the cat this hormone may be responsible for the gastric inhibitory and pancreatic stimulatory mechanisms activated during normal digestion of food.
Analysis of hyperpolarizations induced by glutamate and acetylcholine on Onchidium neurones
Authors: Oomura Yutaka , Ooyama Hiroshi , Sawada Masashi 
Published: December 2014

1. Four giant neurones, designated G‐H cells, in the right pleural ganglion of the marine pulmonate mollusc, Onchidium verruculatum, showed characteristic membrane hyperpolarization during applications of either acetylcholine (ACh) or
L‐glutamate. In the presence of ACh the membrane was hyperpolarized only transiently, while in the presence of glutamate the response was maintained. Significant increases in membrane conductance accompanied the changes in membrane potential.2. In excess potassium sea water, a slight hyperpolarization occurred when the normal concentration was increased between one‐ and twofold. However, depolarization usually occurred when the concentration was increased tenfold except on a few occasions when a slight but definite hyperpolarization occurred. These changes were all accompanied by a substantial increase in the membrane conductance. This hyperpolarization was in all probability the result of an increase in chloride ion permeability caused by the release of an ACh‐like transmitter from depolarized presynaptic nerve terminals.3. The reversal levels for glutamate‐ and ACh‐induced hyperpolarization respectively were approximately — 20 and — 17 mV with respect to the resting membrane potential.4. By changing the external ion composition, glutamate‐ and ACh‐induced hyperpolarization were shown to be the result of an increased permeability of the subsynaptic membrane to potassium and chloride ions respectively. It appears therefore that inhibition in the same G—H cells can be activated by two different transmitter substances and that each of them activates a change in the membrane permeability to a different ion.5. The relationship between the concentration of glutamate and the membrane conductance change was suggestive of two glutamate molecules reacting with a single receptor site.
The effect of early astigmatism on the visual resolution of gratings
Authors: Mitchell Donald E. , Wilkinson Frances 
Published: December 2014

1. Orientational differences in visual resolution were measured at a number of different luminance levels on two subjects with high astigmatism that had remained optically uncorrected until the age of 10. Because of their astigmatism both of these subjects see vertical contours more clearly than horizontal contours with the unaided eye.2. The measurements were made using sinusoidal gratings generated on the face of an oscilloscope with the refractive error carefully corrected with lenses and with the gratings viewed through 3 mm artificial pupils.3. Visual resolution was found to be much better for vertical than for horizontal gratings for both these subjects under these conditions. The difference between the contrast sensitivities for vertical and horizontal gratings was even evident with gratings having spatial frequencies as low as 1 c/deg, but became progressively more pronounced at higher spatial frequencies. In one of the subjects the visual acuity (the cut‐off spatial frequency) for horizontal gratings was more than 3/4 of an octave lower than that for vertical gratings.4. This is very different from the results obtained from normal subjects who typically show only a slight reduction in contrast sensitivity for oblique gratings but resolve vertical and horizontal gratings equally well.5. The quantitative differences between the contrast sensitivities for vertical and horizontal gratings of both high and low spatial frequencies cannot be accounted for by either errors of focus in one meridian or by the presence of meridional aniseikonia.6. In order to completely eliminate any optical explanations for these findings measurements of contrast sensitivity were made using sinusoidal interference fringes formed directly on the retina, thereby bypassing the eye's optics. Since the orientational differences in resolution persisted with this method it must be concluded that they are of neural origin.7. By analogy with the effects on cortical physiology that follow early selective visual deprivation in cats and monkeys, it is argued that these orientational differences in resolution are a consequence of changes induced in the neural organization of the astigmat's visual system by the distorted visual input provided by the uncorrected astigmatism early in life. It is furthermore argued that the smaller orientational differences in resolution observed in normal eyes might similarly be induced by certain asymmetries in the early visual input.
Short‐term adaptive changes in the human vestibulo‐ocular reflex arc
Authors: Gonshor A. , Jones G. Melvill 
Published: December 2014

1. Two sets of experiments have examined the vestibulo‐ocular response (VOR) to repeated sinusoidal rotation (A) in the dark and (B) after attempting visual tracking of a mirror‐reversed image of the visual surround.2. In both A and B a horizontal sinusoidal rotational stimulus of 1/6 Hz and 60°/sec angular velocity amplitude was employed, specifically chosen to lie within the presumed range of natural stimulation of the semicircular canals.3. In A each of seven subjects underwent ten 2‐min runs of the standard stimulus in the dark on each of three consecutive days, with 3‐min rest periods between runs. Using d.c. electro‐oculography (EOG) the VOR gain was measured throughout as eye velocity/head velocity. Mental arousal was maintained by competitive mental arithmetic. Constancy of EOG gain was assured by 50 min dark adaptation before experimentation.4. The results of A showed no consistent change of VOR gain over the three times scales of a run, a day and the 3‐day experiment.5. In B the same subjects underwent a similar pattern of vestibular stimulation, but during eight of the 2‐min daily runs they attempted the reversed visual tracking task. VOR gain was measured during the 1st, 6th and last runs which were conducted in the dark for this purpose. Constancy of EOG gain was maintained by using red light throughout.6. The results of B showed a substantial (approx. 25%) and highly significant (P « 0·001) reduction of VOR gain attributable solely to the 16 min of reversed visual tracking attempted during the 50 min daily experiment. In addition the pre‐test control gain was lower on day 3 than on day 1 (approx. 10% attenuation, P < 0·01) indicating a small cumulative effect from beginning to end of the 3‐day experiment.7. It is concluded (A) that the repeated vestibular stimulus did not itself cause significant attenuation of VOR gain, but (B) that superposition of a reversed visual tracking task did induce retained VOR attenuation which was solely due to the antagonistic visual stimulus.8. In conjunction with other experimental evidence it is inferred that this attenuation probably represents an adaptive change in the VOR induced at least in part by retinal image slip.
The renal blood flow and the glomerular filtration rate of anaesthetized dogs during acute changes in plasma sodium concentration
Authors: Nashat F. S. , Tappin J. W. , Wilcox C. S. 
Published: December 2014

1. The effects of acute changes in plasma Na concentration (PNa) on renal blood flow (RBF) and glomerular filtration rate (GFR) were studied in anaesthetized greyhounds. Saline was infused at a constant rate (0·1 ml. kg−1 min−1) either into a renal artery or into a systemic vein. Plasma Na concentration was altered by varying the Na concentration of the infused saline from 0·154 to 0·077, 0·616 or 1·232
M.2. Blood pressure (B.P.), packed cell volume (PCV), concentration of plasma solids (PS) and the plasma concentration of H+ and K (PK) ions were measured but no attempt was made to contain their fluctuation.3. An infusion of hypertonic saline into a renal artery usually led to an ipsilateral increase in RBF for 5‐15 min, followed by a progressive fall. Over‐all, mean values of RBF fell with PNa throughout the range studied (120‐190 m‐mole l.−1). Glomerular filtration rate rose with PNa to reach maximal values at PNa levels of 140‐160 m‐mole l.−1, but fell thereafter. The combined fall in RBF and GFR, without change in filtration fraction, at PNa values above 160 m‐mole l.−1 is consistent with an alteration in afferent arteriolar resistance. The fall in GFR despite a rise in RBF noted when PNa was reduced below 140 m‐mole l.−1 requires an additional explanation.4. Renal blood flow was independent of PK; it was inversely related to [H+] and directly related to PS. Glomerular filtration rate was independent of PCV and PK. It was also inversely related to [H+] and directly related to PS up to a value of 6 g 100 g−1 plasma, after which the relationship was reversed. These results suggest that the renal vascular responses to acute changes in PNa may be mediated in part, at least, by concurrent change in PS and [H+].
Microiontophoretic studies of the effects of cyclic nucleotides on excitability of neurones in the rat cerebral cortex
Authors: Stone T. W. , Taylor D. A. 
Published: December 2014

1. Responses of cerebral cortical neurones to the microiontophoretic application of acetylcholine, noradrenaline, cyclic adenosine 3′,5′‐monophosphate (cyclic AMP) and cyclic guanosine 3′,5′‐monophosphate (cyclic GMP) were examined.2. The application of acetylcholine and cyclic GMP to identified pyramidal tract neurones resulted in an increased frequency of firing in a large number of cells. Upon application of both substances to cells which could not be identified as pyramidal tract cells, a reduction in the frequency of spontaneous firing was sometimes observed.3. Careful current controls had no effect on the cells discussed here, indicating that the observed responses were not due to the iontophoretic currents. Also, the electro‐osmotic ejection of cyclic GMP (outward current) produced similar changes of cell firing to those which followed iontophoretic application (inward current).4. The microiontophoretic application of atropine resulted in a blockade of acetylcholine responses while leaving responses to cyclic GMP unaffected. This suggests that cyclic GMP was not acting indirectly by releasing acetylcholine from presynaptic endings.5. Ejection of cyclic GMP from solutions containing calcium ions produced responses comparable to those produced by cyclic GMP alone. It is unlikely therefore that cyclic GMP was causing excitation by chelating calcium.6. Applications of noradrenaline and cyclic AMP produced a reduction in the spontaneous discharge rate of most neurones tested.7. Phosphodiesterase inhibitors such as ICI 63,197 caused a potentiation of the noradrenaline responses of pyramidal tract neurones.8. 5′‐adenosine monophosphate produced a powerful depression of all cells to which it was applied. This action was blocked by aminophylline, suggesting the effect was mediated through an adenosine receptor. Responses to cyclic AMP were usually not abolished, but were reduced by about 50% in amplitude.9. These results are consistent with the hypothesis that cyclic AMP may mediate some neuronal effects of noradrenaline and cyclic GMP may mediate some effects of acetylcholine. The results are also consistent with the suggestion that the two nucleotides may sometimes mediate opposite cellular responses to humoral stimuli.
Electrical responses of rods in the retina of Bufo marinus
Authors: Cervetto L. , Pasino E. , Torre V. 
Published: December 2014

1. Intracellular responses to flashes and steps of light have been recorded from the outer segment and the cell body of rods in the retina of the Bufo marinus. The identification of the origin of recorded responses has been confirmed by intracellular marking.2. Responses to flashes delivered in darkness or superimposed on a background were analysed. Responses recorded from outer segments conform to the principle of ‘spectral univariance’. The shape of the response is not affected by enlarging the spot diameter from 150 to 1000 μm.3. The membrane potential measured in darkness at the outer segments varied from ‐15 to ‐25 mV. Injection of steady hyperpolarizing currents increases the size of the response to light; depolarizing currents reduce the response. The mean value of the input resistance is 97 ± 30 MΩ in darkness and increases by 20‐30% during illumination.4. The responses obtained from the cell body of rods have the same shape, time course and spectral sensitivity of those recorded at the outer segment. Injection of steady current at the cell body produces different effects than at the outer segment: hyperpolarizing currents reduce the amplitude of the response to light; depolarizing currents increase the response.5. The experimental data are fitted according to a model similar to that used to describe the responses of turtle cones (Baylor & Hodgkin, 1974; Baylor, Hodgkin & Lamb, 1974a, b).6. The model reproduces the electrical responses of the rod outer segment to a variety of stimuli: (a) brief flashes and steps of light in dark adapted conditions; (b) bright flashes superimposed on background illuminations; (c) pairs of flashes delivered at different time intervals. Responses to hyperpolarizing steps of current are also reproduced by the model.
The distribution of α‐bungarotoxin binding sites on mammalian skeletal muscle developing in vivo
Authors: Bevan Stuart , Steinbach Joe Henry 
Published: December 2014

1. The distribution of α‐bungarotoxin binding sites on embryonic and neonatal rat skeletal muscle fibres was determined by autoradiography. Most of the bungarotoxin binding could be inhibited by curare. This observation, together with the spatial distribution of toxin‐binding sites, indicates that the distribution of bound toxin reflects that of acetylcholine (ACh) receptors on these developing muscle cells.2. At 15 days of embryogenesis, muscle fibres showed an essentially uniform distribution of receptors. By 16 days, many fibres showed an accumulation of receptors in their mid‐region. This accumulation was at the same location as histochemically demonstrated cholinesterase activity.3. At 16 days ACh receptors were distributed over the entire length of the fibres, with a gradient of increasing density as the accumulation was appoached. The density of toxin binding sites in the accumulation was greater than the general level on 15 day cells, suggesting that the high junctional density does not develop solely by the loss of extrajunctional receptors.4. The accumulations of ACh receptors became more pronounced and circumscribed with embryonic development, and after birth the extent of the localizations appeared to follow the size of the neuromuscular junction. The extrajunctional receptor density decreased with development, and by 1 week after birth was undetectable by the methods used.5. The results suggest that the high junctional receptor density found on adult, innervated skeletal muscle fibres develops after the formation of the neuromuscular junction.
Spectral and orientation specificity of single cells in foveal striate cortex of the vervet monkey, Cercopithecus aethiops
Authors: Bertulis Algis , Guld Christian , Lennox-Buchthal Margaret A. 
Published: December 2014

1. The spectral sensitivity, orientation specificity and inhibitory surround of seventy‐three cells were studied in the vervet monkey. The eye was in the dark or illuminated with steady white or spectral light. The cells were in the striate cortex corresponding to the foveal representation. Nearly all the cells gave on‐ or on/off‐responses.2. More than a third of the cells (41%) responded over a narrow spectral band, in the blue, green, yellow or red section. Three quarters of them were orientation specific with flanking inhibitory surround and half of these were of the ‘stopped‐end’ variety as well. The effect of the wave‐length of the background indicated that only a half were activated by such excitatory—inhibitory colour pairs as have been described in the geniculate nucleus.3. A third of the cells (36%) responded to most colours but with the greatest response to green, yellow or red. Less than half were orientation specific. Unlike the narrowband cells, the response decreased with the intensity of the light. Two thirds were activated by the excitatory‐inhibitory colour pairs that have been described in the geniculate nucleus.4. In both groups of cells the wave‐length of the spectral peak could be different when the stimuli were weak compared with when they were strong.5. One quarter of the cells (23%) gave on/off‐responses to all spectral flashes; half were not orientation specific. The difference in orientation specificity between narrow‐ and broadband cells is significant (P < 0·01).
Movements of radioactive potassium in isolated rat ganglia
Authors: Scholfield C. N. 
Published: December 2014

1. Isolated rat superior cervical ganglia were continuously superfused with 42K (or 86Rb) solution and the amount of radioactivity taken up was monitored using scintillation counting.2. Entry of 42K into the ganglia could be resolved into two components, one amounting to 83% of the total 42K uptake, with a rate constant of 0·015 min−1, and the other of 17% of the total, with a rate constant of 0·15 min−1.3. With 6 m
M‐K in the bathing solution, the equilibrium uptake of 42K after 4 hr corresponded to an intracellular concentration of 147 m
M‐K. Changes in the K concentration of the bathing solution (0·5‐20 m
M) had little effect on this value.4. Carbachol or nicotine caused a rapid net loss of 42K. 42K was recaptured on washing out the depolarizing agents, with a rate constant of about 0·3 min−1. This recapture rate was slowed by ouabain, dinitrophenol, cyanide, mersalyl and by reducing the K concentration in the bathing solution.5. Efflux of 42K from preloaded ganglia occurred with a rate constant of 0·017 min−1. This rate was increased about sixfold by 180 μ
M carbachol in 6 m
M‐K but not in 150 m
M‐K suggesting that the increase in efflux was mainly a consequence of the depolarization caused by carbachol.6. 86Rb fluxes and the effects of carbachol thereon were similar.