bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristics of neural transmission from the semicircular canal to the vestibular nuclei of cats
Authors: Jones G. Melvill , Milsum J. H. 
Published: December 2014

1. The characteristics of the dynamic response of specifically canal‐dependent neural units in cat vestibular nuclei have been examined during sinusoidal rotation of the head in decerebrate cats over the narrow frequency range 0·–1·7 Hz.2. Unit action potential frequencies were averaged on line from extracellular steel micro‐electrodes stereotaxically located in the vestibular nuclei through the intact cerebellum.3. Action potential frequency was approximately in phase with stimulus angular velocity, the mean phase for forty‐six units being + 11·°
S.E. of the mean ± 2·2°). Correction for a form of dynamic asymmetry reduced this value almost to zero.4. The mean gain of thirty‐nine single unit responses was 0·76
S.E. ± 0·08) AP/sec per °/sec. The gain varied as the (−0·28) power of stimulus angular velocity, for the five cells appropriately tested.5. A method was evolved for computing the spontaneous condition of cells, in terms of an equivalent spontaneous firing frequency, fsp irrespective of whether they were spontaneously active or silent. This fsp value was normally distributed about a mean value of 11·2 AP/sec (range + 70 to − 40 AP/sec).6. Directionality was examined in 116 units, of which 62% were ipsilateral (e.g. cells on left side excited by left‐going rotational velocity) and 38% contralateral. Ipsilateral units proved easier to isolate and retain than contralateral ones.7. No significant differences in mean phase or gain were found in the sub‐sets of spontaneously active/inactive cells and ipsilateral/contralateral cells.8. It is inferred that the cell population examined was a functionally homogeneous one in which the neural signal was closely tied to the angular velocity of canal rotation for the narrow band of sinusoidal rotational stimuli here employed. It is suggested that this signal is probably retained essentially intact in the ensemble neural message fed forwards from this region.
Field potentials evoked in the brain stem of the cat by stimulation of the carotid sinus, glossopharyngeal, aortic and superior laryngeal nerves
Authors: Biscoe T. J. , Sampson S. R. 
Published: December 2014

1. In a primarily topographical study, the field potentials evoked in the brain stem of the cat by stimulation of the sinus, glossopharyngeal (IX), aortic and superior laryngeal (SLN) nerves have been recorded with glass micro‐electrodes.2. Extracellular negative potentials were evoked in the region of the nucleus of the tractus solitarius and in the lateral reticular formation (LRF) by electrical stimulation of all four nerves. There were differences in the form of these potentials amongst the nerves, particularly between sinus‐IX and aortic‐SLN. The potentials were identified as post‐synaptic with early and late components and were sometimes preceded by an afferent volley.3. Extracellular positive potentials were evoked in the subnucleus reticularis medialis medullae oblongatae and the nucleus reticularis gigantocellularis. Intracellularly recorded hyperpolarizations recorded from six cells had the same time course as the extracellular positivity. Spontaneously active cells encountered in these regions were sometimes depressed for the duration of the positivity.4. Each of the above field potentials was maximal in the region of Horsley—Clarke A. P. co‐ordinates −10 to −13 mm.5. At A.P. co‐ordinates of −15 to −17 mm negativity showing post‐tetanic potentiation was evoked, at latencies similar to the negativity in the LRF, in the commissural nucleus of Cajal, the dorsolateral reticular formation and the medial reticulo‐spinal tract.6. Negative potentials were evoked in the contralateral LRF.
Monosynaptic chemical and electrical connexions between sensory and motor cells in the central nervous system of the leech
Authors: Nicholls J. G. , Purves D. 
Published: December 2014

The synaptic connexions that underlie three different segmental shortening reflexes have been traced by recording intracellularly from individual sensory and motor nerve cells in the
C.N.S. of the leech. The fourteen sensory cells involved in these reflexes respond specifically to one of three modalities: touch, pressure, or noxious stimuli applied to the skin. All three types of sensory neurone give rise to excitatory synaptic potentials in two large motoneurones. Each of these motor cells provides excitatory innervation to the longitudinal muscle fibres of the opposite side of the segment. The mechanism of synaptic transmission is, however, different for each type of sensory cell.1. An impulse in a sensory cell that responds to touch gives rise to a short‐latency depolarizing potential in the large longitudinal motoneurones by way of an electrical synapse. This junction rectifies so that excitation can spread in only one direction (from the sensory to the motor cell), whereas a hyperpolarizing potential can pass only in the opposite direction.2. The synaptic potential evoked in the motoneurone by an action potential in a sensory cell responding to noxious stimuli can be attributed to the action of a chemical transmitter agent and has different properties: the post‐synaptic potential arises after a delay of about 2‐4 msec, is abolished by high concentrations of Mg, and enhanced by high concentrations of Ca. Several lines of evidence show that this connexion is monosynaptic.3. The synaptic potential following an impulse in a pressure cell is produced by both chemical and electrical synaptic mechanisms. Rectification, similar to that described for the touch cell, also occurs at this electrical synapse.4. One or more impulses in any one of the fourteen mechanoreceptor cells in the ganglion can initiate impulses in the large longitudinal motoneurones to produce a shortening of the segment. The contraction is abolished by blocking impulse initiation in the motoneurones.5. The arborizations of the sensory cells and the motoneurone within the neuropile have been studied histologically after injecting a fluorescent dye. Their processes are intertwined in a highly complex manner so that the sites of the synaptic junctions cannot be determined with the resolutions so far achieved. Nevertheless, taken together the histological and the electrical results support the idea that individual cells are connected in a stereotyped pattern and operate by distinctive mechanisms.6. These findings provide a basis for studying the functional role of chemical and electrical synaptic mechanisms in these pathways.
Adrenaline in bird brain
Authors: Juorio A. V. , Vogt Marthe 
Published: December 2014

1. Catecholamine estimations were made on the whole diencephalon and on the hypothalamus of pigeons and fowls using fluorimetry of the acetylated amines as one, and bio‐assay after chromatographic separation of the amines as a second method.2. There was no significant difference between the results obtained by the two methods; for pigeons mean percentage methylation was 10% with one and 12% with the other technique, and in the Rhode Island Red breed of fowls the corresponding figures were 28 and 31%.3. The percentage methylation for the hypothalamus of another breed of fowls (Plymouth Rock) was the same as in Rhode Island Red, but it was significantly lower in White Leghorn birds.4. Between the ages of 3·5 weeks and maturity the percent methylation remained unchanged.5. There is no evidence to suggest that bio‐assay of adrenaline as used in this and previous work lacks specificity, but differences between avian breeds exist and have to be reckoned with.
The effect of hypercapnia on myocardial blood flow and metabolism
Authors: Ledingham I. McA. , McBride T. I. , Parratt J. R. , Vance J. P. 
Published: December 2014

1. In closed‐chest dogs anaesthetized with trichlorethylene, the inhalation of carbon dioxide sufficient to increase the arterial PCO2 from 40 to about 100 mm Hg, increased myocardial blood flow (measured using a 133Xe clearance technique) and right atrial pressure. There were no consistent changes in mean arterial blood pressure, heart rate or cardiac output.2. The effect of hypercapnia on myocardial blood flow was not influenced by the previous administration of atropine and propranolol or of bretylium. It can be concluded, therefore, that the elevated arterial PCO2 has a direct vasodilator effect on the myocardial microcirculation.3. During hypercapnia the coronary sinus PO2 was increased and the coronary arteriovenous oxygen content difference, and calculated myocardial oxygen consumption, reduced. It is suggested that this latter effect may be the result of myocardial depression produced by the decrease in arterial blood pH.4. There was no evidence of myocardial glucose uptake either before or during hypercapnia. The myocardial extraction of lactate and pyruvate at rest varied between 0 and 55%. During acute hypercapnia the extraction of lactate usually fell.5. When the arterial PCO2 was maintained at 100 mm Hg for a period of 1 hr the effects on myocardial blood flow and on oxygen consumption were not sustained.6. Stepwise increments and decrements in arterial PCO2 of 10–20 mm Hg produced corresponding increases and decreases in myocardial blood flow and demonstrated that changes in arterial PCO2 of 20–30 mm Hg can markedly affect blood flow in the myocardium.
Haemodynamic and other studies on the renoprival hypertensive rat
Authors: Ledingham J. M. , Pelling D. 
Published: December 2014

1. The optimal conditions for the development of hypertension after total nephrectomy were defined in the rat. Under these conditions, haemodynamic changes were then studied before and for 3 days after total nephrectomy in the unanaesthetized animal and compared with mock‐nephrectomized controls.2. Changes in cardiac output were followed with an electromagnetic flowmeter chronically implanted on the ascending aorta, and mean arterial pressure with an indwelling aortic cannula.3. Haematocrit fell in animals developing hypertension, due to plasma volume expansion. Restriction of administered saline did not reduce the fall in haematocrit without also preventing development of the hypertension.4. Cardiac output and stroke volume increased significantly on the second and third days after nephrectomy. Peripheral resistance remained unchanged and pulse rate tended to fall.5. The increase in cardiac output appeared to be more than could be accounted for by anaemia alone, and it is suggested that plasma volume expansion was partly responsible.6. In another group of rats developing renoprival hypertension a correlation was found between changes in plasma volume and arterial pressure over the three days.7. Renoprival hypertension was accompanied by a slight but significant reduction in oxygen consumption in comparison with the controls.8. No relationship was found between the changes in blood pressure, and plasma sodium and potassium levels.9. It is concluded that the observed rise in cardiac output associated with renoprival hypertension as induced in this study was not attributable to anaemia nor to a rise in metabolic rate. The implications of this situation are discussed in relation to a theory of the pathogenesis of hypertension and the findings of other workers.
Kinetics of pentose permeation in the perfused rat heart
Authors: Fisher R. B. , Gilbert J. C. 
Published: December 2014

1. The fractional permeation of heart cell water by
L‐arabinose and
D‐xylose after a standard period of perfusion is less the higher the extracellular pentose concentration.2. At any given pentose concentration the kinetics of permeation are consistent with passive diffusion through the cytoplasm or with transport across the cell membrane by a saturable carrier.3. The concentration dependence of permeation is inconsistent with passive diffusion.4. The kinetics of
L‐arabinose permeation are consistent with a carrier having Vmax = 2·2 m‐mole/l. extracellular water per min and a half‐saturation concentration [K] of 0·5 × 10−4
M. The corresponding figures for
D‐xylose are Vmax = 1·4, [K] = 1·6 × 10−4
M.
Autoradiographic demonstration of inhomogeneous distribution of sodium in single oocytes of Bufo bufo
Authors: Dick D. A. T. , Fry D. J. , John P. N. , Rogers A. W. 
Published: December 2014

1. Autoradiography of frozen cells labelled with 22Na has been used to locate a sequestered fraction of internal Na in the oocyte which exchanges very slowly or not at all with external Li.2. Relative grain density in nucleus and cytoplasm, measured photometrically, was used as an indication of 22Na distribution within the oocyte. In test experiments grain density fell to 50% within 19 μm of the edge of the section. Owing to the large diameter of the oocyte (> 600 μm) and its nucleus (> 200 μm), this resolution was adequate to determine cytoplasmic/nuclear (C/N) ratios of grain density.3. In oocytes fully loaded with 22Na, the mean C/N ratio was 0·92 ± 0·03 (n = 11). After 5 hr exchange in Li‐substituted Na‐free Ringer solution, the mean C/N ratio was 2·18 ± 0·04 (n = 11). After 5 hr exchange in Ringer solution as a control, the mean C/N ratio was 1·39 ± 0·18 (n = 7). The cytoplasm thus contained a fraction of 22Na inexchangeable with Li, and more slowly exchangeable with Na than that in the nucleus.4. The non‐Li‐exchangeable fraction of internal Na thus revealed appeared to be quantitatively similar to that already demonstrated by studies of 22Na fluxes and of internal Na activity by means of Na‐sensitive micro‐electrodes.
The penetration of inulin, sucrose, mannitol and tritiated water from the interstitial space in muscle into the vascular system
Authors: Crone Christian , Garlick David 
Published: December 2014

1. An isolated gastrocnemius muscle from cat was perfused with a modified Ringer fluid containing the extracellular tracers mannitol, sucrose and inulin and in some cases tritiated water (HTO). When equilibration of the tracers between the perfusate and the tissue was obtained, perfusion with tracer‐free fluid was started.2. The fractional rate of escape, Φ (t), of the tracers was followed. For all tracers it declined steadily with time. The rate of decline was faster for the smaller extracellular molecules when any combination of two extracellular tracers was studied.3. Arrest of flow for 1–2 min lead to an increase in Φ (t) for the extracellular tracers when flow was resumed. There was little or no effect upon Φ (t) for HTO.4. Doubling the rate of flow had no effect upon Φ (t) for the extracellular tracers, while that of HTO increased.5. We conclude that the cause of the decline in Φ (t) for the extracellular tracers is concentration gradients in the interstitial space. The findings raise problems in methods for studying capillary permeability by means of the fractional rate of escape of tracers from the interstitial space into the vascular system.
Response of semicircular canal dependent units in vestibular nuclei to rotation of a linear acceleration vector without angular acceleration
Authors: Benson A. J. , Guedry F. E. , Jones G. Melvill 
Published: December 2014

1. Recent experiments have shown that rotation of a linear acceleration vector round the head can generate involuntary ocular nystagmus in the absence of angular acceleration. The present experiments examine the suggestion that adequate stimulation of the semicircular canals may contribute to this response.2. Decerebrate cats were located in a stereotaxic device on a platform, slung from four parallel cables, which could be driven smoothly round a circular orbit without inducing significant angular movement of the platform. This Parallel Swing Rotation (PSR) generated a centripetal acceleration of 4·4 m/sec2 which rotated round the head at 0·52 rev/sec.3. The discharge frequency of specifically lateral canal‐dependent neural units in the vestibular nuclei of cats was recorded during PSR to right and left, and in the absence of motion. The dynamic responses to purely angular motion were also examined on a servo‐driven turntable.4. Without exception all proven canal‐dependent cells examined (twenty‐nine cells in nine cats) were more active during PSR in the direction of endolymph circulation assessed to be excitatory to the unit, than during PSR in the opposite direction.5. The observed changes in discharge frequency are assessed to have been of a magnitude appropriate for the generation of the involuntary oculomotor response induced by the same stimulus in the intact animal.6. The findings suggest that a linear acceleration vector which rotates in the plane of the lateral semicircular canals can be an adequate stimulus to ampullary receptors, though an explanation which invokes the modulation of canal cells by a signal dependent upon the sequential activation of macular receptors cannot be positively excluded.
Non‐cholinergic transmission by post‐ganglionic motor neurones in the mammalian bladder
Authors: Ambache N. , Zar M. Aboo 
Published: December 2014

1. In mucosa‐free preparations of the detrusor muscle electrical stimulation with 0·1 msec pulses has been utilized to reveal the non‐cholinergic nature of most, if not all, of the post‐ganglionic motor neurones in the guinea‐pig bladder.2. The twitches elicited by 0·1 msec pulses were abolished by tetrodotoxin, but were not reduced by dimethyltubocurarine or by hexamethonium. Hexamethonium was nevertheless present in all the experiments in order to restrict acetylcholine action to ‘muscarinic’ receptors in the muscle fibres.3. There was little or no diminution in the twitches after prolonged exposure to atropine, 10−8‐10−5 g/ml., although the twitch‐matching dose of acetylcholine was raised 1000–2500 times. Hence, there was no anomalous refractoriness to atropine in these ‘muscarinic’ receptors.4. Despite massive atropinization, the recruitment of unoccupied transmitter‐receptors by means of extra pulses remained unaffected.5. Eserine failed to potentiate the atropine‐resistant twitches.6. The twitches were not depressed by morphine.7. Noradrenaline produced relaxation and twitch reduction. The twitches persisted after α + β adrenoceptor blockade with phentolamine + pronethalol and were unaffected by the monoamine oxidase and catecholamine‐O‐methyl transferase inhibitors, tranylcypromine and pyrogallol.8. Rapid contractions were elicited by 5‐HT and by histamine but the twitches remained unaltered after antagonism of 5‐HT by methysergide and of histamine by mepyramine.9. The twitches could be mimicked by injections of ATP, but after desensitization of the preparation to ATP the response to electrical stimulation remained unaltered.10. Prostaglandins E2 and F2α, only in large doses, produced delayed, sluggish contractions which persisted after the wash; these contractions were quite different from the responses to electrical stimulation, which were immediate, sharp and brief.11. The non‐cholinergic nature of the post‐ganglionic motor neurones was confirmed in the bladder of two other species, the cat and the rabbit.
The electrical activity of the digestive tract of the sheep as an indication of the mechanical events in various regions
Authors: Ruckebusch Y. 
Published: December 2014

1. A method is described in the conscious sheep for recording oscillographically the electrical potentials led from enamelled stainless‐steel wires implanted in the wall of the stomach and intestine.2. Slow waves characterized by cyclically recurring and rhythmic fluctuation in voltage have been recorded, together with the superimposed fast activity or burst of spikes when the muscle is contracting. The whole activity comprised a distinguishable pattern of grouped discharge which is synchronous with mechanical events within different regions of the alimentary tract.3. Grouped discharge occurs at a regular frequency of 7/min in the pyloric part of the abomasum and 18/min from the intestine, but 13/min from the middle duodenum and proximal ileum. Only the major grouped discharges of the fore‐stomach is correlated with the orderly sequential movements of the reticulum and rumen.4. The relationship between electrical and mechanical activity of the reticulo‐rumenal movements was examined at rest, and during feeding and ruminating.5. Electrical correlates of motor activity in the small bowel were investigated under different dietary regimens.
Electrical constants of trabecular muscle from mammalian heart
Authors: Weidmann Silvio 
Published: December 2014

1. The passive electrical properties of muscle bundles obtained from the right ventricle of sheep or calf hearts were determined. Preparations were kept in silicon oil; through extracellular electrodes constant current pulses were made to flow between the ends of the bundles.2. Using micro‐electrodes for potential recording, the following data were obtained: (i) a space constant of 880 μ; (ii) a membrane time constant of 4·4 msec; (iii) a ratio of intra‐to‐extracellular longitudinal resistance of 3·5: 1; (iv) a conduction velocity of 0·75 m/sec.3. The intracellular specific resistance (Ri) in the longitudinal direction was 470Ω cm, corresponding to 3 times Ri of Purkinje fibres or 9 times the specific resistance of Tyrode solution.4. A calculation of specific membrane resistance (Rm) and capacity (Cm) was up against uncertainties in estimating the surface area. Taking morphological data as obtained by light microscopy, Rm works out at 9100Ω cm2, Cm 0·81 μF/cm2. Electron micrographs suggest that the true surface membrane might be either larger (T‐tubules) or smaller (tight junctions between parallel fibres) than the surface area as seen by the light microscope.5. The apparently small value of Cm seems to indicate that the flow of current between ‘outside’ and ‘inside’ is restricted to only a fraction of the fibre surface, while a considerable part of the contact area between parallel fibres is of the low‐resistance type. This would provide for functional connexions not only at the level of intercalated disks, but also along parallel‐running fibres.
Effects of calcium on the contraction of the hypodynamic frog heart
Authors: Chapman R. A. , Niedergerke R. 
Published: December 2014

1. The time course of build‐up or decline of twitch tension in response to enhancement or reduction of the external calcium concentration was determined in frog heart ventricles, in the hypodynamic state as well as under non‐hypodynamic conditions.2. The tension build‐up induced by high calcium was greatly slowed when the heart passed into the hypodynamic state, whereas the decline in low calcium was little altered by this condition.3. The tension decline consisted of two approximately exponential phases, an initial rapid phase (t½ between 3 and 10 sec) and a later slow phase (t½ between 50 and 180 sec).4. A similar composite time course of tension build‐up only occurred under certain conditions: (a) in ventricles in which the hypodynamic state had not developed; (b) after a conditioning period of exposure to enhanced calcium or reduced sodium concentrations.5. The results are explained on the assumption that contraction is brought about by the co‐operative action inside heart cells of two calcium compounds whose concentrations change at different rates after variation of the external calcium concentration.6. Formal relationships describing the dependence of twitch tension on the concentration of these two hypothetical compounds are obtained.A tentative explanation of the development of the hypodynamic state is also proposed.
The effect of calcium ions on long chain fatty acid transport by slices of rat jejunum
Authors: Munday K. A. , Parsons B. J. , York D. A. 
Published: December 2014

1. There is a large increase in palmitic acid uptake by rat jejunum slices when incubated in the presence of calcium. This effect is observed at both 37 and at 0° C.2. The presence or absence of calcium in the incubation medium does not affect triglyceride synthesis from absorbed fatty acid.3. The release of synthesized triglyceride from the tissue into the medium is increased by calcium.4. The probability that calcium transport and long chain fatty acid transport may be interrelated at both the brush border and at the basal and lateral membranes of the intestinal mucosal epithelial cell is discussed.