bluuebunny/crossref_metadata_2025_split huggingface dataset:
Facilitation of monosynaptic excitatory synaptic potentials in spinal motoneurones evoked by internuncial impulses
Authors: Kuno M. , Weakly J. N. 
Published: December 2014

1. Descending tracts and primary afferent fibres were chronically degenerated in the lumbosacral cord of the cat, and attempts were made to evoke monosynaptic e.p.s.p.s in motoneurones by stimulation of interneurones with a pair of fine electrodes inserted into the cord.2. The reversal potential of monosynaptic e.p.s.p.s so produced was more negative than that measured for monosynaptic e.p.s.p.s produced by afferent impulses.3. Monosynaptic e.p.s.p.s evoked in motoneurones by internuncial impulses showed a significantly greater facilitation than those produced by afferent impulses.4. Monosynaptic e.p.s.p.s in a motoneurone produced by supramaximal intraspinal stimuli often revealed a fluctuation in amplitude. In such cases, when two successive stimuli were applied at a short interval, the mean amplitude of the second e.p.s.p.s was greater than that of the first e.p.s.p.s. This facilitation was associated with a decrease in the coefficient of variation of the e.p.s.p. amplitude fluctuation.5. The degree of facilitation of monosynaptic e.p.s.p.s evoked by internuncial impulses was not related to the amount of transmitter released by the preceding impulses.6. It is concluded that facilitation of monosynaptic e.p.s.p.s evoked by both afferent and internuncial impulses is based on the same mechanism and that the degree of facilitation of e.p.s.p.s is entirely determined by the nature of presynaptic elements.
An attempt at an analysis of the factors determining the time course of the end‐plate current
Authors: Kordaš M. 
Published: December 2014

1. An attempt was made to analyse further the factors which might determine the time course of the falling phase of the end‐plate current.2. The end‐plate current was measured by ‘clamping’ the membrane potential during neuromuscular transmission. The falling phase of the end‐plate current had an exponential and a non‐exponential portion.3. The exponential portion of the falling phase of the end‐plate current was found to be strongly affected by changes in the membrane potential and by relatively small changes in temperature.4. It is suggested that the two rate constants which determine the dissociation of the receptor‐mediator complex are affected by both temperature and the membrane potential. Under certain experimental conditions these two rate constants alone seem to determine the time course of the exponential portion of the falling phase of the end‐plate current.
The effect of tetanus toxin at the neuromuscular junction in the goldfish
Authors: Mellanby Jane , Thompson P. A. 
Published: December 2014

1. The effect of tetanus toxin on neuromuscular transmission in the abductor superficialis muscle of the goldfish fin has been investigated.2. The abductor superficialis muscle is multiply innervated and junction potentials (j.p.s) and miniature junction potentials (min.j.p.s) can be recorded with an intracellular micro‐electrode at any point of impalement. Intracellular recordings have been made from muscles in which neuromuscular transmission has been blocked, either completely, or partially, by
I.M. injection of tetanus toxin. In addition, the tension response of both acutely and chronically toxin‐blocked muscles to carbachol (1 × 10−4
M) has been investigated.3. As the neuromuscular block proceeds, the frequency of min.j.p.s falls, and some time after the muscle has stopped responding to nerve stimulation the min.j.p.s disappear.4. In muscles in which the block has not yet proceeded to completion, it has been found that the reduction in the frequency of the min.j.p.s is unaccompanied by any change in their range of amplitudes.5. The min.j.p. frequency can be greatly increased in such incompletely blocked preparations by repetitive stimulation of the nerve (at, for example, 100/sec for 10 sec). The min.j.p.s obtained are indistinguishable from those seen in the absence of stimulation. Additionally, min.j.p.s can be evoked by similar repetitive stimulation in muscles which are completely blocked, and in which no min.j.p.s are seen without stimulation, so long as the block has only been complete for a short time.6. The tension response to carbachol of muscles which have been paralysed by tetanus toxin for only a few days is identical with that of normal muscles. In contrast, chronically toxin‐paralysed muscles contract more rapidly, usually more vigorously, and relax more rapidly than normal muscles.7. It is concluded that tetanus toxin prevents both the nerve‐stimulated and spontaneous release of acetycholine from the presynaptic terminals in the abductor superficialis muscle of the goldfish fin.
Inhibitory and excitatory effects of dopamine on Aplysia neurones
Authors: Ascher P. 
Published: December 2014

1. Electrophoretic application of dopamine (DA) on Aplysia neurones elicits both excitatory and inhibitory effects, which in many cases are observed in the same neurone, and often result in a biphasic response.2. The DA receptors are localized predominantly on the axons. Desensitization, which occurs after repeated injections or with bath application of DA, is more marked for excitatory responses.3. Tubocurarine and strychnine block the DA excitatory responses without affecting the inhibitory ones, which can be selectively blocked by ergot derivatives. It is concluded that the excitatory and inhibitory effects are mediated by two distinct receptors.4. The two DA receptors can be pharmacologically separated from the three ACh receptors described in the same nervous system.5. In some neurones the dopamine inhibitory responses can be inverted by artificial hyperpolarization of the membrane at the potassium equilibrium potential, EK, indicating that dopamine causes a selective increase in potassium permeability.6. In other neurones the reversal potential of dopamine inhibitory responses is at a more depolarized level than EK, but can be brought to EK by pharmacological agents known to block the receptors mediating the excitatory effects of DA.7. In still other neurones, the hyperpolarization induced by DA cannot be inverted in normal conditions, but a reversal can be induced by ouabain or by the substitution of external sodium by lithium. These results are discussed in terms of an hypothesis in which dopamine increases the potassium permeability of a limited region of the axonal membrane.8. It is concluded that a selective increase in potassium permeability probably accounts for all dopamine inhibitory effects in the neurones studied.
Stimulation, by inhibition of (Na+‐K+‐Mg2+)‐activated, ATP‐ase, of acetylcholine release in cortical slices from rat brain
Authors: Vizi E. S. 
Published: December 2014

1. A study has made of the effect of (Na+‐K+‐Mg2+)‐activated membrane ATP‐ase inhibitors on the acetylcholine release from the terminals of enteric nerves and from cortical slices.2. The resting output of acetylcholine from slices of rat cortex was not affected by tetrodotoxin or by noradrenaline, indicating the lack of propagated activity during rest. Furthermore, there was an output of acetylcholine in the absence of Ca.3. The resting acetylcholine output from cortical slices was increased by (a) addition of ouabain or (b) administration of sodium p‐hydroxymercuribenzoate (PHMB), (c) sodium withdrawal and (d) Ca replacement by Ba+.4. Omission of Ca in the presence of 1 m
M ethyleneglycol‐bis‐(β‐aminoethyl‐ether)‐N,N′‐tetra‐acetic acid (EGTA) did not affect the increase of acetylcholine release by the inhibition of (Na+‐K+‐Mg2+)‐activated ATP‐ase induced by ouabain or by PHMB, but reduced that due to Na removal.5. Ouabain increased acetylcholine release promptly.6. Mg‐excess (9·3 m
M), noradrenaline and adrenaline were capable of reducing the increase of acetylcholine release from cortical slices evoked by ouabain, PHMB or by Ca replacement by Ba, but not by Na removal.7. A possible role for (Na+‐K+‐Mg2+)‐activated ATP‐ase in the release of acetylcholine is discussed. It is suggested that the effect of Ca and Mg ions on acetylcholine release might be attributed to their ability to inhibit and activate the membrane ATP‐ase, respectively.
Morphology of interneurones mediating Ia reciprocal inhibition of motoneurones in the spinal cord of the cat
Authors: Jankowska Elżbieta , Lindström S. 
Published: December 2014

1. Interneurones identified by physiological criteria (Hultborn, Jankowska & Lindström, 1971b) to mediate Ia reciprocal inhibition of motoneurones in the spinal cord of the cat were stained by intracellular injection of a fluorescent dye (Procion Yellow).2. The somas of the stained cells were found in Rexed's lamina VII, just dorsal or dorsomedial to the motor nuclei. Their size was about 30 × 20 μm. The cells had four to five slender, weakly branching dendrites. The total extension of their dendritic trees was about 600 μm dorsoventrally, 400 μm mediolaterally and 300 μm rostrocaudally.3. The axons originated from a separate axon hillock or from the base of a dendrite. They were myelinated with external diameter of about 6–14 μm and projected to either the ipsilateral ventral or lateral funiculi. Early collaterals were found only exceptionally. Some axons bifurcated into an ascending and a descending branch within the funiculi.4. The possibility of identifying the Ia inhibitory interneurones on purely morphological grounds is discussed.
The effect of chronic duct ligation on the vascular and secretory responses of the cat's submaxillary gland
Authors: Darke A. C. , Smaje L. H. 
Published: December 2014

1. The object of the present experiments was to re‐investigate the role of kallikrein in functional hyperaemia in the submaxillary gland of the cat. Kallikrein concentration in the gland and saliva was reduced by ligation of the duct for 2–3 days before the acute experiment, at which time the duct was cannulated proximal to the ligation and blood flow and salivation measured.2. Despite the fall in kallikrein concentration, a normal two‐phase vascular response was obtained on continuous stimulation of the chorda‐lingual nerve at 1–5 Hz and the progressive increase in blood flow to a constant level characteristic of 10 and 20 Hz stimulation was also seen. Quantitatively, the increase in blood flow following a 10 sec stimulation was reduced to about 75% of control values at all stimulation frequencies used and the maintained vasodilatation was reduced when using continuous stimulation at 1 Hz but not at 10 and 20 Hz.3. The supersensitivity to the vasodilator properties of bradykinin, previously reported to follow duct ligation, was confirmed.4. The increased blood flow produced by chorda‐lingual nerve stimulation could be delayed by circulatory arrest. Evidence was obtained suggesting that the vascular response to chorda stimulation delayed by arterial occlusion was not mediated by kallikrein alone.5. It was concluded that kallikrein was not the sole mediator of functional hyperaemia in the cat submaxillary gland but that a combination of vasodilator nerves and kallikrein release explained more phenomena than either hypothesis alone.
Increased thyroxine secretion following administration of dinitrophenol to rats
Authors: England P. , Harland W. A. , Orr J. S. , Randall T. W. 
Published: December 2014

1. Feeding male rats 0·2% dinitrophenol (DNP) in the diet caused weight loss, a significant fall in the plasma protein bound iodine concentration, and a rise in the thyroxine secretion rate. Thyroxine concentration was raised in the liver and intestinal tract with contents, reduced in the carcass, and unchanged in the pelt.2. Radio‐iodine uptake by the thyroid gland was unchanged but there was a significant fall in the thyroid/serum activity ratio.3. Five hours after tracer radiothyroxine, DNP treated rats had a reduced fraction of dose in the plasma, with raised concentrations in the liver and intestines.4. Fractional turnover rates of radiothyroxine in plasma, liver and carcass were raised in DNP treated animals.5. DNP caused a significant increase in the biliary clearance of radiothyroxine, when measured immediately after administration of tracer and 4 hr later.6. It is postulated that DNP displaces thyroxine from its plasma binding proteins and that the displaced hormone is excreted in the bile. This wastage together with increased demand resulting from DNP induced hypermetabolism results in increased output of thyroxine by the thyroid gland.
The interaction of reflexes elicited by stimulation of carotid body chemoreceptors and receptors in the nasal mucosa affecting respiration and pulse interval in the dog
Authors: Angell‐James Jennifer E. , Daly M. de Burgh 
Published: December 2014

1. The effects on respiration and pulse interval of stimulation of the carotid body chemoreceptors before, during and after stimulation of receptors in the nose have been studied in the anaesthetized dog.2. Stimulation of a carotid body by infusion of cyanide into the ipsi‐lateral common carotid artery causes hyperpnoea and either an increase, decrease or no change in pulse interval.3. Excitation of receptors in the nasal mucosa leads to reflex apnoea or a reduction in breathing, and an increase in pulse interval.4. When the carotid bodies are excited by the same dose of cyanide during stimulation of the nasal mucosa, the chemoreceptor‐respiratory response is abolished or reduced in size compared with the control effect. On the other hand, the chemoreceptor‐cardio‐inhibitory response is considerably enhanced.5. The potentiated cardio‐inhibitory response of combined chemoreceptor and nasal stimulation could not be accounted for by the change in pulmonary ventilation, arterial PO2 or PCO2, or mean arterial blood pressure.6. These results indicate that excitation of the nasal reflex inhibits the chemoreceptor‐respiratory reflex response but facilitates the chemoreceptor‐cardio‐inhibitory reflex response. The possible sites of these interactions between the nasal and chemoreceptor reflexes are discussed.
Determination of the frequency response of isometric soleus muscle in the cat using random nerve stimulation
Authors: Mannard Allan , Stein Richard B. 
Published: December 2014

1. The frequency response of isometric soleus muscle was determined efficiently by analysis of the unfused tension generated during short periods of random stimulation of the divided ventral roots, in anaesthetized cats.2. Despite the complexities of skeletal muscle, the frequency response of soleus, at moderate lengths and stimulation rates in the physiological range, is closely approximated by the frequency response function for a simple, linear, second‐order system near critical damping.3. The soleus muscle shows a uniformly high sensitivity to fluctuations in nerve activity over a range of frequencies similar to the range of frequencies of muscular activity observable during behaviour. The nerve‐muscle preparation appears to be well suited for smooth and steady motor activity, since it is much less responsive to the higher frequency components contained in individual action potentials or generated in tremor.4. The second‐order parameters: low‐frequency gain, natural frequency and damping ratio provide useful descriptions of the changes in the muscle's response caused by variations of muscle length, nerve stimulation rate or number of active motor units.5. A reduction in tension incurred, for example, during fatigue can be compensated to some extent either by a lengthening of the loaded muscle or through an increase in neural spike repetition rate. However, both mechanisms produce concomitant increases in the ‘sluggishness’ (increased damping and lower natural frequency) of the preparation. This sluggishness may arise out of limitations imposed by the mechanism for the re‐uptake of calcium into the sarcotubular system.6. One naturally occurring method of increasing tension, by recruitment of more active motoneurones, seems to be desirable because tension can be augmented in this way without an increase in sluggishness. This is presumably because recruitment increases the muscle's response without affecting excitation‐contraction coupling in fibres already active.
The effect of increasing the innervation field sizes of nerves on their reflex response time in salamanders
Authors: Stirling R. Victoria 
Published: December 2014

1. A simple quantitative measure was sought which could describe the relationship between reflex coupling in the spinal cord of salamanders and the peripheral innervation fields of the nerves from which the reflexes were elicited.2. In decerebrate salamanders reflex responses were recorded between pairs of cut hind limb nerves. The latencies (S/R times) of these reflex responses were bilaterally symmetrical for a given pair of nerves and were shorter when the stimulated nerve of the pair had a large motor and sensory peripheral limb innervation field; this was especially obvious for reflexes between 15th and 17th segmental nerves.3. After cutting or crushing the 16th nerve in adult salamanders, the adjacent 15th and 17th nerves sprouted collaterally to innervate denervated skin and muscle. There was apparently complete recovery of normal tactile reflexes and walking movements within a month.4. The operation did not affect the reflex response (S/R) times for nerve combinations on the unoperated side, which were not significantly different from those of normal animals with similar sized peripheral nerve fields. The unoperated side therefore represented the preoperative condition.5. In animals where one or both the 15th and 17th nerves had increased its innervation field size, the S/R times between them were significantly shorter on the operated side when the nerve with the enlarged field was stimulated. The degree of shortening was greatest for nerves showing the largest increase in peripheral field area.6. The S/R times between the 15th and 17th nerves were similar to those measured in normal animals in which the peripheral fields were of similar size to the enlarged fields in the operated animals. In a few cases where the increase in field size was considerable, the S/R time between the 15th and 17th nerves became as short as that between the 15th and 16th nerves on the control side.7. After removal of the 15th nerve, the 14th nerve sprouted into the trunk skin and muscle previously innervated by the 15th nerve and the 16th nerve into denervated limb skin and muscle. In spite of the increased peripheral fields of both these nerves, there was no change in the S/R times between them, or between any other pair of limb nerves on the operated side.8. The decrease in the S/R times between the 15th and 17th nerves was only observed where the stimulated nerve had increased its peripheral limb innervation field. The possible causes and significance of this shortening reflex response times are discussed in the context of an apparently functionally appropriate adaptation in the spinal cord.
Morphological identification and intrafusal distribution of the endings of static fusimotor axons in the cat
Authors: Barker D. , Emonet‐Dénand Françoise , Laporte Y. , Proske U. , Stacey M. J. 
Published: December 2014

1. Tenuissimus muscles of the cat were prepared in which the motor innervation was reduced to a single γ axon by cutting all the other motor axons and allowing them to degenerate during a period of 7–12 days. The function of the surviving γ axon was then determined, and the distribution of its endings ascertained in teased, silver preparations.2. In the ten muscles successfully prepared the function of the surviving γ axon was static and the motor innervation distributed to the spindles consisted of trail endings. The conduction velocities of the axons ranged from 33 to 48 m/sec.3. A detailed histological analysis was made of thirty spindles innervated by six of the surviving static axons.4. The six static axons distributed trail endings to both bag and chain muscle fibres in the poles of thirty spindles with about twice the frequency of supplying them to poles in which the distribution was restricted exclusively to one type of muscle fibre or the other.5. The density of trail innervation supplied to the bag fibres, in terms of the mean number of terminals per fibre, was typically from one and a half to twice that supplied to the chain fibres. On the other hand, whereas the number of bag fibres supplied with trail endings in a spindle pole was seldom more than one, the number of chain fibres innervated was usually two in a range of one to four.6. The possible effects that partial denervation might have had on the spindles are discussed, but it is concluded that they are unlikely to have affected the results.
Studies of the pulmonary vagal control of central respiratory rhythm in the absence of breathing movements
Authors: Bartoli A. , Bystrzycka Ewa , Guz A. , Jain S. K. , Noble M. I. M. , Trenchard Diana 
Published: December 2014

1. Breuer's hypothesis that the vagus nerves exert a tonic control of respiratory rhythm, in addition to the phasic control, was examined.2. Closed‐chest cardiopulmonary bypass was instituted in dogs weighing 20–30 kg anaesthetized with chloralose. Respiratory rhythm was recorded from a phrenic electroneurogram.3. Complete muscular paralysis induced with gallamine triethiodide produced an increase in the duration of inspiration and an increase in the amplitude of the integrated phrenic electroneurogram. There was no consistent effect on expiratory duration. Gallamine produced no effect when given after vagotomy.4. In the paralysed state, an increase in lung volume of 25–100 ml. for 30–60 sec produced a sustained increase in the duration of expiration and a decrease of respiratory rate: there was little effect on inspiratory duration, or the amplitude of the integrated phrenic electroneurogram.5. A decrease in lung volume of the same order of magnitude for the same period produced a sustained decrease in the duration of expiration and an increase of respiratory rate: there was little effect on inspiratory duration or the amplitude of the integrated phrenic electroneurogram.6. The phenomena described in (5) and (6) constitute a high gain respiratory frequency controller. They did not occur after bilateral cervical vagotomy.7. Bilateral cervical vagotomy during complete muscular paralysis produced a further increase in the duration of inspiration and in the amplitude of the integrated phrenic electroneurogram; there was no consistent effect on expiratory duration.8. The results confirmed Breuer's hypothesis and showed that inspiratory duration and expiratory duration are controlled independently.
The interaction of calcium and strontium with phosphatidyl serine in the anaphylactic secretion of histamine
Authors: Foreman J. C. , Mongar J. L. 
Published: December 2014

1. Spontaneous histamine release from isolated mast cells was found to be independent of calcium in the concentration range up to 1 m‐mole/l. Phosphatidyl serine did not change the effect of calcium on spontaneous release.2. Spontaneous histamine release was found to vary with the strontium ion concentration. Graded increase in the release occurred as the concentration of strontium was raised from 1 to 10 m‐mole/l. Phosphatidyl serine potentiated this action of strontium; the potentiation showed a graded increase as the phosphatidyl serine concentration was raised from 1 to 100 μg/ml.3. The activation of anaphylactic histamine release by calcium was potentiated by phosphatidyl serine; the degree of potentiation showed a graded increase as the calcium concentration was raised from 0·1 to 1·0 m‐mole/l.4. The activation of anaphylactic histamine release by strontium showed little, if any, potentiation by phosphatidyl serine.5. The response of the mast cells, in terms of anaphylactic histamine release, to calcium, in the presence of optimal concentrations of phosphatidyl serine, was found to be similar to that observed in the presence of strontium alone.6. These observations are discussed in terms of the concepts of affinity and efficacy of the ions at their receptor sites.