bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of non‐myelinated vagal afferent fibres from the lungs in the genesis of tachypnoea in the rabbit
Authors: Guz A. , Trenchard Diana W. 
Published: December 2014

1. The use of a direct current (d.c.) to produce a differential block of conduction in the cervical vagus nerves of rabbits is described; the myelinated fibres are blocked, while the non‐myelinated ‘C’ fibres conduct normally. The method produces reproducible and reversible results.2. The block is equally effective for low and high frequencies of discharge (1–100 Hz). During recovery or development of the block, lower frequencies of discharge can pass but higher frequencies cannot.3. Block of conduction in myelinated fibres is associated with slower, deeper breathing, confirming previous work with cooling.4. A further slowing and deepening of breathing may occur when a differentially blocked (‘non‐myelinated’) nerve is sectioned, and this is mainly apparent when there are pathological conditions in the lungs.5. The respiratory response to the right atrial injection of phenyl diguanide is mediated by non‐myelinated thoracic vagal afferent fibres.6. The tachypnoeic response to lung deflation is not mediated by non‐myelinated fibres.7. Head's Paradoxical reflex has been demonstrated during partial recovery of conduction in myelinated fibres when only lower frequencies of afferent discharge can pass the area of block.8. A standard technique for providing a reproducible vagally mediated, tachypnoeic response to pulmonary micro‐embolism is described using inert carbon‐coated microspheres of 50 μm diameter. This tachypnoeic response was unchanged during a differential block indicating that the response was mediated by non‐myelinated ‘C’ fibres.9. Pathological changes such as haemorrhage, oedema, infarction and collapse were absent after micro‐embolism, and there were no systematic changes in lung resistance and compliance. The walls of arterioles and adjacent alveoli are distorted by the emboli and these areas are the probable sites of afferent stimulation.
The membrane potential and permeabilities of the L cell membrane to Na, K and chloride
Authors: Lamb J. F. , MacKinnon M. G. A. 
Published: December 2014

1. The chloride content and fluxes, and the membrane potential of L cells have been measured.2. L cells contain chloride, 70 m‐mole/l. intracellular water and have a flux of 5·5 p‐mole/cm2 sec.3. The membrane potential is −15 mV.K‐free Krebs causes an increase in Em and replacing chloride with sulphate causes a temporary reduction in Em.4. These values for Em and chloride, and previously obtained values for Na and K fluxes and contents were used to calculate the permeabilities of the various ions using the Goldman constant field theory. This gave permeabilities of 6·3, 4·2 and 51 × 10−9 cm/sec for K, Na and chloride respectively, a ratio of 1:0·67:8·10.5. It is concluded that these cells have a low membrane potential because the PK is some 100 times lower than in skeletal muscle, therefore leading to a PK of the same order as PNa.
Does curare affect transmitter release?
Authors: Auerbach A. , Betz W. 
Published: December 2014

1. The effect of curare on the amount of transmitter released by a nerve stimulus was studied in frog and rat nerve—muscle preparations using electrophysiological techniques.2. When the frog sartorius nerve—muscle preparation was exposed to low doses of curare, the amplitudes of spontaneous miniature end‐plate potentials and end‐plate currents (e.p.c.s, measured under ‘voltage clamp’ conditions) were reduced to the same extent, suggesting that the drug did not alter the number of transmitter quanta released by nerve stimulation.3. With higher doses of curare in frog muscle treated with glycerol to abolish twitching, quantum content was estimated from the coefficient of variation (CV) of e.p.c.s. The measured CV increased slightly in curare; this increase probably resulted from a relatively greater contribution of random noise to the observed fluctuations when the e.p.c. was reduced by curare.4. In the rat diaphragm, muscle fibres were cut to block twitching. This procedure produced, among other changes, a reduction in the muscle fibre space constant, so that junctional signals were distorted by the cable properties of the muscle fibre when, as often occurred, micro‐electrodes were more than 100–200 μ from the end‐plate focus. This produced errors in estimates of quantum content; when these errors were accounted for, it appeared that curare did not significantly alter quantum content.5. It is concluded that if curare affects transmitter release at all, its effect must be much smaller than its well known post‐synaptic blocking action.
The effects of altering mean pressure, pulse pressure and pulse frequency on the impulse activity in baroreceptor fibres from the aortic arch and right subclavian artery in the rabbit
Authors: James Jennifer E. Angell 
Published: December 2014

1. A method is described for perfusing an isolated preparation of the rabbit aortic arch with independently controlled mean pressure, pulse pressure and pulse frequency.2. Recordings made from single or few‐fibre preparations from the aortic arch and right subclavian baroreceptor regions show that the number of impulses per second or per cycle in a single fibre is the same during pulsatile perfusion as during non‐pulsatile perfusion if the pressure is above the threshold pressure to non‐pulsatile perfusion during all phases of the pressure cycle.3. In multi‐fibre recordings the total number of impulses is greater during pulsatile perfusion than during non‐pulsatile perfusion due largely to recruitment of fibres during systole.4. The relationship between instantaneous impulse frequency and aortic arch pressure during one pressure cycle forms an elliptiform curve.5. Increasing the pulse pressure increases the ellipse and causes additional recruitment of other fibres during systole, thus augmenting the total impulse activity.6. Increasing the pulse frequency reduces the number of impulses per cycle for single fibres but produces a small increase in the total impulse frequency in one second period due to recruitment.7. Increasing the rate of change of pressure by increasing the pulse pressure or pulse frequency produced a small reduction or no change of the threshold pressure. Similarly the ‘cut off’ pressure was elevated in some fibres.8. At low initial mean pressures, an increment of pressure, at constant pulse pressure and pulse frequency, increases the total impulse activity by increasing the frequency of impulses in single fibres already active during systole and diastole and by additional recruitment of other fibres. At higher mean pressures there is little increase in impulse activity as the maximum frequency of fibres is attained or superseded and there is little recruitment.
The lymphatics of the kidney and the formation of renal lymph
Authors: McIntosh G. H. , Morris Bede 
Published: December 2014

1. The anatomy of the renal lymphatics and the flow and composition of renal lymph have been investigated in sheep. Lymphatic capillaries were demonstrated in the cortex and cortico‐medullary areas of the sheep's kidney but not within the medulla. The lymph formed in the sheep's kidney drains from the hilum through several small lymphatics; there is no lymphatic drainage from the renal capsule.2. Lymph flow from the sheep's kidney varied from 0·5 to 3·0 ml./hr. The concentrations of electrolytes and urea in renal lymph were found to be similar to lymph from other regions of the body, but the concentration of endogenous creatinine was lower. The average concentration of protein in renal lymph was 43% of the plasma levels; there was a significantly higher proportion of albumin in renal lymph than in plasma. When labelled albumin was injected intravenously, the specific activities of the plasma and renal lymph albumin equilibrated in about 2 hr.3. When [14C]inulin, [125I]hippuran or [14C]creatinine were infused intravenously radioactivity appeared rapidly in the renal lymph. When steady‐state levels were reached in the circulating plasma, the renal lymph/jugular vein plasma ratios for [14C]inulin and [14C]creatinine were 0·82 while for [125I]hippuran the ratio was 0·34. It was considered that the concentration of these substances in renal lymph was similar to the concentration in renal vein plasma.4. The concentration of renin enzyme was on the average about 8 times higher in renal lymph than in jugular vein or renal vein plasma or in lymph from the hind limbs.5. Renal lymph appeared to be formed principally, if not entirely, in the renal cortex and appeared to be a modified filtrate derived from post‐glomerular blood capillaries. If any contribution to renal lymph does come from the medulla, it must be small in relation to the volume of lymph formed in the cortex.
The effect of variations in heart rate and regional distribution of blood flow on the normal pressor response to diving in ducks
Authors: Butler P. J. , Jones D. R. 
Published: December 2014

1. During a 2 min period of submersion of normal ducks, sciatic artery blood flow fell to 10 ± 1·5% control and carotid artery blood flow was reduced to 71 ± 7% control. Mean arterial blood pressure (
M.A.P.), however, was maintained at 83 ± 3·5% of control. The whole animal showed a constrictor response during submersion, with the sciatic vascular bed showing average constriction. Both resistance to flow and yield pressure increased in the sciatic bed but changed little in the carotid bed. After 1 min submersion Pa,O2 was 52 ± 1 mm Hg.2. Upon emersion, as soon as ventilation commenced, the whole animal showed a dilator response. The carotid bed exhibited marked vasodilatation whereas the sciatic bed returned to its control level.3. After α‐receptor blockade, ducks were submerged for 1 min. During this time
M.A.P. fell to 64 ± 5·6% of control and heart rate was reduced to 49 ± 8·3% of control. Blood flow through the sciatic and carotid arteries also fell to values of 41 ± 6·9% of control and 91 ± 13% of control respectively. There was little change in either resistance to flow or yield pressure in the sciatic bed compared to normal ducks, and the carotid bed showed reductions in resistance to flow and yield pressure during submersion. Pa,O2 after 1 min under water was 41 ± 1·1 mm Hg.4. β‐receptor blockade had no effect on any of the measured variables during submersion. Upon surfacing, however, although the whole animal response was one of dilatation, the carotid bed was less dilated than in normal ducks at this time and the sciatic bed was more constricted.5. Injection of atropine not only abolished the bradycardia during submersion but also caused a rise in
M.A.P. and sciatic blood flow during the period under water. After 1 min submersion Pa,O2 was 30 ± 1·2 mm Hg.6. It is concluded that stimulation of adrenergic α‐receptors is responsible for the increase in resistance to flow through the sciatic artery and the maintenance of blood pressure during submersion in the normal animals. This selective constrictor activity and the resulting ischaemia is important in the maintenance of Pa,O2 during submersion. Adrenergic β‐receptors (cardiac and/or peripheral) are involved, to a small extent, in the blood pressure and blood flow changes that occur when ventilation commences upon emersion.
An electrical description of the motoneurone, and its application to the analysis of synaptic potentials
Authors: Jack J. J. B. , Redman S. J. 
Published: December 2014

1. The Rall model of the motoneurone, which consists of a lumped resistance and capacitance, representing the soma, in parallel with a distributed resistance—capacitance network of finite length, representing the equivalent dendritic cable, has been used to investigate the effects of varying electrical and geometrical parameters on the time course of transients generated at the model soma.2. An analytical solution has been obtained for the voltage at the model soma, following a brief current injection at any point on the dendritic cable, in terms of the dendritic to soma conductance ratio, the electrotonic length of the cable, the membrane time constant, and the electrotonic distance between the point of current injection and the soma. This solution has been used to study the response at the soma to currents with a smooth time course, and to brief rectangular current pulses. Computations of these voltage transients are given to illustrate the effect of the above parameters on voltage time course.3. A method for determining the membrane time constant, the dendritic to soma conductance ratio, and the electrotonic length of the dendritic cable, is described. The method involves measurements from the decay time course of the transient at the soma following a brief current pulse being applied at the soma.4. A method is described whereby the time course of a synaptic potential, assumed to be generated by synaptic knobs located exclusively at the soma, may be used to determine the motoneurone parameters, and a parameter describing the time course of current injection.5. A method for estimating the distance between soma and origin of a non‐somatic synaptic potential, once the parameters of the motoneurone are known, is described.
Cardiovascular changes associated with skeletal muscle spasm in tetraplegic man
Authors: Corbett J. L. , Frankel H. L. , Harris P. J. 
Published: December 2014

1. A study has been made of the effect of spontaneous and induced muscle spasms on blood pressure, heart rate, hand blood flow, calf blood flow and occluded vein pressure in the hand and foot in non‐bedridden patients with chronic, closed, complete, localized transection of the cervical spinal cord.2. Both types of spasm produced a similar response consisting of an increase in blood pressure and occluded vein pressure and a decrease in heart rate and hand and calf blood flow. The changes commenced within 2‐3 sec and usually reached maxima in 20–30 sec. On some occasions there was a temporary initial increase in heart rate and calf blood flow.3. The changes occurred independently of changes in bladder pressure.4. It is concluded that the changes in peripheral blood vessels result from a spinal sympathetic reflex to somatic afferents associated with muscular contraction.
Spinal integration of segmental, cortical and breathing inputs to thoracic respiratory motoneurones
Authors: Aminoff M. J. , Sears T. A. 
Published: December 2014

1. The spinal integration of cortical, segmental and breathing inputs to thoracic motoneurones was studied in anaesthetized, paralysed cats: the breathing input was intensified by underventilation or abolished by hyperventilation.2. In apnoeic animals, low intensity stimulation of an internal intercostal nerve evoked a brief latency polysynaptic reflex discharge of expiratory motoneurones (direct response) in several adjacent segments with no or little response of the inspiratory motoneurones.3. A similar direct response of expiratory motoneurones occurred with brief tetanic stimulation of the trunk area in the contralateral sensorimotor cortex.4. Conditioning of an intercostal‐intercostal test reflex by a prior stimulus to an intercostal nerve or to the cortex gave conditioning curves showing facilitation of transmission to expiratory motoneurones at short intervals (5–25 msec) and inhibition at long intervals (25–200 msec).5. The direct response of expiratory motoneurones to the cortical or segmental inputs was depressed during the inspiratory phase when the animal was underventilated; conversely the spontaneous activity of the inspiratory motoneurones was inhibited for a period that corresponded with the direct response or to the phase of facilitated transmission to expiratory motoneurones. During the expiratory phase, the cortically or segmentally induced direct response was facilitated but the inhibition of inspiratory motoneurone activity was concealed by the absence of spontaneous activity.6. It was possible with discrete lesions of the spinal cord to differentiate between the pathways subserving the responses to cortical stimulation and the spontaneous activity due to the breathing input.7. To account for the results a working hypothesis is proposed utilizing a segmental interneuronal network which transmits mutual reciprocal inhibition between inspiratory and expiratory motoneurones.
The effect of tetanus toxin in the goldfish
Authors: Diamond J. , Mellanby Jane 
Published: December 2014

1. The effects of tetanus toxin have been investigated both on central nervous and peripheral neuromuscular systems of goldfish.2. Tetanus toxin kills goldfish when administered in minute doses. The lethal effect is temperature dependent. Unlike mammals, in which tetanus toxin produces spastic paralysis and convulsions, the tetanus‐intoxicated goldfish die with an apparently flaccid paralysis.3. Inhibition and excitation were investigated on the Mauthner cells of goldfish which had been paralysed with tetanus toxin for at least 24 hr, and which were subsequently kept alive for up to 3 days by perfusing the gills with oxygenated water. In such fish, antidromically and orthodromically excited Mauthner cells were quite normal, and there was no apparent effect on either the collateral inhibition or the crossed VIIIth nerve inhibition.4. Local injection of sublethal doses of tetanus toxin into the pectoral fin muscles produced local paralysis of the fin. Nerve—muscle preparations were isolated from such goldfish; in tetanus toxin‐paralysed fins, the muscle no longer responded to stimulation of its nerve. The nerve compound action potential was still present and the muscle still responded vigorously to direct electrical stimulation.5. It is concluded that the major part of the lethal action of the toxin in the fish must be ascribed to a peripheral effect, the blocking of neuromuscular transmission. The inhibitory neuronal systems acting on the Mauthner cells of the goldfish, in apparent contrast to those acting on mammalian spinal neurones, are highly insensitive to tetanus toxin.
The mechanism of acetylcholine release from parasympathetic nerves
Authors: Paton W. D. M. , Vizi E. S. , Zar M. Aboo 
Published: December 2014

1. The output of acetylcholine from the plexus of the guinea‐pig ileum longitudinal strip has been used to study the mechanism of acetylcholine release. From the effects of hexamethonium and tetrodotoxin, it was inferred that 60% of the normal resting output is due to propagated activity in the plexus, and 40% to spontaneous release. Tetrodotoxin virtually abolishes the increase in output in response to electrical stimulation.2. Resting acetylcholine output is increased when the bathing medium is changed in the following ways:(a) sodium replacement by sucrose, trometamol or lithium;(b) addition of ouabain or p‐hydroxymercuribenzoate (PHMB), or withdrawal of potassium;(c) the combination of PHMB and partial sodium replacement;(d) addition of potassium; this increase in output becomes greater in the absence of sodium.3. The resting output is virtually abolished by calcium withdrawal, and is restored by barium substitution for calcium. It is also reduced by raising the magnesium concentration.4. The enhanced resting output in response to sodium withdrawal also occurs in the absence of calcium.5. Cooling to 5° C greatly reduces both the resting output and the output in response to raised potassium concentration or to electrical stimulation.6. The increase in resting output due to potassium excess is slight up to 25 m
M [K+]o, but increases thereafter with about the fourth power of the potassium concentration; it is resistant to tetrodotoxin.7. Synthesis of acetylcholine by the longitudinal strip is increased when output is enhanced by electrical stimulation, by potassium excess or by addition of barium, so that the acetylcholine content of the strip is maintained approximately normal. Synthesis is reduced, in relation to output, by potassium lack or by treatment with ouabain, and is virtually abolished by sodium withdrawal.8. The theory is discussed that acetylcholine release depends on inhibition of the activity of a (Na+ + K+ + Mg2+)‐activated ATPase at the axonal membrane.
Synaptic transmission in the superior cervical ganglion of the cat after reinnervation by vagus fibres
Authors: Ceccarelli B. , Clementi F. , Mantegazza P. 
Published: December 2014

1. A vagus‐sympathetic anastomosis was performed in the cat by connecting end to end the cranial trunk of the vagus to the cranial end of the cervical sympathetic trunk, both severed under the ganglia.2. Forty to sixty days after the anastomosis, the ocular signs of sympathetic paralysis (such as myosis and prolapse of the nictitating membrane) which had developed shortly after the operation, had completely disappeared, thus suggesting the recovery of synaptic transmission in the ganglion. In case of plain preganglionic denervation after the same period the ocular signs of cervical sympathetic paralysis were still present.3. Contraction of the nictitating membrane could be induced by electrical stimulation of both the vagus preanastomotic and the sympathetic postanastomotic—preganglionic trunks. Ganglionic blocking agents induced the blockade of the ‘new’ ganglionic synaptic function, while nicotine and pilocarpine provoked a marked contraction of the nictitating membrane.4. Electron microscopy showed that the preganglionic regeneration of vagus fibers resulted in the formation of new synapses, mainly of axodendritic type, identical to normal ganglionic synapses. Moreover, after cutting the preanastomotic trunk of the vagus, these new ganglionic presynaptic profiles degenerated, thus proving their vagal origin.5. During restoration of the synaptic contacts readjustment of dendritic tips occurred.
The function of the paramedian reticular nucleus in the control of heart rate in the cat
Authors: Calaresu F. R. , Thomas M. R. 
Published: December 2014

1. Selective electrical stimulation of the paramedian reticular nucleus (PRN) in anaesthetized and decerebrate‐anaesthetized cats elicited cardiac slowing which was shown to be due to inhibition of the sympathetic input to the heart.2. In decerebrate preparations stimulation of the PRN elicited cardioacceleration which was abolished by bilateral vagotomy.3. It is suggested that these changes in heart rate in opposite directions can be accounted for by an inhibitory influence of the PRN on both neural inputs to the heart. In the absence of vagal activity, demonstrated in anaesthetized and decerebrate‐anaesthetized preparations, the response to stimulation of the PRN resulted in cardiac slowing. In contrast, when both sympathetic and parasympathetic pathways were active (decerebrate preparation) stimulation of the PRN resulted in cardio‐acceleration, due to simultaneous inhibition of the two neural inputs to the heart.4. It is concluded that the two inhibitory functions of the PRN are probably mediated by two different populations of neurones and that the PRN plays an integrative role in the medullary control of heart rate.
Age changes in cross striated muscle of the rat
Authors: Gutmann E. , Hanzlíková V. , Vyskočil F. 
Published: December 2014

1. Senile muscle atrophy is characterized by a marked reduction in the frequency of spontaneous transmitter release with no electrophysiological evidence of denervation.2. In spite of the reduced number of muscle fibres, there is no ultrastructural evidence for denervation at the end‐plates. There is agglutination of synaptic vesicles, neurotubules and filaments, thickening of the basement membrane, widening of the primary synaptic cleft, and irregular branching of the junctional infoldings, but no axonal degeneration.3. The contractile process in senile muscles is slowed down as is indicated by a prolongation of contraction time, latency period, maximum rate of twitch tension and relaxation time.4. The muscle fibres show proliferation of the T system and increased SR but no fragmentation as is observed in denervation atrophy.5. Senile muscle atrophy thus presents some specific features affecting both pre‐ and post‐synaptic structures, related to a very slow process of deterioration of the neuromuscular contact.