bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intracellular recording from spinal motoneurones in cats with post‐asphyxial rigidity
Authors: Collewijn H. , Van Harreveld A. 
Published: December 2014

1. Intracellular recordings were obtained from lumbar spinal motoneurones in cats with post‐asphyxial rigidity of the hind limbs.2. Membrane potentials, latencies and (or) appearance of excitatory post‐synaptic potentials, initial segment responses and soma‐dendritic spikes were not materially different from those observed in cells of normal cords.3. Dorsal root stimulation activated all the motoneurones examined through monosynaptic pathways in contrast to cells in normal cords in which such a stimulus sometimes elicits only a post‐synaptic potential. In a number of cells subsequent polysynaptic activation caused a spike about 10 msec after the monosynaptic response, notwithstanding the serious interneuronal destruction which characterized these preparations.4. In a few preparations the effects of acute asphyxiation could be examined. The soma depolarized at a rate of 3‐4 mV/min. Synaptic activation was more resistant to O2 lack than antidromic and direct excitation, in contrast to the experience with normal cells. Survival times of 8·5, 11 and 16 min were found. At certain levels of depolarization ‘spontaneous’ spikes were observed, which, since they were preceded by post‐synaptic potentials, could be considered as the result of synaptic activation.5. To account for the enhanced reflex activity of rigid preparations, it was postulated that the substantial loss of interneurones in the cord had caused denervation supersensitivity of the motoneurones to the transmitter compound without materially changing their electrical excitability.6. It was postulated that the early presynaptic failure during asphyxiation in normal preparations was dependent on a mechanism resembling presynaptic inhibition. The prolonged asphyxial survival of reflex activity in rigid preparations may be due to the destruction of interneurones involved in this form of inhibition.
Respiratory and circulatory effects of breathing 100% oxygen in the new‐born lamb before and after denervation of the carotid chemoreceptors*
Authors: Purves M. J. 
Published: December 2014

1. Methods are described for measuring tidal volume and frequency, end‐tidal CO2, blood pressure and heart rate, and arterial gas tensions in the unanaesthetized new‐born lamb.2. The resting values of minute ventilation (V̇)/kg body wt. and arterial oxygen and carbon dioxide tension, (Pa, o2) and (Pa, CO2) were similar to those which have been reported in the new‐born baby. There was a direct and significant relation between Pa, o2 and Pa, CO2 and the age of the lamb.3. Thirty‐five unanaesthetized lambs aged 40 min to 10 days breathed 100% oxygen; minute ventilation fell by an average of 19% of control, end‐tidal CO2 increased and the ratio of change in tidal volume (ΔVT) to change in pressure (ΔP) (ΔVT/ΔP) remained constant. In a proportion of lambs, a small decrease in blood pressure and heart rate was observed. The effect of breathing 100% O2 on lung compliance was variable.4. These changes in ventilation were virtually abolished after both sinus nerves had been cut.5. The results therefore suggest that a significant hypoxic drive to ventilation exists in the new‐born lamb and that this drive is mediated by functioning and mature peripheral chemoreceptors.6. Preliminary evidence suggested that, on 100% O2, the sensitivity of new‐born lambs to inhaled CO2 was reduced.
The respiratory response of the new‐born lamb to inhaled CO2 with and without accompanying hypoxia*
Authors: Purves M. J. 
Published: December 2014

1. The respiratory response to inhaled CO2 was measured in twenty unanaesthetized new‐born lambs aged 4 hr‐10 days. Measurement of resting arterial pH, PCO2 and plasma bicarbonate showed a non‐respiratory acidosis immediately after birth which was corrected in the first 24‐28 hr: thereafter, the acid—base pattern was of a compensated respiratory alkalosis.2. When CO2 was added to the inspired gases and resting arterial oxygen tension (Pa, O2) was controlled, the average increase in minute ventilation (V̇) was 0·075 l.min−1.kg−1.mm Hg, Pa, CO2−1 and duplicate responses in the same lamb differed by 6‐22·5%.3. The slope of the V̇/Pa, CO2 line (S) varied inversely with Pa, O2. In one lamb, severe hypoxia (Pa, O2 = 21 mm Hg) caused a marked depression of the slope.4. Neither the slope S nor the horizontal intercept B of the lines was related to the age of the lamb. B was not related to pHa and only slightly affected by acute hypoxia. B was related to arterial [HCO3−] and values for both were reduced with the acid—base disturbances seen in the first 10 days after birth. Evidence was given which suggested that the response of the new‐born lamb to inhaled CO2 was similar to that of man acclimatized to a Pa, O2 of 70‐75 mm Hg.5. In the lightly anaesthetized lamb, bilateral section of the sinus nerves caused a small reduction in the sensitivity to inhaled 5% CO2 in air, an increase in the respiratory lag and a reduction in the rate at which V̇ increased.6. It was concluded that, in the new‐born lamb, the carotid chemo‐receptors are involved in the response to inhaled CO2 and that hypoxia potentiates this response.
Competition between sodium and calcium ions in transmitter release at mammalian neuromuscular junction
Authors: Gage P. W. , Quastel D. M. J. 
Published: December 2014

1. Frequencies of miniature end‐plate potentials (m.e.p.p.s) were recorded at neuromuscular junctions in rat diaphragm‐phrenic nerve preparations in vitro.2. In the presence of raised [K] (15‐20 m
M) lowering [Na] caused a rapid increase in m.e.p.p. frequency whether [Ca] was low or normal. Raising [Na] towards the normal concentration (162 m
M) caused a slow fall in frequency and raising [Ca] in the range 0·32‐2 m
M caused a slow increase in frequency. These effects were less in the normal [K] (5 m
M).3. Mean m.e.p.p. frequencies were determined for solutions containing 15 m
M‐K and combinations of [Ca] and [Na]. M.e.p.p. frequency varied inversely with [Na] when [Ca] was constant. In each of the three Na concentrations used (162, 113 and 65 m
M) raising [Ca] in the range 0·32‐2 m
M increased m.e.p.p. frequency but when raised above 2‐3 m
M, Ca depressed frequency.4. A model was proposed in which Ca affected transmitter release by changing the concentration in the presynaptic membrane of a complex CaX to which the rate of transmitter release was directly proportional. Higher concentrations of Ca depressed transmitter release by inactivating CaX. Sodium ions competitively depressed release either by competing with calcium ions for association with X or by reducing the affinity of X for Ca.5. When [Na] was lowered in solutions containing raised [Mg] and [Ca], the increase of mean m.e.p.p. frequency was greater than that observed in raised [Ca] and normal [Mg] and was of the same order as the increases seen in low [Ca]. The result was interpreted to indicate either that Na and Mg do not compete with Ca at the same site or that Mg affects the affinity of X for Ca and Na.6. The effect of lowering [Na] on m.e.p.p. frequency was a specific effect of Na ions. When LiCl was substituted for NaCl, the increase of m.e.p.p. frequency persisted. Changes in [Cl] had no effect on m.e.p.p. frequency.7. There was a linear relation between the mean logarithm of m.e.p.p. frequencies and [K], the slope of the relation increasing as [Na] was lowered. Conversely, lowering [Na] caused a greater increase in m.e.p.p. frequency as [K] was raised.8. The variation of m.e.p.p. frequencies in a diaphragm was roughly proportional to a second or higher power of [Na] and inversely proportion to [Ca]. It was thought that this could be due to differences in chelation of Ca which were more apparent at low Ca concentrations.9. The similarities between the effects of Na, Ca and K on m.e.p.p. frequency and the effects of these ions on Ca‐influx in heart muscle led to the suggestion that transmitter release is proportional to the concentration of a negatively charged complex of a carrier X with one calcium ion (CaX) at the internal surface of the membrane and that changes in membrane potential affect transmitter release by changing the distribution or location of CaX in the membrane.
An examination of the evidence for membrane pores in frog skin
Authors: Dainty J. , House C. R. 
Published: December 2014

1. Measurements of the diffusional permeability, Pd, of tritiated water in isolated frog skin bathed in sulphate Ringer have been made under different stirring conditions.2. The mean ±
S.E. values for Pd were found to be (6·5 ± 0·3), (7·9 ± 0·5), (9·7 ± 0·7) and (11·1 ± 0·8) × 10−5 cm sec−1 at 120, 300, 500 and 1000 rev/min. It is considered that these results indicate the existence of ‘unstirred layers’ associated with frog skin.3. The hydraulic conductivity, Lp, of the skin in sulphate Ringer was found to be (2·36 ± 0·07) × 10−7 cm sec−1 atm−1 (±
S.E. of estimate), and no marked increase in this value for Lp was found when the stirring rate was increased from 0 to 500 rev/min.4. It is considered that these results show that previous comparisons of the relative magnitudes of LpRT/V̄w (where V̄w is the partial molar volume of water) and Pd for frog skin have been in error because of the presence of ‘unstirred layers’.5. The bearing of our results and other evidence on the question of pores in cell membranes has been discussed.
Skin histamine in cats: its depletion and subsequent recovery after injection of compound 48/80
Authors: Waton N. G. , West G. B. 
Published: December 2014

1. The histamine content of the skin has been determined in untreated cats, in cats injected with the histamine liberator, compound 48/80, and in cats injected subcutaneously with an oily suspension of histamine or histidine after treatment with compound 48/80.2. Skin histamine in cats varied from 2·2 to 37·5 μg/g. Apart from regional variations in the histamine content of the abdominal skin, lower values were obtained from cats kept on a laboratory diet which included aureomycin (mean 8·5 μg/g, range 2·2‐13·1) than from cats on a high protein diet without aureomycin (mean 17·5 μg/g, range 5·2‐37·5).3. Compound 48/80 caused a depletion of skin histamine which was never complete, and a residue of 3‐7% remained; in cats which originally had a low histamine content of skin, depletion was even less and up to 20% of the original histamine remained.4. Recovery of skin histamine in cats after injections of compound 48/80 was slow, at least 110 days being required for full restoration. The rate of recovery was not altered by daily subcutaneous injections of histidine, but an effect was found with daily subcutaneous injections of histamine. Histamine had no effect for the first 33 days, but at 55 days the percentage histamine content of the skin was greater than in the cats treated with histidine or the oily suspending vehicle, and at 110 days the histamine content was not only much greater than the other two groups but was greater than that before injection of compound 48/80.5. No in vitro histamine formation was detected in the skin samples either before compound 48/80 treatment or at any time during the subsequent recovery of the histamine to control levels.6. The results support the theory that the histamine found in skin tissues of the cat is not formed there but is taken up from the blood stream.
The inhibitory action of noradrenaline and other monoamines on spinal neurones
Authors: Engberg I. , Ryall R. W. 
Published: December 2014

1.
L‐Noradrenaline (NA), 5‐hydroxytryptamine (5‐HT) and acetylcholine (ACh) were administered micro‐electrophoretically to feline lumbar neurones while recording their spike potentials extracellularly.2. There was no evidence to suggest that NA acts as an excitatory transmitter in the spinal cord.3. NA had potent inhibitory effects on some interneurones as revealed by a depression of spontaneous and synaptic firing and on the firing to a local application of an excitant amino acid. The effects on Renshaw cells and motoneurones were less marked.4. The depressant actions of 5‐HT were less marked than those of NA. ACh and carbamylcholine had depressant effects on some NA‐sensitive interneurones but were invariably far less potent and on other NA‐sensitive cells were completely inactive.5. NA had no detectable effect on the normal spike amplitude but when the action potentials were reduced by excessive depolarization then both NA and synaptic inhibition increased the spike amplitude; this effect could be due to a hyperpolarization of the cell membrane.6. There was a correlation between the distribution of NA‐sensitive cells and the relative densities of NA‐containing terminals in various layers of the grey matter.7. It was postulated that NA acts as an inhibitory transmitter released from the terminals of descending pathways in the spinal cord. Other possible mechanisms were discussed but lacked experimental support.
Observations on the isolated foetal sheep with particular reference to the metabolism of glucose and fructose
Authors: Alexander D. Pauline , Britton H. G. , Nixon D. A. 
Published: December 2014

1. Isolated sheep foetuses of 72‐146 days conceptual age (155‐4840 g) have been maintained for periods up to 325 min on an artificial circuit where the placenta has been replaced by an oxygenator.2. Measurements made during the period of observation included heart rate, femoral arterial pressure, umbilical blood flow, blood gases and pH; plasma and urine concentrations of glucose, fructose, lactic acid, urea, α amino nitrogen and electrolytes.3. The circulatory, metabolic and renal conditions of the isolated foetus were found to be similar to those of the exteriorized foetus with intact placental connexions. However, in the later stages a terminal hypoxia developed. This was due to a progressive diminution in umbilical blood flow caused by umbilical arterial constriction.4. The young foetuses removed glucose from the circulation and seemed unaffected by the consequent hypoglycaemia. If the glucose removed was completely oxidized it would account for much of the estimated oxygen consumption. The blood glucose concentration in the older foetuses, on the other hand, did not fall and sometimes rose. Renal excretion of glucose was very small.5. Fructose was usually slowly removed from the circulation and under no conditions did a rapid removal occur. Renal excretion accounted for about half of the fructose disappearing from the apparent fructose space. It is therefore suggested that a small utilization of fructose occurs in foetal tissues but this could account for only a very small fraction of the estimated oxygen consumption.
Release of vasopressin and oxytocin from isolated pituitary glands of adult and new‐born rats
Authors: Dicker S. E. 
Published: December 2014

1. Pituitary glands of adult rats of both sexes, of lactating female and of new‐born rats, incubated in a Locke solution, release both oxytocin and vasopressin. The amount of hormones released, during a measured period of incubation, is related to the actual hormone content of the gland.2. Increasing the concentration of KCl in the incubation medium, with CaCl2 present and in concentration of at least 2·2 m
M, produces an enhanced release of both hormones from pituitary glands of adults, but does not affect the release of hormones from glands of new‐born animals.3. Addition of ouabain to the incubation medium produces a marked increase of the release of the hormones from glands of both adult and new‐born rats. This is accompanied by an extrusion of K ion and an influx of Na ion. The effect of ouabain on the hormone release and the shift of ions can be reversed by subsequent addition of adenosine triphosphate.4. The increased release of hormones produced by ouabain, in glands from new‐born rats, is unaffected by the presence or absence of CaCl2. In adults, however, the effect of ouabain, though present, is reduced in the absence of CaCl2.5. It is suggested that in glands from adult animals, the hormones must be freed from their attachment on the protein‐carrier, neurophysin and that this can be achieved by the entry of calcium ion into the cell. The subsequent secretion of the ‘freed’ hormones appears to be accompanied by a shift of ions across the cell membrane.6. In glands from neonates up to 3 weeks old, the absence of neurophysin, or its poor capacity for binding the hormones, explains the inability of calcium to operate in the same way as in the glands of adults. There is evidence suggesting that the secretion of the neurohypophysial hormones in the new‐born animal consists mainly of their diffusion from the cells, without previous elution of the hormones as in adults.
An excitatory action of adrenaline, noradrenaline, and 5‐hydroxytryptamine on the spinal cord
Authors: E Silva M. Rocha , Sproull D. H. 
Published: December 2014

1. Fasciculation was produced in the trapezius and sternomastoid muscles of anaesthetized cats by adrenaline, noradrenaline and 5‐hydroxytryptamine (5‐HT) put into the cisterna magna. Isoprenaline, similarly applied, was ineffective.2. Each of the three active amines was without effect when applied for a second time after the fasciculation in response to the first application had passed off, but 5‐HT was effective after adrenaline and, similarly, adrenaline after 5‐HT.3. Fasciculation produced by adrenaline, but not by 5‐HT, was inhibited by ergotamine or phenoxybenzamine, given intravenously.4. In producing fasciculation, the adrenaline appeared to be acting on or through the lateral aspect of the upper cervical cord, about the line of emergence of the roots of the spinal accessory nerve, mainly in C1 and C2.5. The electromyograms of the fasciculation due to adrenaline and 5‐HT showed intermittent bursts of activity. After adrenaline, the bursts consisted of fewer spikes than after 5‐HT. The intervals between consecutive spikes were 3·75‐5 msec after either amine, and the bursts occurred irregularly, at frequencies between 7 and 12/sec.6. It is suggested that adrenaline and 5‐HT have excitatory actions on the dendrites or somata of the spinal accessory motor neurones, and the possible role of these amines as synaptic transmitters in the spinal nucleus of the accessory nerve is discussed.
Presynaptic inhibition evoked by muscle contraction
Authors: Devanandan M. S. , Eccles Rosamond M. , Stenhouse D. 
Published: December 2014

1. Contractions of flexor and extensor muscles of the knee and ankle were used to investigate presynaptic inhibition at the spinal level.2. Contractions evoked dorsal root potentials, and increased the excitability of the central terminals of group Ia, Ib and low threshold cutaneous primary afferent fibres.3. The monosynaptic reflexes recorded in response to stimulation of flexor or extensor muscle nerves were depressed, in the presence of strychnine hydrochloride 0·1 mg/kg
I.V., by the contractions.4. It is suggested that these presynaptic inhibitory effects are largely due to the activation of Golgi tendon organs by contraction.
The origin of the glucose dependent increase in the potential difference across the tortoise small intestine
Authors: Wright E. M. 
Published: December 2014

1. Experiments were carried out to investigate the origin of the glucose dependent increase in the potential difference (p.d.) across the isolated intestinal mucosa of the tortoise.2. In addition to glucose, galactose, α‐methyl glucoside, 3‐0‐methyl glucopyranose and sucrose also increased the transepithelial potential difference. There was no increase with either fructose or mannose.3. The use of micro‐electrodes demonstrated that the change in the p.d. due to the presence of glucose was wholly accounted for by the increase in the p.d. across the serosal face of the epithelial cells.4. Diffusion potentials were produced across the isolated mucosa by varying the ionic composition of either the mucosal or serosal fluids. However, there was no reduction of the glucose dependent increase in the p.d. when the ionic concentration gradients across the serosal face of the cell were reversed.5. These results suggest that the increase in the p.d. associated with the active transfer of sugars across the small intestine was due to the presence of an electrogenic ion pump at the serosal face of the epithelial cell.
The inhibitory nerve fibres in the vagal supply to the guinea‐pig stomach
Authors: Campbell G. 
Published: December 2014

1. A comparison was made between the inhibitory responses of the isolated atropinized guinea‐pig stomach to stimulation of the vagus and to stimulation of the perivascular nerves.2. When low frequencies of stimulation were used, the vagi were more effective than the perivascular nerves in causing relaxation of the stomach.3. The responses to vagal stimulation were faster in onset than were the responses to perivascular nerve stimulation.4. Responses to perivascular nerve stimulation were abolished by low concentrations of bretylium, whereas responses to vagal stimulation were only slight reduced. Vagal responses were strongly reduced by higher concentrations of bretylium.5. Amphetamine relieved the blockade of perivascular nerve responses which was caused by bretylium, but never relieved the reduction of the vagal responses.6. It is argued that the vagal inhibitory fibres are not susceptible to ‘adrenergic neurone blockade’, the observed reduction of the responses being due to some other action of bretylium.7. These differences between the vagal and perivascular inhibitory innervations of the stomach suggest that the post‐ganglionic fibres in the vagal pathway and the intramural inhibitory nerves described in the guinea‐pig caecum are similar.
The effects of alteration of blood‐volume on the concentration of circulating angiotensin in anaesthetized dogs
Authors: Hodge R. L. , Lowe R. D. , Vane J. R. 
Published: December 2014

1. The blood‐bathed organ technique was used to assay the concentration of angiotensin in the blood of anaesthetized dogs.2. Alterations of blood volume caused inverse changes of angiotensin concentration owing to changes in the rate of generation of angiotensin which are probably due to changes of the rate of renin secretion.3. Haemorrhage of 14‐26 ml. blood/kg caused an increase of 0·25‐1·5 μg/min in the rate of generation and an increase of 0·1‐0·33 ng/ml. in the blood concentration of angiotensin.4. The changes of angiotensin generation rate were not due to changes of renal arterial or venous pressure. They were abolished by blocking the renal nerves with lignocaine; they showed a consistent inverse correlation with central venous pressure but not with systemic arterial pressure.5. It is concluded that changes of blood volume bring about changes of the rate of generation of angiotensin by a reflex mechanism the efferent limb of which involves the renal nerves. The afferent pathway remains to be elucidated, but the systemic baroceptors do not appear to be of primary importance.6. The renin‐angiotensin system is important in the homeostatic response to changes of blood volume.
The isolation of hyaluronic acid and chondroitin sulphate from kidneys and their reaction with urinary hyaluronidase
Authors: Dicker S. E. , Franklin C. S. 
Published: December 2014

1. Extracts of the cortex and the medulla of fresh kidneys from pigs, sheep and dogs were analysed for the presence of acid mucopolysaccharides.2. Acid mucopolysaccharides were found in the kidneys of the three species and were evenly distributed between cortex and medulla.3. The acid mucopolysaccharides isolated from either the medulla or the cortex of kidneys contained equal amounts of sulphated and nonsulphated fractions; these could be identified as chondroitin sulphate and hyaluronic acid, respectively.4. Urinary hyaluronidase was isolated from urine and estimated by means of turbidity measurements.5. Urine hyaluronidase depolymerizes the acid mucopolysaccharides extracted from either the cortex or the medulla of the kidneys from pig, sheep and dog.6. The enzymic activity of urine hyaluronidase could be expressed as units/mg of protein. The optimum pH activity of the enzyme is at about 4·0.