bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of an exteroceptive stimulus on the concentration of melanocyte‐stimulating hormone in the pituitary of lactating rats
Authors: Deis R. P. , Orias R. 
Published: December 2014

1. A study was made of the effect of an exteroceptive stimulus, produced by a team of lactating rats and of litters while suckling, on the pituitary melanocyte‐stimulating hormone (MSH) activity of a group of lactating rats.2. After being isolated for 9 hr from their litter, one group of lactating rats was killed after being allowed to nurse for 30 min, another group was subjected to the exteroceptive stimulus for 15 min and then killed. Control rats were killed after 9 hr of isolation from the litter without being subjected to either suckling or the exteroceptive stimulus.3. The group of rats which had suckled their young showed a pituitary MSH activity equal to 35 ± 2·29%, and the group exposed to the exteroceptive stimulus an activity equal to 59·5 ± 3·16% of that in the control animals.4. When deaf rats were used, only the suckled mother showed a decrease of the pituitary MSH activity which was similar to that obtained with the normal suckled mother, indicating that the exteroceptive stimulus depended on hearing for its effect.5. A light dose of sodium pentobarbitone was sufficient to block the effect of suckling and the auditory stimuli on the pituitary MSH activity.6. The role of the central nervous system in this phenomenon and the possibility that MSH is implicated in the process of lactation are discussed.
Thyroxine deiodination during cold exposure in the rat
Authors: Hillier A. P. 
Published: December 2014

1. The urinary radio‐iodide excretion following injection of [131I]thyroxine and tri‐iodothyronine is increased in acutely cold‐exposed, thyroidectomized rats.2. This cold response is demonstrable in animals which are fed or fasted or deprived of both food and water. Cold exposure does not increase the rate of urinary excretion of a tracer dose of radio‐iodide. It is concluded that cold exposure accelerates the rate of deiodination of both thyroxine and tri‐iodothyronine.3. It is confirmed that both adrenaline and noradrenaline administered in vivo can enhance the rate of thyroxide deiodination.4. The sympathetic blocking agents guanethidine and bethanidine reduce the extra deiodination of thyroxine induced by cold exposure. Bethanidine was also found to reduce the deiodination of tri‐iodothyronine during cold.5. There is a positive correlation between the deiodination of thyroxine and the urinary catecholamine excretion in the cold‐exposed but not the warm‐exposed rat.6. It is suggested that the enhanced deiodination during cold exposure is mediated by the release of noradrenaline from the sympathetic nervous system.
Cortical conditions for fused binocular vision
Authors: Burns B. Delisle , Pritchard R. 
Published: December 2014

1. The behaviour of twenty‐six single neurones has been studied in the visual cerebral cortex of the cat's neurologically isolated and unanaesthetized forebrain. In a separate series of experiments binocular vision was investigated in five human subjects.2. Units in the cat's brain were excited by two straight, light‐dark edges, projected independently, one upon each retina; these edges were given identical, artificial saccadic movements. The average response of neurones was measured from the post‐stimulus‐histogram (
P.S.H.), which provided the probability of unit‐discharge at various times after the pattern movement.3. A district within either eye‐field could usually be found, such that the saccadic movements of edges passing through this part of the field, caused maximal responses; this part of each field is termed the ‘representative district’. The most exciting orientations of the stimulating patterns were similar for both eyes. A cell excited by similarly oriented patterns, ‘aligned’ through the representative districts for each eye, exhibited dramatic spatial summation. Mutual inhibition between retinal inputs was never seen.4. The response of cortical neurones to such aligned patterns was always greater than that when one pattern was misaligned by displacement in either direction from its representative district.5. When the pattern in one eye was inverted, the cell gave less response to aligned than to misaligned patterns.6. Human subjects, viewing similar inverted patterns through a mirror stereoscope, could only obtain stable fusion with a 5 min arc misalignment of the optic axes.7. In other experiments, one eye of each subject was presented with a white rectangular bar upon a black background, while the other eye was excited by a similar black bar upon a white background. Stable fusion was reported, providing percepts of either one single low contrast bar or two neighbouring bars of high contrast. There was a range of relative pattern positions over which alignment of the eyes sought the former percept in preference to the high contrast pattern.8. These results are consistent with the hypothesis that the mammalian visual system maintains binocular fusion by continuously hunting those eye directions that provide the greatest local cortical responses to saccadic movements, restricted to the smallest possible areas of the visual cortex.
The relationship of energy expenditure and spontaneous activity to the aphagia of rats with lesions in the lateral hypothalamus
Authors: Morrison S. D. 
Published: December 2014

1. Lesions in the lateral hypothalamus of rats always produced an immediate increase in total energy expenditure. The increase was maintained for 24 hr or longer only in rats that became and remained aphagic. Rats that showed no recovery from the aphagia and were maintained by tube feeding showed a second, larger increase in metabolic rate after about 7 days.2. The increase in total energy expenditure was associated, initially, with almost continuous motor activity. With continued aphagia an abnormally differentiated pattern of activity appeared at the same time as the second increase in metabolic rate, and the compartment of energy attributable to activity remained high (34% as compared with 23% in normal rats). These changes were accompanied by a recovery of an instrumental response for food (lever pressing), of interest in offered foods and of grooming activity.3. Metabolic abnormality not attributable to activity was indicated by increased creatinine excretion of aphagic but not of hypophagic rats.4. Rats that recovered spontaneous feeding after aphagia returned towards a normal differentiated pattern of activity, with bursts of activity separated by periods of rest, but showed residual abnormality in creatinine excretion.5. The intimate association between increase of energy expenditure, abnormality of motor activity and the aphagia produced by lateral hypothalamic lesions is consistent with the hypothesis that motor incoordination or disorganization is a cause of the aphagia.
Ionic environment of neurones and glial cells in the brain of an amphibian
Authors: Cohen M. W. , Gerschenfeld H. M. , Kuffler S. W. 
Published: December 2014

1. Experiments were performed to determine the relative contribution of the blood plasma and of the cerebrospinal fluid (c.s.f.) to the ionic environment of neurones and glial cells within the brain of the amphibian Necturus maculosus.2. The concentrations in the blood plasma of untreated control animals were 99 ± 2 m
M for Na+ and 2·0 ± 0·1 m
M for K+. In the c.s.f. the corresponding values were 112 ± 2 m
M‐Na+ and 1·9 ± 0·1 m
M‐K+.3. By keeping animals in K+‐rich water it was possible to raise chronically the concentrations of K+ in the blood plasma up to almost 5 times the normal value, close to 9 m
M, while the c.s.f. concentration of K+ was only doubled, to about 4 m
M. This behaviour of Necturus, tending to keep the K+ in the c.s.f. low, resembles that of mammals.4. The membrane potential of glial cells in the optic nerve can be used as an accurate indicator for determining the K+ concentration in the intercellular spaces. Such determinations were made in vivo, and it was shown that the glial cells adjust their membrane potential to the changes of K+ concentrations in the c.s.f. and not to those of the blood plasma. In contrast, the membrane potential of skeletal muscle fibres changes according to the K+ concentration in the blood plasma.5. It is concluded that the cells within the optic nerve are surrounded by an ionic environment which corresponds to that of the c.s.f. and not to that of the blood plasma. The intercellular spaces are open and ions diffuse freely into them from the c.s.f. A homeostatic mechanism operates, keeping the ion concentrations around neurones and glia within a narrow range and relatively independent of large changes in the blood plasma. This may provide relative stability for the signalling system. Similarities between the optic nerve and other parts of the central nervous system in respect to their relation to c.s.f. and blood are discussed. It seems likely that the mechanisms which control the electrolyte concentrations are similar in Necturus and in mammals.
Diffusional resistance of the innermost layer of the placental barrier of the rabbit
Authors: Faber J. Job , Hart Frederick M. , Poutala Arnold C. 
Published: December 2014

1. The permeability of the endothelial cell layer of the foetal capillaries of the rabbit placenta was measured by the tracer‐dilution method. Isotopically labelled water, urea, chloride and sodium ions, and inulin were used. Radio‐iodinated human serum albumin served as reference tracer. The measurements were made in in situ placentas of 27‐29 days gestation of which the foetal circulation was perfused with homologous blood.2. The permeability of water was found to be 1·7 ml. min−1.g−1, the permeabilities of urea, chloride ions and sodium ions were in the range of 0·28‐0·42 ml. min−1.g−1 and the permeability of inulin was 0·053 ml. min−1.g−1. These values may be underestimates, particularly the value of water.3. The approximate maternal blood space, foetal blood space, and extravascular sodium space were determined in rabbit placentas of 27‐29 days gestation and found to be 0·16, 0·07, and 0·48 ml./g respectively.4. The permeabilities of the endothelial layer were compared to those published for the entire placenta and found to be far greater. The resistance to diffusion of the endothelial layer is only a small part of the total resistance to diffusion. Most of the resistance is localized in the syncytioand/or cellular trophoblasts.5. It was concluded that lipid insoluble molecules diffuse through the interstitial water spaces of the trophoblast in few, relatively wide channels but that diffusing water can make use of intracellular as well as extracellular paths.
The effect of infusions of plasma and of saline on the renal response to water‐loading in sodium‐depleted dogs
Authors: Coxon R. V. , Ramsay D. J. 
Published: December 2014

1. Infusion of 150 ml. of plasma to dogs acutely depleted of sodium chloride by peritoneal dialysis with glucose (5 g/100 ml.) does not restore their ability to respond by diuresis when given 2·5% body weight of water by mouth.2. Infusion of 300 ml. of saline (0·73g NaCl/100 ml.) to these animals results in a brisk increase in urinary flow.3. Infusion of 100 ml. of saline (0·73g NaCl/100 ml.) to sodium‐depleted dogs restores their ability to respond to a water‐load of 2·5% of body weight by diuresis.4. The results are discussed and a tentative explanation put forward.
Electrical activity observed in guinea‐pig olfactory cortex maintained in vitro
Authors: Richards C. D. , Sercombe R. 
Published: December 2014

1. Electrical recordings were made from a preparation of guinea‐pig olfactory cortex maintained in vitro.2. The response of the prepiriform area to a volley delivered to the lateral olfactory tract comprised a sharp negative deflexion upon which several positive notches were superimposed followed by a long‐duration low‐amplitude positive wave.3. Both the negative and positive waves were of maximal amplitude near the top surface of the preparation (the original cortical surface).4. Units recorded at depths of 250‐350 μ showed facilitation and latency variation. The latency distribution of these spikes was very similar to that of the positive notches observed on the surface of the slice.5. The surface observed negative waves were rapidly abolished by oxygen lack.6. The negative and positive waves have been tentatively identified as the extracellular manifestations of the excitatory post‐synaptic potentials (EPSPs) and inhibitory post‐synaptic potentials (IPSPs) occurring in the apical dendrites.7. Some spontaneous activity was observed in a proportion of the preparations studied.8. The evidence presented here strongly supports the contention that portions of the mammalian brain may be maintained in a satisfactory functional condition when isolated from the body, provided that they are maintained in a suitable environment. We believe that such preparations will prove very useful for physiological studies of the mammalian brain.
Effects of nerve cross‐union on fast‐twitch and slow‐graded muscle fibres in the toad
Authors: Close R. , Hoh J. F. Y. 
Published: December 2014

1. A method is described for resolving isometric tetanic tension developed by fast‐twitch and slow‐graded components of heterogeneous toad muscles. This makes use of the difference in threshold for excitation of low threshold nerve fibres which normally innervate the fast‐twitch muscle fibres and high threshold nerve fibres which innervate slow‐graded muscle fibres.2. The sartorius muscle contains only fast‐twitch muscle fibres whereas the posterior semitendinosus (PST) contains both fast‐twitch and slow‐graded muscle fibres, the latter contributing 10‐15% of the maximum isometric tetanic tension.3. Following surgical cross‐union of nerve to sartorius and PST muscles, both the fast‐twitch and slow‐graded muscle fibre components of the PST are reinnervated by low threshold nerves originally innervating sartorius fast‐twitch fibres, and sartorius fast‐twitch muscle fibres are reinnervated by both low threshold and high threshold nerves formerly supplying the fast‐twitch and slow‐graded muscle fibre components of the PST.4. The characteristic mechanical responses of fast‐twitch muscle fibres and slow‐graded muscle fibres were not transformed up to 134 and 200 days respectively following nerve cross‐union.5. PST nerve partially innervated the sartorius muscle whereas sartorius nerves completely innervated the PST muscle. Isometric tetanic tension declined markedly during repetitive indirect stimulation of cross‐innervated sartorius muscles, whereas the tetanic contractions of cross‐innervated PST showed a plateau of tension and resembled the response of normal muscles.6. Normal, cross‐innervated and self‐innervated PST muscles gave sustained contractures in the presence of acetylcholine whereas PST muscles denervated for 120 days gave phasic contractures similar to those of normal, cross‐innervated and self‐innervated sartorius muscles.
Conduction velocity in proximal and distal portions of forelimb axons in the baboon
Authors: Clough J. F. M. , Kernell D. , Phillips C. G. 
Published: December 2014

1. Peripheral nerves of the baboon's forelimb were stimulated at different sites, and the latencies of antidromic action potentials were measured in intracellular records from forelimb motoneurones.2. The conduction velocity of single motor axons was slower in the brachial plexus than in the nerves of the arm and forearm. This proximal slowing of conduction velocity was more marked for rapidly conducting axons than for the more slowly conducting ones.3. Gross recordings from dorsal and ventral roots showed that the conduction velocity was slower in the brachial plexus than in the arm for fast afferent as well as efferent nerve fibres.4. The proximal slowing of conduction velocity was shown to be due neither to errors of measurement nor to proximo‐distal differences of temperature.
Motor innervation, motor unit organization and afferent innervation of m. extensor digitorum communis of the baboon's forearm
Authors: Eccles Rosamond M. , Phillips C. G. , Chien-Ping Wu 
Published: December 2014

1. One hundred and fifty efferent axons innervating m. extensor digitorum communis (EDC) were isolated in filaments of C7 and C8 ventral roots of baboons. Conduction velocities were measured antidromically by stimulating the muscle nerve and recording from the filaments, and fell into two groups: a fast (49‐84 m/sec) and a slow (22‐41m/sec), presumably fusimotor group. The threshold for these latter axons exceeded the strength needed to elicit the maximal motor twitch.2. Stimulation of ventral root filaments containing slow axons produced no contractile tension in EDC.3. Stimulation of ventral root filaments containing fast‐group axons elicited all‐or‐nothing twitches of motor units of EDC. The twitch tensions of 66·3% of the units were < 2·0 g wt.; only 8·7% were > 5·0 g wt. Tetanus‐twitch ratios were 1·4‐4·7 in a sample of 14 units. Contraction times were between 15 and 35 msec in 97% of the units. There was no correlation between contractile properties and axonal conduction velocity.4. Afferent volleys from the stimulated EDC nerve were recorded from C6 or C7 dorsal roots. The threshold was below the threshold for a just‐detectable motor twitch in ten out of eleven baboons. Conduction velocity of the earliest component of the muscle afferent volley was 67‐83 m/sec.5. The conduction velocities of twenty‐eight spindle afferents, identified by their responses to linear stretches of EDC and by their unloading by maximal twitches, were all < 70 m/sec. Higher dynamic sensitivity tended to be associated with higher conduction velocity.
Interaction between sodium and calcium ions in the process of transmitter release at the neuromuscular junction
Authors: Colomo F. , Rahamimoff R. 
Published: December 2014

1. The interaction between Na and Ca ions on quantal transmitter release at the frog neuromuscular junction has been studied, using intracellular recording and averaging of responses.2. At low calcium concentrations, partial withdrawal of Na ions increases end‐plate potential (e.p.p.) amplitudes and quantal content (m) and decreases the amplitude of the miniature e.p.p.s (m.e.p.p.s). Under these conditions the relation between [Ca] and m is highly non‐linear. When plotted on double logarithmic co‐ordinates withdrawal of [Na] causes a nearly parallel shift of this relation.3. Mutual interaction occurs between Ca, Na and Mg in transmitter release. With a constant low [Ca] in the medium, withdrawal of [Na] produces a smaller increase in m when [Mg] is high, than when [Mg] is low.4. In the presence of normal [Ca] (1·8 m
M), [Na] withdrawal decreases the amplitude of the e.p.p. and produces a small decrease in m.5. The results can be explained by assuming that [Na] reduction has two mutually opposing effects on transmitter release: it makes more sites available for the action of Ca, and it lowers the amplitude of the action potential in the nerve terminals. The former effect dominates at low, the latter at high, calcium concentrations.
Changes in plasma glucose, lactate and free fatty acids in lambs during summit metabolism and treatment with catecholamines
Authors: Alexander G. , Mills S. C. , Scott T. W. 
Published: December 2014

1. Exposure to cold increased the plasma levels of glucose and lactate in young lambs (< 1‐63 days old). Free fatty acid concentrations also increased, the increase being much greater in lambs older than 20 days.2. Intravenous infusions of adrenaline and noradrenaline into lambs under a neutral thermal environment caused large increases in plasma glucose, lactate and free fatty acids.3. Adrenaline and noradrenaline infusions increased the concentration of palmitic, stearic and oleic acids in the plasma of young lambs.4. Treatment of lambs in summit metabolism with either α‐ or β‐adrenergic blocking agents (phentolamine or propranolol, respectively) caused the plasma levels of free fatty acids to fall. Phentolamine hydrochloride decreased the concentration of plasma glucose, but did not change the lactate level. In contrast, propranolol decreased the concentration of both of these metabolites in a significant proportion of the experiments.5. Induction of muscular paralysis by suxamethonium chloride, in lambs exposed to cold, resulted in a rise in plasma free fatty acids, and a fall in glucose and lactate levels.6. These observations suggest that the circulating level of plasma metabolites in young lambs is not the limiting factor in the metabolic response to cold exposure.
Interdependence of albumin and sodium transport in the foetal and new‐born pig intestine
Authors: Brown Pat , Smith M. W. , Witty R. 
Published: December 2014

1. Everted sacs of new‐born pig intestines incubated in bicarbonate saline at 37° C, transferred bovine plasma albumin across the mucosa into fluid bathing the serosa, the amount transferred increasing as the concentration of albumin in the mucosal fluid was raised from 0·5 to 16 g/100 ml.2. The rate of albumin transfer across the foetal pig intestine showed an apparent maximum, about 400 μg/g intestine/hr, 2 weeks before birth. The transfer at birth, about 200 μg/g intestine/hr, fell sharply during the next 2 days but later returned to that previously found at birth.3. When sacs were prepared from the intestines of 1 to 7‐day‐old pigs part of the recovered albumin was degraded. No digestion was found when the intestines of new‐born or foetal pigs were used.4. The transfer of water and sodium, but not glucose, measured across the foetal and new‐born pig intestine, was consistently higher when albumin was present in the mucosal fluid: the transmural potential difference was lowered by the presence of albumin. These differences disappeared during the first 2 days of life.5. Both the total and ouabain‐sensitive adenosine triphosphatase (ATPase) activities of the pig intestinal epithelium fell within 24 hr of birth. There was some increase in total ATPase activity in older pigs but the ouabain‐sensitive activity remained low.6. The relation between albumin and sodium transport, seen at a time when albumin is not being metabolized, suggests that the transfers are closely coupled. The movement of sodium into a mucosal cell down its own concentration gradient may provide energy for the translocation of albumin.