bluuebunny/crossref_metadata_2025_split huggingface dataset:
Summit metabolism and cardiovascular function in young lambs during hyperoxia and hypoxia
Authors: Alexander G. , Williams D. 
Published: December 2014

1. Exposure of lambs at sea level to air containing more than 33% oxygen resulted in a small increase in summit metabolism (maximum oxygen consumption on severe cold exposure) in some lambs, and in an improvement in the ability to maintain summit metabolism in others; there was a concomitant improvement in the maintenance of cardiac output, but no change in the degree of right to left shunting.2. Hypoxia (12–13% oxygen in inspired air) reduced summit metabolism of new‐born lambs by 25%; but there was no effect in lambs 6–11 days old. Hypoxia neither reduced cardiac output, nor affected the degree of right to left shunting.3. The results suggest that in very young lambs there is some limitation of summit metabolism imposed by the supply of either oxygen or substrate to thermogenic tissues.
The production of adenosine triphosphate in perfused giant axons of Loligo
Authors: Martin K. , Shaw T. I. 
Published: December 2014

1. The light production by squid giant axons perfused with solutions containing extract of firefly tails has been studied to give information about the production of ATP in such axons.2. An initial flash occurs when the perfusion fluid first enters the fibre. There is a secondary production of light, noticeable when the perfusion is halted, providing glutamate or aspartate are present in the perfusion medium.3. There is no secondary light production if glutamate is replaced by sulphate, succinate or α‐ketoglutarate in the perfusion fluid.4. Ouabain has no effect whereas cyanide and oligomycin both block the secondary light production, the latter irreversibly.5. When the sodium outside the fibre is replaced by lithium or choline the secondary light production is often reduced and occasionally abolished.6. A raised internal sodium does not enhance secondary light production.7. The secondary light production is dependent upon the concentration of AMP in the perfusion solution.8. Fresh axoplasm generates a powerful light on immersion in perfusion fluid whereas dialysed axoplasm, even in the presence of added glutamate, generates no light whatever.9. The evidence, on balance, suggests that, under the conditions of the experiments described, there is no detectable reversal of active transport in perfused nerve fibres but that there is an enzyme system, probably membrane bound, capable of generating ATP from glutamate or aspartate and AMP by oxidative phosphorylation. The enzyme system can be inhibited by the replacement of external sodium.
Responses of unshorn and shorn sheep to thermal stress
Authors: Phillips G. D. , Raghavan G. V. 
Published: December 2014

1. The effect of close shearing upon the respiratory frequency of ewes at ambient temperature of 20° C and 55% relative humidity has been described.2. Removal of an adequate area of fleece (3000 cm2 or more) on the thoraco‐lumbar region resulted in a depression of respiratory responses and this was attributed to the exposure of cold receptors located beneath the fleece.3. The continued depression of respiratory frequency of partially shorn sheep (3000 cm2) during rising ambient temperature appears to be due to persistence of cold receptor drive originating from the shorn area.4. The absence of any rise in carotid blood temperature before the onset of polypnoea in unshorn sheep, during rising ambient temperature, suggests that the onset of panting in sheep can occur almost immediately upon a rise in ambient temperature even in the absence of any rise in the temperature of the blood supplying the brain.
Efflux mechanism contributing to the stability of the potassium concentration in cerebrospinal fluid
Authors: Bradbury M. W. B. , Štulcová Barbora 
Published: December 2014

1. The clearance of 42K from c.s.f. has been separated into two components by means of ventriculo‐cisternal perfusion in the rabbit. At 2 hr the largest fraction of radioactivity is recoverable from brain. A smaller fraction passes into the bloodstream and this loss can be expressed as a barrier clearance.2. The clearance into brain was largely independent of potassium concentrations in the perfusion fluid of 15 m‐equiv/l. and below. It was depressed by ouabain, 10−2 m
M.3. The barrier clearance was small, about 9% of the total, when the perfusion fluid contained potassium (1·5 m‐equiv/l. or below). Above this concentration it increased steeply reaching 32 μl./min or 37% of the total at 10 m‐equiv/l. A similar high barrier clearance was caused by replacing 84% of the sodium in the perfusion fluid with choline. Ouabain, 10−2 m
M, abolished the increased barrier clearance due to potassium (10 m‐equiv/l.).4. The clearance of [14C]urea into both brain and blood was unaffected by the potassium concentration in c.s.f. The barrier clearance of [14C]urea was, if anything, increased by 10−2 m
M ouabain.5. Perfusion of the low sodium fluid caused a net loss of potassium from c.s.f.6. The influx of 42K into c.s.f. from blood was the same, when the perfusion fluid contained potassium (2·9 or 10 m‐equiv/l.).7. The potential between c.s.f. and blood of about 4 mV (c.s.f. positive) was little affected by the potassium or sodium concentration in the perfusion fluid.8. These observations indicate that the net flux of potassium ions from c.s.f. to blood begins to increase very steeply with the potassium concentration in c.s.f., when the latter is between 2 and 3 m‐equiv/l. This relation, taken together with the variation of influx with the potassium concentration in blood plasma, can largely explain the known stability of the potassium concentration in the c.s.f. of the rabbit at 2·8–2·9 m‐equiv/l.9. The increased flux of potassium from c.s.f. at raised concentrations of potassium in this fluid appears to depend on a sodium—potassium pump inhibitable by ouabain.
The effect of temperature on the resting tension of frog's muscle in hypertonic solutions
Authors: Hill D. K. 
Published: December 2014

1. It has long been known that the tension of a resting muscle rises when it is warmed and falls on cooling. It is shown here that treatment with hypertonic solution causes an alteration in this effect; the usual rise or fall of tension with warming or cooling is then preceded by a transient change in the opposite direction.2. The magnitude of the abnormal reversed phase does not depend in a simple, linear, manner on the temperature change. For instance, the effect for cooling from 20 to 0° C is much greater than twice that for 10 to 0° C.3. The results lead to the suggestion that the tension, in both normal and hypertonic muscle, comes from an active process. It is proposed that a temperature change operates by altering the concentration of an ‘activating substance’, and that the change of concentration becomes delayed by hypertonicity.
Further purification of a polypeptide demonstrating enterogastrone activity
Authors: Brown J. C. , Mutt V. , Pederson R. A. 
Published: December 2014

1. The further purification of a polypeptide having potent enterogastrone activity, without CCK—PZ effects, is described.2. The material was inhibitory when doses of 1·0 μg/kg.hr were administered intravenously. Amino acid analyses demonstrated the absence of proline, a high content of glutamine and a preponderance of lysine over arginine. Tryptic degradation destroys the inhibitory effect of the polypeptide. Further studies must be performed before the physiological status of the polypeptide can be ascertained.
The representation of three‐dimensional visual space in the cat's striate cortex
Authors: Blakemore Colin 
Published: December 2014

1. Binocularly driven single units were recorded in the cat's striate cortex. For each neurone the two monocular receptive fields were stimulated simultaneously in order to assess the optimal positioning of the image in both eyes to give the best binocular response.2. The electrode was driven perpendicular to the surface of the brain to explore cortical columns, all the cells of which are known to have the same preferred target orientation.3. All orientation columns were found to fit into one of two classes according to their binocular organization.4. In a constant depth column the receptive fields of binocular neurones cover a small retinal area and they are laid out in almost identical arrays in the two eyes. Consequently, the horizontal disparity is practically the same for all the units. The depth column as a whole is viewing a thin sheet of visual space, a few degrees wide, floating at some distance from the cat. There may be about 0·6° disparity difference between neighbouring depth columns.5. In a constant direction column the binocular units' fields are all super‐imposed on the retina contralateral to the hemisphere containing the column. In the ipsilateral eye they are more scattered horizontally. Therefore the horizontal disparity varies enormously from cell to cell and the column as a whole is viewing a cylinder of visual space directed towards the contralateral eye. Neighbouring direction columns may vary by about 4° in their oculocentric visual direction.6. This columnar arrangement is probably important for space perception in the cat. Activity in only one depth and one direction column would specify the orientation and the three‐dimensional locus of an object in space.7. The two types of column may be involved in the control of disjunctive and conjugate eye movements.
Daily changes in foetal and maternal blood of conscious pregnant ewes, with catheters in umbilical and uterine vessels
Authors: Comline R. S. , Silver Marian 
Published: December 2014

1. Blood gas tensions, pH, packed cell volume (PCV) and the levels of glucose, fructose and lactic acid have been followed in foetal and maternal blood for periods of 3‐30 days in conscious ewes between 80 days gestation and term (∼ 147 days).2. Blood samples were withdrawn through indwelling catheters placed in one or both umbilical vessels, a uterine vein and a maternal artery.3. The success of the operation appeared to depend on the maintenance of maternal blood gas and pH levels within normal limits as well as on the final position of the tip of the catheter. The difficulties and limitations of the technique are discussed.4. Foetal blood gas tensions, pH, PCV, lactic acid and glucose levels did not change markedly during the last 50–60 days of gestation. The fructose concentration fell during this period, the greatest change was between 100 and 120 days gestation.5. Small fluctuations in PO2, PCO2 and pH in umbilical venous blood were associated with similar changes in the uterine vein, so that the gradients across the placenta appeared to remain constant.6. Daily changes in maternal plasma glucose levels were reflected in similar changes in foetal plasma fructose and by much smaller alterations in the foetal glucose levels. The glucose concentration in the foetal plasma was less than 25% of that in maternal plasma.7. The existence of a general relationship between maternal plasma glucose and foetal plasma fructose was masked by the independent fall in fructose levels with age. However, at any given stage of gestation, there was a significant correlation between foetal fructose and maternal glucose.8. Few changes in the umbilical blood were associated with impending abortion or birth. Blood gas tensions remained constant, but a sharp fall in fructose levels often occurred 48 hr before any changes in pH, PCV and lactate concentration.9. Present and other findings on conscious animals are compared with previous observations on acute, anaesthetized preparations.
Medullary activation of intercostal fusimotor and alpha motoneurones
Authors: Andersen P. , Sears T. A. 
Published: December 2014

1. Studies have been made of the anatomical localization in the brain stem of the sites at which tetanic stimulation evoke inspiratory and expiratory apneusis.2. The inspiratory responses arise from a relatively circumscribed region within the medulla corresponding to the nucleus reticularis giganto‐cellularis and ventralis which give rise to the medullary contingent of the long reticulo‐spinal tracts. Expiratory responses were obtained dorsal and lateral to this area, but not localized to any cyto‐architectonically distinct region of the reticular formation.3. During the apneustic responses there was co‐activation of the intercostal alpha and fusimotor neurones with reciprocal inhibition of the antagonistic motoneurones. The threshold for activation of the fusimotor neurones was usually lower than for the alpha motoneurones.4. Results with brief tetanic stimulation suggest that the long reticulospinal tracts are responsible for the apneustic responses and that the effects are mediated at segmental level over an interneuronal pathway.5. The response of the intercostal motoneurones during the apneustic responses is shown to be dependent on the integrity of the dorsal spinal roots.
The origin and secretion of pancreatic juice bicarbonate
Authors: Case R. M. , Scratcherd T. , Wynne R. D'A. 
Published: December 2014

1. The rate of secretion from a saline‐perfused preparation of the cat's pancreas is directly proportional to the perfusate bicarbonate concentration. When all bicarbonate is omitted, secretion completely or almost completely ceases.2. Incorporation of [14C]bicarbonate into the perfusion fluid results in its prompt appearance in the juice. The radioactive label is concentrated four to five times in the juice just as the total juice bicarbonate is four to five times greater than perfusate bicarbonate.3. These two observations suggest that about 95% of pancreatic juice bicarbonate is derived from perfusate (plasma) bicarbonate.4. The inhibition of pancreatic secretion from the perfused gland by acetazolamide is similar to that observed in the intact animal.5. There is a fall in pH and rise in PCO2 in the perfusion fluid leaving the gland which is greater during secretion than at rest.6. It is therefore suggested that during secretion, hydrogen ions pass from the gland into the perfusate (plasma), thus increasing the production of carbon dioxide from circulating bicarbonate. This carbon dioxide diffuses into the cell, is rehydrated (partly under the influence of carbonic anhydrase) and finally is secreted, thus establishing the necessary gradient for the continued diffusion of carbon dioxide into the cell.
Presynaptic and post‐synaptic inhibition elicited in the cat's dorsal column nuclei by mechanical stimulation of skin
Authors: Andersen P. , Etholm B. , Gordon G. 
Published: December 2014

1. Primary afferent depolarization (PAD), with a time course comparable with that of the PAD following limb nerve stimulation, was produced in the cuneate nucleus by mechanical stimulation of the skin of the ipsilateral forepaw. Brushing or blowing on hairs was as effective as any other form of stimulation and there was a rapid adaptation to a sustained stimulus. Up to 55% increase in excitability was produced by blowing on hairs.2. The P‐wave and the PAD produced by mechanical stimulation were at a minimum in the rostral part of the cuneate nucleus and at a maximum 2‐6 mm caudal to the obex.3. The distribution of the PAD produced in the gracile nucleus by blowing on the skin of the hind foot was studied by a technique allowing measurement of excitability changes near the terminals of single fibres. Minimal values were obtained rostral to the obex and maximal values 1‐4 mm caudal to the obex, a distribution matching that previously determined for single cells subject to surround inhibition.4. Post‐synaptic inhibition was produced in the cuneate nucleus by gentle blowing on the ipsilateral forepaw. Up to 20% fall in excitability occurred in populations of cells tested by direct electrical stimulation. IPSPs lasting up to 160 msec were observed in single cells following light mechanical stimulation in the immediate neighbourhood of these cells' receptive fields. Blocking of antidromic invasion of single cells was occasionally produced by mechanical skin stimulation.5. It is concluded that both pre‐ and post‐synaptic inhibition must be concerned in the phenomenon of afferent surround inhibition, though there was no evidence to indicate their relative roles, qualitatively or quantitatively.6. It is shown that up to 20% reduction in transmission through the gracile or cuneate nucleus could be produced by blowing on the ipsilateral hind paw or forepaw respectively, measured as reduction in the area of the monophasically recorded lemniscal response. A single electrical stimulus to the skin of the contralateral forepaw reduced transmission through the cuneate nucleus by less than 5%.
The characteristics of the cochlear after‐potential studied in the guinea‐pig by perfusion and stimulation
Authors: Panayiotopoulos C. P. , Stopp Phyllis E. 
Published: December 2014

1. An after‐potential which comprises three components can be recorded from scala tympani or scala vestibuli following the termination of a tone burst of more than 20–30 msec duration. The major component is of opposite polarity to the negative summating potential (SP) when recorded from scala tympani (ST) and of the same polarity as the SP when recorded from scala vestibuli.2. The size of this after‐potential is dependent on the duration and strength of the tonal stimulus but not on the stimulus frequency or its rate of turn‐off.3. A single short tone‐pip (10 msec) produces no visible after‐potential, but an after‐potential is seen following the end of a train of such pips separated by intervals of similar duration.4. Replacement of the perilymph in ST by Ringer solution has a negligible effect on the cochlear responses. However, replacing the sodium ion in Ringer solution by lithium or adding DNP to the perfusate abolishes the after‐potential just as in the case of a neuronal after‐potential. The latter manoeuvre affects also the N1, CM and SP, while the former does not.5. It is suggested that there exists an active membrane mechanism at the hair cell/nerve junction, which is responsible for the after‐potential and which can be influenced by perfusion of ST. It is further suggested that this neural mechanism makes a contribution to the recorded SP over and above the SP component due to non‐linear factors.
Development of the differential response to succinylcholine in the fast and slow‐twitch skeletal muscle of the kitten
Authors: Mann William S. , Salafsky B. 
Published: December 2014

1. The response to SCh has been studied in anterior tibialis and soleus muscles of new‐born and neonate cat while, in a separate group of animals of similar ages, the end‐plate development in these muscles has been examined.2. At birth, when the contraction times of the anterior tibialis and soleus are not statistically different, the anterior tibialis is 1·4 times more sensitive to SCh blocking action than the soleus, but both muscles were 20–40 times less sensitive than their adult counterparts.3. With maturation, the ratio of the soleus/anterior tibialis contraction time increased to 2·7 while the ratio of the 50% blocking dose of SCh in the soleus/anterior tibialis increased to 2·8, the increases being parallel. The time to 50% recovery at 50% blocking doses of SCh was similar for both muscles at all ages although it was 3 times longer in new‐born and 1‐week‐old animals than in animals 3 weeks of age and older.4. The areas of individual end‐plates from these muscles were very similar at birth but by three weeks of age the areas of end‐plates from the anterior tibialis were substantially greater than those obtained from soleus.5. We have speculated that the relationship between SCh sensitivity and end‐plate area in fast and slow muscle may find its origins in the frequency of the MEPP.
Autonomic effector responses to stimulation of nucleus fastigius
Authors: Achari N. K. , Downman C. B. B. 
Published: December 2014

1. In anaesthetized cats electrical stimulation of the nucleus fastigius caused cardiovascular responses, electrodermal responses of the paws and pupil dilation with retraction of the nictitating membranes.2. The cardiovascular responses included rise of arterial pressure and peripheral vasoconstriction. Increase of pulse pressure and tachycardia also occurred.3. The effects of sympathetic blocking drugs indicate that fastigial stimulation causes sympathetic discharge to the heart and to the peripheral vessels. There was no evidence of alteration of vagal activity.4. Fastigial stimulation inhibited reflex bradycardia due to carotid sinus distension, vagal afferent stimulation or phenyl diguanide.5. Fastigial and hypothalamic influences on cardiovascular responses could be evoked after severing the nervous pathways connecting the two.6. The pressor response to fastigial stimulation was still present after bilateral division of the carotid sinus and vagus nerves.
Direct and indirect activation of the hippocampus by tubocurarine
Authors: Feldberg W. , Lotti V. J. 
Published: December 2014

1. In cats anaesthetized with intravenous chloralose, tubocurarine was either perfused through the inferior horn of a lateral ventricle or applied by micro‐injection into the hippocampus, and the electrical activity was recorded from the surfaces of the occipital cortices and from the cannulae used for the perfusion or injection which, insulated except at their tips, served as recording electrodes as well.2. With both methods, the hippocampus became activated by tubocurarine acting directly on the hippocampus. The activation resulted in an abnormal spike discharge interrupted from time to time by short bursts of fast activity, termed episodes, followed by periods of electrical silence during which no abnormal activity was recorded. This abnormal discharge was recorded in all leads. The spikes were negative when recorded from the surface of the hippocampus, but changed polarity when the electrode was lowered and penetrated the pyramidal cell layer, and on further lowering the electrode the positive spikes increased in voltage up to 15 mV and then decreased.3. With both methods, signs of indirect activation of the hippocampus were observed when the tubocurarine set up foci of excitation in one of the following three areas of cerebral cortex which lie ventral to the hippocampus, the Area entorhinica, the Area perirhinica and the Area post‐splenialis. The foci of excitation resulted in a continuous discharge of negative spikes which were recorded in the leads from these areas only. A characteristic feature of the indirect hippocampal activation arising from the continuous discharge set up in the Area post‐splenialis was the periodicity. Activation lasting 20–60 sec occurred every few minutes or at shorter intervals, often leading to an episode.