bluuebunny/crossref_metadata_2025_split huggingface dataset:
The secretion of pancreatic juice in response to stimulation of the vagus nerves in the pig
Authors: Hickson J. C. D. 
Published: December 2014

1. The secretory response to stimulation of the vagus nerves has been examined in the pig and compared with that in the dog under similar experimental conditions.2. In the pig, stimulation of the vagus nerves caused a profuse flow of pancreatic juice with a high content of bicarbonate, in addition to a secretion of digestive enzymes; atropine suppressed the secretion of enzymes but failed to diminish the flow of bicarbonate‐rich juice.3. Intra‐arterial injections of acetylcholine closely imitated the effects of stimulation of the nerves, with the difference that both the flow of juice and the secretion of enzymes were abolished together by atropine.4. Stimulation of the nerves and injections of acetylcholine were effective after resection of the stomach and intestine: these stimuli can therefore act directly on the pancreas, independently of the release of gastro‐intestinal hormones.5. In the dog, the pancreas differed from that of the pig in that stimulation of the vagus nerves and injections of acetylcholine acted predominantly on the secretion of enzymes and caused only a sparse flow of juice. Atropine annulled all these effects together.6. The results show that the vagus nerves can exert a much wider control of the secretion of pancreatic juice in the pig than in the dog. Possible mechanisms for this action are discussed.
Studies on the excretion of [14C]histamine and its metabolites by the rabbit kidney
Authors: Lippert T. H. , Quasthoff Ursula 
Published: December 2014

1. After intravenous administration of [14C]histamine in rabbits, the urinary excretion of [14C]histamine and [14C]histamine metabolites was examined over a period of 4 hr.2. It was found that [14C]histamine was excreted in the unchanged form only in small amounts (6–7%), while 54–71% was eliminated in the form of its metabolites.3. Under normal conditions, the percentage excretion of metabolites, but not of histamine, showed a dose dependence. With the higher [14C]histamine dose, a significantly smaller proportion of the dose given was excreted as metabolites than with the lower dose. The proportion of unchanged [14C]histamine excreted remained constant.4. Pre‐treatment with histamine infusions, or with mepyramine maleate, caused an increase in the excretion of [14C]histamine metabolites while the excretion of [14C]histamine remained unchanged.5. Pre‐treatment with a diuretic, a combination of mersalyl and theophylline, did not influence the excretion of [14C]histamine nor of its metabolites.
Consequences of monocular deprivation on visual behaviour in kittens
Authors: Dews P. B. , Wiesel T. N. 
Published: December 2014

1. Kittens were raised for a period with one of their eyes closed by suture of the lids. The age at suture and the duration of deprivation were varied systematically. When the cat was a year or more old, the normal and deprived eyes were compared using behavioural procedures which made graded demands on visual function.2. In kittens deprived from birth, the duration of eye closure determined the severity of the defect in vision with the deprived eye. A cat with an eye closed for the first 4‐6 weeks showed as a permanent effect only a lowering of the visual acuity. When closure was extended through the first 7 weeks the visual acuity was further lowered but the animal still showed good visual guidance of paw placement. Further extension of deprivation through the first 16 weeks led to a still more severe defect; such animals showed no indication of visual guidance of paw placement or of pattern discrimination. They were influenced visually by stimuli that differed in luminosity.3. The upper age limit of the susceptibility to deprivation was determined by varying the age at eye closure. Waiting until 1 month of age before closing the eye conferred no appreciable protection. Waiting until 2 months of age, however, reduced the damage. Deprivation starting at 4 months of age or later produced no effect we could detect. Thus, susceptibility is greatest during the second month after birth and then falls until by 4 months of age the kitten, like the adult cat, suffers no permanent consequences of monocular light and form deprivation.4. After exclusive use of the deprived eye for a period, brought about by closure of the normal eye, visual control with the deprived eye was better than in similarly deprived cats whose normal eye was never closed. Improvement in the deprived eye was also seen in an animal whose normal eye was closed after both eyes had been open for more than one year.5. Relating the behavioural results to the neurophysiological findings in the visual cortex in the same or similarly deprived cats shows that the grading of visual defects with age and length of deprivation was generally paralleled by a change in proportion of cortical cells driven by stimulation of the deprived eye. The effect of reversal of eye closure in improving behavioural control was not, however, accompanied by an increase in the ability of the deprived eye to drive cortical cells.
Abomasal secretory responses to teasing with food and feeding in the sheep
Authors: McLeay L. M. , Titchen D. A. 
Published: December 2014

1. Secretion of acid and pepsin from abomasal pouches and contractions of the reticulum and rumen were studied in sheep. Observations were made in sheep after being fasted and when they had food available ad libitum.2. The abomasal pouches were of fundic regions alone and also of the fundic region with a rim of antral mucosa.3. The secretion from both types of pouch was continuous, was increased by feeding and decreased by fasting.4. The volume, pepsin concentration and acid concentration of the secretion from fundic pouches increased within 15–30 min of the sheep being teased with food or fed. These responses were observed in sheep which had food available ad libitum or had been fasted.5. Reticulum contractions and the rumen contractions associated with them (A sequences) increased in frequency when sheep with either type of pouch were teased with food or when they ate.6. Consistent associations between rumination and abomasal secretory activity were not established.7. Mixed fundic‐antral pouches did not characteristically show responses to teasing with food and sustained secretory responses were delayed by up to 90 min after feeding commenced.8. It is suggested that a cephalic phase of gastric (abomasal) secretion was revealed in the studies on fundic pouches of the abomasum.
Blood levels of oxytocin and vasopressin during suckling in the rabbit and the problem of their independent release
Authors: Bisset G. W. , Clark Barbara J. , Haldar Jaya 
Published: December 2014

1. Oxytocin and vasopressin were assayed in samples of blood collected from conscious rabbits during suckling. The milk yields were determined from the weight gain of the litters.2. With normal milk yields (35–155 g), relatively high concentrations (31–375 μu./ml.) of oxytocin were present in the blood but vasopressin was detected in only one out of eight samples. It is concluded that the release of oxytocin by the milk‐ejection reflex is essential for normal milk removal in the rabbit and that this hormone is released independently of vasopressin.3. When the milk yield did not exceed 15 g, an amount which could be removed by passive withdrawal from the mammary gland, vasopressin was detected in four out of five blood samples but none contained a detectable concentration of oxytocin. This result can be explained by the intervention of emotional stress which is known to block the milk‐ejection reflex but which acts as a stimulus for the release of vasopressin.4. Emotional stress could inhibit the milk‐ejection reflex either centrally by blocking the release of oxytocin, or peripherally by blocking the response of the mammary gland to circulating oxytocin. The absence of the hormone in blood during ineffectual suckling suggests that the block is central.
The mechanism of functional vasodilatation in rabbit epigastric adipose tissue
Authors: Lewis G. P. , Matthews J. 
Published: December 2014

1. The effect of close‐arterial infusions of fat‐mobilizing substances has been examined on the release of free fatty acids and blood flow in the epigastric adipose tissue of rabbits.2. All the fat mobilizers in addition to causing the release of free fatty acids also caused an increased blood flow in the fat tissue.3. Both the fat mobilization and the vasodilatation continued for an hour or so after the end of infusion.4. Although no vasodilator substance could be detected in the venous effluent from the activated adipose tissue, a vasodilator could be detected in acid—ether extracts of adipose tissue excised during a period of fat mobilization.5. It is suggested that a vasodilator substance is released or formed in adipose tissue during fat mobilization and that this substance accounts for the vasodilatation accompanying activity in the tissue.
Electrical responses of single cones in the retina of the turtle
Authors: Baylor D. A. , Fuortes M. G. F. 
Published: December 2014

1. Intracellular recordings have been made from single photoreceptors in the retina of the turtle. Histological sections of the retina made after injection of dye through the recording electrode reveal dye in the inner segments of single cones.2. Following a brief flash of light the cone undergoes a hyperpolarization which is graded with the intensity of the flash.3. The excitatory receptive field of a receptor is probably as small as the cross‐section of a single cone, but accurate measurements are rendered difficult by scattering of light within the retina.4. The voltage drop produced by a current injected into the cell is increased during the response to light. Steady hyperpolarizing currents increase the size of the response to light; depolarizing currents of increasing strength reduce and then reverse the response.5. The results are consistent with the hypothesis that light activates the visual cell by decreasing the permeability of membrane channels which in darkness act as a shunt of the membrane.
Direct measurements of membrane unstirred layers
Authors: Green K. , Otori T. 
Published: December 2014

1. The unstirred layer of fluid bounding the posterior surface of the rabbit cornea and contact lens has been directly measured using an optical apparatus.2. Small polystyrene latex spheres (< 0·25 μ diameter) were used as an indicator because of the excellent light‐reflective properties; other indicators were used (e.g. carmine particles) and had a similar behaviour.3. With the bulk solution unstirred the layer was 350 μ thick on the cornea and 150 μ thick on the contact lens. Following vigorous stirring the layer was reduced to 65 μ on the cornea and < 20 μ on the contact lens.4. The present direct measurements of the unstirred layers thickness confirm previous indirect measurements.
Water uptake by the crab‐eating frog Rana cancrivora, as affected by osmotic gradients and by neurohypophysial hormones
Authors: Dicker S. E. , Elliott Annie B. 
Published: December 2014

1. The rate of water uptake across the skin was investigated in live Rana cancrivora, an euryhaline frog which has been reported to tolerate sea water. When they were exposed to distilled water at 29° C, the rate of water uptake was 8·4 ± 0·4 μl./cm2.hr; when bathed in solutions ranging from 30 to 570 m‐osmole/l., irrespective of whether the solute was sucrose, urea or NaCl, the rate of fluid uptake during the first day was inversely related to the osmolarity of the solution. No appreciable fluid movement was observed when the bathing solution had an osmolar concentration of 270 m‐osmole/l.2. The rate of fluid uptake was not affected by injections of vasopressin, oxytocin or of extracts of amphibian or rat pituitary glands, irrespective of whether R. cancrivora were bathed in distilled water or in solutions of NaCl or sucrose.3. In Bufo melanostictus, in contrast with R. cancrivora, injections of neurohypophysial extracts produced a marked increase of the rate of fluid uptake.4. In the laboratory, R. cancrivora could be acclimatized stepwise to tolerate NaCl solutions up to 700 m‐osmole/l. for 7 days.5. After 24 hr exposure either to distilled water or to NaCl solutions from 100 to 670 m‐osmole/l., the osmolar concentration of the plasma of R. cancrivora was always higher than that of the bathing fluid. In R. pipiens or R. temporaria plasma osmolar concentration was higher than that of the bathing fluid only when the latter did not exceed 300 m‐osmole/l.6. Under all conditions investigated, the osmolar concentration of the urine of R. cancrivora was always lower than that of the plasma.7. The amounts of pressor and oxytocic activities of pituitary glands of R. cancrivora kept in distilled water or in NaCl solutions up to 300 m‐osmole/l. were 8·9 ± 0·8 and 1·8 ± 0·3 m‐u./gland, irrespective of sex or body weight within the range 30–50 g. After 3 days exposure to hypertonic NaCl solutions, the amounts of pressor and oxytocic activities were 14·7 ± 1·2 and 3·1 ± 0·3 m‐u./gland. In both instances the pressor/oxytocic ratio was 4·9. Pituitary glands of R. temporaria similarly showed increased pressor and oxytocic activities after exposure to NaCl solutions of 300–360 m‐osmole/l.
Perfusion from cerebral ventricle to cisterna magna in the unanaesthetized cat. Effect of calcium on body temperature
Authors: Feldberg W. , Myers R. D. , Veale W. L. 
Published: December 2014

1. A method is described for the perfusion of the liquor space from a lateral cerebral ventricle to the cisterna magna in the unanaesthetized cat. Perfusions were carried out for 30–40 min using various physiological salt solutions whilst rectal temperature was recorded.2. When the salt solution used contained calcium in the physiological concentration, rectal temperature remained unchanged, but when it contained no calcium an intense hyperthermia developed during the perfusion. The finding that calcium must be present in the perfusion fluid for preventing temperature from rising may lead to a new understanding of the working of the ‘set‐point’ in the control of body temperature and of the mechanism of action of pyrogens.3. Independent of the nature of the perfusion fluid a long‐lasting late rise in temperature developed after a perfusion. This happened regularly when the infusion needle was inserted only into the hub of the ventricular cannula, but rarely when the needle was extended beyond the tip of the cannula shaft and the cannula had been flushed out during the preceding days. It is therefore thought that an unknown pyrogenic factor present in the lumen of the cannula and washed into the ventricle with the perfusion fluid is responsible for this effect.4. The effluent collected from the cisterna contracted the fundus strip of the rat stomach. As the contractions were little affected by BOL, they are attributed mainly to an action of prostaglandin E1 and not to an action of 5‐HT. There was no difference in the biological activity of the effluent whether the perfusion fluid contained calcium or not.
An electrophysiological investigation of the slow fibre system in the frog rectus abdominis muscle
Authors: Forrester T. , Schmidt H. 
Published: December 2014

1. Junctional potentials were recorded with a micro‐electrode inserted into muscle fibres of the rectus abdominis muscle of the frog. Large and small nerve fibres were stimulated separately, using a selective stimulation technique. In a few muscle fibres rectangular current pulses were applied through a second micro‐electrode to examine current—voltage relations.2. Two groups of muscle fibres could be distinguished: (a) Muscle fibres with resting potentials less negative than −75 mV, being localized at the ventral surface only and representing about 9% of the superficial fibres. These fibres were found to be innervated by small (high‐threshold) nerve fibres and responded to single indirect stimuli with a typical s.j.p. (long latency, multiple components, after‐hyperpolarization); upon repetitive stimulation summation of s.j.p.s and a slowly increasing tension could be recorded. The fibres showed a slow time course of electrotonic potentials, relatively high membrane resistance and ‘delayed rectification’. (b) Muscle fibres with generally much higher resting potentials, being innervated by large (low‐threshold) nerve fibres only. Upon indirect stimulation a short‐latency end‐plate or action potential (followed by a twitch) was recorded. The membrane time constant and input resistance of these fibres were similar to those of twitch fibres in other frog muscles.3. No evidence was found in the present work for the existence of an intermediate type of muscle fibre.4. It is concluded that the rectus muscle, similar to other frog muscles, contains two distinct types of muscle fibres, twitch and slow.
The binding of tritiated ouabain to mammalian non‐myelinated nerve fibres
Authors: Landowne D. , Ritchie J. M. 
Published: December 2014

1. A study has been made of the binding of radioactively labelled ouabain by desheathed rabbit vagus nerves, which consist mainly of non‐myelinated fibres. The corresponding inhibition of the electrogenic sodium pump was also measured.2. By varying the ouabain concentration and the external potassium concentration two kinds of binding sites could be distinguished: a first site specifically associated with pumping and whose ability to bind ouabain is dependent on the external presence of potassium; and a second site not associated with pumping and unaffected by external potassium.3. Just complete inhibition of the sodium pumping mechanism is associated with a specific binding of ouabain of about 4·3 p‐mole/mg dry nerve.4. This gives an upper limit for the density of sodium pumping sites of about 750 per square micron.5. The turnover rate (i.e. (cation pumped)/(number of sites)) at 20° C is about 22 sec−1.
Electrophysiological evidence for the existence of orientation and size detectors in the human visual system
Authors: Campbell F. W. , Maffei L. 
Published: December 2014

1. The evoked potential in response to a grating alternating in phase at 8 c/s was recorded as a function of contrast from the occiput of man.2. It was found that a linear relation exists between the log. of contrast and the amplitude of the evoked potential.3. Extrapolation to zero amplitude voltage of the regression line between the amplitude of the evoked potential and log. contrast predicts the psychophysical threshold. This law was found to hold over the wide range of spatial frequencies tested.4. Below 3 c/deg the results are best fitted with two regression lines; one of these is generated from the foveal and the other from the parafoveal representation in the cortex.5. The slope of the regression lines was found to be almost independent of either the spatial frequency or the area of the stimulus grating.6. The slope of the regression lines could be markedly increased by using as a stimulus either two different spatial frequencies, or two different orientations, presented simultaneously.7. Using the evoked potential the selectivity to orientation was found to be so high that a channel was not influenced by another orientation 15° away.8. The channels selectively sensitive to spatial frequency were highly selective and were not influenced by another spatial frequency one octave removed in spatial frequency.9. It is concluded that in man there exist neurones highly selective to both orientation and spatial frequency.
The diuretic actions of prostaglandin E1 and of noradrenaline and the occurrence of a prostaglandin E1‐like substance in the renal lymph of cats
Authors: Fujimoto S. , Lockett Mary F. 
Published: December 2014

1. The actions of noradrenaline, prostaglandin E1 and angiotensin II‐amide on various parameters of renal function and on the flow of renal lymph and its equivalent content of prostaglandin E1‐like activity have been compared in cats under chloralose anaesthesia.2. All three compounds produced diuresis and natriuresis. Noradrenaline (0·1–0·3 μg/kg.min) and angiotensin II (0·1–0·2 μg/kg.min) with rise of the filtration fraction (FF) and GFR; prostaglandin E1 (0·13–0·19μg kg.min) with increase in GFR but without change in FF. Noradrenaline and angiotensin markedly raised renal perfusion pressure, prostaglandin E1 lowered it by approximately 10 mm Hg.3. All three compounds increased the renal lymph flow. Only PGE1 and noradrenaline markedly raised the equivalent concentration of PGE1 in the renal lymph.4. Complete block of α and β adrenergic receptors prevented the vasopressor effect and the rise in FF caused by noradrenaline but did not markedly reduce the diuretic and natriuretic effects nor the influence on renal lymph.5. Effects of PGE1 and of angiotensin were unaffected by α and β adrenergic block and atropinization did not prevent the release of PGE1‐like material or the diuresis caused by noradrenaline.6. It is suggested that the diuretic and natriutetic actions of noradrenaline are in large part attributable to the intrarenal action of this PGE1‐like substance of unknown origin.
The response of some sympathetic neurones to volleys in various afferent nerves
Authors: Coote J. H. , Perez‐Gonzalez J. F. 
Published: December 2014

1. Responses of sympathetic neurones to various afferent inputs have been analysed both in anaesthetized cats with intact neuraxis and in spinal cats.2. In anaesthetized cats electrical stimulation of low threshold group III afferent fibres in skin and muscle nerves inhibited sympathetic neurones and gave depressor responses. The silent period following a sympathetic reflex discharge is most likely due to inhibition brought on by a particular subgroup within this afferent group.3. High threshold group III and group IV afferent fibres excited sympathetic neurones and elicited pressor responses.4. Sympathetic reflex arcs could be temporally facilitated during the somatic afferent induced inhibition, by group IV, and to a lesser extent by group III volleys.5. Section of the spinal cord shortened the time course and lessened the degree of group III inhibition suggesting that suprasegmental pathways are involved in the long‐lasting depression following a reflex.6. Baroreceptor afferent stimulation inhibited group III‐ and group IV‐ evoked reflexes even with some temporal facilitation in the pathway.7. The special properties of the sympathetic reflex arcs and the relation of the results to other work on
B.P. reflexes are discussed. It is suggested that the group III and IV muscle afferents have a chemoreceptor function and are responsible for mediation of the pressor reflex during muscle exercise.