bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial synaptic distribution of recurrent and group Ia inhibitory systems in cat spinal motoneurones
Authors: Burke R. E. , Fedina L. , Lundberg A. 
Published: December 2014

1. The reversal potentials of several types of inhibitory post‐synaptic potentials (IPSPs) have been studied in cat spinal motoneurones with and without modification of intracellular chloride ion (Cl−) concentration. Single barrel intracellular micropipette electrodes have been used.2. When studied with potassium citrate filled micropipettes, the reversal potential for IPSPs evoked by stimulation of antagonist group Ia afferents is the same as that for recurrent IPSPs evoked by antidromic stimulation of motoneurone axon collaterals, confirming earlier observations (Araki, Ito & Oscarsson, 1961; Coombs, Eccles & Fatt, 1955).3. Studied with potassium chloride filled micropipettes. the reversal potential for the group Ia IPSP was found to be different from that for the recurrent IPSP when the amount of Cl− diffusing or iontophoretically injected into the motoneurone was small. The amount of difference in reversal potential varied from cell to cell but when present the group Ia IPSP reversed to a depolarizing potential more readily than the recurrent IPSP in all cases.4. Interaction between recurrent IPSPs and monosynaptic excitatory post‐synaptic potentials (EPSPs) was also studied and the amount of non‐linearity of potential summation was measured.5. The results are consistent with the hypothesis that the terminations of Renshaw cells responsible for the recurrent IPSP are located largely on the proximal dendrites of motoneurones, while the terminations of the interneurones generating the group Ia IPSP appear to be closer to or on the cell somata.
Contractions of the caudal region of the oesophagus of the cat
Authors: Titchen D. A. , Wheeler J. S. 
Published: December 2014

1. The motility of the most caudal part of the oesophagus has been investigated in cats which were decerebrated, had the whole of the central nervous system pithed or were anaesthetized with chloralose.2. Contractions of the most caudal region of the oesophagus were evoked by its stretch and the presence in it of HCl. These reactions were obtained in all types of preparations used.3. In decerebrate preparations oesophageal contractions occurred in response to the introduction of acid into the stomach. These were not obtained after the vagus ṅerves had been cut.4. Slight degrees of gastric distension stimulated oesophageal contractions, greater distension was inhibitory.5. Both reductions in oesophageal activity and contractions of the oesophagus were obtained with different parameters of stimulation of efferent vagal fibres.6. Excitatory and inhibitory effects on the oesophagus were obtained from stimulation of the central end of the vagus nerves cut in the abdomen or in the neck.7. In totally pithed preparations of cats stretch of one region of the oesophagus was found to modify the activity of a distant region of the oesophagus cranial or caudal to the site of distension.8. The reactions of the caudal oesophagus were abolished by atropine.9. The importance of vago‐vagal reflexes in the modification of basically direct oesophageal responses has been discussed.
Actions of dinitrophenol and some other metabolic inhibitors on cortical neurones
Authors: Godfraind J. M. , Kawamura H. , Krnjević K. , Pumain R. 
Published: December 2014

1. In cats under methoxyflurane, DNP and other metabolic inhibitors were tested on cortical neurones by iontophoresis from micropipettes.2. DNP, dinitro‐o‐cresol, iodoacetate, pentachlorophenol and oligomycin (uncouplers or inhibitors of oxidative phosphorylation), as well as moderate anoxia, blocked selectively and reversibly spontaneous firing and discharges evoked by ACh; responses evoked by glutamate were facilitated by moderate doses of DNP and blocked only by large amounts.3. Azide, cyanide, ouabain and strophanthidine had a mainly excitatory effect; the cardiac glycosides tended to depress more strongly responses to glutamate.4. Intracellular observations showed that DNP causes a sharp fall in electrical excitability, associated with a hyperpolarization and fall in membrane resistance.5. The hyperpolarizing action of DNP had a mean reversal level (EDNP) nearly 30 mV more negative than the resting potential; EDNP was identical with the mean reversal level for the depolarizing action of ACh, measured on the same cells.6. DNP had its usual hyperpolarizing effect on neurones whose IPSPs had been made positive by raising the internal [Cl]; the mean EIPSP was over 30 mV more positive than EDNP.7. It is concluded that DNP lowers excitability by raising the membrane conductance to K+ (gK) and that it blocks ACh responses selectively because ACh has a precisely opposite action on these neurones.8. In the Discussion, it is suggested that the rise in gK is mediated by an increase in internal free Ca2+, caused by a slowing of mitochondrial activity, and that a similar mechanism may play a significant role in general anaesthesia.
Thermoregulation in intensively lactating cows in near‐natural conditions
Authors: Berman A. 
Published: December 2014

1. Thermoregulatory reactions of lactating cows (33 kg milk/day) have been measured in summer (25–39° C) and in winter (9·5–24° C) at 3 hr intervals, during four nychthemeral (24 hr) cycles in each season.2. The rectal‐to‐tympanic temperature gradient increased with rising body temperatures. The seasonal changes were larger for the rectal temperatures than for the tympanic membrane temperatures. These and the significantly lower correlations between rectal temperatures and regulatory responses suggest that in the ruminant rectal temperatures are considerably affected by rumen metabolism and do not represent a reliable index of the regulated temperature.3. In the winter the regulatory responses were correlated with skin temperatures only. In the summer responses were correlated with both skin and tympanic temperatures, excepting for skin water loss.4. The seasonal difference in the effects of skin and tympanic temperatures on regulatory responses was associated with a small change in mean tympanic temperature. The twofold larger nychthemeral fluctuation in the summer tympanic temperature is suggested to cause the seasonal difference in the thermoregulatory mode.5. The winter range of nychthemeral fluctuations in tympanic temperature suggests a range of permitted core thermolability. A wider permitted core thermolability in summer is unlikely to be a mechanism of acclimatization in the cow.
Local blood flow, cerebrovascular autoregulation and CO2 responsiveness in the rabbit hypothalamus
Authors: Cranston W. I. , Rosendorff C. 
Published: December 2014

1. Local blood flow has been measured in the hypothalamus and other areas of the brain in the conscious rabbit, by measuring the rate of clearance of small volumes (2·5–10 μl.) of a saline solution of the inert tracer 133Xe injected locally.2. Increasing the arterial PCO2 caused a mean rise in the hypothalamic blood flow of 34%.3. The hypothalamic blood flow remained relatively constant over a mean arterial blood pressure range of 41–140 mm Hg.4. Hypothalamic blood flow was relatively unaffected by anaesthesia with intravenous pentobarbitone; by contrast, blood flow in the cerebral cortex was greatly reduced.5. It is concluded that the technique is a valid and useful one, since CO2 responsiveness and autoregulation is maintained. Different areas of grey matter have different flow rates, and vary in their responsiveness to barbiturate anaesthesia.
Activation of transmitter release by strontium and calcium ions at the neuromuscular junction
Authors: Meiri U. , Rahamimoff R. 
Published: December 2014

1. The interaction between Ca and Sr ions on quantal transmitter release at the frog neuromuscular junction was studied, using conventional electrophysiological techniques.2. While Ca ions always activate transmitter release, the activating action of Sr ions depends on the Ca ion concentration in the medium; at low [Ca], strontium ions enhance the release, but at higher [Ca] they inhibit it. It is postulated that there is a [Ca] at which Sr ions do not affect transmitter liberation.3. When Sr activates release, its effect and the effect of Ca add in a more than linear fashion.4. Magnesium ions inhibit the release induced by Sr.5. The results can be explained by assuming that Ca and Sr act on the same site, at some stage of the process of quantal transmitter release. The affinity of both ions towards the sites is approximately the same, but the effectiveness of Sr is much smaller.
The short‐latency projection from the baboon's motor cortex to fusimotor neurones of the forearm and hand
Authors: Clough J. F. M. , Phillips C. G. , Sheridan J. D. 
Published: December 2014

1. The corticospinal connexions that are responsible for the firing of fusimotor impulses at short latency in response to brief, high‐frequency stimulation of the baboon's motor cortex have been investigated by micro‐electrode recording from antidromically identified fusimotor neurones of the forearm and hand.2. Of nineteen fusimotor neurones investigated by intracellular recording, six showed EPSPs at monosynaptic latency.3. In extracellular records, the latency of firing of an early fusimotor impulse was always too long to be explained by monosynaptic excitation by the corticospinal D volley, but could be explained by monosynaptic excitation from an I volley.4. Four of the nineteen intracellularly recorded fusimotor neurones showed short‐latency (?disynaptic) IPSPs in response to brief high frequency cortical bursts.
Modification of the reflex response to stimulation of carotid sinus baroreceptors during and following stimulation of the hypothalamic defence area in the cat
Authors: Humphreys P. W. , Joels N. , McAllen R. M. 
Published: December 2014

1. The effects of stimulation of the hypothalamic defence area on carotid sinus baroreceptor reflexes have been investigated by examining the cardiovascular responses to a 15 sec period of increased pressure within the vascularly isolated carotid sinus before, during, and immediately following a 25 sec period of hypothalamic stimulation.2. Identification of the hypothalamic defence area was based on the occurence of atropine‐sensitive muscle vasodilatation. Electrode positions were confirmed by histological examination.3. During hypothalamic stimulation the reflex fall in blood pressure resulting from a rise in sinus pressure was found to be undiminished whether sinus pressure was raised at the onset or at the 10th sec of hypothalamic stimulation.4. By contrast, in at least half the cats in which a reflex bradycardia could be evoked from the sinus, this bradycardia was largely if not completely suppressed during hypothalamic stimulation. This suppression of reflex bradycardia occurred when sinus pressure was raised at the onset as well as at the 10th sec of stimulation.5. During the first 5 sec after hypothalamic stimulation the hypotensive response to an increase in carotid sinus pressure was much reduced; on the other hand the reduction in heart rate was exaggerated, sometimes to a very marked degree.6. The results suggest that stimulation of the hypothalamic defence area can modify baroreceptor reflexes and that this modification can include selective alterations in the various components of the reflex response.
Studies of temporal frequency adaptation in visual contrast sensitivity
Authors: Smith Robert A. 
Published: December 2014

1. A short adaptation to sinusoidal flicker produces a temporary elevation in the temporal contrast threshold of a human observer.2. The frequency specificity of this adaptation effect is much less than that observed with adaptation to spatial frequencies; thus it does not seem warranted to postulate the existence of distinct channels for the detection of specific temporal frequencies, as has been done in the case of spatial frequencies (Blakemore & Campbell, 1969).3. At low frequencies, a substantial adapting modulation is necessary to produce an effect, but at high frequencies an effect can be seen even with adaptation which is below threshold (as determined by the method of adjustment).4. This subthreshold adaptation appears to explain the observation that thresholds set by the method of adjustment rise by as much as a factor of two during the first minute of exposure.5. No interocular transfer of the adaptation effect was observed.6. Adaptation first appears at mesopic luminances, but its appearance is not dependent on the change from rod to cone vision. Under several conditions, however, the first appearance of flicker adaptation did coincide with a change in the deLange curve, which is attributable to the appearance of the antagonistic surround of visual receptive fields. Thus it was hypothesized that the surround is essential for adaptation.
Sodium chloride absorption and solute‐linked water flow across the epithelium of the coprodeum and large intestine in the normal and dehydrated fowl (Gallus domesticus). In vivo perfusion studies
Authors: Bindslev Niels , Skadhauge Erik 
Published: December 2014

1. The transmural net flow of salt and water in the coprodeum and large intestine of normal and dehydrated hens was investigated by means of an intraluminal in vivo perfusion technique. The lumen was perfused with hypo‐, iso‐, and hyperosmotic salt solutions. Polyethylene glycol (PEG 4000) and [14C]inulin served as water markers.2. The maximal net Na+ flow (JNa) from the mucosal to the serosal side was nearly the same in the two states of hydration: normal birds 308 μ‐equiv/kg.hr, dehydrated birds 281 μ‐equiv/kg.hr, while the JNa was half maximal at luminal Na+ concentrations of 99 and 43 μ‐equiv/l. respectively. The ‘affinity’ for Na+ in the dehydrated bird was thus twice that in the normal bird. K+ was secreted into the gut lumen at a constant rate against the electrochemical gradient, JK = −97 μ‐equiv/kg.hr (
S.E. = 5). Clμ was absorbed from lumen to plasma down the electrochemical gradient with JCl ranging from 0 to 94 μ‐equiv/kg.hr. The low JCl was observed at low luminal NaCl concentrations when the JNa was also small.3. The solute‐linked water flow, Jvs, occurring in the absence of an osmolality difference across the epithelium, was 1·1 μl. H2O/μ‐equiv Na+ in normal birds and 1·5 in dehydrated birds. The Jvs was calculated as an operational parameter in experiments with luminal osmolalities different from plasma osmolality by subtracting the water flow observed in an experiment without Na+ in the perfusion fluid from the water flow in an experiment with Na+ containing perfusion fluids, both fluids being of the same osmolality. Jvs was maximal at luminal osmolalities close to plasma osmolality. These observations are compatible with the hypothesis that the Jvs is due to an osmotic flow into a confined region between the cells.4. When the perfusion rate was lowered from 5‐9 ml./kg.hr to 0·8–1·0 the incoming perfusion fluid osmolality at which net water flow across the epithelium was zero went up from 100 to 180 m‐osmolal higher than plasma osmolality. This observation suggests that a significant fraction of ureteral urine in the dehydrated bird may be absorbed in the coprodeum and large intestine.
The parasympathetic secretory nerves of the lacrimal gland of the cat
Authors: Arenson M. S. , Wilson H. 
Published: December 2014

1. Electrical stimulation of the brain stem of the anaesthetized cat induces a secretion from the lacrimal gland.2. The secretion is abolished either by Vidian nerve section or by the application of nicotine to the sphenopalatine ganglion.3. In contrast to stimulation of the peripheral end of the cut Vidian nerve, stimulation of the central end induces lacrimal secretion.4. A new pathway is proposed in the light of the experimental findings.
Adrenal catecholamine secretion during stimulation of the nasal mucous membrane in the rabbit
Authors: Allison D. J. , Powis D. A. 
Published: December 2014

1. Left adrenal venous blood was collected in anaesthetized rabbits and analysed for catecholamine content by either a fluorimetric technique or a bio‐assay method using the blood pressure of the pithed rat.2. Stimulation of the nasal mucous membrane with ether vapour or water caused apnoea, bradycardia, a rise in arterial blood pressure and an increase in adrenal medullary catecholamine secretion.3. During the pre‐stimulation control periods adrenaline constituted 66% of the total catecholamine present in adrenal venous blood and noradrenaline 34%. These proportions altered during stimulation of the nasal mucous membrane to 72 and 28% respectively. Electrical stimulation of the left splanchnic nerve produced a secretion composed almost entirely of adrenaline.4. The increased catecholamine output elicited during stimulation of the nose occurred in animals whose pulmonary ventilation was maintained constant by means of a pump. It was abolished, however, by local anaesthesia of the nasal passages or by surgical division of the left splanchnic nerve.5. The increased secretion of catecholamines is therefore reflex in nature, and evidence is presented that it is the result of a primary reflex from the nose.
The mechanism of thyroxine transfer from plasma to tissue binding sites
Authors: Hillier A. P. 
Published: December 2014

1. An examination has been made of the uptake of thyroxine by rat livers perfused with very dilute solutions of thyroxine‐binding globulin (TBG) and thyroxine‐binding pre‐albumin (TBPA).2. Under these circumstances the rate of transfer of thyroxine to the liver is very similar to the rate of thyroxine dissociation for both TBG and TBPA.3. It is concluded that thyroxine transfer from plasma to tissue‐binding sites involves its initial release into the free state and not, as has been suggested, directed exchange.
The effect of adrenaline and noradrenaline on the blood flow, electrical conductance and external secretion of the pancreas
Authors: Barlow T. E. , Greenwell J. R. , Harper A. A. , Scratcherd T. 
Published: December 2014

1. Adrenaline and noradrenaline cause a biphasic change in the transverse electrical conductance across the cat pancreas. After a latent period of from 5 to 30 sec a phase of decreased conductance lasting about 30 sec occurs which gives way to a phase of increased conductance lasting from 5 to 8 min.2. Coincidentally with the phase of decreased conductance, vasoconstriction and a reduction in blood flow occurs and an increased blood flow with the phase of increased conductance. The blood flow and conductance records run a parallel time course.3. Weight for weight adrenaline produces changes of greater magnitude than noradrenaline.4. The phase of decreased conductance and blood flow was abolished by an α‐receptor blocking agent and the phase of increased conductance and blood flow by a combination of α‐ and β‐receptor blocking agents.5. Inhibition of the volume rate of secretion coincident with the phase of decreased conductance followed rapid intravenous injection of adrenaline or noradrenaline. During the phase of increased conductance secretion either returned to control values or was transiently augmented.6. Inhibition of secretion occurred after α‐receptor blockade in the absence of vasoconstriction, suggesting that the catecholamines have a direct action on the cell.7. β‐receptor blockade increased the effectiveness of adrenaline to inhibit pancreatic secretion.When the effects of the catecholamines on secretion were tested, secretion was always induced by secretin.
The binomial nature of transmitter release at the crayfish neuromuscular junction
Authors: Johnson E. W. , Wernig A. 
Published: December 2014

1. Transmitter release at excitatory junctions on the opener muscle of the crayfish dactyl was studied by recording junctional potentials with extracellular micro‐electrodes.2. At low temperatures, evoked release was dispersed sufficiently in time for potentials produced by individual quanta to be counted, and the mean (m) and variance (σ2) of the quantum content distribution for a series of trials measured directly. These values were used to calculate the average probability of quantal release (p), assuming a binomial distribution.3. For all values of m and p, the observed release pattern (number of 0, 1, 2, 3,... quantal releases during a series of trials) was approximated closely by the corresponding binomial distribution. However, Poisson predictions differed significantly from the observed quantal distribution for values of p > 0·2.
Release of an antidiuretic substance by bradykinin in the rat
Authors: Harris M. C. 
Published: December 2014

1. Water‐loaded rats under ethanol anaesthesia were used to determine whether bradykinin releases ADH and whether the release is a reflex response to hypotension or the result of direct stimulation of the central nervous system by the peptide.2. Intravenous injections of bradykinin caused hypotension followed by prolonged antidiuresis; both responses were dose dependent.3. The antidiuresis caused by bradykinin could not be accounted for by hypotension alone. Haemorrhage and intravenous injections of isoprenaline, which caused falls in arterial blood pressure similar to those caused by bradykinin, produced only short‐lasting antidiuretic responses.4. Intracarotid injections of bradykinin caused antidiuresis with little or no preceding hypotension. No antidiuresis was produced by intracarotid injections of isoprenaline.5. After intravenous injection of bradykinin, small amounts of ADH were identified in whole blood and, on a few occasions only, in concentrated urine. However, ADH was not detected in blood extracts.6. After intravenous injection of nicotine in doses which caused antidiureses similar to that caused by bradykinin, ADH was regularly detected in large amounts in blood extracts and in unconcentrated urine.7. Bradykinin did not cause prolonged antidiureses when injected into a rat with congenital diabetes insipidus.8. ADH release was not increased when isolated rat neural lobes were incubated with bradykinin although release was elevated by an increase in the K+ concentration of the incubation medium.9. It is suggested that bradykinin causes release of an antidiuretic substance by a direct action on the central nervous system. The possibility that this substance is ADH is discussed.