bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acetylcholine sensitivity of cerebellar neurones in the cat
Authors: Crawford J. M. , Curtis D. R. , Voorhoeve P. E. , Wilson V. J. 
Published: December 2014

1. Cholinomimetics, acetylcholine antagonists and some other compounds of pharmacological interest were administered electrophoretically near neurones within the vermal cerebellar cortex of anaesthetized (pentobarbitone) and unanaesthetized (cerveau isolé) cats.2. The neurones were identified by position within the cortex, spontaneous activity, and the responses to afferent and antidromic stimulation.3. Purkinje cells, but neither granule nor basket cells, were excited by cholinomimetics, and the acetylcholine receptors had muscarinic properties. Excitation was often preceded by depression of the spontaneous firing.4. Intravenously administered atropine and dihydro‐β‐erythroidine did not depress the synaptic excitation of cerebellar neurones evoked by impulses in mossy, climbing or parallel fibres.5. Acetylcholine is thus unlikely to be an excitatory transmitter within the feline cerebellum, particularly at mossy fibre‐granule cell synapses, despite the presence of relatively high levels of acetylcholinesterase within mossy fibre terminals.
The relation between external potassium concentration and the relaxation rate of potassium‐induced contractures in frog skeletal muscle
Authors: Foulks J. G. , Perry Florence A. 
Published: December 2014

1. Frog toe muscles and isolated fibres from frog semitendinosus muscles were allowed to develop maximum K‐contractures, and after reaching peak tension were transferred to media containing intermediate [K]0 (20‐40 m
M‐K). Under these circumstances, relaxation displayed an early rapid phase, and a subsequent slower phase whose magnitude and rate varied with [K]0. The removal of activator (calcium ion) from the sarcoplasm appears to have a potential‐dependent component.2. The relation between relaxation and [K]0 suggests that, with progressive depolarization, membrane sites from which calcium is initially released become converted into sites which are again capable of binding calcium and removing it from the sarcoplasm.3. The rate of relaxation of frog toe muscle after maximum K‐contractures can be either accelerated or retarded by abrupt alterations in [Ca]0 or by sudden replacement of the major extracellular anion. These effects are attributed to shifts in the relation between calcium rebinding and membrane potential.
Contractures in a superfused frog's ventricle
Authors: Lamb J. F. , McGuigan J. A. S. 
Published: December 2014

1. A new perfused preparation of frog's ventricle is described, whose main advantage is that there are short diffusion distances between the cells and the washing fluid.2. This preparation responds within a few seconds to alterations in sodium, potassium or calcium concentration, or alteration in the osmotic pressure of the bathing fluid. The speed of these alterations is consistent with the diffusional distances involved measured histologically.3. On depolarizing the preparation with Ringer + excess potassium, tension development starts at about ‐25 mV and is still increasing at ‐8 mV (the lowest voltage studied). As in earlier experimetns in frog ventricle (Niedergerke, 1956b) and in skeletal muscle (Hodgkin & Horowicz, 1960) the relation between potential and tension is very steep.4. Sodium free contractures (Lüttgau & Niedergerke, 1958) are very rapid in onset with this preparation. To maintain the tension developed, a rapid rate of washing is necessary for 1–2 min. After this, slow washing is sufficient. It is proposed that this is due to the leaching out of cellular sodium.5. In fresh preparations the twitch and maximum K contracture are of similar size when stimulated at 30/min in 1–2 m
M‐Ca. With the onset of hypodynamia the twitch tension falls, but the K contracture remains unaltered. In hypodynamic ventricles the sensitivity of the twitch to the ratio [Ca]/[Na]2 declines, whereas that of the K contractures remains unaltered. Hypodynamia therefore does not affect the contractile elements themselves.6. During the staircase phenomenon the K contracture and twitch size alter in a similar manner, as previously described by Niedergerke. The sodium free contracture, however, remains unaltered. This tends to favour the hypothesis that the staircase phenomenon is due to effects at the cell membrane rather than in the cell interior.7. Maximum K contractures occur at a [Ca]/[Na]2 ratio of about 0·7 × 10−4 m
M−1, a figure similar to that obtained in earlier experiments (Lüttgau & Niedergerke, 1958).8. The length—tension curves of K contractures are similar to those previously described for heart muscle, using single twitches to generate tension.9. Application of K free solutions produced no rapid contractures in this preparation.
Effects of oxygen tension on vascular and other smooth muscle
Authors: Smith D. J. , Vane J. R. 
Published: December 2014

1. The resting tension of various isolated intestinal and vascular smooth muscle preparations varied directly with the PO2 of the stream of blood used to bathe them.2. This effect was also obtained when artificial salt solution was used and was therefore not due to circulating hormones.3. The effect could not be antagonized by specific pharmacological antagonists such as hyoscine, phenoxybenzamine, hexamethonium, bromolysergic acid, diethylamide or mepyramine.4. The reactions of the isolated organs to catecholamines and 5‐hydroxytryptamine (5‐HT) were increased by the higher PO2.5. These results support the view that oxygen tension may play a major role in autoregulation of blood flow.
Hypercapnia and acetylcholine release from the cerebral cortex and medulla
Authors: Metz B. 
Published: December 2014

1. The cerebral cortex and medulla of fifty‐eight anaesthetized dogs released ACh spontaneously through push‐pull cannulae after perfusion with the anticholinesterase, sarin. Hypercapnia (12% CO2) evoked a significant release of ACh above the basic spontaneous level, from the medullary and cortical areas. Hypercapnia + hypoxia (12% CO2 + 8% O2), in combination, produced an ACh release comparable to hypercapnia; hypoxia (8% O2) had no effect in any region.2. Areas in the medullary reticular formation responsive to injections of CO2‐bicarbonate solutions (‘respiratory responsive areas’) produced a significant increase of ACh after exposure to hypercapnia or hypercapnia + hypoxia, over that obtained from either the ‘non‐respiratory responsive areas’ of the medulla or the cerebral cortex.3. The evidence supports the concept that ACh may participate as a neurotransmitter within the cerebral cortex and medulla. Also the results would suggest but do not prove, that a cholinergic factor may be a component in respiratory control under certain circumstances, such as exposure to hypercapnia.
The role of arterial oxygen tension in the respiratory response to localized heating of the hypothalamus and to hyperthermia
Authors: Findlay J. D. , Whittow G. C. 
Published: December 2014

1. Rectal temperatures, respiratory rates, arterial blood gas tensions, arterial pH and the percentage of red cells in arterial blood have been measured in the unanaesthetized ox in a cool environment (15/12° C, dry bulb/wet bulb [DB/WB]), in a hot, dry environment (40/21° C, DB/WB), during hyperthermia, during infra‐red irradiation, and during localized heating of the anterior hypothalamus. In some experiments the gas tensions and pH of mixed venous blood, and the percentage saturation of the arterial blood with oxygen, were also measured.2. In the cool environment at a mean rectal temperature (Tr) of 38·8° C and a respiratory rate (f) of 28/min the mean values obtained from six animals were: arterial oxygen tension (Pa, O2), 93 mm Hg; arterial carbon dioxide tension (Pa, CO2) 42 mm Hg; arterial pH 7·49; arterial oxygen saturation (Sa, O2) 94%; arterial oxygen capacity (Capa, O2) 13·6 vol.%; arterial packed cell volume (P.C.V.) 29%.3. Exposure to the hot, dry environment resulted in a small increase in the rectal temperature and thermal polypnoea, but there were no statistically significant changes in the blood gas tensions.4. During hyperthermia statistically significant increases occurred in rectal temperature, respiratory rate, Pa, O2, pH and arterial haematocrit, while the Pa, CO2 decreased. The venous oxygen tension (Pv̄, O2) decreased also, and the tentative conclusion was made that although the oxygenation of arterial blood remained unimpaired during hyperthermia, tissue hypoxia may supervene. At very high levels of deep body temperature, some evidence for a secondary decrease in Pa, O2 was obtained.5. Localized heating of the anterior hypothalamus caused an increase in respiratory rate and in Pa, O2. The Pv̄, O2 increased also. These changes were considered to be due to increased cardiac output and diversion of blood to the skin.6. During infra‐red irradiation of three animals at an environmental temperature of 40/21° C, the respiratory rate increased, but the Pa, O2 decreased.
Factors determining the maximal rate of organic anion secretion by the liver and further evidence on the hepatic site of action of the hormone secretin
Authors: O'Máille E. R. L. , Richards T. G. , Short A. H. 
Published: December 2014

1. Bromsulphthalein (BSP) was administered throughout the experiments at a constant rate well in excess of its excretory rate, to anaesthetized dogs in which the common bile duct had been cannulated. The maximal excretory rate of BSP into bile (BSP Tm) obtained in this manner was greatly elevated by choleresis arising from the administration of bile salt (usually taurocholate) at constant rate.2. When bile flow rate was increased in stages by raising the taurocholate administration rate, successive increments in BSP excretion rate were obtained up to a limiting value of about 3 times the original Tm. Beyond this point further increases in taurocholate administration rate caused either no further enhancement of BSP Tm or a decline in the extent of enhancement produced at a previous lower rate of infusion.3. When taurocholate maximal secretion was established first, the subsequent administration of BSP at progressively increasing rates led to reduction in the taurocholate secretion rate.4. Portal infusion of secretin at constant rate (usually 0·2 units/kg body wt. min) which caused substantial increases in bile flow rate, had no effect on BSP Tm. Increases of bile flow rate of the same order following constant taurocholate infusion produced marked elevation of the BSP Tm.5. These findings are discussed and the following conclusions reached:(a) The limiting factor in BSP maximal transfer is the concentration of BSP in bile; increased bile flow rate at the site of BSP excretion (canaliculi) produced by bile salt administration permits an increase in the original Tm to occur without the limiting biliary concentration being exceeded.(b) There is excretory competition between BSP and bile salt but over a certain range of bile salt administration the facilitatory effects of increased bile flow rate outweigh the inhibitory effects due to competition.(c) Since secretin administration had no effect on BSP Tm, it is likely that the hydrocholeresis it produces originates downstream from the canaliculi, i.e. in the bile ductules or ducts; this supports previous evidence obtained in a different manner.
A Purkinje shift in the spectral sensitivity of grey squirrels
Authors: Silver Priscilla H. 
Published: December 2014

1. The light‐adapted spectral sensitivity of the grey squirrel has been determined by an automated training method at a level about 6 log units above the squirrel's absolute threshold.2. The maximum sensitivity is near 555 nm, under light‐adapted conditions, compared with the dark‐adapted maximum near 500 nm found by a similar method.3. Neither the light‐adapted nor the dark‐adapted behavioural threshold agrees with electrophysiological findings using single flash techniques, but there is agreement with e.r.g. results obtained with sinusoidal stimuli.
Regulation of amino acid transport across intestines of goldfish acclimatized to different environmental temperatures
Authors: Mepham T. B. , Smith M. W. 
Published: December 2014

1. Serosal transfers of valine and threonine were measured using everted sacs of anterior intestine taken from goldfish acclimatized to different temperatures.2. Both valine and threonine were actively transported at incubation temperatures equal to or greater than the previous environmental temperature of the fish. There was also a positive serosal transfer of valine, but not threonine, at incubation temperatures below the previous environmental temperature of the fish.3. The mean stable transmural potentials and amino‐acid‐evoked potentials depended both on the temperature to which the fish had been acclimatized and on the temperature at which the sacs were incubated.4. There was a linear relation between the transmural potential and the serosal transfer of amino acid, one additional μmole of valine or threonine being transferred/2 hr incubation period for each 3 mV rise in potential. There was a less obvious correlation between the amino‐acid‐evoked potential and on serosal transfer of amino acid.5. Acclimatization of the goldfish intestine from 8 to 25° C, assessed by changes occurring in the transmural potential and serosal transfer of amino acids, tended to stabilize both parameters, but the compensation in each case was only partial.6. It is possible that the imbalance in transfer of valine‐like and threonine‐like amino acids, seen at incubation temperatures below the previous acclimatization temperature of the fish, has a special function in initiating the process of acclimatization to the new environmental temperature.
Gonadotrophin‐releasing activity of the median eminence at different ages
Authors: Campbell H. J. , Gallardo E. 
Published: December 2014

1. Intrapituitary infusions of extracts made from the median eminence of various species at different ages were found to excite secretion of gonadotrophic hormone as shown by consequent ovulation, presumably due to their content of luteinizing hormone‐releasing factor (LRF).2. Extracts from very immature animals (e.g. new‐born rabbits and rats; 1‐2‐month‐old calves) were found to be highly active with regard to LRF content.3. Extracts from foetal rabbits at 20 days of gestation showed no evidence of containing LRF.4. It is suggested that (a) LRF may have a trophic action upon the anterior pituitary gland during the pre‐puberal phase of life, and that (b) the first formation of LRF coincides with the development of the primary plexus of the pituitary portal system.
The threshold conditions for initiation of action potentials by excitable cells
Authors: Noble D. , Stein R. B. 
Published: December 2014

1. The relation between the strength and duration of a just threshold stimulus (strength—duration curve) is analysed for an excitable membrane polarized uniformly and for an excitable cable polarized at one point.2. The effect on the strength—duration curve of non‐linearity in the membrane current—voltage curve has been analysed. The strength—duration curve can be derived if the membrane current—voltage relation is independent of time. The effects of changes in the current—voltage curve with time due to the existence of a finite membrane activation time and membrane accommodation are analysed.3. The strength—duration curve for the Hodgkin—Huxley membrane equations (Hodgkin & Huxley, 1952) is compared to that of Hill's (1936) two‐time constant model.4. The relation between membrane current—voltage curves and those for a point‐polarized cable are derived for the steady‐state condition. The cable properties tend to linearize the current—voltage curve and to sharpen the voltage threshold.5. The strength—duration curve for a point‐polarized cable whose membrane obeys the Hodgkin—Huxley equations is computed numerically. There is an additional large effect on the cable strength—duration curve arising from the redistribution of charge during passage of a constant current; and the resulting strength—duration curve lies within the range of curves predicted by Hill's model.6. The conditions required for a constant charge threshold (Hodgkin & Rushton, 1946) are shown to be satisfied for short, intense stimuli applied to a cable at one point.7. The results are discussed with reference to the experimental studies available.
The effect of amino acids on the intestinal transport of L‐ and D‐xylose in vitro
Authors: Duthie H. L. , Hindmarsh J. T. 
Published: December 2014

1. The intestinal transport of
D‐xylose by sacs of everted small intestine of the hamster is partially inhibited by
L‐histidine in concentrations of 5, 10 and 20 m
M but not of 2 m
M.2. 20 m
M concentrations of
D‐histidine and
L‐methionine also produce inhibition.3. The inhibition is not due to an alteration in water transport or to a change in pH of the incubating medium.4. The rate of the intestinal transport of
L‐xylose is about ¼ of the rate of
D‐xylose transport and is unaffected by a 20 m
M concentration of
L‐histidine.
The effects of urea and hydrochlorothiazide on the renal functions of rat and domestic fowl
Authors: Dicker S. E. , Eggleton M. Grace , Haslam J. 
Published: December 2014

1. Rats and domestic fowls were given by stomach tube water, urea and hydrochlorothiazide, alone or in combination, in the following amounts: water, 5 ml./100 g; urea, 4 ml. of 1·5% solution + 1 ml. water/100 g; hydrochlorothiazide, 4 ml. of 1·5% urea solution + 1 ml. containing 0·1 mg hydrochlorothiazide/100 g.2. The onset of water diuresis was faster in the fowl than in the rat. It was accompanied by a lower rate of excretion of osmotically active solutes in the former than in the latter. The rate of excretion of creatinine in rats was fourfold that in birds.3. After urea administration, the amount of urea excreted by the fowl was about one fifth that excreted by the rats. While urea produced in rats an osmotic diuresis, with enhanced excretion of osmotically active solutes, in birds it had little effect on either urine flow or solutes excretion.4. Administration of hydrochlorothiazide in rats produced a moderate antidiuresis accompanied by a marked increased excretion of Na and K; in birds, a small increase in the excretion of Na and K but no effect on the urine flow.5. The differences observed between rats and birds can be attributed to the poor development of filtration rate and the absence of a well developed counter‐current system in the fowl.
The relation between the concentrations of bicarbonate and protein in the pancreatic juice in the dog
Authors: Henriksen F. W. , Worning H. 
Published: December 2014

1. In accordance with the admixture theory of the exocrine pancreatic secretion a linear relation between concentrations of bicarbonate and protein in the pancreatic juice is to be expected.2. Pancreatic juice was obtained through a Thomas cannula in three unanaesthetized dogs during digestion of a meal.3. The actual concentration of bicarbonate and protein showed a good approximation to a straight‐line relation.4. The calculated concentration of bicarbonate in the distal secretion was nearly identical with the highest concentration of bicarbonate obtained in the pancreatic juice after stimulation with secretin.
The effect of tiring the forearm muscles in different ways on venous blood pH, PCO2 and standard bicarbonate
Authors: Barcroft H. , Youlten L. J. F. 
Published: December 2014

1. The changes in venous blood pH, pCO2 and standard bicarbonate caused by tiring the forearm by (a) rhythmic work with free circulation, (b) rhythmic work with ischaemic circulation, were determined using the Astrup apparatus.2. For rhythmic work, opening and shutting the hand as quickly as possible for 2 min, the averaged results on six subjects were: pH fell 0·19 units; pCO2 (after full oxygenation of venous blood) rose 52 mm Hg; standard bicarbonate fell 2·9 m‐equiv/l.3. For rhythmic work during ischaemia and accompanied by pain, the averaged results on six subjects were: pH fell 0·19 units; pCO2 (after full oxygenation of venous blood) rose 26 mm Hg; standard bicarbonate fell 6·3 m‐equiv/l.4. These results are compared with those obtained in an earlier investigation on the effect of strong hand grips for 1 min.
The effects of acute haemorrhage on respiration in the cat
Authors: D'Silva J. L. , Gill D. , Mendel D. 
Published: December 2014

1. The effect of haemorrhage on minute ventilation, arterial blood pH and end‐tidal CO2 has been investigated in cats anaesthetized with Nembutal. There was no change in minute ventilation with alteration of blood pressure above 100 mm Hg. Below this level ventilation progressively increased, the minute ventilation at 60 mm Hg being 33% above that at 100 mm Hg. The increase in minute ventilation was always associated with a fall in end‐tidal CO2 and a decrease in arterial blood hydrogen ion concentration.2. The effects were not influenced by vagotomy, but were abolished by carotid sinus denervation or carotid body destruction. After vagotomy and sinus denervation or aortic and carotid chemoreceptor destruction, haemorrhage resulted in a depression of respiration.3. The changes in arterial blood pH and end‐tidal CO2 did not occur without a change in minute ventilation.4. When the changes in arterial blood pH during haemorrhage were prevented by administration of CO2 there was a marked increase in minute ventilation. It is concluded that the respiratory drive to respiration in the cat during haemorrhage is controlled mainly by carotid body chemoreceptors and that the resultant alkalaemia decreases the respiratory response.
Algebraical summation in synaptic activation of motoneurones firing within the ‘primary range’ to injected currents
Authors: Granit R. , Kernell D. , Lamarre Y. 
Published: December 2014

1. In intracellular studies of cat lumbar motoneurones constant synaptic stimuli such as stretch, contraction or a high‐frequency stimulation of a cut afferent nerve have been superimposed on firing in response to injected currents.2. As long as the slope relating spike frequency to injected current remained constant, which by definition is the ‘primary range’ of firing, algebraical summation of superimposed synaptic stimulation prevailed. Added quantities in these experiments were then between 2·0 and 56·2 impulses/sec for excitation, between ‐2·8 and ‐21·8 impulses/sec for inhibition.3. Data were obtained correlating firing rates with amount of synaptic potential and current respectively.4. Theoretical implications are dealt with in the Discussion.
The effect of orientation on the visual resolution of gratings
Authors: Campbell F. W. , Kulikowski J. J. , Levinson J. 
Published: December 2014

1. Visual resolving power is known to be poorer for objects oriented obliquely as compared with horizontal and vertical orientations. Experiments were designed to evaluate the optical and neurophysiological factors involved.2. Gratings with a sinusoidal light distribution were generated on the face of an oscilloscope. Spatial frequency and contrast could be varied while keeping the mean luminance of the grating constant.3. Using a homatropinized eye with an artificial pupil and carefully corrected refraction, high resolution in the vertical and horizontal meridians as compared with the oblique meridians was found for gratings ranging in spatial frequency from 1 to 35 c/deg.4. It is concluded from the similar behaviour of low and high frequency gratings that neither focus errors nor optical aniseikonia can account for these findings.5. Additional proof that optical factors cannot significantly account for these preferred directions of resolution was obtained by forming interference fringes directly on the retina using a neon—helium laser as a coherent light source.6. Similar orientational changes in resolution were found by by‐passing the dioptrics with interference fringes. It is concluded that the effect is due to some orientational inequality in the visual nervous system.