bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionic dependence of luteinizing‐hormone‐induced steroidogenesis in the rabbit ovary.
Authors: Bedwani J R , Wong P Y
Published: December 2014

1. Investigations were made into the influence of the ionic environment on the steroidogenic response of the rabbit ovary to luteinizing hormone (LH). 2. Removal of Ca2+ from the medium was without effect on the response to LH. A similar result was obtained in Ca2+‐free medium containing EGTA. 3. A tenfold increase in [Ca2+]o to 25.6 mM, or the addition of La3+ or Eu3+ (0.25 mM) to medium containing the normal concentration of Ca2+, caused a marked inhibition of the response to LH. 4. Removal of Na+ from the medium, and replacement by choline, had no effect on the response to LH. Replacement of Na+ by Li+ inhibited the response to the hormone strongly, but the addition of 4 mM‐Li+ to normal medium was without effect. 5. Removal of K+ from the medium inhibited LH‐induced steroidogenesis, whereas a twentyfold increase in [K+]o to 100 mM had no effect. The response to LH was also unaffected by the absence of Cl‐. 6. Ouabain (10(−4) M) inhbited the response to LH, but nupercaine (10(−4) M) was without effect. 7. The inhibitory effect of ouabain was reversed by the addition of 2 mM‐NADP+ to the medium. In contrast, the inhibitory effect of Eu3+ persisted in the NADP+‐rich medium. 8. It is suggested that the intracellular ratio of Na+ or Li+) to K+ is important for the expression of the steroidogenic response of the ovary to LH. Altered concentrations of these ions might affect the formation or availability of NADP+. The inhibitory effects of high [Ca2+]o and lanthanide ions, however, are probably due to inhibition of hormone‐stimulated adenyl cyclase.
The effect of 2‐deoxy‐D‐glucose and D‐glucose on the efferent discharge rate of sympathetic nerves.
Authors: Niijima A
Published: December 2014

Efferent discharges were recorded from nerve filaments dissected from the adrenal and renal nerves in the rabbit. 2. An increase in discharge rate was observed in the adrenal nerve filaments following I.V. administration of 2‐deoxy‐D‐glucose (2‐DG). No change in discharge rate after 2‐DG infusion was observed in the renal nerve filaments. 3. A decrease in discharge rate of the adrenal nerve filaments was observed after I.V. injection of glucose, but there was no change in the activity of renal nerve filaments. 4. Transection of the spinal cord abolished the adrenal nerve response to the systemic administration of 2‐DG and glucose. 5. It is suggested that there might be a pathway from the hypothalmic area to the adrenal nerve cells of the spinal cord, but not to the renal nerve cells, through which activity of the adrenal nerve might be changed in response to 2‐DG and glucose infusion.
The relative unimportance of the temporal pattern of the primary afferent input in determining the mean level of motor firing in the tonic vibration reflex.
Authors: Matthews P B
Published: December 2014

1. A study has been made of the effect of varying the temporal arrangement of the mechanical stimuli used to elicit the tonic vibration reflex in the soleus muscle of the decerebrate cat. The reflex was elicited by brief mechanical pulses, applied repetitively, either as a regular series or, at the same mean frequency, in groups of 2, 3 or 4 pulses with a separation between the pulses of 3‐5 msec. Mean frequencies of 140/sec and 100/sec were used. The amplitude of the pulses was such that it could be presumed that each pulse excited every Ia fibre from soleus to discharge a spike, irrespective of the patterning employed. 2. Alterations in the stimulus pattern produced only minimal alterations in the size of the resultant reflex recorded myographically. The grouped stimulation regularly tended to produce the larger effect, but even with groups of 4 at 100/sec the modal effect was only 10% of the pre‐existing response; expressed another way this was equivalent to an increase of 11 Hz in the mean frequency of stimulation. Thus under these conditions grouping the stimuli cannot have had an appreciable effect either in increasing the firing frequency of those motoneurones which were already active, or in recruiting those which were initially quiescent. 3. Recording from individual motor units with fine electrodes placed on the surface of the muscle showed that they were not significantly changing their frequency of firing on altering the pattern of stimulation. 4. Gross electromyographic recording showed that the motor discharge was locked in time to the mechanical stimuli and of appropriate latency for it to be presumed that the actual discharge of impulses was triggered by Ia monosynaptic action. 5. Similar insensitivity to the temporal pattern of the afferent input was found when the motoneurones were excited via two separate channels, one being the pulsed mechanical stimulation of soleus, the other being the weak electrical stimulation of the nerve to the medial head of gastrocnemius; altering the relative timing of the two sets of stimuli had little effect on the myographic result. 6. Thus, during tonic firing the timing of the motor output reflects the timing of the afferent input while the mean motor output reflects the mean value of the afferent input, as seems physiologically appropriate. The latter finding is, however, paradoxical; as detailed in an appendix the amount of motor firing produced by synchronous Ia monosynaptic action might be expected to increase on grouping the stimuli and so apparently favouring e.p.s.p. summation.
Effect of steroid depletion on the response of toad bladder to vasopressin.
Authors: Debnam E S , Hewitt S , Snart R S
Published: December 2014

1. We have investigated the water transport and short‐circuit current (s.c.c.) response to vasopressin (1 mu./ml. and 100 mu./ml.) in isolated toad urinary bladders (Bufo marinus) following overnight incubation in the presence or absence of steroid‐containing Ringer solution. 2. The water transport response to the lower dose of vasopressin (1 mu./ml.) was considerably reduced in 'steroid depleted' conditions, wheras the response to the higher dose of vasopressin (100 mu./ml.) was not similarly affected. 3. Aldosterone 3. Aldosterone 3. Aldosterone (10(‐7)M) potentiated the water transport response to the lower dose of vasopressin (1 mu./ml.) but had no effect on the response to the higher dose (100 mu./ml.). 4. There was no effect of 'steroid depletion' or aldosterone treatment on the vasopressin s.c.c. response when measured as a percentage increase above basal levels. 5. In 'steroid depleted' conditions vasopressin (1 mu./ml.) maximally stimulated Na+ transport (s.c.c.) but a higher dose of vasopressin (100 mu./ml.) was required for maximum water transport. 6. We have failed to obtain any potentiation effect of corticosterone (10(‐7)M) on the water transport or s.c.c. response to vasopressin (1 mu./ml.).
The responses of muscle spindles in sheep extraocular muscles.
Authors: Browne J S
Published: December 2014

1. Responses from de‐efferented muscle spindles in sheep extraocular muscles have been recorded in the Gasserian ganglion using glass microelectrodes. 2. The afferent fibre conduction velocities ranged from 32 to 106 m/sec and most were intermediate. The distribution was unimodal. 3. The afferent responses to ramp stretches and longitudinal vibration of the muscle could not be divided into two groups, but both the dynamic indices and vibration sensitivities of the afferents increased with their conduction velocities. 4. Injection of suxamethonium did not help to classify afferents with intermediate conduction velocity. 5. It is concluded that the afferents from sheep extraocular muscle spindles form a single population whose properties are correlated with their nerve fibre diameters.
Synaptic actions on mitral and tufted cells elicited by olfactory nerve volleys in the rabbit.
Authors: Getchell T V , Shepherd G M
Published: December 2014

1. A unitary study has been carried out of mitral and tufted cell responses to olfactory nerve volleys in the olfactory bulb of rabbits lightly anaesthetized with urethane‐chloralose. 2. With volleys of different strengths, some mitral cells responded with a spike whose latency decreased considerably as the strength increased (elastic response); other cells responded at an invariant latency (inelastic response). The former may reflect diffuse olfactory nerve inputs to the dendritic tufts in the olfactory glomeruli, while tha latter may reflect input from discrete bundles of fibres. 3. The shortest spike latencies are consistent with monosynaptic excitation by the olfactory nerves; longer latencies may be due to longer pathways through the nerves, or polysynaptic pathways within the glomerular layer. 4. Facilitation, in terms of lower threshold and shorter spike latency, was found when testing with paired volleys of weak intensity at relatively short intervals (less than 40 msec). Suppression, in terms of raised threshold, longer latency and briefer repetitive discharges, was found at intervals up to several hundred msec. The facilitation and suppression are consistent with the hypothesis of synaptic excitation and inhibition, respectively, mediated through interneurones in the olfactory bulb. 5. Presumed tufted cells were similar in response properties to identified mitral cells. 6. Intracellular recordings revealed long‐lasting hyperpolarization and in some cases, an initial depolarization leading to spike initiation, in response to an olfactory nerve volley.
Short‐axon cells in the olfactory bulb: dendrodendritic synaptic interactions.
Authors: Getchell T V , Shepherd G M
Published: December 2014

1. In the rabbit olfactory bulb, analysis has been carried out of extracellular unitary responses in the glomerular layer to olfactory nerve volleys. 2. Units in the glomerular layer responded to single volleys with single, double, triple or longer repetitive spike discharges. The shortest initial latencies are consistent with monosynaptic excitation from the olfactory nerves; longer latencies may reflect longer nerve pathways or polysynaptic connexions in the glomerular layer. 3. Like mitral and tufted cells, some glomerular layer units gave evidence of activation by discrete nerve bundles. This correlates with recent anatomical evidence for projections of discrete olfactory nerve bundles to the glomeruli. 4. Facilitation of glomerular layer units took the form of lower spike thresholds and shorter latencies, when testing with paired olfactory nerve volleys of weak strength at relatively short intervals (less than 40 msec). Supression took the form of raised thresholds, longer latencies and briefer repetitive discharges; this was particularly evident with strong volleys at long testing intervals. 5. The early period of facilitation and later period of suppression did not correlate with the recovery cycle of the olfactory nerves; the nerves had an absolute refractory period of approximately 3 msec, relative refractory period of 15‐30 msec, and a small supernormal period of several hundred msec or more. 6. The evidence that the facilitation and suppression are mediated by dendrodendritic pathways through the periglomerular short‐axon cells is discussed in relation to recent electronmicroscopical studies. The results have implications for similar pathways through short‐axon cell dendrites in other parts of the nervous system.
Gradation of the reflex response from atrial receptors.
Authors: Kappagoda C T , Linden R J , Mary D A
Published: December 2014

1. In anaesthetized dogs, distension of balloons so as to stimulate atrial receptors resulted in a reflex increase in heart rate. 2. Successive distensions of one, two and three balloons positioned in the left upper and middle pulmonary vein‐atrial junctions and in the left atrial appendage resulted in a progressive increase in the magnitude of this response. 3. It is concluded that the magnitude of the increase in heart rate is related to the extent of receptor area stimulated.
Initial and delayed membrane currents in crab muscle fibre under voltage‐clamp conditions.
Authors: Mounier Y , Vassort G
Published: December 2014

Membrane currents are investigated under voltage‐clamp conditions in crab muscle fibre. 2. Step depolarizations elicit an initial composite current followed by a late outward current. 3. One of the components of the initial current is inward. It is sensitive to the external calcium concentration and inhibited by manganese ions, it can be carried also by strontium ions; thus it is expected to be a calcium current. 4. In TEA solution this calcium current appears alone, it reverses when the membrane polarization is carried beyond an internal potential of +30 or +35 mV. Such a low equilibrium potential for calcium ions can be explained either by a low selectivity of the calcium channel or by a local accumulation of calcium ions. 5. Calcium conductance shows voltage‐ and time dependence. 6. The late outward current corresponds to a potassium current and is inhibited by TEA ions. Its activation exhibits voltage‐ and time dependence. 7. The activation curve of the late potassium current is shifted in a depolarizing direction by addition of manganese ions. A similar shift produced by increasing [Ca]o or decreasing [Ca]i has been described on other preparations. It is then supposed that the electrical field of the membrane is modified by the gradient of double cations.
Mean and breath‐by‐breath pattern of breathing in man during steady‐state exercise.
Authors: Kay J D , Petersen E S , Vejby-Christensen H
Published: December 2014

1. The breathing pattern, that is the relation between tidal volume (VT) and the inspiratory (TI) and expiratory (TE) durations, has been studied for individual breaths (forty in each steady state). 2. Five healthy subjects were studied in steady‐state exercise on a bicycle ergometer breathing air; three of them were also studied in hypercapnia, at rest and during exercise, and two of them also during exercise on a treadmill. 3. Tidal volume and respiratory frequency both increased with work load. The increase in frequency was largely due to a progressive decrease in TE; TI also decreased. 4. At any constant level of respiratory drive (constant work load or chemical load) VT was positively correlated with both TI and TE in more than 95% of cases. 5. A simple model of the respiratory cycle which fits both the observed mean and breath‐by‐breath patterns and which involves no new assumptions is presented.
Characteristics of gastric inhibition by acidification of oxyntic gland area.
Authors: Konturek S J , Obtulowicz W , Tasler J
Published: December 2014

1. Gastric acid responses to the test meals were measured in the Heidenhain pouch, gastric and pancreatic fistula dogs, using the intragastric titration method, and monitoring the rate at which a solution of 1‐0 N‐NaOH had to be added to maintain the pH of the gastric content constant at pre‐selected values ranging from 5‐0 to 1‐0. In this way the pH profile of the gastric acid and pepsin responses to a liver extract meal kept in the Heidenhain pouch or gastric fistula as well as to exogenous stimuli such as histamine, pentagastrin or Urecholine could be determined. 2. A liver extract meal adjusted to pH 5‐0 produced a potent and pressure‐related stimulation of acid secretion from the Heidenhain pouch without any change in secretion from the main stomach and pancreas or in the serum concentration of immuno‐assayable gastrin. 3. Graded decrease of the liver extract meal pH to below 5‐0 resulted in the pH‐dependent inhibition of gastric acid output, which at pH 1‐0 was only about 30% of the value attained at pH 5‐0. Acid secretion from the Heidenhain pouch induced by exogenous stimuli such as histamine, pentagastrin or Urecholine also showed gradual decrease when the pH of the pouch content was decreased in sequential order from 5‐0 to 1‐0. This pH‐dependent inhibition was accompanied by an increase in pepsin secretion. 4. The pH‐dependent inhibition of the Heidenhain pouch response to the liver extract meal was not altered by topical application of a local anaesthetic and atropine or by the intravenous infusion of large doses of atropine, secretin or metiamide, which were shown to cause a marked inhibition of the main stomach response to the liver meal. 5. The results indicate that there is a local and gastrin‐independent inhibition mechanism of gastric acid secretion activated by an acidified meal making contact with the oxyntic gland area.
Secretory activity of goat mammary glands during pregnancy and the onset of lactation.
Authors: Fleet I R , Goode J A , Hamon M H , Laurie M S , Linzell J L , Peaker M
Published: December 2014

1. The volume of the udder and the composition of the secretion have been followed in five goats through pregnancy to the onset of lactation. 2. During the middle of pregnancy udder volume was minimal and there was little or no fluid in the teats. 3. Two stages of commencing secretory activity (lactogenesis) were defined. In the first, starting up to ten weeks pre‐partum, udder volume increased and the fluid in the teats changed from an extracellular‐fluid‐like to a milk‐like composition and acquired a high concentration of immunoglobulins. Four goats accumulated several litres of a pre‐colostral fluid with a high [lactose] 6‐7 weeks pre‐partum. 4. Comparison of the rate of increase in udder volume with previous data for the rate of increase in empty udder volume in pregnant goats showed that the rate of secretion, even in the last few days of pregnancy, was only a few per cent of the rate immediately after parturition. 5. In the last 2‐3 days of pregnancy there was a three to elevenfold increase in [citrate] in the secretion; this heralded the onset of copious secretion at about the time of parturition. 6. The changes in mammary gland activities are discussed in relation to changes in plasma hormone concentrations during pregnancy.
A correlation between the effects of anti‐mitotic drugs on microtubule assembly in vitro and the inhibition of axonal transport in noradrenergic neurones.
Authors: Banks P , Till R
Published: December 2014

1. Podophyllotoxin, colchicine and griseofulvin inhibit the intra‐axonal movement of noradrenaline storage vesicles in cat hypogastric nerve/inferior mesenteric ganglion preparations maintained in vitro, cause the disappearance of axonal microtubules and inhibit the assembly of microtubules from tubulin in vitro. The order of potency of the three effects is podophyllotoxin greater than colchicine greater than griseofulvin. 2. Lumicolchicine is without effect on the three parameters and does not interfere with the binding of tritiated colchicine to tubulin. 3. Podophyllotoxin causes a more rapid loss of microtubules from axons than the same concentration of colchicine. 4. The experiments provide strong evidence that microtubules are components of the system responsible for the intra‐axonal migration of noradrenaline storage vesicles.
Calcium and stimulus‐secretion coupling in the adrenal medulla: contrasting stimulating effects of the ionophores X‐537A and A23187 on catecholamine output.
Authors: Cochrane D E , Douglas W W , Mouri T , Nakazato Y
Published: December 2014

1. The ionophores X‐537A and A23187, which are known to transfer calcuim across cell membranes, stimulated catecholamine release from perfused cat adrenal glands. 2. These stimulant effects persisted in the presence of hexamethonium and atropine and are therefore attributable to direct actions of the ionophores on the adrenal chromaffin cells. 3. Perfusion with calcium‐free Locke abolished responses to A23187 and reduced those to X‐537A. 4. Responses to X‐537A were consistently large and comparable with those produced by 56 mM potassium. By contrast, responses to A23177, over the wide range of concentrations tested, were variable and much smaller. 5. That the two ionophores can stimulate through calcium‐dependent mechanisms is considered fresh support for the calcium hypothesis of stimulus‐secretion coupling. That they differ in effectiveness may mean that factors besides calcium are important. The greater potency of the less specific ionophore, X‐537A, may be attributable to its ability to depolarize as well as carry calcuim, while the relatively small effects of A23187, a generally more effective ionophore for calcuim, may indicate that inward movement of calcium without a background of membrane perturbation such as may be produced by depolarization, is insufficient to elicit strong secretory responses.
Effects of fasting and semistarvation on the kinetics of active and passive sugar absorption across the small intestine in vivo.
Authors: Debnam E S , Levin R J
Published: December 2014

The effects of dietary restriction on the kinetics of absorption in vivo of glucose, galactose and alpha‐methyl glucoside were assessed by electrical and chemical methods in the rat jejunum. 2. The 'apparent Km', maximum absorption or Vmax (mu‐mole/10 cm. 15 min) and maximum potential difference (p.d.max) were obtained for the jejunal electrogenic active transfer mechanism from the transfer p.d.s and the chemical absorption data corrected for diffusion using various graphical kinetic plots. 3. Fasting for 3 days greatly decreased the 'apparent Kms', obtained from electrical or chemical data, for all the sugars but had no effect on those for L‐valine or L‐methionine. Semistarvation caused a less pronounced reduction of the 'apparent Kms' for the sugars. The dietary‐induced change in 'apparent Km' for glucose was also observed in the fasted hamster. One interpretation of these changes is that the affinity of the carriers for sugars increases during dietary restriction; the greater the level of restriction the greater the increase. 4. Fasting and semistarvation caused large reductions in the Vmax. These reductions were correlated with a reduced enterocyte population estimated by changes in enterocyte column size. 5. The reduction in the Vmax for galactose was mainly accounted for by the decrease in enterocyte population. In the case of glucose, other factors such as reduced enterocyte metabolism or changes in the carriers must be involved to explain the discrepancy between the large decrease in Vmax and the enterocyte column size. 6. Fasting and semi‐starvation had complex, differential actions on the p.d.max for glucose, galactose and alpha‐methyl glucoside. These changes did not correlate with those observed in the Vmax measured chemically. 7. A standard diet obtained from two commercial sources was found to differ greatly in its effect on the electrogenic transfer system for alpha‐methyl glucoside but had no effect on those for galactose and glucose.
The influence of secretin on the secretion of pepsin in response to acid stimulants in the anaesthetized cat.
Authors: Braganza J M , Gibbs A C , Howat H T
Published: December 2014

Peptic secretion was studied in fasting anaesthetized cats in which the pylorus and common bile duct had been occluded to prevent the release of duodenal hormones which might stimulate or inhibit gastric secretion. Dilute acid was instilled into the stomach at intervals to aid recovery of gastric secretion and to preserve peptic activity. 2. Caerulein, histamine and N‐methyl histamine did not increase the output of pepsin when given on their own. Desulphated caerulein was a weak peptic stimulant. 3. Two C.H.R. u./kg per hour secretin initiated pancreatic secretion, the volume of which increased progressively as the dose was increased by stages to 32 C.H.R. u./kg per hour. 4. Four C.H.R. u./kg per hour secretin did not increase the output of pepsin. Peptic secretion was stimulated by 8 C.H.R. u./kg per hour. A maximal output of approximately 2000 u. pepsin/15 min was obtained when 16 C.H.R. u./kg per hour was infused. 5. When each acid stimulant was infused along with 4 C.H.R. u./kg per hour secretin the output of pepsin increased significantly. The peak output, which usually occurred between 15 and 30 min after stimulation, did not exceed 1000 u. pepsin/15 min. 6. The proposed explanation for the potentiation of the peptic response when an acid stimulant is infused along with a dose of secretin, in itself below the threshold of peptic stimulation, is that each acid stimulant increases gastric mucosal blood flow, approximately doubling the effective concentration of secretin delivered to the peptic cell.
A study of hypothalmic neurosecretory cells of bullfrogs in vitro.
Authors: Ishikawa T , Koiaumi K
Published: December 2014

Neurosecretory cells of preoptic nuclei of bullfrogs were studied in isolated hypothalamo‐hypophysial preparations under constant perfusion with oxygenated Ringer solution at 15‐17 degress C. Antidromic potentials were recorded following stimuli applied to the posterior lobe of the pituitary or the stalk. 2. Intracellularly and extracellularly recorded potentials resembled those obtained in vivo from neurosecretory cells of the mammalian hypothalamus. They were unique in that the antidromic potential had a long duration (10‐20 msec) and a distinct notch on the rising phase (between A and B spikes). The conduction velocity of the stalk fibres in vitro at this temperature was 0‐1‐‐0‐2 m/sec. 3. When two successive stimuli were given to the posterior lobe or to the stalk separated by intervals of between 30 and 65 msec, the test (second) response showed a longer delay of the B spike. This delay between the A and B components was as long as 10 msec. Further shortening of stimulus intervals produced block of B spikes in the test response. A complete separation of A and B spikes occur spontaneously in a few instances. 4. Evidence indicated that inhibitory recurrent axon collaterals play a role in the control of bullfrog neurosecretory cells. Antidromic potentials were inhibited by a 'conditioning' stimulus for as long as 300‐400 msec, even when the stimulus did not evoke an antidromic potential. 5. It was found that in addition to the inhibitory interaction there is a facilitatory recurrent axon collateral system which operates within the nuclei. The evidence for this is: (1) stimulation of the posterior lobe, with single subthreshold pulses evoked an action potential if preceded by another stimulus of subthreshold or just threshold intensity. The durations of such facilitatory effects were found to be 20‐‐400 msec; (2) a single pulse given to the posterior lobe did occasionally evoke two spikes from neurosecretory cells; the second spike which occurred 15‐30 msec after the first had the characteristics of a trans‐synaptically produced potential; (3) gradual changes in the intensity of stimuli applied to the neural lobe produced a sudden shift in latencies ranging between 15 and 30 msec. The potentials having long latency also showed characteristics of those transsynaptically excited. In addition, an increase in excitability of neurosecretory cells by antidromic stimulation was confirmed by using orthodromically induced action potentials in in vivo studies. Possible functional significance of inhibitory and excitatory recurrent collateral system in neurosecretory cells was discussed. 6. Two to threefold increase in NaCl concentration of a perfusate slightly increased the latency and refractory period of antidromic potential but not the shape of the potential. Norepinephrine added to a perfusate (1 mug/ml). augmented the separation of A and B spikes of the antidromic potential. Acetylcholine at a concentration of 1 mug/ml. did not have an appreciable effect on the antidromic potential.
Effects of angiotensin II on fluid transport, transmural potential difference and blood flow by rat jejunum in vivo.
Authors: Bolton J E , Munday K A , Parsons B J , York B G
Published: December 2014

A method has been described for the measurement of fluid transport by rat jejunum in vivo over two consecutive 30 min periods. 2. Subpressor infusion rates of angiotensin (0‐59 ng/kg per minute) stimulate fluid transport, while high (pressor) infusion rates (590 ng/kg per minute) inhibit fluid absorption. 3. Both the inhibitory and stimulatory effects of angiotensin on fluid transport are not accompanied by any change in the transmural p.d., total blood flow to the jejunum or distribution of blood flow within the wall of the jejunum. 4. These results are discussed in relation to the mechanism of action of angiotensin on fluid transport and its role in sodium and water homoeostasis.
Effects of divalent cations and of catecholamines on the late response of the superior cervical ganglion.
Authors: Chen S S
Published: December 2014

The characteristics of the late response of the superior cervical ganglion of dogs were studied by close‐arterial injection of catecholamines and divalent cations to the ganglion. 2. Dopamine, noradrenaline and adrenaline inhibit the late response as well as ganglionic activity induced by other means. The effect of dopamine is brief but that of adrenaline is prolonged. 3. Cd2+, Co2+, Ni2+, Zn2+, Hg2+ and Fe2+ markedly potentiate the late response, whereas Mn2+, Ca2+ and Mg2+ inhibit it. 4. may potentiate ganglionic activity triggered by other ganglionic stimulants. The Cd‐augmented activity may be blocked by a ganglion‐blocker which is specific to the stimulant. 5. CdCl2 may exhibit a direct ganglion‐stimulating action on a ganglion which shows prominent late responses and has been conditioned by tetanic preganglionic stimulation. 6. CdCl2 and MnCl2 may inhibit ganglionic transmission by suppressing acetylcholine release from presynaptic nerve terminals. 7. It is concluded that the late response represents the late discharges of ganglion cells, which are very sensitive to inhibition by CaCl2 and MnCl2 and may be potentiated by CdCl2.
Analysis of activity of muscle spindles of the jaw‐closing muscles during normal movements in the cat.
Authors: Cody F W , Harrison L M , Taylor A
Published: December 2014

Recordings have been made of afferent activity from spindles of the jaw‐closing muscles, together with jaw movement and e.m.g. from temporalis and masseter in conscious, unrestrained cats. 2. In the twenty‐nine units studied, the pattern of spindle behaviour observed during eating and lapping was generally what might be expected of stretch receptors. Maximal firing frequencies were found during opening of the mouth (lengthening), while during active closing the discharge was progressively reduced or abolished. Nevertheless, changes in the relation of stretch to firing frequency in different movements indicated that fusimotor drive was not constant. 3. spindle afferents could be divided into two groups on the basis of their maximal firing frequency during eating. "High‐frequency" units (range 240‐600 impulses/sec) showed pronounced velocity sensitivity, which supports the proposal that they correspond to spindle primaries. 'Low‐frequency" units (range 80‐200 impulses/sec) showed predominantly length sensitivity and probably correspond to secondary endings. 4. Length sensitivity of low‐frequency units was considerably greater in lapping movements than in eating, indicating increased static fusimotor drive in the former. Sensitivity in the opening phase of eating was indistinguishable from that recorded in deeply anaesthetized animals. 5. High‐frequency units were generally silenced immediately active shortening commenced. 6. No simple relationship existed between temporalis or masseter e.m.g. and spindle firing. 7. These results imply that normal masticatory movements are not initiated or driven to any appreciable extent via the fusimotor route. Close alpha‐gamma co‐activation is not a feature of this situation. On the other hand, in some other movements, such as licking the lips, fusimotor drive could fluctuate so as largely to cancel the unloading effects of active muscle shortening.
Interaction between the effects of spinal heating and cooling and of injections into a lateral cerebral ventricle of noradrenaline, 5‐hydroxytryptamine and carbachol on thermoregulation in sheep.
Authors: Bacon M , Bligh J
Published: December 2014

1. A study has been made of the interactions of the thermoregulatory effects of spinal cord heating and cooling and of the injections into the cerebral ventricle of noradrenaline, 5‐hydroxytryptamine (5‐HT) and carbamylcholine in sheep. 2. The interactions of spinal cord heating and the injections into the cerebral ventricle of noradrenaline, 5‐HT and carbamylcholine were very similar to those of hypothalamic heating or of high ambient temperature and the injections into the cerebral ventricle of these substances. These results are interpreted as evidence of the synaptic convergence of the pathways from peripheral, spinal cord and hypothalamic warm‐sensors at or before the points of action of these synaptically active substances. 3. The only definite thermoregulatory effect of spinal cooling was the onset of shivering which could be due to a purely spinal effect of cold. No substantial evidence was obtained of an interaction between spinal cooling and an injection of noradrenaline, 5‐HT or carbamylcholine into the cerebral ventricle. Thus there was no clear indication of centripetal pathways from spinal cold sensors converging with those from the skin and the hypothalamus for which evidence of convergence was obtained in an earlier study. 4. The results of this study are expressed in terms of the neuronal model of Bligh, Cottle & Maskrey (1971) and Maskrey & Bligh (1971), appropriately modified.
Charge movement and mechanical repriming in skeletal muscle.
Authors: Adrian R H , Chandler W K , Rakowski R F
Published: December 2014

1. Muscles were placed in a solution which depolarized the membrane to ‐30 to ‐20 mV so that mechanical activation was made refractory. Mechanical repriming and the recovery of voltage dependent charge movement were studied using a voltage clamp technique. 2. Mechanical repriming was investigated by determining the duration of a hyperpolarizing pulse required to elicit a just‐visible contraction for various post‐pulse potentials. As the post‐pulse potential was made more positive shorter repriming times were required to produce a threshold contraction. The relationship approached a minimum repriming time for very positive post‐pulse potentials. 3. These results suggest that hyperpolarization gradually removes some component of the activation mechanism from a refractory state and that the effectiveness of the amount which has recovered depends on the post‐pulse potential. A quantitative explanation is given using a simple model in which the essential component is assumed to be the charge movement process. 4. The rate of repriming contraction is voltage dependent; at ‐160 mV the rate is about twice that at ‐120 mV. Between 4 and 10 degrees C the rate has a Q10 of about 9. 5. Recovery of charge movement was studied using a repriming duration less than that required to produce a threshold contraction. The observed charge movement increased linearly with repriming time, consistent with the approximately linear initial segment of a slow exponential recovery process. Extrapolation of the recovery curve indicated that 2‐5 n/CmuF of charge is reprimed in the time necessary to reprime a threshold contraction. 6. The charge which recovers during a subthreshold repriming pulse is distributed according to membrane potential in the same way as a fully reprimed charge. 7. These results are consistent with the hypothesis that voltage dependent charge movement is an intermediate step in excitation‐contraction coupling. 8. The characteristics of a second type of charge movement are also described.
Pancreatic acinar cells: the role of calcium in stimulus‐secretion coupling.
Authors: Petersen O H , Ueda N
Published: December 2014

1. Segments of mouse or rat pancreas were placed in a flow cell through which physiological salt solutions of varying composition were pumped at a constant rate. Intracellular recordings of membrane potential, resistance and electrical time constant were made from the acini using fine glass micro‐electrodes. In some experiments two micro‐electrodes were inserted into two acinar cells within the same acinus to assess directly cell to cell coupling. The concentration of amylase in the effluent was measured continuously. 2. Electrical coupling between two acinar cells was observed when the tips of the two micro‐electrodes were less than 50 mum from each other. The coupling ratio was close to 1. Acetylcholine (ACh) always evoked depolarization of exactly the same amplitude in two coupled cells and reduced the amplitude of current‐pulse induced membrane potential changes in both cell simultaneously. 3. Stimulation with ACh caused an immediate increase in amylase output. Replacement of superfusion fluid Na by Tris or Cl by sulphate abolished ACh‐evoked increase in amylase release, but the subsequent reintroduction of Na or Cl caused an increase in amylase release of a magnitude similar to what was normally observed following stimulation. 4. Omitting Ca from the superfusion fluid and adding EGTA rapidly depolarized the acinar cell membrane, reduced the input resistance and caused a marked reduction in amylase secretion. During exposure to a Ca‐free, EGTA containing solution a marked increase in amylase release occurred following maximal ACh stimulation. 5. Addition of small amounts of Mg, Ca or Mn to a Ca‐, Mg‐free solution caused an increase in membrane potential, input resistance and electrical time constant and markedly increased amylase release. The effect on the electrical parameters was reversed in the absence of extracellular Na while extracellular Na was of no importance for the effect on amylase release. 6. The effect of ACh on amylase was enhanced during superfusion with a fluid containing 20 mM‐Ca. The presence of Mn (5 mM) in an otherwise normal control had no effect on ACh‐evoked release. 7. These results show that ACh acts on the acinus by reducing the surface cell membrane resistance. It is suggested that the ACh‐receptor interaction causes a release of Ca from the surface cell membrane and that the concentration of Ca in the surface cell membrane determines the specific membrane resistance particularly for Na. The release of Ca to the cytosol activates exocytosis while the Na influx is of importance for acinar fluid secretion. The effect of ACh on amylase secretion can be mimicked by agents displacing membrane‐bound Ca (Mg, Ca, Mn).
Effects of atropine, injected into a lateral cerebral ventricle of the rabbit, on fevers due to intravenous leucocyte pyrogen and hypothalamic and intraventricular injections of prostaglandin E1.
Authors: Cooper K E , Preston E , Veale W L
Published: December 2014

1. Cholinergic synapses in the hypothalamus may transmit information in those thermoregulatory pathways which function to raise body temperature. The effect of atropine, administered intracranially, on the febrile response to intravenous leucocyte pyrogen or intracranial prostaglandin E1 was therefore examined in conscious rabbits. 2. In rabbits exposed to a thermoneutral environment, micro‐injections of PGE1, into the anterior hypothalamus, intraventricular injections of PGE1, and intravenous injection so leucocyte pyrogen all caused fever accompanied by vasoconstriction in the ears and reduced respiratory rate. Intraventricular injection of 200 mug atropine during such fevers attenuated their development. This was due to the activation of heat loss mechanisms through vasodilatation in the ears and an increase in the frequency of respiration. This suggests a similarity in the pattern of neuronal activity evoked by PGE1 and leucocyte pyrogen, at least at the site(s) where atropine directly or indirectly exerted its effect and in the efferent pathways from this site. 3. In rabbits exposed to a cold environment, intraventricular injection of PGE1 caused fever through the activation of shivering accompanied by increased O2 consumption. Intraventricular injection of atropine during the development of fever caused an inhibition of shivering accompanied by increased O2 consumption. Intraventricular injection of atropine during the development of fever caused an inhibition of shievering and a decrease in O2 consumption so that temperature ceased to rise and returned to normal. 4. During fever, reversal by atropine of the increased heat conservation of rabbits in a neutral environment, and of their increased heat production in a cold environment adds further support to the concept that cholinergic synapses provide an important link in central temperature‐rasising pathways.
Isolation of rod and cone contributions to cat ganglion cells by a method of light exchange.
Authors: Rodieck R W , Rushton W A
Published: December 2014

1. The great majority of cat retinal ganglion cells are known to receive signals from rods and from a single (green) cone type. The centre region of the receptive fields of these cells was stimulated by a spot that changed back and forth from orange to white. By adjusting the intensity of the white spot relative to that of the orange a condition could be established at which the photon‐catch rate of the rods remained unchanged during the orange‐white exchange. At this intensity setting, termed the rod isolept, rods are thus unstimulated by the exchange, however intense, and the ganglion‐cell response was found to be due entirely to the green cones. At another intensity setting of the white spot relative to the orange (cone isolept), the photon catch of the green cones remained unchanged during the exchange and ganglion‐cell responses were found to arise entirely from the rods. 2. A neutral wedge in the combined exchange beam (but not in the steady background that covered the whole receptive field) regulated the size of the exchange stimulus and thus the magnitude of the ganglion‐cell discharge heard from a loud speaker to the exchange. Exchange threshold was the wedge setting at which this change in firing rate could only just be heard. 3. At the cone isolept, cones remain unstimulated however intense the exchange stimulus, and the rod increment threshold curve was determined over its full range from absolute threshold up to saturation. Likewise, at the rod isolept, the cone increment threshold curve was determined over the same intensity range as for the rods. Rod saturation was found to occur at the point where the cone increment threshold curve began to rise from its absolute threshold level toward its Weber region. 4. The exchange approach also enabled both rod and cone dark‐adaptation curves following a strong bleaching exposure to be obtained in the same experiment by moving successively between the cone and rod isolepts. At the cone isolept the time course of early rod dark adaptation could thus be determined when the rod threshold to flashing spots lay well above that of the cones.
The effect of zinc on the late displacement current in squid giant axons.
Authors: Meves H
Published: December 2014

1. Displacement currents produced by single depolarizing or hyperpolarizing voltage‐clamp pulses (Idepol and Ihyperpol) were recorded from intracellularly perfused squid giant axons treated with tetrodotoxin and tetraethylammonium chloride. The effect of internal Zn on the slow part of the displacement current was studied at different holding potentials. 2. Internal Zn in a concentration of 3‐3 mM markedly reduced the slow charge displacement associated with depolarizing and hyperpolarizing pulses. 3. At a holding potential more negative than ‐60 mV Idepol is normally larger than Ihyperpol if measured with pulses of equal height. The asymmetry Idepol greater than Ihyperpol (which possibly reflects the movement of gating charges) was abolished by Zn. 4. The reversed asymmetry Ihyperpol greater than Idepol which is normally seen at holding potentials less negative than ‐60 mV was not blocked by Zn. This suggests that the underlying mechanism is different from that of the asymmetry Idepol greater than Ihyperpol. 5. The Zn‐sensitive slow charge displacement during single depolarizing pulses was strongly reduced by lowering the holding potential from about ‐90 to about ‐30 mV. 6. The observations with single clamp pulses were confirmed by averaging and summing the currents associated with an equal number of depolarizing and hyperpolarizing pulses. 7. The effect of internal Zn on the charge displacement is thought to be due to a reaction with mobile charges in the membrane dielectric. Internal Zn in a concetration of 0‐5‐1 mM did not significantly shift the Na inactivation curve, indicating that it does not react with surface charges at the inner side of the membrane.
Analysis of pairs of individual Ia‐E.P.S.P.S in single motoneurones.
Authors: Mendell L M , Weiner R
Published: December 2014

1. Recordings of individual e.p.s.p.s evoked by the action of single medial gastrocnemius Ia fibres have been made from medial gastrocnemius motoneurones. In many motoneurones the action of two Ia fibres has been observed and the properties of the e.p.s.p.s compared. 2. For sixty‐three pairs of averaged e.p.s.p.s, each from the same motoneurone, the ratio of half‐widths was plotted against the ratio of rise times. These results were compared with theoretical values derived from the Rall compartmental model. It was found that variations in synaptic current time courses and differences in the termination of localized synaptic terminals were not sufficient to account for all the data. 3. Amplitude and rise time were inversely related but the correlation coefficient was very low. For pairs of e.p.s.p.s in the same motoneurone the e.p.s.p. with the fast rise time was larger than that with the slow rise time in forty‐eight of sixty‐three cases. 4. In a given motoneurone individual e.p.s.p.s evoked by the action of different Ia fibres did not vary greatly in amplitude. The ratio of peak amplitudes was less than 3 for 86% of the pairs of e.p.s.p.s examined, and the maximum was 4‐8. 5. Amplitude histograms were constructed for individual e.p.s.p.s at thirty‐three synapses. Twenty‐two of them could be shown to satisfy the Poisson law. The others satisfied the binomial law or neither. 6. Within a given motoneurone the amplitude of an e.p.s.p. is closely related to the mean number of quanta released but not to the amplitude of the unit e.p.s.p. produced by the action of a single quantum of transmitter.
The effect of caffeine and tetracaine on the time course of potassium contractures of single muscle fibres.
Authors: Caputo C
Published: December 2014

1. The time course of potassium contractures can be significantly prolonged by low concentrations of caffeine. 2. This effect of caffeine is not due to impairment of the fibre relaxing system. 3. Under conditions were contractile repriming is delayed (low temperature) an extra amount of activator can be released by caffeine, in addition to that released by potassium. 4. The source of this extra amount of activator is intracellular since its release can be shown in a O calcium EGTA medium. 5. Local anaesthetics, tetracaine, and to a lesser extent procaine, affect the release of contractile activator, without impairing the contractile machinery itself. 6. The results of the present paper support the view that the time course of potassium contracture is controlled by a membrane mechanism which is activated upon depolarization and later inactivates with time. 7. The effect of caffeine and local anaesthetics can be explained by assuming that the former prolongs the inactivation time course while the latter shortens it.