bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of anaesthesia on pentagastrin stimulated gastric acid secretion in the cat.
Authors: Albinus M , Blair E L , Hirst B H , Reed J D
Published: December 2014

1. The effect of Saffan (alphaxalone and alphadolone acetate) and Nembutal (pentobarbitone) anaesthesia on gastric acid secretion stimulated by I.V. bolus injections of pentagastrin was investigated in the gastric fistula cat. The effect of Saffan anaesthesia was also tested on I.V. near‐maximal and sub‐maximal infusions of pentagastrin. 2. Neither anaesthetic reduced the acid secreted in response to bolus injections of pentagastrin. Increased acid secretion with the anaesthetic was noted at some doses of pentagastrin in both intact and vagotomized animals. 3. Saffan anaesthesia had no effect on near‐maximal gastric acid secretion stimulated by pentagastrin 8 microgram kg‐1 hr‐1 but increased the response to pentagastrin 1 microgram kg‐1 hr‐1. 4. It is suggested that the differences in the acid secretory responses of the anaesthetized acutely prepared animal compared with the conscious animal are a consequence of the surgical procedures rather than the state of consciousness.
Stimulation of renin secretion and calcium efflux from the isolated perfused cat kidney by noradrenaline after prolonged calcium deprivation.
Authors: Harada E , Rubin R P
Published: December 2014

1. The effects of noradrenaline on the secretion of renin and on the efflux of Ca have been investigated in the isolated cat kidney perfused with Locke solution containing the alpha‐adrenergic blocking agent, phenoxybenzamine, to block increases in renal vascular resistance. 2. Noradrenaline elicited a marked increase in renin secretion in the absence of any discernible alterations in renal arterial pressure, and prolonged perfusion with Ca‐free Locke solution failed to depress noradrenaline‐evoked renin secretion. 3. Noradrenaline caused an increase in the efflux of 45Ca from prelabelled kidneys perfused with Ca‐free solution. Increasing the noradrenaline concentration produced graded increases in 45Ca efflux and renin release, and the peak rise in efflux preceded or coincided with peak renin secretion. 4. DL‐Propranolol inhibited the increase in 45Ca efflux and renin release resulting from noradrenaline stimulation. 5. Electrical stimulation of the renal nerve enhanced 45Ca efflux and renin release from prelabelled kidneys perfused with noraml Locke solution. 6. These findings provide further support for the view that the process of catecholamine‐induced renin secretion involves mobilization of Ca from a cellular site.
Effects of adrenoceptor stimulating and blocking agents on carotid body chemosensory inhibition
Authors: Llados F. , Zapata P.
Published: December 2014

1. The effects of α‐ and β‐adrenoceptor agonists and antagonists on chemosensory discharges originating from carotid bodies in situ were studied in anaesthetized cats.

2. Noradrenaline (NA) injections commonly resulted in increased frequency of carotid nerve chemosensory discharge, an effect ascribed to reduced blood flow through the glomus, and reduced or eliminated by α‐adrenergic block.

3. NA injections occasionally produced an initial reduction of chemosensory discharge frequency, which was however less intense and of shorter duration than that caused by dopamine. This effect of NA is not mediated by α‐adrenoceptors, since it is not blocked by dibenamine, but probably by low affinity for dopamine receptors.

4. Dopamine and apomorphine‐elicited chemosensory inhibition were not affected by low doses of phenoxybenzamine, which blocked NA‐evoked hypertensive reactions.

5. Higher doses of phenoxybenzamine and dibenamine produced a displacement to the right of dose—response curves for dopamine‐ and apormorphine‐elicited chemosensory inhibition. However, this interference by α‐adrenergic blockers was attributed to the resultant hypotension, since it was reversed upon restoration of blood pressure.

6. Isoprenaline, a β‐adrenergic agonist, did not induce chemosensory inhibition, whilst β‐adrenergic blockers (propranolol and dichloroisoproterenol) did not modify dopamine‐ and apomorphine‐elicited chemosensory inhibition.

7. These results provide further support for the hypothesis that chemosensory inhibition could be mediated by specific dopamine receptors, distinct from α‐ and β‐adrenoceptors.
Adaptive rundown of excitatory post‐synaptic potentials at synapses between hair cells and eight nerve fibres in the goldfish.
Authors: Furukawa T , Matsuura S
Published: December 2014

1. The excitatory post‐synaptic potentials (e.p.s.p.s.) evoked by sound stimuli were recorded intracellularly from large afferent eight nerve fibres in the sacculus of the goldfish (S1 fibres). The fish were anaesthetized with MS‐222 and spike potentials were suppressed with locally applied tetrodotoxin. 2. The e.p.s.p.s. successively evoked in response to each wound wave showed a marked rundown in size, while no reduction was observed in the microphonic potentials. The amplitude of successive e.p.s.p.s was reduced keeping approximately a fixed ratio to the preceding ones, suggesting that the rundown is attributable to a depletion of transmitter quanta from the release sites. 3. The rate of rundown of successive e.p.s.p.s, however, remained almost unchanged when the intensity of the stimulus sound was changed. It was also observed that, even after the e.p.s.p.s had been completely adapted to a continuous sound, a vigorous discharge of new e.p.s.p.s was observed when the intensity of the sound was increased. 4. These findings seem to indicate that it is the size of the readily available store and not the release fraction that is changed by a change in the sound intensity. 5. The saccular macula was superfused with solutions different in Ca and Mg ion concentrations. High Ca ion concentration brought about an increase in the size of the readily available store as well as the release fraction. 6. Mechanisms underlying these observations were discussed in terms of the quantal release mechanism as well as the morphology of the release sites.
Inhibition of baroreceptor and chemoreceptor reflexes on heart rate by afferents from the lungs.
Authors: Gandevia S C , McCloskey D I , Potter E K
Published: December 2014

1. Brief stimuli were delivered to the carotid baroreceptors or chemoreceptors in dogs anaesthetized with chloralose and paralysed with D‐turbocurarine. Baroreceptor stimulation was achieved by forceful retrograde injection of 2‐5 ml or air‐equilibrated saline into the external carotid artery after first clamping the common carotid artery. Chemoreceptor stimulation was achieved by rapid retrograde injections of 0.2‐0.5 ml of warmed CO2‐equilibrated saline into the external carotid artery. Observations were made during periods of temporary cessation of artificial ventilation. 2. When the volume of the lungs was not changing, prompt decreases in heart rate were evoked by chemoreceptor or baroreceptor stimuli except when these were delivered during the inspiratory phase of breathing (as judged from the records of phrenic nerve activity). 3. No changes in heart rate were evoked when these stimuli were timed to occur during expansion of the lungs in response to a rapid increase in intratracheal pressure (6‐10 mmHg in 1‐2 sec). Decreases in heart rate were evoked when the stimuli occurred during slower inflations of the lungs. 4. Both stimuli regained their effectiveness on heart rate with time after inflations of the lung when the lungs were held inflated. Both stimuli evoked large decreases in heart rate when delivered during deflations of the lung. 5. The effects of lung inflation on the effectiveness of both cardiodepressor reflexes were abolished by surgical denervation of the lungs.
Determination of dose‐response curves by quantitative ionophoresis at the frog neuromuscular junction.
Authors: Dreyer F , Peper K , Sterz R
Published: December 2014

1. Quantitative ionophoresis at the neuromuscular junction is possible when (a) the drug is released from appropriate distances (15‐‐20 micrometer for most drugs), (b) the topology of receptors is known and (c) high resistance drug pipettes (100‐‐200 M omega) are sued. 2. With this method, drug concentration‐endplate conductance relations were determined in voltage‐clamped end‐plates of the frog for the agonists ACh, carbamylcholine (CCh) and suberyldicholine (SubCh). 3. Based on the co‐operative and independent model, theoretical dose‐response curves were computed using as parameters the Hill coefficient nH, maximum conductance gmax., and apparent dissociation constant K. It was found that the co‐operative model fitted the data much better than the independent model. 4. Based on the co‐operative model, the mean maximum conductance for ACh was gmax. = 169 nS/micrometer, equivalent to 9000 ionic channels/micrometer length of a nerve terminal which can be opened at high drug concentrations. 5. The maximum conductance for CCh at‐‐80 mV membrane potential was, on the average, 78% of that for ACh measured at the same end‐plates. This value is termed the relative efficacy of CCh. 6. The mean values for the apparent dissociation constant K were 27.8 micrometer for ACh, 336 micrometer for CCh and 18 micrometer for SubCh. 7. The inhibition of the acetylcholinesterase activity by edrophonium (3‐‐10 micrometer) affected only the local ACh concentration at the receptor sites, but not gmax. and nH. 8. Dose‐response curves measured before and after removal of single nerve terminals in collagenase‐treated muscle fibres showed no change in the nH, gmax. and K. A slight increase in gmax. to a value of 218 nS/micrometer observed comparing collagenase‐treated and untreated end‐plate. 9. Desensitization of receptors may occur in the range of several tens of milli‐seconds.
The effect of duodenal infusion of milk, casein, lactose and fat on gastric emptying and acid secretion in the milk‐fed calf.
Authors: Bell F R , McLeay L M
Published: December 2014

1. The effect of infusion of the duodenum with milk, casein, lactose and fat on gastric acid secretion and abnormal emptying of a saline meal was studied in milk‐fed calves. 2. Compared with sodium bicarbonate, infusion with casein or lactose, alone or together, caused a small but statistically significant slowing of gastric emptying but did not effect gastric acid secretion. 3. Infection of the duodenum with cows' milk replacer or bovine milk fat slowed gastric emptying markedly and reduced gastric acid secretion significantly below levels obtained with sodium bicarbonate infusion. 4. The experiments provide evidence for the existence of mechanisms which prevent the passage of substantial amounts of whole milk into the duodenum before it has been subjected to gastric digestion.
Axonal transport of acetylcholine, choline acetyltransferase and cholinesterase in regenerating peripheral nerve.
Authors: O'Brien R A
Published: December 2014

1. The axonal transport of acetylcholine (ACh), choline acetyltransferase (ChAc) and cholinesterase (ChE) was estimated in the peroneal nerves of rabbits by measuring the accumulation of each against a nerve crush over a period of 20 hr. 2. Estimates were made of the amounts of these substances that were transported in nerves that had been regenerating for up to 111 days after being crushed or up to 13 days after being cut. 3. The initial response was the same whether the injury was a crush or a cut; the amount of ACh transported was increased, while ChAc and ChE transport was reduced. 4. The amounts of ACh, ChAc and ChE transported tended to return to normal levels when the nerves were allowed to reinnervate the denervated muscles. ChAc transport also showed an early recovery in the cut nerves. 5. The ACh content of the central nerve stump did not alter throughout regeneration but ChAc and ChE contents were reduced at the times when the transport of the enzymes was reduced. 6. These results are discussed in relation to the time course of nerve regeneration.
Role of membrane‐bound calcium in taste reception of the frog.
Authors: Kamo N , Kashiwagura T , Kobatake Y , Kurihara K
Published: December 2014

1. The frog gustatory responses to various salt stimuli and distilled water were greatly enhanced after the tongue was treated with an alkaline solution containing salts of low concentration. The incubation of the alkali‐treated tongue in solution of pH 6.0 containing Ca2+ restored reversibly the behaviour of the gustatory receptor to that before the treatment, while Mg2+ had no ability to do this. 2. The responses to salt stimuli and distilled water were greatly decreased after the tongue was incubated in solutions of pH 5.3 containing Ca2+. 3. On piece of tongue incubated in a solution of pH 5.3 containing 45Ca released a larger amount of 45Ca by the alkali treatment than another piece incubated in pH 7.0. It was concluded that removal of Ca2+ from the gustatory receptor membrane by the alkali treatment led to enhancement of the responses and binding of extra Ca2+ to the membrane by the incubation in acidic CaCl2 solution led to suppression of the responses. We emphasized that a conformational change of the receptor domains plays an important role in the transduction process of the gustatory response.
Latency‐relaxation in single muscle fibres.
Authors: Gilai A , Kirsch G E
Published: December 2014

1. Latency relaxation and twitch tension were recorded simultaneously in single isolated muscle fibres of Xenopus laevis. 2. During low frequency (0.6 or 1 pulse/sec) repetitive stimulation, three successive phases of twitch tension were observed: negative staricase (a slight drop in tension), positive staircase (about 15% increase in tension) and fatigue. At the same time the amplitude of latency relaxation decreased monotonically, and near the peak of positive staircase, the amplitude decreased almost to an undetectable level. 3. The application of caffeine (0.1‐‐1.5 mM) increased peak twitch tension by 15‐‐200%, but decreased the latency relaxation amplitude by 30‐‐93%. 4. The application of Ca‐release inhibitors, deuterium oxide and dantrolene sodium, caused a 43‐‐89% decline in peak twitch tension but no change in latency relaxation amplitude. 5. The lack of correlation between changes in peak twitch tension and latency relaxation amplitude suggests that latency relaxation is associated with the mechanism which triggers Ca2+ relase rather than with Ca2+ release itself.
An analysis of the cable properties of frog ventricular myocardium.
Authors: Chapman R A , Fry C H
Published: December 2014

1. The passive and active electrical parameters of frog ventricular myocardium have been measured. 2. The cytoplasmic resistivity has been determined by following changes in the resistance of a micro‐electrode on penetration of a cell. 3. Unidimensional cable analysis using direct and alternating currents revealed the presence of a single time constant attributed to the surface membrane. 4. Longitudinal impedance measurements indicate that a second time constant is present in the intracellular pathway. 5. The results indicate that the resistance between cells is low so that action potentials can propagate from cell to cell by local circuits. 6. A three‐dimensional cable analysis has also been carried out and compared to a simplified mathematical model which is presented in an Appendix and which closely approximates the experimental situation.
Histological analysis of cat muscle spindles following direct observation of the effects of stimulating dynamic and static motor axons.
Authors: Banks R W , Barker D , Bessou P , Pagès B , Stacey M J
Published: December 2014

1. Eleven cat tenuissimus spindles have been analysed mainly by cutting serial, transverse, 1 micrometer thick sections following direct observation of the effects of dynamic motor (gamma or beta) stimulation. 2. Histological results from these spindles were also used to interpret the effects of static fusimotor stimulation of other spindles. 3. Dynamic motor stimulation usually produced contractions seen as convergent movements of sarcomeres in single bag fibres, identified as bag1 fibres for reasons given in the text. 4. In one spindle a single dynamic axon produced a translational movement in one pole of a bag1 fibre and a convergent movement in each pole of a bag2 fibre, together with movements in other unidentified (presumably chain) fibres. Subsequent analysis showed that besides innervating both bag fibres the axon also supplied two chain fibres. 5. Contrary to expectation, motor endings on the bag1 fibres seldom occurred at the sites of convergent movement. Only two cases of coincidence occurred among sixteen foci and twenty‐one motor endings; otherwise focus and nearest ending were separated by distances of 0.85‐‐2.5 mm. 6. Most of the convergent movements of sarcomeres observed in bag1 fibres occurred in a region of the pole that is ultrastructurally distinct from the region where most of the motor endings were located. The possible relevance of this to the production of contractions in the bag1 fibre is discussed. 7. Convergent movement foci in bag2 fibres produced by the stimulation of static axons occurred largely within the same regions of the pole as the motor endings were located, though, whereas foci were observed in both intra‐ and extracapsular regions, most of the endings were intracapsular.
Carotid and cardiopulmonary baroreceptor control of splanchnic and forearm vascular resistance during venous pooling in man
Authors: Abboud Francois M. , Eckberg Dwain L. , Johannsen U. James , Mark Allyn L.
Published: December 2014

1. This study evaluated the contribution of carotid and cardiopulmonary baroreceptors to reflex splanchnic and forearm vascular adjustments during venous pooling in man. We compared (a) responses to lower body suction which produces venous pooling with (b) responses to lower body suction plus simultaneous application of neck suction. The rationale was that simultaneous application of neck suction, which stretches carotid baroreceptors, would minimize the contribution of carotid baroreceptors to circulatory adjustments produced by lower body suction.

2. Lower body suction at 40 mmHg decreased central venous pressure and arterial pulse pressure and increased forearm vascular resistance (plethysmography), splanchnic vascular resistance (indocyanine green dye clearance), and heart rate. Simultaneous application of neck suction prevented the tachycardia and most of the splanchnic vasoconstriction during lower body suction, but did not significantly attenuate the forearm vasoconstriction.

3. The major findings in this study are first, that the splanchnic vasoconstrictor response during venous pooling is mediated primarily through carotid baroreceptors, and secondly, that carotid and cardiopulmonary baroreceptors produce strikingly contrasting and non‐uniform regional vascular responses during venous pooling. Cardiopulmonary baroreceptors exert the predominant influence on forearm vascular resistance, but appear to have only a minor influence on splanchnic vascular resistance. Carotid baroreceptors produce most of the splanchnic vasoconstriction during venous pooling. but have a minor role in the forearm vasoconstriction.
Acute renal haemodynamic and renin‐angiotensin system responses to graded renal artery stenosis in the dog.
Authors: Anderson W P , Johnston C I , Korner P I
Published: December 2014

1. The acute renal haemodynamic and renin‐angiotensin system responses to graded renal artery stenosis were studied in chronically instrumented, unanaesthetized dogs. 2. Stenosis was induced over 30 sec by inflation of a cuff around the renal artery to lower distal pressure to 60, 40 or 20 mmHg, with stenosis maintained for 1 hr. This resulted in an immediate fall in renal vascular resistance, but over the next 5‐‐30 min both resistance and renal artery pressure were restored back towards prestenosis values. Only transient increases in systemic arterial blood pressure and plasma renin and angiotensin levels were seen with the two milder stenoses. Despite restoration of renal artery pressure, renal blood flow remained reduced at all grades of stenosis. 3. Pre‐treatment with angiotensin I converting enzyme inhibitor or sarosine1, isoleucone8 angiotensin II greatly attenuated or abolished the restoration of renal artery pressure and renal vascular resistance after stenosis, and plasma renin and angiotensin II levels remained high. Renal dilatation was indefinitely maintained, but the normal restoration of resistance and pressure could be simulated by infusing angiotensin II into the renal artery. 4. The effective resistance to blood flow by the stenosis did not remain constant but varied with changes in the renal vascular resistance.
Neural control of skeletal muscle cholinesterase: a study using organ‐cultured rat muscle.
Authors: Davey B , Younkin L H , Younkin S G
Published: December 2014

1. It has been proposed that the influence of innervation on the cholinesterase activity (ChE) of skeletal muscle and on end‐plate ChE in particular is mediated by trophic substance(s) moved by axonal transport and released from nerve. We have tested this hypothesis using rat extensor digitorum longus (e.d.l.) and diaphragm muscles denervated in vitro for several days and then maintained in organ culture to assay putative trophic substance(s). 2. The cholinesterase activity (ChE) of rat extensor digitorum longus (e.d.l.) muscles decreased dramatically after 5 days of denervation in vivo as previously reported. The ChE of rat e.d.l. muscles denervated in vivo for 3 days and then maintained in organ culture for 2 days was essentially identical to that of muscles denervated 5 days in vivo. 3. The ChE OF E.D.L. MUSCLES DENERVATED IN VIVO FOR 3 DAYS AND THEN MAINTAINED FOR 2 DAYS IN CULTURE MEDIUM SUPPLEMENTED WITH SCIATIC NERVE OR INNERVATED MUSCLE EXTRACT WAS SIGNIFICANTLY HIGHER THAN THAT OF MUSCLES DENERVATED IN VIVO FOR 5 DAYS OR DENERVATED IN VIVO FOR 3 DAYS AND THEN CULTURED FOR 2 DAYS IN CULTURE MEDIUM ALONE. Supplementing the culture medium with brain or spinal cord extract also significantly increased the ChE of organ‐cultured e.d.l. muscles. 4. Supplementing the culture medium with liver or spleen extract or with the extract of muscle denervated for 3‐‐7 days in vivo before extraction did not increase the ChE or organ‐cultured e.d.l. muscles. 5. The effect of muscle extract on the ChE of organ‐cultured e.d.l. muscles was dose dependent and occurred gradually reaching a maximum after approximately 24 h of culture. 6. Substance(s) which increased the ChE of organ‐cultured e.d.l. muscles were found to accumulate in transected sciatic nerve in the region just proximal to the site of transection where substances moved by axonal transport are known to accumulate. 7. Media conditioned with neurally stimulated e.d.l. or diaphragm muscles caused a substantial and highly significant increase in the ChE of e.d.l. or diaphragm muscles denervated in vivo and then maintained in organ culture. Media conditioned in the same way with unstimulated muscles did not increase the ChE OF ORGAN‐CULTURED MUSCLES. 8. The active substance(s) released by neural stimulation continued to be released when muscle contraction was blocked by adding D‐tubocurarine to the medium during conditioning but the release of these substance(s) was significantly reduced when magnesium (10mM) was added to the medium during conditioning. 9 The substance(s) released by neural stimulation selectively increased ChE in the end‐plate region. In diaphragm segments denervated in vivo and then maintained in medium conditioned with neurally stimulated muscle, there was a 102% increase in end‐plate ChE but no detectable increase in background ChE. 10...
Three‐micro‐electrode voltage clamp experiments in calf cardiac Purkinje fibres: is slow inward current adequately measured?
Authors: Kass R S , Siegelbaum S A , Tsien R W
Published: December 2014

1. The three‐micro‐electrode voltage clamp method (Adrian, Chandler & Hodgkin, 1970) was adapted for the study of regenerative inward currents in cardiac muscle. The adequacy of measurements of slow inward current in cardiac Purkinje fibres was assessed. 2. Membrane current density is reported simultaneously by total applied current (IT), along with a longitudinal voltage difference signal (delta V), recorded between two intracellular micro‐electrodes. 3. Non‐linear cable calculations show that delta V is a more faithful measure of membrane current density than IT as peak inward current increases. Quantitative agreement between delta V and IT only occurs when both signals report the membrane characteristics that would be obtained with an ideal longitudinal space clamp. 4. Agreement between delta V and IT is thus a useful criterion for satisfactory experimental measurements which we applied to the slow inward current. This component was elicited by depolarizing steps from a holding potential near =45 mV in the presence of tetrodotoxin. The IT signal was compared directly with delta V/R, where R is an effective longitudinal resistance that was experimentally determined. 5. delta V/R and IT showed very good agreement in both peak amplitude and time course at all potentials studied. 6. Radial non‐uniformity during the measured peak slow inward current was estimated by calculations assuming clefts 200 A wide with a uniform distribution of ionic channels. The calculated voltage span from surface to centre was always less than 5 mV, and the measured I‐V characteristics showed little distortion. 7. In another check, I‐V characteristics and slow response membrane action potentials were compared. The measured peak current showed good agreement with the product (total preparation capacitance) x (rate of rise). 8. The experimental and theoretical analysis suggest that the measurements of slow inward current are a good approximation to genuine membrane properties.
A quantitative description of membrane currents in rabbit myelinated nerve.
Authors: Chiu S Y , Ritchie J M , Rogart R B , Stagg D
Published: December 2014

1. Voltage‐clamp studies were carried out on single rabbit myelinated nerve fibres at 14 degrees C with the method of Dodge & Frankenhaeuser (1958). 2. A method was developed to allow the ionic currents through the modal membrane to be calibrated exactly under voltage‐clamp conditions by measuring the resistance of the internode through which the current was injected. 3. The ionic currents in a rabbit node of Ranvier can be resolved into two components, a sodium current and a leak current. Potassium current is almost entirely absent. 4. The sodium currents in rabbit nodes were fitted by the Hodgkin‐Huxley model using m2h kinetics. The kinetics of sodium currents in a rabbit node differ from that in a frog node under similar experimental conditions in two respects: (a) inactivation is faster, tau h for rabbit being 2‐3 times smaller around ‐50 mV; (b) the P(Na) (E) curve for mammal is shifted 10‐15 mV in the hyperpolarizing direction. 5. From the kinetics of sodium current, the non‐propagating rabbit action potential was reconstructed at 14 degrees C. The transient inward sodium current is responsible for the fast initial depolarization phase of the action potential, while the repolarizing phase is accounted for by leak alone. The computed shape of the action potential was in good agreement with the experimentally obtained action potential. 6. At 14 degrees C, frog and rabbit nodes with similar diameters have similar measured gNa values.
Adaptive hyperplasia and compensatory growth in the salt glands of ducks and geese.
Authors: Knight C H , Peaker M
Published: December 2014

1. The incorporation of [3H]thymidine into salt‐gland DNA has been studied in vivo and in vitro during adaptation of birds to salt water. 2. No increase in [3H]thymidine incorporation in vivo was apparent in birds on salt water for 0.25 and 1 day compared with those on fresh water. However, by 2 days there was a marked increase. At 7 and 14 days, incorporation was again low but by these later stages the DNA content of the glands was significantly increased. 3. Increased incorporation of [3H]thymidine was also evident in salt‐gland slices incubated in vitro from birds on salt water for 2 or 4 days, but not for 14 days, compared with those on fresh water. 4. It is concluded that hyperplasia, as well as the hypertrophy demonstrated previously, occurs as part of the over‐all adaptive response of the salt glands during the continual ingestion of salt water, but that the time course of the two processes is different. 5. In geese with one salt gland removed, no indication of compensatory growth of the remaining gland was evident in birds kept on fresh water for 24 days. In such birds on salt water for 14 days, some compensatory growth occurred but, as judged by measurements of DNA, RNA and protein, this could be ascribed to hypertrophy.
Metabolic, respiratory, vasomotor and body temperature responses to beta‐endorphin and morphine in rabbits.
Authors: Lin M T , Su C Y
Published: December 2014

1. The effects of beta‐endorphin and morphine on thermoregulatory responses of unanaesthetized rabbits to different ambient temperatures (Ta) of 2, 22 and 32 degrees C were assessed. 2. Intraventricular administration of either beta‐endorphin or morphine produced dose‐dependent hypothermia at 2 and 22 degrees C Ta. At 2 degrees C Ta the hypothermia was brought about solely by a decrease in metabolic heat production. At 22 degrees C Ta the hypothermia was due to a decrease in metabolism and an increase in peripheral blood flow. However, at 32 degrees C Ta, there were no changes in rectal temperature in response to either beta‐endorphin or morphine application. 3. Hypothermic effects of the administration of beta‐endorphin or morphine were greatly antagonized by pretreatment of animals with either an opiate antagonist naloxone or a serotonin depletor 5,6‐dihydroxytryptamine. 4. These findings indicate that the hypothermic responses to beta‐endorphin or morphine in rabbits may be mediated through central serotonergic mechanisms. The hypothermia was due to a decrease in heat production and/or an increase in heat loss.
Nephron electrolyte transport and sodium‐potassium adenosine triphosphatase activity: influence of nicotine in rat and rabbit.
Authors: Horster M , König T , Schmid H , Schmidt U
Published: December 2014

1. The influence upon mammalian renal epithelial transport of L‐nicotine was studied in different types of experiments. 2. The kidney in situ (rat), when infused with nicotine (1 mg hr‐1 kg‐1 I.V.), lowered its absolute and fractional K+‐absorption significantly and reversibly, but Na+‐absorption did not change. Effects on glomerular function and an irreversible effect upon epithelial Na+ and K+ absorption were prevailing at higher infused amounts (10 or 50 mg hr‐1 kg‐1). 3. Single dissected nephron segments (collecting tubule, rabbit) were perfused in vitro, and the Na+ and K+‐transtubular net flux was measured while L‐nicotine (50 ng/ml.) had been added to the contraluminal side of the epithelium. Both, Na+‐absorption and K+‐secretion were decreased reversibly. 4. The activity of the Na+‐K+‐activated ATPase was significantly decreased in the cortical collecting tubule and in the proximal convoluted tubule of the rabbit after incubation of single in vitro dissected nephron segments with L‐nicotine (50 or 100 ng/ml.). In contrast, nicotine added to a homogenate of renal cortical tissue had no effect on the Na+‐transport enzyme or on key enzymes of glycolysis and gluconeogenesis. 5. These observations on the kidney in situ and on defined, perfused and non‐perfused nephrons in vitro suggest that L‐nicotine has dose‐dependent, direct epithelial and mediated systemic effects on mammalian renal ion transport.
The packeted release of transmitter from the sympathetic nerves of the guinea‐pig vas deferens: an electrophysiological study.
Authors: Blakeley A G , Cunnane T C
Published: December 2014

1. Excitatory junction potentials (e.j.p.s) were recorded intracellularly in the guinea‐pig vas deferens following stimulation of the hypogastric nerve. Differentiation of the rising phase of the e.j.p. showed them to be made up of transient peaks in the rate of depolarisation, the ‘discrete events'. 2. In any one cell discrete events occurred at one or several latencies, intermittently, the frequency of occurrence varying between 1 in 1.8 to 1 in 45 stimuli. 3. Intermittence was not an artifact due to the use of submaximal stimulation nor the result of a ganglionic relay between the hypogastric and vas deferens nerve. 4. Discrete events occurring with a single latency had amplitudes that were multimodally distributed. In some cells the preferred values of amplitude were simple whole number multiples of the smallest preferred value. 5. The time course of discrete events varied from cell to cell and at different latencies. The discrete event had a time to peak of 5.3 +/‐ 1.9 msec, n = 220 (mean +/‐ S.D.) and a time to half decay of 8.3 +/‐ 3.6 msec, n = 220. 6. Discrete events in a cell could be matched for amplitude and time course by spontaneous excitatory junction potentials in the same cell and both probably represent the release of a single packet of transmitter. 7. The e.j.p. is made up of (1) discrete events which represent the release of transmitter from a single varicosity, (2) a non intermittent slow component which represents the electronic spread of activity from smooth muscle excited from distant release sites. 8. It is concluded that transmitter release from individual varicosities is packeted and the number of packets liberated per stimulus from a single varicosity is small, varying between zero and 10.
Measurement and significance of the reversal potential for the pace‐maker current (iK2) in sheep Purkinje fibres.
Authors: DiFrancesco D , Ohba M , Ojeda C
Published: December 2014

1. The apparent reversal potential (Erev) of the pace‐maker current (iK2) is found to depend on the experimental protocol used for its measurement. Evidence is presented showing that depolarizing (hyperpolarizing) pulses given before a test hyperpolarization used to determine Erev, shift Erev to more negative (positive) values. These shifts are opposite to those expected if the only effect of pre‐pulses were to change the concentration of potassium in extracellular clefts ([K]c) via accumulation and depletion processes. 2. This effect is shown to be due to the fact that Erev is dependent on s0, the degree of activation of iK2 at the start of the test hyperpolarization. 3. When a suitable protocol is used, depletion of cleft K can be demonstrated to take place during a large hyperpolarization. Changes in the level of [K]c induced by pre‐pulses must therefore also affect the Erev determination. 4. A simplified three‐compartment model has been used to investigate how K accumulation and depletion can affect the time course of iK2, with particular reference to the problem of Erev determination. Computed examples show that the model is able to reproduce the main features of the time course of iK2 recorded near its reversal potential and the changes induced by pre‐pulses on Erev measuremnet. By contrast, simulation on a linear cable model rules out the possibility that such results are due to voltage non‐uniformity. 5. The three‐compartment model predicts that the measured value of Erev differs from EK2 for two reasons: (1) when the recorded current trace is flat iK2 is still outward and decaying, and (2) the K equilibrium potential shifts to more negative values while the test hyperpolarization is applied. 6. The finding that Erev is directly affected by changes in s at the beginning of the test pulse is discussed in relation to the action of agents (such as Ca2+, H+, salicylate, adrenaline and ouabain) which are found to shift both the s00 curve and Erev.
A method for investigating the role of calcium in the shape change, aggregation and serotonin release of rat platelets.
Authors: Belville J S , Bennett W F , Lynch G
Published: December 2014

1. Effects of the platelet secretagogues thrombin and Concanavalin A (Con A) on shape change and release have been studied under conditions where external Ca2+ and ADP have been controlled. 2. In the absence of detectable aggregation both Con A‐ and thrombin‐induced release of serotonin are markedly dependent upon extracellular calcium. 3. Con A, unlike thrombin, does not produce aggregation in calcium‐supplemented medium. 4. The above property of Con A suggests that, in combination with added creatine phosphate and creatine phosphokinase, this ligand will be of value in the analysis of calcium‐dependent release in platelets.
Differential effects of diltiazem on glutamate potentials and excitatory junctional potentials at the crayfish neuromuscular junction.
Authors: Ishida M , Shinozaki H
Published: December 2014

1. The effects of diltiazem on glutamate potentials and excitatory junctional potentials (e.j.p.s) were investigated in the crayfish neuromuscular junction. 2. When diltiazem (0.3 mM) was added to the perfusion fluid, the ionophoretic glutamate potential was reduced to about half, whereas the peak amplitude of successive e.j.p.s elicited by a train of pulses of 100/sec increased by about 2 times. 3. It was suggested that diltiazem was a non‐competitive inhibitor of L‐glutamate. The reduction of the response to applied glutamate was not due to the acceleration of desensitization of the glutamate receptor. The rate of recovery from desensitization was delayzed by diltiazem. 4. The increase in amplitude of e.j.p.s caused by diltiazem was due to the increase in membrane resistance. The quantum content and size of extracellular e.j.p.s were not affected by diltiazem. 5. It was substantiated using the micro‐electrode technique that the glutamate sensitive area coincided with the neuromuscular junctional area. 6. The pharmacological difference between glutamate potentials and e.j.p.s revealed in the present study is difficult to explain on the glutamate transmitter hypothesis. One explanation worthy to be considered is that there are two pharmacologically different kinds of receptors sensitive to L‐glutamate.
The carotid sinus baroreceptor reflex in conscious rabbits.
Authors: Faris I B , Iannos J , Jamieson G G , Ludbrook J
Published: December 2014

1. A method is described for altering the pressure across the wall of the carotid sinus in conscious rabbits by enclosing the carotid bifurcation in a rigid, fluid‐filled capsule. The extracapsular arterial baroreceptors were denervated. 2. The baroreceptor‐‐heart rate reflex, elicited by injecting vasoactive drugs or inflating aortic and vena caval cuffs, was used to test the new method. The function of the carotid sinus was shown to be unaffected by enclosure in the capsule. Denervation of the extracapsular baroreceptors reduced the gain of the baroreceptor‐‐heart rate reflex two‐ to threefold. 3. The characteristics of the carotid baroreceptor reflex were studied in sixteen animals by the capsule method. Median estimates of maximum gain, and the range over which blood pressure changed, were 1.1 mmHg/mmHg and 57 mmHg respectively. There was good agreement between duplicate estimates made 1‐‐20 days apart. 4. There was only a weak association between the effects on blood pressure and heart rate of altering carotid sinus transmural pressure. Autonomic blockade of the heart, so that its rate was fixed, did not reduce the gain or range of blood pressure change.
Axonal conduction velocity changes following muscle tenotomy or deafferentation during development in the rat.
Authors: Russell N J
Published: December 2014

1. The conduction velocities of axons supplying the intertransverse caudal muscles of 8‐week‐old rats were measured. The distribution of conduction velocities was found to be similar to the more commonly studied hind‐limb innervation. 2. In animals in which the intertransverse caudal muscles had been tenotomized at birth, however, the conduction velocities attained by both the sensory and the motor nerves by 8 weeks of age were significantly reduced. 3. This effect is limited to growing animals since tenotomy of the intertransverse caudal muscles for the same period in adults had no effect on axonal conduction velocity. 4. Deafferentation of normal intertransverse caudal muscles during development also significantly reduced the conduction velocities attained by the motor innervation, to the same extent as tenotomy had done. 5. These results are discussed in relation to the role of impulse traffic in the development of neuronal dimensions.
Lifetime and conductance of acetylcholine‐activated channels in normal and denervated toad sartorius muscle.
Authors: Gage P W , Hamill O P
Published: December 2014

1. The average lifetime and conductance of acetylcholine‐activated channels were measured in normal and denervated, voltage‐clamped toad sartorius muscle fibres at 10 degrees C. 2. The null potential was ‐4 +/‐ 1 mV for subsynaptic channels in normal fibres and ‐6 +/‐ 3 mV for extrasynaptic channels in denervated fibres. 3. There was a linear relationship between variance of conductance fluctuations and mean conductance for acetylcholine‐induced currents up to 50 nA, in denervated fibres clamped at ‐50 mV. The ratio gave a channel conductance of 14 pS. 4. At the same membrane potential, the average lifetime of extrasynaptic channels in denervated fibres was approximately double, whereas channel conductance was approximately half, that of subsynaptic channels in normal fibres: there was little difference in net charge transfer through the two types of channel under similar conditions. 5. Single channel conductance increased, whereas average channel lifetime decreased, as the membrane potential became more positive (depolarized). The effect of potential on channel lifetime and conductance was more pronounced in denervated than in normal fibres.
Separate and combined effects of ouabain and extracellular potassium on renin secretion from rat renal cortical slices
Authors: Churchill Monique C. , Churchill Paul C.
Published: December 2014

1. Renin secretion of rat renal cortical slices was measured as a function of extracellular K and ouabain concentrations in the incubation medium.

2. A sigmoid relationship was found between renin secretion and log K concentration over the range 1·0‐4·0 m
M. Secretion was maximal at about 2·25 m
M‐K and half‐maximal at about 1·43 m
M‐K.

3. In media containing 4·0 m
M‐K, ouabain at 10−8, 10−7, and 10−6
M did not affect renin secretion. Higher concentrations of ouabain inhibited secretion. A sigmoid relationship was found between% inhibition of secretion and log ouabain concentration (10−6‐10−3
M). Inhibition was half‐maximal at 2·3 × 10−5
M and complete at 10−3
M‐ouabain.

4. Lowering extracellular K concentration from 4·0 to 2·25 m
M shifted the dose‐effect curve of ouabain to the left. At 2·25 m
M‐K, inhibition of renin secretion was half‐maximal at 10−5
M‐ouabain.

5. The inhibitory effect of 2 × 10−5
M‐ouabain (twice the dose for 50% inhibition) in media containing 2·25 m
M‐K was nearly identical to the combined effect of lowering K to 1·43 m
M (the concentration required for 50% inhibition) and adding 10−5
M‐ouabain. This observation suggests that ouabain and low extracellular K act at a common site, presumably on Na, K‐ATPase activity, to inhibit renin secretion.

6. Neither 10−3
M‐ouabain nor K‐free medium inhibited renin secretion when the concentration of free Ca in the medium was lowered to < 10−8
M. Therefore it is proposed that as a result of Na, K‐ATPase inhibition, (a) intracellular Na increases, (b) intracellular Ca increases via Na‐Ca exchange, provided that extracellular Ca exceeds 10−8
M, and that (c) Ca accumulation, in some unknown manner, inhibits renin secretion from rat renal cortical slices.
The mechanism of drinking induced by parenteral hyperoncotic solutions in the pigeon and in the rat
Authors: Kaufman Susan , Kaesermann Hans‐Peter , Peters Georges
Published: December 2014

1. In pigeons, the
I.V. injection of 0·3‐1·3 ml. of 50% (w/w) solutions of either polyethylene glycol (mol.wt. 20,000) or dextran (mol.wt. 40,000) induced reliable, rapid dose‐dependent drinking responses. The amount of water drunk in response to
I.V. polyethylene glycol was greater than that in response to
I.P. polyethylene glycol and twice that in response to
I.V. dextran.
I.V. polyethylene glycol induced a diuresis following the onset of drinking.

2. The dipsogenic effect of
I.P. polyethylene glycol solutions in the pigeon was depressed by
I.V. isotonic NaCl solution 1 hr before offering water but was increased by simultaneous
I.V. hyperoncotic polyethylene glycol solution.

3. In contrast, in rats, the subcutaneous injection of 25% (w/w) polyethylene glycol (mol.wt. 20,000; 1·25‐10·0 ml./kg body wt.) induced reliable drinking responses, while the same doses of polyethylene glycol, injected
I.V., did not induce drinking consistently. The volume of water drunk by rats in response to subcutaneous polyethylene glycol was smaller per unit dose than that drunk by
I.P. injected pigeons.

4. The results suggest that receptors for drinking induced by extracellular dehydration in the pigeon could be situated in the extravascular interstitial section of the extracellular compartment.
A possible mechanism of glycolytic impairment after adenosine triphosphate deplection in the perfused rat heart.
Authors: Grinwald P M , Hearse D J , Segal M B
Published: December 2014

1. When the heart is deprived of substrate and O2 for a long period, the ATP content falls to very low levels, with associated changes in ADP and AMP content, and a fall in intracellular pH. 2. These changes appear sufficient to block the hexokinase reaction, outweighing the normal mechanisms controlling this enzyme. Anaerobic glycolysis then remains blocked, even when glucose supply is restored. The block in anaerobic glycolysis can be overcome, however, by a brief period of oxidative metabolism, apparently because the improvement in adenine nucleotide levels serves to ‘re‐prime’ the system. 3. When the cell is severely depleted of ATP, the resulting impairment of glycolysis tends to reinforce the low ATP content, establishing a vicious cycle. Metabolic effects of this kind may cause irreversible loss of function, and may contribute to the mechanism of cell death.
Monocular activation of visual cortex in normal and monocularly deprived cats: an analysis of evoked potentials.
Authors: Mitzdorf U , Singer W
Published: December 2014

The unilaterally induced patterns of prominent excitatory post‐synaptic activity within Areas 17 and 18 were investigated in normal and monocularly deprived cats. They were elicited by electrical stimulation of the optic nerves and evaluated with the one‐dimensional current source‐density method. 1. In Area 18 of normal cats the unilaterally and bilaterally induced current source‐density patterns closely resemble each other. None of the mono‐, di‐ or tri‐synaptic activities is potentiated by binocular convergence. 2. In Area 18 of monocularly deprived cats the synaptic currents elicited by stimulating the nerve on the deprived side lead to approximately the same spatial and temporal distribution of sinks and sources as those induced from the normal eye; but the amplitudes are considerably smaller. This reduction is similar for mono‐, di‐ and trisynaptic responses which indicates (a) that the imbalance between activity from the deprived and non‐deprived eye is mainly due to reduced input to the cortical target cells from the deprived eye and (b) that the activity from the deprived eye still relayed to these cells is passed on to supra‐ and infragranular layers without diminution and in the same way as activity from the normal eye. 3. The imbalance of afferent activity from the deprived and non‐deprived eye is apparent in the evoked potentials recorded from the white matter. This indicates that activity from the deprived eye is already strongly reduced in the thalamo‐cortical fibres. 4. In monocularly deprived, but not in normal cats the monosynaptic activities from the two eyes are often segregated in depth within layer IV. 5. In Area 17 of both normal and deprived cats only a small fraction of the potential monosynaptic activity can be elicited by electrical stimulation of the optic nerves because of transmission failure in the lateral geniculate nucleus. Comparison of the current source‐density patterns elicited from the normal and deprived nerve in monocularly deprived cats indicates that activity produced by fast conducting afferents is more affected (reduced) by deprivation that that conveyed by slower afferents.