bluuebunny/crossref_metadata_2025 huggingface dataset:
Autoregulation of plasma flow in the isolated perfused rat kidney.
Authors: Bullivant M
Published: December 2014

1. Autoregulation of renal plasma flow, by which flow remains constant despite changes in perfusion pressure, was studied in the isolated, perfused kidney of the rat. 2. Autoregulation did not occur in preparations perfused with a protein‐free medium consisting of a balanced ionic solution resembling rat plasma in which 3% polyvinylpyrrolidone replaced the plasma proteins, changes in perfusion pressure over the normal autoregulatory range 100‐150 mmHg produced a corresponding and linear change in venous outflow and no consistent change in renal vascular resistance. 3. Addition of human serum (5%, v/v) to the medium restored autoregulation; changes in perfusion pressure in the range 100‐150 mmHg resulted in a stable plasma flow and a linear change in renal vascular resistance. The addition of bovine serum albumin (3 g/1.) to the protein‐free medium restored autoregulation to a similar degree. 4. In kidneys perfused with the protein‐free medium, the sensitivity of the renal vasculature to the vasoconstrictor drugs epinephrine and angiotensin II was only 1/40 the level seen in those kidneys perfused with media containing serum or albumin. 5. The experiments show that in the isolated, perfused kidney, autoregulation of plasma flow is not dependent on the presence of the globulin, angiotensinogen, in the perfusion medium; and suggest that failure of autoregulation in kidneys perfused with a protein‐free medium could be attributed to the rapid decline in the sensitivity of the vascular smooth muscle to constrictor stimuli.
The action of adrenaline on pace‐maker activity in cardiac Purkinje fibres.
Authors: Cohen I , Eisner D , Noble D
Published: December 2014

1. Adrenaline is known to shift the activation curve for iK2 (s infinite curve) in a positive direction on the voltage axis. This should cause an increase in the slope of diastolic depolarization, but cannot account for the experimentally observed increase in the maximum diastolic potential (MDP). 2. On application of adrenaline, in voltage clamp studies on short sheep cardiac Purkinje fibres there is a consistent 5‐15 mV negative shift of the reversal potential for the pace‐maker current, iK2. This shift is not reversed on application of the beta‐blockers sotalol or propranolol, or on washout for up to one hour. 3. A computer simulation, including this effect of adrenaline, shows that it can shift the maximum diastolic potential in the hyperpolarizing or depolarizing direction depending on the initial value of [K+]o. In both cases it will add to the increase in rate caused by the positive shift of the activation curve for iK2 (the s infinite shift). 4. Studies of the effects of adrenaline on the MDP and rate in long sheep Purkinje fibres show a slower reversibility of the MDP than the rate, consistent with a slower reversal of the shift in the iK2 reversal potential than the shift in s infinite. 5. Possible mechanisms of the shift in reversal potential are discussed with respect to K+ balance in the intercellular clefts of the Purkinje fibre, including a a stimulation of the Na+‐ K+ pump. The possible sources of voltage clamp artifact are also discussed.
On the transmission of the stimulating effects of carbon dioxide to the muscles of respiration.
Authors: Bainton C R , Kirkwood P A , Sears T A
Published: December 2014

1. Electromyography was used to measure the response of the diaphragm and intercostal muscles to CO2 in artificially ventilated decerebrate cats. 2. Hypocapnia produced tonic activity in either inspiratory or expiratory muscles or both, according to the preparation. 3. A graded effect of CO2 on both rhythmic and tonic activity was observed and for the latter this could be seen at as low as 10 torr PA,CO2. 4. In one human subject tonic firing of expiratory motoneurones was also induced by hypocapnia and this activity showed a graded increase with increasing (CO2. 5. A saggital incision of the medulla aimed at interrupting inspiratory bulbospinal axons abolished activity in inspiratory muscles and at eupnoeic levels of CO2 converted the activity of expiratory muscles from a periodic to a topic firing pattern. 6. Following such lesions the threshold for rhythmic excitation of expiratory muscles was elevated and this revealed that the graded effect of CO2 on tonic expiratory activity extends to as high as 60 torr. 7. The tonic activation of respiratory muscles in response to CO2 ceased after cervical cord transection or when the saggital incision in the medulla was extended caudally to the first cervical segment. 8. It is concluded that the CO2 dependent activation of spinal respiratory motoneurones is conveyed by bulbospinal axons which decussate in the vicinity of the obex and that this activation can be rhythmic or tonic. 9. It is suggested that the rhythmic excitation of expiratory muscles derives from a periodic inhibition of expiratory bulbospinal neurones which are subjected to a tonic CO2 dependent excitation which is continuously variable over the physiological range.
The metabolism of [14C]histamine during pentagastrin‐stimulated acid secretion in the cat.
Authors: Bunce K T , Lake H J
Published: December 2014

1. The metabolism of exogenous [14C]histamine has been examined in cats during gastric secretion. The appearance of 14C‐labelled metabolites has been measured chromatographically in urine and gastric juice under non‐secreting and pentagastrin‐stimulated conditions, and in gastric mucosa after pentagastrin stimulation. 2. The main metabolites detected were (i) an acidic product, presumed to be methylimidazoleacetic acid, (ii) Ntau‐methylhistamine, and (iii) an unidentified metabolite, moving rapidly in the chromatographic systems used, and designated 'preacetylhistamine'. No evidence was found for the presence of side chain (i.e. Nalpha)‐methylated histamines, either in the non‐stimulated or pentagastric‐stimulated state. 3. During a 3 hr non‐stimulated period, followed by 3 hr of pentagastrin administration, the relative proportions of 14C‐labelled metabolites excreted in urine remained unchanged. During acid secretion there was an increase in the proportion of 'pre‐acetylhistamine' in gastric juice, which occurred at the expense of the acidic metabolites. It is suggested however that this effect is more likely to be the result of a slow adaptation to the administration of exogenous [14C]histamine than the result of acid secretion. 4. The results of the present work do not appear to support the hypothesis of Code (1970), that a local control mechanism for acid secretion might involve the formation Nalpha‐methylated histamine metabolites in gastric mucosa.
A study of the routes by which protein passes from the pericardial cavity to the blood in rabbits.
Authors: Gibson A T , Segal M B
Published: December 2014

The routes by which radioiodinated serum albumin placed in the pericardial cavity gains access to the circulation have been investigated in rabbits. 1. Eighty per cent of pericardial cavity protein passes through the parietal pericardium and into the circulation through the thoracic duct. 2. A small amount of protein is drained through the right lymph duct; this is probably derived from protein passing from the pericardial cavity into the pleural cavity. 3. There is no apparent movement of protein directly into blood vessels of the parietal pericardium. For theoretical reasons movement of protein across the visceral pericardium and into the blood vessels of the myocardium is also unlikely. 4. A small amount of protein enters the circulation when both major lymphatics are ligated. It is proposed that lymphatic uptake may continue and secondary lymphovenous junctions will open as a result of raised intralymphatic pressure.
The influx of amino acids into the heart of the rat.
Authors: Baños G , Daniel P M , Moorhouse S R , Pratt O E , Wilson P A
Published: December 2014

1. The influx of nineteen amino acids into the heart of the living rat was studied by a method specially devised for experiments under controlled conditions in vivo. 2. When, in separate experiments, the concentration of each amino acid in turn was artificially raised in the circulation, the influx of that amino acid into the heart increased. 3. Our data indicate that at least ten of these amino acids enter the heart in vivo by means of saturable carrier‐mediated transport systems. The transport rates conform, at least approximately, to Michaelis kinetics and the transport systems are clearly, in the cases of many amino acids, active, i.e. energy‐dependent. 4. The amino acids which were studied had rates of influx into the heart which differed from each other over a range of more than 10 to 1, even when allowances were made for the difference in their concentration in the circulating blood. These differences in influx were not related to such factors as the molecular size of the individual amino acids. 5. The amino acids which have a high influx into the heart are mainly those which are needed either to re‐synthesize contractile protein or as oxidizable substrates.
A bilateral antidiuresis to renal artery infusion of prostaglandin E1 in dogs treated with phenylbutazone
Authors: Hall W. J. , Hensey O. J. , O'Neill P. , Sheehan J. D.
Published: December 2014

1. In acute experiments, high levels of endogenous prostaglandins, provoked by operative stress, could obscure or alter the actions of infused prostaglandins on the kidney. For this reason we decided to compare the effects of infusing prostaglandin E1 into the renal artery of the dog before and after the administration of phenylbutazone, a prostaglandin synthetase inhibitor.

2. Infusion of prostaglandin E1 into the left renal artery of the pre‐phenylbutazone treated dog undergoing a mannitol diuresis increased renal plasma flow, glomerular filtration rate and the excretion of salt and water. The findings are in general agreement with those reported by others.

3. Following phenylbutazone administration the vascular and saluretic actions of prostaglandin E1 were unchanged but a reduced diuretic effect was observed. The response to a low dose of prostaglandin E1 (0·05 μg/min) was reduced from 1·46 ± 0·15 to 0·96 ± 0·16 ml./min (P < 0·001) and the response to a high dose (0·5 μg/min) from 1·82 ± 0·19 to 0·99 ± 0·31 ml./min (P < 0·002).

4. A significantly less dilute urine was excreted during prostaglandin infusion in the dog after phenylbutazone treatment than before. The reduction in the diuretic response was of the same order as the decrease in the free water clearance response, while the increase in osmolar clearance was unchanged.

5. In water‐loaded dogs treated with phenylbutazone, infusion of prostaglandin E1 into the left renal artery had a biphasic effect on urine output from the left kidney. An initial diuretic response to a low dose of prostaglandin E1 disappeared with the infusion of higher doses, and antidiuresis developed in the immediate post‐infusion period.

6. As prostaglandin was infused into the left kidney progressive antidiuresis was seen in the non‐infused right kidney.

7. It is concluded that endogenous prostaglandins do not obscure or alter the vascular and saluretic actions of intrarenal prostaglandin E1. The findings question the proposed link between the vascular and saluretic actions of this compound.

8. It is suggested that the reduced diuretic effect of prostaglandin E1 in series no. 1, and the antidiuresis in the water‐loaded dogs, are caused by the release of endogenous ADH. It is further suggested that phenylbutazone unmasks this release by removing the endogenous prostaglandins. If these deductions are correct, the findings support the anti‐ADH role assigned to endogenous prostaglandins by Anderson, Berl, McDonald & Schrier (1975).
Specificity of initial synaptic contacts made on guinea‐pig superior cervical ganglion cells during regeneration of the cervical sympathetic trunk.
Authors: Njå A , Purves D
Published: December 2014

1. Largely appropriate synaptic connexions are formed with neurones in the superior cervical ganglion at long intervals after interruption of the preganglionic nerve. In the present study we have assessed the accuracy of connexions during the early stages of re‐innervation by observing end‐organ responses to ventral root stimulation in vivo, and by recording intracellularly from ganglion cells during ventral root stimulation in isolated preparations. 2. Appropriate, but weak, end‐organ responses were elicited by stimulation of the first and fourth thoracic ventral roots (T1 and T4) 15‐‐30 days after freezing the cervical sympathetic trunk. 3. Intracellular recordings from ganglion cells during stimulation of the ventral roots C8‐‐T7 in vitro showed that synaptic contacts are first re‐established 8‐‐11 days after freezing the preganglionic nerve. The proportion of re‐innervated cells, and the strength of innervation of individual neurones, increased rapidly for up to about 3 months after nerve injury, but showed little change thereafter. Innervation remained weaker than normal even after 6 months. 4. Patterns of segmental innervation recorded intracellularly during the early stages of regeneration were similar to, but more restricted than normal. Even 13‐‐19 days after interruption of the preganglionic nerve, neurones re‐innervated by more than one spinal cord segment tended to be innervated by a contiguous subset of the spinal segments which contribute innervation to the ganglion. The incidence of neurones receiving innervation from a discontinuous segmental subset was about the same at early and late stages or re‐innervation. 5. Throughout the course of nerve regeneration, re‐innervated neurones tended to receive dominant synaptic input from axons arising at a particular spinal level, as do normal cells, with adjacent segments contributing a synaptic influence that diminished as a function of distance from the dominant segment. 6. The results of these experiments argue against the initial formation of imprecise connexions with subsequent retention of appropriate contacts and a loss of inappropriate ones. Rather our findings suggest that the re‐innervation of ganglion cells proceeds by a gradual accumulation of synaptic connexions which are, from the outset, appropriate.
Influences of cones upon chromatic‐ and luminosity‐type horizontal cells in pikeperch retinas.
Authors: Burkhardt D A , Hassin G
Published: December 2014

1. The spectral sensitivity and spatial organization of cones and horizontal cells have been analysed by intracellular recording in pikeperch retinas. 2. The vast majority of cone recordings were obtained from orange‐sensitive cones. They have an action spectrum which peaks at about 605 nm. Recordings from several green‐sensitive cones have also been obtained. 3. The results of action spectrum measurements and spectral screening tests indicate that the vast majority of luminosity‐type horizontal cells receive predominant input from the orange‐sensitive cones. 4. Chromatic‐type horizontal cells were recorded at more proximal levels of the retina than luminosity‐type cells and were the classic red‐depolarizing, green hyperpolarizing (R/G) type. 5. The action spectra of the depolarizing and hyperpolarizing responses of chromatic horizontal cells peak at about 650 and 530 nm, respectively. When the depolarizing mechanism is selectively depressed by a red background field, the action spectrum of the hyperpolarizing mechanism shows an enhanced sensitivity, peaks at 530‐‐540 nm, and may approximate the action spectrum of the green‐sensitive cones. 6. Small red fields evoke depolarizing responses from chromatic‐type horizontal cells but do not seem to significantly activate the depolarizing surround mechanism of cones. 7. These and other results suggest that the colour‐opponent properties of the chromatic‐type horizontal cells are not fundamentally dependent upon feed‐back to cones but rather originate from antagonistic interactions generated in post‐receptor networks.
Modulation of transmission at an inhibitory synapse in the central nervous system of the leech.
Authors: Nicholls J , Wallace B G
Published: December 2014

The synaptic interactions among a group of cells in the leech C.N.S. that regulate the animal's heartbeat exhibit several remarkable features (Thompson & Stent, 1976 a, b, c). We have examined in detail the properties of the inhibitory synapse between two of these cells, the heart interneurone (HN cell) and the heart excitor motoneurone (HE cell). 1. Impulses in the presynaptic HN cell gave rise to monosynaptic i.p.s.p.s in the HE cell that were blocked by high concentrations of Mg and were reversed when the membrane potential of the post‐synaptic motoneurone was hyperpolarized beyond‐‐75 m V or when Cl was injected into the cell body. These i.p.s.p.s were chemically mediated, and involved an increase in chloride conductance. 2. In contrast to chemical synapses between sensory and motor cells in the leech C.N.S., little facilitation or depression of transmission occurred when the HN cell was stimulated at frequencies of 0.1‐‐50 Hz. 3. Steady subthreshold depolarization of the presynaptic HN interneurone evoked a maintained hyperpolarization of the post‐synaptic HE cell, indicating that currents injected into the HN cell body could spread to the terminals and cause continuous release of transmitter. 4. The size of the i.p.s.p. evoked in the HE motoneurone by an action potential in the HN interneurone varied with the resting membrane potential of the presynaptic cell. An impulse superimposed on a prolonged, subthreshold, depolarizing pulse produced a larger i.p.s.p.; conversely, prolonged hyperpolarization of the HN interneurone reduced the i.p.s.p. amplitude recorded in the HE cell. This effect was most obvious when the natural, rhythmical bursts of activity in the HN interneurone were interrupted by bathing the preparation in leech Ringer fluid containing elevated concentrations of Mg. Under these conditions a 10 mV depolarization of the HN cell increased the size of the i.p.s.p. in the HE cell approximately sixfold. Significant changes in i.p.s.p. amplitude occurred without any noticeable change in the amplitude and duration of the presynaptic action potential. With large presynaptic depolarizations, which produced the biggest i.p.s.p.s, there was some reduction in the amplitude and increase in the duration of the action potential. 5. Following a step depolarization of the presynaptic cell, the size of successive i.p.s.p.s increased with a time constant of about 1 sec. Upon repolarization the i.p.s.p.s decreased in amplitude to the original level. 6. stimulation of one HN cell also gives rise to an i.p.s.p. in its contralateral homologue (Thompson & Stent, 1976c). Trains of i.p.s.p.s produced in this way hyperpolarized at HN cell to such an extent that the size of the synaptic potential it evoked in an HE cell was reduced. 7. Thus, an HN interneurone inhibitis transmission between the contralateral HN and HE cells presynapitcally in addition to inhibiting directly the ipsilateral HE motoneurone.
Effect of luminal pH on acid secretion from Heidenhain pouches evoked by topical and parenteral stimulants
Authors: Carter David C. , Grossman Morton I.
Published: December 2014

1. An apparatus for intragastric titration has been devised and its validity tested. Both when attached to a beaker simulating a pouch and when attached to a pouch whose secretion was suppressed by infusing cimetidine, the apparatus accurately measured added acid when the endpoint setting was between pH 3·0 and 9·0. At pH 2·0 and 1·0 with liver extract and at pH 1·0 with saline, the amount of acid added was markedly underestimated.

2. In dogs with vagally denervated pouches, during stimulation by
I.V. infusion of histamine or pentagastrin, the rate of acid secretion as measured by intrapouch titration was uninfluenced by changes in luminal pH between 2·0 and 9·0. The apparent decrease in acid secretion at pH 1·0 could be shown to be due entirely to artifact in that no change in acid secretion was found when the gain in mass of acid was simultaneously measured by using a non‐absorbable dilution indicator to measure volume gain and titration of samples to pH 7·0 to measure acid concentration.

3. During stimulation of acid secretion by solutions of liver extract or of
L‐histidine instilled into the pouch, the rate of acid secretion was found to increase markedly as pH was increased from 3·0 to 9·0 thus confirming our earlier findings.

4. We conclude that while stimulation of acid secretion by topical stimulants is highly dependent on luminal pH, secretion increasing as pH increases, stimulation by parenteral agents such as histamine and pentagastrin is not influenced by luminal pH in the range from pH 1·0 to 9·0.
An analysis of the dose‐response relationship at voltage‐clamped frog neuromuscular junctions.
Authors: Dionne V E , Steinbach J H , Stevens C F
Published: December 2014

1. Frog neuromuscular junctions were viewed with Nomarski optics and voltage clamped. Agonist was applied ionophoretically and agonist concentrations were measured using a micro‐electrode sensitive to quaternary amines. 2. The dose‐response relationship was studied using the agonists carbamylcholine, suberyldicholine and hydroxyphenyl‐propyltrimethylammonium. 3. With all of these agonists, it appeared that the ACh receptor could be active when either one or two agonist binding sites were occupied. The receptor was much more likely to be active when both sites were occupied. Agonist dissociation constants and receptor activation probabilities were estimated by non‐linear regression techniques for several possible receptor activation schemes.
The generation of resting membrane potentials in an inner ear hair cell system.
Authors: Bracho H , Budelli R
Published: December 2014

1. The macula sacculi in the mudpuppy is an inner ear sensory area accessible for intracellular recordings in vitro and in vivo. 2. The resting potentials recorded in vitro can be explained by the electrodiffusion theory assuming a uniform ionic selective in the membranes of the neuroepithelial cells. 3. The resting potentials recorded in vivo are significantly larger than predicted by the electrodiffusion theory, probably because of an electrogenic metabolic process present in the neuroepithelial cells. 4. An equivalent circuit is proposed to explain the resting electrogenesis in the neuroepithelial cells present in the sensory area.
Respiratory oscillations in discharge frequency of chemoreceptor afferents in sinus nerve and anaesthetized cats at normal and low arterial oxygen tensions.
Authors: Band D M , Wolff C B
Published: December 2014

1. The discharge of chemoreceptor afferents in preparations of the sinus nerve in spontaneously breathing anaesthetized cats has been subjected to an averaging procedure in records obtained when the animals breathed (a) air and (b) a hypoxic gas mixture. 2. The mean discharge frequency was higher in hypoxia than at normal oxygen tension. 3. Oscillations in chemoreceptor discharge frequency with the same period as respiration were obtained by the averaging procedure both at normal arterial oxygen tensions and in hypoxia, but there was no significant increase in oscillation amplitude with hypoxia. 4. The carotid body response to arterial PCO2 oscillations does not therefore appear to be amplified by hypoxia. This finding is discussed in relation to the reported dependence upon hypoxia of the ventilatory effects of tube breathing in man.
Glutamate current noise: post‐synaptic channel kinetics investigated under voltage clamp.
Authors: Anderson C R , Cull-Candy S G , Miledi R
Published: December 2014

1. Analysis of voltage‐clamped noise has been used to investigate the operation of glutamate receptors and associated channels at the locust nerve‐muscle junction. Channels opened by glutamate and an agonist have been compared. 2. Glutamate‐induced current fluctuations have a power spectrum with a single (1/frequency2) component which fits a simple model for the operation of channels. The form of the spectra for glutamate voltage noise and for ‘background’ noise has been determined. 3. The single channel conductance was estimated from the spectra, gamma glutamate = 122 +/‐ 0.4 (S.E.) pS. This estimate is independent of membrane potential and of the amplitude of membrane current change produced by glutamate. 4. The rate constant, alpha, for the closing of glutamate‐operated channels depends exponentially on membrane potential, conforming to the equation alpha = approximately alphaeetaVm (approximately alpha = 0.26 +/‐ 0.014 msec‐1, eta = 0.0054 +/‐ 0.001 msec‐1); the duration of the channel lifetime (tau) decreases with hyperpolarization. Membrane potential dependence of alpha reduces as temperature is lowered. 5. For glutamate‐operated channels, the temperature dependence of alpha and gamma fits the Arrhenius equation; alpha and gamma decrease exponentially as a function of T‐1 (degrees K) with a descrete change in slope at about 6 degrees C, indicating a change in the activaiton energies of the respective rate processes. 6. Spectra of quisqualate‐induced current fluctuations have the same form as spectra for glutamate noise. The single channel conductance was estimated from the spectra, gamma quisqualate = 120 +/‐ 3.9 (S.E.) pS. 7. The rate constnt, alpha, for the closing of quisqualate‐induced channels depends exponentially on membrane potential. The duration of the open state for quisqualate channels was 2.2 times longer than for glutamate channels. 8. For glutamate receptors the voltage‐sensitivity of the channel life‐time is in the opposite direction to that of ACh receptors in vertebrate muscle. Possible explanations for the sharp change in the activation energy of the rate processes associated with the channel are discussed.
The tract of Lissauer and the dorsal root potential.
Authors: Cervero F , Iggo A , Molony V
Published: December 2014

1. Intersegmental dorsal root potentials (d.r.p.s) have been recorded in the lumbar spinal cord of spinalized cats under Na pentobarbitone anaesthesia, to investigate the spinal cord structures involved in the intersegmental transmission of d.r.p.s. 2. A technique has been developed for restricted surgical isolation of Lissauer's tract between the segments with subsequent histological verification of the extent of the isolation. 3. Section of the ipsilateral dorsal column resulted in an increase in the latency of the intersegmental d.r.p. and a significant reduction in its amplitude. A further reduction in amplitude was achieved by section of the ipsilateral dorso‐lateral funiculus. 4. Neither section of Lissauer's tract after the above lesions were performed nor restricted Lissauer's tractotomies abolished intersegmental d.r.p.s; only a small reduction in the amplitude of the d.r.p. was obtained. 5. It is proposed that intersegmental d.r.p.s are produced by the activaiton of a propriospinal system projecting through pathways other than Lissauer's tract and that primary afferent collaterals from the dorsal columns make a major contribtuion to their generation. The contribution made by Lissauer's tract is probably small.
Efflux of inorganic phosphate from mammalian non‐myelinated nerve fibres.
Authors: Ferrero J , Jirounek P , Rouiller M , Straub R W
Published: December 2014

1. Uptake and release of radiophosphate were measured in desheathed rabbit vagus nerve. 2. During incubation in Locke containing 0.2 mM‐[32P]phosphate a slow labelling of water soluble compounds of the nerve was found; the labelling of the non water soluble compounds was much smaller. During washing with inactive Locke, the label was almost entirely released from the water soluble compounds; the radioactivity of these compounds was therefore used as the basis for the calculation of the efflux rate constants. 3. The efflux of radiophosphate increased with increasing phosphate concentration of the washing fluid. 4. A similar effect of external phosphate on the efflux of radiophosphate was seen when the phosphate concentration was suddenly changed. The rate constants were in 0.2 mM‐phosphate 1.29 X 10(‐3) min‐1, in 0.2 mM 1.95 X 10(‐3) min‐1, and in 2 mM 3.21 X 10(‐3) min‐1 at 37 degrees C. After changing the external solution the efflux reached a new level with a time constant of about 9 min. 5. Addition of arsenate also increased the efflux of radiophosphate; on a molar basis the effect of arsenate was slightly smaller than the effect of phosphate. 6. Addition of malate or malonate did not affect the efflux of radiophosphate. 7. When the Na of the Locke was replaced by Tris, the efflux of radiophosphate was lowered by 76%, the new level was reached with a time constant of 7.7 min. In Tris‐Locke changes in external phosphate did not affect the phosphate efflux. 8. A lowering of the phosphate efflux by 52% was found in Li‐Locke; the efflux was then no longer affected by the external phosphate concentration. 9. The effect of external phosphate on the efflux and in the radiophosphate was also measured at intermediate Na concentrations. At different Na concentrations the ratio between the Na dependent effluxes in 2 and 0.2 mM‐phosphate was approximately equal to the ratio between the Na dependent influxes in 2 and 0.2 mM‐phosphate. 10. The efflux of 22Na had a rate constant of 0.050 min‐1 in Locke and 0.046 min‐1 in Tris‐Locke. 11. It is concluded that part of the efflux of phosphate is mediated by a Na‐dependent transport system; the system appears to be able to exchange phosphate between the inside and the outside and to mediate net movements of phosphate in both directions.
Electrophysiological characteristics of renorenal reflexes in the cat.
Authors: Calaresu F R , Kim P , Nakamura H , Sato A
Published: December 2014

1. Experiments were done in anaesthetized, paralysed and artificially ventilated cats to determine the fibre composition of renal nerves and to study the functional characteristics of reflex responses recorded in efferent renal nerves during electrical stimulation of contralateral and ipsilateral afferent renal nerves. 2. Renal nerves were found to contain three afferent fibre groups (Abeta, Adelta and C); the majority of these fibres reach the sympathetic chain through the least splanchnic nerve. Efferent sympathetic nerves to the kidney were found to originate from the greater, lesser and least splanchnic nerves through a synapse in the coeliac ganglion. 3. Two contralateral renorenal reflex responses were demonstrated during selective stimulation of renal afferent A and C fibres. The first (A renorenal reflex) was elicited by stimulation with trains of pulses at low voltage and high frequency (200 Hz), had an onset latency of approximately 100 msec and was followed by post‐excitatory depression. The second (C renorenal reflex) was demonstrated by trains of pulses at high voltage and low frequency (20‐‐30 Hz), had an onset latency of approximately 350 msec and was also followed by post‐excitatory depression. 4. Ipsilateral renorenal reflexes with characteristics similar to the contralateral reflexes were also demonstrated. 5. Renorenal reflexes were abolished by destruction of the spinal cord and administration of nicotine sulphate (5‐‐20 mg/kg, i.v.), but were not affected by bicuculline (0.4 mg/kg, i.f.). 6. The significance and the physiological role of these renorenal reflexes as well as their pathways within the central nervous system remain to be determined.
Modulation of ouabain binding and potassium pump fluxes by cellular sodium and potassium in human and sheep erythrocytes.
Authors: Joiner C H , Lauf P K
Published: December 2014

1. Erythrocytes were treated with nystatin to alter internal Na (Nai) and K (Ki) composition. Although the rates of K pumping and [3H]ouabain binding were altered dramatically, the relationship between glycoside binding and K pump inhibition was unaffected. 2. Human cells with high Nai and low Ki exhibited an increased rate of ouabain binding as compared to high Ki, low Nai cells; this paralleled the stimulated K pump activity of high Nai cells. 3. At constant Ki, increasing internal Na stimulated K pump and ouabain binding rates concomitantly. 4. At low Nai, increasing Ki inhibited both K pumping and ouabain binding. However, at high Nai, increasing Ki from 4 to 44 mM stimulated the rate of glycoside binding, parallel to its effect of increasing the rate of active K influx. 5. Anti‐L, an isoantibody to low K (LK) sheep red cells, increased the rate of ouabain binding via its stimulation of K pump turnover. Since the latter effect is the result of affinity changes at the internal cation activation site(s) of the pump (Lauf, Rasmusen, Hoffman, Dunham, Cook, Parmelee & Tosteson, 1970), the antibody's effect on ouabain binding reflected the positive correlation between the rates of K pump turnover and glycoside binding. 6. These data provide the first evidence in intact cells for the occurrence of a Nai‐induced conformational change in the Na/K pump during its normal operational cycle.
Comparison of adenylate cyclase activity and in vitro secretion in the parotid and sublingual glands of the mouse.
Authors: Nieuw Amerongen A V , Roukema P A , Vreugdenhil A P
Published: December 2014

1. Adenylate cyclase (EC 4.6.1.1) activity has been determined in the parotid and sublingual glands of the mouse. Optimal activity of the enzyme was obtained at a Mg2+‐concentration of 8 mM at pH 8.2, using AMP‐PNP as the substrate. 2. Cyclic AMP degradation during the adenylate cyclase assay was relatively high in both the homogenate and the 40,000 g pellet‐fraction of the glands. Theophylline was effective in inhibiting this degradation only in the parotid hemogenate, whereas isobutylmethylxanthine inhibited the cyclic AMP degradation in both salivary glands. Using the latter phosphodiesterase inhibitor, we observed a higher adenylate cyclase activity in the sublingual glands than in the parotid glands. 3. Various receptor‐selective sympathetic and parasympathetic agonists and antagonists have been tested for their capacity to influence the adenylate cyclase activity and the glycoprotein secretion in the parotid and sublingual glands of the mouse, in vitro. (a) The parotid glycoprotein secretion was increased by beta‐adrenergic agonists, which stimulate adenylate cyclase, and by cholinergic muscarinic drugs, which do not activate this enzyme. The adrenergic alpha‐agonist phenylephrine appeared to be involved neither in the glycoprotein secretion nor in the direct regulation of the adenylate cyclase activity. (b) The sublingual protein and mucin secretion was increased by cholinergic muscarinic agents. The over‐all protein secretion was stimulated also by phenylephrine, but this effect could be blocked by propranolol. The adenylate cyclase activity in membrane preparations was not stimulated by these secretogogues.
The effect of pituitary‐adrenal function in the modulation of pain sensitivity in the rat
Authors: Heybach John P. , Vernikos-Danellis Joan
Published: December 2014

1. The relationship between adrenalcortical hormones, adrenocorticotrophic hormone (ACTH), and pain sensitivity was investigated in the rat. Pain sensitivity was assessed by measuring paw‐lick and jump latencies in response to being placed on a grid at 55 °C.

2. Bilateral adrenalectomy increased the sensitivity to pain, but adrenal demedullation had no effect.

3. Pain sensitivity was inversely related to the circadian changes in circulating corticosterone and was greater at 7 a.m. than at 7 p.m. However, the same variation in pain sensitivity existed if the adrenals were removed, suggesting that the increase in pain sensitivity after adrenalectomy was not related directly to the levels of corticosteriods.

4. The time course of the increase in pain sensitivity after adrenalectomy paralleled that of the changes in circulating ACTH. Adrenalectomy markedly increased pain sensitivity at 9 and 18 days following surgery when circulating ACTH levels were markedly elevated and corticosterone was absent, but not at 3 days following adrenalectomy when ACTH levels were lower and corticosterone was absent.

5. Hypophysectomy decreased the sensitivity to pain.

6. The results indicate that ACTH can alter pain sensitivity and that the effect of corticosteroids on the sensitivity to pain is an indirect one by virtue of their negative feed‐back action on the hypothalamic‐pituitary system.
Glucose, glycine and diglycine in test meals at stimuli to a duodenal osmoreceptor slowing gastric emptying.
Authors: Barker G R , Cochrane G M , Corbett G A , Dufton J F , Hunt J N , Roberts S K
Published: December 2014

1. Five subjects took 210 test meals of 750 ml. water containing 30‐‐300 m‐molal glucose or glycine, or 15‐‐150 m‐molal diglycine, or plain water. 2. The greater the concentration of solute, the greater was the volume of original meal recovered from the stomach after a fixed time. 3. On a molal basis glucose was half as effective as diglycine in slowing gastric emptying. This was consistent with the osmoreceptor being exposed to the diglycine after it had been split by the hydrolase of the cytosol of enterocytes (the absorbing cells of the small intestine). 4. The slowing of gastric emptying (ml./mole.1.) was about 10% greater for glycine than it was for glucose. There was apparently a threshold concentration below which glycine did not slow gastric emptying. 5. It was proposed that the response of the doudenal osmoreceptor might depend upon shrinking and swelling of the lateral intercellular space around the enterocytes.
Projections of primary afferent fibres from muscle to neurones of the spinocervical tract of the cat.
Authors: Hamann W C , Hong S K , Kniffki K D , Schmidt R F
Published: December 2014

1. Micro‐electrode recordings were made from axons in the spinocervical tract of decerebrate‐spinal cats. 2. The effect of electrical stimulation of afferent fibres in muscle nerves was examined. 3. Stimulation of group III fibres in muscle nerves excited hair only and hair and pressure units in the spinocervical tract. Hair and pressure units also responded to electrical stimulation of group IV fibres. 4. Units of the spinocervical tract excited by stimulation of muscle nerves had receptive fields in the skin overlying the relevant muscles. 5. Stimulation of group III fibres in muscle nerves produced long lasting inhibition of spinocervical tract units. In two such units the inhibitory action of afferent myelinated fibres was enhanced by increasing the stimulus strength so that group IV fibres were recruited.
Regulation of calcium fluxes in pancreatic islets: dissociation between calcium and insulin release.
Authors: Herchuelz A , Malaisse W J
Published: December 2014

1. The release of 45calcium from prelabelled pancreatic islets is rapidly and almost totally inhibited by lanthanum. 2. Glucose provokes an intitial fall followed by a secondary rise in 45calcium efflux. The latter rise occurs concomitantly with insulin release. Its magnitude is reduced whenever the secretory response to glucose is inhibited, e.g. in the absence of extracellular calcium, presence of Verapamil, or at high magnesium concentration. 3. However, under suitable conditions, the glucose‐induced secondary rise in 45calcium efflux is not totally suppressed whilst insulin release is totally abolished. 4. Inversely, when calcium is replaced by barium in the perifusate, glucose increases insulin output without causing any obvious secondary rise in 45calcium efflux. 5. It is concluded that this secondary rise, which originates from a lanthanum‐nondisplaceable calcium pool, does not correspond solely to an exocytotic release of 45calcium. It could represent, in part at least, a displacement of 45calcium from cellular sites and reflect a glucose‐induced increase in the rate of calcium entry in islet cells.
Acute compensatory adaptation of renal function following contralateral kidney exclusion in Brattleboro rats with diabetes insipidus.
Authors: Shirley D G , Skinner J
Published: December 2014

1. The function of the remaining kidney following ligation of a single renal pedicle in anaesthetized rats with hereditary hypothalamic diabetes insipidus (DI) was studied using clearance methods. Values were compared with those obtained in DI rats which had been sham operated. 2. A small increase in the glomerular filtration rate of the remaining kidney was observed, which was statistically significant after 150 min. Increases in effective renal plasma flow were also observed, but these were not statistically significant. 3. The fractional excretion rates of Na and K increased immediately after contralateral kidney ligation; as a result total Na and K excretion rates remained similar to values in sham operated animals with both kidneys intact. 4. Fractional urine flow (V/GFR) increased by approximately 40% after contralateral ligation. It is argued that, since water reabsorption in the diluting segments of the nephron was unlikely to have been reduced, the increase in V/GFR was an indication that fractional fluid reabsorption in the proximal nephron had been inhibited. 5. Clearance determinations showed that the fractional reabsorption of Na in the proximal nephron was similarly reduced after contralateral ligation. However, Na reabsorption in the distal nephron increased, though not by enough to prevent a doubling of fractional sodium excretion. 6. The osmolalities of interstitial fluids obtained from the medulla and papilla of the contralateral kidney 2 hr after unilateral renal pedicle ligation were slightly, but significantly, higher than corresponding values in sham operated rats. This raises the possibility that salt reabsorption in the ascending limb of Henle might be enhanced immediately after contralateral renal exclusion.
Simultaneous measurement of pressure in the interstitium and the terminal lymphatics of the cat mesentery.
Authors: Clough G , Smaje L H
Published: December 2014

1. Simultaneous measurements of the pressure in terminal lymphatics and interstitial tissue have been made in the exteriorized cat mesentery superfused with either physiological salt solution (Krebs solution) or a water‐immiscible fluorocarbon, FC‐80. 2. The pressures within individual terminal lymphatics were measured using glass micropipettes attached to a servo pressure‐measuring system. Tissue pressures were recorded using saline‐filled cotton‐wool wicks. 3. Mean pressure recorded in the terminal lymphatics of the Krebs‐superfused mesentery were slightly above atmospheric (+0.2 mmHg, n = 45), while those recorded in the FC‐80‐superfused mesentery were slightly below atmospheric (‐0.2 mmHg, n = 46). 4. Tissue pressures were also slightly subatmospheric in the in situ mesentery, and the recently exposed tissue. Continuous superfusion with Krebs solution caused the tissue pressure to rise to atmospheric pressure or above; with FC‐80‐superfusion the tissue pressure also rose, but never to above atmospheric pressure. 5. Isolated strips of mesentery immersed in Krebs solutions of different concentrations gained weight, but when immersed in FC‐80 no change in weight was detected. 6. It was concluded that the interstitial gel of the mesentery is normally unsaturated and that superfusion with Krebs solution leads to tissue oedema. This tendency is less marked in FC‐80‐superfused preparations. Possible mechanisms for lymph formation and propulsion are discussed.
Interpretation of perceived motor commands by reference to afferent signals.
Authors: Gandevia S C , McCloskey D I
Published: December 2014

1. Weights were lifted by flexing the distal joints of the anaesthetized thumbs. A weight‐matching task was used to determine the perceived heaviness of a reference weight during control estimates when it was freely lifted, and during experimental estimates when the weight was not lifted, but simply 'gave way' when a reference isometric tension of the same magnitude was attained. 2. Limitation of the afferent input, by anaesthesia of the digit and by replacing lifting with a sudden unloading, did not grossly impair the judgement of heaviness. The sense of heaviness increased when the muscles became fatigued. 3. These results suggest that the central nervous system can interpret the voluntary motor command as an index of heaviness even when provided with only a crude peripheral signal that the weight has been moved.
Action potentials of embryonic dorsal root ganglion neurones in Xenopus tadpoles.
Authors: Baccaglini P I
Published: December 2014

1. Several classes of action potentials can be distinguished in dorsal root ganglion cells, studied by intracellular recording techniques in Xenopus laevis tadpoles 4.5‐‐51 days old. The ionic basis of the action potential was investigated by changing the ionic environment of the cells and applying various blocking agents. 2. The Ca2+‐dependent action potential is a plateau of relatively long duration (mean 8.7 msec). It is unaffected by removal of Na+ but blocked by mM quantities of Co2+. It is present only in small cells. 3. Ca2+/Na+‐dependent action potentials. Type I is a spike followed by a plateau or hump of different durations (mean 8.1 msec). The spike is selectively blocked by removal of Na+, leaving the plateau which is in turn blocked by Co2+. It is present in cells of small and intermediate size. Type II is a spike of short duration (mean 2.0 msec) with only an inflection on the falling phase. The spike is blocked by removal of Na+ and no other components can be elicited. The inflection is blocked by Co2+. It is present in cells of all sizes. Type III is similar to type I but is seen only in solutions in which the outward current is blocked. It was observed only very infrequently. 4. Na+‐dependent action potentials. Type I a is a short duration spike (mean 1.1 msec). It is abolished by removal of Na+ or addition of tetrodotoxin (TTX), but largely unaffected by Co2+ or La3+. It is present in cells of all sizes. When the outward current channels are blocked and cells exposed to Na+‐free solutions, all cells are capable of producing an action potential in which the inward current is carried by divalent cations. Type I b is a spike with a smooth, more slowly falling phase. It has the same pharmacological properties as type I a action potential and is present in cells of small size. 5. Na+‐dependent action potentials. Type II is a spike with an inflection on the falling phase (mean duration 3.4 msec). It is prolonged by Co2+ and La3+. Removal of Na+ abolishes the spike but TTX does not block it. It is present in cells of all sizes. The mean resting potential is less than that of cells with Na+‐dependent type I action potentials, while the mean input resistance is greater. 6. Tetraethylammonium chloride (TEA) prolongs the different kinds of action potentials. The amount of prolongation varies among cells with a given type of action potential, so that no distinction could be made of the different actionpotential types based on the effect of TEA. 7. The percent of cells with each kind of action potential varies with the developmental age of the animal. The number of cells with Ca2+ and Ca2+/Na+ action potentials decreases with age, while the number of cells with a Na+ type I action potentials increases. The Na+ type II action potential appears only at later stages. 8...