bluuebunny/crossref_metadata_2025 huggingface dataset:
Facilitation of secretion of catecholamines from rat and guinea‐pig adrenal glands in potassium‐free medium or after ouabain.
Authors: Wakade A R
Published: December 2014

1. The effect of K deprivation on catecholamine (CA) secretion induced by transmural stimulation of the isolated perfused adrenal glands of the rat was studied. 2. In the absence of external K, secretion of CA evoked by transmural stimulation was greatly (2‐ to 7‐fold) facilitated. The facilitation was inversely related to the frequency of stimulation. The duration of CA secretion upon stimulation was prolonged significantly in K‐free medium as compared to that in Krebs solution. 3. CA secretion evoked by acetylcholine (ACh) in K‐free Krebs solution was increased by about 40%, with little change in the duration of secretion. 4. Chronic denervation of the adrenal gland practically abolished secretory response induced by transmural stimulation without affecting secretion of CA by ACh. Perfusion of the denervated adrenal gland with K‐free solution enhanced ACh‐induced CA secretion by about 40%, and a secretory response to transmural stimulation became evident. 5. Spontaneous secretion of CA was increased from a control value of about 2 ng/min to 56 ng/min 35 min after perfusion with K‐free Krebs solution. During enhanced spontaneous secretion, electrical stimulation of the adrenal gland produced facilitation of secretion. 6. Spontaneous secretion of CA in K‐free medium was only slightly reduced by lowering Ca to 0.25 mM, but that evoked by stimulation was markedly depressed. However, spontaneous and evoked secretion in K‐free medium were totally blocked upon removal of Ca and addition of 5 mM‐EGTA. 7. Re‐introduction of 2.5 mM‐Ca 6 min after stimulation of the adrenal gland in 0.25 mM‐Ca, K‐free solution produced a marked secretory response. 8. Lowering of Ca to 0.25 mM immediately after stimulation of the adrenal gland in K‐free solution significantly reduced the amounts of CA secreted in the post‐stimulation period. 9. Ouabain (0.14‐1.4 mM) did not enhance secretion of CA in unstimulated preparations or after transmural stimulation of the rat adrenal gland. ACh‐induced secretion was more than doubled by ouabain. 10. Not only was spontaneous secretion of CA from the guinea‐pig adrenal gland enhanced by K deprivation or ouabain, but secretion evoked by transmural stimulation or by ACh was also facilitated in K‐free medium by ouabain (0.7‐7.0 microM). 11. Enhanced secretion of CA in unstimulated preparations or after transmural stimulation of the adrenal gland, in the absence of K, has been attributed to the excess release of ACh from splanchnic nerve terminals. The enhanced release of ACh has been attributed to the elevation of free cellular CA resulting from blockade of the Na pump. On the other hand, ouabain facilitates CA secretin in the rat and guinea‐pig adrenal glands predominantly by its effect on the chromaffin cells.
Effect of pancreatic polypeptide and its C‐terminal hexapeptide on meal and secretin induced pancreatic secretion in dogs.
Authors: Chance R E , Cieszkowski M , Jaworek J , Konturek S J , Swierczek J , Tasler J
Published: December 2014

1. Gastric acid and pancreatic bicarbonate and protein secretion as well as immunoreactive serum gastrin and pancreatic polypeptide concentrations in response to a meal and secretin have been measured before and after infusion of bovine pancreatic polypeptide or its C‐terminal hexapeptide. 2. Liver extract meal kept in the stomach at pH 5.5 (by intragastric titration) produced a marked increase in gastric acid and pancreatic protein secretion accompanied by a rise in serum gastrin and pancreatic polypeptide levels. Exogenous bovine pancreatic polypeptide caused little change in gastric secretion and serum gastrin but resulted in a profound suppression of pancreatic secretion. 3. Ordinary feeding a liver meal produced a marked increase in pancreatic bicarbonate and protein secretion that was dose‐dependently inhibited by bovine pancreatic polypeptide or its C‐terminal hexapeptide, the degree of inhibition being closely correlated with the increments in plasma pancreatic polypeptide. 4. Bovine pancreatic polypeptide and its C‐terminal hexapeptide also inhibited secretin and caerulein‐induced pancreatic secretion in a dose‐dependent manner. 5. This study shows that bovine pancreatic polypeptide inhibits pancreatic secretion at least in part by acting directly on the exocrine pancreas and that its biological activity resides in its C‐terminal hexapeptide fragment.
Thermogenesis in normal rabbits and rats: no role for brown adipose tissue?
Authors: Brockway J M , Lobley G E
Published: December 2014

1. The occurrence of dietary and cold‐induced thermogenesis in young rabbits was unaffected by noradrenaline or propranolol, and it is concluded that the brown adipose tissue, although detectable histologically, is non‐functional. 2. Noradrenaline treatment caused an increase in oxygen consumption in albino, but not in hooded rats, suggesting that the former breed may possess brown adipose tissue capable of thermogenesis.
Slow potassium contractures in mouse limb muscles.
Authors: Dulhunty A F
Published: December 2014

1. Mouse extensor digitorum longus and soleus muscles respond to a sudden maintained increase in external K ion concentration with a fast contracture which inactivates and is followed by a slow contracture. 2. The slow contracture could not be selectively eliminated by altering the tonicity, ionic strength, anionic composition or buffer system of the external solution and depended only on the increase on external potassium concentration. The slow contracture differed from the fast K contracture in its time course, temperature sensitivity, fibre type dependence, and inactivation kinetics. The fast and slow contractures were similarly altered by changes in external anion species, by changes in external divalent cations, and by the presence of 20 mM‐caffeine. 3. The mechanism and functional significance of the slow contracture are obscure. The results suggest that its generation is not identical to that of the fast contracture, but may depend, in part, upon the normal activation processes.
Spatial and temporal properties of cat geniculate neurones after prolonged deprivation.
Authors: Derrington A M , Hawken M J
Published: December 2014

1. Extracellular recordings were made from the dorsal lateral geniculate nucleus of monocularly deprived, dark‐reared and normal cats. The spatial and temporal properties of the neurones were studied. 2. The mean acuity of X‐cells with receptive fields 3 degrees of the area centralis was 3.9 c/degree for deprived eye cells from monocularly deprived cats, compared was 3.8 c/degree for normal cells. 3. The mean activity of X‐cells with receptive fields within 4 degrees of the area centralis was 4.3 c/degree for a dark‐reared cat compared with 4.0 c/degree for a normal cat. 4. The peak response rates of X‐cells to their best spatial frequency were determined. The mean values for the normal, monocularly deprived and dark‐reared populations were all similar. 5 Measurement of the temporal frequency tuning of a number of cells was made. The mean peak temporal frequency for the dark‐reared X‐cells was lower than for monocularly deprived or normal X‐cells. 6. The results are discussed with reference to the location of the primary neural deficit induced by visual deprivation.
Responses of pontine units to skin‐temperature changes in the guinea‐pig
Authors: Hinckel P. , Schröder‐Rosenstock K.
Published: December 2014

1. The responses of fifty‐five single units to changes in skin temperature were recorded in twenty‐three guinea‐pigs anaesthetized with urethane. Skin‐temperature changes were induced by changing the temperature of the water‐perfused support plate of the stereotaxic apparatus and that of the double‐walled Perspex jacket that was put on the support plate.

2. Thirty‐three units were stereotaxically and histologically verified as being within a circumscribed area of the pontine dorsomedial reticular formation (subcoeruleus region). Twenty‐one units were located in the surrounding areas, and one unit in the nucleus raphé magnus region.

3. Twenty‐seven of thirty‐three recorded subcoeruleus units were specifically excited by cooling of the abdominal or leg skin, whereas only five units were non‐thermoresponsive and one unit was warm‐responsive. The cold‐responsive units had peak activity at skin temperatures between 22 and 29 °C, in accordance with the maximum activity in cutaneous cold‐receptors.

4. A markedly different distribution of units was found in the surrounding areas. Only four units were cold‐responsive. Thirteen units were non‐thermoresponsive, and four units were warm‐responsive.

5. The cold‐responsive subcoeruleus units were situated in regions which are known to contain accumulations of noradrenergic cell bodies, and to project to hypothalamic neurones. Electrical stimulation of these regions is known to cause excitatory metabolic responses in unanaesthetized guinea‐pigs. It is concluded that part of the cutaneous cold‐afferents projects to hypothalamic thermointegrative neurones via noradrenergic pathways that ascend from these subcoeruleus regions.
Interactions among rods in the isolated retina of Bufo marinus.
Authors: Griff E R , Pinto L H
Published: December 2014

1. The existence and extent of interactions among rods were analysed in the isolated retina of Bufo marinus. Intracellular recordings were made from the outer segments with micropipettes. Stimuli of precisely measured geometry were delivered to the outer segments using a compound microscope. 2. To demonstrate the existence of interactions two rods were simultaneously impaled; current injected into one rod resulted in a current‐induced potential of like sign in the other rod. 3. When the diameter of a circular stimulus was increased from 30 to 500 micrometer the mean sensitivity of the rods increased by 1.2 +/‐ 0.3 log units (S.D.), though the illuminance measured through the impaled rod was adjusted to be constant. 4. The extent of interactions was examined by presenting a dim, slit‐shaped stimulus at each of several displacements from an impaled rod. This stimulus either passed through the retina before coming into focus on the outer segments (transillumination) or was focused directly on the outer segments (incident illumination). For each displacement both the amount of light scattered onto the impaled rod and the response of the rod were measured. 5. The amount of light scattered onto the impaled rod was assessed for each displacement of the stimulus. For incident illumination this assessment was made by measuring the distribution of bleached pigment about the slit stimulus. The bleaching could be described by an exponential that decreased with distance; this exponential had a space constant of 4 micrometer. For transillumination the assessment was made in two ways. The light that passed through the impaled rod was measured and found to decrease exponentially with slit displacement; the mean space constant of this exponentially was 9.3 +/‐ 3.2 micrometer (S.D.). In few experiments the distribution of bleached pigment about the slit stimulus was measured and was found to decrease exponentially with distance; this latter exponential had a slightly longer space constant than the exponential measured using transmitted light. 6. For each impaled rod a convolution of an exponential interaction function with the measured distribution of stimulus illuminance about the impaled rod could be fitted to the plot of response amplitude versus displacement of the slit stimulus. For stimuli presented by transillumination the mean space constant describing the interaction functions was 20 +/‐ 6 micrometer (S.D.). For stimuli presented by incident illumination the mean space constant of the interaction functions was 22 +/‐ 4 micrometer (S.D.). 7. This report presents new evidence that interactions among rods exist in the isolated retina and that the extent of interactions can be described by a space constant of about 20 micrometer.
Intracellular magnesium does not antagonize calcium‐dependent acetylcholine secretion.
Authors: Kharasch E D , Mellow A M , Silinsky E M
Published: December 2014

1. The effects of intracellular application of Ca and Mg ions on evoked acetylcholine secretion at frog motor nerve terminals were studied. Ca and Mg were applied to the nerve‐ending cytoplasm using liposomes as a vehicle. 2. Under conditions in which intracellular application of Ca produced many‐fold increased in evoked acetylcholine release. 3. When Mg was applied to the nerve‐ending cytoplasm concurrently with Ca, acetylcholine release was further increased above the level produced by introducing Ca alone. 4. The results suggest that intracellular Mg does not antagonize depolarization‐secretion coupling and that antagonism of transmitter release by extracellular Mg occurs only at the external surface of the nerve ending.
Electrophysiological analysis of mitral cells in the isolated turtle olfactory bulb.
Authors: Mori K , Nowycky M C , Shepherd G M
Published: December 2014

1. An in vitro preparation of the turtle olfactory bulb has been developed. Electrophysiological properties of mitral cells in the isolated bulb have been analysed with intracellular recordings. 2. Mitral cells have been driven antidromically from the lateral olfactory tract, or activated directly by current injection. Intracellular injections of horseradish peroxidase (HRP) show that turtle mitral cells have long secondary dendrites that extend up to 1800 micrometer from the cell body and reach around half of the bulbar circumference. There are characteristically two primary dendrites, each supplying separate olfactory glomeruli. 3. Using intracellular current pulses, the whole‐neurone resistance was found to range from 33 to 107 M omega. The whole‐neurone charging transient had a slow time course. The membrane time constant was estimated to be 24‐93 msec by the methods of Rall. The electrotonic length of the mitral cell equivalent cylinder was estimated by Rall's methods to be 0.9‐1.9. 4. The spikes generated by turtle mitral cells were only partially blocked by tetrodotoxin (TTX) in the bathing medium. The TTX‐resistant spikes were enhanced in the presence of tetraethylammonium (TEA), and blocked completely by cobalt. 5. The implications of the electrical properties for impulse generation in turtle mitral cells are discussed. The mitral cells have dendrodendritic synapses onto granule cells, and the TTX‐resistant spikes may therefore play an important role in presynaptic transmitter release at these synapses.
Analysis of a long‐duration inhibitory potential in mitral cells in the isolated turtle olfactory bulb.
Authors: Mori K , Nowycky M C , Shepherd G M
Published: December 2014

1. An inhibitory potential of long duration has been analysed in intracellular recordings from mitral cells in the isolated turtle olfactory bulb preparation. 2. A single volley in the olfactory nerves or lateral olfactory tract elicited synaptic inhibition in mitral cells, followed by a long‐lasting hyperpolarization of the cell. This slow potential has been termed the Is component, to distinguish it from the earlier I1 and I2 components to the inhibitory post‐synaptic potentials (i.p.s.p.s). 3. The slow Is component was inhibitory, as shown by the interruption of spontaneous discharges, and the blockage of responses to injected current and incoming volleys. The duration of the hyperpolarization following a single volley usually lasted up to 5 sec, and occasionally longer. 4. The Is response decreased in amplitude with either depolarizing or hyperpolarizing current injection, without showing a reversal potential. This contrasted with the earlier I1 and I2 components, which showed reversal potentials characteristic of i.p.s.p.s. 5. Tests of membrane conductance showed that the conductance, which was increased during the preceding i.p.s.p., decayed to control values during the early part of the Is potential. 6. The Is response shares some characteristics with slow potentials reported in certain other vertebrate neurones. This type of response may be involved in longer‐term neuromodulatory control of the excitability of the mitral cell.
The anatomical location of the series elastic component in rat vascular smooth muscle.
Authors: Mulvany M J , Warshaw D M
Published: December 2014

1. Flash photomicrographs using Nomarski optics have been taken of the smooth muscle cells in an activated arterial resistance vessel preparation (i.d. approximately 150 micrometers) before and after a quick release of internal circumference in an attempt to determine the location of the series elastic component (s.e.c.). 2. If the s.e.c. lies mainly within the smooth muscle cells, then, while the position of an intracellular structure would change during a release, there would be little change in its position after the release during tension recovery. 3. The movement of intracellular structures during a quick release, x, and the corresponding movement during tension recovery, y, was determined by taking double flash exposures at the appropriate times and measuring the separation of the double images on the film. In eighty‐five pairs of measurements from seven vessels the ratio y/x was equal to 0.21 +/‐ 0.02 (S.E.). 4. The results show that less than half of the smooth muscle s.e.c. resides in extracellular components. The active dynamic stiffness of smooth muscle cells is substantially less than that of skeletal muscle fibres.
Mechanism of the effect of cyanide on cell membrane potentials in Necturus gall‐bladder epithelium.
Authors: Bello‐Reuss E , Grady T P , Reuss L
Published: December 2014

1. Addition of sodium cyanide to the mucosal or the serosal medium bathing the isolated gall‐bladder of Necturus maculosus causes hyperpolarization of both apical and basolateral membrane of the epithelial cells. The effect of cyanide is practically immediate, reversible (if exposure is brief), and long‐lasting (greater than 30 min). 2. The hyperpolarization is accompanied by: (a) reduction of the equivalent resistance of the cell membranes, as shown by cable analysis and input resistance measurements, and (b) increase of the potassium selectivity of both cell membranes, as evidenced by the effects of external substitutions of potassium for sodium on cell membrane potentials. We conclude that the cyanide‐induced hyperpolarization is caused mainly or exclusively by an increase of the potassium permeability of the cell membranes. 3. Addition of the calcium ionophore A23187 (5 microM) to the mucosal medium in the presence of 1 mM‐calcium caused similar effects to those produced by cyanide. After either cyanide or A23187, addition of the other agent did not cause further membrane potential changes. 4. Quinine (100 microM, mucosal medium) reduced the potassium permeability of the apical membrane both under control conditions and during exposure to cyanide. 5. We suggest that the cyanide‐induced increase of the potassium permeability of the cell membrane is mediated by an elevation of intracellular calcium ion activity, attributable to release from mitochondrial sources.
A new interpretation of the pace‐maker current in calf Purkinje fibres.
Authors: DiFrancesco D
Published: December 2014

1. The properties of the ‘pace‐maker’ current iK2 of Purkinje fibres are investigated to verify whether its behaviour during voltage‐clamp pulses is consistent with the view that iK2 is a K current deactivating on hyperpolarization in the range ‐50 to ‐100 mV. 2. During voltage‐clamp pulses in the range positive to the apparent reversal potential (Erev), low concentrations of Cs depress the time‐dependent current change without altering the time‐independent current component. The total current becomes more outward in Cs, which on the assumption that Cs only affects the iK1 and iK2 channels implies that iK2 is inward in the voltage range analysed. 3. Ba strongly reduces the time‐independent component due to iK1 and therefore limits the contribution of K depletion to the total current time course during hyperpolarizations. In the presence of barium a current reversal is not obtained even with large hyperpolarizations in normal Tyrode solution. If in Ba‐containing solutions the external K concentration is raised from 3 up to 48 mM, iK2 greatly increases in the inward direction during hyperpolarizations in the range ‐51 to ‐101 mV, implying that it cannot be carried by K only. 4. In the presence of Ba, measurements of the membrane conductance due to iK2 indicate a channel‐opening process during hyperpolarizations and a channel‐closing process during depolarizations, in the K‐concentration range analysed. 5. It is concluded that iK2 is not, as had been previously thought, a pure K current, but is rather an inward current activated during hyperpolarizations negative to about ‐50 mV. This provides further evidence for a possible identity between iK2 in Purkinje fibres and the current if in the SA node.
Mapping, in the rat central nervous system, of morphine‐induced changes in turnover of 5‐hydroxytryptamine.
Authors: Snelgar R S , Vogt M
Published: December 2014

1. It is known that the full clinical effect of morphine is not seen if those neurones of the central nervous system which contain 5‐hydroxytryptamine (5‐HT) have been inactivated. Morphine increases 5‐HT turnover in brain and cord, and the present work is an attempt at mapping the sites at which turnover is accelerated. 2. The degree of interaction at various sites of the C.N.S. was measured by the increment in the content of 5‐hydroxyindol‐3‐yl acetic acid (5‐HIAA) elicited by morphine in rats pre‐treated with probenecid. The effect was produced by as little as 3.5 mg morphine hydrochloride/kg; for the sake of convenience this dose was doubled in most experiments. Pre‐treatment with probenecid was not necessary for the effect, but a minimum interval of 90 min between injection of morphine and analysis of the brain was essential. 3. Morphine did not act indiscriminately on all 5‐HT neurons, as seen by the fact that the increment in 5‐HIAA formation was independent of the density of 5‐HT neurones in the tissue. Nor was there any relation between basal 5‐HT turnover of a region and the size of its response to morphine. 4. Highly reactive sites were found in dorsal cord, medulla, superior colliculi, substantia nigra, thalamus, hypothalamus, amygdala and striatum. Cortical areas were less responsive, but with large differences among themselves. Hippocampus, central grey, olfactory bulb, cerebellum and white matter had lower or negligible increases in 5‐HT turnover. There was no increase in the turnover of the (non‐neural) 5‐HT of the pineal gland. 5. The relation of the reactive sites to their content in endogenous opioids and to the probable localization of the pharmacological actions of morphine is discussed.
Intestinal bicarbonate secretion in Amphiuma measured by pH stat in vitro: relationship with metabolism and transport of sodium and chloride ions.
Authors: Imon M A , White J F
Published: December 2014

1. Isolated Amphiuma small intestine exposed on both surfaces to buffered or unbuffered media generated gradients of pH under short‐circuited conditions consistent with secretion of HCO3(‐). 2. When unbuffered mucosal medium was maintained at pH 7.4 by addition of acid, alkalinization of the mucosal medium occurred at a rate of 1‐2 microequiv/hr cm2 under short‐circuit conditions (Isc) and was reduced by anoxia, acetazolamide or removal of CO2. 3. The rate of HCO3(‐) secretion (JHCO3(‐)) was reduced at a mucosal pH above or below 7.4 and was proportional to serosal HCO3(‐). 4. JHCO3(‐) was reduced in Na+‐free (choline) and Cl‐free (SO4(2‐) media and after exposure to the stilbene SITS. 5. The difference JHCO3(‐)‐‐Isc was consistent with net Cl‐ absorption. 6. The tissue resistance (Rt) was elevated upon exposure to serosal HCO3(‐) and lowered by mucosal HCO3(‐). 7. The intestinal mucosa exhibited carbonic anhydrase activity that was sensitive to ethoxazolamide. 8. It is concluded that HCO3(‐) secretion is active, influenced by intracellular carbonic anhydrase activity and coupled to Cl‐ and possibly Na+ absorption.
An analysis of the regulation of sodium excretion during induced changes in plasma sodium concentration in anaesthetized dogs.
Authors: Gordon D , Nashat F S , Wilcox C S
Published: December 2014

1. Renal sodium excretion (UNaV) was studied during acute changes in plasma sodium concentration (PNa) induced by altering the concentration of a sodium chloride infusion in anaesthetized dogs. 2. The change in PNa induced other changes, notably in blood pH, the degree of blood dilution, and in glomerular filtration rate and renal plasma flow. No attempt was made to restrain these changes and their effects on UNaV were assessed using factor analysis. This defined new variables ('factors') that are linear functions of the primary variables. Four factors were defined, two of which were related to UNaV. 3. Factor 1 was strongly correlated with UNaV and PNa: its other correlations described the acidosis and plasma dilution of hypernatraemia. Further examination of these inter‐relationships by regression analysis and data selection showed that the increase in UNaV with rising PNa depended upon a fall in both the blood pH and PCO2. 4. Factor 2 was negatively correlated with UNaV: its correlations with plasma protein concentration, haematocrit, blood pressure, glomerular filtration rate and renal plasma flow implied that it represented post‐glomerular plasma protein concentration and its influence on sodium reabsorption. 5. Thus, two independent processes may regulate UNaV during acute salt loading: one is initiated by changes in PNa and plasma dilution but requires a concomitant acidosis and ventilatory adjustment for its full expression; the second relates UNaV to several variables whose influences could be understood by changes they produce in the peritubular capillary plasma protein concentration.
Membrane charge movement in contracting and non‐contracting skeletal muscle fibres
Authors: Horowicz P. , Schneider M. F.
Published: December 2014

1. The single gap voltage clamp technique (Kovács & Schneider, 1978) was used to monitor membrane charge movement in tendon‐terminated short segments of cut frog skeletal muscle fibres.

2. Experiments were performed both on fibres able to contract and on fibres in which contraction was eliminated by exposing the open end to a solution containing 20 m
m‐EGTA. In both cases ionic conductances were minimized by using a predominantly caesium glutamate solution at the open end and a predominantly tetraethyl‐ammonium sulphate solution with tetrodotoxin at the closed end.

3. Modifications of previously used charge movement analysis procedures included synthesis of a ‘mean linear’ ON and OFF capacitative transient from the OFFs of several different hyperpolarizing pulses and use of only the first 35 msec of the ‘mean linear’ transient so that base lines could be fitted to unaltered latter parts of ON and OFF currents for depolarizing pulses.

4. Simultaneous two‐micro‐electrode and gap current recording from gap‐clamped fibres with blocked contraction established the validity of gap‐recorded charge movement currents.

5. For pulses to below about 0 mV in non‐contracting fibres the charges QON and QOFF moved by the non‐linear transient currents at pulse ON and OFF were approximately equal. For pulses to between about 0 and +50 mV QOFF exceeded QON, with the charge inequality increasing with both pulse amplitude and pulse duration.

6. Use of 20 m
m‐cobalt in the solution at the closed end eliminated the ON:OFF charge inequality for large depolarizations by decreasing QOFF.

7. The charge inequality and cobalt effect indicate that, in the absence of cobalt, ionic conductance was being slowly activated during depolarizations to between 0 and +50 mV and that inward calcium current tails were contributing to the measured QOFF values. The small and slowly developing ionic current during large depolarizations was probably removed with the straight sloping base line so that QON was minimally affected by conductance activation.

8. Average Q vs. V results for pulses to at most 0 mV in eighteen non‐contracting fibres were well fitted by the two‐state Boltzmann model where Q = Qmax/[1+exp‐(V ‐ V̄)/k] with Qmax = 26·7±0·6 nC/μF, k = 16·7±0·6 mV and V̄ = ‐32·9±1·0 mV (least‐squares values±
s.d. obtained from fit).

9. In contracting fibres the only apparent artifact produced by contraction in the IQ records for pulses to at most 0 mV was a ‘bowing’ of the OFF base lines for the larger pulses. The ON records appeared to be unaffected by contraction artifacts.

10. The average Q vs. V relationship for pulses to at most 0 mV in contracting fibres was virtually identical to the one obtained from fibres in which contraction was blocked.

11. The ON portions of IQ records for pulses to between about ‐50 and ‐25 mV exhibited prolonged tails, plateaux or secondary rising phases whereas the OFF portions decayed smoothly. IQ time courses were not noticeably different with or without blockage of contraction by internal EGTA.
Pancreatic endocrine responses to stimulation of the peripheral ends of the vagus nerves in conscious calves.
Authors: Bloom S R , Edwards A V
Published: December 2014

1. The effects of stimulation of the peripheral ends of both vagus nerves below the heart (10 Hz for 10 min) were investigated in conscious calves 2‐5 weeks after birth. 2. Stimulation was invariably below behavioural threshold and caused a prompt increase in the concentrations of pancreatic glucagon, insulin and pancreatic polypeptide (PP) in the arterial plasma. Each of these responses was blocked by pretreatment with atropine (0.2 mg/kg). 3. Administration of exogenous glucose by continuous I.V. infusion (ca. 0.08 mmol kg‐1 min‐1) greatly enhanced the release of insulin in response to vagal stimulation without significantly changing that of pancreatic glucagon or PP. 4. Vagal stimulation also caused a significant rise in the concentration of vasoactive intestinal peptide (VIP) in the intestinal lymph and this response was found to persist in the presence of atropine.
Effects of catecholamines and cyclic amp on excitation‐‐contraction coupling in isolated skeletal muscle fibres of the frog.
Authors: Gonzalez‐Serratos H , Hill L , Valle‐Aguilera R
Published: December 2014

1. In skeletal muscle the presence of a positive inotropic effect induced by adrenaline has been a matter of controversy. If it exists, it could be due to catecholamines acting on the actomyosin system, on the sarcoplasmic reticulum (SR) Ca2+ pump or on the release or influx of Ca2+. We investigated these possibilities by using intact, split and skinned skeletal muscle fibres. We also investigated whether adrenaline acts directly or through cyclic AMP. 2. Catecholamines produced an increase in twitch tension and in maximum rates of tension development and tension decay. The inotropic effect took 3 min to appear and 8 min to reach its maximum level. With tetanic stimulations the extra force appeared only at the beginning of the tetanus while approaching the same maximum level, and tended to disappear faster, the higher the frequency of stimulation. At 4 shocks/sec the peak twitch tension with catecholamines decreased during the first seven to ten twitches and became steady afterwards at a level that was still greater than the control. 3. Resting and action potentials showed no important changes in the presence of adrenaline that could explain the inotropic effect. 4. In split fibres the force produced with the release of Ca2+ from the SR by caffeine was 60‐100% larger when cyclic AMP was added to the previous loading solution. In skinned fibres adrenaline given directly to the interior of the cell produced no changes in contraction‐‐relaxation cycles induced by fixed amounts of Ca2+ applied with a pipette. 5. These results strongly suggest that catecholamines through cyclic AMP stimulate the SR Ca2+ pump, increasing thereby the concentration of Ca2+ within the SR. This extra Ca2+ when released during subsequent activation may produce the increase in twitch tension.
Modification, by tractive loading, of the energy cost of walking in sheep, cattle and man.
Authors: Boyne A W , Brockway J M , Ingram J F , Williams K
Published: December 2014

1. A study was made in sheep and cattle walking on a treadmill, of the alteration to the energy expenditure that was caused by voluntarily exerted tension in the tether between animal and treadmill. 2. An additional experiment was carried out to investigate in human subjects walking on a treadmill, the alteration to the energy expenditure as a result of positive and negative tractive loads applied at waist level through a rope parallel to the plane of the treadmill. 3. Alterations to the net energy expenditure when walking were generally similar in the three species and varied with speed and gradient up to a maximum value of approximately 0.04 J per metre walked per gram of tension or negative load.
The effect of prolonged propranolol administration on myocardial transmural capillary density in young rabbits.
Authors: Tasgal J , Williams E M
Published: December 2014

1. As a sequel to previous evidence that prolonged beta‐adrenoceptor blockade in young rabbits led to a relative increase in the capillarity of ventricular muscle, an attempt has been made to localize and quantify the capillary density from epicardium to endocardium in 12‐week old rabbits treated for 6 weeks with propranolol (3 mg kg‐1) S.C. twice daily and in litter‐mates treated with saline (controls). 2. Full‐thickness 0.5 micrometers sections of the left ventricular wall were point‐counted in 200 micrometers steps. In the controls the capillary ‘volume density’ decreased progressively below the epicardial surface from a value of 9% to reach a minimum of 7.1% at a depth of 2.5 mm. Capillary density then increased again towards the endocardium, reaching a maximum of 11.5% in the trabeculae carnae (depth 3.5 mm). 3. In the treated animals the capillary density was increased in the mid wall at 2.3 and 2.5 mm, but significantly decreased in the trabeculae at 3.7 mm (P less than 0.05). 4. A more detailed analysis was undertaken at depths of 0.7 (Epi), 2.3 (Endo) and 3.5 mm (Trab), comprising estimates of capillary number, capillary diameter and intercapillary distance, via the stereological parameters of mean intercept length and mean free distance. 5. In the controls the order was Epi greater than Trab greater than Endo for number, Trab greater than Endo greater than Epi for diameter and Endo greater than Epi greater than Trab for intercapillary distance. 6. In the treated rabbits the mean intercapillary distance was significantly reduced in the epicardial (by 17.5%, P less than 0.05) and endocardial zones (by 32%, P less than 0.005), but was not significantly altered (+3.7%, P greater than 0.05) in the trabeculae. 7. The non‐uniform distribution of capillaries in the controls illustrates that detection of changes in transmural capillary density requires that the depth of samples be measured from the epicardial surface and not, owing to the presence of trabeculae carnae, from the endocardium. 8. If similar treatment effects were to occur in man, they would suggest that prolonged beta‐blockade could induce an increase in capillary density which would render the ventricular mid wall less susceptible to ischaemia.
Diastolic scattered light fluctuation, resting force and twitch force in mammalian cardiac muscle
Authors: Lakatta E. G. , Lappé D. L.
Published: December 2014

1. When coherent light was passed through isolated isometric cardiac muscles during the diastolic or resting period, intensity fluctuations were observed in the scattered field. The frequency of these intensity fluctuations (f½) varied with many experimental interventions known to enhance Ca2+ flux into the cell.

2. In rat muscles stimulated at low frequencies (0.1 ± 2.0 min−1) stepwise increases (0.4‐10 m
m) of [Ca2+] in the bathing fluid ([Ca2+]e), or addition of ouabain (10−6‐6 × 10−4
m) to the perfusate caused stepwise increases in f½. These were paralleled by increments in resting force (RF) such that the changes in f½ and RF were highly correlated. Substitution of K+ for Na+ in the perfusate resulted in parallel transients in RF and f½.

3. In contrast to the rat, most cat muscles stimulated at low frequencies in the steady state exhibited neither diastolic intensity fluctuations nor Ca2+‐dependent changes in RF in [Ca2+]e of 10 m
m or less; when [Ca2+]e was increased to 12‐32 m
m, however, steady‐state Ca2+‐dependent f½ and RF were observed. In a given [Ca2+]e reduction of [Na+]e increased f½. In the transient state following cessation of regular stimulation at more rapid rates (12‐96 min−1) intensity fluctuations were present in all [Ca2+]e and decayed with time (seconds to minutes); the f½ and time course of the decay of the fluctuations were determined by the rate of prior stimulation and [Ca2+]e.

4. Maximum potentiation of twitch force in response to the above inotropic interventions was associated with an optimal level of f½ which was similar in both species; when higher levels of f½ were produced by more intense inotropic intervention, twitch force declined. Over the range of inotropic intervention up to and including that at which maximum twitch potentiation occurred, the increase in diastolic f½ predicted the extent of twitch potentiation with a high degree of accuracy (r > 0.97) both in the transient and steady states.

5. In contrast to the other inotropic interventions studied, catecholamines were unique in that neither f½ nor RF increased over a full range of concentrations that resulted in maximum potentiation of the twitch.

6. It is concluded from these observations that f½ reflects diastolic Ca2+‐dependent myofilament interaction; the increase in the extent of this interaction by inotropic interventions that do not alter the affinity of the myofilaments for Ca2+ probably reflects an increase in diastolic myoplasmic [Ca2+], an optimal level of which is associated with maximal potentiation of twitch force; the difference in f½ in rat and cat muscles under a given set of in vitro conditions may be related to the marked species difference in the effectiveness of excitation—contraction coupling.
Changes in activity of vagal bronchopulmonary C fibres by chemical and physical stimuli in the cat.
Authors: Delpierre S , Grimaud C , Jammes Y , Mei N
Published: December 2014

1. In eighteen anaesthetized cats, action potentials in non‐myelinated vagal afferent neurones were recorded in the nodose ganglion by means of extracellular micro‐electrodes. 2. The pulmonary or bronchial origin of these C fibres was assessed in closed chest preparations by injecting phenyl diguanide into either the right atrium or the ascending aorta (bronchial circulation). This was confirmed in two animals by local mechanical stimulation. 3. Eighty per cent of bronchopulmonary C fibres increased their discharge frequency when the end‐tidal CO2 concentration (FA,CO2) increased from 0.02 to 0.10. Most of these C endings showed a maximal response when FA,CO2 reached 0.04. For the others a further increase in discharge occurred when CO2 concentration reached 0.08‐0.10. Continuous measurement of C fibre discharge frequency indicated that they detected preferentially changes in the inspired CO2 content, but adapted when a high CO2 level was maintained. Their activation by hypercapnia was followed by an increase in lung resistance. 4. Lowering the O2 content of the inspired gas had no effect on the spontaneous activity of bronchopulmonary C endings. 5. When the stroke volume of the pump was doubled, the spontaneous activity of bronchopulmonary C fibres decreased in intact chest preparations. Inflation of the lungs had the opposite effect after the chest was opened. In both cases hyperdeflation was a potent stimulus to these receptors. 6. In tracheotomized cats, the tracheal temperature was 28‐29 degrees C. When normal thermal conditions were restored in the tracheal lumen (33‐34 degrees C) the spontaneous discharge frequency of some bronchial C fibres was greatly increased. 7. It is concluded that the spontaneous activity of most of the bronchial or pulmonary C fibres was maximal when chemical and physical physiological conditions were restored in the lungs. It appears that changes in alveolar CO2 concentration constitute the usual stimulus for these fibres.
Changes in plasma noradrenaline and adrenaline associated with central and peripheral thermal stimuli in the pig.
Authors: Barrand M A , Dauncey M J , Ingram D L
Published: December 2014

1. The role of catecholamines in thermogenesis has been investigated in trained young pigs in various situations which increases heat production. Plasma noradrenaline and adrenaline concentrations were estimated by radioenzymic assay of samples taken from an indwelling jugular catheter to prevent disturbance and stress. 2. During 3 hr at ambient temperatures of between 25 and ‐5 degrees C, there was curvilinear increase in noradrenaline concentrations as temperature decreased, but adrenaline did not change. After 1‐3 days at 5 or 1 degrees C, the concentrations of both amines were similar to those found at thermal neutrality. 3. Cooling the cervical region of the spinal cord resulted in a large increase in plasma noradrenaline whereas local cooling of the hypothalamus was associated with a small increase in the hormone. When cooling either region of the central nervous system, plasma adrenaline concentrations did not change. 4. During exposure to 45 degrees C, rectal temperature increased to 43 degrees C. Concentrations of catecholamines remained low or declined until the rectal temperature was above 41.5 degrees C when the concentrations increased in most animals. 5. Induced physical activity lasting 40 min was associated with an increase in both noradrenaline and adrenaline concentrations. 6. Blood samples from the inferior vena cava, just cephalad to the outlet of the adrenal veins, had much higher concentrations of noradrenaline during cold exposure than those taken simultaneously from the jugular vein. Therefore, at least part of the increase in noradrenaline concentrations reported above may have been due to release of the hormone from the adrenal medulla. 7. It is concluded that during short‐term exposure to cold, and in exercise, there is a rapid catecholamine response, producing concentrations in the blood which could be high enough to stimulate thermogenesis. During longer‐term cold exposure, catecholamine output is low and other factors must be of greater importance in maintaining thermogenic processes. Further, catecholamine output may result from thermal stimuli not only from outside the external surface of the animal but also from within the central nervous system.
Membrane properties and selective connexions of identified leech neurones in culture
Authors: Fuchs Paul A. , Nicholls John G. , Ready Donald F.
Published: December 2014

1. Individual, identified neurones, dissected from the central nervous system of the leech and maintained in culture for several weeks, sprouted processes and formed synaptic connexions.

2. The action potentials of isolated touch (T), pressure (P), nociceptive (N) cells and Retzius cells resembled those of their counterparts in situ, enabling them to be recognized unambiguously. Their input resistances were approximately 4 times greater than those of corresponding cells within the animal. In T, P and N cells trains of impulses were followed by a pronounced after‐hyperpolarization, as in the animal.

3. In certain cells, notably the L motoneurones, membrane properties became altered in culture. The current—voltage relation showed novel rectification and action potentials became much larger.

4. Numerous neurites often extended for hundreds of micrometres from isolated neurones and ended in typical growth cones. Electron micrographs revealed that many fine axons were braided together to form thicker fascicles. Frequently, the processes were orientated between two neighbouring cells rather than at random. The fine structure of the cytoplasm, nucleus and organelles in cultured cells resembled those of their counterparts in situ. The glial cell that normally surrounds the neurones was, however, absent.

5. Pairs of Retzius cells in culture usually became coupled electrically after about 6 days. Similarly L motoneurones became coupled in vitro. These junctions allowed current to pass in both directions and resembled those seen in the animal.

6. Selective connexions were made by certain types of cells. Thus, P sensory neurones did not become coupled with Retzius cells but did develop electrical connexions with L motoneurones, as in the animal.

7. Novel synaptic interactions not obvious in the animal could appear in culture. Retzius and L cells became electrically coupled and, in some instances where electrical coupling between Retzius cells failed to develop, chemically mediated inhibitory potentials became apparent.

8. Isolated, identified leech neurones not only survive but regenerate processes and are capable of forming selective connexions in culture. The ability to define interactions between isolated pairs of cells offers the opportunity to explore in detail problems relating to synapse formation and cell—cell recognition.
The ionic mechanism of intracellular pH regulation in crayfish neurones.
Authors: Moody W J
Published: December 2014

1. Intracellular pH (pHi) regulation in crayfish neurones was studied using pH‐, Na+‐, and Cl‐ sensitive micro‐electrodes. Neuronal pH regulation has previously been studied only in molluscs. 2. The average resting pHi of crayfish neurones was 7.12 +/‐ 0.09, which is 1 pH unit more alkaline than that predicted were H+ ions distributed in equilibrium with the membrane potential. 3. When the cytoplasm was acidified (by NH4Cl loading, CO2 application, or HCl injection), pHi recovered towards its resting value. 4. Removal of Na+ from the external solution inhibited pHi recovery from an acid load by more than 90%. pHi recovery resumed immediately when external Na+ was reintroduced. 5. The resting intracellular Na+ concentration ([Na+]i) of crayfish neurones was 15‐25 mM. During pHi recovery from an acid load, [Na+]i increased by 10‐50 mM. 6. Reducing the external HCO3(‐) concentration from 5 mM to 0 mM slowed pHi recovery by an average of about 45%. This slowing was appreciable even in cells in which Na+ removal almost totally blocked pHi recovery. 7. The resting intracellular Cl‐ concentration ([Cl‐]i) was 30‐40 mM, indicating that these cells actively accumulate Cl‐. During pHi recovery from an acid load, [Cl‐]i decreased by 3‐5 mM. 8. In the presence of the anion exchange inhibitor SITS (4‐acetamide‐4'‐isothiocyanostilbene‐2,2'‐disulphonic acid), pHi recovery was slowed to the rate which was normally seen in HCO3(‐)‐free Ringer solution. SITS abolished the dependence of pHi recovery on the external HCO3(‐) concentration. 9. It is concluded that pHi regulation in crayfish neurones involves two separate mechanisms: a Na+‐dependent, HCO3(‐)‐independent acid extrusion process, and a Cl‐‐‐HCO3(‐) exchange which is probably also Na+‐dependent.
Patterns of recurrent excitation and mutual inhibition of cat Renshaw cells.
Authors: Ryall R W
Published: December 2014

1. Patterns of convergent excitation and mutual inhibition of Renshaw cells to antidromic volleys in motor axons were investigated in cats anaesthetized with chloralose. 2. There were widely varying patterns of excitatory convergence onto individual Renshaw cells, but grouping the cells into different populations revealed the underlying positive and negative correlations between inputs from different motor nerves. 3. The greatest excitatory convergence was seen between axons supplying functionally synergistic muscles. 4. Mutual inhibition between Renshaw cell populations was most evident between antagonist motoneurones and so was inversely related to the excitatory inputs. 5. These results are discussed in relation to the control of recurrent inhibitory phenomena mediated by renshaw cells.