bluuebunny/crossref_metadata_2025_split huggingface dataset:
The initiation of platelet thrombi in normal venules and its acceleration by histamine
Authors: Begent Nicola A. , Born G. V. R. , Sharp D. E. 
Published: December 2014

1. In cheek pouch preparations of anaesthetized hamsters, platelet thrombi or ‘white bodies’ were produced in venules by the micro‐ionto‐phoretic application of adenosine diphosphate (ADP). Currents of 10–400nA were passed through micropipettes containing 10 m
M‐ADP, the tips of which were less than 5 μ from the outer wall of the venule. The effect was quantitated by determining the time between starting the currents and the first appearance of platelets adhering inside the venule opposite the tip of the micropipette.2. Repeated applications of ADP to the same site on a venule caused the appearance of white bodies after intervals which were almost constant for up to 3 hr.3. The time to first appearance of a white body was inversely related to the iontophoretic current between about 10 and 200 nA. Currents smaller than 10 nA had no effect on the platelets. With currents of 200 nA or more the time remained at a minimum of less than 20 sec.4. With currents of about 300 nA the minimum time increased little as the pipette tip was withdrawn up to 20 μ from the venule; with greater distances the time increased progressively.5. Histamine caused gaps to appear between endothelial cells in cheek pouch venules. Histamine at a concentration of 10 m
M in micropipettes was applied iontophoretically by currents of 300 nA to venules at the same sites as ADP. Histamine alone had no effect on circulating platelets. When applied before and together with ADP, histamine decreased the time to first appearance of white bodies by up to 40% below that determined with ADP alone. Iontophoretically applied histamine did not alter the mean blood flow velocity in the venules.6. After stopping the application of histamine, the time to first appearance of white bodies produced by ADP increased again in about 5 min to the control values.7. Bradykinin, which does not cause endothelial gaps in cheek pouch venules, did not accelerate the induction of white bodies like histamine.8. There were no microscopic abnormalities in venules in which white bodies had formed. Venules exposed to histamine accumulated circulating carbon particles in discrete wall areas.9. It is concluded that adhering white bodies can be induced repeatedly in normal venules by direct action of externally applied ADP on circulating platelets and that the accelerating effect of histamine on white body formation is due to the separation of endothelial cells which accelerates the inward diffusion of ADP.
Release of 5‐hydroxytryptamine from caudate nucleus and septum
Authors: Holman R. B. , Vogt Marthe 
Published: December 2014

1. The anterior horn of one lateral ventricle was perfused in anaesthetized cats treated with inhibitors of monoamine oxidase, and the effluent was tested for 5‐hydroxytryptamine (5‐HT).2. The basal release of 5‐HT varied from 0·25 to 4 ng in 25 min, and was usually about 1 ng.3. The basal release rose and fell with body temperature.4. Electrical stimulation for 15 min of the nucleus linearis intermedius or of the nucleus linearis rostralis caused a release of 5‐HT which rarely outlasted the collection period of 25 min.5. Low frequencies (0·5/sec) were, per stimulus, more effective than high frequencies in releasing 5‐HT. Over a 15 min period of stimulation, however, the highest total yield was at 20/sec; it fell abruptly at still greater frequencies.6. No release was obtained if the stimulating electrode was positioned in a variety of brain structures outside the two linear nuclei.7. The experiments indicate that 5‐HT acts as a transmitter of impulses in neurones originating in the linear nuclei and terminating in caudate nucleus and septum.
The functional organization of the isthmo‐optic nucleus in the pigeon
Authors: Holden A. L. , Powell T. P. S. 
Published: December 2014

1. Extracellular single unit records were taken from the isthmo‐optic nucleus of the pigeon, locating the nucleus by the antidromic field potential resulting from electrical stimulation of the isthmo‐optic tract.2. Visual receptive fields were investigated for 248 units, and were classed into three types: directionally selective, directionally non‐selective, and posterior minimum. They ranged from 3 to 10° in extent.3. The topographical representation of the visual field in the nucleus was investigated by histological verification of electrode tracks, and a correlation with the receptive field sequences. Vertical descent through the nucleus resulted in an upwards progression of receptive field locations. Lateromedial passage through the nucleus resulted in a forwards progression of receptive field locations.4. The representation of the lower visual field is greater than that of the superior visual field: that for the central parts of the inferior field is greater than that for the periphery, and the representation of the anterior inferior quadrant is greater than that of the posterior inferior quadrant.
Cyclic adenosine 3′,5′‐monophosphate concentration in the pancreas following stimulation by secretin, cholecystokinin‐pancreozymin and acetylcholine*
Authors: Case R. M. , Johnson M. , Scratcherd T. , Sherratt H. S. A. 
Published: December 2014

1. Following an
I.V. injection of secretin into anaesthetized cats, the pancreatic cyclic AMP concentration rose within 30 sec and reached near‐maximal values within 1 min. Pancreatic secretion began only after 45 sec. As secretion declined, the cyclic AMP concentration also fell. However, after 40 min, when secretion had ceased, the concentration again rose, reaching a maximum after about 80 min and returned to basal values within 140 min.2. During secretin infusion the pattern of cyclic AMP changes was the same, except that the initial rise was maintained as long as secretin was infused.3. Following either pancreozymin or acetylcholine, alone or super‐imposed on secretin stimulation, similar changes in cyclic AMP concentration were observed. However, the initial rise lasted only 30 sec, basal concentrations being approached within 1 min, and was accompanied by enzyme secretion. The concentration of cyclic AMP subsequently rose and fell again, in the absence of enzyme secretion, exactly as after secretin stimulation.4. Similar observations were made using an isolated, saline‐perfused preparation of the cat's pancreas.5. By using very low doses of pancreozymin it was possible to observe the first rise in cyclic AMP concentration in the absence of enzyme secretion. Similarly atropine, while blocking enzyme secretion, did not affect the rise in cyclic AMP concentration after acetylcholine. The second increase in concentration was never associated with secretion (it may have been connected with the synthesis of exportable enzymes by the gland).6. While these observations suggest that cyclic AMP may be involved in the response of the pancreas to secretin, pancreozymin and acetylcholine, no simple relation exists between cyclic AMP concentration and secretion.
Quantal components of the inhibitory synaptic potential in spinal motoneurones of the cat
Authors: Kuno M. , Weakly J. N. 
Published: December 2014

1. Monosynaptic i.p.s.p.s were produced in spinal motoneurones of the cat by stimulation of a pool of interneurones following chronic degeneration of descending tracts and primary afferent fibres in the lumbosacral cord.2. Monosynaptic i.p.s.p.s so evoked by supramaximal stimuli often showed a fluctuation in amplitude with occasional failures of response.3. When two successive stimuli were applied at a short interval, the mean amplitude of the second i.p.s.p.s was greater than that of the first. This facilitation was associated with a decrease in the number of failures, a decrease in the coefficient of variation of the amplitude distribution and an increase in the probability of occurrences of large i.p.s.p.s.4. A statistical analysis of the i.p.s.p. amplitude fluctuation showed that the monosynaptic i.p.s.p. is composed of discrete unit potentials evoked with a certain probability in a manner described by a binomial law.5. The application of strychnine decreased the mean amplitude of i.p.s.p.s with little change in the coefficient of variation of the i.p.s.p. amplitude distribution.6. It is concluded that the release of inhibitory transmitter occurs in quantal steps and that strychnine blocks primarily the post‐synaptic receptors for the inhibitory transmitter.
An attempt at an analysis of the factors determining the time course of the end‐plate current
Authors: Kordaš M. , Gabrovec I. , Kordaš M. , Popovič B. 
Published: December 2014

1. An attempt was made to analyse the factors which might determine the time course of the falling phase of the end‐plate current.2. The end‐plate current was measured by ‘clamping’ the membrane potential during neuromuscular transmission.3. The falling phase of the end‐plate current was found to consist of a non‐exponential, and an exponential portion, the duration of both of which varies under different experimental conditions.4. The results suggest that the rate constants determining the dissociation of the receptor—mediator complex seem greatly to influence the time course of the end‐plate current.
The influence of deep body and skin temperatures on thermoregulatory responses to heating of the scrotum in pigs
Authors: Ingram D. L. , Legge K. F. 
Published: December 2014

1. The temperature on the surface of the pig's scrotum was increased by circulating water through a pad held over the scrotal surface while the animal was lightly restrained.2. At an ambient temperature of 25° C there was no change in respiratory frequency even when the scrotum was heated to 42° C, but peripheral blood flow did increase and body temperature fell. At 30° C ambient temperature, respiratory frequency increased when the scrotum was warmed to 42° C. At an ambient temperature of 32° C, the frequency increased at a scrotal temperature of 40° C and was even higher when the scrotum was 42° C, but body temperature did not fall.3. At a constant ambient temperature the effect on respiratory frequency of heating the scrotum to a given temperature depended on the skin temperature of the trunk which was modified by means of a coat through which water was circulated.4. In a cold environment, heating the scrotum was accompanied by a fall in body temperature, the arrest of shivering and a decline in oxygen consumption.5. Cooling a thermode in the hypothalamus or over the spinal cord inhibited the increase in respiratory frequency and peripheral blood flow caused by heating the scrotum. Warming either thermode potentiates the effect of heating the scrotum.
Changes in axon light scattering that accompany the action potential: current‐dependent components
Authors: Cohen L. B. , Keynes R. D. , Landowne D. 
Published: December 2014

1. When light scattering was measured during hyperpolarizing and depolarizing voltage‐clamp steps, relatively large scattering changes were found during the depolarizing steps. These large changes were found to depend on the time integral of the ionic current and not on the changes in conductance or potential.2. The current‐dependent changes were examined at several scattering angles, and three distinct time courses were found. At 30–120°, the main change occurred after the current when steps of 2–5 msec duration were used. This change was called I‐90°. At 15–30°, the change occurred with the same time course as the time integral of the current. This change was called I‐25°. At 5–15° the scattering change occurred with a time course intermediate between that of I‐90° and I‐25°. This change was called I‐10°.3. In all experiments, outward potassium and outward sodium currents led to similar light scattering changes indicating that specific effects of the cation carrying the current across the membrane were not involved.4. The size of I‐90° was reduced by 29% when an isethionate artificial sea water was substituted for the normal chloride artificial sea water. This reduction equalled the reduction predicted for a transport number effect at the membrane‐solution interface. The time course of I‐90° was similar to the predicted time course for a volume change in the periaxonal space, and such volume changes were tentatively identified as the origin of I‐90°.5. Because of difficulties in measuring the time course of I‐25°, it was not possible to distinguish between a water of hydration effect and a transport number effect as the cause of this change. Similarly, the origins of I‐10° were not identified. Only I‐10° was altered in size and time course when the external refractive index was increased with bovine albumin.6. When the scattering changes during the action potential were examined in light of the voltage‐clamp experiments, we concluded that the forward‐angle change was potential‐dependent and that the long‐lasting change at right angles probably represented a swelling of the periaxonal space resulting from the fact that chloride carried a significant fraction of the outward current during the action potential.
Ionic mechanism of a two‐component cholinergic inhibition in Aplysia neurones
Authors: Kehoe Jacsue 
Published: December 2014

1. A two‐component inhibition, consisting of a rapid and slow i.p.s.p., has been observed in the medial cells of the pleural ganglion of Aplysia. Each i.p.s.p. has been shown to be mediated by a distinct cholinergic receptor. The ionic mechanisms of the two components of the inhibitory response (whether elicited synaptically or by ACh injection) are analysed in this paper.2. The inversion potential (typically −60 mV) of the rapid i.p.s.p. and of the rapid response to ACh injection is selectively altered by an intracellular injection of chloride or by partial substitution of the external chloride by impermeant anions. The shift caused by this last procedure is similar to that predicted for the chloride equilibrium potential (ECl) by the Nernst equation.3. The slow i.p.s.p. and the slow response to ACh injection (both of which invert around −80 mV) are insensitive to changes in either internal or external chloride concentrations; on the contrary, with alterations of the concentration of potassium in the external medium, the inversion potential of the slow responses is altered in a way similar to that expected for the potassium equilibrium potential (EK).4. It is concluded that the rapid i.p.s.p. and the corresponding ACh potential are due to a change in chloride permeability of the post‐synaptic membrane, whereas the slow responses are due to a selective change in potassium permeability.5. Additional data suggest that the fast, ‘chloride’ channel is impermeable to sulphate and methylsulphate, but slightly permeable to propionate and isethionate. The slow, ‘potassium’ channel is impermeable to caesium ions, whereas its permeability to rubidium ions is half that to potassium.6. The potassium permeability of both the non‐synaptic and synaptic membrane is markedly reduced by an intracellular injection of either tetraethylammonium (TEA) or caesium. These ions not only block the cholinergic potassium currents (whether inward or outward) but likewise block the potassium currents activated in the same cells by an iontophoretic injection of dopamine.7. The potassium dependent synaptic potentials are also selectively affected by manipulations known to block the electrogenic sodium pump. In the presence of ouabain or in sea water in which sodium has been replaced by lithium, there is an apparent reduction of these potentials which was shown to be simply a reflexion of the movement of EK towards a less polarized level. This shift in inversion potential was not seen for the potassium dependent response to ACh iontophoretic injection. These results are interpreted in terms of accumulation of potassium ions assumed to occur in the extracellular spaces of the neuropile, but not in the thoroughly dissected somatic region.8. Cooling was shown to eliminate, selectively, the synaptic and ACh potential changes caused by an increase in potassium permeability.
Separation of the pace‐maker and plateau components of delayed rectification in cardiac Purkinje fibres
Authors: Hauswirth O. , Noble D. , Tsien R. W. 
Published: December 2014

1. Experiments on sheep Purkinje fibres were designed to determine whether the current mechanisms responsible for delayed rectification at the pace‐maker (negative to −50 mV) and plateau (positive to −50 mV) ranges of potential are kinetically separable and independent.2. Hyperpolarizations from the plateau range were shown to produce decay of a single component of outward current within the plateau range, but two components were evident when the hyperpolarizations entered the pace‐maker range.3. The time courses of recovery of the two components were too similar at −25 mV to allow temporal resolution at this potential. Clear temporal resolution was, however, possible at potentials between −55 and −95 mV. An indirect method of resolving the two components at −25 mV was used.4. The kinetic properties of the two components correspond to those previously described for the pace‐maker potassium current, iK2, and the outward plateau current, ix1 (Noble & Tsien, 1968, 1969a).5. The instantaneous (fully activated) current—voltage relation for iK2 was reconstructed from the analysed current records. It was found that this relation shows a negative slope conductance at all potentials positive to −75 mV and that the current tends towards zero at zero membrane potential.6. The results are compared with those predicted by two reaction models of the iK2 and ix1 mechanisms. It is concluded that iK2 and ix1 are kinetically separable but that it is not possible with present techniques to decide whether they are controlled by the same or completely independent membrane structures. It is also shown that the instantaneous current—voltage relation calculated for iK2 does not depend on whether the controlling mechanisms are assumed to be independent or linked.
Synaptic potentials in nerve cells of the stellate ganglion of the squid
Authors: Miledi R. 
Published: December 2014

1. Intracellular recordings were made from nerve cells in the stellate ganglion of the squid.2. Stimulation of the preganglionic nerve evoked excitatory or inhibitory synaptic potentials, or a combination of both. Antidromic stimulation of the stellar nerves also evoked excitatory and inhibitory potentials in the cells. With both types of stimulation the synaptic potentials were built up of contributions from several axons indicating considerable convergence of excitatory and inhibitory inputs on the cells.3. Inhibitory, as well as excitatory, miniature synaptic potentials were recorded from the cells even after impulse activity had been blocked by tetrodotoxin.4. Glutamate applied iontophoretically to some cells produced a depolarization of their membranes. In other cases glutamate evoked a hyperpolarizing potential. Application of glutamate caused a decrease in the amplitude of excitatory synaptic potentials.
The resting potential of moth muscle fibre
Authors: Rheuben Mary B. 
Published: December 2014

1. The membrane of the moth muscle fibre was tested for resting permeability to various ions: it is not permeable to Mg2+ or Ca2+; it is slightly permeable to Na+ and NH4+; it is appreciably permeable to Cl−, but Cl− is passively distributed; it is apparently permeable to H+ but effects of HCO3− are not ruled out; and it is primarily permeable to K+.2. Measurement of the internal K+ activity showed that EK is less negative than the resting potential.3. In the presence of DNP, or under anoxia, the membrane potential approaches, EK; there is a small concomitant decrease in effective membrane resistance.4. An increase in external Ca2+ concentration is accompanied by increased effective membrane resistance and an increase in amplitude of the negative resting potential.5. Cooling the membrane (below room temperature) decreased the amplitude of the resting potential by 4–16 mV per 10° C, and was accompanied by a large increase in effective membrane resistance.6. The experimental results most readily fit the hypothesis that the resting potential of the moth muscle fibre, although the membrane is highly permeable to K+, Cl− and apparently to H+, is primarily maintained by an electrogenic transport process which generates an ionic current across the membrane. The possibility that the concentration gradient of H+ ions is metabolically maintained at a level sufficient to explain the resting potential was considered to be unlikely but could not be directly excluded.
Effect of renal nerve stimulation, renal blood flow and adrenergic blockade on plasma renin activity in the cat
Authors: Coote J. H. , Johns E. J. , Macleod Valerie H. , Singer Bertha 
Published: December 2014

1. The effect of electrical stimulation of the distal cut ends of the renal nerves of unilaterally nephrectomized, anaesthetized cats was studied. Using stimulation parameters of 15 pulses per second (pps), 15 V and 0·2 msec duration, there was an immediate sharp drop in renal blood flow, as determined by an electromagnetic flowmeter, which was maintained for about 2 min. Flow gradually returned to control values over approximately the next 10 min in spite of continued stimulation for up to 30 min.2. Plasma renin activity (PRA) increased markedly after 10 min of stimulation but 20 min later fell towards pre‐stimulation values whether stimulation was maintained or not.3. Phentolamine, an α‐adrenergic‐receptor antagonist, abolished both the blood flow and PRA responses to a 10 min period of renal nerve stimulation.4. When the renal artery was constricted in order to produce blood flow changes similar to those found with renal nerve stimulation, the rise in PRA was similar to that observed with renal stimulation.5. In phentolamine‐blocked animals, renal artery constriction, as described, produced the same effect on PRA as was observed with renal nerve stimulation.6. Propranolol, a β‐adrenergic‐receptor antagonist, did not block the blood flow response to renal nerve stimulation, but did block the rise in PRA normally associated with renal nerve stimulation.7. It is suggested that the effect of renal nerve stimulation on PRA is mediated, primarily, by changes in renal blood flow and that one of the steps leading to renin release following stimulation is sensitive to propranolol. This step must be distal to the effect on vascular smooth muscle.
Reflex firing in the lumbar sympathetic outflow to activation of vesical afferent fibres*
Authors: de Groat William C. , Lalley Peter M. 
Published: December 2014

1. Activation of vesical afferent fibres in the Aγδ range by electrical stimulation of the pelvic nerve or by bladder distension elicited reflex firing in hypogastric nerves and in preganglionic nerves to the inferior mesenteric ganglion.2. The multisynaptic reflex was present in cats with an intact spinal cord and in acute and chronic spinal animals (transections at T10—T12). The reflex pathway was partially crossed in the sacral cord, and in the periphery at the level of the inferior mesenteric ganglia. In contrast, an inhibitory response to raised intravesical pressure was mediated by a supraspinal inhibitory mechanism which was activated in parallel with the micturition reflex.3. Since enhancement as well as depression of sympathetic firing accompanied reflex micturition, it is concluded that at least two distinct populations of lumbar preganglionic neurones are responsive to vesical afferent activity: one population being excited, the other depressed, during micturition. The latter population may be involved in an inhibitory feed‐back mechanism on to the bladder.