bluuebunny/crossref_metadata_2025_split huggingface dataset:
The action of nerveside, a peptide extracted from brain, on myenteric ganglia in Auerbach's plexus
Authors: Soh N. M. , Toh C. C. 
Published: December 2014

1. In the rabbit jejunum nerveside causes alternating contractions of the longitudinal and circular muscles, which are similar to the peristaltic reflex produced by distension of the gut. These effects are abolished by dibucaine (Nupercaine) and tetrodotoxin. The site of action is located in Auerbach's plexus.2. Circular muscle contractions due to nerveside are blocked by hexamethonium, nicotine, morphine, atropine and hyoscine. There is no circular response to nerveside after removal of Auerbach's plexus. It is suggested that nerveside acts by stimulating presynaptic nerve terminals which are cholinergic and that the circular muscle is innervated by cholinergic nerve fibres.3. Longitudinal muscle contractions due to nerveside are not affected by hexamethonium but can be blocked by paralysis of myenteric ganglia with nicotine. They are not abolished by morphine or by cholinolytic drugs. It is suggested that nerveside acts by stimulating either receptors insensitive to acetylcholine in ganglion cells or non‐cholinergic presynaptic nerve terminals. It is further suggested that the longitudinal muscle of the rabbit gut is supplied by non‐cholinergic as well as cholinergic nerve fibres.
Geometrical illusions and the response of neurones in the cat's visual cortex to angle patterns
Authors: Burns B. Delisle , Pritchard Roy 
Published: December 2014

1. This report describes the responses of thirty‐six single neurones in the primary visual area of the cat's neurologically isolated and unanaesthetized forebrain, to movements of thin white lines across the visual field. The experiments were designed to record the effects upon the response to a single test line of an added line, which was either parallel to the test line or joined it, making an angle‐pattern of 30°. Unit responses were measured in terms of the peak probability of firing derived from a post‐stimulus histogram.2. All of the cortical neurones tested exhibited a preferred orientation for stimulation by the test line, i.e. an orientation of the line which produced a maximal response when the line passed through the centre of the unit's receptive field.3. There was no evidence that the orientation of a single test line preferred by cortical neurones was different from that preferred by the same cell when excited by an angle pattern, one arm of which was the original test line.4. The position of a test line (with preferred orientation) in the visual field that produced a maximal response from cortical neurones, was not always the same as the position for maximal response, when a second line was added to make either an angle pattern or to make a pattern of two parallel lines.5. Where the two lines of these patterns were close together and separated by less than the radius of the receptive field, the position for maximal response to the test line was shifted towards the added line. Where the two lines were further apart than this but separated by less than a receptive field diameter, the optimal position for the test line was displaced away from the added line.6. Some evidence was found of a lateral inhibition in the visual system, sufficient to account for the displacements described in paragraphs 4 and 5 above.7. It is concluded that the tip of an angle pattern of 30° produces a distorted cortical image within the primary visual area.8. This neural distortion of sensory information seems adequate to explain the well known illusions of orientation that are associated with human perception of patterns containing acute angles.
The mechanical and thermal properties of frog slow muscle fibres
Authors: Floyd K. , Smith I. C. H. 
Published: December 2014

1. A study has been made of the mechanical behaviour and the heat production of frog slow muscle fibres in iliofibularis nerve—muscle preparations at 20° C.2. The slow fibre isometric tension and its rate of development increase with stimulation frequency, the increases beyond 30 Hz being relatively small. Relaxation rate also increases with stimulation frequency. The tension—length curve and maximum isometric tension (250 mN.mm−2) are similar to those of twitch fibres. The maximum shortening velocity is estimated to be 0·11 tonus bundle lengths per second.3. For contractions up to 60 sec at 30–50 Hz the slow fibre heat rate is steady at 6 mJ.g−1.sec−1. Slow fibres produce aerobic recovery heat with a time course similar to that of twitch fibres.4. The accuracy of the results is discussed, and a comparison is made with the properties of twitch fibres. It is concluded that the tension‐producing reactions are thirty times slower in the slow fibres.
The functional organization of the parasympathetic secretory innervation of the submandibular gland
Authors: Ekström J. , Emmelin N. 
Published: December 2014

1. In cats the hypoglossal and chorda‐lingual nerves were cut and their central ends sewn to the peripheral end of the latter nerve. At monthly intervals the sensitivity of the submandibular gland to a secretory agent was then estimated.2 When the supersensitivity resulting from the decentralization of the gland had been lowered to a constant level acute experiments were made. Electrical stimulation of both nerves caused secretion, which was abolished by ganglion blocking drugs and atropine.3. Simultaneous stimulation of the nerves at frequencies subliminal for each nerve did not cause any secretion.4. Stimulation of one nerve at a subliminal frequency did not increase a flow of saliva evoked by stimulation of the other nerve. However, as soon as the secretory threshold was reached, the flow was markedly accelerated, provided it was submaximal.5. In many cases stimulation of the regenerated chorda fibres at a high frequency caused a flow corresponding to the maximal secretory capacity of the gland. In some experiments this was true for the hypoglossal fibres also.6. The functional organization of the parasympathetic secretory innervation of the submandibular gland of the cat is discussed in the light of these observations.
The inotropic and chronotropic effects of catecholamines on the dog heart
Authors: Furnival C. M. , Linden R. J. , Snow H. M. 
Published: December 2014

1. The chronotropic and inotropic responses of the denervated dog heart to intravenous infusions of noradrenaline, adrenaline and isoprenaline were studied.2. The maximum rate of rise of pressure in the left ventricle of the heart, (dP/dt max) measured at a constant heart rate and mean systemic arterial pressure during each series of infusions, was used as an index of inotropic changes (Furnival, Linden & Snow, 1970).3. The order of potency of the catecholamines in producing both chronotropic and inotropic effects was isoprenaline > adrenaline > noradrenaline.4. For the same increase in heart rate produced by an infusion of a catecholamine, noradrenaline caused a greater inotropic effect than adrenaline, which in turn caused a greater increase than isoprenaline.5. The chronotropic and inotropic effects of noradrenaline were potentiated by an intravenous injection of cocaine HCl (5 mg/kg), whereas those of isoprenaline were unchanged.6. The relative difference between the responses to noradrenaline and isoprenaline was abolished by an intravenous injection of cocaine HCl.7. It is concluded that the different relative chronotropic and inotropic effects of isoprenaline and noradrenaline are due to the greater uptake of noradrenaline by sympathetic nerve endings in the sinu‐atrial node than in the muscle of the left ventricle.
Effect of mitosis inhibitors on blood platelet microtubules and aggregation
Authors: Sneddon John M. 
Published: December 2014

1. An inhibitory action of the mitosis inhibitors colchicine, colcemid and vinblastine on blood platelet aggregation has been demonstrated.2. The inhibitory action of low concentrations of these drugs was surmountable by increasing the concentration of the aggregating agents adenosine diphosphate (ADP) or thrombin. High concentrations completely inhibited aggregation.3. The presence of a circumferential bundle of microtubules has been demonstrated in rabbit platelets.4. After exposure to aggregating doses of ADP and thrombin the microtubules move to the centre of the cell, ‘trapping’ the platelet intracellular organelles in a relatively clear cytoplasm.5. Concentrations of the antimitotic agents which reduce platelet aggregation depolymerize the platelet microtubules and prevent the rearrangement of the platelet organelles during aggregation.6. It is suggested that the microtubules are not essential for platelet aggregation but are intimately involved in the movement of intracellular granules. This may be a preliminary stage in the eventual discharge of the granules during the platelet ‘release reaction’.
The responses of aortic arch and right subclavian baroreceptors to changes of non‐pulsatile pressure and their modification by hypothermia
Authors: James Jennifer E. Angell 
Published: December 2014

1. A method is described for isolation of the aortic arch and right subclavian—carotid angle in situ in the rabbit and perfusion with Krebs—Henseleit solution or blood under controlled conditions of pressure and temperature.2. The characteristics of the baroreceptors of the aortic arch and right subclavian—carotid angle were studied by recording from single or few‐fibre preparations of the left and right aortic nerves respectively. Curbes were plotted to show the relationship between the frequency of baroreceptor impulse activity and intra‐aortic pressure during non‐pulsatile perfusion under steady‐state conditions.3. The aortic arch and right subclavian—carotid angle baroreceptors were found to have similar characteristics. Three types of response of the baroreceptors at the threshold pressure to a steady intra‐aortic pressure are described.4. Increasing the intra‐aortic pressure increased the frequency of impulses in fibres previously active and caused recruitment of other fibres in multi‐fibre preparations. The relationship was linear at low pressures and a point of inflexion occurred at higher pressures in the majority of fibres.5. Lowering the temperature of the perfusate reduced the impulse frequency at any given pressure.6. The curves obtained during stepwise increases and decreases in intra‐aortic arch pressure were dissimilar, particularly at the lower end of the pressure range. This phenomenon is probably due to properties of the arterial wall.7. When the aortic arch preparation was excised, changes occurred in the shape of the impulse frequency—pressure curves from baroreceptors in both areas. The point of inflexion was elevated and a higher percentage of fibres failed to reach a point of inflexion in the pressure range studied.
The effects of ethacrynic acid and other sulphydryl reagents on sodium fluxes in frog muscle
Authors: Erlij D. , Leblanc G. 
Published: December 2014

1. Ethacrynic acid (2 m
M) increased the sodium efflux from freshly dissected frog sartorius muscles. This increase was not observed in muscles previously treated with strophanthidin.2. In strophanthidin‐treated muscles, the addition of ethacrynic acid (2 m
M) caused a reduction of sodium efflux. The value of efflux reached in these muscles is similar to that observed in muscles immersed in sodium‐free solutions containing strophanthidin.3. Ethacrynic acid reduced sodium influx into strophanthidin‐treated muscles. Potassium influx was not affected by this substance. These findings suggest that the inhibitor blocks an exchange of sodium for sodium.4. The increase in sodium efflux caused by ethacrynic acid did not result from depolarization nor from an increase in [Na]i.5. Ethacrynic acid caused only a reduction of sodium efflux in muscles previously loaded with sodium by prolonged immersion in potassium‐free solutions at low temperatures.6. A derivative of ethacrynic acid that lacks the ability to combine with sulphydryl (SH) groups did not reduce sodium efflux from muscles treated with strophanthidin.7. Para‐chloromercuribenzoic acid (PCMB) reduced sodium efflux from control and strophanthidin‐treated muscles. This reduction seems to be restricted to the sodium dependent component of the efflux.8. The inhibition of the sodium‐dependent component of sodium efflux caused by ethacrynic acid and PCMB appears to have a similar mechanism, namely, the combination with SH groups.
Ionic dependence of protein transport across the new‐born pig intestine
Authors: Smith M. W. 
Published: December 2014

1. The everted small intestine of the new‐born pig transports albumin to its serosal surface at rates which depend on the ionic composition of the bathing medium.2. Albumin transport takes place most rapidly at sodium and potassium concentrations of 120 and 6 m
M respectively. Increasing the concentration of sodium or potassium, or decreasing the concentration of sodium, reduces the net transfer of albumin.3. Albumin can increase the serosal transfer of sodium, potassium and water. The calculated ionic composition of fluid transported in the presence of albumin closely resembles that presented to the mucosal surface over a wide range of sodium and potassium concentrations.4. Lowering the concentration of sodium reduces water transfer but only if albumin is present in the mucosal medium. Albumin‐stimulated water transfer is only seen when the external concentration of sodium is high.5. Raising the concentration of potassium reduces water transport, whether or not albumin is present, but this reduction is too small to account for the inhibitory effect of potassium on albumin transport.6. The mutual interaction that exists between the transport of albumin and sodium is probably responsible for the increased potassium transport seen at low external concentrations of potassium. Higher concentrations of potassium appear directly to inhibit the interaction between the transport of sodium and albumin.
Membrane properties of the smooth‐muscle fibres of the guinea‐pig portal vein
Authors: Ito Y. , Kuriyama H. 
Published: December 2014

The membrane activities and the various characteristic constants of the smooth‐muscle membrane of the guinea‐pig portal vein were investigated with the micro‐electrode technique.1. The mean membrane potential was −37 mV. Spontaneous discharges appeared as regular bursts of short trains of spikes alternating with silent periods, as a mixture of single spikes and bursts of spikes appearing continuously, or as regular spikes with low frequency.2. Spontaneous spikes with overshoot were frequently observed. The maximum rate of rise of the spike was 3·7 V/sec. The shapes of the spikes were classified into three different types, i.e. pace‐maker type of spike, monophasic spike and spike with a hump during the falling phase.3. Tetrodotoxin (10−5 g/ml.) did not influence the patterns of the spontaneous train discharges nor the shape of the spike.4. Extracellularly applied outward current elicited spikes which were either monophasic or had a hump on the falling phase. Inward current elicited break excitation of the spike.5. Current—voltage relations, produced by application of inward current pulses to the tissue and measured at various distances from the stimulating partition, were linear.6. The smooth‐muscle membrane of portal vein showed cable‐like properties. The mean space constant of the membrane was 0·52 mm; the mean time constant of the membrane calculated from the electrotonic potential was 330 msec.7. Conduction velocity of the spike measured by insertion of two micro‐electrodes was 0·58 cm/sec.8. The time constant of the foot of the propagated spike was 27 msec. The time constant of the membrane calculated from the time constant of the foot of the spike and the conduction velocity was 310 msec.9. The membrane properties of longitudinal smooth muscle of the portal vein were discussed in comparison with other veins and various visceral smooth muscles.
The effect of potassium and chloride ions on the volume and membrane potential of single barnacle muscle cells
Authors: Mobley Bert A. , Page Ernest 
Published: December 2014

1. In single barnacle skeletal muscle cells cell diameter has been measured as a function of external osmolality, and cell diameter and membrane potential have been measured during changes of external K and Cl concentrations ([K]o and [Cl]o) like those described in frog muscle by Hodgkin & Horowicz (1959). The diameter was monitored microscopically with a precision of 0·2–0·4% (
S.D.). [K]o was varied from 1 to 18 m
M, a range of concentrations which does not cause contracture.2. At pH 8·0 the Cl permeability was so low that net KCl and water movements were absent. Such net movements were present at pH 4·5, corresponding to a change in the ratio (Cl conductance/K conductance) from approximately 1/12 at pH 8·0 to 1/2 at pH 4·5.3. Characteristically long time constants were observed for membrane potential responses to a change in [K]o and/or [Cl]o, even at constant [K]o.[Cl]o. This phenomenon is attributed to a delayed equilibration by diffusion within the system of sarcolemmal invaginations and T‐tubules. The delay in the response was increased by introducing polyvinylpyrrolidone (PVP) into this system, presumably because PVP raises intratubular viscosity.4. At pH 4·5 anomalous rectification for net movements of K was demonstrated by measurements of cell diameter and of membrane potential.
The isoenzymes of carbonic anhydrase: tissue, subcellular distribution and functional significance, with particular reference to the intestinal tract
Authors: Carter M. J. , Parsons D. S. 
Published: December 2014

1. The total carbonic anhydrase activity in some guinea‐pig tissues has been measured using a pH‐stat procedure. Stomach, gall bladder, proximal colon and caecum all possess more carbonic anhydrase activity per unit amount of protein than does whole blood.2. The carbonic anhydrase activity of the small intestine is low. Reasons are given for supposing that activity found there is not entirely due to contamination by whole blood, and it is suggested that in this tissue the enzyme may be localized in some cell type other than the columnar absorbing cells.3. Evidence is presented which indicates that heavy metals interfere with the activity of the enzyme as measured in tissue homogenates.4. The distribution and concentration of the two major isoenzymes of carbonic anhydrase have been measured in different tissues. Blood and proximal colon contain both isoenzymes in comparable concentrations, the ratio of the concentration of the ‘low activity’ isoenzyme to that of the ‘high activity’ being about 2. The gastric mucosa contains much ‘high activity’ carbonic anhydrase, but only a negligible amount of the ‘low activity’ isoenzyme. In the caecal mucosa, the ‘low activity’ isoenzyme is predominant, the ratio of its concentration to that of the ‘high activity’ isoenzyme being about 9. It is also found that more than 1·5% of the protein in the caecal mucosa is accounted for as carbonic anhydrase enzymes.5. It is found that some 45% of the total carbonic anhydrase activity of sucrose homogenates of the guinea‐pig colon is bound to particles. The activity is located mainly in the nuclear and microvillous fraction and in the ‘high‐speed supernatant’ fraction. The form of enzyme bound is largely of the ‘high activity’ variety. When the tissue is homogenized in potassium chloride solutions less than 4% of the total activity is recovered in particulate fractions. The amount of activity which is bound to particulate fractions increases as the ionic strength or pH of the homogenate is lowered.6. The findings are discussed in relation to the possible physiological roles of the isoenzymes in tissues other than blood. Possible relationships between the presence of the enzymes and the metabolism and transport of ammonium and fatty acids are considered.
The maintenance of resting potentials in glycerol‐treated muscle fibres
Authors: Eisenberg R. S. , Howell J. N. , Vaughan P. C. 
Published: December 2014

1. A modification of a previously published method for the disruption of the T‐tubules of frog skeletal muscle is described. The modification permits the disruption of the T‐tubules without the decline in resting potentials which was reported previously.2. The method for the disruption of the T‐tubules involves the washout of glycerol following loading in a 400 m
M glycerol Ringer solution. The modification consists of elevating the concentration of divalent cations in the Ringer used for glycerol washout.3. The optimum concentrations are 5 m
M‐Ca2+ and 5 m
M‐Mg2+ added as their chloride salts. Neither 10 m
M‐Ca2+ nor 10 m
M‐Mg2+ are as effective as the combination of each at 5 m
M. Other concentrations gave less satisfactory results.4. The use of the modified technique provides a preparation which maintains 85–90 mV resting potentials for up to 6 or 8 hr but which will not contract in response to membrane depolarization.
Effects of Ba2+ and tetraethylammonium on cortical neurones
Authors: Krnjević K. , Pumain R. , Renaud L. 
Published: December 2014

1. Ba2+, applied by micro‐iontophoresis, excites most cortical neurones that are excitable by ACh; other neurones tend to be depressed.2. The discharges evoked by Ba2+ resemble those evoked by ACh, but they have an even slower time course and are characterized by firing in high frequency bursts.3. The excitatory action of Ba2+, unlike that of ACh, is not abolished by muscarine antagonists; but it can be prevented with dinitrophenol.4. The depolarizing effect of Ba2+ is associated with a rise in membrane resistance and it has a reversal level 24 mV more negative than the resting potential.5. These observations suggest that, as in other tissues, Ba2+ reduced the K+ conductance by a direct action on the cell membrane. Some diminution in Na+ inactivation is indicated by the repetitive firing at high frequency.6. TEA has a predominantly depressant effect on all neurones tested. Like Ba2+, it often increases greatly the duration of spikes, but there is no regular change in resting membrane resistance and no tendency to repetitive firing. TEA probably reduces only the delayed K+ current.7. Even in large doses neither Ba2+ nor TEA interferes with the conductance increase that generates the typical prolonged IPSPs recorded in cortical neurones.