bluuebunny/crossref_metadata_2025 huggingface dataset:
The efflux of calcium from single crab and barnacle muscle fibres
Authors: Ashley C. C. , Caldwell P. C. , Lowe A. G.
Published: December 2014

1. The efflux of calcium, as the isotope 45Ca, has been investigated from single muscle fibres from the barnacle Balanus nubilus and from the crab Maia squinado.

2. If the isotope was initially injected with sufficient calcium (5–65 m
M) to cause a contraction, the efflux did not follow first order kinetics. There was an early rapid phase which reached a peak after 5–10 min and then declined slowly over a period of 50–150 min to a low residual value.

3. Injection of the isotope with the calcium‐binding agent EGTA, so that the injected free calcium concentration was ca. 2 × 10−8
M, abolished the initial rapid loss of calcium. The efflux rose to give a steady value after 10–15 min and its magnitude was similar to the value of the residual efflux.

4. The rate constant for the low residual loss was ca. 7 × 10−4 min−1 for Maia and ca. 17 × 10−4 min−1 for Balanus. The rate constant predicted a calcium efflux of 0·4 p‐mole/cm2.sec for Maia and 1–2 p‐mole/cm2.sec for Balanus at 16–25° C based on the total fibre calcium concentration.

5. The residual calcium efflux was not affected by 0·5 m
M ouabain or 0 potassium salines applied externally. It was stimulated, some 10–15 times in Maia and to a lesser extent in Balanus, by salines containing 600 m
M potassium or 2–5 m
M caffeine. The increased efflux was associated with a brisk contraction.

6. External application of salines containing 20, 40 or 60 m
M potassium or 0·5 m
M caffeine in Maia produced some stimulation of the residual efflux but no visible contraction.

7. Pre‐treatment of Maia fibres with 40 m
M potassium or 0·5 m
M caffeine salines abolished the ability of the fibres to respond to higher concentrations of these agents. A depletion of a releasable calcium fraction by these subthreshold stimuli could explain this phenomenon.

8. Electrical stimulation, the injection of 50 m
M calcium chloride or 50 m
M caffeine produced an elevated calcium efflux which was associated with a contraction.

9. Intracellular injections of EGTA only lowered the residual efflux by up to half its initial value. This suggests that calcium can be released rapidly within these muscle fibres and that the sarcoplasmic calcium concentration is not much altered from its normal value by the injection.

10. The experiments suggest that in Maia, changes in the calcium efflux reflect in magnitude, but not in time course, the internal calcium changes which can be observed with the calcium‐sensitive protein, aequorin.
Ca concentration and flux in Ca‐deprived arteries
Authors: Keatinge W. R.
Published: December 2014

1. Extracellular Ca and EDTA concentrations in arterial smooth muscle in Ca‐free solutions with and without EDTA were estimated from 45Ca and [14C]EDTA washout studies. Ca concentrations were calculated from the measured rate of 45Ca washout at a given moment, combined with separate determinations of the coefficient of diffusion of Ca in the tissue, while EDTA concentrations were calculated by analysing an exponential phase of [14C]EDTA washout and checked by separate determinations of coefficient of diffusion of EDTA in the tissue.

2. Extracellular Ca concentrations after 30 min in simple Ca‐free saline at 36° C was 0·049 m
M at the centre of the tissue and averaged 0·033 m
M throughout the tissue; these were well above the value of 0·005 m
M‐Ca that was found to be the threshold external level for contraction after tissue stores of Ca were removed.

3. Extracellular EDTA concentration at the centre of the tissue reached 6·25 m
M after 1·9 min in EDTA 12·5 m
M at 36° C or after 4·9 min at 5° C. It reached 12·45 m
M after 30 min at 5° C, enough to keep free extracellular Ca at this point well below threshold even if all of the Ca in the tissue, determined as 0·42 μmole/g, were suddenly released on warming.

4. Ca efflux increased greatly on warming after long periods in cold EDTA, and all measurable Ca left the tissue within 30 min in EDTA 12·5 m
M at 36° C although tissue Mg did not fall significantly during this time.

5. Contractions elicited by noradrenaline in Ca‐free saline, with or without EDTA present, were not associated with any increases in the rate of external loss of Ca greater than 0·001 μmole.g−1.min−1.

6. Electronmicrographs showed numerous microvesicles that communicated with the extracellular space; also smooth endoplasmic reticulum among other structures that might have contained non‐communicating Ca stores.

7. The results provide evidence that large responses given by the arteries to noradrenaline in simple Ca‐free saline were due to persisting extracellular Ca or to labile Ca stores dependent on this, while small responses obtained after long periods in cold EDTA depended on non‐communicating Ca stores whose loss was too temperature‐dependent to be limited by diffusion.
A vasodepressor effect of pentobarbitone sodium
Authors: Feldberg W. , Guertzenstein P. G.
Published: December 2014

1. In anaesthetized cats under artificial ventilation, a few milligrams of pentobarbitone sodium injected into the cerebral ventricles produced a pronounced fall in arterial blood pressure, which was central in origin and resulted from inhibition of vasomotor tone.

2. Pentobarbitone sodium was more effective in lowering blood pressure when injected into the cerebral ventricles than when injected into the cisterna magna, yet the pentobarbitone sodium did not act on structures in the ventricular wall, but acted on structures reached from the subarachnoid space.

3. To produce its vasodepressor effect, the pentobarbitone sodium had to pass through the foramina of Luschka into the subarachmoid space beneath the medulla oblongata and to penetrate its ventral surface in a region caudal to the trapezoid bodies and lateral to the pyramids. This was the outcome of experiments in which the pentobarbitone sodium was injected into or perfused through the cerebral ventricles with or without an outflow cannula inserted into the aqueduct or into the fourth ventricle, and of experiments in which pentobarbitone sodium solutions were applied by means of Perspex rings to this region of the exposed ventral surface of the medulla. Whereas the application of pentobarbitone sodium to this region on one side had a weak vasodepressor effect only, its application on both sides produced a pronounced fall in arterial blood pressure.

4. The region where pentobarbitone acted on topical application covers the region where nerve cells are found in the marginal glia immediately under the pia mater. The possibility is discussed that these cells are the morphological substrate on which the pentobarbitone acts, that arterial blood pressure is maintained by their activity which is suppressed by the pentobarbitone sodium.
Baroreceptor sensitive neurones in the anterior hypothalamus of the cat
Authors: Spyer K. M.
Published: December 2014

1. The activity of 372 neurones, located within or close to the hypothalamic depressor area, was recorded on raising the pressure within a vascularly isolated carotid sinus.

2. When the intrasinusal pressure was raised abruptly to 200 mm Hg the activity of fifteen neurones was enhanced and of six inhibited.

3. The neurones exhibiting excitation on baroreceptor afferent stimulation were broadly divisible into two groups. Nine neurones responded with a marked increase in discharge frequency, the other six responded with a ‘burst‐on’ discharge with a minimum latency of 90 msec. Excitation in both cases was always within 500 msec of the presentation of the stimulus. No functional distinction has been drawn from these responses.

4. Evidence has been obtained suggesting that the responses of both types of neurone showing excitation may be potentiated using a pulsatile rather than static stimulus.

5. The role of the neurones in the integration of the carotid sinus baroreceptor reflex is discussed. It is suggested that the hypothalamic depressor area represents the rostral extension of the integrative centre for the reflex.
The thermal origin of spontaneous activity in the Limulus photoreceptor
Authors: Srebro Richard , Behbehani Mahmood
Published: December 2014

1. Discrete depolarizations of the photoreceptor cell membrane called discrete waves occur spontaneously and in response to illumination in the eye of the horseshoe crab, Limulus. Each light induced discrete wave is caused by the absorption of a single photon.

2. The frequencies of spontaneous and light induced discrete waves were studied at different temperatures from 0 to 25° C using a new method of counting them to avoid errors due to their temporal overlap.

3. The frequency of spontaneous discrete waves followed the Arrhenius relationship with activation energy equal to 48·6 kcal.

4. The frequency of the discrete waves caused by a fixed level of steady illumination was not significantly changed when the temperature of the cell was changed.

5. The relationship of the frequency of spontaneous discrete waves to temperature was compared to a prediction based on the relationship of the quantum relative spectral sensitivity of the Limulus eye to the temperature of the eye. The prediction was in good agreement with observation and suggests that spontaneous discrete waves result from thermally induced cis to trans isomerizations of visual pigment molecules.
High potassium and low potassium erythrocytes in cattle
Authors: Christinaz P. , Schatzmann H. J.
Published: December 2014

1. The K and Na concentrations in red blood cells (
R.B.C.) of 251 animals of the Simmenthal breed and thirty‐two animals of other cattle breeds were measured. [Na]cells+[K]cells was 89·4 m‐mole/l. cells. [K]cells varied between 7 and 70 and [Na]cells varied in the inverse sense between 15 and 87 m‐mole/l. cells.

2. The frequency distribution of animals according to K content of
R.B.C.S, which could best be fitted by two superimposed Gaussian curves, suggests that there are two distinct types of cells (high K (HK) cells and low K (LK) cells). Animals with HK cells were considerably less frequent than animals with LK cells.

3. Differences in breed, age or sex do not account for the difference in cation content of
R.B.C.S.

4. Cold stored or PCMBS‐treated HK cells show a more vigorous cation pump activity than equally treated LK cells.

5. At a Na concentration of 100 m
M and a K concentration of 10 m
M isolated haemoglobin‐free membranes prepared from HK cells exhibit a higher activity of Na+K stimulated (ouabain inhibitable) ATPase activity per mg of protein than membranes from LK cells.
Influences of sodium and calcium on the recovery process from potassium contracture in the guinea‐pig taenia coli
Authors: Katase T. , Tomita T.
Published: December 2014

1. In the guinea‐pig taenia coli, influences of Na and Ca ions on the recovery process from the K contracture were investigated. In the absence of Na ion (sucrose‐Krebs solution), the K contracture did not recover when the external K (143 m
M) was returned to the normal concentration (5·9 m
M), although the membrane was repolarized to normal resting potential.

2. After reducing the external K concentration to normal, the addition of Na rapidly terminated the contracture. About 5 m
M‐Na was enough to produce the relaxation, but the rate of relaxation was slower the lower the Na concentration.

3. Lithium could substitute for Na in the relaxation, but Tris‐hydroxymethyl aminomethane could not. The possibility of a chloride contribution was excluded.

4. Ouabain (2 × 10−6 g/ml.) and K removal reduced the rate of relaxation by Na ion only slightly. Lowering the temperature also had a small effect, having a Q10 of about 1·4. Therefore, the Na‐K pump may not be involved in this process, but a physical process seems responsible.

5. The contracture in K‐Krebs solution and in sucrose‐Krebs solution was dependent on the external Ca concentration suggesting a high Ca permeability of the membrane. When sucrose was isosmotically replaced with Mn, Mg, La or Ca ions the relaxation was produced with a relatively fast speed in the absence of external Na ions.

6. These results may be explained by assuming that external Na ions are involved in decreasing the Ca permeability of the membrane and in reducing the intracellular Ca concentration by Na‐Ca exchange, energy for which is supplied by Na influx. In the relaxation by polyvalent cations, suppression of the Ca permeability is probably the main factor.
Temperature dependence of chloride, bromide, iodide, thiocyanate and salicylate transport in human red cells
Authors: Dalmark Mads , Wieth Jens Otto
Published: December 2014

1. The temperature dependence of the steady‐state self‐exchange of chloride between human red cells and a plasma‐like electrolyte medium has been studied by measuring the rate of 36Cl− efflux from radioactively labelled cells. Between 0 and 10° C the rate increased by a factor of eight corresponding to an Arrhenius activation energy of 33 kcal/mole.

2. The rate of chloride exchange decreased significantly in experiments where 95% of the chloride ions in cells and medium were replaced by other monovalent anions of a lyotropic series. The rate of chloride self‐exchange was increasingly reduced by bromide, bicarbonate, nitrate, iodide, thiocyanate, and salicylate. The latter aromatic anion was by far the most potent inhibitor, reducing the rate of chloride self‐exchange to 0·2% of the value found in a chloride medium.

3. The temperature sensitivity of the chloride self‐exchange was not affected significantly by the anionic inhibitors. The Arrhenius activation energies of chloride exchange were between 30 and 40 kcal/mole in the presence of the six inhibitory anions mentioned above.

4. The rate of self‐exchange of bromide, thiocyanate, and iodide between human red cells and media was determined after washing and labelling cells in media containing 120 m
M bromide, thiocyanate, or iodide respectively. The rate of self‐exchange of the three anions were 12, 3, and 0·4% of the rate of chloride self‐exchange found in the chloride medium.

5. The Arrhenius activation energies of the self‐exchange of bromide, iodide, and thiocyanate were all between 29 and 37 kcal/mole, the same magnitude as found for the self‐exchange of chloride.

6. Although approximately 40% of the intracellular iodide and salicylate ions appeared to be adsorbed to intracellular proteins, the rate of tracer anion efflux followed first order kinetics until at least 98% of the intracellular anions had been exchanged.

7. The self‐exchange of salicylate across the human red cell membrane occurred by a different mechanism than the one utilized by the inorganic monovalent anions. The activation energy of salicylate exchange (13·2 kcal/mole) was significantly lower than that of inorganic anion exchange. Salicylate exchange increased with decreasing pH in contrast to the exchange of chloride, which decreases when pH is lowered.
Effect of temperature on membrane potential and ionic fluxes in intact and dialysed barnacle muscle fibres
Authors: Dipolo Reinaldo , Latorre Ramón
Published: December 2014

1. The temperature‐dependent component of the resting potential in intact, cannulated and dialysed fibres from the muscle of the barnacle Balanus nubilus was studied under a variety of different experimental conditions. A decrease in temperature from 22 to 12° C produced a mean depolarization of 10 mV.

2. Neither addition of strophanthidin, nor replacement of external sodium by lithium affect the voltage shift induced by temperature. However, the magnitude of the voltage shift depends on the external chloride and potassium concentration.

3. The dialysis technique was applied to measure the potassium, chloride and sodium fluxes as a function of temperature. The Q10 for the passive fluxes of these ions was 1·9, 1·7, and 1·4 respectively.

4. The temperature‐dependent changes in the passive ionic fluxes combined with the inability of inhibitors of the sodium pump to alter the temperature dependence of the resting potential suggest that the change induced by temperature on the resting potential is primarily caused by a change in the passive permeability ratios, and is not related to active ion transport.
The influence of electrolytes on the volume of non‐metabolizing renal cortical cells
Authors: McIver D. J. L. , Raine A. E. G.
Published: December 2014

1. The metabolism of rat renal cortex slices was inhibited by iodoacetate and anoxia, and swelling was prevented by the presence in the medium of 7·2 g polyethylene glycol 6000/100 ml. (referred to as PEG medium).

2. Slices were incubated for up to 12 hr in PEG medium, and in PEG media containing 440 m‐osmole/kg H2O of an electrolyte (LiCl, NaCl, KCl or RbCl), or a non‐electrolyte (glucose).

3. It was concluded that the slices in all media were at equilibrium with the medium after incubation for 8 hr.

4. Slices in the medium containing glucose reached the same equilibrium water content as those in the PEG medium, but slices in all the electrolyte media had significantly lower equilibrium water contents, although these did not differ significantly from each other.

5. It is suggested that the results demonstrate a non‐specific effect of electrolytes on the swelling of non‐metabolizing cells.
The action of secretin, cholecystokinin‐‐pancreozymin and caerulein on pancreatic secretion in the rat
Authors: Dockray G. J.
Published: December 2014

1. The actions of secretin, cholecystokinin‐pancreozymin (CCK‐PZ) and caerulein have been studied on the rate of flow and protein secretion from the pancreas of urethane‐anaesthetized rats.

2. Secretin stimulated the rate of flow of pancreatic juice and also stimulated the secretion of small but significant quantities of protein. Cholecystokinin‐‐pancreozymin and caerulein strongly stimulated both the rate of flow and rate of protein secretion.

3. Maximal peak rates of flow of juice stimulated by CCK‐PZ (20·3 μl./5 min), were significantly higher than stimulated by secretin (14·0 μl./5 min), but maximal volumes of pancreatic juice secreted in total response to rapid
I.V. injections of secretin and CCK‐PZ were not significantly different.

4. The time course of rates of flow of juice stimulated by CCK‐PZ and caerulein were different to those stimulated by secretin. With CCK‐PZ and caerulein peak rates occurred earlier and responses declined sooner than with secretin.

5. The actions of CCK‐PZ, caerulein and secretin on the pancreas of the rat are discussed in the light of the responses evoked in other species. It is concluded that the rat is less sensitive than other spieces to secretin but not CCK‐PZ.
The effect on heart rate of distending the atrial appendages in the dog
Authors: Kappagoda C. T. , Linden R. J. , Saunders D. A.
Published: December 2014

1. Stretching the atrial appendages in anaesthetized dogs caused an increase in heart rate. This response was unrelated to changes in arterial blood pressure and left and right atrial pressures.

2. The increase in heart rate was a reflex response; the afferent path was in the vagi and the efferent solely in the sympathetic nerves.

3. The receptors involved in this reflex have been localized to the atrial appendages but there is no conclusive evidence as to their nature.
A study of stretch and vibration reflexes of the cat by intracellular recording from motoneurones
Authors: Westbury D. R.
Published: December 2014

1. Intracellular records have been made from alpha motoneurones innervating the triceps surae muscles of the cat. The post‐synaptic responses to afferent inputs from this muscle group have been studied during high‐frequency vibration and during maintained stretches applied to their tendons of insertion.

2. A maintained stretch of the muscles caused a maintained depolarization of the motoneurones. The greater the extension of the muscles, the greater was the depolarization.

3. High frequency vibration of the muscles also caused a maintained depolarization of the motoneurone. As the frequency of vibration was increased, so the depolarization increased. The depolarization fluctuated in amplitude at the frequency of vibration.

4. The amplitude of the depolarizations caused by maintained stretch and vibration were in general greater in the motoneurones which innervated slow twitch motor units than in those which innervated fast twitch motor units. The former motoneurones were also more sensitive to changes in the amplitude of stretch or to the frequency of vibration than were those innervating fast twitch motor units.

5. Those motoneurones responding with relatively large depolarizations to maintained stretch also responded to vibration with large depolarizations. This suggests that the same population of neurones respond to both stretch and vibration.

6. When the muscles were stretched and vibrated at the same time, the phasic response to the dynamic phase of stretching was largely occluded, whereas the response to the maintained component of stretch was not occluded. The implications of these results are discussed.
Responses of neurones in the cat's visual cerebral cortex to relative movement of patterns
Authors: Burns B. Delisle , Gassanov U. , Webb A. C.
Published: December 2014

1. We have investigated the responses of single neurones in the visual cerebral cortex of the unanaesthetized, isolated cat's forebrain to excitation of one retina with patterned light. The responses of twenty‐six cells to the relative movement of two patterns in the visual field have been recorded.

2. We used several forms of relative movement for stimulation, but all of them involved a change in the separation of two parallel and straight light‐dark edges.

3. Responses to this form of stimulation were compared with the responses of the same cells to simple movement, that is, movement of the same patterns without change of distance between their borders.

4. All cells showed a response to relative movement that differed from their response to simple movement.

5. The time‐locked phasic response differed in 54% of the cells tested. Of cells responding in this way, 83% of tests produced an increased phasic response.

6. Relative movement brought about changes in the mean frequency of discharge in 96% of the cells tested. 82% of these cells responded with an increased rate of firing.

7. Movement relative to a coarse background pattern affected more neurones and produced a greater change in their behaviour than did movement relative to a fine‐grained pattern.

8. The neurones tested represented the central part of the visual field (0–10°); while all were affected by relative movement, those representing points furthest from the optic axis appeared to be most susceptible (we found no correlation between size of receptive field and distance from the optic axis).
Dependence of functional vasodilatation in the cat submaxillary gland upon stimulation frequency
Authors: Darke A. C. , Smaje L. H.
Published: December 2014

1. Submaxillary gland blood flow and salivation have been measured in anaesthetized cats and the chorda‐lingual nerve has been stimulated at different frequencies.

2. At low stimulation frequencies (1–5 Hz) there was a large transient increase in blood flow followed by a more modest maintained increase which lasted as long as stimulation continued. Stimulation at 10–20 Hz also produced a rapid initial increase in flow but at these frequencies the subsequent decline was not seen and a gradual further increase to a maintained level was observed.

3. Atropine in small doses depressed both the transient and the maintained response to low frequency stimulation but at 10–20 Hz the maintained vasodilatation was unaffected by the drug.

4. The transient increase in potassium concentration in saliva and venous blood draining the gland was not correlated with the vascular response.

5. In conclusion, further details have been provided concerning the vascular response to chorda‐lingual nerve stimulation and its sensitivity to atropine. Functional vasodilatation is not secondary to potassium release and is not due to a direct interaction between rate of saliva production and rate of blood flow although the vasodilatation does appear to be related in part to the acompanying salivation.
Electrical profiles in the corneal epithelium
Authors: Klyce S. D.
Published: December 2014

1. The potentials and resistances associated with the cell membranes of the rabbit corneal epithelium were studied with 3 M‐KCl‐filled micro‐electrodes.

2. In the isolated cornea, the transepithelial potential was identical in polarity and magnitude to the simultaneously measured total corneal potential. In contrast to previous findings, the stromal potential was positive to the tear side. Negative stromal potentials apparently derive from inadequate electrodes or method of penetration, and were not found to be a function of filling solution. Transepithelial potential was also identical to over‐all corneal potential in the living rabbit eye.

3. In the isolated preparation, the average potential profile occurred in three distinct steps across the epithelium. By means of iontophoretic dye injection it was shown that these steps occurred across the outer membrane of the squamous cell, the transition region between the wing and basal cell, and across the inner membrane of the basal cell.

4. The transverse membrane resistance of the outer epithelial membrane accounted for 60% of total corneal resistance. As a result, short‐circuit current, which depolarizes the cornea, led to a hyperpolarization of the outer membrane, while affecting deeper membrane potentials little or not at all.

5. The spontaneous potential of the outer membrane varied inversely with corneal potential in both normal and chloride‐free Ringer, while the potential of the inner membrane of the basal cell was relatively constant, approaching the theoretical Nernst potential for potassium. The potential of the outer membrane was at chloride equilibrium and was sensitive to extracellular shunts. A Thevenin equivalent drawn for the epithelium suggested that half of the outer membrane potential could be attributed to loop currents. The potential step between wing and basal cells could be accounted for in terms of loop currents driven by the corneal potential through the epithelium.

6. The potential profile of the frog corneal epithelium was similar to that of the rabbit. However, the major resistance in the frog cornea was associated with the basal cell membrane rather than with the squamous cell outer membrane. Quasi‐instantaneous rectification was found for both epithelia. In the rabbit chloride rectified inwardly.
Neurotrophic regulation of muscle cholinesterase: effects of botulinum toxin and denervation
Authors: Drachman Daniel B.
Published: December 2014

1. In order to determine the role of acetylcholine (ACh) transmission in neurotrophic regulation of muscle cholinesterase (ChE), the effects of botulinum toxin treatment were compared with those of denervation, in terms of two fractions of muscle ChE. The sternocleidomastoid muscles of rats were either denervated or injected with botulinum toxin. After 7 days the muscles were frozen, and sequential sections were assayed for acetylcholinesterase activity. By this method, the ChE activity of end‐plates (EPChE) and non‐end‐plate regions (background ChE, BChE) were separately determined.

2. The background ChE was reduced to the same extent by botulinum toxin and denervation. This is interpreted to mean that the neurotrophic regulation of BChE may be wholly cholinergic.

3. The EPChE was significantly reduced by both treatments, but the effect of botulinum toxin was only half as great as that of denervation. This indicates that EPChE is only partially regulated by ACh transmission. The larger effect of denervation suggests that some non‐cholinergic influence may be operating in this situation as well. Disruption of the structural integrity of the end‐plate, with consequent loss of binding sites for the ChE, may account for the additional effect of denervation.
The effects of decerebration on the reflex response to pulmonary vein distension
Authors: Albrook Sally M. , Bennion Glenda R. , Ledsome J. R.
Published: December 2014

1. A method is described for the decerebration of dogs using high frequency coagulation. Animals made decerebrate by this method showed a slowing of the heart rate and a decrease in arterial pressure.

2. Distension of the pulmonary vein—left atrial junctions by the inflation of small balloons caused an increase in heart rate in intact and decerebrate dogs. The magnitude of the response was not significantly different in the two states.

3. The increase in heart rate caused by pulmonary vein distension was shown to be a reflex. It was significantly reduced by injection of propranolol both before and after decerebration. Cervical vagotomy always prevented any response.

4. The similarity of the responses before and after decerebration suggests that structures rostral to the superior colliculus are not required for the appearance of the full reflex effect.

5. The magnitude of the response remaining after administration of propranolol raised the question of the efficacy of propranolol as a β‐blocking agent in this experimental situation, or alternatively suggests the possibility of the existence of an efferent vagal component to the reflex response.
Kinetic properties of the sodium current in striated muscle fibres on the basis of the Hodgkin—Huxley theory
Authors: Ildefonse Michèle , Roy Guy
Published: December 2014

1. The kinetic properties of the sodium current in skeletal muscle fibre, obtained from records in a double sucrose‐gap apparatus, have been analysed in terms of the Hodgkin—Huxley formulation by means of a curve fitting computer program.

2. The net sodium currents were obtained by subtracting records in Ringer and Ringer tetrodotoxin; the currents are inward for depolarizations V from +25 to +128 mV (VNa). The INa—V characteristic shows a small inward rectification for V > + 128 mV.

3. The characteristics of both sodium conductance and permeability are described.

4. The activation and inactivation parameters, m and h, are calculated and compared with those experimentally established in a previous work (Ildefonse & Rougier, 1972) and with the results of Adrian, Chandler & Hodgkin (1970).

5. The currents calculated with these parameter values fit rather well with the experimental ones, the permeability approach being slightly better.

6. The main difference between the experimental and calculated curves is the slower inactivation of the calculated current at V = +55 mV; this difference is envisaged as a possible consequence of some activity in the tubular system of the muscle fibre.
Comparison of the effects of hepatic nerve stimulation on arterial flow, distribution of arterial and portal flows and blood content in the livers of anaesthetized cats and dogs
Authors: Greenway C. V. , Oshiro G.
Published: December 2014

1. The responses to hepatic nerve stimulation were studied in cats and dogs anaesthetized with sodium pentobarbitone. In three series of experiments, hepatic arterial flow was recorded by an electromagnetic flowmeter, intrahepatic distributions of arterial and portal flows were studied by radioactive microspheres, and hepatic volume responses were measured by a plethysmographic method.

2. In cats, nerve stimulation produced a temperature‐dependent decrease in hepatic arterial flow which was not maintained and autoregulatory escape occurred. In dogs, the initial decrease in arterial flow was similar but escape did not occur and the vasoconstriction was well maintained.

3. In both cats and dogs, stimulation of the hepatic nerves did not cause a redistribution of either arterial or portal flows within the liver. Autoregulatory escape in the liver of the cat was not associated with an intrahepatic redistribution of arterial flow and is best interpreted as relaxation of the same vessels which were initially constricted, due to increased production of a vasodilator factor.

4. Stimulation of the hepatic nerves caused a marked temperature‐dependent decrease in hepatic volume which was well maintained and the responses were similar in cats and dogs. The quantitative importance of the liver as a blood reservoir is compared in relation to other vascular beds and the concept of the blood volume reserve is discussed.
Light‐induced changes in the electrical impedance of the isolated frog retina
Authors: Coles J. A.
Published: December 2014

1. An isolated frog retina was mounted in an impedance chamber and superfused on its vitread surface.

2. Changes in the real part of the impedance (ΔR) and also in the imaginary part were measured using alternating current in the frequency range 1–300 kHz passed from one surface of the retina to the other.

3. Under most conditions, the response to a flash of light, measured at frequencies below about 100 kHz, was a decrease in the real part of the impedance (ΔR < 0).

4. The geometry of the electrodes was such that the system was particularly sensitive to changes in the impedance of the layer of photo‐receptor outer segments. It was confirmed that most of ΔR did arise here and that it was mediated by the absorption of light in rod photo‐pigment.

5. The magnitude of ΔR increased when the channels between the outer segments were constricted, e.g. by osmotic swelling of the outer segments. In addition to this increase, a further increase was seen following the commencement of recording in most of the experiments from which usable measurements were obtained.

6. In such retinas, the magnitude of ΔR was greatest when measured at a frequency in the range 3–32 kHz, the largest changes being of the order of 0·1% of the resting value. A light flash bleaching about 1% of the pigment was sufficient to produce this. The onset of ΔR was apparent within 1 msec of the flash (at 15° C); it reached a maximum in 0·5‐4 sec and then returned towards the base line.

7. The main component of ΔR was attributed to a decrease in the resistance of the spaces between the outer segments. In addition, there was a resistance increase which occurred at some other site, probably the surface membrane. The first of these components had an onset slightly more rapid than the second, and both occurred irrespective of whether the major cation in the superfusate was sodium or potassium.
Functional relationship of longitudinal and circular layers of the muscularis externa of the rabbit large intestine
Authors: McKirdy H. C.
Published: December 2014

1. The functional relationship of the longitudinal and circular layers of the muscularis externa of the rabbit large intestine has been studied in a flat preparation.

2. Evidence is presented that mechanical activity can be recorded independently and simultaneously from the two muscle layers of the flat preparation. Such evidence accrues mainly from results obtained from the flat preparation in response to various drugs.

3. During spontaneous rhythmic contractions and during the response to pelvic (parasympathetic) nerve stimulation, both layers show similar activity, never opposite or reciprocal activity.

4. In this flat preparation, the mechanism controlling the level of sustained tension (i.e. ‘tone’) may be dissociable, within limit, from the mechanism controlling rhythmic contractions.
Effects of chemicals on receptors and horizontal cells in the retina
Authors: Murakami Motohiko , Ohtsu Kohzoh , Ohtsuka Teruya
Published: December 2014

1. By applying atomized chemical solutions on to gecko and carp retinae, neuropharmacological reactions of the photoreceptors and horizontal cells were observed.

2. Sodium
L‐glutamate and
L‐aspartate, glycine, ACh and GABA, had no appreciable effect on the photoreceptor activity.

3. Carp horizontal cells were depolarized by both
L‐glutamate and
L‐aspartate. When maximally depolarized, the action of the endogenous transmitter from the receptor terminals was completely masked, resulting in abolition of the S‐potentials.

4. Responses to red light in both L‐ and C‐type horizontal cells were more strongly affected by aspartate than responses to blue light.

5. Glycine and GABA hyperpolarized the horizontal cells, and the S‐potentials were diminished.

6. ACh had no effect on the activity of the horizontal cells.
Frequency‐dependent differences in the responses of the capsular and vascular smooth muscle of the spleen of the dog to sympathetic nerve stimulation
Authors: Davies B. N. , Gamble J. , Withrington P. G.
Published: December 2014

1. The responses of the capsular and vascular smooth muscle to splenic nerve stimulation have been studied simultaneously in the isolated blood‐perfused dog's spleen.

2. Low frequencies of splenic nerve stimulation (below 1·0 Hz) caused pronounced contraction of the splenic capsule but little or no constriction of the splenic vascular bed.

3. Splenic contraction reached a maximum at stimulation frequencies of 1–2 Hz; maximum vasoconstriction occurred at frequencies of 7–10 Hz.

4. The separation of responses of the capsular and vascular smooth muscle was mimicked by close arterial infusions of either adrenaline or noradrenaline.

5. The maximum responses of the splenic vascular smooth muscle to nerve stimulation, adrenaline and noradrenaline were not significantly different.

6. The maximum reduction in spleen volume to sympathetic nerve stimulation was significantly greater than the maximum response to close arterial noradrenaline.

7. The maximum contractions of the spleen to adrenaline and noradrenaline were not significantly different. At concentrations producing submaximal responses adrenaline was more potent than noradrenaline.

8. It is suggested that the frequency dependent separation of smooth muscle responses to sympathetic nerve stimulation is due to a different sensitivity of the capsular and vascular smooth muscle to the chemical transmitter noradrenaline.

9. The results are discussed in the context of the function of the dog's spleen.
Blood volume determination in the mouse
Authors: Riches A. C. , Sharp J. G. , Thomas D. Brynmor , Smith S. Vaughan
Published: December 2014

1. The blood volume of the mouse has been measured using 59Fe‐labelled red cells to determine the red cell volume and 131I‐labelled human serum albumin to determine the plasma volume.

2. Values for the blood volume of 95·0 ± 1·5, 96·3 ± 2·7 and 84·7 ± 1·2 ml./kg body wt. were found for CSI female, CBA female and CBA male mice respectively.

3. A marked discrepancy was observed between the venous (cardiac) haematocrit and the whole body haematocrit.

4. The blood volume of the mouse must be determined from the red cell volume and the plasma volume, measured using appropriate labels, and not from the red cell volume or the plasma volume using the venous haematocrit.
Gastric emptying and secretion in the milk‐fed calf
Authors: Bell F. R. , Razig S. A. D.
Published: December 2014

1. For a few weeks, immediately post‐natally, the abomasum of the ruminant stomach can be regarded as the analogue of the simple stomach for at this time food passes directly to the abomasum because of closure of the oesophageal groove.

2. Using standard fractional and serial test meal techniques discussed by Hunt (1956) and adapted for use in the calf, abomasal emptying, acid and pepsin secretion have been examined. Phenol red was used as a marker to measure volume changes of the test meal.

3. Abomasal emptying is exponential in character whether large or small volumes of fluid are instilled into the abomasum. The initial and end phase of emptying shows variable rates between animals.

4. Glucose and lactose solutions inhibit abomasal emptying as well as acid production.

5. Sodium chloride and sodium bicarbonate of low concentration, near isotonic with blood plasma, stimulate abomasal emptying but the bicarbonate is most effective. Hypertonic solutions of these salts inhibit abomasal emptying.

6. Pepsin secretion in the abomasum of the calf is not affected by test meals of glucose, lactose, sodium chloride or sodium bicarbonate.

7. These results shows a great similarity between the physiology of the abomasum of the milk‐fed calf and the simple stomach. This suggests that the same duodenal receptors, discussed by Hunt & Knox (1968), which control gastric movement in man are also effective in controlling gastric emptying in the milk‐fed calf.
The effect of a preceding stimulus on temporal facilitation at corticomotoneuronal synapses
Authors: Muir R. B. , Porter R.
Published: December 2014

1. Intracellular recordings were made of minimal corticomotoneuronal e.p.s.p.s in lumbar motoneurones of anaesthetized monkeys. For intervals of 2 msec and greater between paired cortical shocks, the average time course of facilitation of the second e.p.s.p. with respect to the first could be fitted closely by a negative exponential with a time constant of 10 msec.

2. In the same motoneurones, ‘triplets’ of corticomotoneuronal e.p.s.p.s were generated by delivering three identical stimuli to the motor cortex. Considering the triplet as a conditioning e.p.s.p. followed by a test pair, the facilitation of the third e.p.s.p. with respect to the second was measured for various combinations of test and conditioning intervals. In each case the amplitude of the third e.p.s.p. was also compared with that of the first (conditioning) e.p.s.p.

3. The effect of a brief conditioning interval was to reduce considerably the facilitation of the third e.p.s.p. with respect to the second at all test intervals from 2 to 50 msec. Combinations of brief conditioning intervals (e.g. 2 or 5 msec) and long test intervals (e.g. 20 or 50 msec) caused the third e.p.s.p. to be smaller than the second. As the conditioning interval lengthened, facilitation in the test pair increased towards the unconditioned values at all test intervals.

4. Facilitation of the third e.p.s.p. with respect to the first could be described approximately as the linear addition of two facilitation components, one due to the conditioning input and one due to the first stimulus of the test pair. Each component followed the same negative exponential time course as found for an isolated pair of e.p.s.p.s and each of the first two inputs contributed to the facilitation of the third e.p.s.p. as if the other of these two inputs had not occurred.
The action of calcium at spinal neurones of the frog
Authors: Dambach G. E. , Erulkar S. D.
Published: December 2014

1. The action of Ca on membrane excitability and synaptic transmission at motoneurones of the isolated spinal cord of the frog has been studied.

2. Impulse propagation along presynaptic fibres was unaffected by [Ca] in the range of 0–10 m
M in the presence of 1 m
M‐Mg.

3. Motoneurone membrane excitability was within normal ranges when the cord was bathed in low or 0 Ca solutions containing 1 m
M‐Mg but was depressed in 5 or 10 m
M‐Ca solutions.

4. Spontaneous miniature synaptic potentials were recorded in the presence of tetrodotoxin. The frequencies were reduced but not abolished in the absence of bath Ca, but were increased greater than twofold in 5 or 10 m
M‐Ca in comparison to those in normal Ringer solution (1 m
M‐Ca).

5. Iontophoretic application of Ca both near to and remotely from the intracellular recording site (presumably in the soma) caused facilitation of elicited post‐synaptic potentials.

6. It is concluded that the action of Ca at these central synapses is identical to that described at the neuromuscular junction.
An electrophysiological investigation of the receptor apparatus of the duck's bill
Authors: Gregory J. E.
Published: December 2014

1. The properties of receptors in the duck's bill have been studied by recording from units isolated by dissecting fine filaments from the maxillary and ophthalmic nerves.

2. The units studied were divisible into three groups, phasic mechanoreceptors responsive to vibration, thermoreceptive units, and high threshold mechanoreceptors.

3. Vibration‐sensitive mechanoreceptors (113 units) had small receptive fields, showed a rapidly adapting discharge to mechanical stimulation of the bill, were sensitive to vibratory but not to thermal stimuli and showed no background discharge.

4. Temperature receptors (twenty‐one units) were insensitive to mechanical stimulation and showed a temperature‐dependent background discharge. Sudden cooling produced a transient increase in discharge frequency.

5. High threshold mechanosensitive units (eight units) gave a slowly adapting discharge to strong mechanical stimulation and were insensitive to vibratory and thermal stimulation.

6. It is concluded that the low‐threshold, vibration‐sensitive responses come from Herbst corpuscles. No specific function can yet be assigned to the Grandry corpuscles.
Isolation of components of admittance change in rod outer segments
Authors: Falk G. , Fatt P.
Published: December 2014

1. Rods were separated by equilibration on a bovine serum albumin (BSA) density gradient into two major fractions, differing in their response to light.

2. In one fraction the response, measured as a change in the real part of admittance ΔG, appeared to consist exclusively of component I, while in the other, component II was prominent.

3. Evidence is presented that component I arose in damaged rods. This follows from observations on rods which have been deliberately damaged by freezing followed by thawing, or by fragmentation.

4. In such damaged rods, component II was absent while component I was increased in amplitude.

5. The frequency dependence of component I in isolation was characterized as a positive ΔG of constant amplitude from low frequencies up to the characteristic frequency fY for the major dispersion of admittance. Above this frequency, it declined to a variable extent.

6. The frequency dependence of component II observed in isolation was consistent with the previous analysis.

7. A negative‐going ΔG is described which was linear with the amount of rhodopsin bleached and which was frequency independent up to the highest frequency of measurement (17 MHz).

8. The origins of component I and the negative component are discussed.
Muscle spindle afferent studies in the baboon
Authors: Koeze T. H.
Published: December 2014

1. The muscle spindle afferent conduction velocity and response to muscle twitch and stretch in young baboons has been recorded in order to find a conduction velocity that can be used to separate primary and secondary afferents.

2. A number of the features of the response of the spindle afferents to stretch were examined. It was found that none could distinguish between primary and secondary afferents with greater certainty than the conduction velocity.

3. Spindle afferents with conduction velocities below 50 m/sec can be classified as secondary and those with conduction velocities above 68 m/sec can be classified as primary with a reasonable degree of certainty.

4. The spindle afferents with conduction velocities between 51 and 67 m/sec are most likely not a separate intermediate group but represent a region of overlap between the two groups.

5. Comparisons of the difference between the response of primary and secondary afferents to overstretch suggested a mechanism to explain the saturation of the primary afferent response at frequencies far below those at which it is capable of firing.