bluuebunny/crossref_metadata_2025_split 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.