bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sodium flux and electrical activity of arterial smooth muscle
Authors: Keatinge W. R. 
Published: December 2014

1. The intracellular concentration and transmembrane flux of Na in smooth muscle cells of sheep carotid arteries were measured by identifying a fraction of tissue Na whose efflux was markedly sensitive to removal of external Ca. This allowed intracellular Na to be distinguished from extracellular bound Na exchanging with a similar time constant.2. When the arteries were in solution containing Na 148 m
M and Ca 2·5 m
M the mean intracellular Na concentration was 7·3 m‐mole/kg cell water and the mean transmembrane flux of Na was 0·18 p‐mole cm−2 sec−1, both values being much lower than reported values for intestinal smooth muscle.3. During electrical activity induced by Ca deprivation the influx of Na increased to 3·2 p‐mole cm−2 sec−1; a 50% reduction in Na concentration stopped electrical activity and reduced influx by more than 50%, and the excess Na influx per action potential was calculated to be at least 1·0‐1·5 p‐mole cm−2.4. Arteries in physiological saline (Ca 2·5 m
M) contained 3·48 μmole Ca/g, much of which was bound extracellularly; in Ca‐free saline 1·39 μmole Ca/g left the tissue within 3 min, showing that extracellular dissolved Ca diffused freely out of the tissue.5. The results provide further evidence that Na is the principal ion carrying the depolarizing current of action potentials in this smooth muscle.
Some effects of ouabain and potassium on transport and metabolism in rat small intestine
Authors: Newey H. , Sanford P. A. , Smyth D. H. 
Published: December 2014

1. Ouabain (10−3
M) inhibited the transfer of glucose, proline, methionine and fluid but not of galactose and 3‐O‐methyl glucose by sacs of rat everted intestine.2. Ouabain (10−3
M) inhibited both glucose and mannose metabolism. Hexose metabolism was also reduced by varying the [K] from 4·8 m‐equiv/l.3. Ouabain (10−3
M) or absence of K reduced the stimulation of amino acid, hexose and fluid transfer by mannose. Although presence of ouabain or absence of K did not inhibit endogenous galactose transfer, these conditions prevented mannose from stimulating this transfer.4. Ouabain (10−3
M) exerted greater effects on hexose and amino acid transfer when K was omitted from the saline and its inhibitory effects were partially overcome by increased serosal [K].5. Ouabain (10−2
M) caused further inhibition of amino acid and glucose transfer and also reduced the transfer of galactose and 3‐O‐methyl glucose.6. The implications of these results are discussed with respect to the relationships between cations and hexose and amino acid transfer.
Factors influencing the electrical potential across the mucosa of rat colon
Authors: Edmonds C. J. , Marriott Jane 
Published: December 2014

1. An investigation has been carried out into various factors which influence the transmucosal potential difference (p.d.) of rat colon in vivo when the p.d. is either high (> 30 mV) or low (< 20 mV).2. The p.d. was uninfluenced by short duration anaesthesia with ether or pentobarbitone. When anaesthesia was prolonged for several hours, p.d. rose steadily. The gradient of p.d. along the descending colon which developed and its elimination by adrenalectomy suggested that the rise was due to increased secretion of adrenal steroids.3. P.d. was increased by Na depletion after a delay of about 18 hr and fell again following Na repletion with a similar time delay. A characteristic gradient of p.d. along the descending colon was seen.4. Both haemorrhage and anoxia caused a rapid fall of p.d. P.d. was restored rapidly to its previous level when anoxia was corrected.5. Vasopressin (
I.V.) in low dose was without effect; in high dose it caused a transient fall of p.d. associated with intense vasoconstriction of gut blood vessels.6. The following factors studied were without effect on p.d.: presence of glucose within the lumen; considerable osmotic gradients across the mucosa; variation of luminal pH over the range 5·2‐9·8; intravenous administration of acetazolamide, chlorothiazide, frusemide, triamterene, ethacrynic acid or ouabain. Ouabain in the luminal solution also had no effect in all but two rats in which a small fall of p.d. was seen.7. 2,4‐dinitrophenol, 10−2
M, in the lumen caused a small fall of p.d. only if the p.d. was high.8. Experiments were done to determine the effect on p.d. of altering the ionic composition of the luminal solution. When the p.d. was low (< 20 mV) alteration of [Na], [K] or [Cl] produced small absolute changes of the p.d., all of comparable magnitude. The changes could be interpreted as due to diffusion potentials resulting from the ionic gradients across the mucosa. When the p.d. was high (> 30 mV), it showed a striking dependence on the luminal [Na] only, consistent with the presence of a large p.d. due to active Na transport.
A ouabain‐sensitive membrane conductance
Authors: Geduldig D. 
Published: December 2014

1. Changes in membrane conductance and potential of sodium‐loaded frog muscle fibres were found when the external recovery solution was changed: from cold to warm, to warm plus ouabain, to cold plus ouabain. Comparisons of these measurements for different external solutions were made by leaving the electrodes implanted in the same fibre during all solution changes. (The recovery solutions contained 10 m
M‐K and 82 m
M‐Cl.)2. The membrane potential became more negative on warming, less negative when ouabain was added, and still less negative when the ouabain‐containing recovery solution was cooled. The membrane conductance increased on warming, increased further on addition of ouabain, and decreased when the ouabain‐containing recovery solution was cooled.3. The increase of conductance which occurred on warming decreased with increasing periods in cold recovery. The increase of conductance which occurred on addition of ouabain decreased if the ouabain was added to the recovery solutions of muscles which were more fully recovered.4. The ouabain‐sensitivity of the membrane conductance may be dependent upon the sodium‐pump rate, or the extent of recovery of the sodium‐loaded muscle fibre in the potassium‐ and chloride‐containing recovery solutions.5. It is suggested that if the potassium conductance of the membrane increases with decreasing sodium‐pump rates, then during the initial part of the recovery period a non‐electrogenic mechanism must be producing a substantial part of the early net potassium influx.
The ineffectiveness of excitation of the primary endings of the muscle spindle by vibration as a respiratory stimulant in the decerebrate cat
Authors: Hodgson H. J. F. , Matthews P. B. C. 
Published: December 2014

1. Small‐amplitude high‐frequency longitudinal vibration (for example, 100 μ peak to peak amplitude at 250 c/s) was applied to the triceps surae muscle of the decerebrate cat without producing any appreciable change in its respiration.2. Manual squeezing of the same muscle produced a large increase in ventilation.3. As vibration is known to be a powerful stimulus for the primary endings of the muscle spindle it is concluded that these receptors are unlikely to have any significant role to play in the reflex regulation of breathing.
The effect of haemorrhage on haemoglobin concentration, blood volume and arterial pressure in kittens and cats
Authors: Mott Joan C. 
Published: December 2014

1. The arterial haemoglobin concentration in kittens less than 24 hr old was inversely related to body weight. There was about twice as much haemoglobin/unit body weight at birth as in adult cats. Haemoglobin concentrations were minimal at 3‐6 weeks of age.2. In animals lightly anaesthetized with sodium pentobarbitone, arterial pressure rose from 52 mm Hg at birth in kittens to 133 mm Hg in adult cats. Blood volume decreased from 73 ml./kg at birth to 60 ml./kg in adults.3. When kittens less than a fortnight old were subjected to stepwise blood letting, arterial pressure fell proportionately with blood volume; in older kittens and in cats, arterial pressure was less well maintained at similar proportionate reductions of blood volume than in young kittens.4. The responses to haemorrhage of kittens and cats were compared with those of rabbits similarly treated and with those of adult cats anaesthetized with urethane and chloralose reported in the literature.
The role of sodium and potassium in insulin secretion from rabbit pancreas
Authors: Hales C. N. , Milner R. D. G. 
Published: December 2014

1. Insulin secretion from pieces of rabbit pancreas incubated in vitro was studied in media of different ionic composition and in response to different substances added to the media.2. Experiments were performed which demonstrated that a sodium pump played a role in insulin secretion and that inhibition of the pump by ouabain, or by the omission of extracellular potassium, stimulated insulin secretion.3. A rise in extracellular potassium concentration stimulated insulin secretion independently of changes in the osmolarity or sodium or chloride concentration of the incubation medium.4. The role of extracellular sodium in insulin secretion was investigated. Extracellular sodium was a pre‐requisite for insulin secretion stimulated by glucose, glucagon,
L‐leucine, tolbutamide, potassium or ouabain.5. The presence of 3·3 m
M glucose in the incubation medium was not essential for the stimulation of insulin secretion by
L‐leucine, tolbutamide or ouabain. Glucagon did not stimulate insulin secretion in the presence of 3·3 m
M glucose but did so in the presence of 16·5 m
M glucose.6. The results obtained in these experiments suggested that a transmembrane sodium flux probably in the β cell was a fundamental event in the stimulation of insulin secretion by diverse stimuli.
Resting and action potentials recorded by the sucrose‐gap method in the superior cervical ganglion of the rabbit
Authors: Kosterlitz H. W. , Lees G. M. , Wallis D. I. 
Published: December 2014

1. Evoked ganglionic action potentials and drug‐induced changes in resting potential were recorded by the sucrose‐gap method. The height of the action potential was 10‐20 mV.2. Since the amplitude of the P wave is inversely proportional to the external potassium concentration between 0·5 and 12 m
M, the P wave is probably caused by a phase of increased permeability to K+.3. In the absence of an anticholinesterase, the depolarizing actions of choline and acetylcholine on the ganglion are almost equal, whereas acetylcholine is 2‐3 times more potent than choline on the fibres of the internal carotid nerve. In the presence of eserine, acetylcholine induces a depolarization of the ganglion of up to 14 mV, while increase in [K+]o causes a depolarization of up to 55 mV.4. Although the post‐ganglionic fibres in the distal pole of the ganglion are depolarized by drugs, for example, acetylcholine, they contribute little to drug‐induced potential changes and probably little to evoked action potentials.5. The hyperpolarization which occurs after exposure of the ganglion to acetylcholine is not due to a phase of increased permeability to K+.
Bleached rhodopsin and retinal interaction
Authors: Westheimer Gerald 
Published: December 2014

1. The human rod retina exhibits lateral inhibition which is demonstrated by the sensitization, i.e. improvement in incremental threshold sensitivity, of a steadily illuminated patch of retina when its surround is also illuminated.2. Experiments were carried out to test whether the previously reported equivalence between steady illumination (real light) and signals from bleached rhodopsin (dark light) also carries over into lateral interaction.3. Symmetrical experiments involving real light patches surrounded by dark‐light annuli, dark‐light patches surrounded by real‐light annuli, and dark‐light patches surrounded by dark‐light annuli showed that dark light is neither susceptible to sensitization by lateral interaction nor capable of exerting it.
The effect of calcium on contraction and conductance thresholds in frog skeletal muscle
Authors: Costantin L. L. 
Published: December 2014

1. The effect of extracellular calcium and magnesium on the contraction threshold and on the thresholds for an increase in sodium and potassium conductance with depolarization was studied in voltage‐clamped frog muscle fibres.2. A larger depolarization was required to reach each of the three thresholds when the concentration of divalent cation was increased.3. The contraction and potassium conductance thresholds appeared to shift in parallel with alterations in calcium over the concentration range 0·2‐10·0 m
M and in magnesium over the concentration range 5·4‐90·0 m
M. The shift amounted to about 4 mV for a threefold change in concentration of divalent cation.4. The sodium conductance threshold was much more sensitive to alterations in divalent cation concentration than was either the contraction or the potassium conductance threshold.
The mechanism of oxygen concentration in the swim‐bladder of the eel
Authors: Berg Trond , Steen Johan B. 
Published: December 2014

1. The PO2 of venous blood from the active swim‐bladder of the eel was shown to decrease with distance from the exit of the rete. This systematic change did not occur in non‐secreting bladders, nor during conditions where exchange in the rete had been abolished.2. The observed change in post‐rete venous PO2 has the same rate constant as the Root‐on shift.3. These findings modify the accepted model for counter‐current multiplication of O2 in the swim‐bladder system by introducing rate constants for diffusion and action of acid in the rete.4. The part played by the assumed impermeability to acid of the arteriovenous partition of the rete is in the modified model replaced by the slow Root‐on shift.5. The modified model contradicts the Kuhn model in that extraction of O2 from blood is decreased at low flow and that at normal flow conditions part of the lactic acid produced can be re‐used.6. Similar modifications are indicated in the model for concentration of inert gases.
The ionic content of mammalian non‐myelinated nerve fibres and its alteration as a result of electrical activity
Authors: Rang H. P. , Ritchie J. M. 
Published: December 2014

1. A study has been made of the ionic content, and of the fibre water, of rabbit desheathed vagus nerves at rest and after activity in various modified Locke solutions.2. In normal Locke solution the intracellular sodium amounted to 86·1 μmole/g dry, and the intracellular potassium 186·0 μmole/g dry. Since the fibre water amounted to 1·124 g/g dry the intracellular sodium and potassium concentrations were 76·6 and 165·5 m‐mole/kg fibre water, respectively.3. In potassium‐free Locke solution the intracellular sodium and potassium concentrations were 111·0 and 121·7 m‐mole/kg, respectively. The intracellular chloride concentration was 40·5 m‐mole/kg.4. In normal Locke solution, a brief period of stimulation followed by a 10 min recovery period produced no significant change in the intracellular contents of potassium, sodium, or water.5. However, in chloride—Locke solution from which the potassium had been omitted, or to which ouabain (1 m
M) had been added, stimulation caused a loss of potassium per impulse of about 20 p‐mole/mg dry, i.e. about 4 p‐mole/mg wet. A similar loss was found in isethionate—Locke solution that was potassium‐free. There was no significant change in any of the other quantities measured (sodium, chloride, and fibre water).6. The efflux of radioactively labelled potassium was measured in potassium‐free Locke solution at rest (kr) and during activity (ks). At 24° C, kr was 0·0084 min−1 and ks was 0·000178 impulse−1.7. When the chloride of Locke solution was replaced by isethionate there was an increase in both kr (about 12%) and ks (about 21%).8. Ouabain (1 m
M) increased ks (by about 70%). This increase seemed to be independent of whether the anion present was chloride or isethionate.9. It is argued that these results indicate that the electrogenicity of the pump plays a relatively small role in maintaining the ionic balance in mammalina C fibres.
The effect of sodium concentration on the content and distribution of sodium in the frog skin
Authors: Cereijido M. , Reisin I. , Rotunno Catalina A. 
Published: December 2014

1. The content and distribution of sodium in the epithelium of the frog skin (Leptodactylus ocellatus L.) have been studied.2. The inulin space, the 22Na exchange, and the amounts of water and sodium were measured in samples of connective tissue. The results indicate that the necessary assumptions generally made to calculate the sodium and water contents of the epithelial cells as the difference between the total content in the tissue and the amounts contained in the inulin space are not valid in the frog skin.3. The mean concentration of sodium in the epithelium has been obtained from direct measurements of sodium and water in samples of epithelium. To measure the water content of the epithelium a new technique has been developed. When the skin is bathed with Ringer solution containing 115 m
M‐Na on both sides, the mean concentration of sodium in the epithelium is 79 m
M. When the concentration of sodium in the Ringer is 1 m
M the mean concentration in the epithelium is 25 m
M. When the skin is bathed with Ringer with 1 m
M‐Na on the outside and 115 m
M‐Na on the inside—a situation which resembles the natural condition in the skin—the mean concentration of sodium in the epithelium is 52 m
M.4. The compartmentalization of Na was studied by comparing the sodium content and the degree of exchange with 22Na in the bathing solutions. In these experiments the skins were exposed to Ringer solutions with different concentrations of sodium, and 22Na on one or both sides.5. The results indicate that the epithelium has a compartment of sodium which is not exchangeable in 40‐80 min and whose size is not appreciably changed by a threefold change in the Na content in the epithelium and a hundredfold change in the concentration of the bathing solution.6. Sodium exchangeable in 40‐80 min seems to be contained in two different compartments: (a) a large one that contains fixed sodium is mainly connected to the inside, and does not appear to participate directly in sodium transport across the frog skin; (b) a small one, that is bounded on the inside by a Na‐impermeable barrier, and that seems to comprise the sodium involved in active transport. When the skin is bathed with Ringer solutions with 115 m
M‐Na on the inside and 1 m
M‐Na on the outside, the transporting compartment contains some 13% of the total sodium in the epithelium.7. The results are interpreted on the basis of a model recently proposed by Cereijido & Rotunno (1968). The major feature of this model is that the sodium transporting compartment is confined to the plasma membrane of the epithelial cells.
Studies on the longitudinal muscle of the anterior mesenteric artery of the domestic fowl
Authors: Bolton T. B. 
Published: December 2014

1. A simple, isolated preparation is described in which the activity of the longitudinal muscle of the anterior mesenteric artery of the domestic fowl is recorded isotonically.2. The longitudinal muscle of the anterior mesenteric artery exhibited tone and marked spontaneous activity. Maximal shortening of this muscle was equal to about 60% of its resting length.3. Acetylcholine in low concentrations produced powerful contractions of the muscle, whereas low concentrations of catecholamines produced relaxation by an action on β‐receptors; much larger concentrations of adrenaline or noradrenaline contracted the muscle. A pharmacological analysis of the responses to electrical stimulation and to agonist drugs indicated that the muscle was supplied by excitatory, cholinergic nerves and by inhibitory, adrenergic nerves.
Electrical and mechanical activity of the longitudinal muscle of the anterior mesenteric artery of the domestic fowl
Authors: Bolton T. B. 
Published: December 2014

1. The electrical activity and changes in tension of the longitudinal muscle of the anterior mesenteric artery (LMAMA) of the domestic fowl were recorded simultaneously using the sucrose‐gap method.2. Spontaneous activity consisted of recurring contractions each accompanied by a burst of action potentials.3. In quiescent preparations, brief electrical stimuli, acetylcholine, or barium chloride produced contractions with the appearance of action potentials. Larger concentrations of barium chloride or acetylcholine produced depolarization and action potentials ceased although contraction was maintained. Whenever depolarization without action potentials occurred, it was associated with a smooth contraction, whereas action potentials were always accompanied by small rapid contractions super‐imposed upon the main contraction.4. When the tone was raised with barium chloride (and in the presence of hyoscine) continuous action potentials occurred; under these circumstances brief electrical stimuli or noradrenaline produced relaxation, cessation of action potentials, and hyperpolarization.
Facilitation of heart muscle contraction and its dependence on external calcium and sodium
Authors: Orkand R. K. 
Published: December 2014

1. The magnitude and time course of the facilitation of contraction following previous stimulation have been studied in strips of frog ventricle when the external concentrations of Na and Ca were varied. The maximum tension and the maximum rate of rise of tension have been used as indices of activation of the contractile element. Under the experimental conditions these two parameters changed similarly.2. At low stimulus frequencies (3‐12 beats/min), and moderate concentrations of external Ca (2‐5 m
M), the facilitation of contraction with repetitive stimulation can be predicted by assuming each contraction to produce an amount of facilitation which sums linearly with that remaining from previous responses. Thus, the staircase can be constructed from the decay of facilitation following a single contraction.3. The decay of facilitation appears to consist of two components. The first has a half‐time of about 3 sec; the second about 50 sec. The decay of the second component of facilitation is slowed and its magnitude increased by raising the external Ca from 2 to 5 m
M.4. Reducing the external Na concentration increases both the initial strength of contraction and the amount of facilitation.5. When the ratio Ca/Na2 is kept constant while changing the Ca and Na concentrations, the first contraction in a series remains constant, but facilitation is less at low concentrations of Ca and Na. Facilitation, therefore, does not depend solely on the amount of initial activation of the contractile system.6. The results are consistent with the hypothesis that facilitation depends on the amount of calcium retained in some cellular store.