bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Na, metabolic inhibitors and ATP on Ca movements in L cells
Authors: Lamb J. F. , Lindsay R. 
Published: December 2014

1. The Ca movements in normal and ‘ghost’ L cells have been examined; all measurements were made using 45Ca.2. Normal cells have a Ca concentration of about 1 m‐mole/l. of cell volume, and exchange Ca in a complex way but with great rapidity; the time taken for the initial Ca* content to fall to half was less than 2 min.3. Poisoning normal cells with DNP 10−3
M + IAA 10−4
M causes a marked reduction in the Ca efflux, no change in Ca influx and an increase in total Ca.4. Variation in internal or external Na concentration does not alter the Ca fluxes or concentrations. Application of cyanide or ouabain and alteration of external K concentration had no effect on the Ca fluxes.5. The sulphydryl reagents, ethacrynic acid and
N‐ethylmaleimide (NEM), have a rapid and marked effect on reducing the Ca efflux.6. L cell ghosts previously poisoned with DNP+IAA have a low Ca efflux. When ATP or CTP is incorporated into such cells the Ca efflux becomes normal.7. An extra amount of phosphate is produced by L cell ghosts when pumping Ca. This is equivalent to the splitting of 1·8 moles of ATP per mole of Ca pumped.8. It is concluded that L cells have a Ca pump driven by ATP, and that Na has no effect on Ca movements in these cells.
Effects of calcium and magnesium on the frequency of miniature end‐plate potentials during prolonged tetanization
Authors: Hurlbut W. P. , Longenecker H. B. , Mauro Alexander 
Published: December 2014

1. End‐plate potentials (e.p.p.s) and miniature end‐plate potentials (min.e.p.p.s) were recorded intracellularly from the cutaneous pectoris nerve‐muscle preparation of the frog during prolonged stimulation at low frequencies (5/sec—50/sec).2. When Ca was present in the bathing solution, the quantum content of the e.p.p. and the frequency of occurrence of the min.e.p.p.s gradually increased during the period of stimulation. During the first few minutes of stimulation, the min.e.p.p. frequency increased linearly with time, and the rate of increase was dependent on the Ca concentration of the bathing solution. However, Mg had no effect on this Ca‐dependent increase in min.e.p.p. frequency.3. A large maintained increase in min.e.p.p. frequency also occurred during prolonged stimulation in solutions that contained no added Ca and 1‐2 m
M‐EGTA. Under these conditions the increase in min.e.p.p. frequency was dependent on the Mg concentration of the bathing solution and was exponential in time.4. It is suggested that the rise in min.e.p.p. frequency is caused by an accumulation of Ca or Mg ions in the nerve terminal, and it is suggested that these ions enter the terminal at relatively non‐specific sites distinct from the Ca‐specific sites that trigger the ‘phasic’ release of transmitter.
The effect of metal ions and antidiuretic hormone on oxygen consumption in toad bladder
Authors: Cuthbert A. W. , Wong P. Y. D. 
Published: December 2014

1. The sodium‐dependent oxygen consumption of pieces of toad bladder (Bufo marinus) has been investigated using an oxygen electrode.2. The effect of polyvalent cations (Ca2+, Sr2+, Mg2+, Eu3+, La3+ and Mn2+) on sodium‐dependent oxygen consumption has been measured. All cations inhibited oxygen consumption, the order of effectiveness being Ca2+ > Sr2+ > Mg2+ > Mn2+ > Eu3+ > La3+.3. Treatment of bladder pieces with antidiuretic hormone (50 m‐u./ml.) decreased the effectiveness of Ca2+ and Sr2+ as inhibitors of sodium‐dependent oxygen consumption. Mn2+, Eu2+ and La2+ were more effective after hormonal treatment, while the effectiveness of Mg2+ was unaltered.4. The results have been interpreted in terms of a model in which sodium entry to the transporting mechanisms of the epithelium is controlled by Ca2+, and in which antidiuretic hormone alters Ca2+ binding and so affects sodium transport.
Na and Ca components of action potentials in amphioxus muscle cells
Authors: Hagiwara S. , Kidokoro Y. 
Published: December 2014

1. The ionic mechanism of the action potential produced in lamella‐like muscle cells of amphioxus, Branchiostoma californiense, was investigated with intracellular recording and polarization techniques.2. The resting potential and action potential overshoot in normal saline are −53±5 mV (
S.D.) and +29±10 mV (
S.D.) respectively.3. The action potential is eliminated by tetrodotoxin (3 μ
M) and by replacing NaCl in the saline with Tris‐chloride but maintained by replacing Na with Li.4. After elimination of the normal action potential by tetrodotoxin or replacing Na with Tris, the addition of procaine (7·3 m
M) to the external saline makes the membrane capable of producing a regenerative potential change.5. The peak potential of the regenerative response depends on external Ca concentration in a manner predicted by the Nernst equation with Ca concentrations close to normal.6. The Ca dependent response is reversibly suppressed by Co or La ions.7. Similar regenerative responses are obtained when Ca is substituted with Sr or Ba.8. It is concluded that two independent mechanisms of ionic permeability increase occur in the membrane of amphioxus muscle cell, one to Na and the other to Ca.
Sodium transport by perfused giant axons of Loligo
Authors: Baker P. F. , Foster Rachel F. , Gilbert D. S. , Shaw T. I. 
Published: December 2014

The sodium efflux from perfused squid giant axons has been studied using radioactive sodium, and the sufficient conditions for the maintenance of a potassium‐ and ouabain‐sensitive sodium efflux have been established. The following were found.1. Axons extruded and then perfused with their own axoplasm had a sodium efflux which was sensitive to cyanide, potassium and ouabain and was thus similar to the efflux from intact axons.2. A method for replacing natural axoplasm into fibres previously perfused with artificial axoplasm was developed and used to establish an artificial perfusate that was not irreversibly toxic.3. Short perfusion (5 min) with a variety of artificial perfusates was then found to give fibres which had potassium‐ and ouabain‐sensitive sodium effluxes when ATP was present in the perfusate.4. In the absence of ATP the sodium efflux was small and relatively insensitive to both external potassium and to ouabain.5. With ADP in the perfusate, fibres gave a sodium efflux which was ouabain‐sensitive but was little affected by the removal of external potassium from the sodium‐rich sea water bathing the fibres.6. The perfused fibres differed from intact fibres in having large ouabain‐insensitive sodium effluxes.7. After very long perfusions (40–90 min), with the simple media containing ATP, the rate constant for sodium efflux from the fibres tended to be large and was relatively insensitive to potassium or to ouabain.8. Fibres refilled with natural axoplasm after long perfusion showed increased sensitivity to external potassium; refilled with dispersed axoplasm the sodium efflux tended to become very large.9. After very long perfusions with artificial axoplasms containing ATP, a potassium‐ and ouabain‐sensitive sodium efflux was found to persist provided that dextran was present and the total osmotic pressure and the hydrostatic pressure of the perfusate were controlled. Under these conditions the sodium efflux resembled that from briefly perfused fibres.The necessary and sufficient conditions for the maintenance of sodium transport by perfused giant axons are discussed.
Interaction effects of visual contours on the discharge frequency of simple striate neurones
Authors: Bishop P. O. , Coombs J. S. , Henry G. H. 
Published: December 2014

1. The discharge frequency of simple neurones in the cat striate cortex responding to the two edges of a slit of light moving over their receptive fields was studied as a function of slit width. While one edge of the slit was discharging the cell, the other edge had a modifying influence on that discharge either by way of facilitation or of inhibition.2. The most common form of the curve relating discharge frequency and slit width had a maximal discharge at narrow slit widths (< 0·5°) and relative inhibition at medium widths (between 0·5° and 2°). At greater slit widths there was usually a region of facilitation before the effects of the two edges became independent of one another. Three other response patterns to slits of different width are described.3. The curve relating slit width and response amplitude for a particular cell provides an important clue to the various activity profiles for that cell. An activity profile plots the excitability of a cell along a line through the receptive field in the direction of stimulus movement. Each type of edge, light and dark, has its own set of activity profiles which differ depending upon stimulus parameters such as the direction of the movement of the edge.4. Two other methods were used to provide further data concerning the activity profiles and as a check on the evidence provided by the responses to slits of different width. One of these two methods used the test stimulus against the background of an artificially produced maintained discharge and the other involved the interaction of the two receptive fields of binocularly activated cells.5. A model is put forward to explain the receptive field organization of simple striate neurones which takes into account not only the main features of what is known concerning the synaptology of the visual cortex but also the new data provided by the present paper and the one which precedes it.
Amino acids and presynaptic inhibition in the rat cuneate nucleus
Authors: Davidson N. , Southwick C. A. P. 
Published: December 2014

1. Presynaptic inhibition was evoked in the rat cuneate nucleus by a peripheral conditioning stimulus. The dicarboxylic amino acid salts glutamate and aspartate and the neutral amino acids glycine and γ‐aminobutyric acid (GABA) were topically applied to a restricted area of the cuneate nucleus and their effects on both resting primary afferent terminal excitability and the increase in excitability of afferent terminals during presynaptic inhibition determined.2. Aspartate had no effect on either resting primary afferent terminal excitability or on the increase in excitability during presynaptic inhibition.3. Glycine reduced both resting primary afferent terminal excitability and presynaptic inhibition.4. Glutamate increased both resting primary afferent terminal excitability and presynaptic inhibition while GABA increased resting primary afferent terminal excitability but reduced the increase in excitability during presynaptic inhibition.5. The convulsant alkaloids picrotoxin (given intravenously) and bicuculline (topically applied) blocked presynaptic inhibition. The blocking action of picrotoxin was overcome by topical application of GABA but not glutamate.6. Simultaneous measurement of pre‐ and post‐synaptic excitability in the cuneate nucleus showed that while glutamate increased excitability at both sites, GABA increased primary afferent terminal excitability but depressed post‐synaptic excitability.7. It is concluded that glycine and glutamate exert non‐specific actions on primary afferent terminals similar to their effects at post‐synaptic sites elsewhere in the
C.N.S. while GABA depolarizes primary afferent terminals by a specific action at the same receptor site as the presynaptic inhibitory transmitter. The possibility is discussed that the presynaptic inhibitory transmitter in the cuneate nucleus is GABA or a closely related substance.
Fatigue of maintained voluntary muscle contraction in man
Authors: Stephens J. A. , Taylor A. 
Published: December 2014

1. The mechanism of fatigue has been studied in maintained maximal voluntary contractions of the first dorsal interosseous muscle of the hand.2. Fatigue occurs in two phases. In the first, lasting 1 min, force falls to about 50%. The smoothed rectified e.m.g. (s.r.e.) falls with the same time course and the normal linear relation between s.r.e. and force of unfatigued muscle is preserved.3. In the second phase, force falls relatively faster than s.r.e.4. Arterial occlusion does not affect the first phase, but in the second phase causes force to fall to zero, whereas without occlusion it tends to stabilize at about 25%.5. The size of the synchronous muscle action potential evoked by ulnar nerve stimulation falls to about 65% of normal, most of this fall occurring in the first phase.6. During recovery after prolonged fatigue, the relation between force and s.r.e. is changed for weak voluntary contractions much more than for strong ones, such that force is less for a given s.r.e. than normal.7. These results are interpreted as evidence that, in a maximal voluntary contraction, neuromuscular junction fatigue is most important at first, but later, contractile element fatigue increases, particularly when the blood supply is obstructed.8. Neuromuscular junction fatigue is believed to be most marked in high threshold motor units, while contractile element fatigue more especially affects low threshold units.
Re‐investigation of the effect of adrenaline and noradrenaline on renal function in situ
Authors: Liang C. C. , Yang Mabel M. P. 
Published: December 2014

1. Adrenaline or noradrenaline in single doses (0·01–0·10 μg/kg) or by continuous infusion (0·3–3·0 μg.kg−1 min−1) into anaesthetized dogs has been administered by different routes. The changes in femoral arterial
B.P., hepatic portal venous pressure, renal venous pressure, intrarenal venous pressure, kidney volume, renal plasma flow (RPF), glomerular filtration rate, urine flow and plasma protein concentration have been followed. The effects varied with route of administration, with dose and time.2. Direct injection of single doses of these drugs (≤ 0·02 μg/kg) into the renal artery reduced RPF and urine flow without affecting the systemic
B.P. or hepatic portal venous pressure.3. When the catecholamines were administered in single small doses (≤ 0·02 μg/kg),
I.M. or
S.C. or via the hepatic or common carotid arteries, only a slight effect on systemic
B.P. was observed. There was little effect on hepatic portal venous pressure, and no diuresis was observed.4. Single injection of these drugs (≤ 0·02 μg/kg) into the mesenteric artery caused an immediate fall of hepatic portal venous pressure without a direct effect on the kidney. A subsequent rise in hepatic portal venous pressure was associated with an increase in urine flow.5. Administration of these drugs (0·01–0·10 μg/kg) into the femoral vein, inferior vena cava or internal jugular vein caused a great rise in systemic
B.P., a decrease in hepatic portal venous pressure and an antidiuresis, but this was usually followed by a rise of hepatic portal venous pressure and by an associated diuresis, as systemic
B.P. returned to normal values.6. The total and segmental renal vascular resistance were calculated from parameters measured during ureteral occlusion. The primary effect of the catecholamines was to increase the resistance in all renal vascular segments and produce antidiuresis; subsequently a drastic drop of all segmental resistances occurred and this was accompanied by a diuresis.7. After block of the α‐adrenergic receptors by dibenzyline or ergotamine, manipulations which increased the hepatic portal venous pressure could still evoke an immediate reflex diuresis.8. Since the primary renal effect of catecholamines is a vasoconstriction and antidiuresis, it seems that the subsequent reduction of the renal vascular resistance and the associated diuresis is caused by some other mechanism.9. It is concluded that the complex effects of catecholamine on renal function represent the resultant of direct intrarenal together with indirect extrarenal actions and that the relative significance of these various actions depends on dose, time and the route of administration.
The influence of deep body temperatures and skin temperatures on respiratory frequency in the pig
Authors: Ingram D. L. , Legge K. F. 
Published: December 2014

1. The influences on respiratory frequency of ambient temperature, the temperature of the skin, the temperature and humidity of the inspired air, hypothalamic temperature, the temperature of the spinal cord, rectal temperature and some temperatures in the abdomen have been studied in the pig.2. At a constant ambient temperature the effect on respiratory frequency of heating a thermode in the hypothalamus was modified by the temperature of the skin of the trunk which was varied independently by means of a temperature‐controlled coat. A cold skin inhibited panting; a warm skin enhanced panting. The effect of heating a thermode over the spinal cord was similarly modified by skin temperatures.3. Simultaneous heating of thermodes in the hypothalamus and spinal cord increased respiratory frequency more than heating either alone, and in a warm environment the rectal temperature influenced the extent to which respiratory frequency increased on heating the thermodes.4. Cooling the thermodes decreased respiratory frequency in a warm environment and the cooling of one thermode enhanced the effect of cooling the other.5. At a constant trunk skin temperature the effect on respiratory frequency of heating the thermode in the hypothalamus depended on ambient temperature.6. Changing the temperature of thermodes in the abdomen did not affect respiration nor was there any evidence that the temperature and humidity of the inspired air had a direct effect on respiration.
The temperature dependence of activation by phosphatidylserine of the sodium pump adenosine triphosphatase
Authors: Priestland R. N. , Whittam R. 
Published: December 2014

1. Treatment of rabbit brain homogenates with deoxycholate reduced ouabain‐insensitive ATPase sixfold and subsequently adding phosphatidylserine had no effect. Ouabain‐sensitive ATPase was made entirely latent but it was fully restored on adding phosphatidylserine.2. Temperature and pH were varied to see if the reconstituted system resembled that in the original membranes. Linear Arrhenius plots were always obtained with the homogenate, and the activation energy was higher for the ouabain‐sensitive than for the ouabain‐resistant enzyme.3. A break at about 15° C was found in the Arrhenius plot of the reconstituted enzyme, but there was no break without added phosphatidylserine or when ouabain was added. The break suggests that the conformation and catalytic activity of the enzyme protein depended on the physical state of phosphatidylserine.
Regional distribution of cardiac output in young lambs: effect of cold exposure and treatment with catecholamines
Authors: Alexander G. , Bell A. W. , Setchell B. P. 
Published: December 2014

1. Lambs less than 3 days old, exposed to thermoneutral or intensely cold conditions in a respiration chamber, were infused with adrenaline or noradrenaline, 1 or 10 μg/kg.min; and the effects on oxygen consumption, cardiac output and its distribution to skin, skeletal and cardiac muscle, liver, spleen, kidney, gut, brown adipose tissue and brain were determined. Cardiac output was estimated by the Fick and dye dilution methods and the distribution of cardiac output by Sapirstein's method of fractional distribution of indicators.2. Under thermoneutral conditions, metabolic rate was stimulated by both doses of noradrenaline and by the low, but not the high dose of adrenaline. Under cold conditions, the low dose of catecholamines had little effect on the already elevated metabolic rate, but the high doses depressed the metabolic response to cold.3. The low dose of adrenaline increased cardiac output under thermoneutral conditions whereas the high dose decreased cardiac output; the effects of noradrenaline were less marked, in contrast to reported effects in new‐born rabbits. The low doses of catecholamine given under cold conditions had little effect on the already elevated cardiac output, but the high doses, particularly of adrenaline, decreased cardiac output.4. Blood flow through the skin of the extremities was markedly reduced by cold exposure, while flow through the peri‐renal fat was doubled, flow through the skeletal muscle was quadrupled and flow through the cardiac muscle was trebled. These increases, particularly in skeletal muscle, were due to increased cardiac output and to vasodilation, as indicated by the reduced ratio of blood pressure to blood flow. Results are contrasted with published reports that blood flow through brown fat in new‐born rabbits was greatly increased by cold, but muscle flow was scarcely altered.5. In almost all organs examined the high doses of adrenaline infused in either environment markedly reduced blood flow, presumably by generalized vasoconstriction. Changes due to noradrenaline were small under thermoneutral conditions and flow through brown fat was increased by only 60% during infusion of 10 μg/kg.min. Much greater increases have been reported in new‐born rabbits. Under cold conditions the high doses of noradrenaline tended to decrease flow in most organs including brown fat and muscle.6. The results provide likely explanations for published reports that adrenaline failed to stimulate non‐shivering thermogenesis or suppressed the mobilization of metabolites and the metabolic response to cold.
The surface area of sheep cardiac Purkinje fibres
Authors: Mobley Bert A. , Page Ernest 
Published: December 2014

1. Measurements combining the techniques of point counting and line integration were performed on light and electron micrographs of Purkinje fibres from the sheep's heart. The measurements were aimed at determining membrane areas of importance for the cellular electrophysiology of this tissue.2. The mean volume fractions of the cells occupied by various constituents were: myofibrils, 0·234; mitochondria, 0·103; and nuclei, 0·009. The mean volume fraction of the fibres occupied by the interspaces between the tightly packed cells was 0·0023.3. The mean fractions of intercellular surface area occupied by junctional specializations were: nexus, 0·17; desmosome, 0·023; and fascia adherens, 0·014.4. The mean surface to volume ratio of the Purkinje cells and fibres was 0·46 μ−1 which is 11·5 times the value of the surface to volume ratio of a long right circular cylinder 100 μ in diameter.5. There are two reasons for the increment in the surface to volume ratio of the fibre (when compared to that of a long right circular cylinder 100 μ in diameter): the multicellular composition of the fibres and the extensive folding of the surface of the cells.6. After correction for the intercellular nexal area the surface to volume ratio of a long cylindrical fibre 100 μ in diameter was 0·39 μ−1, or about 10 times the value for a long right circular cylinder 100 μ in diameter. The surface to volume ratio of the tissue interspaces in the same fibre was 170 μ−1.7. It was concluded that the total sarcolemmal area in this tissue is great enough so that the specific membrane capacitance could be about 1 μF/cm2 and the specific membrane resistance 20,000 Ω cm2.