bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of the electrical excitability of aorta smooth muscle of rabbit
Authors: Mekata F. 
Published: December 2014

1. Electrical records were made from the smooth muscle of rabbit aorta in normal solution and after excitation by noradrenaline, by the partitioned chamber method.2. Noradrenaline (3 × 10−7 g/ml.) produced depolarization and periodic slow potentials, the amplitudes of which were decreased by depolarizing currents and increased by small hyperpolarizing currents. Application of strong hyperpolarizing current stopped production of the slow potentials.3. After application of small amounts of noradrenaline, electrical stimulation produced slow potentials.4. Membrane resistance at the top of the slow potential induced by noradrenaline (3 × 10−7 g/ml.) was decreased to a few percent of the stable potential level during application of noradrenaline.5. The voltage—current relationship of smooth muscle cells in the aorta showed marked cathodal rectification both in standard solution and upon the application of noradrenaline.6. High K (24 m
M) elicited periodic slow potentials, the electrical properties of which were very similar to those induced by noradrenaline. Phentolamine (5 × 10−5 g/ml.) and guanithidine (10−5 g/ml.), however, blocked the production of these slow potentials.7. The conditions required for the production of slow potentials are discussed.8. Evoked slow potentials by current flow during application of noradrenaline (3 × 10−7 g/ml.) was recorded at 5 mm from the stimulating partition. Thus it is concluded that the slow potential can be conducted.
A study of the role of renal nerves in the renal responses to 60° head‐up tilt in the anaesthetized dog
Authors: DiBona G. F. , Johns E. J. 
Published: December 2014

1. Renal responses to 10 min of 60° head‐up tilt were measured in anaesthetized dogs in which renal perfusion pressure was maintained at a relatively constant value.2. Tilting was associated with a fall in systemic blood pressure and an increase in heart rate. Renal blood flow and glomerular filtration rate remained constant while there was a significant decrease in both absolute and fractional excretion of sodium.3. Animals which had undergone acute renal denervation were tilted. The cardiovascular responses were similar to intact animals. A fall in renal blood flow was observed but the glomerular filtration rate was maintained at a steady value during tilting. The decreased renal tubular excretion of sodium measured in intact animals was abolished.4. Alpha‐adrenergic blockade of the kidney was achieved by infusion of phentolamine into the renal artery. Tilting of these animals caused cardiovascular changes similar to those observed in control animals but renal blood flow, glomerular filtration rate and sodium handling remained unchanged.5. Animals in which both carotid sinuses had been acutely denervated were tilted. Systemic blood pressure fell as in intact animals, but the rise in heart rate was significantly less. Renal blood flow, glomerular filtration rate and the rate of sodium excretion were unchanged.6. A 10 min period of 60° head‐up tilt in anaesthetized dogs resulted in an unchanged renal blood flow and glomerular filtration rate which was associated with a decrease in both fractional excretion of sodium and sodium excretion. The renal sympathetic nerves were shown to be responsible for these changes in tubular sodium handling which appeared to exert their action via renal tubular α‐adrenergic receptors. This activation of the renal nerves appeared to be mediated by the carotid sinus baroreceptor reflex.
The effects of vanadate on the fluxes of sodium and potassium ions through the sodium pump
Authors: Beaugé L. A. , Cavieres J. J. , Glynn I. M. , Grantham J. J. 
Published: December 2014

1. The effects of sodium orthovanadate on the fluxes of sodium and potassium (or rubidium) ions through the sodium pump have been investigated in intact human red cells and in resealed ghosts prepared from them. Sodium—potassium exchange, potassium—potassium exchange, pump reversal, sodium—sodium exchange and uncoupled sodium efflux have each been studied.2. When intact human red cells were incubated in high‐sodium media containing vanadate in low concentrations, inhibition of potassium or rubidium influx was marked only if the potassium or rubidium concentration in the medium was sufficiently high to cause nearly maximal influx in the absence of vanadate. The absence of inhibition at lower potassium or rubidium concentrations cannot be explained by supposing that the onset of inhibition by vanadate is slower in these conditions.3. Lowering the extracellular sodium concentration, or raising the vanadate concentration, decreased the minimum concentration of extracellular potassium or rubidium at which inhibition by vanadate was detected.4. Experiments on potassium influx into intact red cells treated with the ionophore A23187 showed that magnesium ions act at intracellular sites to promote inhibition by vanadate.5. Measurements of potassium efflux from intact red cells incubated in high‐sodium media, with or without potassium, showed that potassium—potassium exchange was inhibited by vanadate at low concentrations whereas reversal of the pump was not.6. Measurements of sodium efflux from intact red cells or resealed ghosts incubated in high‐sodium media, with or without potassium, showed that vanadate had little or no effect on sodium—sodium exchange at concentrations at which sodium—potassium exchange was markedly reduced. Much higher concentrations of vanadate did cause partial inhibition of sodium—sodium exchange.7. Experiments to determine whether vanadate in low concentrations inhibited uncoupled sodium efflux were inconclusive, but suggested that the flux was inhibited. Measurements of the ATP hydrolysis that is thought to be associated with the uncoupled sodium efflux showed that this hydrolysis was strongly inhibited.8. The different effects of vanadate on the different fluxes are discussed, and related to the way in which vanadate is thought to act on the sodium pump.
Lateral contacts and interactions of horizontal cell dendrites in the retina of the larval tiger salamander
Authors: Lasansky A. 
Published: December 2014

1. The contacts of horizontal cell dendrites with processes of other second order neurones were studied at the level of the electron microscope in serial sections of the salamander retina. Intracellular recordings of the responses to light of horizontal and bipolar cells were used to investigate the possible significance of some of the morphological findings.2. Horizontal cell dendrites make close membrane appositions (gap junctions) with one another and are post‐synaptic to bipolar cell dendrites at presumed chemical synapses. On the other hand, there is no clear evidence that horizontal cell dendrites are presynaptic to any other neuronal processes at the outer plexiform layer, so that the output connexions of horizontal cell bodies remain a matter of speculation.3. It is suggested that the bipolar cell input and the gap junctions between dendrites contribute, respectively, depolarizing and hyperpolarizing components to the responses of horizontal cell bodies to surround illumination. In addition, the facilitatory effect of central illumination on the surround response of horizontal cell bodies may result, although perhaps only partly, from observed properties of the surround response of bipolar cells.4. In the course of these observations, bipolar cells were found to be presynaptic at the outer plexiform layer not only to horizontal cell dendrites, but also to other bipolar cells, horizontal cell axon terminals and certain processes belonging to an as yet unidentified neurone.
Dual mode of junctional transmission at synapses between single primary afferent fibres and motoneurones in the amphibian
Authors: Shapovalov A. I. , Shiriaev B. I. 
Published: December 2014

1. The isolated hemisected frog spinal cord has been used to examine the effects of changes in ionic composition of perfusing medium on the intracellularly recorded e.p.s.p.s produced in single motoneurones by direct stimulation of individual dorsal root fibres through a separate intracellular micro‐electrode.2. The monosynaptic single‐fibre e.p.s.p.s usually reveal two distinct components, early and late. The early component is resistant to replacement of external Ca2+ by Mn2+ whereas the later is reversibly abolished. It is concluded that the junction between primary afferent fibre and motoneurone provides joint electrical and chemical transmission.3. The average amplitude of the unitary electrical e.p.s.p. varies at different junctions from 25 to 430 μV, mean 124 ± 17 μV (n = 50). It is relatively stable and changes its amplitude only with changes in the height of presynaptic spike. The individual amplitudes observed in a given cell usually have a normal distribution suggesting that any variability in electrical response is entirely due to noise.4. The average amplitude of the single‐fibre chemically mediated e.p.s.p. varies from less than 20 μV to 1·7 mV, mean 222 ± 33 μV (n = 71). A positive correlation was found between the amplitudes of chemical and electrical e.p.s.p.s recorded from different motoneurones.5. Chemical e.p.s.p.s evoked by consecutive impulses in a single presynaptic fibre show statistical fluctuations in amplitude. The fluctuations occur in quantal steps in a manner described by binomial or Poisson statistics. Only in a few cases the deviation from stochastic distribution can be attributed to variable invasion of nerve impulses into the terminal region.6. The amplitude of the unit e.p.s.p. varies between 33 and 104 μV, mean 66·4 ± 4·3 μV (n = 19). The mean quantum content (m) varies from less than 1 to more than 10. The m is reversibly reduced by Ca2+ lack and by Mn2+ until the chemically mediated response fluctuates according to a Poisson distribution with the unit e.p.s.p. equivalent to the single quantum of transmitter.7. When paired or repetitive stimuli are applied to the presynaptic fibre the facilitation of the chemically mediated unitary e.p.s.p. can be observed as well as the post‐tetanic potentiation. The amplitude of the electrical e.p.s.p. remains unchanged during the period of post‐tetanic potentiation, suggesting that the latter is attributable to some change restricted to the specific presynaptic mechanism responsible for the transmitter release but not to changes in presynaptic spike height.
The role of muscle mass in the cardiovascular response to static contractions
Authors: Mitchell J. H. , Payne F. C. , Saltin B. , Schibye B. 
Published: December 2014

1. Eleven men performed static contractions with the fingers (digits II and III), forearm (handgrip) and the knee extensors (knee angle 90°) at 40% maximal voluntary contraction (MVC) for 2 min. In seven of the subjects handgrip and knee extension were combined, both contractions held at 40% MVC. At the end of the contraction, cuffs were inflated to 250 mmHg for 3 min around the extremity which had been contracting. Continuous measurements were performed of force, heart rate and intra‐arterial blood pressure (a. brachialis; 20 cm proximally), before and during contraction as well as during the recovery with and without cuffs inflated.2. Heart rate and blood pressure increased momentarily with the onset of a contraction whereafter a gradual further increase took place. This pattern of response was similar for all muscle groups studied. The increases during the contractions were in the order: fingers, forearm, knee extensors and combined forearm—knee extensors, with the difference between each muscle group contraction being significant.3. In the recovery period from a contraction with the cuff(s) inflated, heart rate returned to control level. Blood pressure also dropped, but remained elevated above pre‐contraction level until the cuff(s) was released.4. The present data during contraction are at variance with earlier observations showing that the cardiovascular response to a static contraction is proportional to the% MVC regardless of the muscle mass involved in the contraction. Our findings are in line with the traditional concept of central and peripheral nervous inputs playing a role in the cardiovascular adjustments to exercise, with both the central and the peripheral factors being related to the mass of the muscles engaged in the exercise.
Variety of functional organization within the monkey motor cortex
Authors: Lemon R. N. 
Published: December 2014

1. Single‐unit recordings have been made from 606 neurones in the arm region of area 4 in five conscious monkeys. Their activity during a stereotyped motor task and their responses to passive natural stimulation of the limb have been investigated.2. 88% of area 4 neurones responsive to natural stimulation received their afferent input from a restricted region of the contralateral arm.3. The activity and afferent input to cell groups have been determined by comparing the properties of neurones located within 500 μm of each other and recorded in one and the same micro‐electrode penetration. 115 such cell groups containing 344 neurones were investigated.4. 75/115 cell groups (65%) contained neurones with input from the same arm zone (shoulder, elbow, wrist or hand) and with a similar pattern of task‐related activity. Cell groups containing neurones with identical afferent inputs never showed contrasting behaviour during movement.5. 40/115 cell groups (35%) contained neurones receiving inputs from more than one arm zone. Twenty‐five cell groups (22%) had two contiguous zones (e.g. wrist and hand) represented and ten groups had input from two discontinuous zones (e.g. elbow and hand). These differences in input within a cell group were usually reflected in contrasting behaviour of its constituent neurones during movement.6. Pyramidal tract neurones (PTNs) lying immediately adjacent to one another usually received similar inputs and exhibited matching behaviour. PTNs lying further apart in the same penetration often showed different activity and responded to different stimuli.7. The topographic distribution of afferent input to area 4 revealed multiple representation of input from a single zone combined with considerable intermingling of input from all four zones. Neurones with shoulder and elbow inputs surrounded those with wrist inputs which in turn lay scattered around a central zone. This central zone only contained neurones with hand inputs, although neurones with hand inputs were found outside this central zone.8. The significance of this complex organization is discussed in terms of motor cortex input and output.
The effect of local anaesthetics on strophanthidin toxicity in canine cardiac Purkinje fibres
Authors: Bhattacharyya M. L. , Vassalle M. 
Published: December 2014

1. Canine Purkinje fibres were superfused in vitro and the electrical and mechanical effects of the local anaesthetics benzocaine and procaine were studied in the absence and in the presence of other agents.2. Both benzocaine (1 × 10−4‐5 × 10−4
m) and procaine (6 × 10−5‐2·5 × 10−4
m) decreased slightly the amplitude of the upstroke and markedly the duration of the action potential. The plateau was shifted to more negative values and the force of contraction was decreased. These effects were dose‐dependent.3. The local anaesthetics abolished the spontaneous activity induced by strophanthidin (5 × 10−7
m) by flattening the oscillatory potential in diastole and increased the force of contraction under these circumstances.4. The local anaesthetics significantly delayed the time of the onset of the spontaneous activity induced by strophanthidin (10−6
m). Also, the intensity of the stimuli had to be increased and the rate of discharge of intoxicated fibres was slower in the presence of local anaesthetics. In contrast, the positive inotropic effect was little affected.5. The local anaesthetics reduced but did not block the inotropic action of norepinephrine and high Ca; and did not abolish (while Mn did) small action potential in 27 m
m‐K‐depolarized fibres.6. In fibres treated with local anaesthetics, lowering [Ca]o did not result in a force rebound and administration of caffeine or exposure to low Na resulted in a larger increase in force.7. In fibres loaded with Ca, local anaesthetics caused an increase in force.8. Local anaesthetics decreased the force more when the external Na concentration was lower.9. This work shows that the local anaesthetics alter the mechanical performance of Purkinje fibres and lead to a depression of the strophanthidin induced oscillatory potential. As for the mechanism for these changes, the present experiments support the hypothesis that local anaesthetic agents have an antiarrhythmic action by decreasing intracellular Na and therefore intracellular Ca as suggested by Perry, McKinney & DeWeer (1978) on the basis of experiments on nerve.
Sidedness of the effects of sodium and potassium ions on the conformational state of the sodium—potassium pump
Authors: Karlish S. J. D. , Pick U. 
Published: December 2014

1. (Na,K)ATPase from kidney membranes has been reconstituted into proteoliposomes following solubilization in cholate, by the freeze—thaw sonication procedure described by Kasahara & Hinkle (1977). The method is rapid and convenient.2. Upon addition of ATP to the exterior medium the reconstituted vesicles sustain high rates of active 22Na uptake and 86Rb efflux with many properties similar to those of the Na/K pump in well characterized cells such as erythrocytes.3. Observations on both active and passive transport of 22 Na and 86Rb indicate that the vesicle population is heterogeneous; about 40 per cent contain Na/K pumps and the remainder seem to be plain lipid vesicles.4. The major Na+‐ or K+‐stabilized non‐phosphorylated conformational forms of the (Na, K)ATPase, E1. Na and E2. (K) respectively, have been investigated in the proteoliposomes, with particular regard to sidedness of the actions of Na+ and K+.5. Tryptic digestion of the vesicles reveals the Na+‐ and K+‐stabilized conformations E1. Na and E2. (K) as characterized originally for purified (Na, K)ATPase (Jørgensen, 1975). Controlled trypsinolysis of Tris+‐loaded vesicles in a Na+‐or K+‐containing medium leads to typical biphasic (Na+) or simple exponential (K+) time courses respectively, for loss of ATP‐dependent 22Na uptake (assayed subsequent to the tryptic digestion in the presence of inophores valinomycin plus FCCP). Tryptic digestion of K+‐ or Rb+‐ or Tris+‐loaded vesicles suspended in a Na+ medium results only in the biphasic (E1. Na) pattern of loss of ATP‐dependent 22Na uptake.6. ATP‐dependent 22Na uptake and 86Rb efflux are reduced by about the same extent following a short tryptic digestion in a Na+‐containing medium.7. Vanadate ions inhibit ATP‐dependent 22Na uptake into the vesicles, at low concentrations (K0·5 ∼ 2 × 10−7
m), following pre‐incubation together with Mg2+ and K+ ions. K+ ions in the medium are effective, K+ ions within the vesicle are not. Na+ ions in the medium prevent inhibition by vanadate+Mg2+ but do not reverse inhibition in vesicles pre‐incubated with vanadate, Mg2+ and K+ ions.8. The results show that the conformational forms E1. Na and E2. (K) are stabilized by Na+ or K+ ions respectively, bound to sites on the Na/K pump normally facing the cytoplasm. The significance of this finding is discussed in relation to the cation transport function of the pump.
The effects of ATP on the interactions between monovalent cations and the sodium pump in dialysed squid axons
Authors: Beaugé Luis , Di Polo Reinaldo 
Published: December 2014

1. The efflux of Na in dialysed axons of the squid has been used to monitor the sidedness of the interactions of the Na pump with Na+ ions, K+ ions and ATP. The axons were under conditions such that most of the Na efflux went through the Na pump by means of a complete cycle of ATP hydrolysis.2. With 310 m
m‐Ki+, 70 m
m‐Nai+ and 10 m
m‐K+ artificial sea water (ASW) more than 97% of the Na efflux was abolished by removal of ATP. The efflux of Na was stimulated by ATP with a K½ of about 200 μ
m. This is similar to the K½ of 150 μ
m found for the ATP dependence of a ouabain‐sensitive Na,K‐ATPase activity in membrane fragments isolated from squid optical nerves.3. A 100‐fold reduction in the ATP concentration (from 3‐5 m
m to 30‐50 μ
m) increased the apparent affinity of the Na pump for Ko+ about 8‐fold. In addition, the maximal rate of Ko+‐stimulated Na efflux was reduced by a similar factor. Analogous results were seen in axons dialysed with 310 m
m‐Ki+ or without Ki+.4. The relative effectiveness of external monovalent cations as activators of the Na efflux was a function of the ATP concentration inside the axon. With 3‐5 m
m‐ATP the order of effectiveness was K+ > NH4+ > Rb+. With 30‐50 μ
m‐ATP the sequence was NH4+ » K+ » Rb+. These results were not affected by the removal of Ki+.5. When the ATP concentration was 3 m
m and the Nai+ concentration 70 m
m, the removal of Ki+ produced a slight and reversible increase in the total efflux of Na (15%) and no change in the ATP‐dependent Na efflux. When the ATP concentration was reduced to 30‐50 μ
m, or the Nai+ concentration lowered to 5‐10 m
m, the removal of Ki+ reversibly increased the total and the ATP‐dependent efflux of Na. The largest increase in Na efflux was seen when both ATP and Nai+ were simultaneously reduced. The ATP‐dependent extra Na efflux resulting from the exclusion of Ki+ was abolished by 10−4
m‐ouabain in the sea waters.6. The increase in the ATP‐dependent Na efflux observed in axons dialysed with 0 Ki+ + 10 m
m‐K+ ASW was not seen in axons perfused with 310 m
m‐Ki+ + 450 m
m‐K+ ASW. However, both experimental conditions gave rise to a similar (and small) ATP‐independent and ouabain‐insensitive efflux of Na. This indicates that the effects on the Na pump of removing Ki+ are not due to the simultaneous membrane depolarization. In addition, it suggests that Ki+ has an inhibitory effect on the Na pump, and that that effect is antagonized by Nai+ and ATP.7. The present results are consistent with the idea that the same conformation of the Na pump (and Na,K‐ATPase) can be reached by interaction with external K+ after phosphorylation and with internal K+ before rephosphorylation. This enzyme conformation produces an enzyme—K complex from which K+ ions are not easily released unless high concentrations of ATP are present. This also stresses a non‐phosphorylating regulatory role of ATP.