bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of adenosine triphosphate in human plasma and the concentration in the venous effluent of forearm muscles before, during and after sustained contractions
Authors: Forrester T. , Lind A. R. 
Published: December 2014

1. When diluted human plasma is perfused through a frog heart, a marked augmentation of the heartbeat is produced which is very similar in action to that of low concentrations of adenosine triphosphate (ATP) on the heart.2. It was established that the substance in the plasma responsible for the heart stimulation was ATP. The following tests were used: (a) the diluted plasma emitted light from firefly lantern extract characteristic of the light signal produced by a solution of ATP; (b) the stimulatory effect on the frog heart and luminescent effect upon the firefly extract were abolished by incubation of the plasma solution with the enzyme apyrase, which converts ATP to adenosine monophosphate (AMP); AMP does not stimulate the heart or cause light to be emitted from firefly extract; (c) the stimulatory substance in the plasma was eluted through a column of Sephadex G‐25 in the same pattern as ATP; and (d) simultaneous assay of plasma solutions on frog heart and firefly extract produced the same quantitative result as that produced by a solution of ATP.3. The amount of ATP in plasma from the venous blood of resting subjects ranged from 0·19 to 0·95 μg/ml. (mean 0·63 μg/ml.,
S.D. ± 0·25); up to half of the ATP detected could be attributed to blood platelet damage. Simultaneous arterial and venous samples of blood from four subjects at rest had mean concentrations of 0·19 μg/ml. (0·07–0·26 μg/ml.) and 0·70 μg/ml. (0·57–0·84 μg/ml.) respectively.4. The concentration of ATP in the venous effluent from exercising forearm muscles was measured. The venous concentration consistently increased over the resting values in response to exercise while in one subject little change occurred in the arterial blood concentration during the exercise. It was concluded that the ATP was added to the blood in its passage through the muscle bed.5. The origin of the ATP, including erythrocytes, blood platelets and active skeletal muscle, is discussed.
Evidence that the secondary as well as the primary endings of the muscle spindles may be responsible for the tonic stretch reflex of the decerebrate cat
Authors: Matthews P. B. C. 
Published: December 2014

1. The size of the tonic stretch reflex of the soleus or gastrocnemius muscle of the decerebrate cat has been compared with the size of the reflex contraction elicited in the same muscle by high‐frequency vibration applied to its tendon.2. On the assumption that vibration preferentially excites the primary endings of the muscle spindles it may be used to estimate the relation between the reflex response and the frequency of the Ia input to the spinal cord. On this basis, the increase in tension evoked by increasing extension is too great to be explained by the increase in Ia input with extension previously found on single fibre recording in comparable preparations.3. When vibration was superimposed on stretch reflexes elicited by different extensions, the size of the additional contraction elicited by the vibration remained approximately constant. If the stretch and vibration reflexes both depended entirely upon the Ia pathway, then occlusion between them would have been expected instead of the simple summation which was found.4. The absence of occlusion was not due to variation of the contractile strength of the muscle with its extension. This was shown by finding that the reflex contraction of soleus produced by stimulating the medial gastrocnemius nerve also remained the same size when elicited at different lengths of the muscle.5. The reflex effects were studied of superimposing alternate stretches and releases of 0·2 mm, on extensions of several mm. The small stretches elicited responses which were larger than expected from the response to large stretches, and which were approximately the same size at different mean lengths of the muscle.6. It is concluded that the tonic stretch reflex of the decerebrate cat cannot readily be explained solely by the increase in Ia discharge produced by stretching, as usually believed. Instead, it is suggested that the group II afferent fibres from the secondary endings of the muscle spindle also play an important part in its production.
Potential differences between mother and foetus at different gestational ages in the rat, rabbit and guinea‐pig
Authors: Mellor David J. 
Published: December 2014

1. Potential differences associated with fluid compartments of rat, rabbit and guinea‐pig conceptuses have been measured. [Na+] and [Cl−] in maternal plasma and amniotic fluid from these three species were also determined.2. Transplacental potential differences of about 15 mV (foetus positive) were found in the rat, of approximately 0 mV in the rabbit, and of about 18 mV (foetus negative) in the guinea‐pig.3. Amniotic fluid potential differences appeared to arise indirectly from the transplacental potential difference in the rat, from the foetal gastric mucosa in the rabbit, and possibly from the foetal gastric mucosa and indirectly from the placenta in the guinea‐pig.4. The results are discussed in the context of Na+ transfer to the foetus, and on this basis tend to question the general assumption that almost all Na+ reaching the foetus passes across the placenta.
On the metabolic basis of nervous activity
Authors: den Hertog A. , Greengard P. , Ritchie J. M. 
Published: December 2014

1. A study has been made of the metabolic substrates that can support the active extrusion of sodium ions from mammalian non‐myelinated nerve fibres. The post‐tetanic hyperpolarization obtained in chloride‐free Locke solution, which reflects the electrogenic component of the sodium pump, was used as the index of metabolic activity.2. When glucose was removed from the Locke solution there was no immediate change in the size of the post‐tetanic hyperpolarization.3. However, glucose is essential for metabolism in nerve fibres; for when a competitive inhibitor, deoxy‐
D‐glucose, was added to the Locke solution the post‐tetanic response was much reduced or abolished. Larger concentrations of deoxy‐
D‐glucose were required in the presence of glucose than in its absence.4. This effect of deoxy‐
D‐glucose could be reversed by glucose, fructose, pyruvate and acetate.5. The depressant effect of deoxy‐
D‐glucose was enhanced by oxaloacetate and by malate.6. Malonate, a competitive inhibitor of the conversion of succinate to fumarate, reduced or abolished the post‐tetanic hyperpolarization.7. This effect of malonate could be overcome by glucose and by pyruvate.
Immunohistochemical localization of protein components of catecholamine storage vesicles
Authors: Geffen L. B. , Livett B. G. , Rush R. A. 
Published: December 2014

1. The distribution of specific proteins in sympathetic neurones has been examined by immunofluorescent histology using antibodies prepared against soluble protein components of the catecholamine storage vesicles of the adrenal medulla.2. Two antigen preparations were separated by ion exchange chromatography of the soluble proteins released on osmotic lysis of catecholamine storage vesicles which had been isolated by centrifugation from homogenates of sheep adrenal medulla. One fraction (AgDH) had high dopamine‐β‐hydroxylase activity, while another (AgCB), consisting of the bulk of the protein, had some capacity to bind catecholamines. On disk gel electrophoresis the antigens ran as single bands with very different mobilities.3. Antisera (AsDH) and (AsCB) produced in rabbits to the two antigens were shown to react specifically with their antigens by immunodiffusion and electrophoresis in agarose.4. Indirect immunofluorescent staining of tissue sections was achieved by layering first the rabbit anti‐sera, followed by goat anti‐rabbit globulin serum which had been conjugated with fluorescein isothiocyanate.5. The adrenal medulla and the cell bodies of sympathetic ganglia showed the most intense green fluorescence with the immune rabbit sera, and hardly stained when pre‐immune serum from the same animal was used. The reactivity of the antisera could be abolished by incubation with the corresponding antigen.6. The preterminal and terminal axons of sympathetic nerves also stained specifically but less intensely with both antisera. When the nerves were ligated for up to 24 hr, the portion immediately proximal to the constriction showed an enhanced reaction to the antisera.7. The results provide evidence that sympathetic neurones contain proteins immunologically identical to those involved in the synthesis and storage of noradrenaline in the adrenal medulla, and support the concept that granular vesicles are synthesized in the perikaryon of the neurone and are transported somatofugally in the axon.
Membrane currents underlying delayed rectification and pace‐maker activity in frog atrial muscle
Authors: Brown Hilary F. , Noble Susan J. 
Published: December 2014

1. A double sucrose gap method has been used to polarize and voltage clamp frog atrial muscle strips.2. In response to steady depolarizing currents, normally quiescent strips often show pace‐maker activity, and long lasting depolarization occurs when the current is terminated.3. Voltage clamp experiments reveal the presence of two current components underlying delayed rectification.4. The first of these components has a time constant which varies with potential and is approximately 500 msec at −90 mV. Its reversal potential usually lies between −70 and −40 mV and has always been found to be positive to the resting potential of normally quiescent fibres.5. The time constant of the second component is extremely slow (τ [unk] 5 sec at −90 mV). Its reversal potential is much more positive than that of the faster component.6. The results confirm the presence of a component of inward current which is insensitive to tetrodotoxin (TTX), having an activation threshold about 20 mV positive to the sodium threshold. This current differs from the two components underlying delayed rectification both in its greater speed of activation and in showing inactivation. The inactivation of this TTX‐insensitive current is also a fairly rapid process.7. It is suggested that pace‐making in sino‐atrial muscle may depend upon the deactivation of the faster component of delayed rectification and that the TTX‐insensitive inward current is also involved.
A quantitative analysis of the slow component of delayed rectification in frog atrium
Authors: Brown Hilary F. , Noble Susan J. 
Published: December 2014

1. The slow component of delayed rectification in the atrial muscle membrane of Rana ridibunda has been analysed quantitatively using a voltage‐clamp technique.2. It is shown that the current is proportional to a variable which obeys first‐order kinetics. At negative potentials the time constant of this process is very long (τ = 3 sec at −55 mV) but it becomes faster at positive potentials (τ = 1·85 sec at +25 mV).3. In the steady state the degree of activation is a sigmoid function of potential. The activation threshold varies substantially between preparations but is usually negative to −30 mV.4. The instantaneous current—voltage relation is nearly linear and its reversal potential most frequently lies between zero and −30 mV.5. The properties of this current system resemble those of the current system ix2 found in mammalian Purkinje fibres.
Interaction of 28Mg with Ca and K in the smooth muscle of guinea‐pig taenia coli
Authors: Sparrow M. P. 
Published: December 2014

1. The uptake of 28Mg, and the total tissue content of Mg, Ca, Na and K have been determined in the smooth muscle of the guinea‐pig taenia coli. The Mg content was 6·56 m‐mole/kg fresh wt. immediately after dissection, falling slowly to 5·11 after 6 hr immersion in Krebs solution at 37° C.2. The Mg content rose to 15·4 m‐mole/kg fresh wt. during immersion in isotonic sucrose containing only MgCl2. It was independent of the Mg2+ concentration in this solution, but was depressed when K+ or Ca2+ ions were added.3. 28Mg uptake showed three separate phases, extracellular, intermediate and slow. The size of the extracellular phase was proportional to the Mg2+ concentration in the solution, but the size of the slow phase was constant. The size of the intermediate phase, exchanging with a half‐time of a few minutes, was depressed when K+ or Ca2+ ions were added.4. The results are compatible with a competition between Mg in the intermediate phase of tracer exchange, and K+ or Ca2+ ions for fixed anionic sites in the tissue.
The activities and concentrations of sodium and potassium in toad oocytes
Authors: Dick D. A. T. , McLaughlin S. G. A. 
Published: December 2014

1. The activity of potassium, aK, in the cytoplasm of oocytes from the toad, Bufo bufo, as measured by potassium‐sensitive glass micro‐electrodes, was 82 m
M. The concentration of potassium, CK, in oocytes from the same ovaries, as determined by flame photometric analysis, was 113 m
M. The ratio aK/CK = 0·73 does not differ significantly from the measured activity coefficient of the normal Ringer bathing solution, which is 0·75.2. The activity of sodium, aNa, in the cytoplasm of toad oocytes, as measured by sodium‐sensitive glass micro‐electrodes, was 9·3 m
M. The concentration of sodium, CNa, in oocytes from the same ovaries, as determined by flame photometric analysis, was 25·8 m
M. The value of the aNa/CNa ratio in the cells, 0·36, is only about half the value of either the aK/CK ratio in the cells or the activity coefficient of sodium in the normal Ringer bathing solution. This implies that about half the sodium in the cell is sequestered in some manner, such that it is unavailable to affect a cation‐sensitive micro‐electrode.3. When the oocytes were bathed for 5 hr in a sodium‐free, lithium‐substituted, Ringer solution the aNa/CNa ratio decreased to 0·06–0·10. This drop in the aNa/CNa ratio implies that the sodium available to the cation‐sensitive micro‐electrode can leave the cell much faster than the sequestered sodium.
Sweat gland function of the donkey (Equus asinus)
Authors: Robertshaw D. , Taylor C. R. 
Published: December 2014

1. Donkeys sweat on exposure to heat and in response to intravenous adrenaline infusion.2. Thermal sweating was abolished by the adrenergic‐neurone blocking agent bethanidine but not by atropine.3. Sympathetic decentralization (by preganglionic sympathectomy) abolished thermal sweating but adreno‐medullary denervation had no effect.4. Exercise resulted in sweating from both sympathetically innervated and decentralized skin and from the innervated skin of animals which had previously undergone adreno‐medullary denervation.5. Insulin‐induced hypoglycaemia resulted in sweating from sympathetically decentralized skin and from innervated skin in two out of four animals. Adreno‐medullary denervation abolished the sweat gland response to insulin administration.6. Cold exposure inhibited the response of innervated sweat glands but not that of decentralized glands to adrenaline infusion.7. It was concluded that heat‐induced and exercise‐induced sweating of the donkey is controlled by adrenergic nerves; adreno‐medullary secretion may contribute to sweating during exercise, and that cutaneous blood flow is important in the response of the glands to humoral stimulation.
Mechanical properties of glycerinated fibres from the tymbal muscles of a Brazilian cicada
Authors: Aidley D. J. , White D. C. S. 
Published: December 2014

1. Some of the properties of glycerinated fibres from the synchronous tymbal muscles of the cicada Fidicina rana have been investigated.2. In the presence of suitable concentrations of ATP and calcium ions, the fibres are able to perform oscillatory work when subjected to small sinusoidal length changes in the frequency range 2‐30 c/s.3. When subjected to abrupt changes in length, active fibres show a delayed increase in tension after a stretch and a delayed decrease in tension after release.4. The muscle fibres therefore show the mechanical properties characteristic of glycerinated fibres from asychronous insect flight muscles. Some implications of this finding in relation to the evolution of asynchronous muscles are discussed.
Influence of carotid baroreceptors on different components of the vascular system
Authors: Brender David , Webb‐Peploe Michael M. 
Published: December 2014

1. Reflex changes in wall tension of the lateral saphenous vein of one hind limb, the splenic veins and capsule, and the resistance vessels of the other hind limb caused by changes in baroreceptor activity were measured in vagotomized dogs under thiopentone‐chloralose anaesthesia.2. Three different methods were used to alter pressure in one or both carotid sinuses. (1) Both carotid sinuses were vascularly isolated and filled with fully oxygenated Krebs—Ringer bicarbonate solution (pH 7·4) from a reservoir in which the pressure could be altered at will. (2) One sinus was denervated, and the contralateral sinus was perfused with arterial blood at different flow rates. (3) One sinus was denervated, and the innervated sinus was perfused with arterial blood at constant flow, the pressure being altered by changing the outflow resistance.3. The left saphenous vein was perfused at constant flow with autologous blood; changes in perfusion pressure were used as a measure of changes in veno‐motor activity. The right common iliac artery was perfused at constant flow to measure changes in resistance vessel activity. Blood flow through the spleen was temporarily arrested, trapping a fixed volume of blood in the organ. Under these conditions, changes in splenic vein pressure were a measure of changes in smooth‐muscle tension in the splenic capsule and veins.4. In order to assess the responses to baroreceptor stimulation in terms of alterations in sympathetic nerve traffic to different components of the peripheral vascular system, ‘frequency—response curves’ were constructed for spleen, saphenous vein, and limb resistance vessels by electrical stimulation of the splenic nerves and lumbar sympathetic chains.5. The saphenous vein showed no consistent response to changes in baroreceptor activity. Reduction in carotid sinus pressure from 180 to 100 mm Hg caused an increase in venous pressure in the isovolumetric spleen and in the iliac artery perfusion pressure. These results were confirmed by electrical stimulation of the carotid sinus nerve. Whereas the peak responses of the limb resistance vessels corresponded to an increase in lumbar sympathetic nerve traffic of 6–10 c/s, the maximal splenic responses were equivalent to an increase in splenic nerve traffic of 1‐4 c/s. These results are consistent with selective autonomic nervous control of different components of the peripheral vascular system.
Presynaptic inhibition of the monosynaptic reflex by vibration
Authors: Gillies J. D. , Lance J. W. , Neilson P. D. , Tassinari C. A. 
Published: December 2014

In cats, the monosynaptic reflex (MSR) elicited from L7 or S1 dorsal roots, or from the tibial nerve (H reflex) was suppressed by vibration at 50–500 c/s of the hind limb with innervation intact. The MSR was not suppressed by selective vibration of cutaneous receptors, and suppression was still observed after the hind limb was skinned. In contrast, the phenomenon disappeared when all muscle nerves were crushed.Suppression of the MSR by vibration was shown to be mediated by presynaptic inhibition by the following methods: correlation with onset of the dorsal root potential (DRP) evoked by vibration, and abolition of both DRP and reflex suppression by picrotoxin; demonstration of primary afferent depolarization and normal excitability of motoneurones to direct stimulation.Reasons are given for deducing that the muscle afferent fibres responsible for the presynaptic inhibition induced by vibration are group Ia rather than groups Ib or II, or afferent fibres from Pacinian corpuscles.
The effect of urea loading on volume and concentration of urine in rabbits
Authors: Stanier Margaret W. 
Published: December 2014

1. To find how urea contributes to the water‐conserving ability of a herbivore's kidney, groups of ten young rabbits on a low‐protein diet and at three different levels of dietary electrolyte were given 1·8 g urea by mouth daily for 3 days. Vasopressin was administered daily to half the animals in each group.2. The urinary osmolarity and urea output of each animal was recorded daily during the urea loading and for a 3‐day control period before and after loading. The renal water requirement for non‐urea solute output (defined as daily volume/daily non‐urea solute output) was calculated. The sodium content of renal cortex and medulla was measured in some animals from each group.3. Urea caused additional water excretion only in those rabbits which were receiving the low‐salt diet. There was invariably increased water excretion when the ratio of urea to non‐urea solute output exceeded 2.4. In most of the rabbits on normal‐salt and high‐salt intake, urea produced little change in the volume in which non‐urea solute was excreted. Three out of the ten high‐salt animals showed significant reduction of this volume during urea‐loading.5. Vasopressin significantly reduced the volume required for non‐urea solute output, but the effect of vasopressin was independent of urea‐loading and of dietary electrolyte level.6. The low‐electrolyte diet significantly reduced the sodium concentration in the rabbits’ renal medullary tissue.7. It is concluded that in rabbits urea contributes to water retention mainly by its high permeability, enhanced by vasopressin, which permits maximal water reabsorption in the renal medulla. Water retention by means of uphill transport of urea, if it occurs at all, is slight.
Secretomotor function of the dorsal motor nucleus of the vagus
Authors: Kerr F. W. L. , Preshaw R. M. 
Published: December 2014

1. The effect of chronic ablation of the dorsal motor nucleus of the vagus on insulin‐induced secretion of acid by the stomach has been investigated in conscious cats.2. Destruction of this nucleus results in a persistent profound reduction in gastric secretion of acid under these experimental conditions, while the visceromotor and cardioinhibitory effects of stimulation of the distal end of the acutely transected ipsilateral cervical vagus were unaffected.3. It is concluded that the dorsal motor nucleus is a secretomotor centre.
The influence of stimulus parameters on contractions of isolated frog muscle fibres
Authors: Rüdel R. , Taylor S. R. 
Published: December 2014

1. Reversible changes in twitch and tetanus contractions of isolated frog muscle fibres were produced by varying the duration and strength of a transversely applied d.c. stimulus.2. When the stimulus strength was at least 1·1 times threshold the peak force of the contraction elicited was reduced by stimulus durations longer than 1 msec at 20 °C, and by durations longer than 3 msec at 2‐5 °C.3. As the strength of a prolonged stimulus was progressively increased to 3 times rheobase or more, peak twitch and tetanus force declined to 40–70% of the amplitude with short (0·2–0·5 msec) stimuli. The time to peak of the twitch was slightly decreased and the first phase of relaxation was accelerated.4. Cine‐micrography of fibres which were permitted to shorten under a light load revealed that the side of the fibre adjacent to the anode was unactivated under conditions which also reduced peak force output.5. With stimulus durations longer than 20 msec, peak force, time to peak, and relaxation time increased as the stimulus strength increased from 2·5 to 3 times rheobase. This might have been produced by a cathodal contracture following the action potential.6. The results are discussed in relation to previous studies of activation in striated muscle.