bluuebunny/crossref_metadata_2025_split huggingface dataset:
The energetics of tortoise muscle
Authors: Woledge R. C. 
Published: December 2014

1. A study has been made of the mechanical behaviour and the heat production of tortoise skeletal muscle during tetanic contractions.2. The relation between force (P) and velocity (v) is more curved than that of frog muscle. It can be fitted by Hill's equation (v/vmax = (1 ‐ P/P0)/(1 + P/a)) using a value of P0/a considerably less than for frog muscle.3. The value of the shortening heat constant is less than in frog muscle. It is about a half of a. No evidence was found that the value depended on the load.4. The maintenance heat rate is much less than in frog muscle and, as in frog muscle, is roughly equal to a.b (where b = vmax.a/P0). The maintenance heat rate does not diminish during a long tetanus as it does in frog muscle.5. The ratio of work/(work + initial heat) is greater in tortoise muscle than in frog muscle. As in frog muscle, the recovery heat is about equal to (work + initial heat). It follows that tortoise muscle is more efficient than frog muscle at converting free energy into work.6. Possible theoretical bases for connexions between the shape of the force—velocity curve of a muscle and its efficiency are discussed.
A study of the end‐plate potential in sodium‐deficient solution
Authors: Kordaš M. 
Published: December 2014

1. The effect of anticholinesterases in lengthening the end‐plate potential is much more pronounced in a low‐sodium solution than in an ordinary Ringer‐curare solution.2. To investigate this difference, intracellular recordings of end‐plate potentials and of end‐plate currents in voltage‐clamped muscle fibres were used.3. It was found that the very large lengthening of the end‐plate potential in a low‐sodium solution was due to a combination of three factors: (i) lengthening of the underlying end‐plate current, (ii) an increased membrane resistance and (iii) marked inward‐going (anomalous) rectification of the muscle membrane.
Energy cost of tonic contraction in a lamellibranch catch muscle
Authors: Baguet F. , Gillis J. M. 
Published: December 2014

1. The oxygen consumption of isolated anterior byssus retractor muscle (ABRM) of Mytilus edulis was measured during tonic contraction induced by acetylcholine (ACh).2. The respiration was measured with an oxygen electrode during 95 min, divided into one period of 5 min and six successive periods of 15 min.3. Tonic contraction induced a prolonged increase of the basal respiration that slowly diminished with a time course roughly similar to that of the tonic tension.4. For each period of measurement, the excess respiration over the resting level could be analysed into a constant amount and an amount that depended on the maintained tonic tension. The analysis was performed by fitting regression equations of the type Y = Q+bP, where Y is the excess respiration in n‐moles O2/g.min, and P, the isometric tension (kg/cm2); term b of the equation expresses the amount of oxygen consumption directly proportional to the tonic tension.5. During the first 20 min of contraction, terms b of the equations are not significant, and most of the excess respiration (terms Q) is independent of the tension. The oxygen consumed during this time is supposed to reflect the recovery metabolism for the energy cost of the development of the tension.6. From the 20th to the 80th min of contraction, terms Q are reduced and terms b are significant and constant. The excess respiration during this period is equal to 16·9 (±0·5) n‐moles O2/g.min + P × 6·8 (±0·5) n‐moles O2/kg.cm.min (±
S.E. of the means, n = 24).7. During a tonic contraction suppression of tension by a release reduced the oxygen consumption which increased again when tension was restored by stretching the muscle back to its original length. This confirmed the role of tension in determining the intensity of respiration during the catch.8. The oxygen consumption related to this tension restored by stretching the muscle, varied from 8·0 to 12·3 n‐moles O2/kg.cm.min. These figures are of the same order of magnitude as the coefficient b obtained in the case of tonic contraction without modification of tension by length changes.9. These results are taken as a demonstration that the maintenance of tonic tension is an ‘active’ phenomenon with a metabolic counterpart.
Interference with the metabolism of glucose by a non‐metabolizable hexose (3‐methylglucose)
Authors: Himsworth R. L. 
Published: December 2014

1. It having previously been shown that the injection of the non‐metabolizable sugar, 3‐methylglucose, into normal rats provokes the release of adrenaline with consequent hyperglycaemia, the effect of 3‐methylglucose upon the metabolism of glucose was investigated. In rats, whose adrenal glands had been denervated by transplantation, 3‐methylglucose reduced the oxidation of glucose by 46%. A reduction of this magnitude cannot be accounted for unless the oxidation of glucose by the brain is depressed.2. The lowering of the blood glucose concentration of adrenalectomized rats by insulin was prevented by the prior administration of 3‐methylglucose.3. 3‐Methylglucose retarded the movement of a glucose load from the blood into the tissues.4. The results of these experiments are consistent with competition between glucose and 3‐methylglucose for the glucose transfer system at cell surfaces.5. The similarity between the effects upon cerebral metabolism of hypoglycaemia and the interference by a non‐metabolizable sugar with glucose transport into the brain, is discussed.
Effects of hyperventilation on the circulatory response of the rabbit to arterial hypoxia
Authors: Crocker E. F. , Johnson R. O. , Korner P. I. , Uther J. B. , White S. W. 
Published: December 2014

1. The circulatory effects of artificial hyperventilation with air and low oxygen mixtures were studied in rabbits anaesthetized with chloralose‐urethane and given decamethonium iodide. The role of vagal afferents in the response to hypoxia was also assessed in spontaneously breathing unanaesthetized and anaesthetized animals.2. In the anaesthetized rabbit artificial hyperventilation inhibited all the changes in autonomic activity to the heart and peripheral circulation resulting from stimulation of the arterial chemoreceptors, and also reduced vagal efferent tone. In animals with section of the carotid sinus and aortic nerves the changes in autonomic activity observed during hypoxia and hyperventilation were much smaller than in normal animals and affected only cardiac autonomic activity.3. The effects of hyperventilation during hypoxia were mediated chiefly through vagal afferents rather than through the effects of hypocapnia. In the absence of changes in autonomic activity (e.g. during artificial hyperventilation with air) the circulatory effects were small and less clearly related to afferent vagal activity.4. In the spontaneously breathing anaesthetized and unanaesthetized rabbit vagal afferent activity resulting from the respiratory response to hypoxia inhibits sympatho‐adrenal activity in the same way as during hypoxia with artificial hyperventilation.5. The importance of the vagal afferent input in the rabbit is discussed in relation to the qualitative differences in circulatory response with increasing severity of hypoxia, and in relation to the effects of anaesthesia.
Secretion of kallikrein and its role in vasodilatation in the submaxillary gland
Authors: Beilenson Susanne , Schachter M. , Smaje L. H. 
Published: December 2014

1. The effects of parasympathetic (chorda) and sympathetic nerve stimulation on the concentration and output of kallikrein secreted in saliva from the cat's submaxillary gland were compared. Sympathetic stimulation always produced a much higher concentration (up to 500 times) and output (up to 390 times) of kallikrein than parasympathetic stimulation. In the dog, in which sympathetic nerve stimulation produces little or no secretion from the submaxillary gland, there was also a marked increase in the secretion of kallikrein when sympathetic was superimposed on parasympathetic secretion. This effect did not occur, however, in the rabbit's submaxillary gland.2. It was possible to deplete the cat's submaxillary gland of kallikrein, either by ligation of the duct for several days or by duct ligation and sympathetic nerve stimulation, so that it was undetectable either in the gland or in saliva after stimulation of the chorda. Such glands, nevertheless, responded to chorda stimulation with a normal atropine‐resistant vasodilatation.3. There is a close parallelism between the rate of secretion of salvia and vasodilatation over a range of frequencies of chorda stimulation, but the output (and concentration) of kallikrein in saliva is distinctly different for the same frequencies of nerve stimulation.4. Our results are consistent with the view that vasodilator nerves exist in the parasympathetic nerves to the submaxillary gland. We suggest that they are cholinergic in nature despite the fact that chorda vasodilatation is resistant to atropine. It is further suggested that neither the kallikrein—kinin system nor adrenergic vasodilator nerve fibres play a significant role in chorda vasodilatation.
The active transport of 5‐hydroxyindol‐3‐ylacetic acid and 3‐methoxy‐4‐hydroxyphenylacetic acid from a recirculatory perfusion system of the cerebral ventricles of the unanaesthetized dog
Authors: Ashcroft G. W. , Dow R. C. , Moir A. T. B. 
Published: December 2014

1. An operation on dogs for the implantation of guide tubes to the lateral ventricle and cisterna magna and a method whereby the ventricular space can be repeatedly perfused in conscious and unrestrained animals are described.2. The characteristics of a recirculatory perfusion system were examined and the bulk formation and absorption of cerebrospinal fluid and the volume of the ventricular space perfused were derived from the concentrations achieved during the infusion of inulin into the system.3. 5‐hydroxyindol‐3‐ylacetic acid (5‐HIAA), the acid metabolite of 5‐hydroxytryptamine, and 3‐methoxy‐4‐hydroxyphenylacetic acid (HVA), the main acid metabolite of dopamine, were demonstrated to be mainly removed from cerebrospinal fluid (c.s.f.) by an active transport system localized in the region of the fourth ventricle.4. It was possible to inhibit the active transport of these acids from cerebrospinal fluid by pre‐treating the dogs with probenecid.
Cord cells responding to fine myelinated afferents from viscera, muscle and skin
Authors: Pomeranz B. , Wall P. D. , Weber W. V. 
Published: December 2014

1. Micro‐electrode recordings were made in the thoracic cord of acute spinal cats. Cells, which were located in the histologically defined lamina 5, responded both to the fine myelinated afferents from the splanchnic nerve and to afferents from the skin. Splanchnic afferents inhibit the effect of converging cutaneous inputs for periods up to 150 msec. Skin stimuli may also inhibit the effect of afferent nerve impulses from viscera. Some cells respond monosynaptically to the splanchnic afferents, others indirectly.2. Fine myelinated afferents from gastrocnemius (group 3) stimulate lamina 5 cells which also have cutaneous receptive fields. Cutaneous and group 3 muscle afferents interact by mutual inhibition in their effect on the cells.3. Fine myelinated afferents from skin excite lamina 5 cells. The cutaneous responses of lamina 5 cells contrast with those of lamina 4 cells in the following respects: (a) the receptive fields are larger, (b) they respond with an increased latency to Aβ afferents, (c) there is a low pressure threshold at the edge, (d) they respond to a wide range of pressure stimuli from light brush to heavy pinch applied to the centre of the receptive fields and (e) they respond to AΔ afferents.4. Lamina 5 cells receive fine myelinated afferents either from viscera or from muscle or from skin. Lamina 4 receives large myelinated afferents from skin and lamina 6 receives large myelinated afferents from muscle. The results suggest the hypothesis that some fine myelinated afferents form a class of afferents which signal the state of tissue, and end on lamina 5 cells.
The analysis of image motion by the rabbit retina
Authors: Oyster C. W. 
Published: December 2014

1. Micro‐electrode recordings were made from rabbit retinal ganglion cells or their axons. Of particular interest were direction‐selective units; the common on—off type represented 20·6% of the total sample (762 units), and the on‐type comprised 5% of the total.2. From the large sample of direction‐selective units, it was found that on—off units were maximally sensitive to only four directions of movement; these directions, in the visual field, were, roughly, anterior, superior, posterior and inferior. The on‐type units were maximally sensitive to only three directions: anterior, superior and inferior.3. The direction‐selective unit's responses vary with stimulus velocity; both unit types are more sensitive to velocity change than to absolute speed. On—off units respond to movement at speeds from 6′/sec to 10°/sec; the on‐type units responded as slowly as 30″/sec up to about 2°/sec. On‐type units are clearly slow‐movement detectors.4. The distribution of direction‐selective units depends on the retinal locality. On—off units are more common outside the ‘visual streak’ (area centralis) than within it, while the reverse is true for the on‐type units.5. A stimulus configuration was found which would elicit responses from on‐type units when the stimulus was moved in the null direction. This ‘paradoxical response’ was shown to be associated with the silent receptive field surround.6. The four preferred directions of the on—off units were shown to correspond to the directions of retinal image motion produced by contractions of the four rectus eye muscles. This fact, combined with data on velocity sensitivity and retinal distribution of on—off units, suggests that the on—off units are involved in control of reflex eye movements.7. The on—off direction‐selective units may provide error signals to a visual servo system which minimizes retinal image motion. This hypothesis agrees with the known characteristics of the rabbit's visual following reflexes, specifically, the slow phase of optokinetic nystagmus.
A blood‐testis barrier restricting passage from blood into rete testis fluid but not into lymph
Authors: Setchell B. P. , Voglmayr J. K. , Waites G. M. H. 
Published: December 2014

1. A permeability barrier in or around the seminiferous tubules of rams has been demonstrated by studying the rate of passage of a variety of substances from blood plasma into fluid collected from the rete testis and into testicular lymph.2. All substances studied passed readily into testicular lymph.3. Tritiated water, urea, ethanol and bicarbonate in rete testis fluid equilibrated with blood plasma within 3 hr; Na+, K+, Rb+, Cl−, I−, CNS−, creatinine and galactose entered slowly and p‐aminohippurate (PAH), glutamate, iodinated albumin, inulin and [51Cr]EDTA did not appear in rete testis fluid at all.4. Rubidium was excluded relative to iodoantipyrine from the testes of control and hypophysectomized rats and from rat testes heated to 37, 40, 43 and 45° C; no such exclusion was seen in testes of rats which had been given cadmium chloride 5 months earlier so as to destroy the seminiferous tubules.5. It is suggested that this permeability barrier will regulate the access to the seminiferous epithelium of some constituents of blood plasma, isolate the germinal cells immunologically and help to maintain the concentration differences between rete testis fluid and lymph or blood plasma.
Factors influencing the time course of S‐potentials resulting from brief flashes
Authors: Naka K. I. 
Published: December 2014

1. Wave forms of the S‐potential (luminosity‐type) from the tench retina were analysed with single or repetitive flashes.2. In tench the slope of the ‘
ON’ phase was dependent on the relative flash intensity but was independent of flash duration (if it was longer than 15 msec) and the state of adaptation.3. The slope of the ‘
OFF’ phase was a dual function of flash duration and of the state of adaptation. Light adaptation brought forth a sharp ‘
OFF’ phase, referred to as ‘cut‐off’ in this paper.4. Temporal or spatial contrast of light and darkness was necessary for the appearance of the cut‐off which was partly responsible for complex wave forms of the L‐type potential.5. As far as the wave form is concerned the information on the state of adaptation is well processed before it is fed into the S‐space as voltage and does not appear there as a shift in d.c. level.
Classification of inferior collicular neurones of bats in terms of responses to pure tones, frequency‐modulated sounds and noise bursts
Authors: Suga Nobuo 
Published: December 2014

1. Single unit activity in the inferior colliculus of bats was studied with pure tones, FM (frequency‐modulated) sounds and noise bursts which are the most basic three components of the complex sounds produced by many different animals including man. Neurones were divided into three groups, (i) ‘generalized’ units responding to all three elements, (ii) ‘deaf’ units responding to two out of the three and (iii) ‘specialized’ units responding to only one of the three. Each of these was divided into three subgroups.2. Three subgroups of generalized units were called ‘symmetrical’, ‘asymmetrical’ and ‘upper‐threshold’ units. The symmetrical unit had a wide excitatory area and responded to any sounds which had components falling in this area. The asymmetrical unit had a narrow excitatory area abutting on a large inhibitory one and showed different responses to FM sounds depending on the directions of frequency sweep. The upper‐threshold unit had not only an excitatory area, but also an inhibitory one. The neurone failed to respond to strong sounds, i.e. these showed upper thresholds.3. Three subgroups of deaf units were called ‘pure tone‐deaf’, ‘FM‐deaf’ and ‘noise‐deaf’ units. The pure tone‐deaf unit did not respond to any pure tones but did respond to FM sounds and noise bursts. The noise‐deaf unit did not respond to noise bursts but did respond to pure and FM tone pulses. An FM‐deaf unit has not yet been confirmed.4. Three subgroups of specialized units were called ‘pure tone‐specialized’, ‘FM‐specialized’ and ‘noise‐specialized’ units which responded exclusively to either pure tones, FM sounds or noise bursts, respectively. In the FM‐ and noise‐specialized units, pure tone pulses caused only inhibitory processes.5. About 95% of neurones studied showed phasic on‐responses to sound stimuli and almost no spontaneous discharges. Only a small percent of neurones showed spontaneous discharges higher than a few impulses per second. Response patterns of some of these neurones changed with frequency, intensity, duration and repetition rate of sound stimuli. These neurones responded to any of pure tones, FM sounds and noise bursts.6. All neurones except the symmetrical ones had inhibitory areas, in which sounds inhibited responses to excitatory ones when these are delivered simultaneously. Therefore the structure in complex sounds is very important in the excitation of these neurones.
The effect of temperature on the membrane conductance of the smooth muscle of the guinea‐pig taenia coli
Authors: Brading Alison , Bülbring Edith , Tomita T. 
Published: December 2014

1. The effect of temperature on the membrane conductance of the smooth muscle of guinea‐pig taenia coli was investigated electrophysiologically, using the double sucrose gap method, and by ion‐flux determinations.2. In the range between 19° C and 37° C, the membrane conductance increased with rising temperature and decreased with cooling (Mean Q10 about 2·5).3. When the Cl concentration in the external medium was low (Cl− substitution with benzene‐sulphonate), the effect of changing the temperature was smaller (Mean Q10 about 1·5).4. In muscle depolarized by excess K (27 m
M) in a solution containing low Cl, cooling repolarized the membrane and markedly increased membrane resistance.5. The slow phases of the 42K‐ and 36Cl‐exchange were greatly slowed by cooling which did not change the rate constants of the 24Na‐efflux curve. Thus observations on the rate of exchange of ions agreed with the electrophysiological findings indicating a reduction of K‐ and Cl‐conductance of the cell membrane at low temperature.6. The depolarization produced by lowering the external Ca‐concentration was greatest at high temperature (37° C). With cooling the membrane was repolarized and membrane resistance increased.7. The sustained state of depolarization observed when the external Ca was replaced by Ba (2·5 m
M) at high temperature (37° C) was terminated by cooling.8. The observations may be interpreted by the hypothesis that Ca, located at two different membrane sites, controls, independently, at the outer layer mainly Na‐ (and Ba‐) permeability and at the inner layer mainly K‐permeability, the Ca‐binding at these sites being affected by temperature in the opposite direction.
Heart capillary permeability to lipid‐insoluble molecules
Authors: Alvarez O. A. , Yudilevich D. L. 
Published: December 2014

1. A study has been made, in the isolated, beating dog heart perfused with blood, of the transcapillary exchange of the following substances: [3H]water, 22Na, 86Rb, 36Cl, [14C]urea, [3H]glycerol, [3H]glucose, [14C]sucrose and [3H]inulin.2. The method used to study the exchange was the ‘indicator diffusion’ technique. It consists in a rapid arterial injection of a mixture containing a diffusible and a non‐diffusible molecule, followed by a rapid split collection of the venous outflow, up to 30 sec. The fractional extraction, E, of the diffusible substance was obtained by comparing the relative concentrations of both tracers in injected medium and in each venous sample.3. E for [3H]water was the highest (0·90 ± 0·3), and it did not vary with flow. All other molecules had values for E that decreased as flow increased.4. Capillary permeability constant, P, was estimated from PS = — F ln (1 — E), in which S is the surface area of exchange and F is the blood perfusion rate. To test the validity of the equation, E was measured at different blood perfusion rates. It was found that the equation did not apply at relatively low flows for the more diffusible substances.5. The average values of P estimated for inulin, sucrose, glucose, glycerol and urea were 0·27, 0·8, 1·0, 1·5 and 3·1 × 105 (cm/sec), respectively. The ratio P/D (in which D is the free diffusion in water constant) was the same for all these substances. This can be interpreted as showing that if pores exist in the capillary endothelium, they must be larger than 80–100 Å diameter. It is concluded that the pores could actually be the intercellular slits as previously suggested by electron microscope studies. Endothelial cell participation in the exchange appears to be small except for [3H]water.
Supraspinal control of reflex activity in renal nerves
Authors: Coote J. H. , Downman C. B. B. 
Published: December 2014

1. In anaesthetized cats distension of carotid sinus inhibited renal nerve activity and intercostal‐renal nerve reflexes. The degree of inhibition was dependent on the amount of rise in sinus pressure. Intercostal‐intercostal reflexes were not inhibited.2. Inhibition of renal nerve activity and intercostal‐renal nerve reflexes could be obtained on stimulating in the dorsal reticular formation but mainly in the ventromedial reticular formation at the level of the obex. The intercostal reflex could also be inhibited at several of these points.3. The possibility that two inhibitory mechanisms are available is suggested, at least one projecting on to spinal reflex arcs.4. Other ways of inhibiting renal nerve activity were shown. One was similar to that produced by single shocks to peripheral skin and muscle nerves, and the other was due to a subnormal excitability of vasomotor neurones following intense activation.