bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of prolonged saline‐exposure on sodium transport across frog‐skin
Authors: Hornby R. , Thomas S. 
Published: December 2014

1. Differences in Na transport between skins from Rana temporaria and R. esculenta maintained for up to several weeks in water or 0·7% saline (0·7 g NaCl in 100 ml. H2O), with and without daily injections of 4% saline (4 g NaCl in 100 ml. H2O), were measured, in vitro.2. In saline‐treated skins, the following changes were found:(a) An increased Na content.(b) A consistent decrease in short‐circuit current (Isc).(c) An increased d.c. resistance, R, the consistency of which varied with the anion content of the Ringer solution.(d) A highly significant fall in Na influx, accounting for the reduced Isc; a small reduction in Na efflux was not significant, statistically.(e) The Pitressin‐induced increment in Isc was usually considerably lower compared with that in water‐exposed skins; considered relative to the pre‐Pitressin values, however, there were no clear differences.(f) By calculation from the changes in resistance (R) caused by replacement of outer Na2SO4 Ringer by K2SO4 Ringer solution,I. E0, the electromotive force of the active sodium transport system, was moderately, but significantly, reduced,II. R shunt, the shunt path resistance, was moderately, but significantly, increased, andIII. Rser, the series path resistance, was considerably, and highly significantly, increased.(g) K influx from outer K2SO4 Ringer solution was reduced.3. Differences between skins from water‐exposed and saline‐treated frogs persisted, in vitro, despite the occurrence of anionic‐dependent acute changes after mounting in Ringer solution.4. There were seasonal changes in Isc, and in the effects of saline treatment.5. The findings are discussed in terms of decreased permeability of outer barriers to ion‐diffusion, and reduced activity of a Na pump.
Blood volume changes in outdoor exercise of 8‐10 hour duration
Authors: Pugh L. G. C. E. 
Published: December 2014

1. Blood volume was measured with carbon monoxide on six hill‐walkers before and immediately after a 28‐mile walk on two occasions. The subjects had free access to food and fluid.2. Blood volume increased and haematocrit fell significantly on both occasions compared with the control observations. The mean increase of blood volume was 204 ml. or 3·9% (P < 0·01) and the mean reduction of haematocrit was 2·1% (P < 0·02). Plasma volume calculated from these results increased by 233 ml. or 7·3%. There was no significant change in red cell volume or plasma protein concentration.3. These changes are the opposite of those taking place in short‐term exercise and suggest that in the absence of dehydration a compensatory adjustment of blood volume takes place during exercise of many hours duration.
Cutaneous thermoreceptors in primates and sub‐primates
Authors: Iggo A. 
Published: December 2014

1. Cutaneous thermoreceptors were examined electrophysiologically in primates (monkey, baboon) and in sub‐primates (dog and rat) by recording from single units dissected from peripheral nerves.2. Thermal stimuli were delivered from thermodes in contact with the skin.3. Primate ‘cold’ receptors had spot‐like receptive fields and were found in both hairy and glabrous skin. The conduction velocities of the axons ranged from 0·6 to 15·3 m/sec.4. The discharge from the primate receptors characteristically appeared in bursts with intervals of silence within the range temperatures of 18‐40° C. Static and dynamic sensitivity curves were established, with maxima about 30° C.5. Cold receptors in the lip of the dog had maximal sensitivity at 31‐37° C. The axons were myelinated with conduction velocities less than 20 m/sec.6. ‘Warm’ receptors, with maximal sensitivity at 40° C and non‐myelinated axons, were abundant in the scrotal nerve of the rat. The ‘cold’ receptors had maximal responses at 23‐28° C.7. The ‘spurious’ thermoreceptor behaviour of slowly adapting mechanoreceptors is described and the way in which they may distort integrated potential records from whole nerves is analysed.
A quantitative analysis of the responses of certain dorsal horn neurones to mechanical stimulation of the large foot pad in cats
Authors: Fuller D. R. G. , Gray J. A. B. 
Published: December 2014

1. Responses of single units in the dorsal horns of the spinal cords of cats to mechanical stimulation of the large foot pad have been recorded.2. The observations made with different single stimuli belonging to the set under different conditions of excitability have included: the numbers of impulses per response, their means and variation; the frequency distributions of impulse numbers; the time distribution of activity during a response and in particular the probability of an impulse occurring in each successive time interval.3. The observations with two stimuli were designed to measure the [ill] of the whole response contributed by the second stimulus and [ill] relate the size of this contribution to the interval between the stimuli and their distance apart.4. The results are discussed and it is concluded that the observed transformations allow representations of successive events to exist at the same time and that the purpose of the transformation may therefore be to allow particular types of interaction between successive events. A model of mechanism which is consistent with many of the observations is also discussed.
Relationship between growth hormone and muscular work in determining muscle size
Authors: Goldberg A. L. , Goodman H. M. 
Published: December 2014

1. Growth hormone reduced the loss of weight or induced net growth of denervated soleus and plantaris muscles in hypophysectomized rats.2. Growth hormone did not alter the weight of the denervated muscle relative to its contralateral control, i.e. the hormone increased the sizes of denervated and control muscles proportionately.3. Similarly treatment with the hormone appeared to cause proportional growth in muscles undergoing work‐induced hypertrophy and their contralateral controls.4. It is suggested that muscle size is determined by at least two independent factors, growth hormone and muscular work. Growth hormone appears to act as a biochemical ‘amplifying system’ for the cell's anabolic machinery and determines the absolute changes in muscle size which result from changes in muscular work.
Retardation of protein synthesis in rat foetal liver on inhibiting rate of histamine formation
Authors: Grahn B. , Hughes Rosanne , Kahlson G. , Rosengren Elsa 
Published: December 2014

1. The rate of protein synthesis, as gauged by the incorporation of [14C]leucine, has been determined in vitro in foetal and 5‐day‐old rat liver, tissues with respectively high and low histidine decarboxylase activity.2. Incorporation of [14C]leucine was considerably faster in foetal liver than in liver of the young.3. Following inhibition of histamine formation by α‐methyl histidine, a specific inhibitor of histidine decarboxylase, the rate of incorporation of [14C]leucine was substantially diminished in foetal but not in liver of the young.4. The retarded incorporation of [14C]leucine consequent on inhibition of endogenous histamine formation could not be restored by extracellular histamine, i.e. by adding histamine to foetal liver tissue.5. On complete inhibition of protein synthesis by puromycin in foetal and 5‐day‐old rat liver the rate of histamine formation was not affected.6. The present observations support the view of endogenous histamine formation, ‘nascent histamine’, as an essential part of the metabolic machinery in some rapidly growing tissues.
The structure and function of a slowly adapting touch corpuscle in hairy skin
Authors: Iggo A. , Muir A. R. 
Published: December 2014

1. Slowly adapting cutaneous mechanoreceptors, in the cat and primates, have been studied by histological and neurophysiological methods.2. Each touch corpuscle is a dome‐shaped elevation of the epidermis, whose deepest layer contains up to fifty specialized tactile cells.3. Nerve plates, enclosed by the tactile cell (Merkel cells), are connected to a single myelinated axon in the dense collagenous core of the corpuscle.4. The corpuscle generated > 1000 impulses/sec when excited by vertical surface pressure. The response was highly localized and showed a low mechanical threshold, the frequency being dependent upon the velocity and amplitude of the displacement. There was a period of rapid adaptation before a sustained response which might continue for > 30 min.5. A quantitative analysis of the responses to excitation by displacements of differing amplitude, velocity and duration is included.6. The discharge of touch corpuscle units evoked by a mechanical stimulus was temperature‐sensitive, and was enhanced by a fall in skin temperature.
Force measurements in skinned muscle fibres
Authors: Hellam D. C. , Podolsky R. J. 
Published: December 2014

1. Isometric force was measured in skinned segments of frog semitendinosus muscle fibres exposed to solutions in which the calcium ion concentration was controlled with EGTA.2. The threshold for force development, calculated from an apparent stability constant for the CaEGTA complex of 106.69
M−1 at pH 7·0, was generally close to pCa 7·5. Maximum force was reached at about pCa 6·0.3. Maximum force is proportional to the cross‐sectional area of the fibres.4. The rate of force development was slower than that expected from simple diffusion of a substance from the bathing solution into the fibre. The delay appears to be due to slow equilibration of the EGTA buffer system during calcium uptake by the sarcoplasmic reticulum.5. Addition of deoxycholate (DOC) to the bathing solution produced a reversible increase in the rate of force development. The steady force was also increased for values of pCa that gave less than maximum force, which shifted the force—pCa relation toward lower calcium concentrations by about 0·5 pCa unit.6. The length—force relation in partially activated preparations is similar to that reported for electrically activated intact fibres. This result suggests that in the region of myofilament overlap the affinity of the binding sites for calcium is uniform along the length of the calciumbinding myofilament.
The significance of the shape of the lens and capsular energy changes in accommodation
Authors: Fisher R. F. 
Published: December 2014

1. A method for the estimation of the energy released by the anterior part of the lens capsule during accommodation is described. This includes(i) A determination of the pressure required to distend the capsule by a standard volume.(ii) The calculation from the photographed lens profiles of the degree of capsular contraction which occurs when the lens changes from the unaccommodated to the accommodated form.(iii) Capsular volume changes in vitro are then related to the surface area changes calculated for the lens in vivo.2. A correlation exists between the stored capsular energy per unit area or surface tension and the accommodation power of different species. The human lens capsule releases 1170 ergs/cm2 while the more spherical lenses of the cat and rabbit release 520 and 485 ergs/cm2 respectively for a 10% change in lens diameter. The amount of energy which can be stored depends on the degree of flatness of the lens and the volume of the anterior segment. The flatter the lens and the smaller the volume of the anterior segment, the greater the capsular surface tension.3. The anterior surface of the human lens remains ellipsoidal throughout life. The changes of accommodation which occur in presbyopia may therefore be related to the lens profiles at various ages. It is found that a coefficient obtained by dividing the anterior volume of the lens by the 5th power of the equatorial radius of the lens modifies the degree of accommodation for a given change of lens diameter.4. The loss of accommodation is proportional to the effective capsular surface energy until about the age of 45. The effective capsular surface energy can be defined as the energy which gives the same change in lens dioptric power per erg regardless of the lenticular profile changes which occur with age. It is obtained by multiplying capsular surface tension at a given age by a ratio. This is obtained by dividing the profile coefficient mentioned in paragraph 3 of the given lens, by the profile coefficient of the reference lens aged 15 (0·068). The effective surface energy of the entire lens falls from 110 ergs at the age of 15 to 50 ergs at 60. Assuming that ciliary power remains unaltered 55% of the loss of accommodation is accounted for solely by the fall in Young's Modulus of elasticity of the capsule and the changing shape of the lens with age.
Cardiovascular responses in apnoeic asphyxia: role of arterial chemoreceptors and the modification of their effects by a pulmonary vagal inflation reflex
Authors: James Jennifer E. Angell , Daly M. de Burgh 
Published: December 2014

1. In the spontaneously breathing anaesthetized dog, the systemic circulation was perfused at constant blood flow; there was no pulmonary blood flow and the systemic arterial blood PO2 and PCO2 were controlled independently by an extracorporeal isolated pump‐perfused donor lung preparation. The carotid and aortic bodies were separately perfused at constant pressure with blood of the same composition as perfused the systemic circulation.2. Apnoeic asphyxia, produced by stopping the recipient animal's lung movements and, at the same time, making the blood perfusing the systemic circulation and the arterial chemoreceptors hypoxic and hypercapnic by reducing the ventilation of the isolated perfused donor lungs, caused an increase in systemic vascular resistance.3. While the systemic arterial blood was still hypoxic and hypercapnic, withdrawal of the carotid and aortic body ‘drive’ resulted in a striking reduction in systemic vascular resistance. Re‐establishing the chemoreceptor ‘drive’ immediately increased the vascular resistance again.4. Apnoeic asphyxia carried out while the carotid and aortic bodies were continuously perfused with oxygenated blood of normal PCO2 had little or no effect on systemic vascular resistance.5. The systemic vasoconstrictor response produced by apnoeic asphyxia was reduced or abolished by re‐establishing the recipient animal's lung movements, and this effect occurred in the absence of changes in the composition of the blood perfusing the systemic circulation and arterial chemoreceptors. This abolition of the vasoconstriction was due to a pulmonary reflex.6. Apnoeic asphyxia slowed the rate of the beating atria due to excitation of the carotid and aortic body chemoreceptors. This response can be over‐ridden by an inflation reflex arising from the lungs.7. It is concluded that the cardiovascular responses observed in apnoeic asphyxia are due, at least in part, to primary reflexes from the carotid and aortic body chemoreceptors engendered by arterial hypoxia and hypercapnia. The appearance of these responses is, however, dependent upon there being no excitation of a pulmonary (inflation) vagal reflex.
The slowing of gastric emptying by nine acids
Authors: Hunt J. N. , Knox M. T. 
Published: December 2014

1. Test meals containing a range of concentrations of nine different acids were given to twenty healthy subjects. The acids used were hydrochloric, acetic, lactic, tartaric, phosphoric, citric, propionic, butyric and hexanoic.2. The greater the concentration of acid in the meal the greater was the volume of the meal recovered after a fixed interval.3. A rectilinear relationship between the mean concentrations of acid (m‐equiv/l.) required to give a recovery of 450 ml. and the molecular weights of the acids used was found. The acids with high molecular weights were less effective than those with low molecular weights.4. The results indicate that the molecular weights of the anions play the dominant part in determining the effectiveness of the various acids. Slowing of gastric emptying by acids does not seem to be dependent upon their pK values provided they are less than 5. The oil/water partition coefficients are also apparently irrelevant to effectiveness.5. These findings are considered to be consistent with the view that a barrier to movement of the anions in an aqueous system limits the access of the hydrogen ions to duodenal receptors, which activate the mechanism slowing gastric emptying.
The role of the vagus nerves in the respiratory and circulatory reactions to anaphylaxis in rabbits
Authors: Karczewski W. , Widdicombe J. G. 
Published: December 2014

1. Rabbits, previously sensitized to egg albumen, were anaesthetized and then rendered anaphylactic by a further injection of egg albumen; total lung conductance of flow, lung compliance, breathing rate, tidal volume, end‐tidal CO2%, systemic arterial and right atrial blood pressures and heart rate were measured. Before induction of anaphylaxis, some rabbits were vagotomized, some had their vagi cooled to block differential conduction, and others were paralysed and artificially ventilated to minimize secondary changes in afferent activity from the lungs and in blood gas tensions.2. Lung conductance was reduced by anaphylaxis in spontaneously breathing and in artificially ventilated rabbits, and the effect was lessened by vagal cooling and greatly reduced by vagotomy; the hyperventilation of anaphylaxis took the form of an increase in tidal volume rather than in respiratory frequency during vagal cooling, and all changes in ventilation were abolished by vagotomy. These effects are therefore dependent on the integrity of vagal nervous pathways.3. Lung compliance was reduced by anaphylaxis to a similar degree in all groups of rabbits; all groups showed similar falls in end‐tidal CO2%. These effects are therefore not dependent on the integrity of vagal conduction.4. Anaphylaxis reduced systemic arterial blood pressure, the response being smaller when the vagi were cooled or cut.5. It is concluded that anaphylaxis has direct actions on the pulmonary vascular bed, the distal airways or the alveoli. However, the changes in breathing, blood pressure and large airway calibre are mainly dependent on vagal reflex activity. By analogy with responses to injections of histamine and phenyl diguanide (Karczewski & Widdicombe, 1969b) it is concluded that anaphylaxis stimulates lung deflation and irritant receptors which mediate much of the reflex responses.
Functional consequences of tenotomy in hind limb muscles of the cat
Authors: Nelson P. G. 
Published: December 2014

1. The chronic EMG activity and the contractile properties of normal, denervated or tenotomized cat triceps surae muscles were measured.2. Following Achilles tenotomy no measurable change in EMG activity occurred in either the soleus or medial gastrocnemius muscles.3. No change in the twitch time or tetanus‐twitch ratio was seen following tenotomy in these muscles despite marked atrophy of the muscle. Measurements were made 3‐10 weeks following the tenotomy procedures.4. Denervation results in some prolongation of the gastrocnemius twitch.5. The relationship between the contractile properties of a given muscle and the aggregate amount of activity imposed on that muscle by its innervation is discussed.
The secretion of electrolytes and enzymes by the pancreas of the anaesthetized cat
Authors: Case R. M. , Harper A. A. , Scratcherd T. 
Published: December 2014

1. The bicarbonate concentration in cat pancreatic juice falls and the chloride concentration increases at slow secretory rates. The concentration of sodium and potassium remain constant at all secretory rates.2. Acetazolamide reduces the maximal rate of secretion markedly, and the maximal bicarbonate concentration slightly, but does not alter the reciprocal relationship between bicarbonate and chloride at slow rates of flow.3. By perfusion of the main duct it has been shown that there is a loss of bicarbonate and a gain of chloride across the duct wall due to a passive process of exchange diffusion. It is suggested that this may account for a substantial part of the flow‐dependent changes in bicarbonate and chloride concentrations in the intact gland.4. The enzyme content of pancreatic juice is made up of a small continuous basal output, to which may be added a much larger secretion in response to hormonal stimulation.5. From analysis of successive small samples of juice it has been found that the response to single injections of pancreozymin lasts a very short time, during which the secretory cells release enzymes in a small volume of chloride‐containing fluid.6. It is concluded that in the cat pancreatic secretion consists of an isosmolar primary secretion mostly of sodium bicarbonate, to which is added small amounts of a chloride‐containing enzyme secretion. This fluid is modified, particularly at slow flow rates, by transductal exchange of chloride and bicarbonate which, at least in the main duct, is passive in nature.
A lesion of the transverse tubules of skeletal muscle
Authors: Howell J. N. 
Published: December 2014

1. A method is described by which a selective lesion can be made in vitro in the transverse tubules of frog skeletal muscle.2. The method consists of exposing the muscle for 1 hr or more to a buffered salt solution made hypertonic by the inclusion of 400 m
M glycerol and then returning the muscle to an isotonic salt solution. The lesion is induced during the washout of the glycerol.3. Electron micrographs reveal that the lesion consists of a rearrangement of the T‐system membranes in such a way that the continuity of the tubules is lost. The membranes appear to coalesce into large vesicles scattered irregularly throughout the sarcoplasm.4. The glycerol treatment results in a depression of the resting potential of up to 30 mV. The treated fibres are depolarized by high concentrations of K as are normal muscle fibres.5. T‐tubule lesioned fibres are unable to respond mechanically either to electrical stimulation or to elevated K but they do contract in the presence of caffeine and relax when the caffeine is removed.6. Problems concerning the variability of the procedure are presented and certain considerations concerning the mechanism of the effect are discussed.
Hypoxia and pulmonary arterial pressure in the rabbit
Authors: Owen-Thomas J. B. , Reeves J. T. 
Published: December 2014

1. The effect of hypoxia on pulmonary arterial pressure was studied in young and adult rabbits.2. In isolated perfused lungs, hypoxia caused no rise in pulmonary arterial pressure in rabbits on the day of birth. The size of the hypoxic response increased progressively until 9–11 days of age, when the adult response of a 20% rise of pulmonary arterial pressure at constant flow was attained.3. The intact adult rabbit responded to hypoxia with a 14–30% rise in pulmonary arterial pressure, attributed to vasoconstriction and independent of frequency or tidal volume during positive pressure ventilation.