bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sodium fluxes in diaphragm muscle and the effects of insulin and serum proteins
Authors: Creese R. , Jenden D. J. 
Published: December 2014

1. Thin diaphragm muscles in dialysed serum maintained their total sodium at values similar to those found in vivo. The fibre sodium exchanged with a half‐time of 5 min, and the flux was 10 p‐mole.cm−2.sec−1. The internal sodium was less than 10 μmoles/g fibre water and the ratio of external to internal sodium was at least 15. The calculated energy expenditure for sodium extrusion was less than 2% of the resting metabolism.2. In physiological saline the half‐time for exchange of fibre sodium was similar to that in serum, but in saline there was an increase in sodium permeability and a raised total and fibre sodium.3. Muscles treated with insulin (0·02 u./ml.) showed a more rapid exchange of sodium compared with muscles in saline, with no change in the permeability to sodium. Insulin also affected sodium movements in the absence of external glucose.4. In saline the fraction of sodium which exchanged rapidly occupied 0·33 by volume of the muscle, after corrections for diffusion, and this value was similar to the mannitol space.5. Fibre diameters were measured in frozen sections. Muscles prepared by fixation and embedding showed marked shrinkage.
A down then up staircase in frog ventricle due to altered excitation—contraction coupling
Authors: Brown A. M. , Orkand R. K. 
Published: December 2014

1. Repetitive stimulation of frog ventricle strips bathed in low calcium (< 1m
M) fluids produced a decrease followed by an increase in successive tension responses which was not due to changes in the amplitude or the duration of the cardiac action potential.2. The depression of contraction reached its peak 5‐10 sec after a conditioning contraction and decayed to one half in about 0·5 min; it was greater during a series of 5‐10 stimuli when the frequency was increased from 3/min to 12/min.3. Lowering the external calcium concentration increased the amount of depression.4. The initial depression could be converted to facilitation by: (a) increasing the external calcium; (b) lowering the external sodium; (c) lowering the external potassium; and (d) the addition of strophanthidin.
The constancy of the energy expended by rats on spontaneous activity, and the distribution of activity between feeding and non‐feeding
Authors: Morrison S. D. 
Published: December 2014

1. Methods were developed and described for partitioning the total daily energy expenditure of rats into compartments attributable to rest, total spontaneous motor activity and feeding activity.2. In terms of energy expenditure feeding appeared as a form of motor activity which was at least as costly as other spontaneous activity.3. The compartment attributable to total spontaneous activity within a 24 hr period was about 25% of total energy expenditure and was not altered by body weight, food intake or feeding mode (e.g. solid or liquid food).4. The compartment attributable to feeding activity varied with food intake and with feeding mode in such a way that non‐feeding activity varied inversely with feeding activity. By a given feeding mode non‐feeding activity varied inversely with food intake.5. It is concluded (a) that food deprivation does not induce increased total activity by the rat, but does produce a complementary increase in non‐feeding activity; (b) that measurement of a specific motor activity does not give a valid estimate of change in total activity; and (c) that the complementary relationship between the energy expended on feeding activity and that expended on non‐feeding activity is responsible for the decline in food intake with increasing non‐feeding activity that has been shown to occur at low habitual levels of spontaneous activity.
Thermal studies of the rates of the reactions of carbon dioxide in concentrated haemoglobin solutions and in red blood cells. A. The reactions catalysed by carbonic anhydrase. B. The carbamino reactions of oxygenated and deoxygenated haemoglobin
Authors: Kernohan J. C. , Roughton F. J. W. 
Published: December 2014

1. The initial rates of uptake of carbon dioxide by bovine Hb and HbO2, in solutions and in intact red cells at 25° C, pH 6·8‐7·4, have been measured by the continuous flow rapid calorimeter in the presence and absence of the carbonic anhydrase inhibitor acetazolamide.2. Over the time range 0‐10 msec the only significant reaction, in the presence of acetazolamide, was the carbamino combination of CO2. In the absence of acetazolamide there was a much larger heat evolution owing to the simultaneous catalysis of CO2 to bicarbonate due to the enzyme, carbonic anhydrase. Subtraction of the former rate from the latter gives the catalysis of the CO2 hydration per se. The mode of calculating the actual amount of chemical change from the observed heat evolution is described in detail.3. The carbonic anhydrase activity was found to vary about threefold between individual blood samples, as in previous work on dilute bovine enzyme solutions, but to be independent of the state of oxygenation of the haemoglobin. Comparison of the enzyme activity in solution and in the red cell seemed to show a discrepancy of the order of 30% in favour of the latter when approximate allowance was made for the difference of pH and Cl− content in the two cases. This 30% difference might be reduced if exact corrections could be applied.4. No significant difference was observed between the rates of the carbamino CO2 reactions in concentrated Hb solutions and red cell suspensions, provided that approximate allowance was made for differences of pH in both cases.5. The rate of carbamino combination with Hb appeared to be about twice that with HbO2 at the same pH. Possible explanations for this difference are discussed.
Mammary and whole animal metabolism of glucose and fatty acids in fasting lactating goats
Authors: Annison E. F. , Linzell J. L. , West C. E. 
Published: December 2014

1. Measurements were made of milk yield, mammary blood flow and mammary arteriovenous differences during the measurement of substrate entry rate by the isotope dilution method using [U‐14C]glucose, acetate, palmitate, stearate or oleate in conscious lactating goats after 24 hr starvation.2. As previously reported, in fasting, milk yield fell to 40 ± 3·4 (
S.E.)%, lactose secretion to 31 ± 3·4%, milk fat secretion to 81 ± 6·7% and mammary blood flow fell to 53 ± 7·5% of the values before fasting. Mammary O2 uptake was only 45 ± 5% of the mean value in fed animals and there were marked falls in the uptakes of glucose, acetate and triglycerides, a smaller fall in β‐hydroxybutyrate uptake, and a large increase in free fatty acid uptake.3. Glucose was found to enter the circulation of the fasting animal at 1‐1·6 mg/min/kg body wt. (entry rate) and it gave rise to 3‐5% of the total CO2. The udder took up 10·7‐16·1 mg/min/kg of tissue and 8‐10% of mammary CO2 was derived from glucose, although only 5‐10% was oxidized. Mammary uptake accounted for 35‐43% of the total glucose entering the circulation.4. In the whole animal acetate entry rate was 1‐1·4 mg/min/kg and 9‐10% of total CO2 was derived from it. The udder used 0·8‐2·4 mg/min/kg of tissue and 9‐13% of mammary CO2 was derived from acetate, 46‐79% of that taken up being oxidized. Mammary uptake accounted for only 2‐6% of the total acetate entry rate. Negligible quantities of isotope were found in milk fatty acids and there was a fall in the proportion of milk fatty acids of chain length up to C14 which in fed animals are synthesized from acetate and β‐hydroxybutyrate.5. Palmitate, stearate and oleate entered the circulation as free fatty acids at 0·94‐6·8 mg/min/kg and 6‐9% of total CO2 was derived from each. The udder took up 3·0‐5·7 mg/min/kg of tissue and 4‐8% of mammary CO2 was derived from each acid. In the udder 8 and 5·5% of stearate and oleate were oxidized and 25% of palmitate. Mammary uptake of stearate was 31·5% of the total entry rate, palmitate 1%, and oleate 7·5%. Only long chain milk fatty acids were labelled.6. During fasting the mammary
R.Q. was 0·85 ± 0·045 compared with a value in fed animals of 1·24 ± 0·02, when the udder is synthesizing fatty acids from acetate. The total mammary uptake of lipid precursors was only 74% of the rate of milk fat secretion and there was an 18% shrinkage in empty udder volume, suggesting the use of endogenous mammary tissue substrates.
The after‐effects of repetitive stimulation on the isometric twitch contraction of rat fast skeletal muscle
Authors: Close R. , Hoh J. F. Y. 
Published: December 2014

1. The peak tension and time course of isometric twitch contractions of rat extensor digitorum longus muscle in vitro (35° C) have been measured at various stages of potentiation following repetitive stimulation at 20 c/s and 300 c/s.2. Potentiation of the peak twitch tension increases with an increase in the number of repetitive stimuli up to a maximal level of about 1·9 times the control value. The relation between potentiation and numbers of stimuli is dependent on the frequency of stimulation.3. Potentiation of peak twitch tension is maximal shortly after the end of repetitive stimulation and subsequently decays exponentially at a rate which is dependent on the number of stimuli in the train and the frequency of stimulation.4. Short trains of stimuli bring about nearly maximal potentiation with little or no change in contraction time and a small decrease in half‐relaxation time.5. Long trains of stimuli increase the contraction time, the half‐relaxation time and the twitch duration in addition to potentiating the peak tension. The changes in twitch time course are dependent on the number of repetitive stimuli and the frequency of stimulation.6. The results are discussed in relation to possible mechanisms of post‐tetanic potentiation and the degree of activation of mammalian and amphibian muscle fibres.
The effect of adrenaline on the tension developed in contractures and twitches of the ventricle of the frog
Authors: Graham J. A. , Lamb J. F. 
Published: December 2014

1. The effect of adrenaline on contracture and twitch tension in frog's ventricle has been examined, using the superfused preparation.2. In 1 m
M‐Ca Ringer, contractures induced with excess KCl concentrations from 50 to 200 m
M, are reduced by 1 × 10−6 g/ml. adrenaline to an average of 0·62 of control values, in marked contrast to the well known positive inotropic effect of adrenaline on the heart twitch. This effect of adrenaline is directly dose dependent. Increasing [Ca]o diminishes the effect of adrenaline on contracture tension, and on the twitch tension.3. Adrenaline has a significantly greater effect on the KCl contracture tension than noradrenaline or isoprenaline.4. In 1 m
M‐Ca Ringer, Na‐free contractures are reduced to 0·72 of controls by 1 × 10−6 g/ml. adrenaline. Adrenaline also significantly reduces tension in contractures induced by 50 c/s alternating current.5. The action of adrenaline on contracture tension is largely complete in 1–2 min at various rates of stimulation and calcium concentrations. A similar time course has been found for the effect of adrenaline on membrane potential.6. Pronethalol blocks the action of adrenaline on both twitch and contracture. The action on the contracture can also be blocked by ouabain (1 × 10−5
M), and exposure of the tissue to K‐free or Na‐free Ringer solution.7. Adrenaline hyperpolarizes the membrane potential with a range of [K]o from 0 to 200 m
M. This effect is blocked by pronethalol and ouabain. After exposure to ouabain, adrenaline causes a significant decrease in the membrane potential. This may be due to an increase in the sodium permeability.8. At low values of the [Ca]/[Na]2 ratio, adrenaline takes a relatively constant number of beats for full action, but at high values of the ratio the development of full effect is largely time dependent.9. The time course of the effect on the twitch of changing from 0·5 to 2 m
M‐Ca Ringer has been studied at various rates of stimulation. The equilibration time has been found to depend on the heart rate.10. The effect on the contracture suggests that adrenaline decreases the calcium permeability. It is further suggested that the development of twitch tension is not due to direct Ca entry but is due to the release of Ca from a local store within or between the cells. The inotropic action of adrenaline is explained in terms of this store.
The minimum latency of the a‐wave
Authors: Arden G. B. , Ikeda Hisako 
Published: December 2014

1. Intense flashes of light evoke early and late receptor potentials from albino rat eyes.2. When the temperature is lowered the amplitude of the early receptor potential (e.r.p.) is found to decrease much more than that of the a‐wave. Below 5° the a‐wave can be seen without a preceding negative e.r.p.3. The a‐wave, but not the e.r.p., is suppressed by an intense flash, so that subsequent stimuli only evoke e.r.p.s.4. The responses of such light‐adapted eyes have been used to determine the contribution of the a‐wave to the response of dark‐adapted eyes.5. These calculated a‐waves begin during the e.r.p. with an initial portion which is biphasic.6. The initial portion has a temperature dependence similar to that of the a‐wave. It is not related to the photoreversal of rhodopsin caused by the stimulating flashes.7. The minimum latency of the a‐wave, extrapolated to body temperature, is approximately 300 μsec.8. The site and mode of generation of the a‐wave is discussed.
Myelinated afferent fibres innervating the primate skin and their response to noxious stimuli
Authors: Perl E. R. 
Published: December 2014

1. The functional characteristics of cutaneous receptors in the squirrel monkey were determined by recording discharges of single myelinated afferent fibres in peripheral nerves with micro‐electrodes or from fine filaments prepared by dissection. One hundred and sixty‐nine fibres of the posterior femoral cutaneous nerve and 209 of the superficial radial nerve with conduction velocities between 4 and 88 m/sec were classified according to the nature of the most effective stimulus, discharge characteristics, adaptation rate and organization of the receptive field.2. Twenty per cent of the fibres innervating either hairy or glabrous skin required strong mechanical stimuli for activation; thresholds ranged from moderate to overtly damaging pressures. This class showed little or no sensitivity to thermal changes including noxious heat. Their receptive fields consisted of numerous, mechanically‐excitable points or spots. All such fibres gave higher impulse frequencies to noxious than to innocuous mechanical stimuli and a large fraction were considered to be nociceptors because they responded only to noxious deformation. The conduction velocities of nociceptors were distributed between 5 and 28 m/sec.3. All but a few of the other fibres encountered responded vigorously to innocuous stimuli and were readily identified as corresponding to one of the receptor types known to exist in either the primate or the cat. These sensitive receptors were systematically tested by intense cutaneous stimuli; their response to injurious stimuli always could be mimicked by innocuous ones.4. Therefore, in the primate a particular class of slowly‐conducting myelinated fibres is partially responsible for signalling mechanically‐induced cutaneous damage. The probable relation between such afferent fibres and certain kinds of cutaneous pain is explored.
An examination of the effects of osmotic pressure changes upon transmitter release from mammalian motor nerve terminals
Authors: Hubbard J. I. , Jones S. F. , Landau E. M. 
Published: December 2014

1. When the frequency of miniature end‐plate potentials (m.e.p.p.s) was measured at neuromuscular junctions in rat diaphragm nerve preparations in vitro bathed in solutions having osmolarities between 200 and 700 m‐osmoles/l. it was found that m.e.p.p. frequency was transiently increased by exposure to osmotic gradients exceeding 75 m‐osmoles/l., and then declined, within 1 hr, to a steady level slightly higher than the control level of frequency. Smaller osmotic gradients caused a maintained increase in m.e.p.p. frequency. E.p.p. quantal content was initially increased and later profoundly decreased upon exposure of preparations to solutions with an osmotic pressure of 500 or 600 m‐osmoles/l. but was unaffected by less hypertonic solutions.2. Variation of the Ca or Mg content of the bathing solutions did not alter these effects of osmotic pressure on the early transient increase in m.e.p.p. frequency or e.p.p. quantal content but affected the late steady increase in m.e.p.p. frequency.3. The value of the transient increase in m.e.p.p. frequency was exponentially related to the osmotic gradient in the range 0‐300 m‐osmoles/l. with a Q10 of 1·95 (range 11‐34° C). Greater osmotic gradients did not further increase m.e.p.p. frequency. Variation of the ionic strength of the bathing medium did not influence osmotic effects upon frequency.4. The discrepancy between the effects of osmotic gradients upon spontaneous and nerve‐impulse induced transmitter release was explained by an occlusion of the osmotic effects by depolarization of nerve terminals. Time‐course studies showed that in the presence of 20 m
M‐KCl the m.e.p.p. frequency increase in response to an increase in osmotic pressure was small and was followed by a reduction in frequency to below control levels while osmotic pressure changes had no immediate effect upon m.e.p.p. frequency in solutions containing 30 m
M‐KCl.5. It was concluded that increased osmotic gradients could release transmitter by a mechanism independent of Ca and of nerve terminal depolarization.6. It is suggested that the initial transient effects of changes of osmotic gradient upon transmitter release are related to flow of water through the nerve terminal membrane, while the later effects are related to nerve terminal volume changes.
The responses of goats to the experimental induction of hypocalcaemia with cation‐exchange columns
Authors: Symonds H. W. , Treacher R. J. 
Published: December 2014

1. Ionic calcium was selectively removed from the circulating blood of three anaesthetized goats by means of columns of cation‐exchange resin. Concentrations of other ions were not directly affected by the column.2. A calcium extraction rate of 0·35 m‐equiv/min caused a fall in plasma total calcium of up to 40% in 35 min. Plasma calcium concentration returned to normal within 2 hr of the end of calcium removal.3. Mobilization rates reached a maximum between 15 and 20 min after calcium removal commenced, declining rapidly after it had stopped.4. Removal of calcium by EDTA infusion results in a similar calcium mobilization pattern to that produced by Ca removal by ion‐exchange.5. A smaller variation appears to exist between goats in maximum calcium mobilization rates than in maximum phosphorus mobilization rates and goats may be able to mobilize phosphorus relatively faster than calcium.
The mechanism of the pyrogenic effect of streptococcus cell wall mucopeptide
Authors: Mašek K. , Rašková Helena , Rotta J. 
Published: December 2014

1. The intravenous injection into rabbits of 25‐50 μg of a preparation of cell‐wall mucopeptide (SM) from group A streptococcus produced a rise in rectal temperature and a fall in the number of circulating granulocytes in the blood.2. The pyrogenic response to SM is not dependent on the circulating granulocytes since it occurred also in rabbits made leucopenic by nitrogen mustard (HN 3).3. The pyrogenic response to SM was enhanced after an intravenous injection of 5‐hydroxytryptophan (5‐HTP).4. Pre‐treatment with reserpine caused a much greater attenuation of the pyrogenic response to SM than pre‐treatment with α‐methyl‐para‐tyrosine (AMPT).5. As the reserpine reduced the 5‐hydroxytryptamine (5‐HT) and noradrenaline level in the hypothalamus, whereas the AMPT reduced only the noradrenaline level, it is concluded that 5‐HT may be involved in the pyrogenic response and the way in which 5‐HT may exert this function is discussed.
Compensatory reactions to a lack of metabolizable glucose
Authors: Himsworth R. L. 
Published: December 2014

1. Following the injection of adrenaline into rats pre‐treated with thyroxine, there is a pronounced and prolonged increase in their oxygen consumption. On this basis a method is described for following increases in the rate of secretion of adrenaline in response to physiological stimuli in rats.2. Using this method the onset and the cessation of the increased rate of secretion of adrenaline during insulin induced hypoglycaemia has been found to correspond to a blood glucose concentration of approximately 40 mg/100 ml.3. 3‐Methylglucose (3‐O‐methyl‐
D‐glucopyranose) is shown to cause a marked and sustained increase in the blood glucose concentration.4. This action of 3‐methylglucose can be accounted for by an increase in the rate of secretion of adrenaline, as it is accompanied by a rise in oxygen consumption in thyroid treated rats and is prevented by interruption of the central nervous connexions of the adrenal medulla.5. These findings can be explained by 3‐methylglucose's acting upon the receptor which reacts to insulin hypoglycaemia by bringing about the secretion of adrenaline. It is shown that the effective stimulus to this receptor is not a low blood glucose concentration. The stimulus is possibly a depressed rate of utilization of glucose by the receptor tissue.
The effect of prolonged exercise on the components of the blood fibrinolytic enzyme system
Authors: Bennett N. B. , Ogston C. Marie , Ogston D. 
Published: December 2014

1. The levels of the blood components of the fibrinolytic enzyme system were measured before, during and after a 4 hr period of exercise in eight subjects.2. Mean plasminogen activator level rose progressively over the first 3 hr with little further change during the 4th hr of exercise. Following the period of exercise there was a rise in a circulating anti‐activator which was still present 20 hr after completion of the exercise.3. There was no alteration in the mean blood level of plasminogen, fibrinogen, anti‐plasmin or a serum inhibitor of plasminogen activation during or following the exercise.4. The significance of the findings in relation to the mechanism of interaction of the components of the fibrinolytic system is discussed.
The role of left atrial receptors in the diuretic response to left atrial distension
Authors: Ledsome J. R. , Linden R. J. 
Published: December 2014

1. The diuretic response to distension of the whole left atrium caused by obstruction of the mitral orifice has been compared with the effects of distension (by means of small balloons) of the left pulmonary vein/left atrial junctions.2. Distension of the pulmonary vein/atrial junctions caused an increase in heart rate and a diuresis similar to but smaller than that caused by mitral obstruction.3. Section of both ansae subclaviae prevented the increase in heart rate produced by distension of the pulmonary vein/left atrial junctions but had little effect on the diuretic response either to pulmonary vein distension or to mitral obstruction.4. A diuretic response to mitral obstruction could be demonstrated after all nerves from the lungs had been cut but not after the vagus nerves had been cut at levels likely to interrupt the majority of afferent fibres from left atrial receptors.5. The results support the view that stimulation of left atrial receptors is a major factor in the production of a diuretic response to mitral obstruction.