bluuebunny/crossref_metadata_2025_split huggingface dataset:
The chemical and energetic properties of muscles poisoned with fluorodinitrobenzene
Authors: Dydyńska M. , Wilkie D. R. 
Published: December 2014

1. The heat production and mechanical responses of frogs' sartorii have been recorded at 0° C after immersion in normal Ringer solution, and also after poisoning with 1‐fluoro‐2, 4‐dinitrobenzene (FDNB) and nitrogen. The muscles were later analysed chemically for changes in ATP, phosphocreatine (PC), inorganic phosphate (Pi), lactate, total adenine nucleotide and total inosine nucleotide.2. Analysis of paired resting muscles established that the resting levels of these substances found in our experiments were similar to those reported elsewhere.3. Resting muscles that had been poisoned with FDNB and N2 contained significantly more PC and less ATP than unpoisoned controls. Moreover, some of their adenine had been deaminated to inosine.4. In a normal muscle in oxygen, the PC that breaks down as a result of a 30 sec tetanus is restored with a roughly exponential time course whose half‐time is about 10 min. Thus at least 40 min rest must be allowed between the different stages of an experiment.5. Isometric twitches of the poisoned muscle rapidly decline in size, but small twitches continue to be produced for a very long time. If stimulation is discontinued, substantial recovery takes place. The total tension development is equivalent to at least thirty normal twitches, and correspondingly, the total heat production is greater than could be accounted for even by complete break‐down of the ATP in the muscle. In fact, the ATP break‐down, though highly significant, is not nearly complete.6. In short series of isometric twitches there is significant break‐down of ATP and, less consistently, of PC; also a significant increase in Pi but no additional deamination of adenine. The rate of development of isometric tension is slightly decreased.7. The results described under (6) are definitely due to the presence of FDNB. In similar experiments with the muscles in N2 but not otherwise poisoned the only significant change is a break‐down of PC.8. In a long series of isotonic twitches the chemical effects are similar to those described under (5) and inosine formation is clearly demonstrable. The poisoned muscles show force—velocity curves of normal shape, the Fenn effect and the presence of shortening heat. Thus their contractions are normal or nearly so.9. The complexity of the chemical reactions that continue in the poisoned muscle makes it impossible to draw up an accurate energetic balance sheet.10. A new hypothesis is suggested to explain the energetic importance of inosine formation.
The effects of hypoxia in the new‐born lamb before and after denervation of the carotid chemoreceptors*
Authors: Purves M. J. 
Published: December 2014

1. Twenty‐seven unanaesthetized new‐born lambs, 6 hr‐10 days old, responded to two levels of inspired oxygen, 125 and 110 mm Hg (alveolar CO2 being controlled) with a sustained increase in minute ventilation (V̇), a small increase in heart rate and a less consistent rise in systemic blood pressure.2. An increase in V̇ was observed when arterial oxygen tension (Pa, O2) had fallen by 6‐15 mm Hg. There appeared to be no fixed threshold of Pa, O2 at which ventilation started to increase.3. The increase in ventilation caused by these levels of hypoxia was significantly and directly related to the age of the lamb and to its control alveolar CO2.4. More severe hypoxia caused a progressive increase in V̇ until Pa, O2 was about 25 mm Hg when respiration failed. This increase at Pa, O2 > 25 mm Hg was markedly potentiated when alveolar PCO2 (PA, CO2) was increased and abolished after bilateral denervation of the carotid chemoreceptors.5. Significant (> 10%) left‐to‐right shunts were found in ten out of twelve lambs lightly anaesthetized with pentobarbitone sodium, breathing air. Hypoxia diminished the left‐to‐right pressure gradient largely by its pressor effect on the pulmonary circulation. When inspired O2 tension (PI, O2) was 70 mm Hg, all seven lambs studied showed a reversal of the pressure gradient and evidence of right‐to‐left shunts (11‐42%) across the ductus arteriosus.6. The implications of these findings have been discussed with reference to previous studies of the new‐born response to hypoxia and it is concluded that the peripheral chemoreceptors are fully active at birth and in the new‐born period.
Nerve‐mediated excitation of the taenia of the guinea‐pig caecum
Authors: Campbell G. 
Published: December 2014

1. A study was made of the responses of the isolated taenia of the guinea‐pig caecum to stimulation of the intramural nerves.2. Four types of response are described, made up of a contraction and/or a relaxation occurring during stimulation and an after‐contraction occurring when stimulation is stopped.3. A delayed relaxation which sometimes occurred at the end of stimulation is also described.4. Atropine usually abolished the contractions occurring during stimulation. After‐contractions either appeared or were increased in amplitude in the presence of atropine, and delayed relaxations were abolished.5. The anti‐cholinesterase drug neostigmine could convert the response during stimulation from a relaxation to a contraction. After‐contractions were often abolished by neostigmine and delayed relaxations appeared.6. It is concluded that the contractions which occurred during stimulation were mediated by cholinergic nerves. The after‐contraction appears to be a rebound phenomenon, following the hyperpolarization of the muscle caused by stimulation of the inhibitory nerves. It is suggested that the delayed relaxation is caused by the effects of persisting inhibitory transmitter substance on cells which do not undergo rebound excitation.
The time course of early changes in the rate of tension development in electrically‐stimulated frog toe muscle: effects of muscle length, temperature and twitch‐potentiators
Authors: Foulks J. G. , Perry Florence A. 
Published: December 2014

1. An RC circuit employing a piezo‐electric crystal was used to differentiate the tension output of electrically stimulated frog toe muscle.2. The rate of tension development curves (dP/dt) usually displayed an initial step‐wise increase in the rate of tension development, and often showed further discernible steps in tension acceleration. The successive stages of tension acceleration tended to be equal in duration, and approximated the length of the latent period (ca. 4 msec at room temperature). These observations suggest a synchronous turnover of the links between the myofilaments during the initial interval following stimulation, with an over‐all cycle time at room temperature of about 8 msec.3. Lowering the temperature produced proportionate alterations in the duration as well as the magnitude of each successive phase of tension development, with a Q10 of approximately 2.4. Characteristic changes in the pattern of tension generation were seen with alterations in muscle length, and at lengths greater than 120% of the standard length the irregularities in the dP/dt curves disappeared and the rate of tension development increased in linear fashion. This behaviour could be accounted for by the hypothetical S‐filaments connecting the free ends of the thin actin filaments across the H‐zone.5. The effects of nine twitch potentiators were studied. Only perchlorate produced prominent increases in the earliest phase of tension development and in maximum tetanus tension—properties expected with an increase in the excitation‐induced release of calcium ion into the sarcoplasm (increased intensity of the ‘active state’).6. The time of onset of the increases in tension acceleration which were produced by twitch potentiators did not correlate with their capacity to lower the ‘mechanical threshold’, indicating that the amount of calcium released by the action potential is not necessarily altered by a shift in the membrane potential at which calcium release occurs.7. All potentiators studied proved capable of (a) augmenting the rate of increase of tension generation (slope of dP/dt curves) during their rapid phase, as well as (b) increasing the interval during which the dP/dt curves for twitch and tetanus coincide. These effects occurred separately. It is suggested that both of these effects may be explained on the basis of delayed removal of sarcoplasmic calcium ion, resulting in prolongation of the ‘active state’.
Analysis of some central actions of nicotine injected into the cerebral ventricles of cats
Authors: Hall G. H. , Reit E. 
Published: December 2014

1. In unanaesthetized cats intraventricular injections of 2·5‐10 μg nicotine produced blinking, narrowing of the palpebral fissures, retching, vomiting and asynchronous twitching of the ears. With larger doses (30‐100 μg) the ear twitching was interrupted for a short time by laying back of the ears. Respiration first became laboured and deep, then rapid and shallow following which panting occurred. There was salivation, loud calling, micturition and defaecation. With still larger doses (300‐1000 μg) there was torticollis, ataxia and blind charging sometimes followed by a clonic‐tonic convulsion.2. In cats anaesthetized with chloralose only some of these effects followed the intraventricular injection of nicotine, i.e. the ear response, respiratory changes and salivation. In addition, the pinna reflex was facilitated.3. The ear response and the facilitation of the pinna reflex did not occur on perfusion of nicotine from a lateral ventricle to aqueduct. They result from an action on superficial structures in the cervical cord between C1 and C2. Applied to this region of the cord, nicotine produced the ear response within 10‐60 sec, sometimes in concentrations as low as 1/100,000. Applied below C2, nicotine was ineffective.4. Transecting the cord below C2 or cutting the dorsal and ventral roots of C1, C2 and C3 bilaterally did not affect the ear response produced by topical application or by intraventricular injection of nicotine. Transection of the cord above C1 abolished it.5. Hexamethonium applied to the cervical cord between C1 and C2 inhibited the ear response and the facilitation of the pinna reflex whether produced by nicotine applied topically or injected intraventricularly.6. The salivation and the respiratory changes produced by intraventricular injections of nicotine did not occur when nicotine was perfused from a lateral ventricle to the aqueduct. They result from an action of the nicotine on structures situated superficially in the brain stem. Nicotine had no sialogogue or respiratory effect when applied to the region of the cord at which it produced an ear response, but perfused through the subarachnoid space from interpeduncular fossa to cisterna magna or injected into the subarachnoid space alongside the brain stem, it produced these effects.7. Hexamethonium perfused from interpeduncular fossa to cisterna magna inhibited the salivary secretion as well as the respiratory changes produced by nicotine similarly applied.8. The efferent pathway for the salivation is parasympathetic since it no longer occurred after cutting the chorda‐lingual nerve or after intravenous atropine.9. Intravenous injections of nicotine also produced the ear response with facilitation of the pinna reflex, salivation and hyperventilation in the anaesthetized cat, but only the ear response and facilitation of the pinna reflex are central effects. The salivation and hyperventilation following intravenous injection are due to peripheral actions of nicotine.
Electrical properties of the smooth muscle membrane of the guinea‐pig vas deferens
Authors: Hashimoto Y. , Holman Mollie E. , Tille J. 
Published: December 2014

1. The effects of polarizing current on single smooth muscle cells of the isolated guinea‐pig vas deferens have been studied by means of a bridge circuit in which the same electrode was used to pass current and record membrane potential.2. Most cells had polarization resistances from 15 to 37 MΩ.3. Depolarizing currents caused graded spikes up to a maximum amplitude of 75 mV.4. Self‐regenerative spikes occurred in some cells if the membrane was depolarized by > 35 mV.5. Currents of long duration and sufficient intensity caused a repetitive discharge.6. Spikes arising from excitatory junction potentials were always ‘all‐or‐none’ in contrast to the graded responses to intracellular stimulation.7. Electrotonic potentials declined much more rapidly than spontaneous excitatory junction potentials (EJPs); thus the time course of the EJP cannot be determined by the passive electrical properties of the smooth muscle cell membrane.
The blood flow and oxygen consumption of brown adipose tissue in the new‐born rabbit
Authors: Heim T. , Hull D. 
Published: December 2014

1. A direct method for measuring venous outflow from brown adipose tissue in anaesthetized new‐born rabbits is described.2. During noradrenaline infusion the mean blood flow through brown adipose tissue increased from 87 to 360 ml./100 g tissue (wet wt.).min, and the mean rate of oxygen consumption of brown adipose tissue rose from 9·3 to 60 ml. O2/100 g tissue.min.3. During cold exposure the mean blood flow through brown adipose tissue increased from 90 to 304 ml./100 g tissue.min.4. The mean cardiac output was 266 ml./kg body weight.min; during noradrenaline infusion it was 405 ml./kg body weight.min. At rest about one tenth, and during noradrenaline infusion about one quarter of the cardiac output went to brown adipose tissue.5. It was calculated that most of the extra oxygen consumed during the metabolic response of the anaesthetized new‐born rabbit to noradrenaline infusion or cold exposure was consumed by brown adipose tissue.6. Hypoxia (breathing 10% O2 in N2) greatly reduced the increase in oxygen consumption but not the increase in blood flow in brown adipose tissue caused by noradrenaline infusion.
An electrophysiological study of odour similarities of homologous substances
Authors: Döving K. B. 
Published: December 2014

1. The activity of single bulbar units in the olfactory system of the frog was recorded extracellularly by means of micro‐electrodes. The electro‐olfactogram was recorded simultaneously from the receptor epithelium.2. The olfactory epithelium was stimulated with substances of homologous series of normal aliphatic alcohols, acetates and ketones.3. The effect on a bulbar unit was classified as excitatory or inhibitory, and the chi‐square values calculated with one degree of freedom for all pairs in a given series. The statistical values obtained indicated the degree of similarity in olfactory stimulative properties between the odours.4. The results show that the degree of similarity in olfactory properties is greatest among neighbouring substances and gradually decreases with increasing separation in chain length.5. Significant rank correlation coefficients were found between the chi‐square values and the molecular weight ratios for alcohols and acetates. The results are discussed in relation to psychophysical findings obtained with the same substances.
Effect of amino acids on sugar absorption
Authors: Hindmarsh J. T. , Kilby D. , Wiseman G. 
Published: December 2014

1. Sacs of everted mid‐small intestine of the hamster have been used to study the effect of amino acids on sugar absorption.2. The sugars employed were
D‐glucose,
D‐galactose, 3‐O‐methyl‐
D‐glucose,
D‐fucose,
L‐glucose, α‐glucoheptose,
L‐fucose,
D‐mannose and
L‐sorbose. The amino acids were
L‐ and
D‐histidine,
L‐ and
D‐methionine,
L‐ and
D‐alanine,
L‐ and
D‐valine,
L‐ and
D‐glutamic acid,
L‐leucine,
L‐proline,
L‐ornithine and
L‐aspartic acid.3. Actively absorbed amino acids considerably inhibit the transport of actively absorbed sugars. The results give support for the view that
D‐histidine and
L‐glucose are actively transferred. Passively absorbed amino acids and sugars are not involved.4. As
L‐glutamic and
L‐aspartic acids in the mucosal fluid have no inhibitory effect on
D‐glucose absorption, although mucosal fluid
L‐alanine is quite potent, the step at which the latter exerts its inhibitory action must be before that at which the intracellular transamination of
L‐glutamic and
L‐aspartic acids occurs. It would seem likely, therefore, that
L‐alanine interferes with the process by which epithelial cells capture and concentrate sugars at the luminal border.5. More than one active transfer system may exist for
D‐glucose.6. The influence of actively absorbed
L‐amino acids on
D‐glucose active transport seems to be in some way related to the efficiency with which the amino acids are themselves concentrated.7. Inhibition of
D‐glucose active absorption by an amino acid may be a simple test of an amino acid's participation in an active transport system.
The effects of hyperventilation on the reflex cardiac response from the carotid bodies in the cat
Authors: Scott Mary J. 
Published: December 2014

1. Cats were anaesthetized with chloralose and urethane, and ventilated by an artificial intermittent negative pressure applied to the thorax. The carotid body chemoreceptors were isolated and perfused with oxygenated blood. They were stimulated by substituting hypoxic blood obtained from a donor animal.2. Stimulation of the carotid bodies during constant ventilation caused a bradycardia. When an artificial hyperventilation was induced during carotid body stimulation the heart rate increased.3. The increase in heart rate during hyperventilation, and while the carotid bodies were being stimulated, was due to at least two mechanisms, first a reflex from the lungs and secondly a fall in arterial blood PCO2, both of which accompany the hyperventilation.
Effects on temperature of monoamines injected into the cerebral ventricles of anaesthetized dogs
Authors: Feldberg W. , Hellon R. F. , Myers R. D. 
Published: December 2014

1. In dogs anaesthetized with pentobarbitone sodium an injection of adrenaline or noradrenaline into the cerebral ventricles through a cannula implanted into the left lateral ventricle caused a fall in rectal temperature as a result of cessation of shivering, loss of muscle tone, and skin vasodilatation. 5‐Hydroxytryptamine (5‐HT) similarly applied caused shivering and a rise in rectal temperature.2. The hypothalamus of the dog thus appears to react to the three monoamines in the same way as in the cat, and not as in the rabbit and sheep.
The effect of uranyl nitrate on intestinal transfer of hexoses
Authors: Newey H. , Sanford P. A. , Smyth D. H. 
Published: December 2014

1. Uranyl nitrate in a concentration of 3 × 10−4
M caused reduction in mucosal transfer of glucose but not of galactose nor 3‐O‐methyl‐glucose by sacs of rat everted intestine. At this concentration uranyl nitrate had little effect on glucose metabolism (measured by glucose disappearance).2. Uranyl nitrate in a concentration of 3 × 10−3
M caused reduction in transfer of glucose, galactose, 3‐O‐methyl‐glucose and fluid, and inhibited glucose metabolism.3. Uranyl nitrate did not inhibit entry of glucose into the intestine under anaerobic conditions.4. Glucose was found to inhibit or stimulate galactose transfer depending on the conditions. The inhibitory action is presumably by competition for a common carrier, whereas stimulation indicates that glucose metabolism can supply energy for galactose transfer.5. It is suggested that there are two different routes for glucose in the cell, one of which is uranyl sensitive and not used by galactose, and the other is uranyl insensitive and shared by both hexoses. The implications of this are discussed in relation to transport and metabolism.
Absence of adrenal influence on ovarian graft activity in male rats castrated at birth
Authors: Smith W. N. Adams 
Published: December 2014

1. An investigation was made to see whether the presence of the adrenal gland was necessary for cyclical activity of ovarian transplants in adult male rats which had been castrated at birth.2. Rats were castrated on the day of birth or at 6‐8 weeks of age and when 3 months old were adrenalectomized and had a transplant of immature ovary placed in the anterior chamber of one eye. Control animals were subjected to the same procedure apart from adrenalectomy.3. Transplants in rats castrated at birth were observed to undergo full cyclical activity, with follicular rupture and the formation of corpora lutea. Transplants in rats castrated at 6‐8 weeks of age did not cycle and corpora lutea were not formed.4. Adrenalectomy did not influence the behaviour of the ovarian transplants.5. It is concluded that the presence of the adrenal gland was not necessary to support cyclical activity in ovarian tissue transplants in male rats castrated at birth.
The release of acetylcholine from the spinal cord of the cat by antidromic stimulation of motor nerves
Authors: Kuno M. , Rudomin P. 
Published: December 2014

1. ACh was measured in the effluent from the perfused lumbosacral cord of the cat with or without stimulation of the central ends of the cut left sciatic and femoral nerves after section of the left dorsal roots.2. In about 30% of the preparations ACh was obtained in the samples collected at rest (average 3·3 ng/min); the amount of ACh release was increased 1·3‐9 times by stimulation of the peripheral nerves. The average amount of ACh collected during stimulation of the peripheral nerves at 5/sec was 6·9 ng/min. Antidromic motor nerve impulses responsible for the ACh release were likely to be only those in alpha motor fibres.3. There was a depression in ACh release/stimulus as the stimulus frequency was increased more than 10/sec. Such changes in ACh release with various stimulus frequencies were correlated with depression in the response of Renshaw cells to excitation through motor‐axon collaterals.4. Amounts of ACh release during stimulation of the peripheral nerves at 5/sec were significantly increased for 1 or 2 min after a short tetanic stimulation of the nerves.5. Intravenous injection of dihydro‐β‐erythroidine did not reduce the amount of ACh release produced by stimulation of the peripheral nerves.6. It is concluded that antidromic impulses in alpha motor fibres liberate ACh from the presynaptic terminals at the central synapses on Renshaw cells.
Mechanoreceptors in rabbit ear skin innervated by myelinated nerve fibres
Authors: Miller S. , Weddell G. 
Published: December 2014

1. The activity of single myelinated fibres innervating mechanosensitive units in the dorsal skin of the ears of New Zealand White and Chinchilla rabbits has been recorded with glass micropipette electrodes, inserted into intact bundles of the great auricular nerve.2. Only two types of afferent unit were observed: hair units, sensitive to hair displacement, and skin spot units, sensitive to deformation of spot‐like areas of skin between the hair orifices. Hair units were more numerous and no unit contained receptors of both types. Up to nine hairs or six skin spots composed each hair or skin spot unit, respectively. Both types were rapidly adapting.3. The areas of the receptive fields of the hair units were significantly larger in the New Zealand White than in the Chinchilla strain.4. In the hair units from the Chinchilla rabbits: (a) there was no correlation between the receptive field areas and the conduction velocities of the afferent fibres; (b) the areas and conduction velocities of the units showed no significant topographical distribution over the ear; (c) the extent of the overlap of the receptive fields was estimated and the sum of the areas is shown to be about 40 times the area of the ear.