bluuebunny/crossref_metadata_2025_split huggingface dataset:
Onset of contractility in cardiac muscle
Authors: Brady Allan J. 
Published: December 2014

1. A technique is described whereby (i) quick stretches and releases of controlled velocity, amplitude and time of onset can be applied to muscle. (ii) Releases from isometric to isotonic contraction can be performed at controlled delays relative to the stimulus, and displayed on a delayed expanded oscilloscope sweep. An isotonic lever system with an equivalent mass of 12·8 mg is described.2. Quick stretch of rabbit or cat papillary muscle after excitation does not result in a level of tension equal to or greater than normal peak isometric tension appropriate to the stretched length. Stretches applied during the first half of the rising phase of tension development give responses nearly identical to the same stretches applied before the stimulus (indicating that Starling's Law of the heart holds until this time). Stretches applied in the later phase of tension development or during relaxation result in diminished peak isometric tensions or accelerated relaxation.3. The rate of tension development following quick releases of isometrically contracting muscle to zero tension is not maximal until the releases are made 150‐200 msec after excitation.4. Shortening velocity with light afterloads is not initially maximal nor constant for an appreciable period of time. The shortening velocity with heavy afterloads reaches its maximum more rapidly when the load is not lifted within the first 200 msec of a contraction which, if maintained isometric, would have required 400‐500 msec to reach peak tension. With these heavier loads, a period of 100‐200 msec of constant shortening velocity may occur.5. Freeloaded isotonic contractions show an inflexion in their shortening curves occurring 150‐200 msec after excitation.6. Maximum rate of isotonic shortening following releases from isometric to isotonic contraction with a given load is not maximal until the releases occur about 200 msec after the stimulus.7. It is concluded that contractility in cardiac muscle is relatively slow in its onset with maximum capacity to shorten occurring about midway through the rising phase of isometric tension development.
Chemoreceptor reflexes in the new‐born infant: effects of varying degrees of hypoxia on heart rate and ventilation in a warm environment*
Authors: Brady June P. , Ceruti Eliana 
Published: December 2014

1. We studied the effects of varying degrees of hypoxia for 3 min periods on the heart rate and respiration of thirty‐three healthy full‐term infants in a warm environment.2. During the first 5 days of life a decrease in alveolar oxygen tension (PA, CO2) below 80 mm Hg induced hyperventilation, a decreased alveolar carbon dioxide tension (PA, CO2), and tachycardia during the first minute of hypoxia. During the second and third minute, while the decreased PA, CO2 and tachycardia persisted, ventilation fell. There was a further fall in ventilation when the baby breathed 21% O2 again. This response was also observed when the inspired gas was heated to 35° C.3. During the first 5 days of life a decrease in PA, CO2 between 81 and 100 mm Hg did not affect ventilation or PA, CO2 during the first minute of hypoxia, but still induced a tachycardia and a fall in minute volume during the second and third minute.4. When the PA, CO2 was elevated and maintained constant during hypoxia, ventilation increased during the first minute and fell during the second and third minutes, suggesting that hypocapnia did not explain the transient ventilatory response to hypoxia.5. After the first week of life a greater and maintained increase in ventilation was seen during hypoxia. This response was potentiated by the addition of CO2.6. The possibility that changes in the pulmonary circulation, associated with a functionally patent ductus arteriosus, may explain these differences, is discussed.
The effect of cortisol on the haematocrit values and serum electrolytes of the adult and foetal rat
Authors: Seller Mary J. 
Published: December 2014

1. The serum sodium, potassium and chloride levels of the non‐pregnant rat, pregnant rat and foetus were estimated under normal circumstances and following the administration of 3 mg/kg cortisol to the non‐pregnant and pregnant rat.2. Normally, the electrolytes and haematocrit value of the non‐pregnant rat and the electrolytes of the foetus were higher than those occurring in the pregnant rat.3. After treatment with cortisol, the sodium, potassium and chloride content of the serum, and the haematocrit value of the non‐pregnant rat dropped significantly. There was no change in these values in the pregnant animals, but the foetus showed a significant decrease in sodium, potassium and chloride levels after maternal treatment.
Analysis of actions of 5‐hydroxytryptamine in pregnancy
Authors: Robson J. M. , Sullivan F. M. 
Published: December 2014

1. When 5‐hydroxytryptamine creatinine sulphate is injected subcutaneously in a dose of 2 mg into mice during the second half of pregnancy, the foetuses die within 1 hr. The mode of action of 5‐hydroxytryptamine (5‐HT) in producing this effect has been studied.2. It has been demonstrated that this is not a direct toxic effect of 5‐HT. Very little passes through the placenta into the foetus, and after the injection of much larger amounts directly into the foetus no lethal effect was observed.3. It was shown that 5‐HT had little effect on uterine motility in vivo, and that the much larger contractions produced by oxytocin did not produce any effect on the foetus.4. No constriction of the umbilical vessels was produced by 5‐HT injected into the mother, nor did the local application of 5‐HT to the cord produce any effect.5. The administration of 5‐HT to the mother markedly reduced the passage of 22Na from the maternal circulation into the placenta and foetus. This was accompanied by a reduction in the blood supply to the placenta from a normal value of 87 μl./min/g to 4 μg/min/g.6. It is suggested that the effect of 5‐HT in producing foetal death is a consequence of the reduction in the transfer function of the placenta.
The effect of previous stimulation of the adrenal cortex by adrenocorticotrophin on the function of the pituitary—adrenocortical axis in response to stress
Authors: Jones M. T. , Stockham M. A. 
Published: December 2014

1. There appear to be at least two peripheral regulators affecting normal physiological adrenal function during repeated stimulation with adrenocorticotrophin (ACTH).2. There is a tachyphylaxis to ACTH if the stimulation of the adrenal gland is frequent. This may be due to alteration or saturation of the trapping mechanism for acceptance of ACTH by the tissue. There also may be inhibitors at the adrenal level. The results obtained could also be explained on the basis of end product inhibition by corticosterone on the process of synthesis or by the presence of a destructive enzyme for ACTH.3. If the amounts of ACTH released or injected are sufficiently great the gland is capable of synthesizing more steroid but adrenocortical dynamics do not allow an immediate release of the steroid into the peripheral circulation. Thereby high levels of steroid in the plasma are maintained for longer periods rather than increased.
The permeability of the gastric mucosa of dog
Authors: Altamirano M. , Martinoya C. 
Published: December 2014

1. Tritiated water, [14C]urea, [14C]thiourea, [14C]sucrose and [59Fe]‐haemoglobin were used to study the permeability of a semi‐isolated piece of the great curvature of the canine stomach.2. The osmotic pressure of the solutions placed in contact with the secretory surface of the epithelium was changed by means of dextrose or urea. The mucosa behaved as a semi‐permeable membrane, meaning that water flowed under gradients of osmotic pressure. Regardless of the solute used, about 45 × 10−6 ml. of water flowed/cm2/min under a gradient of one atmosphere.3. The permeability constants of the probing molecules were determined under zero net volume flow obtained by placing isosmotic dextrose or isosmotic urea in the chamber. The constants decreased as the molecular volume of the probing molecules increased.4. The transport of all the non‐electrolytes across the epithelium decreased significantly when the chamber contained isosmotic dextrose. Basically, this effect seems to be a result of the reduction of the area available for diffusion caused by the high molecular volume of dextrose.5. The increased hindrance to diffusion of the probing molecules caused by the added solutes is considered as good evidence that the probing molecules diffuse by way of pores filled with water.6. The equation derived by Renkin (1954) fits the results obtained if we assume that the equivalent membrane has pores of at least two different radii. The calculated radii vary somewhat with the solute placed in the chamber, though about 88% of the area available for diffusion consists of pores with radii smaller than 2·5 Å.7. The equivalent pore radius, calculated from Kedem & Katchalsky's (1961) formula for pores of one single radius, contradicts some experimental findings. Once again, the results obtained would be reproduced more accurately by an equivalent membrane pierced by parallel pores of at least two different diameters.8. A procedure is suggested for calculating the proportion of pores of different radii. It seems likely that the pore radii vary in a continuous distribution from the large pores which allow the diffusion of haemoglobin, to pores hardly permitting the passage of water. The wide pores would form a small fraction of the total area available for the diffusion of water.
Appearance of 5‐hydroxytryptamine and an unidentified pharmacologically active lipid acid in effluent from perfused cerebral ventricles
Authors: Feldberg W. , Myers R. D. 
Published: December 2014

1. In cats anaesthetized with intraperitoneal pentobarbitone sodium, three regions of the cerebral ventricles, the third ventricle, the inferior or the anterior horn, were perfused with artificial c.s.f. and the effluent was tested on the fundus strip of the rat's stomach.2. Effluent from all three regions contracted the fundus strip. The contractions were due to at least two substances as revealed by treatment of the strip with 2‐bromolysergic acid diethylamide (BOL). The contractions that were sensitive to BOL are attributed to 5‐hydroxytryptamine (5‐HT) whereas the BOL resistant contractions appear to be due to an unknown hydroxy acid related to irin or the prostaglandins.3. The contractions produced by effluent collected from the third ventricle were due wholly or mainly to 5‐HT, those from the inferior horn to the unknown hydroxy acid, and those from the anterior horn to both substances in varying proportions. In addition, some samples of effluent from the third ventricle seemed to contain catecholamines as well.4. The 5‐HT in the effluent from the third ventricle is thought to be derived from the hypothalamus. The amounts assayed in 1 ml. effluent—the volume collected during 10 or 20 min perfusion—varied between 0·4 and 12 ng 5‐HT. Output of 5‐HT was initially high, then usually decreased but sometimes increased again during prolonged perfusion when temperature began to rise as anaesthesia lightened or when additional pentobarbitone sodium was given intravenously.5. When perfusion of the third ventricle was continued after death the 5‐HT content in the effluent increased 3 to 24‐fold during the first hour and then gradually declined. This post mortem rise in 5‐HT output suggests an abnormal state of release of 5‐HT from the hypothalamus. The theory is discussed that the same may happen in certain cases of brain injury and that the abnormal release of 5‐HT would explain the pyrexia and shivering seen in such cases.6. The intraperitoneal injection of 5‐hydroxytryptophan greatly increased the output of 5‐HT in the effluent from the perfused third ventricle but only when this precursor of 5‐HT was injected in large doses which caused respiratory arrest thus necessitating artificial ventilation. Upon the injection of 150 mg/kg the output of 5‐HT rose to 90 ng/ml. and a further rise to 180 ng/ml. occurred when perfusion was continued after death.7. It was not possible to establish a relation between the presence of the hydroxy acid in the effluent from the inferior horn and neuronal activity.8. The 5‐HT detected in the effluent from the anterior horn is assumed to have been released from the caudate nucleus.
Nerve implants in botulinum poisoned mammalian muscle
Authors: Fex S. , Sonesson B. , Thesleff S. , Zelená Jirina 
Published: December 2014

1. In albino rats the botulinum poisoned gastrocnemius muscle was supplied with an accessory motor nerve in order to investigate whether muscle fibres with structurally intact but non‐transmitting synapses would accept additional innervation. As a control similar operations were made in unpoisoned rats.2. One to three months after nerve implantation the muscles were examined histologically for the presence of a new end‐plate zone. In botulinum treated muscles 1662 ± 165 (mean ±
S.D.) of new end‐plates were found. In the control animals only a few (90 ± 13) were observed in the immediate vicinity of the implanted nerve trunk.3. Following recovery from the paralysing action of botulinum toxin electrical stimulation of both the implanted and the original motor nerve evoked strong mechanical twitches in the gastrocnemius muscle.4. When the nerves were stimulated simultaneously little or no summation of tension occurred, indicating that presumably many of the muscle fibres with new end‐plates also had functionally intact junctions from the original nerve. The presence of two end‐plates in a muscle fibre was confirmed in a few experiments on single curarized fibres by intracellular recording of end‐plate potentials on stimulation of each nerve.
Sodium depletion of pregnant ewes and its effects on foetuses and foetal fluids
Authors: Phillips G. D. , Sundaram S. K. 
Published: December 2014

1. Some effects of sodium depletion were investigated in sheep at different stages of pregnancy ranging from 55 to 139 days. Sodium depletion was induced by draining the saliva from one parotid gland for a period of 6 days. Foetal samples were collected at the end of the depletion period.2. Sodium depletion of the ewe resulted in a fall in saliva Na+ level and a rise in saliva K+ level, a fall in plasma Na+ and K+ levels, a 35% reduction in plasma volume and a 16% reduction in body weight.3. In the Na+ depleted ewes the sodium levels of the foetal plasma and amniotic fluid were lower and the volume of the allantoic fluid greater than those in the control ewes.4. It is concluded that sodium depletion of the ewe leads to a deficiency of sodium in the foetus.5. On the basis of these experiments and other reports it is postulated that a sodium deficient foetus, like a sodium deficient adult, responds to the deficiency by restricting sodium losses in the urine and by excreting water.
The influences of adrenolytic drugs and noradrenaline on the histamine release in cardiac anaphylaxis in vitro
Authors: Giotti A. , Guidotti A. , Mannaioni P. F. , Zilletti Lucilla 
Published: December 2014

1. The regional distribution (auricles, ventricles and septum) of histamine and its release during anaphylaxis were studied in isolated perfused guinea‐pig hearts.2. The highest value of histamine content was found in the right auricle, the lowest in the left ventricle and septum, both in normal hearts, and in the hearts subjected to anaphylaxis.3. The fraction of the total histamine released in the course of 24 min by antigen was 50%. The fraction released from the different regions of the heart was similar. No evidence was found for release of 5‐hydroxytryptamine.4. A relation was found between the distribution of mast cells and the tissue concentration of histamine. The highest number of mast cells per unit area was found in the right auricle; the lowest in the left ventricle.5. The histamine release by antigen was reduced by previous treatment with (+)‐tubocurarine; the histamine release by (+)‐tubocurarine was depressed by previous challenge of the heart with antigen.6. Reserpine reduces histamine release. Perfusion of reserpine‐treated hearts with noradrenaline partially restored histamine release.7. β‐Adrenergic blocking agents (dichloroisoproterenol and pronethalol) reduced histamine release.8. The drugs tested did not modify the tissue concentration of histamine.9. The possibility of a modulating activity of catecholamines on histamine release in cardiac anaphylaxis is discussed.
The influence of thyroid gland on amino acid accumulation and protein synthesis by rat small intestine in vitro
Authors: Bronk J. R. , Parsons D. S. 
Published: December 2014

1. A method is described for measuring the accumulation of amino acids and also the extent to which the absorbed amino acids are incorporated into the tissue protein of rings of rat intestine in vitro.2. With this method rat jejunum was found to accumulate a mixture of amino acids to give a concentration in the tissue water which was 2‐3 times that in the medium after 8 min incubation. More than 10% of the absorbed amino acids were found to be incorporated into protein.3. In surgically thyroidectomized animals there was no impairment of the capacity of the intestine to accumulate amino acids nor was there any loss of ability to incorporate these amino acids into protein. Similarly, treatment of the thyroidectomized animals with 3,5,3′‐triiodothyronine (T3) did not produce any significant change either in the rate of accumulation or in the extent of the incorporation of the amino acids.4. The omission of glucose from the incubation medium was found to cause a large increase in the respiration of mucosal slices in the presence of the amino acid mixture. Thyroidectomy significantly reduced this high respiration rate. Treatment of thyroidectomized animals with T3 restored the respiration to high value.
Amino acid accumulation and incorporation in rat intestine in vitro
Authors: Bronk J. R. , Parsons D. S. 
Published: December 2014

1. Rings of rat jejunum incubated in vitro accumulate a mixture of amino acids at a rate of about 3 μmoles/cm. hr. The rate of incorporation of the accumulated amino acid into the tissue protein corresponds to a rate of synthesis of 50% of the protein of the whole wall in five days.2. Replacement of the Na+ in the NaCl of the incubation medium by choline or by Li+ did not prevent amino acid accumulation by the tissue. However, replacement of the Na+ by K+ prevented the accumulation.3. The accumulation of amino acids by rat jejunum in vitro proceeded at normal rates not only in the presence in the incubation medium of oxygen tensions below 10 Torr but also in the presence of 2,4‐dinitrophenol. Reasons are given for supposing that the findings are compatible with the view that the energy upon which depend the processes of amino acid accumulation by the tissue could be derived from the movement of ions across cellular boundaries.4. The amino acid incorporation into the tissue proteins was reduced to one tenth of the control rate in the presence of 2,4‐dinitrophenol or by hypoxia so that the processes of incorporation depend upon energy derived from oxidative metabolism. In the presence of oligomycin the tissue respiration was depressed but the amino acid incorporation into the tissue protein was not inhibited. The view that the amino acid incorporation may be able to function with energy intermediates other than ATP is discussed.
Experiments on the genesis of bubbles as a result of rapid decompression
Authors: Lever M. J. , Miller K. W. , Paton W. D. M. , Smith E. B. 
Published: December 2014

1. The time course of intravascular bubble formation in mice after rapid decompression from 150 Lb/sq. in. has been followed in vivo in a flap preparation of thoracic and abdominal skin.2. Gas appeared first in the arteries, moving distally after a latent period of 3 min or more. Then bubbles appeared, moving centrally, in the venous system.3. The arterial bubbles could not be attributed to air forced into the circulation from the lungs or lumen of the gut.
The effects of arginine deficiency on the water and solute metabolism in weanling rats
Authors: Bentley P. J. , Ferguson D. R. , McGowan G. K. 
Published: December 2014

1. Weanling rats fed on a synthetic diet, which was completely deficient in arginine, grew more slowly than rats fed on a similar diet which included arginine.2. No differences in the haemoglobin level or plasma protein concentration or electrophoretic pattern were found in the two groups of rats.3. The arginine‐deficient rats drank less water, and excreted less urine, which was more concentrated than that of the control animals, although the solute output was reduced, and the extrarenal water losses were the same.4. The arginine‐deficient animals excreted less urea, non‐protein nitrogen, creatinine and total solutes. The blood urea concentration of the deficient animals was significantly higher than that of the controls, indicating that arginine deficiency had impaired the excretion of urea.5. There was no difference between the renal weights of both groups of animals when related to total body weight, nor was there a difference in the histological appearance of the kidneys.6. The amounts of arginine vasopression and oxytocin/kg body wt. stored in the neurohypophyses of both arginine‐deficient and control animals were the same.
Asphyxial potentials of spinal grey matter, and of ventral and dorsal roots
Authors: Biersteker P. A. , Collewijn H. , Van Harreveld A. 
Published: December 2014

1. Asphyxial potentials of short latency (from a few to about 10 sec) were recorded with mono‐ and bipolar electrodes from the cat's spinal cord. Monopolarly, a zone of maximum negativity was found somewhat dorsal of the central canal in the dorsal horn. With bipolar leads potentials of opposite polarity were observed in the dorsal and ventral horns. In the dorsal horn the more ventral electrode tip became negative with respect to the more dorsal one, in the ventral horn the more ventral tip became more positive. In the centre of the cord where the monopolar potential showed a maximum the bipolar potentials were small in either direction, or reversed during asphyxiation.2. These observations can be explained by the development of two independent dipoles of opposite polarity, located in the dorsal and ventral horn respectively, oriented with their negative poles towards the centre of the cord.3. In the ventral as well as in the dorsal root a negativity of a proximal electrode with respect to a more distal one developed during asphyxiation after the same latency as the asphyxial cord potentials. The asphyxial root potentials continued to grow during periods of asphyxiation as long as 30 min, and recovered promptly upon re‐oxygenation.4. Ventral and dorsal root potentials were abolished by asphyxiation of the cord for a period of 60 min, 2 weeks previously. This procedure destroys practically all the neurones, but not the dorsal root fibres. The dorsal root potential, but not the ventral one, was abolished by extradural sectioning of the roots, 2 weeks previously.5. The asphyxial ventral and dorsal root potentials were interpreted as the result of depolarization of the intraspinal part of the motoneurones and primary afferent endings respectively, conducted electrotonically along the roots. The short latency of these potentials suggests that an early depolarization of motoneurone, and of the primary afferent end knobs occurs. The latter, which may have some relation to presynaptic inhibition, explains the early failure of synaptic conduction during acute asphyxiation.