bluuebunny/crossref_metadata_2025_split huggingface dataset:
The reflex cardiovascular depression caused by occlusion of the coronary sinus in the dog
Authors: Muers M. F. , Sleight P. 
Published: December 2014

1. Brief occlusions of the outflow from the cannulated coronary sinus in the open chest anaesthetized dog caused a rise in coronary venous pressure, bradycardia, and systemic hypotension.2. The bradycardia and hypotension were directly proportional to the peak systolic coronary venous pressures above a threshold value of about 50 mm Hg.3. The bradycardia, but not the systemic hypotension, was abolished by intravenous atropine. Both responses were abolished by cutting the cervical vagi, and reversibly abolished by cooling them to less than 7° C.4. During occlusions, there was inhibition of activity in single and small multi‐fibre preparations of sympathetic efferent nerves in the ansae subclaviae and the cervical sympathetic.5. On the right side, nearly all afferent fibres ran in the recurrent cardiac nerve. There was no concentration of afferents in one cardiac nerve on the left side.6. It was concluded that the cardiovascular depression was reflex, and was caused by the stimulation of nerves or nerve endings in the ventricles of the heart.
Action potentials from ventricular mechanoreceptors stimulated by occlusion of the coronary sinus in the dog
Authors: Muers M. F. , Sleight P. 
Published: December 2014

1. In experiments to determine the type of intra‐cardiac receptors which cause the coronary sinus occlusion reflex, recordings were made from sixty‐nine single and small multi‐fibre preparations of cardiac vagal afferents in open‐chest anaesthetized dogs.2. Thirty‐two fibres were stimulated by occlusion of the coronary sinus outflow through an indwelling Morawitz cannula. No receptors were stimulated during occlusions at peak systolic coronary venous pressures below the threshold for reflex cardiovascular depression. At higher pressures, fibre recruitment and further increases in stimulated discharge were demonstrated.3. The afferent endings of twenty‐nine of these fibres were mechanically localized to the epicardium and myocardium of the left ventricle. Three were in the right ventricle. Seventeen single fibres discharged spontaneously at an average of 0·9 impulses/sec. There was cardiac modulation of both resting and stimulated discharge, with most action potentials in systole. Seven of eight fibres conducted at less than 1·0 m/sec.4. These ventricular receptors and a further twenty‐two otherwise like them but not stimulated by occlusions were designated epi‐myocardial receptors.5. 73% of receptors were stimulated by intrapericardial nicotine (50–100 μg). Presumptively superficial receptors were more sensitive to this stimulus.6. Epi‐myocardial receptors were stimulated by intravenous or intracoronary catecholamines, by electrical stimulation of cardiac sympathetic nerves, and by eliciting the carotid sinus occlusion reflex. Aortic occlusion stimulated 66% of fibres tested, but was a less effective stimulus. After all these stimuli, there was a systolic modulation of discharge in more than 70% of fibres.7. It was concluded that the epi‐myocardial receptors are similar to those previously shown to cause the epicardial chemoreflex, and to participate in the coronary chemoreflex. It is suggested that they are responsive to systolic mechanical changes which are accentuated by catecholamines. Their possible effectiveness in other cardiac reflexes and in initiating circulatory changes at the beginning of exercise and the vasovagal syndrome is discussed.
The mechanism of adenosine diphosphate induced platelet aggregation: binding to platelet receptors and inhibition of binding and aggregation by prostaglandin E1
Authors: Boullin D. J. , Green A. R. , Price K. S. 
Published: December 2014

1. Normal human blood platelets in stirred plasma were incubated with [14C]ADP for 10–360 sec and the aggregation responses were correlated with platelet bound radioactivity, the platelets being separated from the plasma within 25 sec of the end of the experiment.2. The platelet aggregation response, measured as a change in light transmittance through platelet‐rich plasma, was related to the plasma [14C]ADP concentration and linearly related to the log platelet bound [14C]ADP 60–120 sec after addition of nucleotide to plasma.3. Thin layer chromatography of the platelet bound radioactivity showed that 78–90% was unmetabolized ADP, the remainder being AMP. Plasma radioactivity consisted of ADP, AMP and adenosine. There was no detectable radioactive cyclic AMP in either platelets or plasma.4. Further accumulation of radioactivity occurred after 180 sec but was not related to the aggregation response.5. Prostaglandin E1 inhibited aggregation and platelet [14C]ADP accumulation when added to platelet‐rich plasma 60 sec before [14C]ADP. There was a significant correlation between inhibition of aggregation and inhibition of [14C]ADP accumulation.6. Prostaglandin E1 also reversed ADP aggregation when added to platelet‐rich plasma after the nucleotide, with an accompanying decrease in platelet bound [14C]ADP.7. It is concluded that ADP induces platelet aggregation by binding to specific receptors probably located on the plasma membrane, and that prostaglandin E1 inhibits this effect by interfering with the ADP binding.
Changes during eating in oxygen consumption, cardiac function and body fluids of sheep
Authors: Christopherson R. J. , Webster A. J. F. 
Published: December 2014

1. A study was made of the changes taking place in O2 consumption, cardiac function and the volume and composition of the body fluids of sheep while they consumed a meal of hay.2. During eating Pa, CO2 and Pv, CO2 both increased, pH decreased and free plasma [HCO3−] increased. Venous haematocrit increased sharply at the beginning of the meal, and declined slowly after feed was removed.3. Arterial PO2 did not change significantly during eating. However Pv, O2 fell slightly but significantly. The O2 saturation of venous blood fell due to the decline in pH. Estimated CO2 in arterial blood increased as a consequence of increased haemoglobin content. The net effect was to increase arteriovenous difference in O2 content from 4·4 ml./100 ml. before eating to 6·0 ml./100 ml. at the end of the meal.4. O2 consumption increased about 60% during eating and fell rapidly thereafter. Heart rate followed a similar pattern. Cardiac output however increased only about 17%, from 6 to 7 l./min. Consequently stroke volume declined throughout the meal from 76 to 52 ml./beat.5. Plasma volume, estimated from measurements of T‐1824, declined sharply by about 300 ml. at the beginning of the meal and recovered slowly after feed was removed. Blood volume declined less because of a rise in circulating erythrocytes.6. Extracellular fluid volume was estimated from measurements of thiocyanate and thiosulphate spaces. Thiocyanate space measurements were abandoned after thiocyanate was found to be concentrated in saliva. Considerable random variation occurred in measurements of changes in extracellular fluid from thiosulphate disappearance but the results did reveal a significant fall of 1000–1500 ml. in extracellular fluid volume during eating.7. The significance of these interrelated changes is discussed in relation to the maintenance of homoeostasis during eating in the sheep.
Coronary vasodilator responses to hypoxia before and after aminophylline
Authors: Afonso S. , Ansfield T. J. , Berndt T. B. , Rowe G. G. 
Published: December 2014

1. In previous studies adenosine has been postulated to be the mediator in coronary blood flow regulation and aminophylline was found to inhibit the coronary vasodilator action of adenosine. The present study was performed to determine whether aminophylline inhibits coronary vasodilatation induced by hypoxia.2. Coronary and systemic haemodynamic and metabolic effects of hypoxia were studied in anaesthetized dogs before and after aminophylline. Aminophylline did not influence coronary vasodilatation induced by hypoxia.3. These results are held not to lend support to the hypothesis that adenosine is the metabolite responsible for the regulation of coronary blood flow.
Transcapillary fluid movement in human calf after drinking hypertonic saline
Authors: Matsubara I. 
Published: December 2014

1. Transcapillary absorption of interstitial fluid was demonstrated with a pressure plethysmograph applied to the human calf after the ingestion of 200 ml. hypertonic (5·1%) saline. Capillary absorption began within 15 min after ingestion and lasted for about 2 hr. The maximum rate of absorption (0·019 ml./min. 100 ml. tissue) was attained 30–75 min after ingestion.2. The total amount of fluid absorbed into capillary blood vessels in the calf was 1·11 ml./100 ml. tissue. The amount of fluid thus absorbed in the whole body was estimated to be 677 ml.3. The capillary filtration coefficient (CFC) of the calf was also measured by the pressure plethysmograph. This was 0·0038 ml./min. mm Hg. 100 ml. tissue.4. The peak value of capillary absorption pressure was 5·2 mm Hg.5. The total osmotic pressure of the plasma rose by 12·6 m‐osmole/kg H2O after ingestion. This rise was accompanied by transcapillary fluid absorption.6. The plasma protein concentration and packed cell volume were almost unchanged by ingestion, indicating that the plasma volume was unaltered.7. It was estimated that the net shift of fluid between intracellular and interstitial compartments during the period of transcapillary fluid absorption was very small.8. It is concluded that the volume of fluid moving from plasma into intestinal lumen is the same as that flowing from interstitial fluid into plasma, and that the transcapillary absorption is caused by a difference in osmotic pressure between the plasma and the interstitial fluid.
Electrical properties of white and red muscle fibres of the elasmobranch fish Scyliorhinus canicula
Authors: Stanfield P. R. 
Published: December 2014

1. Standard electrophysiological techniques (including a method which controls the membrane potential at a point on a muscle fibre) were used to investigate the electrical properties of white and red muscle fibres of the elasmobranch fish Scyliorhinus canicula.2. The resting potential of the white fibres in the standard Ringer solution was — 85·2 ± 0·4 mV. That of the red fibres was — 71·1 ± 1·2 mV. The membrane resistance of white fibres was 1588 ± 97 Ω cm2 and that of red fibres was 5410 ± 1070 Ω cm2.3. White fibres always responded to direct stimulation with an action potential. It proved impossible, with two impaling micro‐electrodes, to record action potentials from the red fibres, although on one occasion an abortive spike was seen.4. The resting membrane of the red fibres seemed less permeable to chloride than was the membrane of the white fibres. However, the resting potassium permeability showed the potential dependence called inward or anomalous rectification in both white and red fibres.5. White fibres responded to square depolarizing pulses with conductance changes to sodium and, subsequently, to potassium.6. All red fibres examined with the point voltage clamp showed a delayed increase in potassium conductance on depolarizing.7. Out of twenty‐seven red fibres examined, six showed no sign of having any sodium conductance mechanism. Eight showed large sodium currents on depolarizing, and the remaining thirteen had small sodium currents. It seemed likely that the group of eight fibres might be able to propagate action potentials.
Effects of intracerebral micro‐injection of sodium salicylate on temperature regulation in the rabbit
Authors: Cranston W. I. , Rawlins M. D. 
Published: December 2014

1. Symmetrical, bilateral micro‐injections (10 μl.) of 6–30 μg sodium salicylate have been made into various parts of the brains of febrile and afebrile rabbits.2. In rabbits with fever induced by an intravenous infusion of endogenous pyrogen, micro‐injections of sodium salicylate produced antipyresis when given into the preoptic hypothalamus and the mid‐brain.3. In afebrile rabbits, micro‐injections of sodium salicylate into these areas were without effect on temperature.4. The results suggest that at least part of the antipyretic effect of salicylates may be mediated by antagonizing the effects of endogenous pyrogen within these areas of the brain.
The effect of efferent discharges in renal nerves on the activity of arterial mechanoreceptors in the kidney in rabbit
Authors: Niijima Akira 
Published: December 2014

1. The effect of sympathetic efferent flow in renal nerves on afferent discharges from renal arterial mechanoreceptors was observed in dissected filaments of renal nerves in the rabbit.2. An increase in afferent discharge rate was observed after renal nerve stimulation.3. Perfusate accumulated during renal nerve stimulation in an isolated kidney preparation showed a vasoconstrictor effect on blood vessels in rabbit ear.4. Infusion of a small amount of (±)‐noradrenaline increased afferent discharge rate.5. Modification of blood pressure levels by chemical means modified renal afferent discharge rate.6. It is suggested that there is an efferent control mechanism on the activity of renal arterial mechanoreceptors by a vasomotor reflex.
Effects of stimulation of efferent fibres of the vagus on the reticulo‐omasal orifice of the sheep
Authors: Newhook J. C. , Titchen D. A. 
Published: December 2014

1. The reticulo‐omasal orifice has been observed and its activity recorded in decerebrate and spinal preparations of lambs and in lambs and sheep anaesthetized with chloralose.2. Spontaneous closure movements at about 6/min were seen, or recorded from balloons placed in the orifice in all types of preparation when both vagus nerves had been cut and after atropine, hexamethonium, phentolamine and propranolol had been given
I.V.3. The effects on the reticulo‐omasal orifice of stimulation in the neck of efferent fibres of the vagus nerves on either side differed according to the form of the stimulus applied.4. Threshold stimulation of the vagus nerve caused closing of the orifice which was blocked by atropine.5. Opening of the orifice and disappearance of spontaneous closing movements followed more intense stimulation of the vagus nerves.6. Vagal opening effects were obtained after atropine was given and after adrenergic opening and closure effects had been blocked with phentolamine and propranolol.
Kinetics of slow thermal reactions during the bleaching of rhodopsin in the perfused frog retina
Authors: Baumann C. 
Published: December 2014

1. Slow thermal reactions occurring in the rhodopsin rods of flash‐irradiated frog retinas were investigated spectrophotometrically.2. Five substances were identified as reactants: metarhodopsin II, metarhodopsin III, all‐trans‐retinal, opsin, and all‐trans‐retinol.3. Quantitative analysis showed that the transition between these substances are not a series of three consecutive reactions.4. An alternative scheme, compatible with the results, consisted of four reactions and involved two parallel pathways for the decay of metarhodopsin II, viz. conversion into metarhodopsin III, and hydrolysis into retinal and opsin.5. The first‐order rate constants for the four reactions were as follows: 1·4 × 10−2 sec−1 for the conversion of metarhodopsin II into metarhodopsin III; 7·9 × 10−3 sec−1 for the hydrolysis of metarhodopsin II; 1·4 × 10−3 sec−1 for the hydrolysis of metarhodopsin III; and 2·6 × 10−3 sec−1 for the reduction of retinal into retinol (21° C).6. Two other four‐parameter schemes involving an equilibrium between metarhodopsin II and metarhodopsin III were also considered. One was found to be incompatible with the results. The other, though adequate, did not describe the data as well as the model summarized in 4 and 5. It also had the peculiar property of requiring that two apparently independent parameters be equated.
Counting every quantum
Authors: Sakitt B. 
Published: December 2014

1. Human subjects were asked to rate both blanks and very dim flashes of light under conditions of complete dark adaptation at 7° in the periphery. The ratings used were 0, 1, 2, 3, 4, 5, and 6.2. For one subject (B.S.) the distributions of ratings were approximately Poisson distributions. The data were consistent with each rating being the actual number of effective quantal absorptions plus the number of noise events. This subject was presumably able to count every rod signal (effective absorptions plus noise).3. For two other subjects, the data were consistent with the ratings being one less (L.F.) and two less (K.D.) than the number of effective absorptions plus noise. They were able to count every rod signal beginning with 2 and 3 respectively. A fourth subject's erratic data could not be fitted.4. The fraction of quanta incident at the cornea that resulted in a rod signal was estimated to be about 0·03 which is consistent with physical estimates of effective absorption for that retinal region.5. A simulated forced choice experiment leads to an absolute threshold about 0·40 log units below the normal yes‐no absolute threshold. This and other results indicate that subjects can use the sensory information they receive even when only 1, 2 or 3 quanta are effectively absorbed, depending on the individual. Humans may be able to count every action potential or every discrete burst of action potentials in some critical neurone.
Ionic permeability changes as the basis of the thermal dependence of the resting potential in barnacle muscle fibres
Authors: Fischbarg Jorge 
Published: December 2014

1. The thermal dependence of the resting potential of isolated barnacle muscle fibres was larger (1–2 mV/° C) than predicted by Nernst's equation (about 0·2 mV/° C). A comparative study was made of the influence on thermal dependence of parameters related to (a) passive permeability and to (b) Na extrusion.2. High [K]o decreased the thermal dependence reversibly. [Ki], [Na]i and [Cl]i were determined by chemical analysis, and Goldman's equation was fitted to data relating V to [K]o at different temperatures, in the presence and absence of ouabain 5 × 10−5
M. In both cases the behaviour of V when T was lowered from 20 to 4° C was accounted for by increases in the calculated PNa/PK and PCl/PK (from 0·006 to 0·043 and from 0·17 to 0·34 on the average, respectively.)3. Other parameters related to passive permeability (and which caused reversible depolarization): decreased [Cl]o (methanesulphonate or gluconate substituted), and decreased pHo (below 5·0), also decreased the thermal dependence reversibly.4. Inhibitors (ouabain 5 × 10−5
M, cyanide 2–10 × 10−3
M, 2,4‐dinitrophenol 2 × 10−4
M) externally applied did not affect either resting potential or its thermal dependence for several hours.5. Increasing [Na]i three‐ to fourfold by intracellular injection decreased both resting potential and its thermal dependence.6. Although a small effect by a Na electrogenic pump cannot be excluded, the largest part of the thermal effect on the resting potential is concluded to depend on temperature‐induced variations in relative ionic permeabilities to cations and anions. A model is proposed which can account for the data assuming that (a) each permeant ion associates to a separate site in the membrane, and (b) the ion‐site equilibrium is temperature‐dependent.
Reflex cardiovascular and respiratory responses originating in exercising muscle
Authors: McCloskey D. I. , Mitchell J. H. 
Published: December 2014

1. In anaesthetized and decerebrate cats isometric exercise of the hind limb muscles was elicited by stimulating the spinal ventral roots L7‐S1. This caused a rise in arterial blood pressure, with small increases in heart rate and pulmonary ventilation. These changes were abolished by cutting the dorsal roots receiving afferents from the exercising muscle.2. When the triceps surae muscle was made to exercise by ventral root stimulation, occlusion of the femoral artery and vein through and beyond the period of exercise caused the blood pressure to remain raised until the occlusion was removed. The ventilatory and heart rate responses were not markedly altered or prolonged by such circulatory occlusion.3. Injection of small volumes of 5% NaCl or isotonic KCl into the arterial blood supplying hind limb muscles gave cardiovascular and respiratory responses similar to those evoked by exercise. Like the responses to exercise, these responses were abolished by dorsal root section.4. Direct current anodal block of the dorsal roots receiving afferents from the exercising muscle was used to block preferentially large myelinated fibres: this form of block did not abolish the evoked cardiovascular and respiratory responses. Local anaesthetic block of the dorsal roots was used to block preferentially unmyelinated and small myelinated fibres: this form of block abolished the cardiovascular and respiratory responses. It is concluded that the reflex responses are mediated by fibres within groups III and IV (small myelinated fibres and unmyelinated fibres).
The formation of a renally active peptide by cat lungs from γ‐globulin in vitro and the plasma concentrations of this peptide, in vivo
Authors: Lockett Mary F. 
Published: December 2014

1. A substance (LS), extracted in aqueous acetone and separated by partition and thin‐layer chromatography, has been obtained from lung perfusates and from the systemic blood of cats.2. LS is assayed biologically in rats during sustained saline diuresis by measurement of the μequiv Na retained. This parameter is linearly related to the log concentration of LS infused.3. Lungs perfused with Tyrode fluid neither contain nor produce LS. Production of LS begins when γ‐globulins (in cat plasma, mixed ox globulins or equine Cohn II) are present in the perfusing fluid.4. The proteinase inhibitor trasylol does not prevent the formation of LS by lung; trasylol protects LS from break‐down during re‐perfusion and during isolation from perfusates or from blood.5. In cats under chloralose anaesthesia LS is present during haemorrhage in systemic arterial and mixed venous blood, the arterial concentration of LS is approximately four times the venous.
Extracellular cations and the movement of choline across the erythrocyte membrane
Authors: Martin K. 
Published: December 2014

1. The ability of human erythrocytes to accumulate choline is abolished when external Na is replaced by Cs, Rb, K or Li but is increased when the external cation is Mg or Ca.2. The unidirectional influx of choline is reduced when external Na is replaced by other monovalent cations but is not changed when Na is replaced by Mg or Ca.3. The unidirectional efflux of choline into a choline‐free medium is increased when external Na is replaced by other monovalent cations and markedly reduced when Na is replaced by Mg or Ca. When the external medium contains 1 m
M choline, changing the external cation has virtually no effect on the rate of choline efflux.4. When the extracellular concentrations of K and Na are similar to that found in the intracellular water, choline appears to become passively distributed across the cell membrane; when the extracellular K is then replaced by Cs a net efflux of choline against a concentration gradient results.5. It is concluded that the choline carrier may be described as a cation carrier with a high affinity for choline and affinities for Cs > Rb > K > Li > Na and that these monovalent cations can cross the membrane on the choline transport system.