bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of graded pulsatile pressure on the reflex vasomotor responses elicited by changes of mean pressure in the perfused carotid sinus‐aortic arch regions of the dog
Authors: James Jennifer E. Angell , Daly M. de Burgh 
Published: December 2014

1. In the anaesthetized dog, the carotid sinuses and aortic arch were isolated from the circulation and separately perfused with blood by a method which enabled the mean pressure, pulse pressure and pulse frequency to be varied independently in each vasosensory area. The systemic circulation was perfused at constant blood flow by means of a pump and the systemic venous blood was oxygenated by an extracorporeal isolated pump‐perfused donor lung preparation.2. We have confirmed our previous observations that under steadystate conditions the vasomotor responses elicited reflexly by changes in mean carotid sinus pressure are modified by alterations in carotid sinus pulse pressure, whereas those evoked by changes of mean aortic arch pressure are only weakly affected by modifications of aortic pulse pressure.3. When the carotid sinus and aortic arch regions are perfused in combination at constant pulse frequency (110 c/min), the relationship between mean carotid sinus‐aortic arch pressure and systemic arterial perfusion pressure is dependent on the size of the pulse pressure.4. Increasing the pulse pressure alters the curve relating the mean carotid sinus‐aortic arch pressure to systemic arterial perfusion pressure in such a way that the perfusion pressure is lower at a given carotid sinus‐aortic arch pressure within the range 80–150 mm Hg. The larger the pulse pressure, up to about 60 mm Hg, the greater the fall in systemic arterial perfusion pressure. Above a mean carotid sinus‐aortic arch pressure of about 150 mm Hg, alterations of pulse pressure have little effect.5. There is a family of curves representing the relation between mean carotid sinus‐aortic arch pressure and systemic vascular resistance, depending on the pulse pressure.
The effect of environmental conditions on the growth and function of brown adipose tissue
Authors: Hardman M. J. , Hull D. 
Published: December 2014

1. Rabbits were reared from birth under one of two contrasting conditions. They were either well‐fed and kept in a cool environment, or kept warm but fed on alternate days only. When they were a week old their metabolic responses to cold or the net exchanges of glucose, free fatty acid and glycerol by their brown adipose tissue in vivo before and during noradrenaline infusions were measured.2. The cold‐reared rabbits grew normally, the under‐fed rabbits were undersized; in both groups the brown adipose tissue wet weights were less than those normally found at birth. In cold‐reared rabbits this was due largely to the low fat content, in the under‐fed rabbits it was not.3. The rabbits' rates of oxygen consumption at a thermoneutral temperature and in response to cold was greater in the cold‐reared rabbits.4. The increase in temperature over brown adipose tissue and the increase in blood flow in response to noradrenaline infusion was also greater in the cold‐reared rabbits.5. Although the brown adipose tissue of cold‐reared rabbits contained 30% fat it did not release fatty acids 24 hr after a feed. In contrast the brown adipose tissue of the under‐fed rabbits released fatty acids at a high rate.6. It was concluded that both prolonged cold exposure and undernutrition influenced the function and development of brown adipose tissue during the first week of life. Cold exposure increases the thermogenic capacity of the tissue, undernutrition reduces it. The net release of fatty acids from brown adipose tissue, is, in part, dependent on the tissues' own intracellular requirements.
The distribution of chloride ions in the smooth muscle cells of the guinea‐pig's taenia coli
Authors: Casteels R. 
Published: December 2014

1. The intracellular Cl concentration of taenia coli cells, determined by an analytical procedure and by an extrapolation procedure, has a value between 60 and 73 m‐mole/l. cell water.2. This concentration is too high to be explained by a passive distribution. The discrepancy could be due to a binding of Cl in the intracellular or extracellular compartment or to an active uptake of Cl by the cells.3. Determination of the activity coefficient for Cl in homogenates of smooth muscle did not support the hypothesis of binding of Cl ions.4. The efflux of 36Cl from taenia coli cells was not affected by foreign anions. After 1 hr exposure to a Cl‐free solution, the tissues contained less than 1 m‐mole of Cl/kg wet wt., even if Cl had been replaced by a slowly penetrating anion. Because the intracellular cation concentration remained constant, it has to be assumed that new anionic groups can be formed in the cells.5. The intracellular Cl concentration decreases during exposure to ouabain or to K‐free solution. The uptake seems therefore to be linked to the uptake of K through the Na pump.6. Exposure to K‐free solution increases the K permeability of the membrane. Under the same experimental conditions the Cl permeability of the membrane increases as long as K is leaking out of the cells.7. The anions in the external solution exert an important influence on the K permeability of the membrane. NO3 and I cause a small increase of the permeability and large anions such as benzenesulphonate, propionate or pyroglutamate cause a pronounced decrease of this permeability.
The origin of lipoprotein in the intestinal and hepatic lymph of unsuckled new‐born calves
Authors: Lascelles A. K. , Wadsworth J. C. 
Published: December 2014

1. Experiments have been conducted to determine the origin and character of the lipid in thoracic duct lymph of new‐born, unsuckled calves. This involved the collection and analysis of intestinal and hepatic lymph from two bile‐fistulated and seven non‐fistulated animals.2. The output of total esterified fatty acid in intestinal and hepatic lymph in the unfed calf after recovery from the anaesthetic was about 0·6 and 0·025 g/hr, respectively.3. Three lipoprotein fractions were obtained by ultracentrifugation of intestinal lymph samples. These appeared to correspond to very low‐ (d < 1·005), low‐ (1·2 > d < 1·005) and high‐ (d = 1·20) density lipoprotein of human serum. These lipoproteins contained approximately 40%, 50% and 10% respectively of the total lipid.4. Very low‐density lipoprotein was not found in blood serum or hepatic lymph and it was evident that very low‐density lipoprotein and most of the low‐density lipoprotein in intestinal lymph were derived from sources other than the capillary filtrate.5. The output of total esterified fatty acid in intestinal lymph fell steadily during the course of an 11–16 hr period of bile deprivation to values 55% of those in comparable calves without bile fistulae. This was accompanied by a virtual disappearance of very low‐density lipoprotein and a decrease in low‐density lipoprotein of approximately 50%. These effects could not be attributed to starvation.6. There was a general resemblance in fatty‐acid composition between biliary lipid and the triglyceride of the lipoproteins, the predominant fatty acids being 16:0 and 18:1. The presence of appreciable levels of odd carbon number and branched‐chain fatty acids were consistent with the transfer of significant amounts of free fatty acid from maternal blood to the foetus.7. It is concluded that most of the lipid in thoracic‐duct lymph of unfed, new‐born calves is derived from the intestines and that the fatty acids of the very low‐density lipoprotein in intestinal lymph arise from the absorption of biliary phospholipid.
The influence of hepatic portal circulation on urine flow
Authors: Liang C. C. 
Published: December 2014

1. A study of the effect of changes in the hepatic portal venous pressure (HPVP) on the rate of urine flow in dogs has been made. Normally this pressure varies between 3·7 and 14·9 cm H2O. It can be raised or lowered by varying the method of manipulation of the visceral organs.2. When the HPVP was raised within 15 cm H2O above the premanipulation level it caused an increase in urine flow to 2‐3 times the normal levels within 2‐5 sec. If the HPVP was raised to more than 15 cm H2O above the pre‐manipulation levels it resulted in a period of antidiuresis. The urine flow returned rapidly to normal level immediately after the pressure was released.3. The kidney volume increased when an induced diuresis occurred and decreased when an antidiuresis occurred.4. The urine chloride concentration decreased during diuresis, but total chloride excretion increased. Total chloride excretion was reduced when an antidiuresis occurred.5. Topical application of local anaesthetics at the hilus of the kidney and on the renal nervous plexus abolished the response. This and other evidence indicate that this effect on urine flow is a result of nervous reflex activity, probably involving the sympathetic but not the vagus.6. The receptive area lies in the mesentery between the mesenteric capillaries and the main portal vein.
The effect of angiotensin on cation transport by rat kidney cortex slices
Authors: Munday K. A. , Parsons B. J. , Poat Judith A. 
Published: December 2014

1. A study has been made of the effect of angiotensin (10−12 g/ml.) on active and passive transport of sodium, potassium and water between rat kidney cortex slices and the incubation medium.2. Angiotensin has no effect on the passive uptake of sodium and loss of potassium by slices incubated under conditions which inhibit active transport.3. Active sodium extrusion by slices incubated under aerobic conditions is stimulated, whereas active potassium uptake is inhibited by angiotensin.4. Sodium pump activity is stimulated by angiotensin in the presence of ouabain or in the absence of potassium in the incubation medium, conditions which block the sodium for potassium exchange pump.5. There is a 2 min latent period following the application of angiotensin before a response is observed.6. These findings are discussed in relation to the mechanism of action of angiotensin on kidney sodium and fluid transport processes.
The propagation of transient potentials in some linear cable structures
Authors: Jack J. J. B. , Redman S. J. 
Published: December 2014

1. Analytical solutions have been given for the time course of voltage transients occurring in one‐dimensional cable structures, with linear uniform membrane properties.2. These solutions show how the time course of the voltage transients generated at different distances are affected by variations in the time course of current injection (at one point on the cable) and by alterations in the length of the cable, with either sealed or open end terminations. These effects are illustrated with computed results.3. Simple measurements from the time course of a membrane potential displacement, occurring in a one‐dimensional cable structure following a brief current injection across the membrane, are used to evaluate the parameters which describe the cable model. These parameters are the membrane time constant, the electrotonic length of the cable, the cable end termination, and in the case of a post‐synaptic potential, the distance between the electrode and the active synapse.
Coronary blood flow, oxygen delivery rate and cardiac performance
Authors: Bacaner Marvin B. , Lioy Franco , Visscher Maurice B. 
Published: December 2014

1. Studies have been made on the isolated blood‐perfused heart of dogs in which isometric tension development at various settings of resting tension (RT) was measured at various levels of O2 delivery rates controlled by altering (a) coronary blood flow (CBF), (b) O2 capacity or (c) O2 saturation of the perfusate. Measurements were also made of O2 consumption and vascular perfusion resistance.2. The capacity of the left ventricle to develop tension at any given setting of resting tension was found to be directly correlated with changes in O2 delivery rate using any of the above three methods of altering the latter.3. The slopes of the curves relating resting tension to developed tension are positively correlated with total O2 delivery to the heart.4. The O2‐dependent metabolic effect upon tension production was found to be slow in development, in contrast to the Frank—Starling effect, which reached full development in the first heart beat after a change in resting length and tension.5. The O2 consumption of the isometrically contracting heart is strongly correlated with the O2 delivery rate at all particular values of resting tension and related developed tension.6. The metabolic state of the myocardium as determined by the rate of O2 delivery within physiological ranges is (a) a direct major determinant of the tension‐producing capacity of the heart muscle and (b) determines the magnitude of adaptation via the Frank—Starling mechanism.
Plasma oxytocin concentration and paraventricular neurone activity in rats with diencephalic islands and intact brains
Authors: Dyball R. E. J. , Dyer R. G. 
Published: December 2014

1. Plasma oxytocin concentrations and the discharge rates of identified paraventricular neurones were compared in intact animals and diencephalic island preparations.2. Substantial amounts of oxytocin (88–322 μu./ml.) were found in the plasma of intact rats but in no case was it detected in the plasma of island preparations. The discharge rate of paraventricular units was also significantly reduced in these preparations.3. The results are consistent with the hypothesis that an increase in the discharge rate of paraventricular neurones is associated with oxytocin release from the neurohypophysis.4. The discharge rates of identified paraventricular units were not affected by intravenous injections of oxytocin either in intact animals or island preparations.
Movement of choline acetyltransferase in axons disconnected from their cell bodies
Authors: Ekström J. , Emmelin N. 
Published: December 2014

1. Phrenic nerves of rats were cut out and divided into two parts of equal length, one proximal and one distal. The activity of choline acetyltransferase of the two pieces was estimated. Four groups of rats were studied: (1) normal rats, and rats in which 3 days earlier, (2) the right nerve had been cut in the uppermost part of the thorax, (3) a ligature had been tied round the right nerve just above the diaphragm, and (4) these two procedures had been combined.2. In normal rats the activity of the enzyme was about the same in proximal and distal pieces. Ligation of the nerve caused an increase of the activity, of about 50%, in the distal but not in the proximal segment.3. After section of the nerve the activity below the section was 18% of normal in the proximal, and 9% in the distal piece.4. When the nerve was both cut and tied the activity decreased to the same level in both pieces, and this was about the level of the proximal piece after mere section of the nerve.5. It is concluded that choline acetyltransferase can move for some time along the axons to the nerve terminals even when the connexion with the soma has been interrupted.
Competitive interaction of β‐guanidino propionic acid and γ‐aminobutyric acid on the muscle fibre of the crayfish
Authors: Feltz Anne 
Published: December 2014

1. The interaction of β‐guanidino propionic acid and γ‐aminobutyric acid has been investigated on the crayfish muscle by measurement of the membrane conductance.2. The increase in membrane conductance produced by GABA is depressed by β‐guanidino propionic acid. This antagonist acts in a competitive way as shown by the shift of log dose—response curves and by the results of tests for competitive interaction (method of Schild (1947); Lineweaver and Burk's plot).3. Perfusion of GABA was shown to induce a receptor desensitization. As a consequence, the slope of the dose—response curve plotted in Hill's co‐ordinates increases when care is taken to minimize this phenomenon. The significance of this slope for establishing the real number of GABA molecules binding with the GABA receptor is discussed.
On the nature of the oscillations of the membrane potential (slow waves) produced by acetylcholine or carbachol in intestinal smooth muscle
Authors: Bolton T. B. 
Published: December 2014

1. Intracellular recording was made with glass micro‐electrodes from cells of the longitudinal muscle of the guinea‐pig ileum in isotonic and in hypertonic solution.2. In isotonic solution spontaneous bursts of electrical activity occurred; these consisted of a slow potential component which carried a burst of spike action potentials. Acetylcholine increased the size (and the frequency) of the slow potential component. This had the effect of first reducing and then abolishing the spike potentials; continuous slow wave activity was thus produced. Slow waves were about 1 sec in duration and up to 50 mV in size in isotonic solution.3. In hypertonic solution the membrane potential was stable. There were no spontaneous spikes and no slow potentials. However, spikes, but not slow potentials, were elicited by depolarizing current. Carbachol (or acetylcholine) reduced the membrane potential and initiated spikes and oscillations of the membrane potential (slow waves). Slow waves were 2‐5 sec in duration and 10–40 mV in size in hypertonic solution.4. The response to carbachol in hypertonic solution was unaffected by surgical denervation of the tissue, by tetrodotoxin, or by ganglion blocking agents, indicating that muscarinic stimulants produced their effects by acting directly on the smooth muscle cell.5. In hypertonic solution slow waves occurred only in the presence of a muscarinic stimulant and could not be elicited with depolarizing current (unless carbachol was present) nor by increasing the external potassium concentration.6. In hypertonic solution slow waves were abolished by hyperpolarizing the membrane and their rate of rise was proportional to the level of the membrane potential from which they arose. The membrane resistance was reduced at the peak of the slow wave. Slow waves were rapidly abolished by sodium‐deficient solutions but spikes were not.7. It is suggested that slow waves represent an inward current through a slow, sodium‐sensitive and voltage‐dependent ion channel, and that acetylcholine or carbachol increase, while hypertonic solution decreases, the current carried by this channel.
Metabolic rate and thermal insulation in albino and hairless mice
Authors: Mount L. E. 
Published: December 2014

1. Rates of oxygen consumption of albino and hairless mice were measured in a metabolism chamber during periods of approximately 5 or 24 hr. Rectal temperature was measured before and after each period. The chamber temperatures used were 22, 30 and 32° C for both albino and hairless, and in addition 34 and 36° C for the hairless mice.2. The mean age and body weight of the albino mice were 102 days and 34·6 g; the corresponding values for the hairless mice were 87 days and 32·8 g.3. The mean minimum rates of oxygen consumption (ml./kg.min) were 31·0 for the albino and 38·8 for the hairless mouse; the corresponding estimated critical temperatures were in the ranges 30–32° C for the albino mouse and 32–34° C for the hairless mouse.4. The mean values for core‐ambient thermal insulation (° C.m2.hr/kcal) were 0·418 and 0·328 for the albino mouse, and 0·275 and 0·221 for the hairless mouse, at 22 and 30° C respectively in each case.
The effect of type D botulinum toxin on frog neuromuscular junctions
Authors: Harris A. J. , Miledi R. 
Published: December 2014

1. Botulinum toxin type D blocks neuromuscular transmission in frogs. Motor nerve impulses continue to invade the nerve terminals but cease to evoke the phasic release of transmitter normally associated with them.2. Sensory receptors in the muscle continue to generate impulses even after 4 days of continuous exposure to botulinum toxin.3. Contrary to expectations, spontaneous miniature end‐plate potentials did not disappear completely after botulinum intoxication; they still occurred, although with reduced frequency, in most end‐plates. These miniature potentials had a skew amplitude distribution instead of the bell‐shaped distribution of normal end‐plates.4. The electron‐microscopic appearance of botulinum‐poisoned end‐plates was not obviously altered.5. Even though after botulinum nerve impulses fail to release transmitter, tetanic nerve stimulation causes an increase in the frequency of miniature end‐plate potentials. Many of the unit potentials which appear during the tetanic period are of an amplitude which is larger than that of spontaneous potentials, indicating that a different class of unit is being released preferentially. Some implications of this finding are briefly discussed.
Chemical change and energy output during muscular contraction
Authors: Gilbert Claude , Kretzschmar K. M. , Wilkie D. R. , Woledge R. C. 
Published: December 2014

1. The production of heat and (internal) work and the changes in the amount of phosphocreatine (PCr), ATP, inorganic phosphate (Pi) and sometimes lactate have been measured from moment to moment during and after tetanic isometric contractions of isolated frog muscles at 0° C.2. Heat production was measured by thermopiles and a novel apparatus was employed for freezing the muscles rapidly at a chosen instant so as to halt the chemical processes before analysis.3. Using unpoisoned muscles in oxygen, it was shown that neither oxidative recovery processes nor glycolytic ones led to appreciable restitution of PCr or ATP during 15 sec of contraction. However, clear signs of recovery processes could be seen within a minute. In our preparations artificial ‘ageing’ by storage at low temperature did not interfere with the capacity for glycolysis.4. Our clearest result was that the break‐down of PCr was not nearly large enough to account for the rapid heat production during the first few sec of contraction. By the end of a 15 sec tetanus as much as 10 mcal/g remained unaccounted for.5. The source of this heat is not clear. At no time is there any sign of net break‐down of ATP; indeed there appears to be a slight increase of ATP in the stimulated muscle.6. Break‐down of PCr continues both during relaxation and during the minute following, while the muscle is at rest. Thus during contraction there is heat production without PCr break‐down, while subsequently there is PCr break‐down without heat production.
Nucleotide requirements for sodium‐sodium exchange catalysed by the sodium pump in human red cells
Authors: Glynn I. M. , Hoffman J. F. 
Published: December 2014

1. Resealed red cell ghosts containing a variety of nucleoside triphosphates, or a mixture of tri‐ and diphosphates, were allowed to lose 24Na into a 10 m
M‐K medium or a K‐free high‐Na medium in the presence and absence of ouabain.2. Only ATP supported a ouabain‐sensitive Na:K exchange in the 10 m
M‐K medium, or a ouabain‐sensitive Na:Na exchange in the K‐free medium.3. Because of ATPase and adenylate kinase activity, it is difficult to control the levels of ATP and ADP inside resealed red cell ghosts. Some control was achieved by incorporating into the ghosts an ATP regenerating system consisting of creatine phosphate and creatine kinase.4. Measurements of 24Na efflux from ghosts prepared in this way showed that ADP is required for the ouabain‐sensitive exchange of Na that occurs in K‐free high‐Na media, but not for the normal exchange of Na for K that occurs in K‐containing media.5. The significance of these findings is discussed.