bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanism of compensatory renal hypertrophy
Authors: Dicker S. E. , Shirley D. G. 
Published: December 2014

1. Adult rats were unilaterally nephrectomized and the weight of the remaining kidney up to 42 days after the operation compared with that of rats of comparable weight which underwent a sham operation.2. After unilateral nephrectomy the rate of renal hypertrophy varied with the protein content of the diet: it was faster when animals were fed on a high protein diet (22% casein) and lowest in animals fed on a low protein diet (7% casein).3. In rats fed on a standard diet (18% casein), after unilateral nephrectomy there was a sharp increase in glomerular filtration rate (
G.F.R.), as measured by inulin clearance estimations; this was accompanied by an enhanced oxygen uptake and by an increase of RNA/DNA ratios in the renal cortex. Changes in rate of oxygen uptake and of RNA/DNA ratios in the medulla were negligible.4. A marked increase in mitotic activity of cells of the cortex occurred only 48 hr after the operation. It lasted for about 2 days. No significant changes in mitotic activity of cells in the medulla were observed.5. After its initial marked rise glomerular filtration rate in the renoprival kidney settled down to about 30–40% above its pre‐operative level, and remained at that level for the whole period of observation (6 weeks), while the increase of oxygen uptake returned to its control level in some 10–14 days. RNA/DNA ratios in the cortex remained high, but did not increase further.6. The increase of RNA/DNA ratios in the renal cortex was correlated with a steady increase in the dry weight of the renoprival kidney.7. Water and solutes excretion were restored to normal in about 3‐5 days after the operation.8. Though the increase in glomerular filtration rate may be the prime mover in the mechanism of compensatory renal hypertrophy, it does not explain why there is an increase in the size of tubules.
Further studies on prostaglandin E1 fever in cats
Authors: Feldberg W. , Saxena P. N. 
Published: December 2014

1. Micro‐injections of a few nanograms of prostaglandin E1 (PGE1) into the anterior hypothalamus of unanaesthetized cats produced a rise in rectal temperature, whereas temperature was not affected when micro‐injections of even larger doses were made into the posterior hypothalamus. The hyperthermia produced by injections of PGE1 into the cerebral ventricles is therefore attributed to an action of PGE1 on the anterior hypothalamus.2. During a pentobarbitone sodium anaesthesia the sensitivity of cats to the hyperthermic effect of PGE1 injected into the cerebral ventricles was found to be greatly reduced, particularly during the early stage of anaesthesia when body temperature was falling steeply.
Intracellular sodium activity and the sodium pump in snail neurones
Authors: Thomas R. C. 
Published: December 2014

1. Recessed‐tip Na+‐sensitive micro‐electrodes were used to measure [Na+]i continuously in snail neurones for experiments lasting up to several hours. The average resting [Na+]i in twenty‐two cells was 3·6 m
M.2. Inhibition of the Na pump by ouabain caused [Na+]i to increase at an average rate of 0·54 m‐mole/min. This corresponds to a passive influx of Na quantitatively similar to that observed in squid axons.3. Changing external K over the range 1‐8 m
M had little effect on [Na+]i, but K‐free or 0·25 m
M‐K Ringer caused a rise in [Na+]i.4. Increasing membrane potential by up to 90 mV caused an increased influx of Na, but did not inhibit the pump.5. Reducing external Na caused a decrease in [Na+]i but did not affect the pump rate at a given [Na+]i. The pump rate at low [Na+]i was proportional to [Na+]i minus a threshold value of about 1 m
M.6. The Na pump appeared still to be electrogenic at subnormal rates of activity.7. It is concluded that, given sufficient external K, the rate of the Na pump depends principally on [Na+]i. Changes in external Na or membrane potential appear to affect the pump only indirectly, by changing the Na influx and thus [Na+]i.
A reflex increase in heart rate from distension of the junction between the superior vena cava and the right atrium
Authors: Kappagoda C. T. , Linden R. J. , Snow H. M. 
Published: December 2014

1. Localized distension of the junction between the superior vena cava and the right atrium without obstructing venous return caused an increase in heart rate.2. This increase in heart rate was a reflex response; the afferent path was in the vagi and the efferent solely in the sympathetic nerves.3. The receptors most likely to be stimulated by the distension of the junction between the superior vena cava and the right atrium are the right atrial receptors located on the endocardial surface of the intrapericardial portion of the superior vena caval—right atrial junction.
Pure central responses from off‐centre cells and pure surround responses from on‐centre cells
Authors: Enroth-Cugell Christina , Pinto L. H. 
Published: December 2014

1. Pure responses generated by the centre response mechanism of off‐centre cells or the surround response mechanism of on‐centre cells were studied in the cat by recording from single optic tract fibres while applying slow square‐waves of light of varying duration but constant luminance.2. The response, whether due to a centre or a surround mechanism, consisted of a rapid decrease in firing frequency at onset of light, followed by a gradual recovery of firing rate while the light was on. The time course of the recovery was exponential. At ‘off’ there was a sudden increase in firing rate (off‐discharge) followed by an exponential, more gradual, decay of impulse frequency. Both the gradual recovery during illumination and the off‐discharge were absent for the shortest flashes.3. Perhaps the most significant result was that the behaviour exhibited by responses generated by one only of the response mechanisms, centre or surround, is predictable and much simpler than that exhibited by mixed responses; the magnitude of the off‐discharge increased, the latency decreased monotonically with increased flash duration and the magnitude of the off‐discharge was linearly related to the level of firing at the moment when the light went off.4. For two off‐centre cells gain was studied by recording the response to a brief test flash superimposed upon a slow gain changing square‐wave stimulus. Centre mechanism gain decreased promptly upon application of the gain changing light, stayed low while it was on, only to return promptly to its former value when the gain changing light went off.5. A simple model which qualitatively accounts for the results (excluding latency) was suggested. The onset of light initiates both an inhibitory and excitatory process whose sum constitutes the transient input to the cell. The excitatory process grows at a slower rate so that ‘excitation wins more and more as the light remains on’. Similarly after ‘off’ the excitatory process decays slower than the inhibitory one, thus leaving the cell with a transient excess of net‐excitation.
The effect of vasopressin (Pitressin) administration and dehydration on the concentration of solutes in renal fluids of rats with and without hereditary hypothalamic diabetes insipidus
Authors: Lee J. , Williams P. G. 
Published: December 2014

1. The method of sequential centrifugation has been used to obtain fluid samples from both the renal papilla and inner medulla of the rat.2. Experiments were carried out on Brattleboro rats with hereditary hypothalamic diabetes insipidus (DI; homozygous recessive), and on their (heterozygous) litter‐mates with normal quantities of neurohypophysial vasopressin. Initial classification of the animals by measurement of urine volume and osmolality was confirmed by post‐mortem bio‐assay of the pituitary glands, in thirty‐five out of forty‐seven animals.3. In rats with DI, urine osmolalities comparable to those of heterozygous rats were obtained after four daily injections of 1 u. Pitressin Tannate in Oil (PTO). Under these conditions, when dehydration was superimposed for 72 hr, urine osmolality did not increase markedly. In heterozygous rats dehydrated for the same period of time, urine osmolality increased by some twofold.4. In rats with DI, the administration of PTO induced a rise of both sodium and urea concentrations in renal fluids and in urine. Dehydration during PTO administration caused a further rise of urea concentrations only. Dehydration per se significantly raised urinary and renal fluid urea concentrations, but sodium concentrations did not rise.5. In heterozygous rats dehydration per se increased both urea and sodium concentrations in renal fluids and urine.6. The evidence is discussed that the action of vasopressin involves factors apart from increasing the permeability of the distal nephron to water and urea.
The relations between sarcomere length and characteristics of isometric twitch contractions of frog sartorius muscle
Authors: Close R. I. 
Published: December 2014

1. Relations between sarcomere length, tension and time course of isometric twitches at 20° C were determined for thirty‐two sartorius muscles from Rana temporaria.2. The maximum isometric twitch tension per unit cross‐sectional area of muscle ranged from 0·56 to 2·2 kg/cm2 at 20° C and initial sarcomere length about 2·1 μ. This variation was not correlated with the corresponding measure of tetanic tension.3. The maximum isometric twitch tension per unit cross‐sectional area of muscle at 2·1 μ sarcomere length was directly correlated with twitch contraction time and inversely correlated with the cross‐sectional area of the muscle.4. The isometric twitch contraction was potentiated with increase in initial sarcomere length from about 2·1 to about 2·8 μ at 20° C, and the degree of potentiation was inversely correlated with the maximum isometric twitch tension per unit cross‐sectional area of muscle at 2·1 μ sarcomere length.5. The sarcomere length: twitch tension relation is labile and may be altered by changes in temperature and the after‐effects of repetitive stimulation.6. Variation in twitch contractions at different sarcomere lengths are discussed in connexion with excitation—contraction coupling and the degree of activation of muscle fibres during twitch contractions at 20° C.
Electrical stimulation of the human eye in different adaptational states
Authors: Carpenter R. H. S. 
Published: December 2014

1. Experiments are described in which the phosphene produced by passing alternating current of frequency 100 Hz through the eye is matched with a patch of light having the same apparent size.2. Matches of this type have been made against different background light intensities, and at various times after a strong retinal bleach.3. To match the phosphene under particular conditions of this type, it is found that the patch must be set some 1·5 log td brighter than its own threshold under the same conditions. Exceptions to this rule occur with very bright backgrounds, or very soon after bleaching.4. The increment threshold for a small spot of light on the phosphene in the dark is some 0·5 log td higher than for the same spot on a patch of light matched in appearance to the phosphene under the same conditions.5. The process linking electrical stimulation of the eye to firing of fibres in the optic nerve is deduced to be substantially unaffected by the state of adaptation of the eye, save perhaps in the exceptional conditions described in (3).6. It is therefore argued that this phosphene is the result of stimulation both of the retinal visual pathways lying central to the variable‐gain element commonly accepted to explain the facts of dark adaptation, and also of the input to this element that is supposed to alter its gain.
The effect of real and simulated time‐zone shifts upon the circadian rhythms of body temperature, plasma 11‐hydroxycorticosteroids, and renal excretion in human subjects
Authors: Elliott Ann L. , Mills J. N. , Minors D. S. , Waterhouse J. M. 
Published: December 2014

1. Observations were made upon five subjects who flew through 4½–6 time zones, four of them returning later to their starting point, and upon twenty‐three subjects experiencing simulated 6 or 8 hr time zones shifts in either direction in an isolation unit.2. Measurements were made of plasma concentration of 11‐hydroxycorticosteroids, of body temperature, and of urinary excretion of sodium, potassium and chloride. Their rhythm was defined, where possible, by fitting a sine curve of period 24 hr to each separate 24‐hr stretch of data and computing the acrophase, or maximum predicted by the sine curve.3. The adaptation of the plasma steroid rhythm was assessed by the presence of a sharp fall in concentration after the sample collected around 08.00 hr. The time course of adaptation varied widely between individuals; it was usually largely complete by the fourth day after westward, and rather later after eastward, flights. After time shift the pattern often corresponded neither to an adapted nor to an unadapted one, and in a subject followed for many months after a real flight a normal amplitude only appeared 2–3 months after flight.4. Temperature rhythm adapted by a movement of the acrophase, without change in amplitude, although on some days no rhythm could be observed. This movement was always substantial even on the first day, and was usually nearly complete by the fifth.5. High nocturnal excretion of electrolyte was often seen in the early days after time shift, more notably after simulated westward flights. Adaptation of urinary electrolyte rhythms usually proceeded as with temperature, but the movement of the acrophase was slower, more variable between individuals, more erratic, and sometimes reversed after partial adaptation. On a few days there were two maxima corresponding to those expected on real and on experimental time.6. Sodium excretion was much less regular than that of potassium, but adapted more rapidly to time shift, so that the two often became completely dissociated. Chloride behaved much as sodium.7. The time course of adaptation of the plasma steroid and urinary potassium rhythms were sufficiently similar to suggest a causal connexion. The time course of adaptation of the temperature rhythm did not coincide with that of any other component considered here.
Control of ACh sensitivity by muscle activity in the rat
Authors: Lømo T. , Rosenthal Jean 
Published: December 2014

1. Rat soleus and extensor digitorum longus (EDL) muscles were examined following complete blockade of sciatic nerve impulses with anaesthetics or diphtheria toxin for periods up to 14 days.2. Muscles showed atrophy equivalent to that seen after similar periods of denervation.3. Nerve blockade appeared to have little or no effect on neuromuscular transmission when tested by stimulation beyond the block. Normal spontaneous miniature end‐plate potentials were present.4. Nerve impulse blockade caused the entire muscle membrane to become sensitive to iontophoretically applied acetylcholine.5. The increase in sensitivity in soleus could be prevented by chronic nerve stimulation distal to the region of block.6. Tenotomy, of 5‐12 days duration, which produced atrophy, had no effect on the sensitivity of soleus to acetylcholine.7. Chronic direct stimulation of denervated soleus or EDL muscles could prevent the usual denervation supersensitivity, or cause it to decline towards normal once it had appeared. However, the sensitivity of the end‐plate region remained normal.
The importance of timing on the respiratory effects of intermittent carotid body chemoreceptor stimulation
Authors: Eldridge Frederic L. 
Published: December 2014

1. The respiratory response, measured directly as tidal volume or indirectly by using integrated peak phrenic activity, to brief intermittent chemical stimulation or depression of the carotid body was determined in anaesthetized cats. Recordings of carotid sinus nerve impulses allowed precise timing of the stimulus.2. Stimulation of the carotid body had a rapid effect on air flow, tidal volume and phrenic discharge rate only if given during inspiration. Increases in tidal volume and peak phrenic discharge occurred only if stimulation was applied during the last half of inspiration. Stimulation during expiration had no effect on the form or magnitude of subsequent breaths.3. Depression of the carotid body by NH4OH led to decreased tidal volume and phrenic discharge if it occurred during inspiration but had no effect if it occurred during expiration.4. Stimuli in expiration led to a prolongation of expiration. Stimuli in late inspiration caused prolongation of both inspiration and expiration.5. All of the effects noted were eliminated by bilateral carotid body denervation.6. The findings are similar to those following electrical stimulation of the carotid sinus nerve and are attributable to modulation of carotid body signals by the central respiratory neurones.
Deiodination of thyroid hormones by the perfused rat liver
Authors: Hillier A. P. 
Published: December 2014

1. An investigation has been made into the deiodination of thyroid hormones by the perfused rat liver. The hormones were labelled with 125I in the phenolic ring and the rate of deiodination was estimated by measuring the release of radio‐iodide into the perfusate.2. At tracer concentrations, 0·98% of the liver thyroxine is deiodinated/5 min. The deiodination of tri‐iodothyronine is considerably faster, 3·3%/5 min.3. Deiodination is very sensitive to changes in temperature.4. The reaction shows saturation kinetics typical of many enzymes, the reciprocal of the rate of deiodination being proportional to the reciprocal of the hormone concentration in the tissue. The maximum rate of deiodination of each hormone is about 1·5 μg/min for a whole liver preparation weighing 16 g.5. Tri‐iodothyronine inhibits thyroxine deiodination and vice versa, suggesting that a single enzyme is responsible for both reactions.6. Propyl thiouracil (PTU) at high concentrations inhibits the deiodination of both hormones.7. An abnormally high rate of deiodination is associated with the actual injection of hormone into the preparation. This suggests that only the free (unbound) hormone in the tissue is directly available to the deiodinating enzyme.8. About half of the whole body deiodination of thyroxine is relatively insensitive to PTU. It is suggested that most of this type of deiodination is performed in the liver and that the process is one of inactivation.
The effects of calcium on branchial sodium fluxes in the sea‐water adapted eel, Anguilla anguilla, L
Authors: Bornancin M. , Cuthbert A. W. , Maetz J. 
Published: December 2014

1. The sodium influx through the gills of eels placed in calcium‐free sea water for 15 hr was double that of controls. The effect was reversed in 1 hr by addition of calcium.2. The total sodium outflux through the gills of fish placed in calcium‐free sea water for 15 hr was double that of controls. The effect was only partially reversed in 15 hr by addition of calcium.3. The passive outflux component of the total outflux was increased fourfold when calcium was removed and was restored to normal in 15 hr by addition of calcium. The active (exchange) outflux component of the total outflux was halved by calcium removal and increased above normal following calcium addition.4. The inability of calcium to restore the total outflux to normal within 15 hr in calcium‐depleted fish, together with the raised plasma sodium concentration at this time, suggests that the raised outflux is caused by homoeostatic mechanisms, rather than permeability changes in the gill epithelium.
Diurnal variations of plasma calcium and calcitonin function in the rat
Authors: Milhaud Gérard , Perault-Staub Anne-Marie , Staub Jean-François 
Published: December 2014

1. These experiments were designed to investigate the normal physiological role of calcitonin in the control of blood calcium.2. The rat can be adapted to an artificial cycle of alternating 12‐hr periods of light and darkness. Since rats eat only in the dark, calcium absorption is confined to the dark period.3. In rats thus adapted, the plasma calcium and phosphate levels show cyclic variation related, among other factors, to the calcium intake.4. The variation observed is modified by the removal of the thyroid gland. This cannot be attributed to deprivation of thyroxine and triiodothyronine because these experiments were carried out within 2 days of thyroidectomy.5. Thyroidectomy raises the plasma calcium and phosphate levels, but only if performed during the dark‐fed period. This suggests the existence of a diurnal rhythm in endogenous calcitonin function.6. The magnitude of the falls in plasma calcium and phosphate, produced by exogenous calcitonin, also varies with the time of day. This shows that the rat's responsiveness to calcitonin also varies diurnally.
Constrictor and compliance responses of some arteries to nerve or drug stimulation
Authors: Gillespie J. S. , Rae R. M. 
Published: December 2014

1. The magnitude of the maximum constrictor response to nerve stimulation was measured in the saphenous, ear, inferior and superior mesenteric, renal and carotid arteries in the rabbit and corresponding arteries, except the ear and carotid, in the guinea‐pig. The responses varied from an average rise of 350 mm Hg in the rabbit saphenous to almost no response in the rabbit carotid. The guinea‐pig arteries gave consistently smaller responses than the rabbit. The response magnitude was unrelated to wall thickness or the presence of an active uptake mechanism for noradrenaline. The response did correlate with the density of adrenergic innervation, with the wall thickness to lumen ratio and with the function of the artery and the amount of connective tissue in its wall.2. The magnitude of the maximum constrictor response to noradrenaline and six other agonist drugs, acetylcholine, histamine, 5‐HT, KCl, vasopressin and angiotensin II, was compared. In all arteries noradrenaline was the most powerful agonist. The maximum responses to nerve stimulation and to noradrenaline were compared. In the rabbit saphenous and ear arteries this ratio was almost 1, but in arteries such as the rabbit renal it fell below 0·5.3. Artery wall stiffness was measured from the pressure/volume relationship during distension of a closed length of artery. In a relaxed artery two components only were present, an early easily distended phase and a late relatively undistensible phase. Noradrenaline caused a third, early, very stiff phase to appear in the pressure/volume curves. This is probably due to contracted muscle. The increase in stiffness varied from 617% in the rabbit saphenous to 152% in the rabbit carotid. In conducting arteries such as the carotid the change in stiffness was a more sensitive index of noradrenaline action than vaso‐constriction.4. During the measurement of wall stiffness stress relaxation was not noticeable in relaxed arteries but was prominent in arteries contracted by noradrenaline. Stress relaxation involved both the changes in wall stiffness and the ability to constrict and was reversible even in the continuing presence of agonist drugs.5. Nerve stimulation, even in arteries where its vasoconstrictor effects were equal to those of noradrenaline, gave only slight increases in artery wall stiffness, suggesting that even in these densely innervated arteries only a small fraction of the muscle is activated by nerve stimulation.
Effects of exteriorization of the ureters on the water metabolism of the domestic fowl
Authors: Dicker S. E. , Haslam J. 
Published: December 2014

1. Six domestic fowls were operated for exteriorization of the ureters.2. Three weeks after the operation their food and water intake was compared with that of six unoperated control fowls of similar weight.3. Water intake was calculated from the amount of water drunk, the metabolic water and the water content of the food eaten; while water loss was estimated from the water content of urine and faeces excreted and from evaporation.4. Fowls with exteriorized ureters drank more than the control birds. The excess of water drunk by these birds approximated the amount of water lost in the urine.