bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation of food intake in lambs with adipocyte glucose metabolism and NEFA release
Authors: Mears G. J. , Mendel V. E. 
Published: December 2014

1. Experiments were conducted with lambs to determine the correlation between food intake, rate of glucose incorporation into CO2 and lipids, and rate of lipid mobilization by their isolated omental adipocytes.2. During the interval between weaning and slaughter average daily dry matter (ADDM) intakes of the individual lambs were significantly correlated with average daily gains; however, the ratio of ADDM intake to body wt.¾ was similar in all individuals.3. The average size of adipocytes for each lamb, as determined by lipid: protein ratios, was not significantly correlated with food intake.4. Oxidation of glucose to CO2 and the total measured glucose incorporation by the adipocytes were significantly and negatively correlated with lamb ADDM intakes at low levels of glucose (0·1 mg/ml.), whereas rates of lipogenesis from glucose were similar for all intake levels.5. Insulin‐induced increases in glucose utilization were positively and significantly correlated with ADDM intakes to the extent that insulin had over twice the effect on the adipocytes from high‐intake lambs as it had on those from low‐intake lambs. The minimum effective dose of insulin necessary to significantly increase glucose utilization by the adipocytes was also positively and significantly correlated with the ADDM intakes of the lambs.6. Basal NEFA release rates were higher for adipocytes from low‐intake lambs. Epinephrine significantly increased NEFA release rates, independent of lamb intakes.7. A larger number of adipocytes in the high‐intake lambs means that they would have a greater total potential to lower blood glucose, particularly when they are under the effects of normal circulating levels of insulin. The amount of glucose removed from the glucose pool could be the feed‐back signal which results in a high long‐term food intake.
Thyroid hormone responses to prolonged cold exposure in man
Authors: Eastman C. J. , Ekins R. P. , Leith I. M. , Williams E. S. 
Published: December 2014

1. Four men, of ages varying from 23 to 28 years, living at Halley Bay, Antarctica (75° 31′ S, 26° 39′ W), were exposed to a mean air temperature of 6·6° C.2. The concentration of serum triiodothyronine (T3) rose significantly by the second day, remained raised, and returned to pre‐exposure levels within 2 days of return to a normal environment.3. The concentration of serum thyroxine (T4) rose more slowly than did the T3, reaching a maximum in 3‐4 days and also returning to normal within 2 days of return to a normal environment.4. There was a wide individual variation in the change of concentration of serum cortisol.
The influence of bulbospinal monoaminergic pathways on sympathetic nerve activity
Authors: Coote J. H. , Macleod Valerie H. 
Published: December 2014

1. Spontaneous and reflex activity was recorded from renal and splanchnic nerves and thoracic white rami during discrete electrical stimulation within the medulla oblongata of anaesthetized cats.2. Inhibition or excitation of spontaneous sympathetic nerve activity was obtained from several medullary regions.3. The long‐circuited reflex elicited in renal nerves and the spinally mediated reflex discharge produced in white rami by single shock stimulation of intercostal nerves were inhibited by stimulation within the sympatho‐inhibitory areas of the medulla.4. Activation of spontaneous sympathetic nerve activity or inhibition of spontaneous and reflex sympathetic nerve activity was obtained during electrical stimulation within the lateral funiculi of the cervical spinal cord in unanaesthetized decerebrate cats, spinalized at C1.5. There was a correlation between the position of some sympatho‐inhibitory regions of the medulla and spinal cord and the position of the cell bodies and axons of descending monoamine‐containing neurones.6. Intravenous administration of the precursor of noradrenaline,
L‐DOPA, to unanaesthetized decerebrate cats, spinalized at C1, was followed by a depression of spontaneous activity in renal nerves and reflex responses elicited in renal nerves and white rami.7. Similarly the precursor of 5‐hydroxytryptamine, 5‐HTP, caused a depression of reflex activity elicited in renal nerves and white rami, but had no effect on spontaneous renal nerve activity.8. It is suggested that there exist both noradrenergic and tryptaminergic pathways which descend to the spinal cord from the medulla and which are inhibitory to sympathetic outflow.
Fall in blood pressure produced from discrete regions of the ventral surface of the medulla by glycine and lesions
Authors: Guertzenstein P. G. , Silver Ann 
Published: December 2014

1. In cats anaesthetized with pentobarbitone sodium, atropinized by
i.v. atropine methyl nitrate and artificially ventilated, experiments were carried out (a) to localize the site where glycine acts on the ventral surface of the medulla when, on topical application through paired Perspex rings caudal to the trapezoid bodies, it produces a fall in arterial blood pressure, (b) to compare the effects of uni‐ and bilateral application, and (c) to study the blood pressure effects produced by electrolytic lesions of the glycine‐sensitive areas.2. Blood pressure fell only a little on unilateral application of glycine through one of the Perspex rings, but a pronounced fall occurred on its bilateral application. The fall was too large to be explained by two minimal responses added together. Thus the application of glycine to one side potentiated the depressor effect of glycine applied to the other side.3. By moving the paired Perspex rings rostrally or caudally to different positions on the medulla and determining for each position the effectiveness of glycine, the glycine‐sensitive areas were found to be restricted to a 1·5 mm wide strip situated 1–2·5 mm caudal to the trapezoid bodies. By making electrolytic lesions within the limits of this strip the glycine‐sensitive areas were found to be not wider than 1·5 mm in the mediolateral direction and to be situated about 4 mm lateral to the mid line. Histologically, such lesions involved the cells of the parvicellular part of the lateral reticular nucleus.4. Placing an electrode, with a diameter of 1 mm, under light pressure on the glycine‐sensitive area produced a short‐lasting steep rise in blood pressure. The same effect was produced when a current was passed through the electrode to destroy the underlying tissue, but after its destruction the passage of current no longer produced the pressor effect.5. Once the glycine‐sensitive area of one side was destroyed, glycine applied to the destroyed area through one of the Perspex rings no longer produced its small depressor effect, but when applied to the intact area of the other side, a pronounced fall in blood pressure occurred. Thus unilateral destruction had the same effect as unilateral glycine application. It potentiated the depressor effect of glycine applied to the other side.6. Following unilateral destruction of the glycine‐sensitive area there was only a small fall in blood pressure; following its bilateral destruction blood pressure fell to a low level.7. It is concluded that the cells in the small circumscribed glycine‐sensitive areas on the ventral surface of the medulla may play a key role in the maintenance of arterial blood pressure and that the cells of one side are sufficient for this function.
Effect of ouabain on renin secretion in anaesthetized dogs
Authors: Churchill Paul C. , McDonald Franklin D. 
Published: December 2014

1. Pentobarbitone anaesthetized dogs were used to study the effects on renin secretion of ureteral occlusion and partial aortic clamping before and after intrarenal arterial administration of ouabain.2. Arterial plasma renin activity (A renin) and renal venous minus arterial plasma renin activity (RV‐A renin) were both increased by either ureteral occlusion during mannitol diuresis or partial aortic clamping to reduce renal perfusion pressure. Intrarenal arterial ouabain administration blunted or abolished the effects of these manoeuvres on A and RV‐A renins.3. The observations are not consistent with the hypothesis that renin secretion is uniquely controlled by afferent arteriolar transmural pressure. Both ureteral occlusion and aortic clamping reduce this pressure and increase renin secretion, yet evidence presented herein suggests that ouabain, which also decreases this pressure, decreases renin secretion.4. The observations are consistent with the hypothesis that renin secretion is controlled by tubular fluid flow and/or composition in the region of macula densa cells. Possibly changes in flow and/or composition are detected as changes in macula densa intracellular sodium concentration.
Changes in time scale and sensitivity in turtle photoreceptors
Authors: Baylor D. A. , Hodgkin A. L. 
Published: December 2014

1. In turtle cones the steady‐state relation between the internal potential and log light intensity was much flatter in the steady state than it was at 30 msec after the beginning of a step of light; this is attributed to a desensitization which develops with a delay of 50–100 msec.2. When a weak flash was superposed on a steady background light which hyperpolarized the cone by 3‐6 mV the amplitude of the linear response to a flash was reduced to 1/e and the time to maximum was shortened from about 110 to 70 msec; the response also became diphasic. With stronger background lights the flash sensitivity continued to fall, but the time to maximum did not become shorter than 40–50 msec and lengthened again with very strong lights.3. In cones the flash sensitivity SF was reduced to half its dark value SFD by a light intensity of 1/SFDζ where ζ is about 20 sec/V.4. At low levels of background light, about two‐thirds of the change in sensitivity was time‐dependent and one‐third was attributable to the ‘instantaneous non‐linearity’ described in the previous paper.5. The reduction in time to peak and the decrease in sensitivity produced by a background light which hyperpolarized by about 3 mV was little affected by changing the diameter of the area illuminated from 12 to 800 μm.6. An experiment with a rod showed that a very weak light which hyperpolarized by only 0·5 mV decreased the linear response to 1/e and shortened the time to maximum from 300 to 180 msec.7. With weak or moderate flashes the time‐dependent desensitization lagged behind the potential by 50–100 msec.8. The desensitization and shortening of time scale which persisted after a flash or step were associated with an after‐hyperpolarization. The relaxation of potential, sensitivity and time scale became slower as the preceding illumination was increased from 103 to 1010 photons μm−2; the increase seemed to occur in steps involving components which relaxed with time constants of the order of 0·1, 1, 10 and 100 sec. A rebound phenomenon was observed after steps longer than 30 sec and with equivalent intensities greater than 105 photons μm−2 sec−1.9. Several of the observations are explained by a hypothesis in which the central assumption is that the particles which block the ionic channels are degraded or removed by an autocatalytic reaction.
Extreme vestibulo‐ocular adaptation induced by prolonged optical reversal of vision
Authors: Gonshor A. , Jones G. Melvill 
Published: December 2014

1. These experiments investigated plastic changes in the vestibulo‐ocular reflex (VOR) of human subjects consequent to long‐term optical reversal of vision during free head movement. Horizontal vision‐reversal was produced by head‐mounted dove prisms. Four normal adults were continuously exposed to these conditions during 2, 6, 7 and 27 days respectively.2. A sinusoidal rotational stimulus, previously shown to be nonhabituating (1/6 Hz; 60°/sec amplitude), was used to test the VOR in the dark at frequent intervals both during the period of vision‐reversal and an equal period after return to normal vision. D.c. electro‐oculography (EOG) was used to record eye movement, taking care to avoid changes of EOG gain due to light/dark adaptation of the retina.3. All subjects showed substantial reduction of VOR gain (eye velocity/head velocity) during the first 2 days of vision‐reversal. The 6‐, 7‐ and 27‐day subjects showed further reduction of gain which reached a low plateau at about 25% the normal value by the end of one week. At this time the attenuation of some EOG records was so marked as to defy extraction of a meaningful sinusoidal signal.4. After removal of the prisms VOR gain recovered along a time course which approximated that of the original adaptive attenuation.5. In the 27‐day experiment large changes of phase developed in the VOR during the second week of vision‐reversal. These changes generally progressed in a lagging sense, to reach 130° phase lag relative to normal by the beginning of the third week. Accompanying this was a considerable restoration of gain from 25 to 50% the normal value. These adapted conditions, which approximate functional reversal of the reflex, were then maintained steady, even overnight, until return to normal vision on the 28th day.6. Thereafter, whereas VOR phase returned to near‐normal in 2 hr, restoration of gain occupied a further 2‐3 weeks.7. There was a highly systematic relation between instantaneous gain and phase, even during periods of widely fluctuating change associated with transition from one steady state to another. During such transition there was a tendency for directional preponderance to occur in the VOR.8. All the observed changes were highly specific to the plane of vision‐reversal, no VOR changes being observed in the sagittal plane.9. VOR changes were adaptive, in the sense that they were always goal‐directed towards the requirements of retinal image stabilization during head movement. They were plastic to the extent that there was extensive and retained remodelling of the reflex towards this goal.10. It is inferred that all the observed changes in gain and phase are compatible with a simple neural network employing known vestibulo‐ocular projections via brainstem and cerebellar pathways, providing that the reversed visual tracking task can produce plastic modulation of efficacy in the cerebellar pathway and that this pathway exhibits a dynamic characteristic producing moderate phase lead in a sinusoidal signal at 1/6 Hz.
Nervous outflow from skeletal muscle following chemical noxious stimulation
Authors: Mense S. 
Published: December 2014

1. In order to determine the nervous outflow from skeletal muscle during chemically induced muscle pain, the impulse activity of various types of muscle afferents in response to close intra‐arterial injections of pain‐producing substances (bradykinin, 5‐hydroxytryptamine, histamine and potassium) was studied in anaesthetized cats using a single fibre recording technique.2. By administration of algesic agents in doses which produce pain in man and pain reactions in animals, about half of the group IV and two thirds of the group III muscle afferents could be activated. In contrast, group II and group I afferent units were usually not excited by chemical noxious stimulation. If effects at all occurred in the thick myelinated afferents, they consisted of a depression of the fibre activity rather than of an activation.3. The qualitative features of the discharges of group III muscle afferents induced by chemical stimulation resembled those of the group IV units very closely. The group III units differed from the group IV afferents in that their responses to a given dose of bradykinin were of greater magnitude.4. It is concluded that the chemically induced muscle pain is probably mediated by certain portions of the group IV and group III afferents, whereas the reactions of group II and group I units to algesic agents are such that a contribution to muscular chemo‐nociception seems improbable.
Calcium currents and conductances in the muscle membrane of the crayfish
Authors: Henček M. , Zachar J. 
Published: December 2014

1. Membrane currents in calcium type muscle membrane of the cray‐fish Astacus fluviatilis were analysed by a method in which a membrane microarea was isolated by circulating sucrose rings contacting the fibre perpendicular to the fibre surface.2. The early calcium inward currents were separated from the total membrane currents by subtraction of the early and delayed potassium currents from the total membrane current.3. The isolated calcium currents show a time course characteristic for a transient change of calcium conductance. The presence of inactivation was further checked by the time course of the tail currents at the end of voltage clamp pulses of variable duration.4. The reversal potential of the early calcium currents determined from the current—voltage relations was +85 ± 4·2 mV. The calcium potentials were used to express the calcium currents in the form of chord conductances.5. Calcium conductances (gCa) as functions of time and voltage were found to be described quantitatively on the assumption that gCa is determined by two variables (m and h), according to the equation gCa = m6hḡCa, where ḡCa is a constant and m and h obey first order differential equations of the Hodgkin—Huxley type.6. The activation parameters of the gCa were determined by fitting the solutions of the above equations to the experimental values of the gCa. This method was also used to check the inactivation parameters.7. The inactivation parameters of the gCa were obtained from the inactivation curves, which were determined for several membrane potentials by variation of the duration of the conditioning step.8. The average calcium conductance constants were tabulated and compared with sodium conductance constants in excitable membranes.
The force‐velocity relationship in vertebrate muscle fibres at varied tonicity of the extracellular medium
Authors: Edman K. A. P. , Hwang J. C. 
Published: December 2014

1. The relationship between active force and velocity of shortening was studied during tetanic contraction of isolated semitendinosus muscle fibres of the frog (0·5‐2·0° C). Measurements were carried out with the fibre immersed in isotonic (1·00R) Ringer solution and in solutions that were made hypotonic by reduction of NaCl (osmolality 0·62 and 0·81 of normal Ringer) and hypertonic by addition of sucrose (osmolality 1·22 and 1·44 of normal Ringer).2. The force—velocity relation was hyperbolic at loads lower than 80% of measured isometric force (P0) but exhibited a reversed curvature between 0·8P0 and P0. The maximum velocity of shortening was determined in two different ways: (i) by extrapolation to zero load from force—velocity data truncated at 0·8P0 (computer fitting of hyperbola, leastsquares method) and (ii) by recording the time required to take up the slack of the fibre after a quick release during tetanus.3. Isometric force and maximum speed of shortening both changed inversely with the tonicity of the extracellular medium. Immersion of the fibre in 0·81R hypotonic solution caused active tension and shortening velocity to increase by 10 ± 1% (mean ±
S.E. of mean, n = 14) and 12 ± 1%, respectively. Conversely, force and shortening velocity decreased by 12 ± 1% (n = 13) and 22 ± 2% when normal Ringer was replaced by 1·22R hypertonic solution. These changes doubled when the tonicity was altered from normal Ringer to 0·62R and 1·44R, respectively.4. Changes in fibre cross‐sectional area equivalent to those obtained in the 0·81R and 1·22R solutions (+11% and ‐13%, respectively) were produced by varying the sarcomere length within the range 2·0‐2·5 μm in the normal Ringer solution. Maximum velocity of shortening remained very nearly constant under these conditions, indicating that the shortening velocity, like the isometric force, is not critically dependent on changes in myofilament lattice width over the range considered.5. The results support the view that both shortening velocity and active force are modulated by changes of the intracellular ionic strength above and below the level that normally exists in the intact muscle fibre.
Action of oleic acid on the exocrine pancreatic secretion of the conscious rat: evidence for an anticholecystokinin‐pancreozymin factor
Authors: Laugier R. , Sarles H. 
Published: December 2014

The effects on exocrine pancreatic secretion of an intraduodenal infusion of oleic acid (2 ml in 60 min) has been assessed in conscious rats provided with a new type of duodenal cannula permitting the normal flow of pancreatic juice, but not of bile, between experiments.1. Intraduodenal oleic acid infusion induces an increased secretion of water and bicarbonate which is still significantly above basal values 90 min after the end of infusion. Protein output increased during the infusion, but protein concentration and output significantly decreased under basal levels 120 min and 150 min after infusion (respectively ‐63 and ‐57% of basal values at 150 min).2. No inhibition was found when oleic acid was introduced into the caecum or into the first 20 cm of ileum isolated from the rest of small intestine. On the contrary, inhibition of protein secretion was induced immediately by intra‐ileal oleic acid infusion.3. Inhibition of protein secretion secondary to intra‐ileal oleic acid infusion was transmitted from a donor rat to a receiver rat by means of a cross‐circulation.4. It is concluded that oleic acid induces an immediate and long lasting increase in water and bicarbonate secretion. During the infusion of oleic acid, protein output is increased, followed by an inhibition. This delayed inhibition stems from the second part of the small intestine and was transferred from one rat to another by cross‐circulation: it is speculated that oleic acid releases in the conscious rat (from the distal part of the small intestine) a hormonal factor inhibiting pancreatic secretion.
The relation between tidal volume and inspiratory and expiratory times during steady‐state carbon dioxide inhalation in man
Authors: Gardner W. N. 
Published: December 2014

1. Ambiguities and discrepancies in the published descriptions of the patterns of breathing in man have been re‐investigated.Steady‐state hyperpnoea during rest was induced in normal subjects of both sexes by means of CO2 inhalation, usually in high O2, but sometimes in low (PA, O2 ∼ 200 and 55 torr respectively).2. The relations between mean tidal volume V̄T and mean times for inspiration T̄I and expiration T̄E were satisfactorily divided into lower and upper parts (ranges 1 and 2) in nineteen out of thirty‐three experiments using an objective least‐squares method, and polynomials were fitted separately to each of the following pairs of variables V̄T,lower, T̄I; V̄T,lower, T̄E; V̄T,upper, T̄I; V̄T,upper, T̄E.3. The breakpoints occurred when V̄T was about one third of vital capacity, but there was much variation between subjects.4. In range 2, V̄T was inversely related to both T̄I and T̄E and there appeared to be linkage between T̄I and T̄E, all as described by Clark & Euler (1972). The relation suggested by Hey, Lloyd, Cunningham, Jukes & Bolton (1966) over range 2 was not confirmed.5. The main part of the relation described by Hey et al. (1966) is concerned with range 1. Here the relation between V̄T and T̄I was variable; slight, but significant negative correlation predominated. V̄T was, on the other hand, strongly and inversely related to T̄E, and plots of (T̄E — T̄I) against V̄T over both ranges showed even less scatter. Hence (a) T̄E is probably related to V̄T through two mechanisms, one involving a link with TI and another prominent one being quite independent of TI, (b) most changes of respiratory frequency in normal man are brought about by change of TE rather than of TI, and (c) there is no region of constant frequency as implied by Clark & Euler (1972).