bluuebunny/crossref_metadata_2025_split huggingface dataset:
Disturbances of rod threshold forced by briefly exposed luminous lines, edges, disks and annuli
Authors: Hallett P. E. 
Published: December 2014

1. When the dark‐adapted eye is exposed to a brief duration (2 msec) luminous line the resulting threshold disturbance is much sharper (decay constant of ca. 10 min arc) than would be expected in a system which is known to integrate the effects of light quanta over a distance of 1 deg or so.2. When the forcing input is a pair of brief duration parallel luminous lines the threshold disturbance falls off sharply at the outsides of the pattern but on the inside a considerable spread of threshold‐raising effects may occur unless the lines are sufficiently far apart.3. The threshold disturbance due to a briefly exposed edge shows an overshoot reminiscent of ‘lateral inhibition’.4. If the threshold is measured at the centre of a black disk presented in a briefly lit surround then (a) the dependence of threshold on time interval between test and surround suggests that the threshold elevation is due to a non‐optical effect which is not ‘metacontrast’; (b) the dependence of threshold on black disk diameter is consistent with the notion that the spatial threshold disturbance is progressively sharpened as the separation of luminous edges increases.5. If the threshold is measured at the centre of briefly exposed luminous disks of various diameters one obtains the same evidence for an ‘antagonistic centre‐surround’ system as that produced by other workers (e.g. Westheimer, 1965) for the steadily light‐adapted eye.6. The previous paper (Hallett, 1971) showed that brief illumination of the otherwise dark‐adapted eye can rapidly and substantially change the extent of spatial integration. The present paper shows that brief illumination leads to substantial ‘inhibitory’ effects.7. Earlier approaches are reviewed: (a) the linear system signal/noise theory of the time course of threshold disturbances (Hallett, 1969b) is illustrated by the case of a small subtense flash superimposed on a large oscillatory background; (b) the spatial weighting functions of some other authors are given.8. A possible non‐linear model is briefly described: the line weighting function for the receptive field centre is taken to be a single Gaussian, as is customary, but the line weighting function for the inhibitory surround is bimodal.
Effects of CO2 on transmembrane potentials of rat liver and muscle in vivo*
Authors: Williams J. A. , Withrow C. D. , Woodbury D. M. 
Published: December 2014

1. The effects of increasing the inspired CO2 concentration on the transmembrane resting potential (RP), intracellular electrolytes, and cell pH of rat liver and muscle were studied.2. Elevation of CO2 produced a rapid reversible fall in hepatic RP. This effect is mediated by a decrease in plasma pH and is in part due to hypoxia.3. The decrease in hepatic RP could not be accounted for by shifts in electrolytes, and an effect on membrane permeability is suggested.4. The hepatic RP was also found to be decreased by hypoxia and increased by hyperoxia.5. Muscle RP showed no immediate change in response to CO2 but after 60 min there was significant depolarization. This effect could be accounted for on the basis of electrolyte shifts between cells and plasma, by use of the Goldman equation.6. Cell pH data showed that liver is buffered approximately threefold more than skeletal muscle.7. While intracellular pH fell in response to CO2 the H+ gradient remained constant in muscle and increased in liver.
The influence of deep body temperatures and skin temperatures on peripheral blood flow in the pig
Authors: Ingram D. L. , Legge K. F. 
Published: December 2014

1. The rate of blood flow through the tail of the pig has been measured by means of venous occlusion plethysmography using a mercury in rubber strain gauge. Conscious animals were used in all experiments because previous work had demonstrated that anaesthetics interfere with the animal's ability to vasoconstrict.2. Graded changes in the temperature of the hypothalamus were imposed by means of an implanted thermode. It was found that the change in blood flow depended on the extent of the change in hypothalamic temperature and on the ambient temperature. Below 20° C ambient temperature, heating the hypothalamus did not cause vasodilatation and at 30° C ambient temperature, cooling the hypothalamus caused only slight vasoconstriction, but at 25° C ambient temperature, changes in hypothalamic temperature caused changes in blood flow from full vasoconstriction to full vasodilatation.3. The skin temperature on the trunk was changed by means of water circulated through tubes sewn into a coat worn by the pig. Blood flow in the tail, which was outside the coat, depended on the skin temperature of the trunk, the ambient temperature, and the temperature of the hypothalamus, all of which were varied separately.4. A thermode was implanted in the epidural space in the cervical region of the spinal cord. The change in blood flow in the tail which accompanied a change in thermode temperature was found to depend on the temperature of the thermode and the ambient temperature. Cooling the spine while the hypothalamus was being heated to 43° C resulted in a decrease in blood flow, but when the spine was heated while the hypothalamus was being cooled the increase in blood flow was only slight.5. Local stimulus to the tail in the form of infra‐red heat, or increased air movement was followed by changes in blood flow even when deep body temperature remained stable.
Formation of saliva and potassium transport in the perfused cat submandibular gland
Authors: Petersen O. H. 
Published: December 2014

1. In the cat submandibular gland perfused with modified Locke solutions, salivary secretion during acetylcholine (ACh) infusion and K uptake from the perfusion fluid after the ACh‐induced K loss were measured.2. Strophanthin G (10−5
M) abolished K uptake, whereas salivary secretion was unaffected.3. Ethacrynic acid (10−4‐2 × 10−4
M) hardly affected K uptake whereas salivary secretion was severely inhibited.4. During perfusion with Ca‐free solution K uptake was unaffected, whereas salivary secretion was severely reduced.5. The presence or absence of CO2/HCO3 in the perfusion fluid was of no importance for the secretory process and the K uptake. Acetazolamide (2 × 10−4‐10−3
M) did not inhibit these transport processes.6. It is suggested that two kinds of Na transport occur in the acinar cells of the salivary glands: a Na extrusion coupled with K uptake, responsible for the maintenance of the concentration gradients across the cell membrane; and a Na transport coupled with Cl transport into the acinar lumen, responsible for the formation of the primary secretion.
Effects of nerve cross‐union on rat intracellular potassium in fast‐twitch and slow‐twitch rat muscles
Authors: Hoh J. F. Y. , Salafsky B. 
Published: December 2014

1. Electrolytes of normal, self‐innervated and cross‐innervated extensor digitorum longus and soleus muscles of rats have been determined.2. [K]i was 173 m‐equiv/l. for both normal and self‐innervated extensor digitorum longus. In cross‐innervated extensor digitorum longus it was reduced to 159 m‐equiv/l.3. For normal and self‐innervated soleus, [K]i was 150 m‐equiv/l. and 154 m‐equiv/l. respectively. In cross‐innervated soleus it was increased to 182 m‐equiv/l.4. The content and distribution of most other electrolytes of cross‐innervated soleus, as well as its weight, were not significantly different from those of controls. On the other hand, cross‐innervated extensor digitorum longus weighed about half as much as controls and contained markedly elevated Na+, Cl− and extrafibre water and reduced non‐collagenous protein and intrafibre water.5. It is concluded that [K]i of fast‐twitch and slow‐twitch muscle fibres are under neural regulation. Possible mechanisms for this regulation are discussed.
The heat of shortening during the plateau of tetanic contraction and at the end of relaxation
Authors: Aubert X. , Lebacq J. 
Published: December 2014

1. The net thermal effect of shortening on the heat production of the sartorius muscle of Rana temporaria has been studied at 0° C in tetanic contractions of either 1·2 or 2·0 sec analysed up to the end of relaxation.2. Three types of contractions have been compared: isometric at the standard length (lo); isometric at a shorter length (lo minus 4·27 mm); and rapid shortening at constant velocity between those two lengths during the plateau of tetanic activity, the work being collected by an ergometer of the Levin—Wyman type. After the end of the shortening, stimulation was continued long enough to allow a complete recovery of tension before relaxation started.3. In those conditions, shortening heat appears clearly by comparison with the isometric contractions, and most of its effect persists up to the end of relaxation. However, a reduction of the net thermal effect, of the order of 15–25%, is observed during relaxation.4. The net supplement of heat is the same whether the shortening occurs in the beginning (0·4 sec) or towards the end (1·2 sec) of the contraction period; the reduction of the effect during relaxation is more important in the pelvic part than in the tibial part of the muscle.5. This small reduction of the thermal effect of the shortening is fully accounted for by the fact that the tension redeveloped after the end of the movement remains always below the tension developed in a tetanus at the same final length, but isometric from the start.6. As the greater part of the net thermal effect of the shortening persists at the end of relaxation, shortening heat cannot be part of a cyclic process reversed during relaxation; it must derive from some chemical source of energy.
Catecholamines and 5‐hydroxytryptamine in nervous tissue of cephalopods
Authors: Juorio A. V. 
Published: December 2014

1. Catecholamines and 5‐hydroxytryptamine were measured fluorimetrically in nervous tissue of cephalopod molluscs.2. The only catecholamines found present in nervous tissue of Eledone, Octopus and Sepia were dopamine and noradrenaline. The highest concentrations were found in the optic lobes and in the superior buccal lobe. The concentrations of dopamine and noradrenaline were smaller in other regions of the nervous tissue taken.3. 5‐Hydroxytryptamine was also found in most of the regions investigated. The highest concentration was found in the inferior buccal ganglia and in the optic lobes.4. The administration of reserpine produced a marked decrease in the concentration of catecholamines and 5‐hydroxytryptamine in octopod nervous tissue.5. These findings suggest that dopamine, noradrenaline and 5‐hydroxytryptamine may function as neurotransmitters in cephalopod molluscs.
Effects of abrupt load alterations on force—velocity—length and time relations during isotonic contractions of heart muscle: load clamping
Authors: Brutsaert D. L. , Claes V. A. , Sonnenblick E. H. 
Published: December 2014

1. Abrupt alterations in load (load‐clamping) have been imposed on cat papillary muscles during the course of isotonic shortening, between the onset of shortening and peak shortening.2. For any given total load, whether imposed during the course of shortening or before stimulation, the velocity of shortening is determined solely by the instantaneous length, and not by the sequence of length and tension changes through which it arrived at that length.3. This unique force—velocity—length relation is independent of time from just after the onset of shortening until just prior to peak shortening.4. These results suggest that a steady state exists for the maximum intensity of active state in heart muscle over a major portion of the time during which isometric force is rising, and that heart muscle always senses total load while shortening.
The effect of temperature change upon transmitter release, facilitation and post‐tetanic potentiation
Authors: Hubbard J. I. , Jones S. F. , Landau E. M. 
Published: December 2014

1. End‐plate potentials (e.p.p.s) and miniature end‐plate potentials (m.e.p.p.s) were intracellularly recorded from rat diaphragm phrenic nerve preparations in vitro at temperatures between 7° and 40°C.2. The quantal content of e.p.p.s and the frequency of m.e.p.p.s showed broadly similar relationships with temperature, with maxima about 20° and above 39°C.3. Analysis of the change in e.p.p. quantal content showed that the maximum about 20°C was accompanied by a similar maximum of p, the probability of release of quanta. The maximum above 39°C was associated with a rise in n, a presynaptic store of material needed for release.4. The rate at which transmitter could be mobilized was linear in an Arrhenius plot with an apparent activation energy of 25 kcal deg−1.5. Facilitation and post‐tetanic potentiation (PTP) were shown to be entirely attributable to changes in p.6. It is suggested that facilitation and PTP have a common basis and that the (temperature‐dependent) rate of Ca removal from intracellular sites at which it exerts its action is as important a determinant of the magnitude of quantal release as is the amount of Ca combining with these sites.
Catecholamine secretion by the adrenal medulla of the foetal and new‐born foal
Authors: Comline R. S. , Silver Marian 
Published: December 2014

1. The content and output of adrenaline and noradrenaline from the equine adrenal medulla has been investigated under different conditions in foetuses, foals and adult mares.2. In the foetus only small amounts of both amines were secreted in response to stimulation of the peripheral ends of the splanchnic nerves to the gland; during anoxia the adrenal discharge was far greater and was independent of any nervous mechanism.3. Whereas in the ruminant a direct adrenal response to low PO2 is confined to the noradrenaline cells during foetal life only, the adrenal medulla of the foetal foal secreted both adrenaline and noradrenaline during asphyxia, and the direct response persisted for some days after birth. Noradrenaline was the amine predominantly released during asphyxia in the foetus.4. Catecholamine output from the equine adrenal medulla changed with age, in that there was a gradual increase in both the absolute and relative amount of adrenaline released, irrespective of the stimulus applied, although at any given stage of development a higher proportion of adrenaline was secreted in response to stimulation of the splanchnic nerves than during anoxia.5. The relative proportions of the two amines in the effluent blood bore little resemblance to those found in the glands, removed after prolonged asphyxia, in either foetuses or foals. Preliminary observations have indicated that more noradrenaline is present in the glands when the foetus remains relatively undisturbed within the uterus.6. The possible significance of the larger adrenal response to asphyxia in the foetal foal in comparison with other species is discussed in relation to the development of the innervation and the growth of the adrenal cortex.
The permeability of mammary ducts
Authors: Linzell J. L. , Peaker M. 
Published: December 2014

1. The permeability of the teat mucosa of the goat has been studied in vitro and, as an isolated teat pouch, in vivo. In vivo the mucosa was found to be impermeable to radioactive Na, K, Cl and Rb isotopes and to labelled lactose, but permeable to 3HOH, and to a lesser extent, urea.2. The permeability of the intramammary ducts has been assessed by comparison of the rates of passage from the blood of ions and urea relative to 3HOH into various fractions of milk in different parts of the gland.3. Negligible quantities of ions were detected in the milk present in large ducts after an
I.V. infusion or during a close arterial infusion to keep the venous blood concentrations constant. However, after approximately 25 min, milk in the alveoli had fully equilibrated with 3HOH, and 24Na+ and was almost fully equilibrated with urea but not with 42K+ and 36Cl−.4. The quantity of milk in a fraction of milk was directly related to the amount of 3HOH present in that fraction but not to the amounts of the other indicators (urea, labelled Na, K, Rb and Cl). Comparison of the concentration of these substances with 3HOH in different milk fractions indicates that the mammary ducts are probably impermeable to ions and only slightly permeable to urea.5. The injection of [14C]lactose into the teat showed that after 10 and 20 min, 7 and 14% respectively of the radioactivity had reached the residual (alveolar) milk. Thus diffusion within the milk in the ducts could account for the small quantities of labelled ions found in milk within the ducts following intravascular injection.6. It is concluded that the large and medium‐sized ducts in the mammary gland are impermeable to lactose and to the monovalent ions studied.7. In non‐lactating animals, the ducts are more permeable to Na+ and Cl− than in the lactating animals.8. The relative rates of passage of ions into residual (alveolar) milk was Na > Cl > K.
The effects of oxytocin and milk removal on milk secretion in the goat
Authors: Linzell J. L. , Peaker M. 
Published: December 2014

1. When goats were milked each hour after being given a dose of synthetic oxytocin within the range thought to be released by the pituitary, there was a progressive rise in milk yield becoming statistically significant by 5 hr. The effect was reduced if the milk was not removed from the gland each hour.2. Milking transplanted glands each hour without injecting oxytocin also increased milk yield. The yield of the unmilked glands on the same animals was not affected. Massaging the transplanted glands had no effect on the milk yield.3. Oxytocin treatment and, to a lesser extent, frequent milking without oxytocin, altered milk composition. [Na], [Cl] and [non‐casein protein] increased; [K] and [lactose] decreased.4. Oxytocin infusions permitted the leakage of [14C]lactose from milk to plasma and [14C]sucrose from plasma to milk.5. In some goats very small doses of oxytocin caused changes in milk composition and in one such animal these changes were mimicked by the close arterial infusion of bradykinin.6. Reasons are given for believing that the changes in composition are incidental to the main action of oxytocin in expelling milk and could be caused by a small number of leaks between the tight junctions connecting secretory cells.7. The increase in the rate of milk secretion following milk removal is probably of greater physiological significance than the small changes in milk composition and supports Levy's idea of a local negative feed‐back via a chemical component of milk.
The membrane properties of the smooth muscle of the guinea‐pig portal vein in isotonic and hypertonic solutions
Authors: Kuriyama H. , Ohshima K. , Sakamoto Y. 
Published: December 2014

The membrane properties of the longitudinal smooth muscle of the guinea‐pig portal vein were investigated under various experimental conditions.1. In isotonic Krebs solution, the membrane potential (−48·7 mV), the maximum rates of rise and fall of the spike (4·6 and 2·3 V/sec respectively), the space constant (0·61 mm), the conduction velocity of excitation (0·97 cm/sec) and the time constant of the foot of the propagated spike (18·4 msec) were measured.2. The various parameters of the muscle membrane in the isotonic solution were compared with those in the hypertonic solution prepared by the addition of solid sucrose (twice the normal tonicity).3. When the muscles were perfused with hypertonic solution, marked depolarization of the membrane and increased membrane resistance occurred. These were probably due to reduction of the K permeability, increased internal resistance of the muscle and shrinkage of the muscle fibre.4. The membrane potential in isotonic and hypertonic solutions was analysed into two components, i.e. the metabolic (electrogenic Na‐pump) and the ionic (electrical diffusion potential) component in the various environmental conditions.(a) In isotonic and hypertonic solutions, the membrane was depolarized by lowering the temperature or by removal of K ion from the solutions. When the tissues were rewarmed or on readdition of K ion, the membrane was markedly hyperpolarized. These hyperpolarizations of the membrane were suppressed by treatment with ouabain (10−5 g/ml.), by warming to only 20° C and by K‐free solution.(b) The relationships between the membrane potential and the [K]o in isotonic Krebs, in the hypertonic (sucrose) Krebs, in the Na‐free (Tris) Krebs and in the Cl‐deficient (C6H5SO3) Krebs were observed. The maximum slopes of the membrane depolarization against tenfold changes of [K]o were much lower than that expected if it behaved like a K electrode.(c) In Na‐free (Tris) solution, the membrane was not depolarized in isotonic condition but it was depolarized in hypertonic condition.5. The low membrane potential in hypertonic solution (−37 mV) compared with isotonic solution (−49 mV) was thought to be mainly due to suppression of K permeability of the membrane and not due to suppression of the metabolic component.The electrogenic Na‐pump and the membrane potential of the portal vein was discussed in relation to other excitable cell membranes.
The Florida retinal densitometer
Authors: Hood C. , Rushton W. A. H. 
Published: December 2014

1. In Part I the principles of reflexion densitometry are discussed in relation to the measurements of visual pigments in man.2. In Part II the new Florida densitometer is described in some detail, and records are shown of the instrument's performance with pigment in equilibrium or changed by bleaching.3. With an artificial eye the fluctuations are of the order to be expected from quantum noise and limit the precision of one measurement to 0·0035 of ‘double density’ which corresponds to some 2% of total pigment.4. Part III treats of the reliability and significance of the measurements in living man. It needs ten repeated measurements to attain the reliability of 1 with the artificial eye.5. The measuring light used bleaches cone pigments by 0·4% in the 6 sec required to make a measurement.6. The interpretation of the measurements is briefly discussed.
Stiles—Crawford effect and the bleaching of cone pigments
Authors: Coble J. R. , Rushton W. A. H. 
Published: December 2014

1. The efficiency of light entering the eye through various points in the pupil (Stiles—Crawford effect) was studied using two criteria: (a) visual brightness judged by flicker fusion and (b) the rate of cone pigment bleaching measured by reflexion densitometry.2. Both measurements were made in the same apparatus with the same geometry of presentation and both gave the same Stiles—Crawford effect.3. This suggests that the densitometer measures pigment deep in the outer segments of the cones where light is absorbed for vision.4. Foveal cones seem all to point in the same direction, since the fraction of pigment bleached by light entering the pupil at any one point is the same when measured by light entering anywhere.