bluuebunny/crossref_metadata_2025_split huggingface dataset:
Luminance‐dependent changes in mesopic visual contrast sensitivity
Authors: Smith Robert A. 
Published: December 2014

Spatial and temporal modulation transfer functions have been measured as a function of luminance at scotopic and mesopic levels. It is found that throughout the scotopic range the data can be accounted for by a two process visual system, with the processes having the following properties.Simple excitatory processThis mechanism summates over somewhat less than 1 square degree of visual angle and over about 200 msec of time. These properties do not change with luminance, but the over‐all sensitivity of the mechanism follows the De Vries—Rose law. The temporal properties of this mechanism follows those of the scotopic b‐wave. At high luminances, the temporal, but not spatial, properties of this mechanism break down in a manner which had not been studied.Low‐frequency inhibitory processThis process is manifest as a decrease in sensitivity from that of the simple excitatory process. Its effect is observed only when both spatial and temporal frequency are low, suggesting that it has a larger (perhaps 3 ×) summation area in both space and time. The inhibitory process is not observed below a certain threshold luminance, which is highly dependent upon the configuration of the stimulus. For a suitable stimulus, this threshold will be well into the scotopic luminance range.It is suggested that these two processes represent psychophysical correlates of the centre and surround of retinal receptive fields.
The effect of citric acid and its sodium salts in test meals on the gastric outputs of acid and of chloride
Authors: Hunt J. N. , Knox M. T. 
Published: December 2014

Five subjects were given 750 ml. test meals lasting 10–20 min, containing 0–300 m
N citric acid, monosodium dihydrogen citrate, disodium monohydrogen citrate or trisodium citrate.1. Increase in concentration of sodium citrate in the range 0–125 m
N gave increasing outputs of acid and chloride.2. The more acid the meal for any given citrate ion concentration, the less the output of acid and chloride.3. The greater the concentration of an acid citrate salt, the less the output of acid.4. There was evidence of loss of acid from the stomach by diffusion with the more acid meals.
Innate seasonal oscillations in the rate of milk secretion in goats
Authors: Linzell J. L. 
Published: December 2014

1. When goats were kept in continuous milk production for 2–4 yr the rate of milk secretion oscillated in a sinusoidal fashion with a mean wavelength of 49·7 ± 1 weeks, being highest in summer and lowest in winter.2. Milk [Cl] tended to be higher in summer and [protein] highest in winter but there were no seasonal changes in [fat], [lactose], [Na] or [K].3. There were no seasonal oscillations in body weight but the udders were larger in summer than in winter although this did not solely account for the changes in milk yield.4. Although the autumnal fall in yield and the rise in the spring coincided with the breeding season, seasonal variations also occurred in two ovariectomized animals.5. Seasonal fluctuations were independent of diet, occurring equally in animals that had never eaten grass but were fed continuously on dry feed and hay ad libitum.6. Annual oscillations in yield and udder size but not [protein] and [Cl] were also exhibited in two goats kept in a constant temperature chamber at 14 ± 2° C, fed every 2 hr and subjected continuously to 16 hr light and 8 hr dark. These observations have so far persisted for 2 yr in one goat and for 3 yr in the other. However, the wave‐length was reduced to 45 ± 1 weeks. Oestrus was suppressed for 2 years.
Efferent control of arterial chemoreceptors mediated by glossopharyngeal fibres and artifacts introduced by stimulation techniques
Authors: Goodman N. W. 
Published: December 2014

1. In anaesthetized cats, stimulation of the cut carotid sinus nerve generally caused a reduction in discharge in afferent fibres peeled from the nerve distal to the stimulating electrodes, though this was somewhat variable. In four out of five fibres the inhibition was reduced or abolished by close intra‐arterial injection of atropine. Only single fibres were used.2. There was a risk of adventitious excitation of the afferent fibre by stimulus escape. Some of the features of this excitation and the ease with which it occurred were investigated using an isolated length of vagus, baroreceptor fibres and chemoreceptor fibres. Low concentrations of local anaesthetic could raise the threshold for adventitious excitation whilst not affecting the normal passage of impulses.3. During stimulation of the efferent components of the sinus nerve, a continuous check for adventitious excitation was kept, utilizing the fact that chemoreceptor fibres show a minimum inter‐spike interval of about 10 msec.4. The true inhibition of discharge would seem to be vasomotor in origin.
The effect of glycerol treatment on crab muscle fibres
Authors: Papir Dalia 
Published: December 2014

1. Membrane constants of the closer muscle of the ghost crab, Ocypoda cursor, were determined before and after treatment in hypertonic glycerol solution and return to an artificial sea‐water (
A.S.W.) solution.2. Muscle contraction was abolished after return of the muscle to
A.S.W.3. The membrane capacitance was reduced from 29·0 μF/cm2 to 10·5 μF/cm2.4. Other passive properties of the muscle membrane, not dependent on capacitance, were not changed.5. The presynaptic nerve, transmitter release, post‐synaptic sensitivity to transmitter and ionic mechanisms of synaptic action were unaffected by glycerol treatment.6. More than 60% of the membrane capacitance/unit area is contributed by the complex tubular system.7. The tubular system in crustacea is necessary for excitation‐contraction coupling.
The orderly recruitment of human motor units during voluntary isometric contractions
Authors: Milner‐Brown H. S. , Stein R. B. , Yemm R. 
Published: December 2014

1. The contractile properties of human motor units from the first dorsal interosseus muscle of the hand were studied during voluntary isometric contractions using recently developed techniques.2. The twitch tensions produced by motor units varied widely from about 0·1–10 g. The twitch tension of a motor unit varied nearly linearly as a function of the level of voluntary force at which it was recruited over the entire range of forces studied (0–2 kg).3. The number of additional motor units recruited during a given increment in force declined sharply at high levels of voluntary force. This suggests that even though the high threshold units generate more tension, the contribution of recruitment to increases in voluntary force declines at higher force levels.4. Contraction times for these motor units varied from 30 to 100 msec. Over 80% had contraction times less than 70 msec, and might be classed as fast twitch motor units. The larger motor units, which were recruited at higher threshold forces, tended to have shorter contraction times than the smaller units.
Reconstitution of the sodium pump from protein and phosphatidylserine: features of ouabain binding
Authors: Chipperfield A. R. , Whittam R. 
Published: December 2014

1. A study has been made of ATP splitting and ouabain binding to the sodium pump reconstituted from protein and phosphatidylserine.2. Ouabain was bound to protein alone, but when phosphatidylserine was added, binding was increased threefold. The stimulation resembled the course of activation of sodium‐dependent ATPase activity.3. EGTA partly simulated the activation of ATPase by phosphatidylserine but did not enhance binding.4. The dissociation constant for the enzyme‐ouabain complex was 3·5 × 10−8
M. The turnover number (2,000 molecules of ATP per minute) and the number of receptor sites (3·8 × 1013 per mg protein) were calculated.5. The results provide further evidence of the involvement of phosphatidylserine in the action of the sodium pump.
The characteristics of ‘end‐plate noise’ produced by different depolarizing drugs
Authors: Katz B. , Miledi R. 
Published: December 2014

1. End‐plate depolarization and associated ‘membrane noise’ due to decamethonium, acetylthiocholine and suberyldicholine have been examined and compared with the effects of acetylcholine and carbachol.2. The transient ionic channels resulting from the action of decamethonium and acetylthiocholine are of much shorter duration than those produced by acetylcholine. They are, therefore, similarly to carbachol channels, less effective in causing membrane depolarization.3. Suberyldicholine, on the other hand, produces ion channels whose duration exceeds that of acetylcholine.4. Lowering the temperature causes an increase in amplitude of the elementary potential change produced by decamethonium and acetylthiocholine.5. The relation between the characteristic features of drug‐induced membrane noise and the underlying molecular reaction rates is discussed.
Receptive fields of simple cells in the cat striate cortex
Authors: Bishop P. O. , Coombs J. S. , Henry G. H. 
Published: December 2014

1. The excitatory and inhibitory components in the receptive fields of unimodal simple cells in the striate cortex of the cat anaesthetized with nitrous oxide have been described using slits of light and single light‐dark edges as stimuli.2. There is a small excitatory region (excitatory complex) centrally located in the receptive field that is made up of various combinations and spatial arrangements of subliminal excitatory and discharge subregions or centres.3. The subliminal excitatory centres were revealed by a binocular facilitation technique. The excitability of the cell was raised by repeated stimulation via one eye while the neurone was tested with single edges via the other eye.4. The subliminal excitatory and discharge centres are each specifically activated by only one type of edge, light‐dark or dark‐light, and then only in one direction of motion. All the subregions in the excitatory complex have the same optimal stimulus orientation.5. Inhibitory components in the receptive field were identified by stimulating the cell with bars of light and single edges against an artificial background discharge produced by repeated stimulation separately applied either to the same eye (monocular conditioning) or to the other eye (binocular conditioning). There are powerful inhibitory sidebands to either side of the excitatory complex and these inhibitory regions merge to include the excitatory complex when stimulus orientation is angled away from the optimal.6. Excitation is highly stimulus specific whereas inhibition is non‐specific.7. The organization of the two receptive fields of a binocularly discharged cell can be closely similar.8. The attempt is made to translate the concept of subliminal excitatory and discharge centres into specific neural mechanisms involving both the geniculo‐cortical input and various intracortical circuits.9. These new developments call for only minor modifications to the model we have proposed for the organization of the receptive field.
The influence of body core temperature and peripheral temperatures on oxygen consumption in the pig
Authors: Carlisle H. J. , Ingram D. L. 
Published: December 2014

1. The rate of oxygen consumption was measured in young pigs exposed to different ambient temperatures and the effect on metabolic rate of changing the temperature of thermodes implanted in the hypothalamus and over the spinal cord was determined. In some experiments the temperature of the skin over the trunk was changed by means of a water‐perfused coat.2. Cooling the hypothalamus or the spinal cord in a warm ambient did not change the rate of oxygen consumption. At a thermoneutral ambient temperature, cooling either thermode increased oxygen consumption. In a cold environment, cooling either thermode increased the rate of oxygen consumption more than at a thermoneutral temperature. The increase in the rate of oxygen consumption was greatest during cooling of the spinal cord and it appeared that the pigs also shivered more violently. Heating either thermode tended to decrease oxygen consumption in a cold environment.3. In pigs with thermodes both in the hypothalamus and over the spinal cord, cooling both thermodes was accompanied by a greater increase in oxygen consumption than cooling either thermode alone. The increase in oxygen consumption on cooling one thermode could be reduced by heating the other.4. The skin temperature (fixed by the water perfused coat, or the ambient temperature) at which the rate of oxygen consumption increased, was lowered during heating of the thermodes, but the rate of increase in oxygen consumption appeared not to change as a function of falling skin or ambient temperature.
Separate channels for the analysis of the shape and the movement of a moving visual stimulus
Authors: Tolhurst D. J. 
Published: December 2014

1. The effects of temporal modulation on the properties of spatial frequency channels have been investigated using adaptation.2. Adapting to drifting sinusoidal gratings caused threshold elevation that was both spatial frequency and direction specific. Little systematic difference was found between the band widths of the elevation curves for drifting and stationary gratings.3. It was confirmed that adaptation fails to reveal channels at low spatial frequencies when stationary gratings are used. However, channels were revealed at frequencies at least as low as 0·66 c/deg when the test gratings were made to move. These channels are adapted only a little by stationary gratings, confirming their dependence on movement.4. The existence of movement‐sensitive channels at low spatial frequencies explains the well known observation that temporal modulation greatly increases the sensitivity of the visual system to low spatial frequencies.5. Temporal modulation was effective at revealing these channels only when the flicker or movement of the test patterns was apparent to the observer; only at low spatial frequencies did patterns, modulated at low rates, actually appear to be temporarily modulated at threshold. At higher spatial frequencies, they were indistinguishable from stationary patterns until the contrast was some way above the detection threshold.6. It is suggested, therefore, that the movement‐sensitive channels are responsible for signalling the occurrence of movement; the channels at higher spatial frequencies give no information about temporal changes. These two systems of channels are compared to the Y‐ and X‐cells respectively of the cat.
Neurones in the ventrobasal complex of the rat thalamus responding to scrotal skin temperature changes
Authors: Hellon R. F. , Misra N. K. 
Published: December 2014

1. In rats the scrotal temperature was raised or lowered with a water‐perfused thermode while micro‐electrode recordings were made of unit activity in the ventrobasal complex of the thalamus. The electrodes were aimed at the region where evoked responses had been found by electrical stimulation of the scrotum. Recording sites were marked by iontophoresis of dye from the micro‐electrode.2. Changes in firing rate of thalamic neurones were only found in the scrotal temperature range of 31–40° C. Within this range, 72% of the 123 cells tested were excited or suppressed by skin warming. At temperatures above or below this range, activity was not affected. Most of the cells responded just to temperature and only 7% were also excited by touch.3. Raising temperature in the range 31–40° C caused 82% of the thermally responding cells to increase their firing rate and 18% to decrease their rate. Individual neurones showed a sudden and maintained change in their activity for scrotal temperature increases of only 2, 1 or even 0·5° C. Mean firing rates changed by factors of about 8 or more with these temperature increases and further warming did not change the rate. These step‐like changes in firing rate were found at different points over the whole skin temperature range of 31–40° C, but most were between 33 and 38° C.4. For a given neurone the step‐like change in activity occurred once its critical temperature was reached, irrespective of whether this was achieved by a step increase of skin temperature over 1–2 sec or by a slow ramp increase lasting several minutes.5. It is not possible to say whether the skin warm receptors, cold receptors or both were responsible for these thalamic responses, but the results do show that incoming thermal information is considerably processed when it reaches the thalamic level.
Placental iron transfer in the cat
Authors: Baker Erica , Morgan E. H. 
Published: December 2014

1. The transfer of iron from maternal plasma to the foetus was studied in the cat using cat transferrin labelled with 59Fe and radioiodine.2. Pregnancy was accompanied by a fall in maternal haematocrit, a rise in serum total iron‐binding capacity and iron stores, but no change in serum iron concentration or plasma iron turnover.3. Near‐term foetal haematocrit and serum iron concentration were higher and iron binding capacity lower than in the pregnant animals.4. The uptake of 59Fe from maternal plasma by the placenta and transfer to the foetuses were slow and small in amount. The daily transfer of iron to the foetuses calculated from these data was only 5 μg.5. There was a small, transient uptake of 59Fe from the plasma by the foetal membranes.6. Small amounts of plasma transferrin and albumin were slowly taken up by the placenta.7. It was concluded that the maternal endothelium of the placenta of the cat acts as a barrier for the uptake of plasma transferrin‐bound iron. As a result the rate of iron transfer to the foetuses from maternal plasma is inadequate to account for their rate of iron accumulation, and another source, such as maternal erythrocytes, must supply most of the iron to the foetuses.
Adaptation and dynamics of cat retinal ganglion cells
Authors: Enroth‐Cugell Christina , Shapley R. M. 
Published: December 2014

1. The impulse/quantum (I/Q) ratio was measured as a function of background illumination for rod‐dominated, pure central, linear square‐wave responses of retinal ganglion cells in the cat.2. The I/Q ratio was constant at low backgrounds (dark adapted state) and inversely proportional to the 0·9 power of the background at high backgrounds (the light adapted state). There was an abrupt transition from the dark‐adapted state to the light‐adapted state.3. It was possible to define the adaptation level at a particular background as the ratio (I/Q ratio at that background)/(dark adapted I/Q ratio).4. The time course of the square‐wave response was correlated with the adaptation level. The response was sustained in the dark‐adapted state, partially transient at the transition level, and progressively more transient the lower the impulse/quantum ratio of the ganglion cell became. This was true both for on‐centre and off‐centre cells.5. The frequency response of the central response mechanism at different adaptation levels was measured. It was a low‐pass characteristic in the dark‐adapted state and became progressively more of a bandpass characteristic as the cell became more light‐adapted.6. The rapidity of onset of adaptation was measured with a time‐varying adapting light. The impulse/quantum ratio is reset within 100 msec of the onset of the conditioning light, and is kept at the new value throughout the time the conditioning light is on.7. These results can be explained by a nonlinear feedback model. In the model, it is postulated that the exponential function of the horizontal cell potential controls transmission from rods to bipolars. This model has an abrupt transition from dark‐ to light‐adapted states, and its response dynamics are correlated with adaptation level.
Characteristics of a sulphydryl group essential for sodium exchange diffusion in beef erythrocytes
Authors: Motais R. , Sola F. 
Published: December 2014

1. In the beef red blood cell, the component of the Na efflux which is insensitive to ouabain but depends on the presence of external Na, is not affected by furosemide but is reduced by several agents: ethacrynic acid, dinitrofluorobenzene, p‐chloromercuribenzene (PCMB),
N‐ethylmaleimide and p‐chloromercuribenzene sulphonate (PCMBS). Some of these agents increased a parallel passive permeability which could mask the reduction of efflux.2.
N‐ethylmaleimide and PCMBS, which in our experimental conditions (initial concentration 5 × 10−4
M and 5 × 10−6
M respectively, haematocrit 7·7%) do not increase the leak, inhibit Na influx and efflux markedly and equally. This provides further evidence of the existence of a typical ouabain‐insensitive Na exchange diffusion in beef red blood cell.3. Inhibition of the exchange diffusion mechanism by
N‐ethylmaleimide or PCMBS is not total and their inhibitory effects are slightly additive. Various arguments suggest that their effects on exchange diffusion can be attributed to a reaction with sulphydryl groups.4. These sulphydryl groups are rapidly titrable by a poorly penetrating agent such as PCMBS, and the inhibitory effect is rapidly reversible. Thus, it is assumed that the sulphydryl groups containing proteins are superficially located on the outer border of the membrane.5. After inhibition, there is no change in half saturation constant for the complexing reaction for transfer, suggesting that the inhibited sites are no longer functioning but that the uninhibited sites are in every way normal.6.
N‐ethylmaleimide and PCMBS act similarly in sheep red blood cells.7. PCMBS does not affect sodium movement in human erythrocytes, but
N‐ethylmaleimide inhibits markedly the ouabain‐insensitive Na efflux.
Development of a mammalian fast muscle: dynamic and biochemical properties correlated
Authors: Drachman D. B. , Johnston D. M. 
Published: December 2014

1. The isometric properties and related biochemical properties of a developing rat fast muscle (extensor digitorum longus, EDL) have been determined during the 21 days after birth.2. At birth the maximum rate of rise of tension in a tetanus, a measure of speed of contraction, is slow; it begins to increase only after the 5th day and reaches adult values by 21 days.3. The increase in actomyosin ATPase activity of the rat EDL correlates closely (P ≪ 0·001) with the changes in the maximum rate of rise during the same period of development.4. The relaxation phase of a tetanic response begins to increase in speed promptly after birth, and reaches adult values by the 21st day. The rate of calcium accumulation by the isolated sarcoplasmic reticulum (SR) increases with a similar time course.5. The separate contributions of contraction and relaxation mechanisms to the changes in the more conventional isometric properties of maturing muscles have been analysed.