bluuebunny/crossref_metadata_2025_split huggingface dataset:
The absorption of polyvinyl pyrrolidone by the new‐born pig intestine
Authors: Hardy R. N. 
Published: December 2014

1. The intestinal absorption of [131I]polyvinyl pyrrolidone of mean mol. wt. 160,000 (K. 60) and 40,000 (K. 30) after oral administration has been measured in unsuckled conscious pigs less than 20 hr old. Absorption was assessed by the measurement of the concentration of [131I]PVP in venous blood during the 6 hr after feeding and also by the distribution at the end of the experiment of [131I]PVP between homogenates of the alimentary tract and homogenates of the rest of the animal.2. The concentration of [131I]PVP in the peripheral blood after feeding was dependent upon the mol. wt. of the polymer, when comparable amounts had been absorbed from the intestine. PVP K. 60 attained higher blood concentrations than PVP K. 30 and the blood concentrations of PVP K. 60 were close to the values to be expected if all the material which had left the intestine had remained in the blood. The lower blood concentrations found when PVP K. 30 was fed were associated with the disappearance of labelled solute from the gut and were thus the consequence of the relatively rapid escape of labelled solute from the plasma after absorption had taken place.3. The ability of the intestine to absorb [131I]PVP K. 60 declined progressively after birth but did not terminate abruptly unless the animal was fed colostrum. In unsuckled animals the rate and extent of absorption at 3 hr was much greater than at 20 hr after birth, but some absorption was still present at least 65 hr after birth.4. The transfer of PVP K. 60 to the peripheral blood was dependent upon factors in sow colostrum, since significant absorption did not occur when PVP was fed in water or simple salt solutions.5. The factors which accelerated absorption were present in colostrum from the goat, cow and ewe as well as that from the sow; they remained in the whey, but, in contrast to the factors which accelerate absorption in the calf, were largely inactivated by boiling. Similarly, neither phosphate, lactate, pyruvate, nor lower volatile fatty acid salts, which were effective in the calf, accelerated absorption in the pig.6. The absorption of [131I]PVP K. 30 was found to be much less dependent upon the composition of the solvent than the absorption of [131I]PVP K. 60, although absorption was most rapid when PVP K. 30 was fed in colostrum.
Bovine splenic nerve: characterization of noradrenaline‐containing vesicles and other cell organelles by density gradient centrifugation
Authors: Hörtnagl H. , Hörtnagl Heide , Winkler H. 
Published: December 2014

1. Homogenates of bovine splenic nerves were subjected to differential and sucrose density gradient centrifugation. From the low‐speed supernatant a high‐speed sediment (mitochondria, lysosomes, microsomes and noradrenaline (NA) vesicles) was obtained. By density gradient centrifugation of this sediment it was shown that NA vesicles are slightly less dense than mitochondria, but denser than microsomes.2. In further experiments a mitochondrial and a microsomal sediment were obtained. The mitochondrial sediment was fractionated with a short centrifugation time over a density gradient ranging from 0·6 to 1·2
M sucrose. Mitochondria (fumarase and succinate‐dehydrogenase) and lysosomes (acid ribonuclease and deoxyribonuclease) sedimented to the bottom of the tube. The highest concentration of NA vesicles was found in a medium position. There was only a small amount of microsomes (glucose‐6‐phosphatase) present.3. The microsomal sediment was centrifuged for 150 min over a density gradient ranging from 0·8 to 1·4
M sucrose. The microsomes remained on the top of the gradient. There were also some mitochondria and lysosomes present. The NA vesicles were found in highest concentration in the middle of the gradient (at about 1·2
M sucrose).4. With the use of these two density gradients, the subcellular distribution of dopamine‐β‐hydroxylase, monoamine oxidase and ATPase was studied. Dopamine‐β‐hydroxylase was found to be localized in the NA vesicles. Monoamine oxidase was mainly recovered in mitochondria; a small part of the enzyme appeared to be microsomal. ATPase was present in microsomal elements.
Calculation of the membrane potential in smooth muscle cells of the guinea‐pig's taenia coli by the Goldman equation
Authors: Casteels R. 
Published: December 2014

1. The intracellular K+, Cl− and Na+ concentrations in the taenia coli cells of the guinea‐pig have been estimated from the total ion content or the extrapolated intracellular tracer content, the sorbitol space and the dry wt./wet wt. ratio.2. The exchange of K+, Cl− and Na+ was studied by following the uptake and the efflux of these ions with radioactive isotopes. The following efflux values have been calculated: mK, 4 p‐mole.cm−2.sec−1; mCl, 8·4 p‐mole.cm−2.sec−1 and mNa, 7·2 p‐mole.cm−2.sec−1. These flux values agree well with the influx values, obtained under the same experimental conditions.3. The slowness of diffusion in the extracellular space reduces the Na flux by about 2·5% and the K flux by about 30%. A correction factor of 1·3 has to be introduced to obtain the true K flux.4. The values for the permeability constants calculated by the constant field assumptions are for PK, 11 × 10−8 cm/sec; PCl, 6·7 × 10−8 cm/sec and for PNa, 1·8 × 10−8 cm/sec. The introduction of these values and of the ion concentrations in the Goldman equation gives a resting potential of −37 mV.5. One of the possible explanations for the discrepancy between the measured resting potential and the calculated one, is that the resting potential of these smooth muscle cells is partly a diffusion potential and partly due to the operation of an electrogenic Na pump.
The transient electric responses of the cochlea
Authors: Stopp Phyllis E. 
Published: December 2014

1. DC responses were recorded from the cochleae of pigeons, cats and guinea‐pigs. In addition to the known summating potential, transients of the same polarity were observed at the onset and termination of the tonal stimulus.2. These transients were most noticeable in the pigeon, being least in the guinea‐pig responses.3. They could be modified by changing the rate of rise and fall of the stimulus envelope, but not by cutting the middle ear muscles.4. Comparable effects were seen when the ear was directly driven by a mechanical stimulus.5. With stimuli of long duration the off‐transient was usually masked by a slow potential of opposite polarity. This deflexion appears to be an afterpotential, rather than a mechanical transient, since it is dependent on the duration of the preceding stimulus.
Quantitative aspects of gain and latency in the cat retina
Authors: Cleland B. G. , Enroth‐Cugell Christina 
Published: December 2014

1. The gain of the central response mechanism and the latency of the pure central response of on‐centre ganglion cells were studied by recording from single optic tract fibres the responses evoked by slow square‐wave stimuli applied against some steady background.2. The concept of effective flux was introduced and defined: if any portion of a stimulus extends beyond Ricco's area of complete summation, then that stimulus has an actual flux, equal to the product of its area and luminance, but it also has an effective flux which is that fraction of its actual flux which equals the actual flux of another stimulus which, when it falls entirely within Ricco's area, evokes an isobolic pure central response or has the same adaptive effect upon the central response mechanism as the first stimulus.3. The most significant finding was that when the cell responded with a pure central response to the incremental flux (the square wave) applied against a steady effective background flux, then the gain and the latency were functions exclusively of the sum of the two fluxes (the total flux), not of the incremental or background flux as such. This shows that the level of field adaptation of the central mechanism is reset within the latent period of the response to an incremental flux.4. Increment sensitivity curves based on isobolic suprathreshold responses all had the same slope of 0·9, when the log of the incremental flux was plotted against the log of the total flux. A plot of log latency against log total effective flux had a slope of −0·1.5. The stimulus—response relation derived from (3) and (4) was [Formula: see text] and [Formula: see text], where R is the response amplitude, Fet the total flux, ΔFe the incremental flux and K1 and K2 are constants.
Distance effects in human scotopic retinal interaction
Authors: Westheimer Gerald , Wiley R. W. 
Published: December 2014

1. Using the threshold for a small, brief test flash as a measure, the effect of light stimulation of small adjacent retinal regions of the human retina was investigated during adaptation to a medium scotopic illuminance.2. Within about ½° of the tested area, light causes a desensitization gradually decreasing with distance. Beyond that there is a sensitizing zone which in turn gives way to an outer desensitizing zone. The sign of these effects is reversed if the peripheral stimulus is a patch of darkness.3. Evidence for non‐linearity of summation of individual patches was found. Occlusion of each other's sensitizing influence is observed if two regions are closely adjacent to each other.
The attenuation of rod signals by backgrounds
Authors: Alpern M. , Rushton W. A. H. , Torii S. 
Published: December 2014

1. The paper which precedes this investigated the nerve interaction between two flashes, λ at centre (Fig. 1a) and ϕ on the surround region (but not on the centre). The size of the inhibitory nerve signal V generated by ϕ is given by V = ϕ(ϕ + σ), where σ is the semi‐saturation constant.2. A former paper (Alpern & Rushton, 1967) had shown that when the flash ϕ falls upon a steady background θ, V suffers attenuation in the G‐box (Fig. 1b) down to the fraction θD/(θD + θ) where θD is the eigengrau or receptor noise. Thus, in general, the nerve signal N is given by [Formula: see text].3. This formula had only been established for a moderate range of values. In this paper we use extreme values to explore the limits of its validity. We find the equation to be true over the entire intensity range where N is measurable.4. Six different types of experiment have been performed to test various features of the equation. For instance, if log N is plotted against log ϕ for various fixed values of θ, the curve is always the same with simply a vertical shift. And the shift is equal to log(1 + θ/θD) for all values both of θ and of ϕ.5. The most interesting curve is the plot of log ϕ against log θ for fixed N. This is similar to the Weber—Fechner increment threshold but the criterion is not that ϕ be strong enough to be detected, but strong enough to generate an N signal just sufficient to inhibit some fixed λ flash. These curves (below the onset of saturation) are all the same except for vertical separation, and prove that the condition for flash detection is that a fixed signal, N0, is generated of size 10−5 of the maximum signal obtainable (i.e. with ϕ large and θ zero).6. With strong backgrounds the curves of (5) above exhibit a marked saturation of the Aguilar & Stiles’ type (1954). The family of curves each with a fixed N value shows a remarkable symmetry (Fig. 8) which in fact follows from the equation in (2) above. It has nothing to do with bleached pigment, but follows from the equation in (1) above. V there cannot exceed unity, thus when scaled by the G‐box below the criterion level, further increase in ϕ will not bring improvement.
Fat metabolism in brown adipose tissue in vivo
Authors: Hardman M. J. , Hull D. 
Published: December 2014

1. Noradrenaline infusions (
I.V. for 30 min) in new‐born and 1‐week‐old unanaesthetized rabbits caused a rapid and sustained rise in oxygen consumption and an increase in blood glucose, free fatty acid and glycerol concentrations. Similar changes occurred in anaesthetized 1‐week‐old rabbits.2. A simple direct method was used to measure the net exchange of metabolites across brown adipose tissue in anaesthetized young rabbits. It was found that the brown adipose tissue of rabbits reared from birth in a thermoneutral environment and studied when their next feed was due took glucose from and released fatty acids and glycerol into the circulation.3. Similar rabbits kept unfed for a further 48 hr in a warm environment released fatty acids and glycerol from their brown adipose tissue at a far greater rate, but the rate of glucose uptake was reduced.4. On the other hand the brown adipose tissue of rabbits kept unfed in a cold environment (20°C) took up circulating free fatty acids as well as glucose and did not release glycerol. The brown adipose tissue of these rabbits was depleted of fat.5. The rate of blood flow through brown adipose tissue and the exchange of all three metabolites increased fourfold during noradrenaline infusion in the three groups of rabbits.6. It is concluded (i) that brown adipose tissue releases significant amounts of fatty acids and glycerol into the circulation and that this contribution is greatly increased with noradrenaline infusion and presumably cold exposure, and (ii) that brown adipose tissue depleted of fat produces heat by drawing free fatty acids as well as glucose from the circulation.
Oscillation in the stretch reflex arc and the origin of the rhythmical, 8–12 c/s component of physiological tremor
Authors: Lippold O. C. J. 
Published: December 2014

1. A brief downward, stepwise displacement applied to the outstretched finger gives rise to a train of approximately sinusoidal movements of it, lasting often more than 1 sec. The frequency of these waves is the same, in any one subject, as that of physiological tremor.2. The oscillations are regular in form, and bear a constant phase relation to the applied displacement; they can be summated using an averaging computer (Biomac 1000) triggered by the mechanical stimulus.3. The oscillations are altered in the same way as is physiological tremor by a number of factors. Cooling the arm before recording lowers the frequency, warming raises it, while the application of an arterial cuff decreases the amplitude and tends to elevate the frequency. These factors have effects of similar magnitude on both the oscillations and the tremor.It thus appears highly likely that the waves produced by a mechanical input and physiological tremor waves are due to the same process, namely oscillation in an underdamped servo‐system.4. The oscillation is not due simply to the mechanical, die‐away resonance of the finger, because bursts of muscle action potentials can be recorded in phase with the finger movements both in the wave train evoked by the mechanical displacement and during normal tremor.5. It is concluded that physiological tremor in the 8–12 c/s band is due to oscillation in the stretch reflex servo‐loop.
The location of the chemoreceptor controlling gastric acid secretion during hypoglycaemia
Authors: Colin‐Jones D. G. , Himsworth R. L. 
Published: December 2014

1. The injection of 2‐deoxy‐D‐glucose directly into the lateral hypothalamic area of rats, but not elsewhere, caused a prompt and sustained secretion of acid by the stomach at a rate comparable to that due to insulin hypoglycaemia.2. Acid secretion provoked by such injections, like that resulting from hypoglycaemia, could be stopped by raising the plasma glucose concentration by the intravenous infusion of glucose.3. Unilateral intrahypothalamic injection of 2‐deoxy‐D‐glucose activated both vagi for, although cutting one vagus reduced the secretion, division of both was necessary to abolish it.4. Gastric acid secretion evoked by a systemic stimulus (insulin‐induced hypoglycaemia or intravenous 3‐O‐methylglucose) could be prevented by inactivating the lateral hypothalamic area on each side with phenol or lignocaine.5. It is concluded that there exists in the lateral hypothalamic area a chemoreceptor, responsive to a lack of metabolizable glucose, which can initiate and sustain the vagally mediated secretion of acid by the stomach.
The effects of nerve stimulation and hemicholinium on synaptic vesicles at the mammalian neuromuscular junction
Authors: Jones S. F. , Kwanbunbumpen Suthiwan 
Published: December 2014

1. Electron micrographs of nerve terminals in rat phrenic nerve—diaphragm preparations have been studied. This has been done before and after prolonged nerve stimulation. The effectiveness of nerve stimulation has been monitored by intracellular micro‐electrode recordings from the muscle cells.2. Characteristic changes in the form and distribution of the nerve terminal mitochondria were noted after nerve stimulation.3. Synaptic vesicle numbers in the region of nerve terminal less than 1800 Å from the synaptic cleft were significantly greater in tissue taken 2 and 3 min after nerve stimulation, than in unstimulated preparations.4. The long and short diameters of the synaptic vesicle profiles less than 1800 Å from the synaptic cleft were measured. Analysis of the distribution of the diameters indicated synaptic vesicles to be basically spherical structures. Estimates of synaptic vesicle volume were made from the measurements. Synaptic vesicle volume was significantly reduced in tissue taken 2 and 4 min following nerve stimulation.5. If hemicholinium, a compound which inhibits acetylcholine synthesis, was present during the period of nerve stimulation, much greater reductions in synaptic vesicle volume occurred. Synaptic vesicle numbers in the region of nerve terminal less than 1800 Å from the synaptic cleft were also reduced, compared with unstimulated control preparations.6. These results are regarded as support for the hypothesis that the synaptic vesicles in nerve terminals at the mammalian neuromuscular junction represent stores of the transmitter substance, acetylcholine.
Effect of asphyxia due to umbilical cord occlusion in the foetal lamb on leakage of liquid from the circulation and on permeability of lung capillaries to albumin
Authors: Adamson T. M. , Boyd R. D. H. , Hill June R. , Normand I. C. S. , Reynolds E. O. R. , Strang L. B. 
Published: December 2014

1. Experiments were performed on foetal lambs, exteriorized at Caesarean section, to determine the effects of asphyxia on the leakage of liquid from the circulation and on the permeability of lung capillaries to albumin. Following a period of control observation (30–120 min) the foetus was asphyxiated by occlusion of the umbilical cord for 5‐10 min and then allowed to recover while observations were continued for a further 20–80 min.2. Measurements were made of the lymph flow from the lungs, that had drained via the thoracic duct; of protein concentration in lymph and plasma; of arterial blood haematocrit, pH, PO2 and PCO2; and of arterial and left atrial pressures and heart rate. Human serum albumin labelled with 125I was infused intravenously during the control period and 125I count rates were followed in plasma and lymph throughout the experiment. Values for the transfer coefficient of albumin (Ė/V min−1, i.e. interstitial fluid clearance of albumin per unit of lung interstitial fluid volume) were determined during control, cord‐occlusion and post‐occlusion periods.3. During cord occlusion arterial and left atrial pressure, haematocrit and plasma protein concentration all rose, returning to the control value by 20 min after release of cord occlusion. The haematocrit values indicated that about 9% of the blood volume was temporarily lost from the circulation. Lung lymph flow also increased, reaching a maximum in the 5 min period after release of occlusion and returning to the control level 15 min later. Values for Ė/V of albumin were at no time significantly different from those during the control period.4. It was concluded that acute foetal asphyxia produced by umbilical cord occlusion caused an increased leakage of liquid from the circulation in general. This effect was temporary and was probably due to an increase in capillary pressure during cord occlusion. The asphyxia had no persistent effect on the permeability of lung capillaries to albumin.
Physiological and morphological identification of horizontal, bipolar and amacrine cells in goldfish retina
Authors: Kaneko Akimichi 
Published: December 2014

1. Intracellular recordings were made from various types of cells in the isolated goldfish retina, and Procion Yellow was injected from the recording pipette in order to identify histologically the structure recorded. The dye diffused and stained the cell body and processes down to the fine branches.2. S‐potentials were identified as coming from the external horizontal cells and from the internal horizontal cells. Both L‐ and C‐type S‐potentials were found in both regions, and no histological differences were seen in cells giving these two types of responses. S‐potentials recorded from the external horizontal cells showed less spatial summation than those recorded from the internal horizontal cells.3. Bipolar cell responses consisted of sustained potentials associated with an antagonistic centre‐surround type receptive field (on‐centre, off‐surround or vice versa). Spike activity was not observed in bipolar cells.4. Amacrine cells responded with transient depolarization both at the beginning and at the end of illumination. They sometimes showed spike activity. The amplitude of on‐ and off‐depolarization showed slight dependence on stimulus geometry but a distinct centre‐surround organization was not observed.
Effects of iontophoretically applied drugs on spinal interneurones of the lamprey
Authors: Martin A. R. , Wickelgren Warren O. , Berànek R. 
Published: December 2014

1. Intracellular records were obtained from giant interneurones in the isolated spinal cord of the sea lamprey. The cells had a mean resting potential of about 75 mV and action potentials with overshoots of about 35 mV. Their input resistances, measured by passing polarizing currents through the recording pipette, were in the range 3‐7 MΩ.2. Iontophoretic ejection of γ‐aminobutyric acid (GABA) from a micropipette placed near the surface of a cell resulted in a slight hyperpolarization, accompanied by a marked reduction in input resistance. The reversal point for the potential change was about 5 mV greater than the resting membrane potential.3. Iontophoretic application of
L‐glutamate to the cells produced a depolarization with a decrease in input resistance much smaller than that accompanying a GABA potential of similar amplitude. The action potential amplitude was reduced by
L‐glutamate application. The reversal potential could not be determined accurately but appeared to be near zero membrane potential.4. Glutamate application produced, in addition, a burst of inhibitory synaptic potentials in the cell, presumably by depolarizing either inhibitory presynaptic nerve terminals or nearby inhibitory cell bodies.5. Acetylcholine (ACh) produced no detectable change in membrane resistance or potential.6. Application of the three drugs to first‐order sensory cells in the spinal cord had no effect on their membrane properties.