bluuebunny/crossref_metadata_2025 huggingface dataset:
Disparity processing of spatial frequencies in man
Authors: Felton Thomas B. , Richards Whitman , Smith Robert A.
Published: December 2014

1. Adaptation to a high‐contrast sine‐wave grating has been shown previously by Blakemore & Campbell (1969) to raise the modulation required to detect a low‐contrast grating that has the same or similar spatial frequency as the adapting grating.

2. A similar adaptation effect occurs when the adaptation and test gratings are seen binocularly and are presented off the plane of fixation. When the gratings are not located on the plane of fixation, however, the greatest rise in threshold following adaptation occurs for test gratings presented in the same plane as the adapting grating. Thus, the neural mechanisms adapted to the high contrast patterns must be processing disparity information.

3. The spatial frequency response of the disparity adaptation effect has been measured by adapting to gratings of different spatial frequencies presented at a given disparity, and comparing threshold elevations for identical test gratings presented in the same (disparate) plane as the adapting grating or in the plane of fixation.

4. The unbiased adaptation effect specific to disparity is greatest for gratings whose periods are twice the disparity.

5. There is no adaptation effect specific to disparity for individuals possessing only convergent or only divergent disparity mechanisms.

6. The results suggest that disparity mechanisms make bar by bar correlations as opposed to edge by edge correlations and that narrow bar detectors feed small disparity mechanisms whereas wide bar detectors feed large disparity mechanisms.
Spinal pathways projecting to the cerebral first somatosensory area in the monkey
Authors: Andersson Sven A. , Norrsell Kerstin , Norrsell Ulf
Published: December 2014

1. Potentials evoked with short latency in the cerebral post‐central gyrus after intradermal electrical, or adequate light tactile stimulation of the contralateral body half have been studied in the monkey, before and after transection of different spinal pathways at the upper cervical level.

2. Initially, positive potentials evoked by both types of stimulus were recorded after transection of the dorsal funiculi with the same somatotopic, topographical distribution as before the lesion.

3. The potentials recorded after transection of the dorsal funiculi could be evoked via one pathway located in the dorsal half of the lateral funiculus ipsilateral to the afferent input, and another pathway located, at least partially, in the ventral funiculus contralateral to the afferent input.

4. Of these two pathways, the crossed ventral pathway was found necessary to keep the topographical distribution of the evoked potentials unaltered.
Effect of prolonged ouabain treatment on Na, K, Cl and Ca concentration and fluxes in cultured human cells
Authors: Lamb J. F. , McCall D.
Published: December 2014

1. Girardi and Hela cells (derived from human heart and cervix respectively) were grown as monolayer cultures in B.M.E. (Eagles basal medium) containing concentrations of ouabain up to 5 × 10−8
M for periods ranging up to 5 days. The cell sizes, numbers, Na, K, Cl, and Ca concentrations and fluxes were then measured.

2. Twenty‐four hours incubation in ouabain concentrations equal to or less than 5 × 10−8
M caused a rise in [Na]i and an almost equal fall in [K]i to new steady levels. The concentrations so reached were linearly related to the ouabain concentrations, such that in 5 × 10−8
M ouabain [Na]i rose to 124 m‐mole/l. intracellular water and [K]i fell to 55 m‐mole/l. i.c. water in Girardi cells. In Hela cells the changes were smaller at any particular ouabain concentration. These levels were maintained constant for at least 5 days.

3. In cells in the logarithmic phase of growth, raising [Na]i and lowering [K]i by ouabain caused a slowing of growth rate proportional to the ouabain concentration used. In cells in the stationary phase there was no change in the cell numbers over 24 hr. The volume of the cells was not directly affected by the treatment.

4. Reducing [K]o from the normal value of 5·4 to 2·5 m
M increased the effect of any ouabain concentration, whereas increasing [K]o to 7·5 decreased the effect of ouabain.

5. Reduction of [K]o to 2·5 m
M had no effect on the [K]i or [Na]i but halved the cell numbers, probably by a reduction in the growth rate. The mechanism of this effect is obscure.

6. In Girardi cells raising [Na]i and lowering [K]i by prolonged treatment increases the total Na fluxes and decreases the total K fluxes but keeps the total Na + K flux constant. High‐Na, low‐K cells had a reduced Na:K exchange compared to fresh cells and also had a Na:K pumped ratio nearer 4:1 than the 3:2 normally found.

7. These cells also show ouabain‐sensitive and ouabain‐insensitive Na:Na exchanges. In high‐Na, low‐K cells the ouabain sensitive Na:Na exchange is the same as in fresh cells. The effect of treatment on the ouabain insensitive Na:Na exchanges has not been elucidated.

8. The Cl content and fluxes are not altered by prolonged ouabain treatment. From this it is inferred that the membrane potential in high‐Na, low‐K cells is the same as in normal cells.

9. High‐Na, low‐K cells have the same calcium content and fluxes as fresh cells. From this it is concluded that there is no Na:Ca coupling in these cells.
A sympathetic reflex elicited by distension of the mesenteric venous bed
Authors: Andrews C. J. H. , Andrews W. H. H. , Orbach J.
Published: December 2014

1. The proximal ends of the distal portions of severed nerves coming from the small intestine were monitored for nerve impulses. When the mesenteric venous pressure was increased by mechanical obstruction of the portal vein there was a proportional increase in the frequency of afferent action potentials, the frequency falling immediately the venous pressure was reduced. The stimulus for the increased rate of nerve discharge appeared to be pressure within the mesenteric venous bed and not anoxia, for obstruction of the arterial supply to the gastrointestinal tract did not activate the same fibres.

2. Obstruction of the portal vein led to an increased efferent nervous discharge to the intestines. The reflex increase persisted after bilateral vagotomy, after transection of the spinal cord at the level of C7 and after section of the hepatic nerves, but was abolished by section of the intestinal nerves.

3. It is suggested that the spinal reflex is concerned with local distribution of blood and that the mesenteric venous ‘volume’ or ‘stretch’ receptors which initiate the reflex are similar to those described elsewhere in the body.
Adaptation to square‐wave gratings: inhibition between spatial frequency channels in the human visual system
Authors: Tolhurst D. J.
Published: December 2014

1. The observation that the detection threshold for a square‐wave grating depends only on that of its fundamental was confirmed by showing that adapting to the fundamental spatial frequency caused elevation of the square‐wave threshold, to the same extent as the fundamental threshold was elevated by the same adapting pattern. Adapting to the third harmonic frequency had no effect on the square‐wave threshold.

2. Adapting to a square‐wave grating should elevate the thresholds for both the fundamental and third harmonic frequencies (Blakemore & Campbell, 1969), and the amount of elevation at each frequency should be predictable from the contrast of that frequency within the square‐wave.

3. It was found, however, that both the fundamental and third harmonic, when present in the square‐wave, were much less effective as suprathreshold adapting stimuli than would be predicted from their effects when viewed in isolation.

4. Adapting to a mixture of two sinusoidal gratings (with 3:1 frequency ratio) demonstrated that the fall in adapting power was not due to the higher harmonics of the square‐wave nor to nonlinearities in the stimulus display. Similar effects were found when the phase relations of the adapting gratings were changed, showing that the interaction is not a special property of square‐waves or of edges.

5. It is suggested that the spatial frequency channels subserving the fundamental and third harmonic frequencies inhibit each other when the patterns are some way suprathreshold. At or near threshold, there is no such reciprocal inhibition.
Synaptic actions of peripheral nerve impulses upon Deiters neurones via the mossy fibre afferents
Authors: Allen G. I. , Sabah N. H. , Toyama K.
Published: December 2014

1. The cerebellar integration of sensory inputs to Deiters neurones was investigated in decerebrate cats. In some preparations decerebration was combined with transection of the olivocerebellar fibres.

2. In the latter preparations peripheral nerve impulses generally produced a response consisting of a sequence of the following post‐synaptic potentials: (i) an initial e.p.s.p. (d1), (ii) early i.p.s.p. (h1), (iii) later i.p.s.p. (h2).

3. The mean latencies of d1, h1 and h2 were 5·7, 7·3 and 9·8 msec from the forelimb nerves, and 7·5, 9·0 and 13·4 msec from the hind limb nerves, respectively.

4. The stimulus intensity—response relation indicates that the Group I muscle afferents as well as the low threshold cutaneous afferents contribute to the response.

5. In the preparations with the intact inferior olive there were additional components of the post‐synaptic potentials: a later e.p.s.p. (d2) and another later i.p.s.p. (h3), their mean latencies being 15·3 and 19·7 msec from the forelimb nerves, and 18·0 and 21·3 msec from the hind limb nerves, respectively.

6. The d1 and h2 components were attributed to the mossy fibre afferents and d2 and h3 to the climbing fibres; d1 and d2 were due to excitation through the collaterals of the mossy and climbing fibres, and h2 and h3 to inhibition from Purkyně cells activated by the mossy and climbing fibres, respectively. h1 was too early to be produced through the cerebellum, and was probably mediated by inhibitory neurones in the reticular formation.
Calcium‐dependent amylase release and electrophysiological measurements in cells of the pancreas
Authors: Kanno T.
Published: December 2014

1. Transmembrane potential, effective membrane resistance, and amylase output were recorded from acinar cells of rat pancreas perfused in vitro.

2. Both pancreozymin and acetylcholine hyperpolarized the acinar cells, increased effective membrane resistance, and augmented amylase output.

3. The omission of calcium from the perfusion medium increased effective membrane resistance and potential, and abolished the increase in amylase output in response to the drugs.

4. A quantitative relation was found between the amount of amylase released by pancreozymin and the concentration of calcium in the perfusion medium at values below the normal 2·5 mM calcium. Excess magnesium did not inhibit the increase in amylase output in response to the drug.

5. It is concluded that the release of amylase from the pancreas depends on the entry of calcium into the acinar cells. The entry of calcium seems to be mediated by a carrier in the membrane and may be considered as a ‘facilitated diffusion’.

6. The electrophysiological findings taken together with morphological evidence provided by scanning electron microscopy favour the view that pancreatic zymogens are released from the granules in the acinar cells to the lumen by the process known as exocytosis.
Facilitation and inhibition of cell groups within the superior cervical ganglion of the rabbit
Authors: Brimble M. J. , Wallis D. I. , Woodward B.
Published: December 2014

1. The patterns of facilitation and inhibition of the Sa and Sb components of the post‐ganglionic compound action potential after a single conditioning stimulus were different and dependent on stimulus parameters.

2. With submaximal conditioning and test stimuli, the Sa component showed a phase of early facilitation (40–75 msec after the conditioning stimulus) followed by a prolonged tail of facilitation. With maximal stimuli, early facilitation and late facilitation (700–2000 msec after the conditioning stimulus) were separated by a phase of inhibition or relative inhibition, most pronounced 100–300 msec after the conditioning stimulus.

3. During early facilitation, a submaximal Sa response was facilitated by 33·1 ± 3·9%, while a maximal Sa response was facilitated by 14·5 ± 2·9%.

4. Providing preganglionic C fibres were excited, facilitation of the Sb component remained relatively constant for 40–500 msec after the conditioning stimulus, with no phase of inhibition.

5. Early facilitation of submaximal Sa responses was greatest when the conditioning stimulus excited about 50% of the preganglionic B fibres, but that of maximal responses was greatest when the conditioning stimulus excited all the B fibres. The preganglionic C fibres modulated facilitation of the Sa component. Maximal facilitation of this component was associated with depression of the Sb component.

6. Submaximal Sa responses are more strongly inhibited than maximal Sa responses 200 msec after a conditioning stimulus. The C fibre pathway seems able to modulate the degree of inhibition of the Sa ganglion cells.

7. A neuronal model with divergent and convergent preganglionic B and C fibres supplying Sa ganglion cells is consistent with the results. The preganglionic input is able to vary the size of the subliminal fringe. The Sb component is in part due to the Sa ganglion cells firing to their C fibre input.
Internodal conduction in undissected demyelinated nerve fibres
Authors: Rasminsky M. , Sears T. A.
Published: December 2014

1. A new method is described for recording external longitudinal currents from single undissected nerve fibres in rat ventral roots. The method permits identification of the sites of fifteen or more successive nodes of Ranvier in a given single fibre and the measurement of internodal conduction times between them.

2. Average internodal conduction time for normal ventral root fibres of internodal length between 0·75 and 1·45 mm is 19·7 ± 4·6 (
S.D.) μsec at 37° C. Internodal conduction time appeared to show a minimum for fibres of internodal length 1·0 mm.

3. Ventral roots were demyelinated by focal application of diphtheria toxin. Although conduction is markedly slowed in demyelinated fibres, sites of inward membrane current remain spatially separated indicating that conduction remains saltatory to the point of conduction block rather than becoming continuous as in unmyelinated fibres.

4. Slowing of conduction appears to be due to changes in the passive electrical properties of the internodal myelin. Evidence is presented suggesting that there is an increase in internodal capacitance and a decrease in internodal transverse resistance at internodes of demyelinated fibres; such changes would have the effect of delaying excitation at the nodes. The changes in passive electrical properties, which appear to be primarily in the vicinity of the nodes, would be consistent with the pathological changes observed in demyelinated fibres.

5. Internodal conduction times in demyelinated fibres have ranged from normal (26 μsec at 30° C) to more than 600 μsec. There is a great variation in internodal conduction time at successive internodes of a given single fibre; this presumably reflects the varying severity of demyelination of successive internodes.

6. As in normal fibres, nodes of demyelinated fibres generate less current when excited by the second of two closely spaced impulses. This results in an increased internodal conduction time for the second impulse and, at a critically short interstimulus interval, conduction block of the second impulse.

7. The increased refractory period of transmission of internodes with increased internodal conduction times is a consequence of the decreased ability of such internodes to sustain propagation in the face of small decreases in nodal current.

8. During tetanic stimulation, increases in internodal conduction time are associated with corresponding decreases in nodal current generated by the node proximal to the internode in question.

9. It is suggested that changes in the magnitude of the nodal current during repetitive activity are due to changes in transmembrane concentration gradients of sodium, the increased internodal conduction time and eventual conduction block during tetanic stimulation being caused by intracellular sodium accumulation.

10. Intracellular sodium accumulation is also offered as the explanation for the post‐tetanic depression seen in demyelinated fibres.
Hypomagnesaemia following theophylline or furosemide injection in ewes: renal versus extrarenal effect
Authors: Larvor P. , Rayssiguier Y.
Published: December 2014

1. Intravenous theophylline infusion (30 mg/kg body weight during 90 min) induces in normal ewes a magnesuria associated with hypomagnesaemia.

Intravenous furosemide infusion (1 mg/kg body weight during 90 min) induces in the same animals a similar magnesuria with only a slight hypomagnesaemia.

2. In magnesium deficient ewes, theophylline induces a hypomagnesaemia, without a significant rise in magnesuria.

3. Theophylline infusion, with simultaneous reinjection of the excess magnesium excreted in urine, induces a significant hypomagnesaemia.

4. Thyroidectomy does not inhibit the effect of theophylline on magnesaemia.

5. It is concluded that the effect of theophylline on magnesaemia is mainly of extrarenal origin, while the effect of furosemide is only renal. The effect of theophylline is not mediated through calcitonin secretion.
Intrahepatic distribution of portal and hepatic arterial blood flows in anaesthetized cats and dogs and the effects of portal occlusion, raised venous pressure and histamine
Authors: Greenway C. V. , Oshiro G.
Published: December 2014

1. Radioactive microspheres were used to determine the distribution of arterial and portal flows within the liver. 141Ce‐microspheres and 51Cr‐spheres were given to allow two determinations of flow distribution in each animal and experiments are described to establish the accuracy and validity of the method.

2. Mean flow/g to any lobe or segment of a lobe in a group of animals was not markedly different from the mean flow/g to the whole liver, and in general the liver was homogeneously perfused with both portal and arterial blood. However, in any one liver, some areas received a relatively greater flow (up to 300%) and some a relatively smaller flow (down to 50%) at the time the microspheres were given. The gall bladder received a much smaller portal flow/g than the parenchyma but its arterial flow/g varied widely in different animals.

3. If portal flow to an area of parenchyma was reduced by occlusion of a branch of the portal vein, this area received a significantly increased arterial flow.

4. An increase in hepatic venous pressure did not cause a significant change in the intrahepatic distribution of either arterial or portal flows in cats.

5. In dogs, infusions of histamine into the portal vein caused a redistribution of portal flow away from the free ends of the lobes towards the hilar ends but the distribution between lobes did not change and there was no redistribution of arterial flow.
Quantal independence and uniformity of presynaptic release kinetics at the frog neuromuscular junction
Authors: Barrett Ellen F. , Stevens C. F.
Published: December 2014

1. Amplitude and latency fluctuations of the end‐plate potential at the frog neuromuscular junction were studied simultaneously at low temperatures, using intracellular or focal extracellular recording techniques and average quantal contents between 0·5 and 3.

2. At the release rates studied, the evoked release of one quantum has in most cases no significant effect on the probability of subsequent quantal release to the same stimulus, confirming the mutual independence of quantal releases in this preparation.

3. An equation derived from Poisson's law was applied to a histogram of the latencies of the first quantum released on each of a series of trials, to predict the average quantal content of end‐plate responses originating at various times after nerve stimulation. The shape of the predicted time distribution of quantal contents usually agreed closely with that of the experimentally observed time distribution of end‐plate response amplitudes. This agreement demonstrates that both the amplitude and the latency fluctuations of the end‐plate response result from one presynaptic stochastic process that is uniform in magnitude and time course after each stimulus.

4. Analysis of extracellular records from synaptic regions with a history of extensive activity often suggested the existence of depressive interaction among quantal releases, perhaps caused by depletion of the supply of releasable quanta.
On the mechanism of barbiturate anaesthesia
Authors: Richards C. D.
Published: December 2014

1. The effects of pentobarbitone (0·05–0·6 m
M in saline solution) on the evoked field potentials of in vitro preparations of guinea‐pig olfactory cortex were studied.

2. The evoked field potentials comprised an initial diphasic wave — the lateral olfactory tract (l.o.t.) compound action potential — followed by a surface negative wave (e.p.s.p) of 1–3 mV amplitude and about 10 msec duration. Superimposed on the negative wave were a number of positive peaks (population spikes).

3. Pentobarbitone depressed the e.p.s.p. but not the l.o.t. compound action potential. The number and size of the population spikes were progressively reduced as the e.p.s.p. became depressed, indicating a failure of transmission through the cortical relay. The e.p.s.p. depression increased with increasing concentrations of pentobarbitone.

4. Pentobarbitone had no effect on the threshold to electrical stimulation of the l.o.t. fibres or on that of the post‐synaptic cells to synaptic excitation.

5. Post‐tetanic potentiation and frequency potentiation were either of normal magnitude or were enhanced in the presence of 0·2–0·3 m
M pentobarbitone.

6. It is concluded that pentobarbitone probably reduces the output of transmitter from the presynaptic nerve terminals of the olfactory cortex and that this mechanism could be the basis of the depressant action of the barbiturates.
The effect of stretching the superior vena caval—right atrial junction on right atrial receptors in the dog
Authors: Kappagoda C. T. , Linden R. J. , Snow H. M.
Published: December 2014

1. Action potentials were recorded from fibres in the right cervical vagus, the receptor endings of which were localized to the endocardial surface of the superior vena caval—right atrial junction.

2. Stretching the junction between the superior vena cava and the right atrium without obstructing venous return caused an increase in the discharge of these fibres. This increase in impulse frequency was similar to that caused by small changes in mean right atrial pressure (range 0–13·5 cm H2O).

3. This evidence supports the earlier suggestion that stimulation of the right atrial receptors by stretching the superior vena caval—right atrial junction causes a reflex increase in heart rate.
Compensatory renal growth after unilateral nephrectomy in the new‐born rat
Authors: Dicker S. E. , Shirley D. G.
Published: December 2014

1. The right kidney in a series of control rats aged between 5 days and 115 days was weighed. The kidney weight/body weight ratio was greater in young than in older rats, but decreased linearly with increasing age.

2. After unilateral nephrectomy of rats 5 days old, the remaining kidney underwent compensatory growth. The rate and extent of this growth were greater than in adult rats.

3. The concentrations of RNA and DNA in the renal cortex and medulla of rats 5 days old were higher than in adult animals. The concentrations of the two nucleic acids fell with age, and reached adult levels after approximately 6 weeks.

4. After unilateral nephrectomy of rats 5 days old, the concentrations of RNA and DNA in the medulla were not significantly different from those in control animals. In the cortex, however, there was a delayed increase in the RNA/DNA ratio, which reached a level some 12% higher than that in control rats. This increase was smaller than that observed in unilaterally nephrectomized adult rats.

5. The cortical QO2 of the remaining kidney of unilaterally nephrectomized new‐born rats was elevated by some 20% within 1 day of unilateral nephrectomy. Cortical QO2's remained higher than those of control animals for 3–4 weeks.

6. Since after unilateral nephrectomy, the increase in renal mass in new‐borns was greater than that in adults, whereas the degree of cortical cellular hypertrophy (as estimated by the RNA/DNA ratio) was smaller than in adults, it is likely that in new‐born animals a significant contribution to compensatory growth comes from cellular hyperplasia.
Delayed release of transmitter at the frog neuromuscular junction
Authors: Rahamimoff R. , Yaari Y.
Published: December 2014

1. After the end‐plate potential (e.p.p.) there is an increase in the frequency of the miniature e.p.p.s. This delayed release of transmitter was studied at the frog neuromuscular junction, using conventional intracellular and extracellular recording techniques. E.p.p. amplitude was kept subthreshold by subnormal concentrations of activating divalent ions.

2. The ratio delayed release: initial release had values between 2 and 140%, depending on the experimental conditions; it decreased with an increase in Ca concentration and quantal content.

3. Delayed release is larger at low temperature than at room temperature.

4. Delayed release is statistically independent of the amplitude of the preceding e.p.p.

5. The time course of the decay of the delayed release is monotonic when strontium is the activating divalent ion; it shows a ‘dip’ in more than 50% of the cases when Ca activated release.

6. The results were discussed in terms of the residual Ca ion hypothesis.
Cutaneous convergence on to the climbing fibre input to cerebellar Purkyně cells
Authors: Leicht Rolf , Rowe Mark J. , Schmidt Robert F.
Published: December 2014

1. In cats anaesthetized with Nembutal, the cutaneous receptive fields of individual cerebellar climbing fibres were assessed by recording the climbing fibre responses of single Purkyně cells following controlled mechanical stimulation (air jets, vibration, taps, pressure) of the foot pads of all four limbs and of the hairy skin of the limbs and the body.

2. Three major types of cutaneous receptive fields of individual climbing fibres were recognized: (a) restricted fields generally confined to the distal areas of one limb only; (b) circumscribed fields on the distal areas of two to four limbs (discontinuous fields); and (c) widespread continuous fields extending over all or almost all of the body surface. A fourth group appears to receive cutaneous inputs from one limb and sensory input from deeper structures in other limbs.

3. Thresholds for tapping of the foot pads were often quite low (< 100 μm indentation), and there was no noticeable difference in the distribution of thresholds between the climbing fibres having restricted or more widespread cutaneous receptive fields. Similarly, the latencies of climbing fibre responses evoked by vibration and tapping were in the same ranges for climbing fibres with receptive fields restricted to one limb only and for those having more widespread fields.

4. In regard to location in the anterior lobe of the cerebellum it was found that those climbing fibres receiving inputs only from the ipsilateral forelimb projected to Purkyně cells located almost entirely in lobule V, whereas all other climbing fibres with restricted or more widespread receptive fields projected to Purkyně cells distributed widely within lobules II to V.
Thresholds of cortical activation of baboon α‐ and γ‐motoneurones during halothane anaesthesia
Authors: Koeze T. H.
Published: December 2014

1. In the halothane anaesthetized baboon the threshold for cortically elicited primary and secondary spindle afferent discharge was compared to the threshold at the ‘best point’ for a cortically elicited tibialis anticus tension change.

2. The cortical threshold for eliciting a tension change was greater than the cortical threshold for eliciting spindle afferent discharge for some afferents and less for other afferents.

3. The pattern of cortically elicited spindle afferent discharge during muscle stretch suggested static γ‐motoneurone activation. No convincing evidence of dynamic γ‐motoneurone activation was seen.

4. Inhibition of spindle afferent discharge was occasionally found and the ‘best point’ was the same as the cortical ‘best point’ for eliciting monosynaptic α‐motoneurone activity. This result suggested that the cortical projections which inhibit the pre‐existent activity of static γ‐motoneurones are in a close anatomical relation to those cortical projections which elicit activity of α‐ and static γ‐motoneurones.
The effect of lecithin on intestinal cholesterol uptake by rat intestine in vitro
Authors: Rampone Alfred J.
Published: December 2014

1. Sacs 20 cm long were obtained from the upper half of the small intestine of bile fistula rats (bile duct cannulated 48 hours previously). The sacs were everted, filled with oxygenated phosphate buffer and incubated 1 hr at 37° C in 25 ml. of a buffered micellar solution of oleic acid (0·6 m
M), mono‐olein (0·3 m
M), sodium taurocholate (4·8 m
M) and 3H‐labelled cholesterol (0·15 m
M) plus glucose (28 m
M).

2. After incubation the amount of [3H]cholesterol taken up by the mucosal tissue was measured. It averaged 200 n‐mole/hr.g tissue wet wt. ± 6 (
S.E.).

3. Adding 3 ml. whole rate bile with other factors unchanged caused cholesterol uptake to decrease by 50% in confirmation of previous studies.

4. Adding purified lecithin obtained from rat liver tissue, and from egg yolks, similarly decreased cholesterol uptake. A significant response was obtained with 2·5 mg liver lecithin (concentration 0·13 m
M) and a near maximum response with 15 mg (concentration 0·80 m
M). 10 mg lecithin decreased uptake by an amount equivalent to that obtained with 3 ml. whole bile.

5. Lecithin is an active component of whole bile causing reduced intestinal cholesterol uptake from micelles.

6. The decreased uptake of cholesterol in the presence of lecithin may have been the result of expansion of the cholesterol‐containing micelles with consequent reduction in cholesterol permeability.
The effect of adrenalectomy or pharmacological inhibition of adrenocortical function on macromolecule uptake by the new‐born rat intestine
Authors: Daniels V. G. , Hardy R. N. , Malinowska K. W.
Published: December 2014

1. Bilateral adrenalectomy in 18‐day‐old rats resulted in an extension by approximately 4 days of the period during which the villous epithelial cells of the small intestine took up polyvinyl pyrrolidone (PVP) of mean mol. wt. 160,000.

2. The eventual termination of PVP uptake (‘closure’) closely resembled normal closure in control animals: the time course of the decline in uptake and the histological changes indicated that more mature ‘PVP‐impermeable’ cells progressively ascended the villi.

3. Injection of Metopirone was ineffective in animals 10 days after birth, but when injected after day 13 caused closure within 3 days.

4. Metopirone injection significantly reduced the plasma concentration of corticosterone and caused a marked rise in the plasma concentration of deoxycorticosterone.

5. Aminoglutethimide injection also produced precocious closure and had an effect similar to Metopirone on the plasma concentrations of corticosterone and deoxycorticosterone.

6. Injection of Metopirone or aminoglutethimide increased the relative adrenal weight compared with control animals. Aminoglutethimide was more effective and caused approximately a 100% increase in adrenal weight.
Thermoregulatory changes induced during heat acclimatization by controlled hyperthermia in man
Authors: Henane R. , Valatx J. L.
Published: December 2014

1. Heat acclimatization has been carried out by a controlled hyperthermia procedure, and induced thermoregulatory changes have been investigated for nine fit young men.

2. During the experiments two types of thermal responses became apparent. The subjects tolerating the rise in the central temperature during hyperthermia displayed a marked improvement of their sweating capacity and their sweating performances, and a parallel shift towards lower body temperatures of the curves relating sweat rate to tympanic, rectal and mean skin temperatures.

3. This shift occurred without any change in the slope, that is without any change in the gain of the central control system. It was accompanied by a concomitant shift of the threshold of sweating onset, so that for a given central temperature there was a higher sweat rate following treatment.

4. The sweat decline appeared late in tolerant subjects. This decline was early in the intolerant subjects and appeared as early as the first day of heat treatment. Moreover, these subjects displayed no increase of sweat output with repeated sessions of heat treatment.

5. The core—periphery temperature gradient measured during the cooling stage did not change in the tolerant subjects when acclimatization had developed. This gradient increased in the intolerant subjects because deep temperature decreased slowly whilst skin temperature decreased rapidly. The core of intolerant subjects retained the stored heat and dissipated it slowly. The tolerant subjects seemed on the contrary to display in the same conditions increased tissue conductance enabling rapid dissipation of the stored heat.
Electrophysiology of cardiac function in teleosts: cholinergically mediated inhibition and rebound excitation
Authors: Cobb J. L. S. , Santer R. M.
Published: December 2014

1. A study has been made on the responses of the plaice (Pleuronectes platessa) heart, isolated and in situ to differential vagal stimulation using intra‐ and extracellular recording electrodes. The effects of direct application of acetylcholine and catecholamines and their respective blocking agents are also reported.

2. Vagal stimulation at 7 Hz totally inhibits heart beat whilst stimulation at 2–3 Hz accelerates it. Both these effects are blocked by atropine (10−6 g/ml.). Bretylium (10−5 g/ml.) and pronethalol (10−6 g/ml.) have no effect upon either response to vagal stimulation.

3. On cessation of prolonged inhibitory vagal stimulation there is a marked increase in the heart rate, and in quiescent hearts one or two beats are initiated after stimulation.

4. Vagal stimulation gives rise to a hyperpolarization in atrial cells. It is proposed that all the excitatory effects of vagal stimulation are due to rebound excitation from an inhibitory hyperpolarization. At high frequencies the hyperpolarizations summate to give rise to total inhibition. At lower frequencies of stimulation the heart beat is increased to rates dependent on interaction between the time course of the hyperpolarization and the refractory period of the heart. Both effects are cholinergically mediated.

5. The rebound excitation in response to vagal stimulation (post‐vagal tachycardia) persists in response to stimulation of the atrial myocardium in the presence of atropine (10−6 g/ml.) and bretylium (10−5 g/ml.). It is therefore suggested that this is a response of the muscle cell membrane to vagal stimulation and is not nerve‐mediated.
Spontaneous salivation in the rabbit submandibular gland
Authors: Smaje L. H.
Published: December 2014

1. Salivation has been studied in the submandibular gland of the rabbit. A very slow spontaneous salivation took place when all possibility of nerve influence had been excluded. Salivation was not due to ultrafiltration.

2. The ‘spontaneous’ saliva had a mean K concentration of 148 m
M and Na concentration of 46 m
M. With increasing salivation rate produced by parasympathetic nerve stimulation, K concentration fell to a plateau level of about 30 m
M whilst Na concentration fell rapidly to reach the low value of 3 m
M, then began to rise again at the higher flow rates.

3. Ligation of the submandibular duct produced a reversal of the ion concentrations in spontaneous saliva. By 4 days K concentration was lower and that of Na higher than control values until by 2 weeks the effect was maximal with mean concentrations of 25 m
M for K and 153 m
M for Na.

4. Ouabain increased the spontaneous salivation rate and ethacrynic acid slowed or prevented it altogether. On the basis of the known sites of action of these drugs it is postulated that two pumps are involved in the regulation of spontaneous salivation. There appears to be basal activity of an acinar mechanism pumping NaCl into the lumen, taking water with it. This pump is activated directly or indirectly by the intracellular Na concentration which itself is controlled by an Na—K exchange pump.

5. Excitation of the sympathetic trunk produced a small, though definite, increase in salivation rate. There was evidence that myoepithelial cells might also be involved in the sympathetic response and that they were activated by α receptor stimulation. Salivation evoked by sympathetic nerve stimulation would seem to be a response to β receptor stimulation, but the possibility that activation of both α and β receptors was required could not be excluded entirely.
The interaction of sodium and potassium with the sodium pump in red cells
Authors: Garay R. P. , Garrahan P. J.
Published: December 2014

1. At high internal K concentrations the efflux of Na from red cells increases with internal Na concentration following an S‐shaped curve. As internal K is reduced the S‐shaped region and the value of internal Na for which the Na efflux is half‐maximal are both shifted progressively towards zero.

2. The effects of internal Na on the shape of the Na efflux curves can be quantitatively accounted for if it is assumed that the rate of Na efflux is linearly related to the number of pump units having three identical and non‐interacting sites occupied by Na.

3. The effects of internal K on the shape of the Na efflux curves are fully explained if it is assumed that the inner sites for Na of the Na pump also behave as identical and non‐interacting sites for internal K, being the K‐carrier complexes unable to promote Na translocation. The apparent affinity of the Na pump for internal K is about 50 times less than for internal Na.

4. Internal K not only alters the apparent affinity of the Na pump for Na, but also affects its turnover rate. The turnover rate of Na: K exchange increases with internal K following a curve which saturates at about 30 m
M internal K. The turnover rate for Na:Na exchange increases linearly with internal K.

5. The linear dependence of the rate of Na:Na exchange on internal K explains why, when internal Na is increased at the expense of internal K, the rate of Na:Na exchange progressively decreases after passing through a maximum.

6. The effects of external Na on the rate of Na:Na exchange can be satisfactorily explained assuming that they are due to the occupation by external Na of three identical and non‐interacting sites on each pump unit. The apparent affinity of the Na pump for external Na is about 160 times less than the apparent affinity for internal Na.

7. Under all the experimental conditions tested, it was found that the relation between flux and cation concentration at one of the surfaces of the cell membrane is altered only by a constant factor by changes in the cation composition at the opposite surface of the cell membrane. This fact strongly suggests that there are no interactions between the inner and outer sites of the Na pump.

8. The effects of inner and outer cations on both the Na:K and the Na:Na exchanges catalysed by the Na pump suggest that cation fluxes are proportional to the number of pump units having its inner and outer sites simultaneously occupied by the relevant cations. It seems therefore that sequential models for ion transort do not provide an adequate description of the molecular mechanism of active transport in red cells.
The effects of lung reflexes on laryngeal resistance and motoneurone discharge
Authors: Stransky A. , Szereda‐Przestaszewska Małgorzata , Widdicombe J. G.
Published: December 2014

1. The reflex action of stimulation of alveolar J–receptors and of airway epithelial irritant receptors has been investigated on laryngeal resistance to airflow and on laryngeal motoneurone discharge in cats and rabbits.

2. Resistance to airflow of the innervated larynx was measured (1) with the larynx isolated in situ with constant flow from the trachea to a pharyngeal opening; and (2) with the animal breathing through the larynx and the pharyngeal opening. With both methods resistance was determined from the relationship between translaryngeal pressure and airflow.

3. In control conditions the laryngeal resistance was about one tenth of total lung resistance.

4.
I.V. injections of phenyl diguanide (to stimulate J‐receptors) caused apnoea and complete closure of the larynx, followed by rapid shallow breathing with expiratory constrictions of the larynx. Expiratory laryngeal motoneurones were strongly stimulated.

5. The laryngeal responses to phenyl diguanide were nearly abolished by bilateral vagotomy in the chest (below the origin of the recurrent laryngeal nerves), and were absent on injection of the drug into the left atrium; the motoneurone responses were abolished by vagotomy and lessened by paralysis and artificial ventilation.

6.
I.V. injections of histamine acid phosphate or inhalation of an aerosol of the drug in solution (to stimulate lung irritant receptors) caused tachypnoea and expiratory constrictions of the larynx, and increased discharges in expiratory laryngeal motoneurones.

7. The laryngeal responses to histamine were more than halved by bilateral intrathoracic vagotomy.

8. Phenyl diguanide and histamine increased the frequency of the discharge of inspiratory laryngeal motoneurones, but reduced the number of impulses per inspiratory phase. Laryngeal resistance in inspiration was usually increased.
Phosphate excretion in the laying hen (Gallus domesticus)
Authors: Martindale L.
Published: December 2014

1. The excretion of phosphate during the calcifying and non‐calcifying phases of egg formation was studied.

2. The pattern of phosphate excretion was observed during increasing body loads of phosphate.

3. A tubular mechanism for phosphate excretion is proposed in which tubular phosphate secretion occurs proximal to, or coincidental with reabsorption.

4. Parathyroid extract increased the rate of phosphate excretion and appeared to inhibit both the reabsorptive and secretory mechanisms.

5. The pattern of excretion of phosphate loads by hens in the calcifying phase was closely similar to that of birds in the non‐calcifying phase when treated with parathyroid extract.

6. The relationship between shell calcification and the parathyroids is discussed.
Psychophysical evidence for sustained and transient detectors in human vision
Authors: Kulikowski J. J. , Tolhurst D. J.
Published: December 2014

1. The sensitivity to temporally modulated sinusoidal gratings was determined. Two thresholds could be distinguished for the modulated gratings: the contrast at which flicker could be perceived and the contrast at which the spatial structure became distinct.

2. The flicker detection thresholds and pattern recognition threshold varied independently as functions of the spatial and temporal frequencies, suggesting that the two thresholds represent the activity of two independent systems of channels.

3. The channels detecting flicker prefer low and medium spatial frequencies. They have a pronounced decline in sensitivity at low temporal frequencies of sinusoidal modulation. They respond twice as well to gratings whose phase is alternated repetitively as to gratings turned on and off at the same rate.

4. The channels responsible for the discrimination of spatial structure are most responsive at high and medium spatial frequencies. There is no decline in sensitivity at low temporal frequencies. These channels respond equally well to alternating and on/off gratings up to about 8 Hz.

5. The temporal properties as revealed with sinusoidal modulation, suggest that the flicker‐detecting channels would give transient responses to prolonged presentation of stimuli: the channels responsible for analysing the spatial structure would give sustained responses. The responses of the two types of channel to alternating and on/off gratings confirm this suggestion.
Potassium accumulation in smooth muscle and associated ultrastructural changes
Authors: Jones A. W. , Somlyo A. P. , Somlyo Avril V.
Published: December 2014

1. The water content, extracellular (60CoEDTA) space, ionic composition and ultrastructure of several mammalian smooth muscles were studied after incubation in solutions of varying ionic compositions and osmolarities.

2. Substitution of KCl for NaCl resulted in an increase in cell water, K and Cl, accompanied by little change in total wet weight. This was due to a reduction in the extracellular space.

3. Changes in extracellular osmolarity produced a wider range of cell volumes in high KCl solutions than in Krebs. The addition of 29–58 m
M sucrose to high KCl prevented the swelling.

4. Electron microscopy of smooth muscle swollen in high KCl solution revealed light (less electron opaque than normal) fibres of increased diameter, reduction in extracellular space, and nuclear swelling. The normal thick filament lattice was destroyed in swollen, osmium‐fixed smooth muscles.

5. The ultrastructural changes ascribed to swelling were absent in smooth muscles, (a) depolarized in high K2SO4 solutions, (b) in high KCl solutions with 29–58 m
M sucrose, and (c) returned to normal Krebs solution for recovery from swelling.

6. Smooth muscles incubated in high KCl (swollen) and high K2SO4 (unswollen) exhibited similar contractile responses, suggesting the filament lattice was intact until fixation, and that the contractile mechanism can operate over a relatively wide range of actin to myosin separations.

7. Shrinkage of smooth muscles in high KCl solutions made hypertonic with the addition of 10% sucrose was accompanied by an aggregation of the thick filaments.

8. The cell water of fixed taenia coli was reduced (a) by incubation in hypertonic solution followed by fixation in normal glutaraldehyde, or (b) by fixation of normal tissue in hypertonic glutaraldehyde. Osmotic responses during aldehyde fixation may be a source of artifact in the visualization of the normal filament lattice.
Active transport of 131I across the blood—brain barrier
Authors: Davson Hugh , Hollingsworth Jillian R.
Published: December 2014

The ventricular space of rabbits was perfused with a low‐viscosity silicone oil for the purpose of (1) collecting freshly secreted cerebrospinal fluid (c.s.f.) uninfluenced by diffusional exchanges with the brain and (2) studying passage of solutes from the blood into the brain, uncomplicated by exchanges with c.s.f. The freshly secreted c.s.f. appeared as fine droplets suspended in the less dense silicone, and accumulated at the bottom of the collected silicone. Studies on the penetration of 24Na from blood into this fluid indicated that considerable exchanges with the brain had occurred between its secretion and collection, in spite of this method of collection.

The second objective was attained, in that the exchanges between the freshly secreted fluid and the brain were quantitatively insufficient to affect the measure of kinetics of uptake by brain from the blood. In consequence, it was possible to demonstrate unequivocally that the increased uptake by brain of 131I, when treated with perchlorate, was due to inhibition of an active process occurring across the blood—brain barrier.

Other studies, involving ventriculo‐cisternal perfusion with artificial c.s.f., lent further support to this concept. 131I distribution is some 32% of the brain weight, a figure close to the ‘chloride‐space’.