bluuebunny/crossref_metadata_2025_split huggingface dataset:
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’.
On the mechanism of halothane anaesthesia
Authors: Richards C. D. 
Published: December 2014

1. The effects of halothane on the evoked potentials of in vitro preparations of guinea‐pig olfactory cortex were studied.2. The evoked potentials recorded from the cortical surface comprised an initial diphasic wave — the lateral olfactory tract (l.o.t.) compound action potential — followed by a negative wave of 1–3 mV amplitude and about 10 msec duration. Superimposed on the negative wave was a number of positive peaks. The negative wave has been identified as an extracellularly recorded, monosynaptic, excitatory post‐synaptic potential (e.p.s.p.) and the positive peaks have been shown to reflect the discharge of the cortical cell population in response to the evoked e.p.s.p. and are therefore termed ‘population spikes’.3. When halothane (0·4–1·5%) was added to the gas stream that superfused the surface of the preparation the evoked e.p.s.p.s became smaller in amplitude and the size of the population spikes diminished. The l.o.t. compound action potential was unaffected by these levels of halothane. Higher levels of halothane (above 2%) further reduced the amplitude of the evoked e.p.s.p.s, abolished the population spikes, decreased the amplitude of the l.o.t. compound action potential and slowed its time course. The effects of halothane on the evoked potentials were dose‐related and were independent (after the first 10 min of treatment) of the duration of the exposure to halothane.4. The decrease in the size of the population spike caused by the exposure to halothane implied that transmission through the cortical relay had been impaired. This was also shown by the decrease in the evoked activity of units in the prepiriform cortex. Of eleven units, eight were depressed by halothane (0·5–1·5%) two were unaffected and one showed a transient increase in the number of spikes generated in response to a l.o.t. volley.5. Halothane (up to 1·5%) had no effect on the threshold of the l.o.t. fibres to electrical stimulation or on that of the post‐synaptic cells to synaptic excitation.6. Post‐tetanic potentiation and frequency potentiation of the evoked e.p.s.p.s were enhanced in the presence of 1% halothane.7. It is concluded that halothane reduces excitatory synaptic transmission not by an increase in the electrical threshold of the post‐synaptic cells to synaptic excitation but by interference with the process of chemical transmission either by reducing the output of transmitter from the pre‐synaptic nerve terminal or by reducing the sensitivity of the post‐synaptic membrane to the released transmitter substance.
Retention of the original topographic polarity by the 180° rotated tectal reimplant in young adult goldfish
Authors: Yoon Myong G. 
Published: December 2014

1. The pattern of visual projection from the retina on to the optic tectum was studied with neurophysiological mapping methods following reimplantation of the optic tectum in young adult goldfish.2. When a rectangular piece of the tectum was dissected out and then reimplanted to the same tectum in situ, the restored visual projection showed a normal retinotopic order over the area of the tectal reimplant.3. If the tectal tissue was reimplanted after rotation by 180°, the visual projection from that part of the retina which innervated the 180° rotated tectal reimplant was found to be organized in a completely reverse retinotopic order within the reimplanted area in contrast to the normal projection from the other part of the retina on to the intact surrounding area of the same optic tectum.4. The results indicate that a piece of reimplanted tectal tissue retains its original topographic polarity regardless of whether the tectal tissue was rotated or not.5. The retention of original topographic polarity by a small fraction of the tectal tissue suggests that the optic tectum is not a passive receiver of incoming optic fibres but an active accommodator which selects appropriate optic fibres to make proper synaptic connexions in a consistent topographic order.
Effect of pyrogen and antipyretics on prostaglandin activity in cisternal c.s.f. of unanaesthetized cats
Authors: Feldberg W. , Gupta K. P. , Milton A. S. , Wendlandt Sabine 
Published: December 2014

1. Samples of cisternal cerebrospinal fluid (c.s.f.) were collected from unanaesthetized cats while rectal temperature was continuously recorded. From the same cat, samples were collected during normal body temperature, during pyrogen fever and when the fever was brought down by an
I.P. injection of an antipyretic. Fever was produced by injection of the bacterial pyrogen of Shigella dysenteriae either into the third ventricle, cisterna magna or
I.V. The samples of c.s.f. were assayed for PGE1‐like activity on the rat stomach fundus strip preparation rendered insensitive to 5‐HT.2. In samples of c.s.f. collected during normal body temperature, usually either no PGE1‐like activity was detected, or its activity was low. Higher values were obtained in only a few cats.3. In each experiment the PGE1‐like activity increased, often many‐fold, in samples collected during the pyrogen fever, irrespective, of the route of administration of the pyrogen. However, on
I.V. injection, about 1000 times larger doses of the pyrogen were required than on injection into the liquor space to produce fever and the increase in PGE1‐like activity of cisternal c.s.f.4. The antipyretic drugs indomethacin, paracetamol and aspirin, injected
I.P. during the pyrogen fever, brought down temperature, and the PGE1‐like activity of the cisternal c.s.f. again became low.5. When samples of cisternal c.s.f. were subjected to thin layer chromatography the prostaglandin‐like activity was solely or mainly found in the zone corresponding to the prostaglandins of the E series.6. These findings support the theory that pyrogens produce fever by increasing synthesis and release of prostaglandin in the preoptic anterior hypothalamic area, and that antipyretics of the aspirin type bring down this fever because they inhibit this synthesis.7. It is concluded that pyrogen increases prostaglandin synthesis not only in the preoptic anterior hypothalamic area. When injected into the liquor space increased synthesis of prostaglandin probably occurs in many regions near the surface of the brain stem, and when injected
I.V. may occur in other parts of the
C.N.S. as well. But to produce fever the prostaglandin has to act on the preoptic anterior hypothalamic area.
The composition of maternal plasma and foetal urine after feeding and drinking in chronically catheterized ewes during the last two months of pregnancy
Authors: Mellor D. J. , Slater J. S. 
Published: December 2014

1. The fluid sacs and bladders of sixteen foetuses in fourteen ewes were catheterized between 81 and 92 days gestational age and the rumens of four ewes were also catheterized.2. Between 95 and 145 days gestational age in forty‐six 24 hr experiments hourly samples of maternal plasma and foetal urine were obtained and in fifteen experiments foetal fluid samples were also taken at 4‐ to 6‐hr intervals.3. The osmolality, pH, and concentrations of sodium, potassium, chloride, glucose, fructose and urea were measured on all samples.4. During experiment there was no significant variation in the composition of amniotic or allantoic fluid. Marked changes in osmolality occurred in maternal plasma and foetal urine when ewes drank after feeding, but not in ewes that received water intrarumenally via catheter while feeding or in fasting ewes. Post‐prandial changes in maternal plasma osmolality may have altered transplacental water fluxes and as a result foetal plasma volume and osmolality.5. The results suggest that the foetus alters renal water retention by varying antidiuretic hormone (ADH) secretion in response to changes in blood volume and at later gestational ages plasma osmolality as well.6. Post‐prandial changes in the [Na+]/[K+] ratio of foetal urine suggested that foetal adrenocorticotrophin (ACTH) secretion is influenced by variations in foetal blood volume and glucose concentrations.7. The post‐prandial changes in foetal urine composition observed here support previous suggestions (Mellor & Slater, 1972) about the role of foetal urine in foetal fluid formation which were based on gestational changes in the composition of foetal fluids and urine sampled once daily during the post‐absorptive state.
Receptive field organization of bipolar and amacrine cells in the goldfish retina
Authors: Kaneko Akimichi 
Published: December 2014

1. Intracellular recordings were made from bipolar and amacrine cells in the isolated goldfish retina. Cells were identified mainly from their response patterns to a spot and an annulus in reference to the knowledge obtained from the previous work of intracellular Procion Yellow injection. Using white light and monochromatic lights receptive field organization of recorded cells were analysed.2. All bipolar cells had a centre‐surround organization in their receptive fields. The field centre was estimated to be 100–200 μm in diameter, and the surround 1–1·5 mm.3. Bipolar cells were classified into two types according to the response properties to monochromatic lights. Opponent colour cells received inputs from red and green cones, responding with red on‐centre, red and green off‐surround or vice versa. Cells without colour coding received input from red cones both in the field centre and the surround. In these cells the centre and the surround were well balanced.4. Amacrine cells were also classified into two types, a sustained type and a transient type. The sustained type amacrine cells responded with a steady potential change and were colour coded. They were hyperpolarized by red and depolarized by green light. The transient type amacrine cells responded with transient depolarization at on and off of light flashes. They received input chiefly from red cones and were not colour coded. Both types of amacrine cells showed a large spatial summation in an area over 2·5 mm; centre‐surround antagonism was not seen.5. Comparing the size of the receptive field with anatomy, especially with the size of dendritic spread, the field centre of bipolar cells agreed in size with their dendritic spread. Bipolar cell surround clearly exceeded its dendritic field. Since the response properties of the bipolar cell surround was mimicked most closely by the receptive field of external horizontal cells, the input to the bipolar cell surround is thought to be mediated by external horizontal cells.6. By comparing receptive field properties of various retinal cells it is suggested that both the opponent colour bipolar cells and the colour coded amacrine cells converge on to the double opponent ganglion cells.
Properties of the depolarizing synaptic potential evoked by peripheral illumination in cones of the turtle retina
Authors: O'Bryan P. M. 
Published: December 2014

1. Intracellular recordings of cone and horizontal cell responses to circles or annuli of light were made with the purpose of determining the properties of and the mechanisms underlying the horizontal‐cell‐mediated depolarization of cones which is evoked by surround illumination.2. A comparison of the responses of a cone and a near‐by horizontal cell to a peripheral stimulus revealed a striking similarity in their time courses and amplitudes, indicating that a correlation exists between the depolarizing synaptic potential in the cone and the response of the horizontal cell.3. The depolarizing synaptic potential in cones was separated from the direct response of the cell to light by illuminating the periphery with an annulus during steady, bright illumination of the central cone. The synaptic potentials were graded with the intensity or area of peripheral illumination. In some cones a spike‐like depolarization, which overshot the dark resting potential, occurred with bright illumination of the periphery.4. The effects of extrinsic current on the synaptic potential demonstrated that this response was generated by a change in membrane conductance consisting of two separate components with different time‐dependences and reversal levels. The slower of the two components, which often outlasts the stimulus, represents an increase in membrane conductance.5. The progressive decline in the amplitude of the responses of horizontal cells under a large spot from centre to periphery was found to result in a diminished feed‐back effect in cones near the edge of the spot. This leads to a Mach‐band effect during the plateau phase of cone responses, suggesting that one function of the feed‐back might be to enhance contrast discrimination.
Functional characteristics of mechanoreceptors in sinus hair follicles of the cat
Authors: Gottschaldt K.‐M. , Iggo A. , Young D. W. 
Published: December 2014

1. The discharge of impulses in afferent fibres dissected from the infraorbital and ulnar nerves of anaesthetized cats was recorded during controlled movements of the maxillary and carpal sinus hairs.2. Four main types of afferent units were identified. Two had slowly adapting responses characteristic of the epidermal type I, and dermal type II mechanoreceptors of the hairy skin. Two rapidly adapting responses to movement of the sinus hairs were found, one with a high velocity threshold and another with a low velocity threshold.3. The slowly adapting units showed a power relationship between the degree of displacement of the hair and the mean interspike interval of the response. Slowly adapting units also exhibited a power relationship between the velocity of displacement of a hair and the mean interspike interval of the response.4. The conduction velocities of all types of afferent units were measured and fell in the range of the Aα, fast myelinated fibres.5. Movements of the carpal sinus hairs yielded both types of slowly adapting response recorded in fibres of the ulnar nerve directly innervating the carpal sinus hair follicles, and rapidly adapting responses from Pacinian corpuscles, found in close association with, but external to, these follicles.6. On the basis of the findings in this study and the results of anatomical investigations of the receptor structures in the sinus hair follicle a correlation between the distinguishable afferent responses and the morphologically identifiable nerve endings has been proposed.
The sequential contractions of the rumen associated with eructation in sheep
Authors: Ruckebusch Y. , Tomov T. 
Published: December 2014

1. The orderly sequential movements of the reticulum and the rumen were studied in conscious sheep by electromyography using enamelled stainless‐steel wires implanted in various regions of the stomach wall and by recording mechanical changes within the various parts of the organ. Electrical activity of the rumen and/or pressure changes were related to eructation when the animals were at rest, feeding or ruminating.2. Secondary contractions of the rumen were found to originate in the ventral blind sac immediately following a primary contraction or independently. The wave of contraction originating in the ventral blind sac was seen to pass in a circular manner to the dorsal blind sac, the dorsal sac, the ventral sac and finally once more to the ventral blind sac. Eructation occurs at the end of the contraction of the dorsal sac. In each case, the time required to initiate the secondary cycle depended on the strength of contraction of the ventral blind sac.3. Sustained gaseous distension elicited numerous secondary contractions of the rumen concurrent with a lower frequency of reticular contractions. Although some secondary contractions were incomplete, all began with contraction of the ventral blind sac and were associated with eructation.4. Chemical stimulation of the rumen by fatty acids at pH 5·5–5·9 increased the ratio of secondary to primary contractions of the rumen to a varying extent depending on their initial rate.5. It was concluded that the seemingly random occurrence of a secondary cycle of the rumen was dependent on the activity of the ventral blind sac and its pattern could be altered by both mechanical and chemical stimulation.
Sweat storage as a factor influencing sweat discharge in sheep
Authors: Johnson K. G. 
Published: December 2014

1. Sweat output has been measured continuously from four Welsh Mountain sheep exposed on several occasions for periods of 8 hr to air temperatures of 20, 30 and 40° C. At all temperatures sweat was discharged intermittently. Discharges occurred more frequently at high air temperatures and when the animals were shorn, but not at consistently different frequencies in summer and winter.2. At 40° C Ta, sweat discharges were initially large, decreased in size during the first 1–3 hr, and then continued at regular intervals and at an approximately constant size for the remainder of the experiments. Most, and probably all, sweat glands in the skin were active at each discharge.3. The volumes of sweat glands, determined histologically, decreased after prolonged activity in the heat. Comparison of the changes in sweat gland volumes with the amounts of sweat discharged led to conclusions that the decline in sweat output seen on initial exposure to heat was probably due to depletion of secretory fluid from storage within the gland and that the subsequent regular discharge of small amounts of sweat was due to expulsion of newly formed secretion.4. Examination of serial sections of midside skin revealed that in these sheep sweat glands consisted of a superficial non‐convoluted duct separated from a large ampulla by a region in which the gland was convoluted. After long periods of sweating, the glands decreased in diameter in both the convoluted and non‐convoluted regions but were never found to be empty.5. The pattern of sweat output from sheep during prolonged exposure to heat appears to be determined not only by processes of secretion and intermittent expulsion but also by the amount and rate of depletion of preformed sweat stored in the gland lumen.
Effect of cations on the blood platelet release reaction
Authors: Sneddon J. M. , Williams K. I. 
Published: December 2014

1. Stimulus‐secretion phenomena in blood platelets incubated with trypsin or thrombin have been investigated.2. Secretion occurs in at least two stages: (a) induction, obtained when the platelets are incubated with proteolytic enzymes in the presence of the chelating agent EDTA, and (b) release, which occurs with the subsequent addition of Ca2+ to the incubation medium.3. Ca2+ was the only essential divalent cation required for release. Ba2+ and Mg2+ inhibited release and Sr2+ could only partially substitute for Ca2+.4. Blood platelets exhibited recovery from enzymic perturbation by trypsin or thrombin by a mechanism that was temperature dependent, but did not require the synthesis of new protein.5. The results are discussed in relationship to stimulus—secretion in other cells.