bluuebunny/crossref_metadata_2025_split huggingface dataset:
The rate of recovery of vision after early monocular deprivation in kittens
Authors: Giffin Fred , Mitchell Donald E. 
Published: December 2014

1. Fifteen kittens were monocularly deprived of vision by suturing the lids of the right eye together for various periods of time at different ages. A simple behavioural technique was used to assess the immediate effects of the period of monocular deprivation on the visual acuity of the deprived eye as well as the time course of any subsequent recovery.2. The extent of the recovery of vision was measured under conditions where the animal was either forced to use its deprived eye by performing a reverse suture or where the animal had both eyes open after the initial period of monocular occlusion.3. The initial effects of monocular deprivation were graded in severity according to the age at which the deprivation was imposed, ranging from apparent blindness in animals deprived at 6 weeks of age to only a small loss of acuity in kittens deprived at 12 weeks of age.4. The effects of deprivation imposed from birth were particularly severe, leading to a temporary blindness. Nevertheless after a period of time that became progressively longer with increasing deprivation, all animals showed some recovery of pattern vision over the course of the next 2 or 3 months. The extent of this recovery became progressively less as the period of deprivation was prolonged. There was even some recovery of vision (an acuity of 2·5 cycles/deg) in animals that were deprived throughout the duration of the ‘critical period’ to 4 months of age.5. Direct comparison of the rate of behavioural recovery between animals that were reverse sutured with that of litter‐mates that received binocular input after monocular occlusion to either 45 or 60 days of age proved to be remarkably similar, although the acuity that was eventually attained by the reverse sutured animals was always slightly higher.6. The recoveries observed after reverse suturing were reasonably well correlated with changes observed in the ocular dominance of visual cortical cells under similar circumstances.7. Although the recovery in these animals can be accounted for by the simple notion of a competitive interaction between the two eyes, the recovery observed in animals that had both eyes open after the initial period of deprivation cannot be so readily explained. Evidently there must be an additional non‐competitive mechanism of recovery.
Ionic effects on the membrane potential of hyperpolarizing photoreceptor in scallop retina
Authors: Gorman A. L. F. , McReynolds John S. 
Published: December 2014

1. The effects of different external ionic conditions and of metabolic inhibitors on the membrane potential of hyperpolarizing photoreceptors in the retina of the scallop Pecten irradians were examined in the presence and absence of light.2. Changes in extracellular K+ have a greater effect on membrane potential in the light than in darkness. The receptor potential is increased in amplitude when [K]o is reduced and decreased when [K]o is elevated. It is hyperpolarizing when [K]o is less than the estimated value for [K]i and depolarizing when this condition is reversed.3. The complete replacement of [Na]o causes a significant hyperpolarization of membrane potential in darkness, whereas it has a much smaller hyperpolarizing effect on the peak of the receptor potential.4. The ratio of Na+ to K+ permeabilities (PNa/PK) decreases during bright illumination. Our results suggest that PK is seven times that for PNa in the dark but is 57 times greater than PNa in light.5. The metabolic inhibitors DNP and NaCN cause membrane potential in the dark to hyperpolarize. This hyperpolarization is associated with a decrease in the PNa/PK ratio similar to that found during illumination.6. High [Ca+]o also causes membrane potential in the dark to hyperpolarize. This hyperpolarization is associated with an increase in membrane conductance.7. The results indicate that the hyperpolarizing receptor potential of the distal photoreceptor is produced by a light‐evoked increase in K+ permeability.
Effect of lower body negative pressure on human muscle nerve sympathetic activity
Authors: Sundlöf Göran , Wallin B. Gunnar 
Published: December 2014

1. Recordings of multi‐unit sympathetic activity were made from muscle branches of the median nerve in five healthy subjects during application of lower body negative pressure (l.b.n.p.). Simultaneous recordings of arterial blood pressure were made in four subjects. The strength of the neural activity was quantitated by counting the number of pulse synchronous sympathetic bursts and their amplitudes in the mean voltage neurogram.2. The general appearance of the sympathetic activity in pulse synchronous bursts was similar during control periods and during l.b.n.p., but during l.b.n.p. there was always an increase in the number of sympathetic bursts and usually also in the mean voltage amplitude of the bursts.3. The probability of occurrence of a burst was correlated to different blood pressure parameters of individual heart beats and both during control periods and during l.b.n.p. there was regularly a close negative correlation to diastolic, a low correlation to systolic, an intermediate negative correlation to mean and a positive correlation to pulse pressures.4. The changes in arterial blood pressure during l.b.n.p. were small and in most cases statistically insignificant. The observed increases in the number of sympathetic bursts during l.b.n.p. were significantly greater than what could be expected on the basis of the blood pressure changes.5. The findings suggest that the reflex control from the arterial baroreceptors is maintained during l.b.n.p. but, since the increase of sympathetic activity during l.b.n.p. could not be explained by a change in stimulation of the arterial baroreceptors, influence from other receptor groups (presumably intrathoracic volume receptors) must also have occurred.
Action potentials in gland cells of rat pituitary pars intermedia: inhibition by dopamine, an inhibitor of MSH secretion
Authors: Douglas W. W. , Taraskevich P. S. 
Published: December 2014

1. Cells were dissociated from rat pituitary pars intermedia, maintained in culture, and subjected to electrophysiological study.2. Recorded membrane potentials varied widely (range — 18 to about — 80 mV). They were relatively insensitive to changes in external Na but were rapidly and reversibly lowered by excess K.3. Action potentials were elicited by passing current through intracellular recording electrodes. They were reversibly blocked by tetrodotoxin (TTX, 2 × 10−6
M) or by removal of Na from the recording solution and thus appeared to be Na spikes. Cells yielding action potentials in response to depolarization had relatively high membrane potentials (about — 65 mV) which may be representative of the true resting membrane potential of pars intermedia cells.4. Spontaneous action potentials were recorded extracellularly from nearly all the many isolated pars intermedia cells studied with a microsuction electrode. Their amplitude was reduced by TTX (0·1‐2 × 10−6
M). Electron microscopic examination of cells producing action potentials showed them to be hormone‐containing parenchymal (gland) cells.5. Dopamine (10−6
M), a presumed physiological inhibitor of secretion of melanocyte stimulating hormone (MSH) from pars intermedia cells, decreased the frequency of spontaneous action potentials but not their amplitude. Similar effects were seen with noradrenaline (10−6
M), another inhibitor of MSH secretion, whereas isoprenaline and 5‐hydroxytryptamine (5‐HT), which do not inhibit MSH secretion, had no effect.6. Action potentials may be involved in stimulus‐secretion coupling in pars intermedia cells.
Histochemical reactions of fibres in a fast twitch muscle of the cat
Authors: Edjtehadi Guiti D. , Lewis D. M. 
Published: December 2014

1. Serial sections of flexor digitorum longus muscle (f.d.l.) of the cat were examined histochemically for four enzyme systems: adenosine triphosphatase (ATPase) with alkaline and acid pre‐incubation, phosphorylase and succinic dehydrogenase (SDHase).2. The number of types into which fibres should be divided was assessed by estimating enzyme reaction intensity from measurements of light transmission through photomicrographs. It was concluded that in general the enzyme reaction intensities of fibres were distributed continuously. However, the distribution histograms showed two (phosphorylase and SDHase) or three (acid and alkaline ATPase) clear peaks. Eighteen combinations of reaction intensities (profiles) were seen of which eight were very rare. The distribution of profiles differed between individuals but were similar in right and left muscles.3. Areas of fibres were measured from muscles which had been fixed at the length at which twitch tension was maximal. The variance in fibre area with any one profile was significantly less than the variance in fibre area of all fibres within a muscle. There were significant differences between the mean areas of fibres with different profiles.4. If only three enzyme reactions are considered (acid and alkaline ATPase and phosphorylase) the majority of fibres fall into one of the three classes commonly accepted for other muscles. The remainder would fit into this classification with the minimal assumption of only one error of fibre typing resulting from the continuous distributions of enzyme reaction intensities. The SDHase reaction was not strongly correlated with the three classes and could be used to divide the fibres further into six groups. Differences between means of fibre areas were significant for all pairs out of these six groups except one.5. The grouping may be considered to reflect a dual system of enzymes, the two systems being (a) ATPases and phosphorylase, (b) SDHase. A possible role of nervous activity in determining this dual system is discussed. The hypothesis involves two partly independent characteristics of motoneuronal activity: (a) the frequency of impulses, and (b) the total number of impulses.6. The measurements are correlated with other physiological variables in the individual animals. The mean areas of fibres in all groups increased with body weight. There were changes in the proportions of light and dark SDHase fibres related to weight. The total area contributed by dark alkaline ATPase fibres decreased and that by intermediate alkaline ATPase fibres increased with increasing twitch time to peak.7. Specific tension of the group of slower muscle fibres in f.d.l. was estimated to be 0·29 N.mm−2 compared with 0·39 N.mm−2 for the faster fibres.
Phasic firing enhances vasopressin release from the rat neurohypophysis
Authors: Dutton A. , Dyball R. E. J. 
Published: December 2014

1. Isolated rat neural lobes were incubated in vitro and electrically stimulated to release vasopressin. The released vasopressin was assayed using a radioimmunoassay and there was a reasonably good correlation (r = 0.81) between results obtained with this assay and those obtained by bioassay with the rat blood pressure method.2. Regular stimulation at frequencies of 5, 10 and 20 Hz released progressively more vasopressin and the release could be blocked by addition of tetrodotoxin to the incubation medium.3. Stimulation with pulse patterns derived from tape recordings of phasically firing units in the supraoptic nucleus of dehydrated rats released more vasopressin than the same number of pulses regularly spaced in time. In the range 2‐8 pulses/sec vasopressin release was related to the pulse frequency within the bursts (r = 0.90) and the number of short (< 100 msec) interpulse intervals (r = 0.92). Vasopressin released per pulse increased over the frequency range 3‐6 pulses/sec, but above 6 pulses/sec vasopressin release per pulse tended to diminish.4. We conclude that phasic firing of vasopressin neurosecretory cells may enhance vasopressin release in vivo and that an important factor in determining release is the number of short interspike intervals.
Air humidity and carotid rete function in thermo‐regulation of the goat
Authors: Jessen Claus , Pongratz Hans 
Published: December 2014

1. The effects of air humidity on respiratory rate have been studied in conscious goats exposed to an air temperature of + 33 °C. Before the experiments the animals had been chronically implanted with hypothalamic thermodes and intravascular heat exchangers to manipulate hypothalamic and general body core temperatures.2. Raising air humidity from 37 to 96% at constant air temperature resulted in a rise of respiratory rate, an immediate increase in hypothalamic temperature and a delayed smaller increase in general body core temperature.3. The rise of respiratory rate was smaller when general body core temperature was clamped at its control level and was absent when hypothalamic and general body core temperatures were clamped at their control levels during the humid air phase.4. It is concluded that the effect of high air humidity on respiratory rate in goats is predominantly the result of a rise in hypothalamic temperature acting on local thermosensitive structures. The carotid rete heat exchanger is thought to provide the thermal link between the evaporating surfaces of the upper respiratory tract and the hypothalamus.5. This function of the carotid rete heat exchanger is restricted to heat stressed animals. In animals subject to central cooling no local effects on hypothalamic temperature could be observed when the temperature of the inspired air was altered from + 33 to ‐ 17 °C.
Cold acclimation in the secretory responses of the isolated exocrine pancreas of the rat
Authors: Habara Y. , Kanno T. , Saito A. 
Published: December 2014

1. The secretory function of the isolated and perfused exocrine pancreas has been studied in the course of cold acclimation in rats that were fed at an ambient temperature of 1 °C in an artificial climatic room.2. A series of experiments was carried out in early autumn (autumn series). The sums of the outputs of protein, amylase, zymogen protease, lipase, and juice flow in samples collected for a total of 30 min during and after 5 min stimulation with different concentrations of cholecystokinin—pancreozymin (CCK—PZ; 5‐50 m‐u./ml.) were simultaneously measured in the autumn series of experiments, and they were plotted against the logarithmic scale of concentration of CCK—PZ to obtain a dose—response relation.3. The sums of protein output, lipase output, and juice flow evoked by different concentrations of CCK—PZ in the group of rats fed at 1 °C for 3 weeks were almost identical to the corresponding value in the group fed at about 21 °C for 3 weeks.4. The sum of output of zymogen protease in the former group was almost identical to the corresponding value in the latter group except that the sum induced by 20 m‐u. CCK—PZ/ml. was significantly larger in the former.5. The sum of output of amylase induced by various concentrations of CCK—PZ in the former group was significantly smaller than the corresponding value in the latter group.6. It was thus concluded that the CCK—PZ‐induced outputs of protein, lipase, and zymogen protease were little affected if any by 3 weeks of cold exposure, whereas the CCK—PZ‐induced amylase output was significantly suppressed.7. Another similar series of experiments was performed in the summer of the same year. The results obtained suggest that the secretory function of exocrine pancreas is directly inhibited by prolonged cold exposure in summer but it is not in autumn.
Evidence supporting the indirect depolarization of primary afferent terminals in the frog by excitatory amino acids
Authors: Evans R. H. 
Published: December 2014

1. Isolated hemisected spinal cords of the frog have been used to investigate the way excitant amino acids depolarize primary afferent fibres and terminals.2. GABA and excitant amino acids caused depolarization in dorsal roots. But dorsal roots sectioned at the point of exit from the spinal cord responded only to GABA.3. Prolonged application of kainate or
N‐methyl‐
D‐aspartate to hemicords caused a depolarization of dorsal roots in association with an increased extra‐cellular [K+]. The two effects decayed with similar time courses. The depolarization recorded from ventral roots was maintained in the presence of the excitants.4. Field potentials, elicited by electrical stimulation of ventral roots and recorded in the ventral horn of Mg blocked preparations, were abolished by prolonged treatment with kainate. Corresponding dorsal horn field potentials elicited by electrical stimulation of dorsal roots were resistant to the presence of kainate.5. Excitability of motoneurones or afferent terminals was measured from the amplitude of action potentials evoked by submaximal cathodal stimulation of ventral or dorsal horns and recorded in ventral or dorsal roots respectively. Prolonged application of kainate to Mg blocked preparations abolished the excitability of motoneurones within 5 min, but the excitability of primary afferent terminals was increased and maintained for several hours.6. These observations support the hypothesis that primary afferent terminals in the frog do not have receptors for excitatory amino acids and that depolarization of terminals induced by excitatory amino acids is mediated through release of K from other cells within the dorsal horn.
Release of inorganic phosphate during activity in mammalian non‐myelinated nerve fibres
Authors: Maire J. C. , Straub R. W. 
Published: December 2014

1. The efflux of labelled phosphate was measured in desheathed rabbit vagus nerve at rest and during activity.2. In solutions with 2 m
M‐phosphate and 1 m
M‐K the rate constant of the resting efflux was 2·7 × 10−3 min−1; stimulation caused an extra fractional loss of 2·8 × 10−6 impulse−1.3. Lowering the phosphate concentration decreased the resting and the stimulated efflux; with 0·2 m
M‐phosphate the corresponding values were 1·9 × 10−3 min−1 and 1·8 × 10−6 impulse−1, respectively.4. Increasing the K to 5·6 m
M decreased both resting and stimulated efflux.5. Lowering the temperature decreased the resting efflux with a Q10 of 2·9 and the stimulated efflux with a Q10 of 8·1.6. Chromatography of the effluent showed that at rest and during activity at least 96% of the radiophosphate was in the orthophosphate fraction.7. Replacing the Na of the solution by Li lowered the rate constant of the resting efflux to 0·8 × 10−3 min−1 and abolished the extra release during activity, without reduction of the action potential.8. The presence of ouabain did not affect the resting efflux, except at 100 μ
M, when a transient reduction was found. The extra fractional loss was not affected with 0·001 μ
M; with 0·01‐0·5 μ
M, it was reduced without much change in the action potential, and abolished at higher concentrations.9. The results agree with the hypothesis that the extra release results from an increase in internal inorganic phosphate caused by increased break‐down of ATP during recovery.10. Comparison with the O2 consumption shows that about 1% of the inorganic phosphate liberated at the inside of the axons escapes to the outside.
Thermoregulatory noradrenergic and serotonergic pathways to hypothalamic units
Authors: Brück K. , Hinckel P. 
Published: December 2014

1. In guinea‐pigs hypothalamic single units were extracellularly tested for their response to thermal stimulation of the skin and to electrical stimulation of two different pontine areas, the nucleus raphé magnus and the dorsomedial reticular formation. Furthermore, thermoregulatory control actions were measured during the stimulations.2. Electrical stimulation of those reticular formation areas containing noradrenaline cells caused an increase of oxygen uptake, electrical muscle activity and body temperature, while stimulation of the nucleus raphé magnus, known to contain serotonin cells, brought about inhibition or had no effect.3. The recorded units could be subdivided into three groups.Cell type a. Neurones on the boundary of preoptic and anterior hypothalamic regions which increased their firing rate when the skin was cooled and decreased it when the nucleus raphé magnus was stimulated.Cell type b. Neurones in the anterior hypothalamus which did not respond to brain‐stem stimulation.Cell type c. More posterior neurones which increased their firing rate when the skin was warmed or when the nucleus raphé magnus was stimulated and decreased their firing rate when the reticular formation was stimulated.4. Cell type a seems to represent interneurones which are connected to the ascending serotonergic thermoregulatory pathway. As for cell type c, it is inferred that it could represent interneurones which control the threshold for shivering and non‐shivering thermogenesis.
Input‐output relationships of central neural circuits involved in respiration in cats
Authors: Eldridge Frederic L. , Gill‐Kumar Pritam , Millhorn David E. 
Published: December 2014

1. Inspiratory output responses, measured as integrated phrenic activity, to hypercapnia, to unilateral and bilateral carotid sinus nerve stimulation and to combinations of these stimuli were determined in paralysed, vagotomized and glomectomized cats whose end‐tidal PCO2 was kept constant by means of a servo‐controlled ventilator. In addition, the effect on these responses of the mechanism that causes the respiratory after‐discharge was determined.2. Above the threshold for rhythmic activity, the inspiratory response to hypercapnic stimulation of the central chemoreceptor was curvilinear, showing progressively smaller increments of output for equal increments of PCO2 as the latter became higher.3. The combining of stimuli from right and left carotid sinus nerves failed to show an algebraically additive effect; the response was approximately 70% of that predicted from a summing of the separate stimuli given alone.4. The response to a constant carotid sinus nerve test stimulus was progressively decreased in magnitude as the pre‐stimulus level of respiratory activity was increased by conditioning stimulation of the central chemoreceptors by hypercapnia, by stimulation of the opposite carotid sinus nerve or by the mechanism that generates an after‐discharge.5. From a descriptive standpoint, our findings show that there is a negative or hypoadditive interaction between the peripheral and central inputs at the level of the central respiratory controller. However, we present evidence that, rather than being a specific interaction between peripheral and central inputs, the response is due to the properties of a neural component of the central pathway. This component is common to both inputs and develops progressive saturation of its neural elements as its activity increases.6. In addition, the neural mechanism which generates a respiratory after‐discharge appears to saturate completely at a lower level of inspiratory activity than that at which the common pathway develops complete saturation. This finding supports the idea that this mechanism represents an independent input to the respiratory controller.7. Because the described a‐linear response characteristics of the central respiratory controller are due to its inherent neuronal properties rather than to specific interactions between inputs, we suggest that studies of such ‘interactions’ must be interpreted with this consideration in mind.