bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in renal cyclic nucleotide content as a possible trigger to the initiation of compensatory renal hypertrophy in rats
Authors: Dicker S. E. , Greenbaum A. L. 
Published: December 2014

1. Cyclic adenosine 3′, 5′‐monophosphate (cyclic AMP) and cyclic guanosine 3′, 5′‐monophosphate (cyclic GMP) have been estimated in the kidneys of rats.2. Ten minutes after unilateral nephrectomy there was a threefold increase of cyclic GMP in the remaining kidney, which was accompanied by a moderate fall of cyclic AMP.3. The changes in cyclic nucleotides in the remaining kidney after unilateral nephrectomy were of short duration.4. When an anephric rat was cross‐circulated with a normal litter‐mate, there was an increase of cyclic GMP concentration in the kidneys of the latter, which reached its maximum 10 min after the establishment of the cross circulation.5. In experiments where one kidney of a litter‐mate was transplanted to the neck of another rat, unilateral nephrectomy was not followed by changes of the level of cyclic nucleotides in either the transplanted or the remaining kidney. Bilateral nephrectomy, however, resulted in a marked increase of cyclic GMP in the transplanted kidney.6. The clamping of the blood vessels to one kidney for periods up to 10 min had the same effect as unilateral nephrectomy on the concentration of cyclic GMP in the remaining kidney. When the clamp was removed and the circulation restored, the concentrations of cyclic nucleotides returned to preoperative levels in both kidneys.
The effect of calcium ions on the binomial parameters that control acetylcholine release during trains of nerve impulses at amphibian neuromuscular synapses
Authors: Bennett M. R. , Fisher C. 
Published: December 2014

1. A study has been made of the effects of changing the external calcium concentration [Ca]o on the binomial parameters p and n that control the average quantal content (m̄) of the end‐plate potential (e.p.p.) during trains of nerve impulses at synapses in amphibian striated muscle.2. In high external calcium concentrations (0·4 m
M ≤ [Ca]o < 1·0 m
M) the increase in m̄ of a test impulse following a conditioning impulse at different intervals (< 100 msec) was due to an increase in the number of quanta available for release, n; the increase in m̄ of successive e.p.p.s in a short high frequency train was primarily due to an increase in n.3. In high external calcium concentrations (1·0 m
M ≤ [Ca]o < 10 m
M) there was a decrease in m̄ of a test impulse following a short high frequency conditioning train (4‐5 impulses, 20‐100 Hz) at different intervals (200 msec < 5 sec) and this was due to a decrease in the number of quanta available for release, n; in a long high frequency train (20 impulses, 20‐100 Hz) there was an increase in m̄ for the first few successive e.p.p.s followed by a depression of m̄ which eventually reached a steady state and these changes in m̄ were due to changes in n; the higher the frequency the greater was the depression in n during the steady‐state period.4. In high calcium concentrations, the steady‐state m̄ reached in the first 20 impulses during continual stimulation at high frequency gave way to a decline in m̄ over several minutes until a new depressed steady‐state value of m̄ was reached and this was maintained during the longest periods of stimulation (30 min); this decline in m̄ was primarily due to a decline in the number of quanta available for release.5. These changes in the number of quanta available for release during trains of impulses are predicted in terms of a hypothesis in which facilitation is due to the accumulation of a residual calcium‐receptor complex in the nerve terminal that determines the fraction of a pool of quanta which contributes to n, and depression is due to a decrease in the number of quanta in this pool.
Inhibitory processes underlying the directional specificity of simple, complex and hypercomplex cells in the cat's visual cortex
Authors: Sillito A. M. 
Published: December 2014

1. The iontophoretic application of bicuculline, an antagonist of GABA, the putative inhibitory transmitter in the visual cortex, has been used to examine the contribution of post‐synaptic inhibitory processes to the directional selectivity of simple, complex and hypercomplex cells in the cat's striate cortex.2. The directional selectivity of simple cells was significantly reduced or eliminated during the iontophoretic application of bicuculline. This supports the view that the selectivity is derived from the action of a GABA‐mediated post‐synaptic inhibitory input modifying their response to a non‐directionally specific excitatory input.3. Complex cells were subdivided into three categories on the basis of the action of iontophoretically applied bicuculline on their directional selectivity, receptive field characteristics and distribution in terms of cortical layer. They are referred to as type ‘1’, ‘2’ and ‘3’ complex cells.4. The directional specificity of type ‘1’ complex cells was eliminated during the iontophoretic application of bicuculline. It seems likely, therefore, that they receive a non‐directionally specific excitatory input and that, as for simple cells, the directional specificity derives from the action of a GABA‐mediated post‐synaptic inhibitory input. No type ‘1’ complex cells were recorded below layer IV.5. The directional specificity of type ‘2’ complex cells was unaffected by the iontophoretic application of bicuculline, despite increases in response magnitude, a block of the action of iontophoretically applied GABA and, in some cases, changes in other receptive field properties. It is suggested that these cells receive a directionally specific excitatory input. The type ‘2’ complex cells were found both superficial and deep to layer IV with the majority in layer V.6. Type ‘3’ complex cells appear to have very similar receptive field properties to those of the cells described by other workers as projecting to the superior colliculus. They were found predominantly in layer V. Their directional specificity was not eliminated by the iontophoretic application of bicuculline. However, they exhibited a powerful suppression of the resting discharge in response to stimulus motion in the non‐preferred direction. Iontophoretic application of ammonium ions revealed a small excitatory response in place of the suppression. It appears from these observations that the directional specificity of the type ‘3’ complex cells could be determined, at least in part, by an inhibitory process which is not GABA‐mediated.7. The directional specificity of hypercomplex cells found in layers II and III was unaffected by the iontophoretic application of bicuculline, and they showed no suppression of their background discharge level in response to stimulus motion in the non‐preferred direction. This evidence is consistent with the view that they receive a directionally specific excitatory input.
Effects of 5‐hydrooxytryptamine on pial arteriolar calibre in anaesthetized cats
Authors: Harper A. Murray , MacKenzie Eric T. 
Published: December 2014

1. The responses of individual pial arterioles and small arteries to perivascular injections of 5‐hydroxytryptamine were studied in anaesthetized cats.2. Pial arteriolar calibre was measured by a television image‐splitting technique.3. At normotension, the average response of pial vessels was dilatatory at injected 5‐hydroxytryptamine concentrations between 10−10 and 10−4
M.4. These pial vascular changes were, however, dependent upon the resting vessel calibre: those arterioles < 70 μm dilated universally, whereas small arteries ≥ 200 μm in resting diameter tended to constrict in response to 5‐hydroxytryptamine.5. The 5‐hydroxytryptamine‐induced dilatation of pial arterioles < 70 μm in resting calibre was directly dependent on mean arterial pressure, although no such relationship was observed with the larger cerebral vessels.6. It is concluded that the specific cerebrovascular actions of 5‐hydroxytryptamine are largely tone‐dependent. The greater the resting tone of a pial arteriole, then the greater will be the tendency of that vessel to dilate in response to 5‐hydroxytryptamine, and vice versa.7. The direct vascular actions of 5‐hydroxytryptamine are in contradistinction to the observed changes in cerebral tissue perfusion and it would therefore appear that the effects of this amine on cerebral metabolism and neuronal activity outweigh its cerebrovascular actions under physiological conditions.
Differential enhancement of early and late components of the cerebral somatosensory evoked potentials during forced‐paced cognitive tasks in man
Authors: Desmedt John E. , Robertson Donald 
Published: December 2014

1. Cerebral potentials evoked by random sequences of electrical stimuli to four fingers were recorded in intact man performing selective attention tasks. Eye movements and other artifacts were excluded from the averaged traces. Different finger stimuli were designated as targets to be mentally counted in alternate runs of each experiment. The high mean random rate of stimuli (150/min) fully involved the processing capacities of the subject. Vigilance changes or differential expectancy effects were excluded by the reciprocal random design with four different sensory channels. Task‐related enhancements of somatosensory evoked potentials (s.e.p.) components were estimated by comparison with the s.e.p.s to physically identical finger stimuli recorded in runs when the subject attended signals in the opposite hand. The experimental design avoided subject's fatigue.2. The primary s.e.p. components N20 and P45 were not significantly influenced and this excluded centrifugal gating of the corticipetal signals as a mechanism.3. The earliest task‐related changes in s.e.p. occurred 55‐135 msec (mean 77·7 msec) after the target finger stimuli. In most cases the negative N140 component was markedly enhanced both for target signals and for non‐targets in the adjacent finger of the same hand. However, in several subjects the targets elicited a positive P100 component instead. Both N104 and P100 were larger at the contralateral parietal focus than ipsilaterally. They were definitely smaller at the vertex and frontal scalp locations.4. Enhancements of N140 were not observed in similar random four‐finger experiments carried out at a 4 times slower mean rate, but they occurred in a bisensory paradigm with finger shocks and acoustic clicks at that slower rate.5. A large positive P400 component was only elicited by target stimuli. Its voltage was maximum over the parietal region and was equal on both sides.6. At least three categories of components can be differentiated in the cortical s.e.p. on the basis of their time domains (roughly 18‐70 msec, 70 to 200‐250 msec and over 200 msec after the finger stimuli), cerebral hemispheres topography and cognitive parameters. Verbal instructions defining specific perceptual tasks can to a large extent switch on and off the components of the second and third categories when the processing resources of motivated subjects are fully committed in a well designed forced paced paradigm. In certain individuals physiological evidence for a different ‘stimulus set’ processing of target (P100) and non‐target (N140) signals was documented for the first time.
Postural effects on muscle nerve sympathetic activity in man
Authors: Burke David , Sundlöf Göran , Wallin B. Gunnar 
Published: December 2014

1. Pulse‐synchronous bursts of multi‐unit sympathetic activity (MSA) were recorded in peroneal muscle nerve fascicles in eight healthy subjects when lying, sitting and standing. The sympathetic activity was quantitated by counting the number of bursts in the mean voltage neurogram/min. Postural changes were analysed by considering the total activity to be a product of the number of bursts in relation to the number of heart beats (burst incidence) and the heart rate.2. In lying there were large interindividual differences in total activity, but for all subjects the activity increased when going from lying to sitting and from sitting to standing. With a few exceptions the increase between the lying and sitting postures was associated with an increase in both burst incidence and heart rate whereas between the sitting and standing postures there was an increase in heart rate but on the average no change in burst incidence.3. When going from lying to sitting or from sitting to standing the magnitude of the change in burst incidence was inversely related to the initial burst incidence so that subjects with low initial values usually showed greater increases in burst incidence than subjects with high initial values. Some subjects with high initial values decreased their burst incidence.4. With changes in postures there was an inverse linear relationship between the fraction of the change in MSA associated with a change in burst incidence and the fraction associated with a change in heart rate. An increase in total activity could be obtained by changing only burst incidence, by increasing heart rate without changing burst incidence, or by appropriate changes in both parameters. The slope of the regression line was ‐0·53 indicating that for adequate postural compensation fewer additional bursts were required when the compensatory response involved an increase in heart rate rather than an increase in only burst incidence.5. It is suggested that an impairment of the ability to regulate heart rate will make subjects with high burst incidence in the lying position orthostatically more vulnerable than those with low burst incidence.6. Shortly after standing up one subject developed bradycardia and subsequently fainted. The nerve recording was maintained until the subject collapsed. During the initial bradycardia no sympathetic bursts occurred suggesting that the syncope was associated with an interruption of normal baroreflex feedback between blood pressure and sympathetic outflow.
Re‐innervation of guinea‐pig superior cervical ganglion cells by preganglionic fibres arising from different levels of the spinal cord
Authors: Njå Arild , Purves Dale 
Published: December 2014

1. The ability of preganglionic axons to re‐establish their normal pattern of synaptic connexions with superior cervical ganglion cells has been studied after section of the cervical sympathetic trunk.2. In vivo stimulation of the last cervical (C8) and the first seven thoracic ventral roots (T1—T7) 3‐4 months after section of the trunk produced end‐organ responses similar to those observed in normal animals.3. The pattern of innervation of individual neurones, determined by intracellular recording of synaptic potentials 4‐9 months after cutting the sympathetic trunk, was also similar to that observed in normal neurones. Both normal and re‐innervated ganglion cells were contacted by pre‐ganglionic axons arising from C8 to T7, and each neurone was usually innervated by a contiguous subset of these segments.4. Re‐innervated neurones, as normal cells, were typically dominated by the innervation from a particular spinal cord segment, with the adjacent segments contributing a synaptic influence that decreased as a function of distance from the dominant segment. This was true whether the amplitude of the post‐synaptic potential, or the estimated number of contributing axons, was used as the criterion of segmental dominance.5. Re‐innervated neurones, however, showed some abnormalities. The average number of ventral roots contributing innervation to each neurone was reduced from 4·1 to 3·0, and discontinuities in the sequence of innervating segments were more frequent than in normal neurones. Moreover, fewer preganglionic axons contacted each neurone after regeneration.6. A further difference between normal and re‐innervated neurones during the period covered by these experiments was that axons from the more caudal spinal cord segments were less successful in re‐establishing contacts with ganglion cells than those from the rostral segments. The more caudal the position of the preganglionic neurones, the more pronounced was this relative deficiency.7. Although anomalies of ganglion cell innervation were apparent, the basis for the restoration of normal functional effects appears to be the re‐establishment of a pattern of innervation of individual neurones similar to that observed in normal ganglia.
Changes in motor commands, as shown by changes in perceived heaviness, during partial curarization and peripheral anaesthesia in man
Authors: Gandevia S. C. , McCloskey D. I. 
Published: December 2014

1. The centrally generated ‘effort’ or direct voluntary command to motoneurones required to lift a weight was studied using a simple weight‐matching task when the muscles lifting a reference weight were weakened. This centrally generated input to motoneurones was increased when the lifting muscles were partially paralysed with curare or decamethonium as judged by the increased perceived heaviness of a reference weight lifted by the weakened muscles.2. If subjects were asked simply to make matching isometric contractions when the lifting muscles were weakened the isometric tension produced by a weakened muscle was over‐estimated.3. When subjects matched weights by flexing the distal joint of the thumb the perceived heaviness of a reference weight during a control partial curarization was compared with its perceived heaviness during a similar partial curarization when the thumb was also anaesthetized. At any level of maximal strength during curarization the perceived heaviness (which reflects the motor command to lifting motoneurones) was increased when the thumb was anaesthetized.4. This increased voluntary command to lifting motoneurones may be required because automatic reflex assistance provided by apparent servo action from the long flexor of the thumb is suppressed by anaesthesia of the thumb (Marsden, Merton & Morton, 1971, 1973, 1976a; Dyhre‐Poulsen & Djørup, 1976).
The role of acetylcholine in the regulation of ion transport by rat colon mucosa
Authors: Browning J. G. , Hardcastle Jacqueline , Hardcastle P. T. , Sanford P. A. 
Published: December 2014

1. Acetylcholine increases the potential difference across rat proximal colon both in vivo and in vitro.2. There is a sigmoid relationship between the change in potential difference and the logarithm of the dose of acetylcholine. The dose—response curve is shifted to the left by neostigmine and to the right by atropine, suggesting that the action of acetylcholine is mediated by a muscarinic type of receptor.3. The dose‐response curve for acetylcholine in vivo is not altered by the ganglion‐blocking agents hexamethonium and pentolinium, suggesting a direct effect of this transmitter on the colon.4. Acetylcholine causes an increase in potential difference, a small decrease in resistance and hence a rise in the current generated by both normal and stripped everted sacs of rat colon.5. In the absence of sodium, the calculated current change produced by acetylcholine is reduced, and the removal of chloride has a similar inhibitory effect. The absence of bicarbonate does not significantly affect the response.6. Acetylcholine virtually abolished net sodium movement and induced net chloride secretion and these changes accounted for the increased short‐circuit current.7. Acetylcholine had no effect on oxygen consumption by rings of colon.8. Tracts staining for acetylcholinesterase were observed running from the submucous plexus towards the mucosal epithelium.9. This study shows that acetylcholine can influence ion movement by rat colonic mucosa and suggests that the autonomic nervous system might be involved in the regulation of transport mechanisms in this tissue.
An analysis of the anatomical basis for the mechanical response to motor nerve stimulation of the rat vas deferens
Authors: Anton Patricia G. , Duncan Morag E. , McGrath J. C. 
Published: December 2014

1. An anatomical basis was sought for the biphasic motor nerve response of the rat vas deferens. The motor nerve pathway to the tissue was stimulated at different points between the vertebral outflow and the intramural fibres, in the pithed rat and in isolated tissues, to examine the possibility of two anatomically separate groups of neurones. Different preparations of the isolated tissue were devised to detect whether different groups of smooth muscle fibres contributed to the two phases.2. The fibres mediating both phases of the response arose from the upper lumbar vertebral outflows. Both phases were elicited by pre‐ or post‐ganglionic stimulation and could be depressed by hexamethonium. In the pithed rat or with hypogastric nerve stimulation in the isolated tissue, however, the initial ‘twitch’ phase was relatively resistant to such blockade.3. When the rat vas deferens was perfused through the lumen in situ or in vitro, the perfusion pressure response to motor nerve stimulation exhibited two phases similar to those of the longitudinal contractile response.4. Isolated rat vasa were bisected into portions, each of which was stimulated and longitudinal tension was recorded. The proportions of the two phases of the response varied along the length of the tissue. At the prostatic end the total response was relatively weak with a dominant ‘twitch’ and at the epididymal end the two phases were comparable in magnitude. The distribution of adrenergic nerve terminals within the muscle layers also varied along the length of the rat vas deferens.5. The effects of drugs were investigated on the motor responses of the above preparations. The ‘twitch’ phase was relatively susceptible to blockade by reserpine and lysergic acid diethylamide and the ‘secondary’ phase to phentolamine with both equally sensitive to guanethidine. Each phase had similar susceptibilities to blockade irrespective of which part of the tissue was involved.6. It was concluded that two types of nerve‐muscle transmission may be involved in the rat vas deferens with the proportion of each varying along the length of the tissue but both displaying pharmacological characteristics of adrenergic fibres.
Interaction between longitudinal and circular muscle in intestine of cat
Authors: Connor J. A. , Kreulen David , Prosser C. L. , Weigel R. 
Published: December 2014

1. Slow waves recorded from isolated longitudinal muscle averaged 13 mV and had slow rate of rise (0.04 V/sec) whereas when recorded from intact segments the amplitude averaged 27 mV and the rate of rise was more rapid (0.09 V/sec), often with a notch between the initial peak and the plateau. Membrane potentials of longitudinal muscle were similar in isolated and intact preparations (‐ 66 mV). Resting potentials of circular muscle averaged ‐ 67 mV.2. Small bundles of circular muscle tested in the double sucrose gap produced activity, either spontaneously or in response to stimulation, which fell into three categories: fast spikes (50‐200 msec duration), slow spikes (1‐5 sec duration), and small graded responses. The duration of fast spikes could be increased severalfold by the addition of TEA; the graded responses were converted to full‐sized spikes by TEA.3. Treatment of circular muscle with Ca‐free Krebs solution eliminated spikes, and in intact preparations reduced the amplitude and rate of rise of slow waves and eliminated the notch on slow waves.4. Current—voltage curves of longitudinal muscle show delayed rectification in the depolarizing quadrant; similar curves of circular muscle show anomalous rectification, i.e. a region where a very small current causes a large voltage change.5. Non‐polarized electrotonic coupling between longitudinal and circular layers indicates low‐resistance pathways. Apparent space constants of longitudinal muscle are greater when attached to circular muscle than when isolated.6. It is concluded that small slow potentials originate rhythmically in longitudinal muscle, that these spread passively to circular muscle where a regenerative amplification occurs which depends on Ca conductance and the amplified slow waves spread back to the longitudinal layer. In the intact intestine pacemaking is, therefore, separate from propagation and the circular muscle provides the bulk of depolarizing current for propagation.