bluuebunny/crossref_metadata_2025_split huggingface dataset:
Centrally evoked sympathetic discharge: a functional study of medullary vasomotor areas
Authors: Kahn Norman , Mills Elliott 
Published: December 2014

1. The medulla oblongata was stimulated electrically in decerebrate cats following bilateral vagotomy. Changes in splanchnic nerve discharge evoked by stimulation of pressor and depressor areas in the medulla are correlated with changes in arterial pressure. An interaction of baroreceptor afferents with the efferent sympathetic system at the level of the medulla and/or spinal cord is demonstrated. Evidence is presented which suggests that it is possible to alter activity selectively in a given division (splanchnic) of the sympathetic outflow.2. Evoked responses were categorized as follows:(a) Sustained splanchnic activation; an immediate increase in total splanchnic activity occurred with only a small, gradual decline in activity during the stimulation period. Mild stimulation (150‐200 μA) raised systolic pressure by 60‐80 mm Hg and stronger stimulation (300‐400 μA) increased pressure by 100‐150 mm Hg. When comparable pressor responses were elicited from points on either side of the mid line, splanchnic excitation was greater with homolateral stimulation (left side).(b) Unsustained splanchnic activation; an immediate increase in activity occurred which declined sharply as systolic pressure rose by 60‐100 mm Hg during stimulation. Such a decline was attributed to the influence of baroreceptor afferents. Thus, if previous carotid occlusion was maintained during stimulation, the decline in activity was minimized although the pressor response increased. It is suggested that the structures yielding unsustained responses differ from those yielding sustained responses in their functional relation with the baroreceptor afferents.(c) Reduced splanchnic discharge during direct medullary stimulation; a partial or complete inhibition of splanchnic activity was obtained, which was sometimes accompanied by a 20‐40 mm Hg reduction in systolic pressure. However, the direction and magnitude of the systemic pressure change were not as consistently related to the splanchnic response as they were during activation. Even if splanchnic efferent activity were elevated by carotid occlusion, stimulation still reduced discharge.
The effect of oxytocin and adrenaline on blood flow in the hind limb of the dog following chronic lumbar sympathectomy
Authors: Lloyd Sybil , Pickford Mary 
Published: December 2014

1. In a number of dogs the last two lumbar ganglia were removed unilaterally. At various dates up to the 56th day after operation the dogs were anaesthetized and the effect of oxytocin and adrenaline on hind‐leg blood flow studied. Oxytocin alone reduced leg flow in all dogs after operation.2. Until approximately day 11 after operation oxytocin given during an infusion of adrenaline increased leg blood flow, as it does in normal dogs not given adrenaline infusion. After that date it reduced the flow even during adrenaline infusion. The timing of this change suggests that the normal response to adrenaline depends on the presence of undegenerated nerve fibres.3. In one animal the sympathetic nerves were crushed between the last two lumbar ganglia and beyond the last, and hind‐leg blood flow frequently measured by means of venous occlusion plethysmography until day 204, when the animal was anaesthetized and acute observations made. Electrical stimulation of the sympathetic chain above the site of crushing caused a reduction in leg flow, indicating that at least some of the nerve supply had regenerated. However, oxytocin reduced leg flow when used alone and exerted no apparent effect in the presence of adrenaline.4. It is suggested that sympathetic nerves to vascular smooth muscle have a function or functions other than transmitter release and that when crushed nerves regenerate the functions do not recover at the same rate.
Activity of single neurones in the hypothalamic feeding centres: effect of gastric distension
Authors: Anand B. K. , Pillai R. V. 
Published: December 2014

1. Unit activity from neurones of hypothalamic ‘feeding’ and ‘satiety’ centres, and from adjacent hypothalmic regions, was recorded by means of steel micro‐electrodes inserted by a stereotaxic method, under Dial anaesthesia.2. The spike frequency of these neurones was observed during inflation of the stomach with intragastrically placed balloons, and during electrical stimulation of the gastric branches of the vagus. As control measures, distension of the peritoneal cavity and stimulation of a sensory nerve were also carried out. These tests were repeated after severing the gastric vagal branches.3. In fasted animals the frequency of spontaneous discharge was slower in the units of the satiety centre as compared with those of the feeding centre. The spike frequency of neurones in these two hypothalamic regions maintained an inverse relationship in all experimental situations.4. Distension of the stomach and stimulation of the gastric vagal branches increased the spike frequency of satiety neurones, decreased the spike frequency of feeding neurones, and did not produce any change in spike frequency of adjacent hypothalamic neurones. A few units in the lateral mammillary region also changed their spike frequency on gastric distension. These responses were abolished after severing the gastric nerves.5. The results suggest that distension of the stomach brings about satiation through vagal afferents activating the hypothalamic satiety mechanism.6. The role of this in the nervous regulation of food intake is discussed.
Pulmonary vasoconstriction in asphyxia during cross‐circulation between twin foetal lambs
Authors: Campbell A. G. M. , Cockburn F. , Dawes G. S. , Milligan J. E. 
Published: December 2014

1. The effect of asphyxia on pulmonary vascular resistance was measured in anaesthetized foetal lambs whose left lung was supplied with arterial blood from a twin, both still being attached to their placentas by intact umbilical cords.2. In foetal lambs of 91‐92 days gestation asphyxia of the recipient caused no pulmonary vasoconstriction so long as its left pulmonary artery was supplied with normal blood from a twin donor. Asphyxia of the donor caused pulmonary vasoconstriction in the unasphyxiated recipient; this was therefore wholly due to a local effect of the blood passing through the lung.3. In foetal lambs of 98‐142 days gestation asphyxia of the recipient caused a small degree of pulmonary vasoconstriction, even though the left pulmonary artery was supplied with normal blood from the twin donor. This vasoconstriction was abolished by administration of hexamethonium or by cutting the sympathetic nerves to the left lung.4. In mature foetal lambs pulmonary arterial inflow and venous outflow were measured simultaneously. Broncho‐pulmonary blood flow was less than 5% of total pulmonary flow. Pulmonary O2 consumption was 0·75 ± 0·11 ml./100 g.min, or about 5% of total foetal O2 consumption.
The behaviour of the sodium pump in red cells in the absence of external potassium
Authors: Garrahan P. J. , Glynn I. M. 
Published: December 2014

1. When red cells loaded with 24Na are incubated in balanced glucose salt solutions, the removal of external potassium reduces sodium efflux by about one third. Ouabain reduces the residual sodium efflux by about one half.2. The ouabain‐sensitive efflux of sodium into potassium‐free solutions is accompanied by an equal ouabain‐sensitive influx of sodium.3. If sodium in the external potassium‐free salt solution is progressively replaced with choline, both the ouabain‐sensitive sodium efflux and the ouabain‐sensitive sodium influx are reduced until, with only 5 m
M‐Na externally, both become very small.4. At sodium concentrations intermediate between 140 m
M and 5 m
M, ouabain‐sensitive sodium influx and ouabain‐sensitive sodium efflux remain equal within the limits of experimental error. The relation between the magnitude of the ouabain‐sensitive sodium exchange and the external sodium concentration is roughly linear.5. As the external sodium concentration is decreased beyond 5 m
M towards zero, ouabain‐sensitive sodium efflux increases again.6. In the presence of 5 m
M‐K, the ouabain‐sensitive sodium efflux is scarcely affected by replacing most of the external sodium with choline.7. In the presence of ouabain, sodium efflux is unaffected by external potassium and is little affected by replacing external sodium with choline.8. The results suggest that in the absence of external potassium the ouabain‐sensitive transport mechanism catalyses a one‐for‐one exchange of sodium ions across the cell membrane. The relation between this exchange and Ussing's classical ‘exchange diffusion’ is discussed.9. The exchange does not occur in the presence of external potassium at physiological concentrations.10. Calculations of sodium efflux were based on the specific activities of total cell sodium: separate experiments confirmed that these were the same as the specific activities of sodium lost to sodium‐free solutions. No evidence of a slowly exchanging sodium fraction was found.
The stoicheiometry of the sodium pump
Authors: Garrahan P. J. , Glynn I. M. 
Published: December 2014

1. When resealed ghosts containing adenosine triphosphate (ATP), magnesium and sodium were incubated in a medium containing potassium, ATP was hydrolysed vigorously by a ouabain‐sensitive mechanism. If the ghosts contained potassium instead of or in addition to sodium, and the external solution contained sodium but no potassium, there was little ouabain‐sensitive hydrolysis of ATP. As it is known that the ouabain‐sensitive ATPase in fragmented ghosts requires both sodium and potassium ions, these results show that the ATPase is activated by potassium externally and by sodium internally, and suggest that the ions activating the ATPase are the ions that are transported.2. Resealed ghosts containing ATP, magnesium and sodium were incubated in sodium‐free media containing potassium, with and without ouabain, and the rate of loss of sodium and rate of hydrolysis of ATP were measured. The hydrolysis of 1 molecule of ATP by the ouabain‐sensitive mechanism was accompanied by the ouabain‐sensitive loss of about 3 sodium ions.3. 24Na and 42K were used to measure sodium efflux and potassium influx in identical batches of fresh red cells under the same conditions and at the same time. Each flux was measured in the presence and absence of ouabain. The ratio (ouabain‐sensitive sodium efflux)/(ouabain‐sensitive potassium influx) was significantly greater than 1 (1·20 ± 0·01 and 1·35 ± 0·01 in two experiments). If a small fraction of the potassium influx represented a ouabain‐sensitive potassium: potassium exchange, the ratio of the numbers of ions moved in the sodium: potassium exchange catalysed by the pump must have been even further from unity.4. Resealed ghosts containing [γ‐32P]ATP, magnesium, 24Na and orthophosphate were incubated in balanced salt solutions with and without potassium and with and without ouabain. A comparison of sodium efflux, estimated from 24Na loss, with ATP hydrolysis, estimated from the formation of [32P]orthophosphate, showed that the sodium:sodium exchange in a potassium‐free medium was accompanied by little or no ouabain‐sensitive hydrolysis of ATP.5. Experiments on intact red cells loaded with 24Na showed that both sodium:sodium exchange in a potassium‐free medium, and sodium:potassium exchange in a medium containing potassium, were partially inhibited by oligomycin (1‐10 μg/ml.). Inhibition of the sodium:potassium exchange was not affected by raising the external potassium concentration.
Nature of thalamo‐cortical relations during spontaneous barbiturate spindle activity
Authors: Andersen P. , Andersson S. A. , Lømo T. 
Published: December 2014

1. The relation between thalamic and cortical spontaneous spindles was investigated in cats anaesthetized with barbiturates.2. Simultaneous recordings with multiple electrodes in the thalamus and cortex revealed a high correlation between thalamic and cortical spindle activity, both with regard to the occurrence of the spindles as well as to their individual waves, provided a critical location of the electrodes was secured. The results indicate a point‐to‐point relation between a group of thalamic cells and a small cortical area to which these cells project. In the spontaneous rhythm, the cortical columns are probably individually controlled by a thalamic rhythmic entity. This point‐to‐point relation was found in all the major sensory projection systems and in one thalamic ‘association’ nucleus and its corresponding ‘association’ cortex.3. Cortical barbiturate spindles appeared either as local spindles in a restricted cortical area or as compound spindles in several areas. Spindles recorded from electrodes separated by 2 mm or more were clearly different with regard to intraspindle wave frequency, duration, and the time of start and stop of the spindle. These differences increased with increasing distance between the electrodes, and were most pronounced when the corticograms of the two hemispheres were compared.4. Spontaneous spindle activity interfered with orthodromic transmission through n. ventralis posterolateralis (VPL) and medial geniculate nucleus (MG), judged by depression of the thalamic and cortical responses to peripheral nerve volleys or clicks. Such inhibition required the afferent volley to be delivered at a particular time of the spontaneous oscillations. Further, orthodromic volleys reset the rhythmic spindle waves in the appropriate thalamic and cortical areas.5. These findings lead to a new concept of the thalamic pace‐maker function. During barbiturate anaesthesia, small assemblages of thalamic neurones seem to have the ability to generate independent rhythmic discharges, and thereby control the rhythm of the particular cortical column to which this thalamic group projects.6. During barbiturate anaesthesia, many facultative pace‐makers seem to be present in the thalamus. The total number may be as large as 25,000‐35,000. Usually, many of these rhythmic thalamic units beat in synchrony or near synchrony.
The effect of vagal stimulation on plasma insulin and glucose levels in the baboon*
Authors: Daniel P. M. , Henderson J. R. 
Published: December 2014

1. The concentration of insulin in the blood of fifteen fasting baboons, anaesthetized with pentobarbitone sodium, was measured by a specific radio‐immunoassay method.2. The mean resting concentration of insulin was: inferior vena cava (IVC) 22 μu./ml. and splenic vein (after splenectomy) 140 μu./ml.3. Subdiaphragmatic stimulation of the cut right vagal trunk (at 10 impulses/sec, duration 1·5 msec, for 10 min) produced a mean increase of 50% over resting levels in IVC insulin concentration and an increase in splenic vein insulin of 30% over resting levels.4. The mean resting level of blood glucose in splenic vein blood was 89·4mg%, that in IVC blood was 79·4mg%. The difference is significant (P < 0·005).5. Vagal stimulation did not alter these glucose levels, so that insulin release following vagal stimulation is not secondary to hyperglycaemia.6. The increased insulin secretion following vagal stimulation might be expected to produce hypoglycaemia. Its failure to do so is discussed.
Micro‐iontophoretic studies on neurones in the cuneate nucleus
Authors: Galindo A. , Krnjević K. , Schwartz Susan 
Published: December 2014

1. Cuneate cells in anaesthetized cats were strongly excited by
L‐glutamate, and somewhat less by
D‐glutamate; cells which receive afferents from hair receptors were particularly sensitive.2. Glutamate could be used to demonstrate post‐synaptic inhibitory inputs from the dorsal column, the medial lemniscus and the frontal cortex.3. Many cuneate cells were also strongly excited by adenosinetriphosphate (ATP); this was probably due to the chelating action of ATP, as citric acid was also quite effective.4. γ‐Aminobutyric acid (GABA) readily blocked all forms of spontaneous and evoked activity, except antidromic invasion of cuneothalamic neurones; cells which receive proprioceptive afferents were particularly sensitive to GABA. Glycine had a comparable effect.5. Acetylcholine (ACh), catecholamines, histamine, 5‐hydroxytryptamine (5‐HT) and an extract containing substance P mostly had only weak depressant actions. Cholinergic and mono‐aminergic mechanisms are probably not very significant in the cuneate.6. These results are consistent with the possibility that glutamate and GABA (or glycine), or some closely related compounds, are the main excitatory and inhibitory transmitters in the cuneate nucleus.7. If ATP is released from afferent nerve endings, it could also play a significant role in excitation.
A study of synaptic transmission in the absence of nerve impulses
Authors: Katz B. , Miledi R. 
Published: December 2014

1. The axo‐axonic giant synapse in the stellate ganglion of the squid has been used to study synaptic transmission.2. When nerve impulses have been eliminated with tetrodotoxin, synaptic transfer of potential changes can still be obtained by applying brief depolarizing pulses to the presynaptic terminal.3. Suitably matched pulses are as effective as the normal presynaptic spike in evoking post‐synaptic potentials. The synaptic delay and the time course of the post‐synaptic potential are very similar to that in the normal preparation.4. The synaptic transfer (input/output) characteristic has been studied under different experimental conditions. With brief (1‐2 msec) current pulses, post‐synaptic response becomes detectable when the presynaptic depolarization exceeds about 30 mV. The post‐synaptic potential increases about tenfold with 10 mV increments of presynaptic depolarization.5. Calcium increases, magnesium reduces the slope of the synaptic transfer curve. The influences on this curve of (i) duration of the pulse, (ii) preceding level of membrane potential, (iii) position of recording electrode, (iv) rate of repetitive stimulation are described.6. After loading the synaptic terminal with tetraethylammonium ions, large inside‐positive potentials can be produced in the terminal and maintained for many milliseconds.7. By raising the internal potential to a sufficiently high level, synaptic transfer becomes suppressed during the pulse, and the post‐synaptic response is delayed until the end of the pulse.8. This observation is in accord with a prediction of the ‘calcium hypothesis’, viz. that inward movement of a positively charged Ca compound, or of the calcium ion itself, constitutes one of the essential links in the ‘electro‐secretory’ coupling process of the axon terminal.
The dependence of slow inward current in Purkinje fibres on the extracellular calcium‐concentration
Authors: Reuter H. 
Published: December 2014

1. In sodium‐free solution electrical constants of short Purkinje fibres were similar to those in Tyrode solution. Alterations in the extracellular calcium concentration ([Ca]o = 0; 1·8; 7·2 m
M) had no appreciable effect on these constants, unless the fibres were soaked in calcium‐free solution for more than 40 min.2. In sodium‐free solution without calcium there was constant or increasing outward current in response to sudden depolarizations (voltage‐clamp technique) over the whole voltage range ‐85 to +40 mV. In calcium‐containing solution initial outward current was followed by a slow change in current towards zero which was sometimes large enough to produce a net inward current. This current had a threshold in the voltage range ‐60 to ‐40 mV. It was not affected by alterations in the extracellular chloride or magnesium concentrations. The dependence on [Ca]o suggests that the slow inward current is carried by calcium ions.3. Negative slopes in the steady‐state current—voltage relations were obtained in fibres soaked in calcium‐containing solutions but were never observed in calcium‐free solution.4. The calcium equilibrium potential (ECa) was estimated to be about 150 mV, inside positive.5. In Tyrode solution the slow inward current was smaller than in sodium‐free solution and its threshold was shifted to about ‐20 to ‐10 mV. It was dependent on [Ca]o as in sodium‐free solution. It was increased by adrenaline and not affected by tetrodotoxin.6. It is concluded that calcium ions carry an appreciable membrane current in the inward direction when the membrane of the Purkinje fibre is depolarized. This calcium current may be involved in excitation—contraction coupling.
Peripheral modification of sensory nerve responses after cross‐regeneration
Authors: Robbins N. 
Published: December 2014

1. Chemical responses of skin and tongue, recorded in vivo from intact and self‐regenerated cutaneous or lingual nerves, were compared to responses from cutaneous nerves cross‐united with distal stumps of lingual nerves. Cross‐innervated tongue grafts were also studied.2. In contrast to normal tongue—nerve preparations, skin preparations usually showed responses to chemical stimulation with longer latency, higher threshold, and less variation of temporal pattern with diverse stimuli. These characteristics were similar when the nerve, having been cut, had regenerated.3. On chemical stimulation of the tongue, cutaneous nerves cross‐innervating the tongue often yielded records which were ‘gustatory’ by all criteria. Some responses with low threshold and short latency were also obtained from dorsal cutaneous nerves innervating tongue grafts.4. Thus, cutaneous nerves can serve the same role as gustatory nerves. The functional characteristics of these sensory neurones are not predetermined and must depend on the environment of the nerve endings.
The renal accumulation of urate and p‐aminohippurate in the rabbit
Authors: Møller Jesper V. 
Published: December 2014

1. During intravenous infusion of urate and p‐aminohippurate (PAH), the concentration of these two substances in cortex tissue of rabbit kidney exceeded the corresponding plasma concentration.2. Following the administration of 2,4‐dinitrophenol, fumarate, succinate, probenecid, and salicylate, accumulation of urate in kidney cortex and renal net secretion of urate were abolished. The accumulation and secretion of PAH were only partially inhibited after infusion of these compounds.3. The renal accumulation of urate was reduced in relation to the inhibition of urate excretion during infusion of various amounts of PAH.4. The combined data indicate a correlation between renal accumulation and excretion of urate and PAH. It appears likely that accumulation of urate and PAH in vivo is due to tubular secretion of these two substances, although in the case of urate a small contribution from tubular reabsorption of urate cannot be excluded.