bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cholinergic mechanisms in the caudate nucleus
Authors: McLennan H. , York D. H. 
Published: December 2014

1. Acetylcholine (ACh), and a number of cholinomimetic and cholinolytic agents, have been applied to single neurones of the caudate nucleus, and the effects compared with those produced by stimulation of nucleus ventralis anterior thalami (VA).2. Neurones responding by excitation following ACh and VA stimulation, and others depressed by both ACh and VA stimulation have been observed. The two types of cell are located in different regions of the nucleus.3. Both types of ACh effect, and the responses to VA stimulation, are prevented by atropine.4. Taken with the earlier observation that the release of ACh from the caudate can be enhanced by VA stimulation, it has been suggested that the present results indicate a final cholinergic link in the pathway from VA to caudate.
Discharge patterns of principal cells and interneurones in lateral geniculate nucleus of rat
Authors: Burke W. , Sefton Ann Jervie 
Published: December 2014

1. The cells of the lateral geniculate nucleus of the rat are classified into one of two distinct groups on the basis of their responses to a single shock to optic nerve or visual cortex. The distinctive difference between these two groups is that the P cells (87% of all cells) responded with short bursts of 1‐5 spikes, whereas the I cells (13%) responded with long bursts of about 10 spikes. Both groups give recurring bursts at intervals of 100 msec or more for a total duration of up to about 5 sec.2. The majority of P cells (75%) have a lower threshold for late firing than for early firing. The majority of I cells (62%) have about the same threshold and all I cells have very low thresholds.3. To stimulation of the optic nerve the mean latency of the first spikes of all P cells is 4·4 msec. The mean latency of the first spikes of all I cells is 5·8 msec. The latency of the earliest spike in an I cell is 0·9 msec longer than the earliest spike in a P cell.4. To stimulation of the visual cortex the latency of the earliest spike in an I cell is 1·0 msec longer than the earliest spike in a P cell. Most P cells (78%) respond with either very short latency (less than 1·7 msec) or with a wave form characteristic of antidromic invasion or both. No I cell has either of these characterstics.5. It is concluded that P cells are principal cells projecting to visual cortex and that I cells are interneurones.
Oxygen consumption during pouch development of the macropod marsupial Setonix brachyurus
Authors: Shield John 
Published: December 2014

1. Measurements of O2 consumption at 9 or 10 temperatures in the 20‐40° C ambient temperature range were made on joeys with ages selected to cover the 180‐day period of pouch occupancy.2. The rate of O2 consumption of joeys younger than 100 days increased directly with ambient temperature.3. After 100 days of age the O2 consumption rate at low temperatures rose and at about 140 days of age a constant rate was maintained over the full ambient temperature range.4. Heat transfer from joey to mother commenced after 100 days of age.5. At 150‐180 days of age the rate of O2 consumption at 20° C was approximately 12 times greater than at ages less than 100 days. A thermal neutral zone was established in the range 32‐36° C by joeys older than 150 days.6. At the usual pouch temperature of 36·5° C, O2 consumption per unit wet body weight rose from 12 ml./kg.min at birth to 17 ml./kg.min at the end of pouch life. On a unit dry body weight basis it fell from 120 to 56 ml./kg.min. This decline parallels the decrease in growth rate.
The diffusion of radiopotassium across intercalated disks of mammalian cardiac muscle
Authors: Weidmann Silvio , Hodgkin A. L. 
Published: December 2014

1. Experiments were performed to determine whether intercalated disks represent a high or a low resistance to the diffusion of K ions.2. Bundles of sheep ventricular fibres, 0·6‐0·8 mm thick and 7‐11 mm long, were pulled through a hole in a partition. One half was charged by radiopotassium (K*); the other half was washed by inactive Tyrode solution.3. A steady state with respect to the distribution of K* along the bundle was reached 6 hr after the exposure to radioactivity.4. On the ‘washed’ side [K*] fell along a relatively smooth curve and did not tend to the value zero towards the cut end of the bundle. The average space constant for the decrease of [K*] was 1·55 mm, corresponding to a distance of about 12 × the length of a cell. This indicates that the disk resistance is low and that the fibres are healed over at their cut ends.5. Rhythmical contraction had no detectable effect on the space constant. This may mean either that shortening and thickening of a cell does not effectively mix its content, or that stirring goes on even in resting cells.6. On the assumption of mixing between disks the average resistance of 1 cm2 of disk to the movement of K ions is 3 Ω. If there is no mixing this value would be even lower.7. The assumption that K* distribution within the ‘washed’ half of the bundle is a consequence of cell‐to‐cell rather than of extracellular movement is supported by the results of several control experiments.8. It is concluded that the propagation of the cardiac action potential is possible by local circuit currents.
The effect of hyperthermia and localized heating of the anterior hypothalamus on the sympatho‐adrenal system of the ox (Bos taurus)
Authors: Robertshaw D. , Whittow G. C. 
Published: December 2014

1. Arterial plasma catecholamine concentrations, rectal temperatures and respiratory rates were measured in the unanaesthetized ox in a cool environment (15/11·5° C dry bulb/wet bulb (
D.B./W.B.) in a hot, dry environment (40/22° C), in a hot, humid environment (40/39·1° C) and during localized heating of the hypothalamus.2. There was no significant difference in the plasma catecholamine levels of animals exposed to a cool environment (15/11·5° C) and to a hot, dry (40/22° C) environment.3. When the animals became hyperthermic in the hot, humid environment, considerable increases in the plasma levels of adrenaline and smaller increases in noradrenaline concentration occurred.4. Bilateral adreno‐medullary denervation abolished the changes in plasma catecholamine levels associated with hyperthermia.5. Localized heating of the anterior hypothalamus in either a cool or a warm environment did not result in any change in plasma catecholamine levels.6. It was concluded that the source of the increased levels of plasma catecholamines during hyperthermia was the adrenal medulla and that the stimulus for their release was a nervous one rather than direct chemical or thermal stimulation of the adrenal medulla. The cause of the increased sympatho‐adrenal activity was not apparent, but neither thermal stimulation of cutaneous and hypothalamic receptors nor the associated changes in respiratory activity seemed to be implicated in the response.
Energy barriers to sodium extrusion from sodium‐rich kidney cortex slices
Authors: Smyth Honor 
Published: December 2014

1. Rat and guinea‐pig kidney cortex slices were made Na‐rich by leaching in cold NaCl and then allowed to recover in Ringer solution at 30 or 25° C. Net Na extrusion was systematically decreased by the use of re‐immersion media with constant Na and diminishing K, or with constant K and increasing Na, and the energy requirements for Na extrusion under these conditions were calculated.2. The critical energy barrier at which no net Na loss can be achieved was somewhat lower in these tissues than found by other authors for frog sartorius muscle.3. Inclusion of pyruvate or insulin and lactate in the recovery fluid had no effect.4. Methylsulphate apparently enters renal cells during incubation and is therefore unsuitable for use with this tissue as a source of impermeant anion.
Synaptic stimulation superimposed on motoneurones firing in the ‘secondary range’ to injected current
Authors: Granit R. , Kernell D. , Lamarre Y. 
Published: December 2014

1. This paper extends the work on the ‘primary range’ of firing (Granit, Kernell & Lamarre, 1966), in lumbar motoneurones to the ‘secondary range’. By definition the latter begins when, with stronger currents, the linear curve relating firing rate to injected current in the primary range undergoes a fairly sudden increase of slope.2. It was shown that motoneurones firing at the higher frequencies of the secondary range were partially inactivated. Yet such firing rates were within the physiological range.3. Algebraical summation of firing rates, when present in the secondary range, implied at the same time that the synaptic amount added was diminished by comparison with what it had been within the primary range.4. Superimposed synaptic excitatory stimuli did not (as in the ‘primary range’) regularly add their effect algebraically on to the rate of firing achieved by injected currents alone. More commonly the synaptic effect of the constant input underwent a progressive increase throughout the secondary range.5. Superimposed inhibitory stimuli regularly reduced the slope constant as determined by trans‐membrane current alone and, by counter‐acting inactivation, made the motoneurone approach the mode of firing characteristic of the ‘primary range’.6. The latter finding emphasizes the significance of analysing firing motoneurones with the aid of ‘slope constants’ and provides inhibition with a new role in the integrative behaviour of motoneurones, as considered in the Discussion.
A species comparison of the effects of changing perfusion pressure on blood flow and metabolic heat production in the myocardium
Authors: Grayson J. , Parratt J. R. 
Published: December 2014

1. A heated thermocouple technique (internal calorimetry) has been used to investigate blood flow and heat production responses in the myocardium to changing blood pressure in monkeys, dogs, rabbits, guinea‐pigs and rats.2. Perfusion experiments (isolated guinea‐pig and dog hearts) showed linear relations between conductivity increment and coronary blood flow up to 1·5 ml. g−1 min−1 (dog heart perfused with blood) and 5 ml. g−1 min−1 (guinea‐pig heart perfused with saline). This relation was the same in the beating and non‐beating heart.3. In rabbits, guinea‐pigs and rats the relation between flow (conductivity increment) and blood pressure was linear. In contrast, in monkeys and dogs, over the range 100‐40 mm Hg, little change in blood flow occurred. After the injection of procaine around the stellate ganglion, the relation between pressure and flow in both species was linear. It is suggested that the constancy of blood flow displayed in the monkey and dog over this blood pressure range was due to the activity of adrenergic vasodilator fibres.4. Evidence is adduced to show an increased myocardial heat production when systemic arterial pressure fell below about 60 mm Hg. This was not affected by cardiac denervation. The possible significance of this effect is discussed.
Dynamic and static contributions to the rhythmic γ activation of primary and secondary spindle endings in external intercostal muscle
Authors: von Euler C. , Peretti G. 
Published: December 2014

1. In cats anaesthetized with sodium pentobarbital 160 external intercostal muscle spindle afferents were identified by their pause in response to ventral root stimulation; the internal intercostal muscle was denervated.2. In order to assignate the afferents to either primary or secondary endings they were tested for their responsiveness to vibration (Bianconi & Van Der Meulen, 1963). The maximal frequency which they were able to follow regularly for at least four cycles, termed ‘critical frequency’, was determined.3. The endings fell into two groups: low‐f (frequency) sensitive endings with critical frequencies below 400 c/s and high‐f sensitive endings with critical frequencies above 400 c/s. The latter were regarded as primary endings and the former as secondary ones.4. The manner in which the spindle endings resumed activity after a pause produced by shocks to the ventral root, i.e. whether ‘phasic’ or ‘tonic’ (Granit & Van Der Meulen, 1962) was studied in all the spindle afferents.5. All the secondary (low‐f sensitive) endings were ‘tonic’ except three for which the determination of critical frequency was questionable. Both ‘tonic’ and ‘phasic’ properties were found among the primary (high‐f sensitive) endings.6. The majority of the secondary endings (74%) showed inspiratory rhythmic fusimotor activation in parallel with the skeletomotor contraction as did the primary endings (79%).7. Fifty‐seven spindle endings which all showed marked rhythmic inspiratory γ activation were tested for respiratory variations in their dynamic responses to steady stretch and length changes introduced at low repetition rates.8. The results indicate that both ‘dynamic’ and ‘static’ γ fibres are represented among the rhythmic γ fibres controlling primary muscle spindle endings, whereas rhythmic activation of secondary endings seems to be mediated only by ‘static’ fibres.
Responses in the inferior olive to stimulation of the cerebellar and cerebral cortices in the cat
Authors: Armstrong D. M. , Harvey R. J. 
Published: December 2014

1. Extracellular field potentials and single unit responses have been recorded from the inferior olive of the cat following stimulation of the surface of the contralateral paramedian lobule of the cerebellum, and of the ipsilateral cerebral cortex.2. Cerebellar stimulation results in antidromic invasion of inferior olivary neurones via the climbing fibres. These responses are followed by synaptic discharges which may be generated through climbing fibre recurrent collaterals.3. Precise histological controls have shown that these responses to stimulation of the paramedian lobule are located in the ventral lamella of the principal olive.4. Unifocal stimulation of the sensori‐motor cortex with surface‐anodal pulses evokes synaptically generated discharges of neurones in the ventral lamella, with a latency of 8‐9 msec. The area of cortex yielding responses has been mapped at chosen stimulus intensities and the limitations of the maps have been discussed.5. It has been shown that the initial excitatory responses obtained from either cortex are followed by an inhibition which lasts about 100 msec, and gives way to a period of recovery or facilitation. This, in turn, is succeeded by a further period of inhibition. Possible neural substrates for these changes have been discussed.
The effects of stimulating cutaneous and splanchnic afferents on cerebellar unit discharges
Authors: Newman P. P. , Paul D. H. 
Published: December 2014

1. Electrical stimulation of the right splanchnic nerve evoked the discharge of single units in the right cerebellar cortex of the anaesthetized cat. The majority of the units also responded to electrical stimulation of an area of skin on the right side of the anterior abdominal wall. The units were all located in lobules Vb‐f (culmen) of the anterior lobe of the cerebellum, lateral to the paravermian vein.2. The response evoked by a conditioning stimulus (C) to one afferent pathway was followed by a period during which the response of a testing stimulus (T) to another pathway was diminished or absent. Diminished responsiveness was indicated by a reduction in the probability of the unit firing and a prolongation of the mean latency of the test response.3. The effects of interaction depended on the interval between conditioning and testing stimuli and could be demonstrated with intervals as long as 150 msec. Complete blocking of the test response occurred with C—T intervals between 30 and 40 msec; at intervals shorter than 25 msec the effects were less intense.4. If the C—T interval was constant, increasing the strength of the conditioning stimulus or decreasing the strength of the testing stimulus produced in each case a more powerful and prolonged inhibitory effect on the test response.5. When two successive stimuli were applied to the splanchnic nerve, the discharge evoked by the first stimulus was invariably followed by complete block of the response to the second stimulus over a wide range of intervals.
Observations on the potential across the rumen of the sheep
Authors: Ferreira H. G. , Harrison F. A. , Keynes R. D. , Nauss A. H. 
Published: December 2014

1. The electric potential difference between rumen contents and jugular venous blood was measured in anaesthetized sheep. In order to investigate the effect on the potential of changing the ionic concentrations within the rumen, the digesta were removed from the rumen and various salt solutions were substituted. The reticulo‐rumen sac was isolated before the experiment by ligation of the oesophagus and the reticulo‐omasal junction.2. The observation of Dobson & Phillipson (1958) that the rumen contents are normally of the order of 30 mV negative to the blood was confirmed.3. For potassium concentrations between 25 and 100 m
M the potential at constant [Na+] varied linearly with log [K+]. With sulphate as the anion, the slope for a 10‐fold concentration change was 39·7 ± 3·0 mV when [Na+] was around 50 m
M. The slope showed a tendency to increase when [Na+] was lowered, and to decrease when [Na+] was raised.4. When chloride was substituted for sulphate, both the slope and the absolute size of the potential were slightly reduced.5. When the sodium concentration was varied at constant [K+], the potential increased as an approximately linear function of [Na+]. At around 10 m
M‐K the mean slope was 0·32 ± 0·07 mV/m
M; at the highest potassium concentrations it fell to 0·13 ± 0·05 mV/m
M.6. In most of these experiments isotonicity was maintained with sucrose. The results of a few tests in which Li+ was substituted for Na+ or K+ suggested that the rumen epithelium behaves in a relatively inert fashion towards this ion.
The potential and short‐circuit current across isolated rumen epithelium of the sheep
Authors: Ferreira H. G. , Harrison F. A. , Keynes R. D. 
Published: December 2014

1. A technique is described for working with isolated sheets of rumen epithelium. Epithelium was obtained at operations for rumen fistulation or in acute experiments and was rapidly mounted between two cone‐shaped chambers each of which held 40 ml. of bathing fluid. The fluids were gassed with 95% O2/5% CO2 and 20 cm2 of epithelium was exposed to the fluids.2. Electrical measurements were made of (a) the potential generated across the epithelium, (b) the short‐circuit current which flowed and (c) the resistance of the epithelium.3. The results are grouped according to the composition of the sheep Ringer solution used to bathe the epithelium. The most stable preparation was obtained when the solutions contained 5 m
M each of glucose, acetate, propionate and butyrate as well as bicarbonate and phosphate buffers.4. In Cl− media, the average initial p.d., short‐circuit current (s.‐c.c.) and resistance were 9·3 mV, 11·6 μA/cm2 and 1156 Ω. cm2 respectively. Higher values of 17·6 mV, 17·3 μA/cm2 and 1501 Ω. cm2 were recorded in SO42- media. In both media, the s.‐c.c. declined at approximately 1·5 μA/cm2.hr and preparations were suitable for study over periods from 4 to 6 hr.5. When the concentration of potassium was varied on either side of the epithelium at constant [Na+], the potential showed a linear relation with log [K+] for both sides of the epithelium.6. Changing the sodium concentrations at constant [K+] on either side of the epithelium caused negligible alterations in the potential.7. Exclusion of sodium from the media bathing both sides of the epithelium abolished the potential and s.‐c.c.8. The addition of ouabain to the blood side of the preparation abolished the potential and s.‐c.c. whereas on the rumen side these parameters were unaffected.
Monoamine oxidase inhibition: effect on 5‐hydroxytryptamine output from perfused third ventricle and body temperature
Authors: El Hawary M. B. E. , Feldberg W. , Lotti V. J. 
Published: December 2014

1. In cats anaesthetized with pentobarbitone sodium the third ventricle was perfused with artificial c.s.f., the effluent was collected in 30 min samples and assayed for 5‐hydroxytryptamine (5‐HT) on the rat stomach‐strip preparation. Rectal temperature was monitored continuously.2. On perfusion of artificial c.s.f. through the third ventricle, small amounts of 5‐HT appeared in the effluent; the amounts decreased with successive samples.3. When tranylcypromine (Parnate), an inhibitor of amine oxidase, was added to the perfusion fluid and perfusion was continued, the 5‐HT output increased. This increase was associated with shivering and a rise in temperature which was not, however, maintained.4. When tranylcypromine was injected intraperitoneally, during the fall in temperature produced by the pentobarbitone sodium anaesthesia, the 5‐HT output also increased, shivering occurred and the fall in temperature was halted or reversed. The effect on temperature was maintained.5. When the cat was killed and perfusion was continued, the 5‐HT output, already elevated by the tranylcypromine before death, increased even further in the next few samples.
The reflex effects of alterations in lung volume on systemic vascular resistance in the dog
Authors: Daly M. de Burgh , Hazzledine Julie L. , Ungar A. 
Published: December 2014

1. The reflex effects of alterations in lung volume on systemic vascular resistance have been studied in anaesthetized dogs under conditions in which the systemic circulation was perfused at constant blood flow. The pressures in the isolated perfused carotid sinuses and aortic arch, and the arterial blood PO2 and PCO2 were maintained constant.2. A maintained inflation of the lungs produced by injection of air into the trachea caused a fall in systemic arterial perfusion pressure, indicating vasodilatation. The size of the systemic vasodilator response varied directly with the pressure and volume of gas used to inflate the lungs. A similar effect was observed when the tidal volume of lungs ventilated by an intermittent positive pressure was increased.3. Collapse of the lungs by creating a pneumothorax in closed‐chest spontaneously breathing animals evoked a systemic vasoconstrictor response which was reversed when the lungs were re‐expanded.4. These vasodilator responses were abolished by dividing the pulmonary branches of the thoracic vagosympathetic nerves. Evidence is presented that the afferent fibres run in the cervical vagosympathetic nerves and through the stellate ganglia.5. The responses were unaffected by atropine, but were abolished by hexamethonium, guanethidine and by bretylium tosylate, indicating that they are mediated via the sympathetic nervous system.6. Evidence is presented that the lungs are a constant course of afferent impulses inhibiting the ‘vasomotor centre’, and that the lung inflation—systemic vasodilator reflex is a potential mechanism operating in eupnoeic breathing.
The effect of noradrenaline on the permeability of depolarized intestinal smooth muscle to inorganic ions
Authors: Jenkinson D. H. , Morton I. K. M. 
Published: December 2014

1. Radio‐isotopes have been used to study the effect of noradrenaline on the permeability of the taenia of the guinea‐pig caecum to inorganic ions. The preparations were bathed at either 10 or 20° C in solutions containing a high concentration of potassium, in order to depolarize the fibres and so avoid ionic movements secondary to changes in membrane potential.2. Under these conditions noradrenaline increased both inward and outward fluxes of potassium whilst having little effect on the exchange of chloride.3. No effect of noradrenaline on the uptake of sodium could be detected, whereas carbachol (carbamyl choline chloride), applied under identical conditions, caused a significant increase at a concentration chosen to match the effect of noradrenaline on potassium exchange.4. These results are discussed in relation to the hypothesis that an increase in potassium permeability contributes to the inhibitory actions of noradrenaline on intestinal smooth muscle.