bluuebunny/crossref_metadata_2025_split huggingface dataset:
Periodic components in steady‐state activity of cuneate neurones and their possible role in sensory coding
Authors: Amassian Vahé E. , Giblin Denis 
Published: December 2014

1. Individual cuneate touch, touch‐hair and proprioceptive neurones often display periodic components in their steady‐state resting or evoked discharges. The periods may be visible in the interspike interval distribution or may be revealed only by the expectation density function. Several levels of complexity were identified; from one to four mutually prime, periodic components may be present, with or without an aperiodic component.2. The periodic components usually depend on the peripheral input, as shown by their introduction or modification by peripheral stimulation and by their disappearance following deafferentation.3. The coefficient of variation of periodic discharges by touch and touch‐hair neurones was 0·024‐0·23 (aperiodic, driven discharges usually had CV's of 0·64‐0·77).4. The occasional recording extracellularly of a periodically occurring, unitary prepotential preceding the spike and the intracellular recording of a periodic, ‘giant’, unitary e.p.s.p. imply that an individual periodic impulse in an afferent fibre may elicit a post‐synaptic discharge. Even with threshold stimulation, the timing of post‐synaptic discharge was quite precise.5. The periodicity did not appear to reflect a cycle of subnormality intrinsic to the post‐synaptic neurone, because a current pulse injected through a micro‐electrode lying just external to the membrane could block the next expected periodic discharge, but did not continuously vary its waiting time.6. A mathematical model that fits some discharge patterns predicts the interval distribution from an over‐all probability of response to the periodic input: each periodic afferent impulse is treated as an independent trial resulting in success (post‐synaptic discharge) or failure. Some other interval distributions are fitted by a ‘conditioned’ model in which a success reduces the probability of response at the next periodic trial.7. The discussion includes a hypothesis of tactile discrimination, in which the output of a sensory relay, e.g. cuneate neurone, signals both the number of afferent fibres converging upon it and the afferent period in each.
Factors influencing plasma renin and angiotensin II in the conscious pregnant ewe and its foetus
Authors: Pipkin Fiona Broughton , Lumbers Eugenie R. , Mott Joan C. 
Published: December 2014

1. Plasma renin (measured in the presence of additional substrate) was significantly higher (10·7 ± 1·1
S.E. of mean ng/ml.hr) in foetal lambs of 111–144 days gestation age (full term 147 days) than in their mothers (1·5 ± 0·2 ng/ml.hr
S.E. of mean, P < 0·001) but plasma angiotensin II concentrations were in the same range (ewe 47·3 ± 6·6
S.E. of mean, foetus 47·4 ± 14·1
S.E. of mean pg/ml.). The endogenous velocity of renin production by foetal plasma was also greater than that of maternal plasma.2. Foetal plasma [Na+] (137 ± 0·8
S.E. of mean m‐equiv/l.), was lower than that in the ewe (142 ± 1·5 m‐equiv/l.
S.E. of mean, P < 0·01).3. Foetal plasma renin in lambs of less than 120 days gestation was lower (9·2 ± 2·7
S.E. of mean ng/ml.hr) than that in lambs of over 130 days gestation (12·6 ± 2·6 ng/ml.hr
S.E. of mean, P < 0·01). Foetal plasma [K+] (3·8 ± 0·1
S.E. of mean m‐equiv/l.) was also lower in lambs of less than 120 days gestation than in those over 130 days (4·1 ± 0·1
S.E. of mean m‐equiv/l., P < 0·001).4. When small volumes of blood (≤ 3% of blood volume) were withdrawn from foetal lambs, plasma renin increased. The% increase of plasma renin in hypoxaemic foetal lambs was significantly less (P < 0·05) than in control lambs. At the end of 60 min hypoxaemia, arterial pressure and plasma [K+] were significantly higher in hypoxaemic than in control foetal lambs.5. During foetal hypoxaemia, plasma angiotensin II concentration increased concurrently with plasma renin.6. Bilateral nephrectomy was performed in two foetal lambs. Plasma renin fell to very low levels and angiotensin II became undetectable.7. Adrenaline (∼.0·42 μg/min.kg
I.V.) infused into the foetus did not alter foetal plasma renin. When adrenaline was infused into the ewe (∼0·26 μg/min.kg) maternal plasma renin increased. Maternal infusion of adrenaline raised foetal plasma renin significantly more (P < 0·05) than foetal infusion.8. It is concluded that the foetal kidney is the major source of foetal renin in the last quarter of gestation and that renin release is stimulated by very small reductions of blood volume. Hypoxaemia does not augment renin release and cannot be responsible for high levels of renin and angiotensin associated with vaginal delivery.
Linear analysis of membrane conductance and capacitance in cardiac Purkinje fibres
Authors: Hellam D. C. , Studt J. W. 
Published: December 2014

1. The membrane capacitance and slope conductance of sheep cardiac Purkinje tissue were examined under conditions of constant and slowly changing voltage within the potential range: −70 to −100 mV. Data were secured by applying constant current pulses, or by imposing ramp commands or small changes in holding potential under voltage clamp control.2. The electrical measurements, combined with light and electron microscopic data on preparation structure, were interpreted with the aid of a core‐conductor model that permits quantitative representation of cleft‐ and lateral surface membranes for individual preparations (Hellam & Studt, 1974).3. The analysis led to the following conclusions. The slope conductance of unit membrane area (Gm) is quite low in the normal resting potential range; at −80 mV the value is 0·09 mmho/cm2. Gm exhibits a marked decline with depolarization in the region positive to −88 mV, but only slight voltage‐dependence at more negative potentials within the range of present observations. The capacitance of unit membrane area (Cm), from voltage ramp data collected near −90 mV, is 0·9 μF/cm2.4. Comparison with results of earlier studies indicates that the differences between present and previous experimental estimates of these membrane characteristics result from differences in modelling and structural analysis of tissue preparations.
The time‐dependent and dose‐dependent effects of caffeine on the contraction of the ferret heart
Authors: Chapman R. A. , Léoty C. 
Published: December 2014

1. Trabeculae isolated from ferret heart and from other mammalian hearts have been mounted in a way that enables the tension generated to be measured while the composition of the bathing fluid is rapidly altered.2. Application of caffeine to these trabeculae initiates a rapid transient contracture and depresses the strength of regularly evoked heart beats.3. The strength of the contractures, the rate of tension development and the rate of spontaneous relaxation are all increased by raising the concentration of the applied caffeine.4. The strength of the caffeine contracture is relatively unaffected by changes in the bathing Na+, K+ or Ca2+ concentrations, but is reduced by exposure to the free‐base form of local anaesthetics.5. Lowering of the temperature has complex effects on the amplitude of the caffeine contracture due to the differing temperature sensitivities of the contraction and spontaneous relaxation.6. Following a caffeine contracture, a period of perfusion by caffeinefree solution is required before a full‐sized contracture can be evoked by the re‐application of caffeine. This re‐priming of the caffeine contracture has a sigmoidal time course that can be fitted by a two compartment model. The rate constants of the filling of each of the compartments can be obtained analytically, and are found to be increased by raising the extracellular calcium concentration, [Ca]o, by stimulating the preparation or by raising the temperature. Reducing the [Na]o or raising the [K]o has little effect on these processes.7. The presence of traces of caffeine in the perfusing fluid between the conditioning and test challenges with the caffeine contracture solution reduces the extent of the re‐priming without much affecting its rate.8. The behaviour of several model systems have been compared with that of the heart with the aid of an analogue computer. A four compartment closed system has been found to simulate the results presented in this paper.9. It appears that caffeine has its effects by acting to increase the rate of release of activator calcium from one part of a non‐homogeneous intracellular relaxing system present within the mammalian heart, which is likely to be the sarcoplasmic reticulum.
ATP hydrolysis associated with an uncoupled sodium flux through the sodium pump: evidence for allosteric effects of intracellular ATP and extracellular sodium
Authors: Glynn I. M. , Karlish S. J. D. 
Published: December 2014

1. A method has been developed for regenerating [γ32P]ATP of constant specific activity within resealed red cell ghosts, and for measuring its hydrolysis. The method may be used to follow the hydrolysis of ATP at concentrations down to 1 μ
M, and for periods long enough for the ATP at these very low concentrations to turn over several hundred times.2. Using this method we have been able to show that the ‘uncoupled’ efflux of Na caused by the Na pump when resealed red cell ghosts are incubated in (Na + K)‐free media is associated with a hydrolysis of ATP. The stoicheiometry is roughly 2‐3 Na ions expelled per molecule of ATP hydrolysed.3. Measurements of ATP hydrolysis and Na efflux as functions of intracellular ATP concentration have shown that uncoupled Na efflux, and its associated ATP hydrolysis, are saturated at intracellular ATP concentrations in the region of 1 μ
M.4. Measurement of ATP hydrolysis as a function of ATP concentration in resealed ghosts incubated in a K‐containing medium gave a complicated activation curve suggesting the involvement of high‐affinity (Km ca. 1 μ
M) and low‐affinity (Km ca. 100 μ
M) sites.5. When resealed ghosts containing about 1 μ
M‐ATP were incubated in a Na‐free or in a high‐Na medium, the addition of K to the medium reduced the rate of ouabain‐sensitive ATP hydrolysis.6. Ouabain‐sensitive ATP hydrolysis in resealed ghosts incubated in K‐free choline media was inhibited by external Na at low concentrations (Ki < 1 m
M), but this inhibition was reversed as the external Na concentration was further increased.7. The results show that uncoupled Na efflux may be thought of as the transport mode associated with Na‐ATPase activity, just as Na‐K exchange is the transport mode associated with (Na + K)‐ATPase activity. The significance of the differences between uncoupled Na efflux and Na‐ATPase activity, on the one hand, and Na—K exchange and (Na + K)‐ATPase activity, on the other, is discussed.
Prolonged inactivation of cortical pyramidal tract neurones in cats by distension of the carotid sinus
Authors: Coleridge Hazel M. , Coleridge John C. G. , Rosenthal Fred 
Published: December 2014

1. We have investigated the effects of stimulating carotid sinus baroreceptors upon the activity of single cortical pyramidal tract cells (PT‐cells) in anaesthetized cats.2. Extracellular potentials were recorded from PT‐cells, which were driven orthodromically (1/sec) by stimulating thalamic nuclei (N. ventralis lateralis, N. ventralis posterolateralis) or afferent nerves in the contra‐lateral forepaw. Baroreceptors were stimulated by inflating small balloons placed in the bifurcations of one or both common carotid arteries.3. Distension of the carotid sinus caused a prolonged depression of the orthodromically evoked discharge of eighteen of thirty‐two PT‐cells, the effect ranging from a 15% reduction in firing to complete cessation of activity (average reduction, 39%). The depression of firing outlasted the period of balloon inflation by an average of 85 sec; in some experiments inhibition persisted for as long as 2‐3 min.4. Inflation of the balloon caused a reflex fall in arterial pressure (mean decrease, 29 mmHg), pressure reverting to the control level as soon as the balloon was deflated. Single fibre recording from the carotid sinus nerve confirmed that stimulation was confined to baroreceptors and that carotid chemoreceptors were unaffected by balloon distension.5. Depression of PT‐cell activity could not be explained simply by a fall in cerebral blood flow resulting from the reflex fall in arterial blood pressure. When a comparable or greater degree of hypotension was produced by bleeding or peripheral vagal stimulation, PT‐cell firing fell in a third of experiments but reverted immediately to the control level when arterial pressure was restored. Thus some factor other than a decrease in cerebral perfusion pressure was responsible for the prolonged inhibition evoked by carotid sinus distension.6. Our results are consistent with the hypothesis that baroreceptor input to the reticular formation exerts an ascending influence on cortical mechanisms, with prolonged inhibitory effects comparable to those previously demonstrated at spinal level.
Testicular blood flow and a study of the testicular venous to arterial transfer of radioactive krypton and testosterone in the rhesus monkey
Authors: Einer‐Jensen N. , Waites G. M. H. 
Published: December 2014

1. Testicular blood flow (ml. 100 g−1.min−1; mean ±
S.E. of the mean) measured in monkeys by 133Xe clearance was 15·9 ± 1·2 (twenty‐six estimations on three monkeys; six testes) within 15 min of anaesthesia and 7·5 ± 0·8 (twelve estimates; four monkeys, eight testes), after 1‐2 hr of anaesthesia; and, when measured by 85Kr clearance in the second hour of anaesthesia was 9·1 ± 3·7 (seven estimates; four monkeys, four testes). Testicular temperature was 32·9 ± 0·2° C (mean ±
S.E. of mean) when deep body temperature was 37·2 ± 0·2° C.2. Blood flow in the caput epididymidis was 27·4 ± 2·1 ml. 100 g−1.min−1 (mean ±
S.E. of mean; four estimates).3. Radioactivity accumulated in the ipsilateral testis and epididymis but not in the contralateral tissues, during the infusion of 85Kr saline into the testicular veins.4. During [3H]testosterone infusions into the testicular veins, radioactivity was consistently higher in ipsilateral testicular arterial plasma than in plasma withdrawn simultaneously from the aorta in four of five experiments with no difference in one. After two such infusions, the radioactivity was up to 5 times greater in the ipsilateral testis and epididymis than in the contralateral tissues.5. During one infusion of [125I]bovine serum albumin into the testicular veins, there was no accumulation of radioactivity in the ipsilateral tissues.6. Testosterone concentrations (ng.ml−1; mean ±
S.E. of mean) in plasma from seven anaesthetized monkeys which were sexually experienced were: testicular vein 53·22 ± 8·03 (eight estimates); testicular artery, 4·58 ± 0·94 (14); saphenous vein, 3·81 ± 0·68 (14). The corresponding values from four sexually inexperienced monkeys were 25·27 ± 2·11 (12); 2·89 ± 1·99 (12); aorta 2·76 ± 0·57 (12).7. The results are discussed as evidence for vascular exchange of molecules between the testicular veins and artery in the spermatic cord.
Electrophysiological study of the antiluminal membrane in the proximal tubule of Necturus: effect of inorganic anions and SCN−
Authors: Anagnostopoulos Takis 
Published: December 2014

1. A study has been made of the effects of anionic substitutions on the electrical potential difference (p.d.) and conductance characteristics of the antiluminal (peritubular) membrane of the proximal tubule of Necturus kidney. The tubular lumina were filled with oil in order to minimize potential and conductance contributions from luminal membrane and from paracellular shunt pathway.2. Isosmotic substitutions, [A]o for [Cl]o, produced the following average changes in membrane p.d. (mV): F− +1·7, BrO3− +0·1, Br− ‐4·5, ClO3− ‐5·2, I− ‐7·9, NO3− ‐12·1, ClO4− ‐17·8, SCN− ‐25·3.3. The amplitude of the depolarization caused by increase in K concentration (K‐depolarization) in the peritubular perfusate was found to increase during perfusion of the tissue with ClO4− (by 78%), SCN− (45%), I− (23%), NO3− (20%), Br− (16%); it decreased with F− (by 17%).4. Comparison of membrane p.d. at peak K‐depolarization in the control state (during KCl perfusion) with that obtained in the experimental state (during KA perfusion) was found to be more reliable than determination of bi‐ionic potentials as a qualitative estimate of the permeabilities of the various anions (PA) relative to that of chloride (PCl).5. Study of both peak K‐depolarization p.d. and bi‐ionic potentials yielded the following sequence for halide anion permeabilities: PF > PCl > PBr > PI. The peritubular membrane was found to be substantially more permeable to NO3−, ClO4− and SCN− than to Cl−.6. The sequence of membrane conductances during anionic substitutions was Cl− ≃ BrO3− < Br− ≤ ClO3− < I− ≃ F− < NO3− < ClO4− < SCN−.7. From the changes in p.d. induced by K‐depolarization, the absolute values of p.d. at peak K‐depolarization and from the changes in membrane conductance induced by anionic substitutions, it may be inferred that Br−, I−, NO3−, ClO4− and SCN− all increase PK; and that F− increases PNa (though a smaller increase in PK cannot be excluded).
Effects of sodium, potassium and calcium ions on the slow wave in the circular muscle of the guinea‐pig stomach
Authors: Ohba M. , Sakamoto Y. , Tomita T. 
Published: December 2014

1. The contribution of Na, K and Ca ions to the generation of slow waves in the circular muscle of the guinea‐pig stomach was studied.2. The slow waves had a lower, potential‐independent (first) and an upper, potential‐dependent (second) component. Reduction of the external Na prolonged the first component, but complete removal of Na depolarized the membrane and caused deterioration of the slow wave.3. Readmission of Na (5‐10 m
M) restored the slow wave; this action was not abolished by ouabain.4. Removal of K depolarized the membrane and slightly reduced the amplitude and duration of the slow waves. Readmission of K hyperpolarized the membrane and increased the amplitude and duration of the slow waves, particularly of the first component. Ouabain blocked the effects on the membrane potential, but not the effects on the slow waves.5. An increase in extracellular Ca prolonged the first component and reduced the frequency. Removal of extracellular Ca abolished the slow wave activity. Excess Ca enhanced, and low Ca reduced the effects of altering the concentrations of external K.6. It is concluded that the ouabain‐sensitive Na‐K pump may not be directly involved in generating slow waves, but that some other metabolic process is involved, which is regulated to a large extent by Ca, and possibly also by Na and K.
Membrane properties of Aplysia neurones intracellularly injected with phospholipases A and C
Authors: Hinzen D. H. , Tauc L. 
Published: December 2014

1. The effects of phospholipases A from bee venom and from porcine pancreas and of phospholipases C from Clostridium welchii and Bacillus cereus on active and passive membrane properties of Aplysia neurones have been studied. Consistent alterations in electrical membrane properties were found following intracellular application of three of these enzymes.2. Bee venom phospholipase A produced a rapid decrease of membrane potential and resistance. Voltage clamping revealed a marked depression of peak transient current with little or no effect in the late outward current.3. Mammalian phospholipase A was found ineffective in changing either the resting or active membrane properties.4. Phospholipase C from Bacillus cereus led to a strong hyperpolarization and a fall in membrane resistance. Voltage clamping revealed a marked increase in the late outward current.5. Neurones injected with Clostridium welchii phospholipase C manifested a several‐fold rise in resting membrane resistance as well as a tendency to slight hyperpolarization.6. All enzymes were ineffective when externally applied.7. It is tentatively concluded that the internally applied phospholipases affect specific ionic permeabilities both in the resting and active excitable membrane. Various mechanisms by which the differing actions of enzymes of the same type could be explained are discussed.
Maintained function of foreign and appropriate junctions of reinnervated goldfish extraocular muscle
Authors: Scott Sheryl A. 
Published: December 2014

1. The ability of a multiply innervated muscle to become dually innervated, that is to accept a functional innervation from both its original and a foreign nerve, was investigated using the superior oblique muscle (s.o. muscle) of the goldfish.2. Dual innervation of s.o. muscles was achieved by allowing the original nerve (cranial NIV) to regenerate to its s.o. muscle which had been previously denervated and cross‐innervated by a foreign nerve (cranial NIII), or by allowing the original and the foreign nerve to regenerate simultaneously to a denervated muscle.3. Behavioural observations suggested that in some fish reinnervation of the s.o. muscle by its original nerve repressed the function of a previously established foreign innervation. However, physiological tests which involved the stimulation of both foreign and appropriate nerves, and the recording of mechanical and electrical activity of the s.o. muscle, demonstrated that there was no functional displacement of foreign innervation on these muscles, even on individual dually innervated fibres.4. Dual innervation of the s.o. muscle persisted, apparently unchanged, for as long as the observations were continued (up to 7 months). The s.o. muscle contains two populations of fibres, fast and slow, and both types became and remained dually innervated.5. When both NIII and NIV were allowed to regenerate simultaneously to a denervated s.o. muscle there was no obvious selectivity in the final pattern of innervation. On the average both nerves elicited approximately equal tension from s.o. muscles, and evoked excitatory junctional potentials (e.j.p.s) of similar mean quantal contents.6. ‘Myotypic respecification’ was shown not to be responsible for the discrepancy between the behavioural results which sugested that repression of foreign innervation had occurred, and the physiological results which demonstrated that this was not the case. Anatomical and physiological findings indicated that the discrepancy was attributable to eye rotation produced by regenerated inferior oblique muscle fibres which contracted simultaneously with the cross‐innervated s.o. muscle. The net result was an eye movement in which the activity of the s.o. muscle was masked.7. It is concluded that repression of established foreign neuromuscular connexions following reinnervation by the embryologically correct nerve does not occur on goldfish extraocular muscles. The s.o. muscle can become non‐selectively innervated by both foreign and appropriate axons, and remains so, at least for several months.