bluuebunny/crossref_metadata_2025 huggingface dataset:
Circadian rhythms in human salivary flow rate and composition
Authors: Dawes C.
Published: December 2014

1. Unstimulated whole saliva and parotid saliva stimulated at a constant flow rate of 1·0 ml./min were collected from eight subjects at about 07.00, 11.00, 14.00, 17.00 and 22.00 hr and oral temperature was recorded several times daily for time spans of between 4 and 26 days. A least‐squares cosine wave was fitted to the data to test for the presence and characteristics of circadian rhythms.

2. Estimates of mean level, amplitude, acrophase and period were obtained for different components and the results were subjected to cosinor analysis.

3. Unstimulated whole saliva showed significant circadian rhythms in flow rate and in the concentrations of sodium and chloride but not in protein, potassium, calcium, phosphate or urea.

4. Stimulated parotid saliva showed significant circadian rhythms in the concentrations of protein, sodium, potassium, calcium and chloride but not in phosphate or urea

5. Oral temperature showed a circadian rhythm which, like the salivary rhythms, was of a 24.0 hr periodicity.
The reflex cardiovascular depression caused by occlusion of the coronary sinus in the dog
Authors: Muers M. F. , Sleight P.
Published: December 2014

1. Brief occlusions of the outflow from the cannulated coronary sinus in the open chest anaesthetized dog caused a rise in coronary venous pressure, bradycardia, and systemic hypotension.

2. The bradycardia and hypotension were directly proportional to the peak systolic coronary venous pressures above a threshold value of about 50 mm Hg.

3. The bradycardia, but not the systemic hypotension, was abolished by intravenous atropine. Both responses were abolished by cutting the cervical vagi, and reversibly abolished by cooling them to less than 7° C.

4. During occlusions, there was inhibition of activity in single and small multi‐fibre preparations of sympathetic efferent nerves in the ansae subclaviae and the cervical sympathetic.

5. On the right side, nearly all afferent fibres ran in the recurrent cardiac nerve. There was no concentration of afferents in one cardiac nerve on the left side.

6. It was concluded that the cardiovascular depression was reflex, and was caused by the stimulation of nerves or nerve endings in the ventricles of the heart.
Action potentials from ventricular mechanoreceptors stimulated by occlusion of the coronary sinus in the dog
Authors: Muers M. F. , Sleight P.
Published: December 2014

1. In experiments to determine the type of intra‐cardiac receptors which cause the coronary sinus occlusion reflex, recordings were made from sixty‐nine single and small multi‐fibre preparations of cardiac vagal afferents in open‐chest anaesthetized dogs.

2. Thirty‐two fibres were stimulated by occlusion of the coronary sinus outflow through an indwelling Morawitz cannula. No receptors were stimulated during occlusions at peak systolic coronary venous pressures below the threshold for reflex cardiovascular depression. At higher pressures, fibre recruitment and further increases in stimulated discharge were demonstrated.

3. The afferent endings of twenty‐nine of these fibres were mechanically localized to the epicardium and myocardium of the left ventricle. Three were in the right ventricle. Seventeen single fibres discharged spontaneously at an average of 0·9 impulses/sec. There was cardiac modulation of both resting and stimulated discharge, with most action potentials in systole. Seven of eight fibres conducted at less than 1·0 m/sec.

4. These ventricular receptors and a further twenty‐two otherwise like them but not stimulated by occlusions were designated epi‐myocardial receptors.

5. 73% of receptors were stimulated by intrapericardial nicotine (50–100 μg). Presumptively superficial receptors were more sensitive to this stimulus.

6. Epi‐myocardial receptors were stimulated by intravenous or intracoronary catecholamines, by electrical stimulation of cardiac sympathetic nerves, and by eliciting the carotid sinus occlusion reflex. Aortic occlusion stimulated 66% of fibres tested, but was a less effective stimulus. After all these stimuli, there was a systolic modulation of discharge in more than 70% of fibres.

7. It was concluded that the epi‐myocardial receptors are similar to those previously shown to cause the epicardial chemoreflex, and to participate in the coronary chemoreflex. It is suggested that they are responsive to systolic mechanical changes which are accentuated by catecholamines. Their possible effectiveness in other cardiac reflexes and in initiating circulatory changes at the beginning of exercise and the vasovagal syndrome is discussed.
The mechanism of adenosine diphosphate induced platelet aggregation: binding to platelet receptors and inhibition of binding and aggregation by prostaglandin E1
Authors: Boullin D. J. , Green A. R. , Price K. S.
Published: December 2014

1. Normal human blood platelets in stirred plasma were incubated with [14C]ADP for 10–360 sec and the aggregation responses were correlated with platelet bound radioactivity, the platelets being separated from the plasma within 25 sec of the end of the experiment.

2. The platelet aggregation response, measured as a change in light transmittance through platelet‐rich plasma, was related to the plasma [14C]ADP concentration and linearly related to the log platelet bound [14C]ADP 60–120 sec after addition of nucleotide to plasma.

3. Thin layer chromatography of the platelet bound radioactivity showed that 78–90% was unmetabolized ADP, the remainder being AMP. Plasma radioactivity consisted of ADP, AMP and adenosine. There was no detectable radioactive cyclic AMP in either platelets or plasma.

4. Further accumulation of radioactivity occurred after 180 sec but was not related to the aggregation response.

5. Prostaglandin E1 inhibited aggregation and platelet [14C]ADP accumulation when added to platelet‐rich plasma 60 sec before [14C]ADP. There was a significant correlation between inhibition of aggregation and inhibition of [14C]ADP accumulation.

6. Prostaglandin E1 also reversed ADP aggregation when added to platelet‐rich plasma after the nucleotide, with an accompanying decrease in platelet bound [14C]ADP.

7. It is concluded that ADP induces platelet aggregation by binding to specific receptors probably located on the plasma membrane, and that prostaglandin E1 inhibits this effect by interfering with the ADP binding.
Changes during eating in oxygen consumption, cardiac function and body fluids of sheep
Authors: Christopherson R. J. , Webster A. J. F.
Published: December 2014

1. A study was made of the changes taking place in O2 consumption, cardiac function and the volume and composition of the body fluids of sheep while they consumed a meal of hay.

2. During eating Pa, CO2 and Pv, CO2 both increased, pH decreased and free plasma [HCO3−] increased. Venous haematocrit increased sharply at the beginning of the meal, and declined slowly after feed was removed.

3. Arterial PO2 did not change significantly during eating. However Pv, O2 fell slightly but significantly. The O2 saturation of venous blood fell due to the decline in pH. Estimated CO2 in arterial blood increased as a consequence of increased haemoglobin content. The net effect was to increase arteriovenous difference in O2 content from 4·4 ml./100 ml. before eating to 6·0 ml./100 ml. at the end of the meal.

4. O2 consumption increased about 60% during eating and fell rapidly thereafter. Heart rate followed a similar pattern. Cardiac output however increased only about 17%, from 6 to 7 l./min. Consequently stroke volume declined throughout the meal from 76 to 52 ml./beat.

5. Plasma volume, estimated from measurements of T‐1824, declined sharply by about 300 ml. at the beginning of the meal and recovered slowly after feed was removed. Blood volume declined less because of a rise in circulating erythrocytes.

6. Extracellular fluid volume was estimated from measurements of thiocyanate and thiosulphate spaces. Thiocyanate space measurements were abandoned after thiocyanate was found to be concentrated in saliva. Considerable random variation occurred in measurements of changes in extracellular fluid from thiosulphate disappearance but the results did reveal a significant fall of 1000–1500 ml. in extracellular fluid volume during eating.

7. The significance of these interrelated changes is discussed in relation to the maintenance of homoeostasis during eating in the sheep.
Coronary vasodilator responses to hypoxia before and after aminophylline
Authors: Afonso S. , Ansfield T. J. , Berndt T. B. , Rowe G. G.
Published: December 2014

1. In previous studies adenosine has been postulated to be the mediator in coronary blood flow regulation and aminophylline was found to inhibit the coronary vasodilator action of adenosine. The present study was performed to determine whether aminophylline inhibits coronary vasodilatation induced by hypoxia.

2. Coronary and systemic haemodynamic and metabolic effects of hypoxia were studied in anaesthetized dogs before and after aminophylline. Aminophylline did not influence coronary vasodilatation induced by hypoxia.

3. These results are held not to lend support to the hypothesis that adenosine is the metabolite responsible for the regulation of coronary blood flow.
Transcapillary fluid movement in human calf after drinking hypertonic saline
Authors: Matsubara I.
Published: December 2014

1. Transcapillary absorption of interstitial fluid was demonstrated with a pressure plethysmograph applied to the human calf after the ingestion of 200 ml. hypertonic (5·1%) saline. Capillary absorption began within 15 min after ingestion and lasted for about 2 hr. The maximum rate of absorption (0·019 ml./min. 100 ml. tissue) was attained 30–75 min after ingestion.

2. The total amount of fluid absorbed into capillary blood vessels in the calf was 1·11 ml./100 ml. tissue. The amount of fluid thus absorbed in the whole body was estimated to be 677 ml.

3. The capillary filtration coefficient (CFC) of the calf was also measured by the pressure plethysmograph. This was 0·0038 ml./min. mm Hg. 100 ml. tissue.

4. The peak value of capillary absorption pressure was 5·2 mm Hg.

5. The total osmotic pressure of the plasma rose by 12·6 m‐osmole/kg H2O after ingestion. This rise was accompanied by transcapillary fluid absorption.

6. The plasma protein concentration and packed cell volume were almost unchanged by ingestion, indicating that the plasma volume was unaltered.

7. It was estimated that the net shift of fluid between intracellular and interstitial compartments during the period of transcapillary fluid absorption was very small.

8. It is concluded that the volume of fluid moving from plasma into intestinal lumen is the same as that flowing from interstitial fluid into plasma, and that the transcapillary absorption is caused by a difference in osmotic pressure between the plasma and the interstitial fluid.
Electrical properties of white and red muscle fibres of the elasmobranch fish Scyliorhinus canicula
Authors: Stanfield P. R.
Published: December 2014

1. Standard electrophysiological techniques (including a method which controls the membrane potential at a point on a muscle fibre) were used to investigate the electrical properties of white and red muscle fibres of the elasmobranch fish Scyliorhinus canicula.

2. The resting potential of the white fibres in the standard Ringer solution was — 85·2 ± 0·4 mV. That of the red fibres was — 71·1 ± 1·2 mV. The membrane resistance of white fibres was 1588 ± 97 Ω cm2 and that of red fibres was 5410 ± 1070 Ω cm2.

3. White fibres always responded to direct stimulation with an action potential. It proved impossible, with two impaling micro‐electrodes, to record action potentials from the red fibres, although on one occasion an abortive spike was seen.

4. The resting membrane of the red fibres seemed less permeable to chloride than was the membrane of the white fibres. However, the resting potassium permeability showed the potential dependence called inward or anomalous rectification in both white and red fibres.

5. White fibres responded to square depolarizing pulses with conductance changes to sodium and, subsequently, to potassium.

6. All red fibres examined with the point voltage clamp showed a delayed increase in potassium conductance on depolarizing.

7. Out of twenty‐seven red fibres examined, six showed no sign of having any sodium conductance mechanism. Eight showed large sodium currents on depolarizing, and the remaining thirteen had small sodium currents. It seemed likely that the group of eight fibres might be able to propagate action potentials.
Effects of intracerebral micro‐injection of sodium salicylate on temperature regulation in the rabbit
Authors: Cranston W. I. , Rawlins M. D.
Published: December 2014

1. Symmetrical, bilateral micro‐injections (10 μl.) of 6–30 μg sodium salicylate have been made into various parts of the brains of febrile and afebrile rabbits.

2. In rabbits with fever induced by an intravenous infusion of endogenous pyrogen, micro‐injections of sodium salicylate produced antipyresis when given into the preoptic hypothalamus and the mid‐brain.

3. In afebrile rabbits, micro‐injections of sodium salicylate into these areas were without effect on temperature.

4. The results suggest that at least part of the antipyretic effect of salicylates may be mediated by antagonizing the effects of endogenous pyrogen within these areas of the brain.
The effect of efferent discharges in renal nerves on the activity of arterial mechanoreceptors in the kidney in rabbit
Authors: Niijima Akira
Published: December 2014

1. The effect of sympathetic efferent flow in renal nerves on afferent discharges from renal arterial mechanoreceptors was observed in dissected filaments of renal nerves in the rabbit.

2. An increase in afferent discharge rate was observed after renal nerve stimulation.

3. Perfusate accumulated during renal nerve stimulation in an isolated kidney preparation showed a vasoconstrictor effect on blood vessels in rabbit ear.

4. Infusion of a small amount of (±)‐noradrenaline increased afferent discharge rate.

5. Modification of blood pressure levels by chemical means modified renal afferent discharge rate.

6. It is suggested that there is an efferent control mechanism on the activity of renal arterial mechanoreceptors by a vasomotor reflex.
Effects of stimulation of efferent fibres of the vagus on the reticulo‐omasal orifice of the sheep
Authors: Newhook J. C. , Titchen D. A.
Published: December 2014

1. The reticulo‐omasal orifice has been observed and its activity recorded in decerebrate and spinal preparations of lambs and in lambs and sheep anaesthetized with chloralose.

2. Spontaneous closure movements at about 6/min were seen, or recorded from balloons placed in the orifice in all types of preparation when both vagus nerves had been cut and after atropine, hexamethonium, phentolamine and propranolol had been given
I.V.

3. The effects on the reticulo‐omasal orifice of stimulation in the neck of efferent fibres of the vagus nerves on either side differed according to the form of the stimulus applied.

4. Threshold stimulation of the vagus nerve caused closing of the orifice which was blocked by atropine.

5. Opening of the orifice and disappearance of spontaneous closing movements followed more intense stimulation of the vagus nerves.

6. Vagal opening effects were obtained after atropine was given and after adrenergic opening and closure effects had been blocked with phentolamine and propranolol.
Kinetics of slow thermal reactions during the bleaching of rhodopsin in the perfused frog retina
Authors: Baumann C.
Published: December 2014

1. Slow thermal reactions occurring in the rhodopsin rods of flash‐irradiated frog retinas were investigated spectrophotometrically.

2. Five substances were identified as reactants: metarhodopsin II, metarhodopsin III, all‐trans‐retinal, opsin, and all‐trans‐retinol.

3. Quantitative analysis showed that the transition between these substances are not a series of three consecutive reactions.

4. An alternative scheme, compatible with the results, consisted of four reactions and involved two parallel pathways for the decay of metarhodopsin II, viz. conversion into metarhodopsin III, and hydrolysis into retinal and opsin.

5. The first‐order rate constants for the four reactions were as follows: 1·4 × 10−2 sec−1 for the conversion of metarhodopsin II into metarhodopsin III; 7·9 × 10−3 sec−1 for the hydrolysis of metarhodopsin II; 1·4 × 10−3 sec−1 for the hydrolysis of metarhodopsin III; and 2·6 × 10−3 sec−1 for the reduction of retinal into retinol (21° C).

6. Two other four‐parameter schemes involving an equilibrium between metarhodopsin II and metarhodopsin III were also considered. One was found to be incompatible with the results. The other, though adequate, did not describe the data as well as the model summarized in 4 and 5. It also had the peculiar property of requiring that two apparently independent parameters be equated.
Counting every quantum
Authors: Sakitt B.
Published: December 2014

1. Human subjects were asked to rate both blanks and very dim flashes of light under conditions of complete dark adaptation at 7° in the periphery. The ratings used were 0, 1, 2, 3, 4, 5, and 6.

2. For one subject (B.S.) the distributions of ratings were approximately Poisson distributions. The data were consistent with each rating being the actual number of effective quantal absorptions plus the number of noise events. This subject was presumably able to count every rod signal (effective absorptions plus noise).

3. For two other subjects, the data were consistent with the ratings being one less (L.F.) and two less (K.D.) than the number of effective absorptions plus noise. They were able to count every rod signal beginning with 2 and 3 respectively. A fourth subject's erratic data could not be fitted.

4. The fraction of quanta incident at the cornea that resulted in a rod signal was estimated to be about 0·03 which is consistent with physical estimates of effective absorption for that retinal region.

5. A simulated forced choice experiment leads to an absolute threshold about 0·40 log units below the normal yes‐no absolute threshold. This and other results indicate that subjects can use the sensory information they receive even when only 1, 2 or 3 quanta are effectively absorbed, depending on the individual. Humans may be able to count every action potential or every discrete burst of action potentials in some critical neurone.
Ionic permeability changes as the basis of the thermal dependence of the resting potential in barnacle muscle fibres
Authors: Fischbarg Jorge
Published: December 2014

1. The thermal dependence of the resting potential of isolated barnacle muscle fibres was larger (1–2 mV/° C) than predicted by Nernst's equation (about 0·2 mV/° C). A comparative study was made of the influence on thermal dependence of parameters related to (a) passive permeability and to (b) Na extrusion.

2. High [K]o decreased the thermal dependence reversibly. [Ki], [Na]i and [Cl]i were determined by chemical analysis, and Goldman's equation was fitted to data relating V to [K]o at different temperatures, in the presence and absence of ouabain 5 × 10−5
M. In both cases the behaviour of V when T was lowered from 20 to 4° C was accounted for by increases in the calculated PNa/PK and PCl/PK (from 0·006 to 0·043 and from 0·17 to 0·34 on the average, respectively.)

3. Other parameters related to passive permeability (and which caused reversible depolarization): decreased [Cl]o (methanesulphonate or gluconate substituted), and decreased pHo (below 5·0), also decreased the thermal dependence reversibly.

4. Inhibitors (ouabain 5 × 10−5
M, cyanide 2–10 × 10−3
M, 2,4‐dinitrophenol 2 × 10−4
M) externally applied did not affect either resting potential or its thermal dependence for several hours.

5. Increasing [Na]i three‐ to fourfold by intracellular injection decreased both resting potential and its thermal dependence.

6. Although a small effect by a Na electrogenic pump cannot be excluded, the largest part of the thermal effect on the resting potential is concluded to depend on temperature‐induced variations in relative ionic permeabilities to cations and anions. A model is proposed which can account for the data assuming that (a) each permeant ion associates to a separate site in the membrane, and (b) the ion‐site equilibrium is temperature‐dependent.
Reflex cardiovascular and respiratory responses originating in exercising muscle
Authors: McCloskey D. I. , Mitchell J. H.
Published: December 2014

1. In anaesthetized and decerebrate cats isometric exercise of the hind limb muscles was elicited by stimulating the spinal ventral roots L7‐S1. This caused a rise in arterial blood pressure, with small increases in heart rate and pulmonary ventilation. These changes were abolished by cutting the dorsal roots receiving afferents from the exercising muscle.

2. When the triceps surae muscle was made to exercise by ventral root stimulation, occlusion of the femoral artery and vein through and beyond the period of exercise caused the blood pressure to remain raised until the occlusion was removed. The ventilatory and heart rate responses were not markedly altered or prolonged by such circulatory occlusion.

3. Injection of small volumes of 5% NaCl or isotonic KCl into the arterial blood supplying hind limb muscles gave cardiovascular and respiratory responses similar to those evoked by exercise. Like the responses to exercise, these responses were abolished by dorsal root section.

4. Direct current anodal block of the dorsal roots receiving afferents from the exercising muscle was used to block preferentially large myelinated fibres: this form of block did not abolish the evoked cardiovascular and respiratory responses. Local anaesthetic block of the dorsal roots was used to block preferentially unmyelinated and small myelinated fibres: this form of block abolished the cardiovascular and respiratory responses. It is concluded that the reflex responses are mediated by fibres within groups III and IV (small myelinated fibres and unmyelinated fibres).
The formation of a renally active peptide by cat lungs from γ‐globulin in vitro and the plasma concentrations of this peptide, in vivo
Authors: Lockett Mary F.
Published: December 2014

1. A substance (LS), extracted in aqueous acetone and separated by partition and thin‐layer chromatography, has been obtained from lung perfusates and from the systemic blood of cats.

2. LS is assayed biologically in rats during sustained saline diuresis by measurement of the μequiv Na retained. This parameter is linearly related to the log concentration of LS infused.

3. Lungs perfused with Tyrode fluid neither contain nor produce LS. Production of LS begins when γ‐globulins (in cat plasma, mixed ox globulins or equine Cohn II) are present in the perfusing fluid.

4. The proteinase inhibitor trasylol does not prevent the formation of LS by lung; trasylol protects LS from break‐down during re‐perfusion and during isolation from perfusates or from blood.

5. In cats under chloralose anaesthesia LS is present during haemorrhage in systemic arterial and mixed venous blood, the arterial concentration of LS is approximately four times the venous.
Extracellular cations and the movement of choline across the erythrocyte membrane
Authors: Martin K.
Published: December 2014

1. The ability of human erythrocytes to accumulate choline is abolished when external Na is replaced by Cs, Rb, K or Li but is increased when the external cation is Mg or Ca.

2. The unidirectional influx of choline is reduced when external Na is replaced by other monovalent cations but is not changed when Na is replaced by Mg or Ca.

3. The unidirectional efflux of choline into a choline‐free medium is increased when external Na is replaced by other monovalent cations and markedly reduced when Na is replaced by Mg or Ca. When the external medium contains 1 m
M choline, changing the external cation has virtually no effect on the rate of choline efflux.

4. When the extracellular concentrations of K and Na are similar to that found in the intracellular water, choline appears to become passively distributed across the cell membrane; when the extracellular K is then replaced by Cs a net efflux of choline against a concentration gradient results.

5. It is concluded that the choline carrier may be described as a cation carrier with a high affinity for choline and affinities for Cs > Rb > K > Li > Na and that these monovalent cations can cross the membrane on the choline transport system.
Facilitation of monosynaptic excitatory synaptic potentials in spinal motoneurones evoked by internuncial impulses
Authors: Kuno M. , Weakly J. N.
Published: December 2014

1. Descending tracts and primary afferent fibres were chronically degenerated in the lumbosacral cord of the cat, and attempts were made to evoke monosynaptic e.p.s.p.s in motoneurones by stimulation of interneurones with a pair of fine electrodes inserted into the cord.

2. The reversal potential of monosynaptic e.p.s.p.s so produced was more negative than that measured for monosynaptic e.p.s.p.s produced by afferent impulses.

3. Monosynaptic e.p.s.p.s evoked in motoneurones by internuncial impulses showed a significantly greater facilitation than those produced by afferent impulses.

4. Monosynaptic e.p.s.p.s in a motoneurone produced by supramaximal intraspinal stimuli often revealed a fluctuation in amplitude. In such cases, when two successive stimuli were applied at a short interval, the mean amplitude of the second e.p.s.p.s was greater than that of the first e.p.s.p.s. This facilitation was associated with a decrease in the coefficient of variation of the e.p.s.p. amplitude fluctuation.

5. The degree of facilitation of monosynaptic e.p.s.p.s evoked by internuncial impulses was not related to the amount of transmitter released by the preceding impulses.

6. It is concluded that facilitation of monosynaptic e.p.s.p.s evoked by both afferent and internuncial impulses is based on the same mechanism and that the degree of facilitation of e.p.s.p.s is entirely determined by the nature of presynaptic elements.
An attempt at an analysis of the factors determining the time course of the end‐plate current
Authors: Kordaš M.
Published: December 2014

1. An attempt was made to analyse further the factors which might determine the time course of the falling phase of the end‐plate current.

2. The end‐plate current was measured by ‘clamping’ the membrane potential during neuromuscular transmission. The falling phase of the end‐plate current had an exponential and a non‐exponential portion.

3. The exponential portion of the falling phase of the end‐plate current was found to be strongly affected by changes in the membrane potential and by relatively small changes in temperature.

4. It is suggested that the two rate constants which determine the dissociation of the receptor‐mediator complex are affected by both temperature and the membrane potential. Under certain experimental conditions these two rate constants alone seem to determine the time course of the exponential portion of the falling phase of the end‐plate current.
The effect of tetanus toxin at the neuromuscular junction in the goldfish
Authors: Mellanby Jane , Thompson P. A.
Published: December 2014

1. The effect of tetanus toxin on neuromuscular transmission in the abductor superficialis muscle of the goldfish fin has been investigated.

2. The abductor superficialis muscle is multiply innervated and junction potentials (j.p.s) and miniature junction potentials (min.j.p.s) can be recorded with an intracellular micro‐electrode at any point of impalement. Intracellular recordings have been made from muscles in which neuromuscular transmission has been blocked, either completely, or partially, by
I.M. injection of tetanus toxin. In addition, the tension response of both acutely and chronically toxin‐blocked muscles to carbachol (1 × 10−4
M) has been investigated.

3. As the neuromuscular block proceeds, the frequency of min.j.p.s falls, and some time after the muscle has stopped responding to nerve stimulation the min.j.p.s disappear.

4. In muscles in which the block has not yet proceeded to completion, it has been found that the reduction in the frequency of the min.j.p.s is unaccompanied by any change in their range of amplitudes.

5. The min.j.p. frequency can be greatly increased in such incompletely blocked preparations by repetitive stimulation of the nerve (at, for example, 100/sec for 10 sec). The min.j.p.s obtained are indistinguishable from those seen in the absence of stimulation. Additionally, min.j.p.s can be evoked by similar repetitive stimulation in muscles which are completely blocked, and in which no min.j.p.s are seen without stimulation, so long as the block has only been complete for a short time.

6. The tension response to carbachol of muscles which have been paralysed by tetanus toxin for only a few days is identical with that of normal muscles. In contrast, chronically toxin‐paralysed muscles contract more rapidly, usually more vigorously, and relax more rapidly than normal muscles.

7. It is concluded that tetanus toxin prevents both the nerve‐stimulated and spontaneous release of acetycholine from the presynaptic terminals in the abductor superficialis muscle of the goldfish fin.
Inhibitory and excitatory effects of dopamine on Aplysia neurones
Authors: Ascher P.
Published: December 2014

1. Electrophoretic application of dopamine (DA) on Aplysia neurones elicits both excitatory and inhibitory effects, which in many cases are observed in the same neurone, and often result in a biphasic response.

2. The DA receptors are localized predominantly on the axons. Desensitization, which occurs after repeated injections or with bath application of DA, is more marked for excitatory responses.

3. Tubocurarine and strychnine block the DA excitatory responses without affecting the inhibitory ones, which can be selectively blocked by ergot derivatives. It is concluded that the excitatory and inhibitory effects are mediated by two distinct receptors.

4. The two DA receptors can be pharmacologically separated from the three ACh receptors described in the same nervous system.

5. In some neurones the dopamine inhibitory responses can be inverted by artificial hyperpolarization of the membrane at the potassium equilibrium potential, EK, indicating that dopamine causes a selective increase in potassium permeability.

6. In other neurones the reversal potential of dopamine inhibitory responses is at a more depolarized level than EK, but can be brought to EK by pharmacological agents known to block the receptors mediating the excitatory effects of DA.

7. In still other neurones, the hyperpolarization induced by DA cannot be inverted in normal conditions, but a reversal can be induced by ouabain or by the substitution of external sodium by lithium. These results are discussed in terms of an hypothesis in which dopamine increases the potassium permeability of a limited region of the axonal membrane.

8. It is concluded that a selective increase in potassium permeability probably accounts for all dopamine inhibitory effects in the neurones studied.
Stimulation, by inhibition of (Na+‐K+‐Mg2+)‐activated, ATP‐ase, of acetylcholine release in cortical slices from rat brain
Authors: Vizi E. S.
Published: December 2014

1. A study has made of the effect of (Na+‐K+‐Mg2+)‐activated membrane ATP‐ase inhibitors on the acetylcholine release from the terminals of enteric nerves and from cortical slices.

2. The resting output of acetylcholine from slices of rat cortex was not affected by tetrodotoxin or by noradrenaline, indicating the lack of propagated activity during rest. Furthermore, there was an output of acetylcholine in the absence of Ca.

3. The resting acetylcholine output from cortical slices was increased by (a) addition of ouabain or (b) administration of sodium p‐hydroxymercuribenzoate (PHMB), (c) sodium withdrawal and (d) Ca replacement by Ba+.

4. Omission of Ca in the presence of 1 m
M ethyleneglycol‐bis‐(β‐aminoethyl‐ether)‐N,N′‐tetra‐acetic acid (EGTA) did not affect the increase of acetylcholine release by the inhibition of (Na+‐K+‐Mg2+)‐activated ATP‐ase induced by ouabain or by PHMB, but reduced that due to Na removal.

5. Ouabain increased acetylcholine release promptly.

6. Mg‐excess (9·3 m
M), noradrenaline and adrenaline were capable of reducing the increase of acetylcholine release from cortical slices evoked by ouabain, PHMB or by Ca replacement by Ba, but not by Na removal.

7. A possible role for (Na+‐K+‐Mg2+)‐activated ATP‐ase in the release of acetylcholine is discussed. It is suggested that the effect of Ca and Mg ions on acetylcholine release might be attributed to their ability to inhibit and activate the membrane ATP‐ase, respectively.
Morphology of interneurones mediating Ia reciprocal inhibition of motoneurones in the spinal cord of the cat
Authors: Jankowska Elżbieta , Lindström S.
Published: December 2014

1. Interneurones identified by physiological criteria (Hultborn, Jankowska & Lindström, 1971b) to mediate Ia reciprocal inhibition of motoneurones in the spinal cord of the cat were stained by intracellular injection of a fluorescent dye (Procion Yellow).

2. The somas of the stained cells were found in Rexed's lamina VII, just dorsal or dorsomedial to the motor nuclei. Their size was about 30 × 20 μm. The cells had four to five slender, weakly branching dendrites. The total extension of their dendritic trees was about 600 μm dorsoventrally, 400 μm mediolaterally and 300 μm rostrocaudally.

3. The axons originated from a separate axon hillock or from the base of a dendrite. They were myelinated with external diameter of about 6–14 μm and projected to either the ipsilateral ventral or lateral funiculi. Early collaterals were found only exceptionally. Some axons bifurcated into an ascending and a descending branch within the funiculi.

4. The possibility of identifying the Ia inhibitory interneurones on purely morphological grounds is discussed.
The effect of chronic duct ligation on the vascular and secretory responses of the cat's submaxillary gland
Authors: Darke A. C. , Smaje L. H.
Published: December 2014

1. The object of the present experiments was to re‐investigate the role of kallikrein in functional hyperaemia in the submaxillary gland of the cat. Kallikrein concentration in the gland and saliva was reduced by ligation of the duct for 2–3 days before the acute experiment, at which time the duct was cannulated proximal to the ligation and blood flow and salivation measured.

2. Despite the fall in kallikrein concentration, a normal two‐phase vascular response was obtained on continuous stimulation of the chorda‐lingual nerve at 1–5 Hz and the progressive increase in blood flow to a constant level characteristic of 10 and 20 Hz stimulation was also seen. Quantitatively, the increase in blood flow following a 10 sec stimulation was reduced to about 75% of control values at all stimulation frequencies used and the maintained vasodilatation was reduced when using continuous stimulation at 1 Hz but not at 10 and 20 Hz.

3. The supersensitivity to the vasodilator properties of bradykinin, previously reported to follow duct ligation, was confirmed.

4. The increased blood flow produced by chorda‐lingual nerve stimulation could be delayed by circulatory arrest. Evidence was obtained suggesting that the vascular response to chorda stimulation delayed by arterial occlusion was not mediated by kallikrein alone.

5. It was concluded that kallikrein was not the sole mediator of functional hyperaemia in the cat submaxillary gland but that a combination of vasodilator nerves and kallikrein release explained more phenomena than either hypothesis alone.
Increased thyroxine secretion following administration of dinitrophenol to rats
Authors: England P. , Harland W. A. , Orr J. S. , Randall T. W.
Published: December 2014

1. Feeding male rats 0·2% dinitrophenol (DNP) in the diet caused weight loss, a significant fall in the plasma protein bound iodine concentration, and a rise in the thyroxine secretion rate. Thyroxine concentration was raised in the liver and intestinal tract with contents, reduced in the carcass, and unchanged in the pelt.

2. Radio‐iodine uptake by the thyroid gland was unchanged but there was a significant fall in the thyroid/serum activity ratio.

3. Five hours after tracer radiothyroxine, DNP treated rats had a reduced fraction of dose in the plasma, with raised concentrations in the liver and intestines.

4. Fractional turnover rates of radiothyroxine in plasma, liver and carcass were raised in DNP treated animals.

5. DNP caused a significant increase in the biliary clearance of radiothyroxine, when measured immediately after administration of tracer and 4 hr later.

6. It is postulated that DNP displaces thyroxine from its plasma binding proteins and that the displaced hormone is excreted in the bile. This wastage together with increased demand resulting from DNP induced hypermetabolism results in increased output of thyroxine by the thyroid gland.
The interaction of reflexes elicited by stimulation of carotid body chemoreceptors and receptors in the nasal mucosa affecting respiration and pulse interval in the dog
Authors: Angell‐James Jennifer E. , Daly M. de Burgh
Published: December 2014

1. The effects on respiration and pulse interval of stimulation of the carotid body chemoreceptors before, during and after stimulation of receptors in the nose have been studied in the anaesthetized dog.

2. Stimulation of a carotid body by infusion of cyanide into the ipsi‐lateral common carotid artery causes hyperpnoea and either an increase, decrease or no change in pulse interval.

3. Excitation of receptors in the nasal mucosa leads to reflex apnoea or a reduction in breathing, and an increase in pulse interval.

4. When the carotid bodies are excited by the same dose of cyanide during stimulation of the nasal mucosa, the chemoreceptor‐respiratory response is abolished or reduced in size compared with the control effect. On the other hand, the chemoreceptor‐cardio‐inhibitory response is considerably enhanced.

5. The potentiated cardio‐inhibitory response of combined chemoreceptor and nasal stimulation could not be accounted for by the change in pulmonary ventilation, arterial PO2 or PCO2, or mean arterial blood pressure.

6. These results indicate that excitation of the nasal reflex inhibits the chemoreceptor‐respiratory reflex response but facilitates the chemoreceptor‐cardio‐inhibitory reflex response. The possible sites of these interactions between the nasal and chemoreceptor reflexes are discussed.
Determination of the frequency response of isometric soleus muscle in the cat using random nerve stimulation
Authors: Mannard Allan , Stein Richard B.
Published: December 2014

1. The frequency response of isometric soleus muscle was determined efficiently by analysis of the unfused tension generated during short periods of random stimulation of the divided ventral roots, in anaesthetized cats.

2. Despite the complexities of skeletal muscle, the frequency response of soleus, at moderate lengths and stimulation rates in the physiological range, is closely approximated by the frequency response function for a simple, linear, second‐order system near critical damping.

3. The soleus muscle shows a uniformly high sensitivity to fluctuations in nerve activity over a range of frequencies similar to the range of frequencies of muscular activity observable during behaviour. The nerve‐muscle preparation appears to be well suited for smooth and steady motor activity, since it is much less responsive to the higher frequency components contained in individual action potentials or generated in tremor.

4. The second‐order parameters: low‐frequency gain, natural frequency and damping ratio provide useful descriptions of the changes in the muscle's response caused by variations of muscle length, nerve stimulation rate or number of active motor units.

5. A reduction in tension incurred, for example, during fatigue can be compensated to some extent either by a lengthening of the loaded muscle or through an increase in neural spike repetition rate. However, both mechanisms produce concomitant increases in the ‘sluggishness’ (increased damping and lower natural frequency) of the preparation. This sluggishness may arise out of limitations imposed by the mechanism for the re‐uptake of calcium into the sarcotubular system.

6. One naturally occurring method of increasing tension, by recruitment of more active motoneurones, seems to be desirable because tension can be augmented in this way without an increase in sluggishness. This is presumably because recruitment increases the muscle's response without affecting excitation‐contraction coupling in fibres already active.
The effect of increasing the innervation field sizes of nerves on their reflex response time in salamanders
Authors: Stirling R. Victoria
Published: December 2014

1. A simple quantitative measure was sought which could describe the relationship between reflex coupling in the spinal cord of salamanders and the peripheral innervation fields of the nerves from which the reflexes were elicited.

2. In decerebrate salamanders reflex responses were recorded between pairs of cut hind limb nerves. The latencies (S/R times) of these reflex responses were bilaterally symmetrical for a given pair of nerves and were shorter when the stimulated nerve of the pair had a large motor and sensory peripheral limb innervation field; this was especially obvious for reflexes between 15th and 17th segmental nerves.

3. After cutting or crushing the 16th nerve in adult salamanders, the adjacent 15th and 17th nerves sprouted collaterally to innervate denervated skin and muscle. There was apparently complete recovery of normal tactile reflexes and walking movements within a month.

4. The operation did not affect the reflex response (S/R) times for nerve combinations on the unoperated side, which were not significantly different from those of normal animals with similar sized peripheral nerve fields. The unoperated side therefore represented the preoperative condition.

5. In animals where one or both the 15th and 17th nerves had increased its innervation field size, the S/R times between them were significantly shorter on the operated side when the nerve with the enlarged field was stimulated. The degree of shortening was greatest for nerves showing the largest increase in peripheral field area.

6. The S/R times between the 15th and 17th nerves were similar to those measured in normal animals in which the peripheral fields were of similar size to the enlarged fields in the operated animals. In a few cases where the increase in field size was considerable, the S/R time between the 15th and 17th nerves became as short as that between the 15th and 16th nerves on the control side.

7. After removal of the 15th nerve, the 14th nerve sprouted into the trunk skin and muscle previously innervated by the 15th nerve and the 16th nerve into denervated limb skin and muscle. In spite of the increased peripheral fields of both these nerves, there was no change in the S/R times between them, or between any other pair of limb nerves on the operated side.

8. The decrease in the S/R times between the 15th and 17th nerves was only observed where the stimulated nerve had increased its peripheral limb innervation field. The possible causes and significance of this shortening reflex response times are discussed in the context of an apparently functionally appropriate adaptation in the spinal cord.
Morphological identification and intrafusal distribution of the endings of static fusimotor axons in the cat
Authors: Barker D. , Emonet‐Dénand Françoise , Laporte Y. , Proske U. , Stacey M. J.
Published: December 2014

1. Tenuissimus muscles of the cat were prepared in which the motor innervation was reduced to a single γ axon by cutting all the other motor axons and allowing them to degenerate during a period of 7–12 days. The function of the surviving γ axon was then determined, and the distribution of its endings ascertained in teased, silver preparations.

2. In the ten muscles successfully prepared the function of the surviving γ axon was static and the motor innervation distributed to the spindles consisted of trail endings. The conduction velocities of the axons ranged from 33 to 48 m/sec.

3. A detailed histological analysis was made of thirty spindles innervated by six of the surviving static axons.

4. The six static axons distributed trail endings to both bag and chain muscle fibres in the poles of thirty spindles with about twice the frequency of supplying them to poles in which the distribution was restricted exclusively to one type of muscle fibre or the other.

5. The density of trail innervation supplied to the bag fibres, in terms of the mean number of terminals per fibre, was typically from one and a half to twice that supplied to the chain fibres. On the other hand, whereas the number of bag fibres supplied with trail endings in a spindle pole was seldom more than one, the number of chain fibres innervated was usually two in a range of one to four.

6. The possible effects that partial denervation might have had on the spindles are discussed, but it is concluded that they are unlikely to have affected the results.
Studies of the pulmonary vagal control of central respiratory rhythm in the absence of breathing movements
Authors: Bartoli A. , Bystrzycka Ewa , Guz A. , Jain S. K. , Noble M. I. M. , Trenchard Diana
Published: December 2014

1. Breuer's hypothesis that the vagus nerves exert a tonic control of respiratory rhythm, in addition to the phasic control, was examined.

2. Closed‐chest cardiopulmonary bypass was instituted in dogs weighing 20–30 kg anaesthetized with chloralose. Respiratory rhythm was recorded from a phrenic electroneurogram.

3. Complete muscular paralysis induced with gallamine triethiodide produced an increase in the duration of inspiration and an increase in the amplitude of the integrated phrenic electroneurogram. There was no consistent effect on expiratory duration. Gallamine produced no effect when given after vagotomy.

4. In the paralysed state, an increase in lung volume of 25–100 ml. for 30–60 sec produced a sustained increase in the duration of expiration and a decrease of respiratory rate: there was little effect on inspiratory duration, or the amplitude of the integrated phrenic electroneurogram.

5. A decrease in lung volume of the same order of magnitude for the same period produced a sustained decrease in the duration of expiration and an increase of respiratory rate: there was little effect on inspiratory duration or the amplitude of the integrated phrenic electroneurogram.

6. The phenomena described in (5) and (6) constitute a high gain respiratory frequency controller. They did not occur after bilateral cervical vagotomy.

7. Bilateral cervical vagotomy during complete muscular paralysis produced a further increase in the duration of inspiration and in the amplitude of the integrated phrenic electroneurogram; there was no consistent effect on expiratory duration.

8. The results confirmed Breuer's hypothesis and showed that inspiratory duration and expiratory duration are controlled independently.