bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors controlling the secretion of a substance biologically resembling the 18‐monoacetate of D‐aldosterone by heart muscle
Authors: Lockett Mary F. , Retallack R. W.
Published: December 2014

1. Previous work has demonstrated that the cat heart secretes a substance which resembles the 18‐monoacetate of
D‐aldosterone (18 MA) in chromatographic properties and biological actions. This substance (HS) releases ADH from the neurohypophysis and, in higher concentration, causes renal retention of salt and water. HS is extracted from blood, separated chromatographically and assayed in terms of equivalent 18 MA activity either by inhibition of water diuresis in rats or by reduction of the excretion of Na by the isolated kidney. Positive correlation has been demonstrated between heart rate and HS secretion.

2. Heart—lung preparations from cats have been used to disclose additional factors controlling the rate of secretion of HS from heart muscle.

3. Positive inotropic effects produced by administration of digoxin or adrenaline or by increase in peripheral resistance are associated with increases in the secretion of HS.

4. Negative inotropic effects produced by high concentrations of procaine hydrochloride or by increase in venous return without change in external work are associated with decrease in HS secretion.
The perceived spatial frequency shift: evidence for frequency‐selective neurones in the human brain
Authors: Blakemore Colin , Nachmias Jacob , Sutton Peter
Published: December 2014

1. Prolonged observation of a high‐contrast grating pattern causes an apparent shift in the spatial frequency of gratings subsequently viewed with the same retinal region. Gratings of higher and lower frequency than the adapting pattern seem, respectively, higher and lower than in fact they are.

2. There is no significant after‐effect at the adapting frequency itself nor at frequencies more than two octaves away.

3. For very low adapting frequencies, the after‐effect remains centred at about 3·0 c/deg and declines in strength as the adapting frequency is successively lowered.

4. The magnitude of the after‐effect increases with the contrast of the adapting grating and the length of time spent in adaptation. It takes several hours to recover completely from 30 min adaptation.

5. The phenomenon is orientation‐specific: a horizontal adapting grating has no effect on vertical test gratings. There is partial interocular transfer of the after‐effect.

6. These findings provide further evidence that the visual system of man, like those of the cat and the monkey, contains neurones selectively sensitive to the orientation and dimensions of retinal images, and that these adaptable cells are actually involved in the encoding and perception of the size of simple patterns.
Post‐tetanic hyperpolarization produced by an electrogenic pump in dorsal spinocerebellar tract neurones of the cat
Authors: Kuno M. , Miyahara J. T. , Weakly J. N.
Published: December 2014

1. Hyperpolarization following single and repetitive excitation of dorsal spinocerebellar tract (DSCT) neurones of the cat was studied by intracellular recording.

2. Hyperpolarization following an antidromic action potential consisted of an initial, brief phase (undershoot) and a late, prolonged phase. The latter hyperpolarization was independent of the membrane potential, whereas the former was reversed in polarity by hyperpolarizing pulses applied across the DSCT cell membrane.

3. DSCT neurones showed a prolonged hyperpolarization after a train of antidromic action potentials. The amplitude and duration of the hyperpolarization were dependent on the number and the frequency of action potentials. A similar hyperpolarization was observed following a train of impulses evoked by depolarizing pulses applied through the intracellular electrode.

4. There was no detectable conductance change during the post‐tetanic hyperpolarization. The latter showed no reversal potential when the membrane potential was altered.

5. The half‐decay time of the post‐tetanic hyperpolarization was lengthened when the cord temperature was lowered. The temperature coefficient (Q10) was 2·4 within the range of 31–40° C.

6. The amplitude of the undershoot following each action potential was assumed to provide a criterion for the accumulation of the extracellular K+. Alterations in the amplitude of undershoots during repetitive excitation suggested that the duration of post‐tetanic hyperpolarization depends on the accumulation of extracellular K+ as well as of intracellular Na+ associated with a train of impulses.

7. It is suggested that post‐tetanic hyperpolarization is produced by an electrogenic sodium pump. A possible significance of such a hyperpolarization in impulse coding is discussed.
Response characteristics of muscle afferents in the domestic duck
Authors: Dorward Patricia K.
Published: December 2014

1. Response patterns of 116 muscle stretch receptor units isolated from the sciatic nerve of the duck have been studied, and the units classified as muscle spindles and tendon organs.

2. Units classified as spindles had low threshold tensions for maintained discharge. From conduction—velocity measurements, the calculated fibrediameter spectrum appears to be unimodal, ranging from 5 to 11–12 μm.

3. Spindle units showed essentially ‘in parallel’ behaviour, though increase in initial tension often led to the appearance of ‘in series’ responses. Although apparent ‘α‐excitation’ during maximal tetanic contractions was a common occurrence, no direct evidence of α‐innervation of spindles was obtained.

4. Evidence has been obtained for motor innervation of spindles by fibres distinct from those constituting the alpha supply to extrafusal muscle fibres. Afferent response attributable to this fusimotor innervation is influenced by initial tension and stimulus‐frequency. Electrical thresholds for fusimotor responses ranged from 1·1 to 4·03 times α maximum.

5. Tendon organ units consistently showed ‘in series’ response patterns during muscle contractions. They were not influenced by stimulation of the high‐threshold efferent nerve supply to the muscles.

6. Threshold tensions required for maintained discharge in tendon organ units from m. gastrocnemius pars lateralis were characteristically high; however, many units from m. flexor perforans et perforatus d. 3 had unexpectedly low mechanical thresholds. The calculated fibre‐diameter spectrum for tendon organ units is unimodal, ranging from 4–7 to 10–11 μm. As in mammals, they contribute to the coarse‐fibre component in the muscle nerve and include the fastest fibres present.
Cat colour vision: evidence for more than one cone process
Authors: Daw N. W. , Pearlman A. L.
Published: December 2014

1. The ability of cats to distinguish colours was investigated at mesopic and photopic levels to test the hypothesis that cats discriminate wavelength by using rods in conjunction with a single type of cone.

2. Cats were trained to distinguish red from cyan, and orange from cyan at the mesopic level. They retained the ability to make this discrimination when the coloured stimuli were placed against a background bright enough to saturate the rods.

3. One cat was also tested after being exposed to a bright white light of 9000 cd/m2 for a period of 5 min, and found able to distinguish red from cyan.

4. These results suggest that cats have more than one type of cone. Subsequent recordings from single units in the lateral geniculate nucleus showed that there are rare opponent colour units in layer B with input from a green‐absorbing cone and a blue‐absorbing cone.
Temperature dependence of non‐electrolyte and sodium permeability in giant axon of squid
Authors: Hidalgo Cecilia , Latorre Ramón
Published: December 2014

1. The efflux of [14C]urea was measured in micro‐injected axons at 18° C. A permeability constant for urea of (0·55 ± 0·18) × 10−6 cm/sec was calculated from these experiments.

2. The influxes of urea, thiourea, ethylene glycol, urethane and toluene were measured in perfused axons at 18 ± 1° C. The permeability constants obtained from these determinations increased in the order listed, from (0·76 ± 0·19) × 10−6 cm/sec for urea to 0·80 × 10−4 cm/sec for toluene.

3. The influxes of tritiated water and sodium ions at 18° C were measured in perfused axons. An average permeability of (0·78 ± 0·22) × 10−4 cm/sec for titriated water and an average influx of 23 ± 6 p‐mole/cm2 sec for sodium were obtained.

4. Lowering the temperature of the external sea‐water bathing the axon from 18 to 5° C produced a decrease of 12% in the permeability of toluene, 30% for tritiated water and urethane, 55% for ethylene glycol and urea and 60% for thiourea. There was a 50% reduction in the influx of sodium for this same temperature change.

5. The results obtained with the effect of temperature on permeabilities suggest that the axonal membrane has a non‐homogeneous composition. A model based on the assumption of structured aqueous channels in the membrane is postulated.
The effect on respiration of abrupt changes in carotid artery pH and PCO2 in the cat
Authors: Band D. M. , Cameron I. R. , Semple S. J. G.
Published: December 2014

1. An in vivo pH monitoring technique was used to assess changes in pH, and by inference changes in PCO2, in the carotid artery of anaesthetized cats. The changes in carotid artery pH and respiration following abrupt injections of various acids into the carotid artery or aorta were investigated.

2. Injections of saline equilibrated with 100% CO2, timed to produce changes at the carotid body chemoreceptors during early inspiration caused an increase in the tidal volume of that breath. The amplitude and rate of change of the pH changes so produced were comparable with those of the oscillations in pH produced by respiration itself.

3. The respiratory responses to injection of saline equilibrated with 100% CO2 occurred whether the animal was breathing air or 100% O2.

4. Injections of lactic or hydrochloric acid were without an effect on respiration, except when pH changes larger than 0·1 pH unit were produced. A NaHCO3 solution equilibrated with 30% CO2 stimulated respiration, even though the solution was alkaline to the cat's arterial blood and induced an alkaline change in arterial pH.

5. Infiltration of the carotid sinus nerve area with procaine temporarily abolished the respiratory response to injections of saline equilibrated with 100% CO2.
Effects of nephrectomy and KCl on transmembrane potentials, intracellular electrolytes, and cell pH of rat muscle and liver in vivo
Authors: Williams J. A. , Withrow C. D. , Woodbury D. M.
Published: December 2014

1. The ability of 24 hr nephrectomy and KCl to raise plasma K+ concentration was used to correlate transmembrane resting potential (RP), ionic gradients, and cell pH (DMO method) in rat muscle and liver in vitro.

2. Effects of 24 hr nephrectomy on electrolytes included a rise in plasma K+ and fall in Na+, with a rise in intracellular K+ and fall in intracellular Na+ in both liver and muscle. Intracellular Cl− concentration rose in muscle and decreased in liver.

3. Measured muscle RP was decreased from −91 to −77 mV by 24 hr nephrectomy, with the RP predictable from the Goldman equation for Na+ and K+ with PNa/PK = 0·01 and Cl− behaving as if passively distributed.

4. Measured hepatic RP was increased from −43 to −48 mV by 24 hr nephrectomy, with a change in ionic permeability or activation of an electrogenic pump necessary to explain the results.

5. Plasma acid—base changes consisted of metabolic acidosis with partial respiratory compensation. Cell pH rose slightly in both liver and muscle; the H+ gradient remained constant in muscle but increased slightly in liver.

6. KCl was injected into intact rats while the RPs were continuously measured in muscle or liver. Muscle RP was found to decrease and hepatic RP to increase along a similar time course.

7. Infusion of KCl into the portal vein led to an increase in the hepatic RP for values of hepatic venous K+ of 15–25 m
M, whereas infusion sufficient to increase the hepatic venous K+ concentration to 30–40 m
M produced no change or a slight decrease in hepatic RP.

8. The rat muscle RP can be adequately described by the Goldman equation for Na+ and K+, whereas the hepatic RP may well have both diffusion and electrogenic components which respond differently to an increase in plasma K+ concentration.
Rat gastric acid secretion studies with histamine and synthetic gastrin‐like pentapeptide
Authors: James R. M. V.
Published: December 2014

1. Gastric acid secretion was measured in the urethane anaesthetized rat whilst maintaining a recirculated gastric perfusion fluid at pH 4.

2. The latent period of onset of secretion following single intravenous doses of histamine and pentapeptide in combination was significantly shorter than that following either stimulant alone.

3. When administered over a period of 2 hr the maximal steady rate of secretion in response to pentapeptide was 75% of that to histamine.

4. Acid stimulatory effects were additive both when the drugs were given concurrently over a 2 hr period and when one was administered after a maximal response had been obtained to the other.

5. Although there is some evidence to indicate that histamine and pentapeptide might be initiating acid secretion by different mechanisms it is suggested that they may not be acting with total independence.
Abnormalities of 5‐hydroxytryptamine uptake and binding by blood platelets from children with Down's syndrome
Authors: Boullin D. J. , O'Brien R. A.
Published: December 2014

1. Blood platelets from normal children and children with the trisomy 21 form of Down's syndrome (mongolism) were studied to determine the cause of the well established reduction in platelet 5‐HT in the disease.

2. Concentrations of endogenous 5‐HT in the platelets from mongols were 25·3% of the concentrations found in normal children.

3. The net accumulation of 5‐HT in the mongol cells was decreased to 52·7% of normal. This reduction was probably due, in part, to a defect in 5‐HT transport, because the initial rates of 5‐HT uptake at plasma concentrations of 10−6 and 10−5
M were significantly slower.

4. Experiments on the efflux of 5‐HT from mongol platelets loaded with amine showed that the rate of loss was initially 2·6 and later 7·8 times faster than normal.

5. Platelet ATP in mongol cells was 26% of normal, and the reduction of ATP and 5‐HT was in the molar ratio of 3:1.

6. It is considered that the low platelet 5‐HT in Down's syndrome is due to a defective 5‐HT transport mechanism and impaired 5‐HT binding, resulting from a reduction in the essential binding substance, ATP.
The role of sodium and calcium ions in the hypothalamus in the control of body temperature of the unanaesthetized cat
Authors: Myers R. D. , Veale W. L.
Published: December 2014

1. Isolated regions of the anterior, posterior and other areas of the hypothalamus of the unanaesthetized cat were perfused by means of push‐pull cannulae lowered through permanently implanted guide tubes. Each site was perfused for a 30 min interval at a rate of 50 μl./min. Concentrations of sodium, calcium, potassium and magnesium ions in the perfusate were altered selectively.

2. Sodium ions in a concentration which varied from 13·6 to 68·0 m
M in excess of the level in extracellular fluid caused a steep rise in the temperature of the cat when the solution was perfused at sites located within the posterior hypothalamic area. Shivering, vasoconstriction, and piloerection accompanied the increase in temperature. When the chloride was replaced in the perfusate by the toluene‐p‐sulphonate salt of sodium, the hyperthermia was equally intense. Solutions containing excess sodium ions perfused within the anterior and other hypothalamic areas produced either a slight fall or rise in temperature as well as other physiological changes.

3. Calcium ions in a concentration which varied from 2·6 to 10·4 m
M in excess of the physiological level perfused at the same sites within the posterior region of the hypothalamus produced a sharp fall in body temperature, which was accompanied by vasodilatation and a decrease in the activity of the cat. When solutions containing excess calcium were perfused in the anterior and other hypothalamic areas, no consistent change in temperature occurred.

4. Potassium or magnesium ions in concentrations which varied from two to ten times the level in extracellular fluid had virtually no effect on the temperature of the cat when they were perfused in the anterior, posterior or other areas of the hypothalamus.

5. We conclude that the constancy in the ratio between sodium and calcium ions in the posterior hypothalamus may be the inherent mechanism by which the set‐point for body temperature is determined.
Ionic mechanism of post‐tetanic potentiation at the neuromuscular junction of the frog
Authors: Weinreich D.
Published: December 2014

1. Transmitter release at the frog neuromuscular junction was studied after sodium influx in nerve and muscle was abolished by tetrodotoxin (TTX).

2. In the presence of TTX, transmitter release evoked by electrotonic depolarization of the nerve terminal was potentiated following presynaptic stimulation by a train of depolarizing pulses.

3. Post‐tetanic potentiation (PTP) in the presence of TTX appeared no different from that observed in control (TTX‐free) muscles. The magnitude as well as the time course of PTP was dependent on the number of tetanic stimuli and on temperature of the medium when sodium influx was inhibited by TTX.

4. When external sodium was replaced by an isotonic calcium chloride solution PTP was still present. Ionophoretic application of calcium during tetanic nerve stimulation and increase in the intensity of the depolarizing pulse of the train, which presumably enhances calcium movements into nerve endings, caused a large increase in the duration of PTP.

5. It is concluded that PTP does not require sodium but depends on movement of calcium from the external medium into the nerve terminal.
The relative contribution of K and Cl to the total increase of membrane conductance produced by adrenaline on the smooth muscle of guinea‐pig taenia coli
Authors: Ohashi H.
Published: December 2014

1. The relative contribution of K and Cl to the total increase of membrane conductance produced by adrenaline on the smooth muscle of guinea‐pig taenia coli has been investigated. Constant current pulses were applied with a pair of large external electrodes, the voltage change was recorded with an intracellular micro‐electrode, and the change in the size of the electrotonic potential by adrenaline was measured.

2. Adrenaline hyperpolarized the membrane by about 8 mV with a range from 5 to 15 mV and it reduced both the size and the time course of the electrotonic potential. On the average the size was reduced to 65 ± 1·8% (n = 75) of the normal size, from which a decrease of the membrane resistance to 45 ± 2·2% was calculated, or 48% allowing for the spatial decay.

3. The magnitude of the reduction of the electrotonic potential caused by adrenaline was decreased as the concentration of K or Cl ions in the medium was reduced by substituting NaCl or sucrose for KCl or an impermeant anion, benzene sulphonate, for Cl ions. The adrenaline effect remained unaltered when the NaCl was replaced with Tris‐Cl.

4. It is therefore concluded that adrenaline opens the ion pathways mainly for K and Cl.

5. On the basis of the changes in potential and in conductance caused by adrenaline, the equilibrium potential for its action was calculated as − 75 mV.

6. The ratio of the Cl component to the K component of the additional conductance increase was obtained as 0·36 using the calculated equilibrium potential and the Nernst potentials for K (−91 mV) and Cl (‐31 mV).
The contribution of mechanical factors to the early adaptation of the spindle response
Authors: Husmark I. , Ottoson D.
Published: December 2014

1. Adaptation in terms of the early fall of the receptor potential was studied in isolated frog spindles. The contribution of gross mechanical changes to the decline of the response was determined by comparing the responses obtained under constant length and under constant tension.

2. It was found that the early adaptation under constant stretch increased with increasing lengthening of the spindle for stretches up to 25–30% of the resting length and decreased with still stronger stretches. When the spindle was stretched by 100% or more the static phase of the receptor potential reached nearly the same height as the dynamic peak and the early adaptation approached zero.

3. The early adaptation decreased with decreasing velocity of linearly rising stretch and approached zero for stretches below about 0·5 mm/sec.

4. For different strengths of a steplike stretch the amount of early adaptation was linearly related to the fall in tension over the same period. The relative amount of tension fall, however, was always less than the corresponding fall of the response.

5. The early adaptation was 15–20% smaller under constant tension than under constant length for stretches below the level giving the maximum dynamic peak.

6. The results suggest that a comparatively small amount of the early adaptation of the spindle response to constant stretch is related to gross alterations in length in different regions of the spindle. The main part of the adaptive fall of the response is probably related to functional properties of the sensory membrane and to the ionic mechanism underlying the production of the receptor potential.
The effect of light chloralose and pentobarbitone anaesthesia on the acid—base state and oxygenation of arterial blood in dogs
Authors: Ledsome J. R. , Linden R. J. , Norman J.
Published: December 2014

1. The effects of light anaesthesia of approximately 8 hr duration using either pentobarbitone or chloralose on the acid—base balance and oxygenation of arterial blood were determined in dogs breathing spontaneously.

2. With pentobarbitone anaesthesia there was a slight initial respiratory acidaemia.

3. With chloralose there was a non‐respiratory acidaemia which was probably the result of using an unbuffered solvent.

4. Changes in the acid—base balance and the oxygen concentration of the arterial blood over the course of each experiment were minimal.

5. In one animal a pH of 7·07 was recorded; in others the oxygen tension on occasion was between 50 and 60 mm Hg. The value of monitoring the acid—base state and the oxygenation of blood in experimental preparations is discussed.
Biophysical properties of the longitudinal smooth muscle of the guinea‐pig rectum
Authors: Kuriyama H. , Mekata F.
Published: December 2014

1. The membrane properties of the longitudinal muscle layer of the guinea‐pig rectum were studied in hypertonic solution (twice the normal Krebs by addition of sucrose) by the micro‐electrode technique. To produce the electrotonic potential and spike, stimulating partitions were used.

2. Hypertonic solution hyperpolarized the membrane and increased the membrane resistance. However, no change in the space constant was observed before and after treatment with hypertonic solution.

3. The appearance and amplitude of the spike became regular after treatment with hypertonic solution and appearance of the overshoot was consistent.

4. The characteristic constants and the conduction velocity were measured in hypertonic solution.

(i) The space constant of the membrane was 0·81 mm, the time constant of the electrotonic potential was 83·7 msec and the time constant of the foot of the propagated spike was 8·8 msec.

(ii) The conduction velocity of the excitation measured by insertions of the two micro‐electrodes was 4·4 cm/sec.

(iii) The chronaxie of the membrane was 71·3 msec.

5. The results obtained from the present experiments were discussed in relation to the cable theory, and it was concluded that the passive properties of the membrane of the rectal smooth muscle could be explained by the cable equations.

6. The specificities of the electrical properties of rectal smooth muscle were compared with muscle from other regions of the alimentary canal.
Lack of involvement of fusimotor activation in movements of the foot produced by electrical stimulation of monkey cerebral cortex
Authors: Lewis M. McD. , Porter R.
Published: December 2014

1. Contractions of the small muscles of the foot producing flexion and adduction of the hallux were elicited by brief trains of electrical stimulation of a motor point on the precentral gyrus of anaesthetized monkeys and these contractions were recorded myographically.

2. The cortical stimulus intensities necessary to produce minimal muscle contractions were measured for different frequencies of stimulation at the cortical point, and the latency of the minimal muscle contraction was measured in each case.

3. Section of all the relevant lumbar and sacral dorsal roots had no effect on the threshold stimulus currents necessary to produce minimal contractions or on the latencies of these responses. Hence, in the anaesthetized monkey, the power of the cortico‐fusimotor activity stirred up by electrical stimulation of the cortex is inadequate to influence significantly the motor responses of the most accessible muscles.
The effect of insulin and insulin deficiency on the transport and metabolism of glucose by rat small intestine
Authors: Leese H. J. , Mansford K. R. L.
Published: December 2014

1. Insulin deficiency induced by anti‐insulin serum or streptozotocin increased glucose absorption, as measured in everted sacs of rat upper ileum incubated for 30 min with oxygenated Krebs—Henseleit bicarbonate medium.

2. Everted sacs prepared from the terminal ileum of insulin‐deficient rats were able to accumulate glucose against a concentration gradient (i.e. development of active glucose transport).

3. In experimental diabetes induced by streptozotocin, everted sacs of upper ileum showed increased 3‐methyl glucose active transport, and sacs of terminal ileum showed development of 3‐methyl glucose active transport.

4. Lactic acid formation during the absorption of both glucose and 3‐methyl glucose was increased approximately twofold in everted sacs of insulin‐deficient animals.

5. Insulin added at 100 mu./ml. to the incubating media of everted sacs prepared from insulin‐deficient rats did not result in a reduction of glucose absorption or reverse the other effects.

6. Fluoride (5 × 10−3
M) added to the serosal and mucosal media of sacs of terminal ileum prepared from insulin‐deficient rats decreased [14C]CO2 formation from [U‐14C]glucose and lactate formation during glucose absorption, but was unable to reverse the effect of insulin deficiency on glucose active transport.

7. The effects of insulin deficiency induced by streptozotocin were more striking than those induced by anti‐insulin serum.

8. Everted sacs prepared from rats starved for 3 days showed increased glucose active transport accompanied by diminished conversion of [U‐14C]glucose to [14C]CO2.

9. The possible role of hexokinase is discussed in relation to these findings.
Prediction of repetitive firing behaviour from voltage clamp data on an isolated neurone soma
Authors: Connor J. A. , Stevens C. F.
Published: December 2014

1. Membrane parameters of an isolated neural cell body have been determined by voltage clamp analysis. Data are expressed as membrane ion‐specific conductances, leak conductance, and capacitance.

2. Three ionic currents are present: Inward, II; and two operationally distinct outward currents, IK and IA. Both outward currents are apparently carried by potassium ions.

3. Hodgkin—Huxley‐like equations were solved for the discharge of two sequential action potentials in response to a constant stimulus current. The digital computer solutions are compared with action potential data recorded from the investigated cell.

4. The computed and experimentally measured relationships between firing frequency and stimulus current intensity are compared and are linear over the same portion of the total frequency range.

5. Cell behaviour in the latter part of the interspike interval is dominated by the conductance gA while gNa and gK largely determine the character of the action potential and the initial portion of the interspike interval.

6. Prehyperpolarization of the membrane activates gA and the membrane response to depolarizing current differs markedly from the response elicited when no prehyperpolarization is imposed.
Effect of prostigmine on the time course of the end‐plate potential in the rat diaphragm
Authors: Kuba K. , Tomita T.
Published: December 2014

1. End‐plate potentials (e.p.p.s) were evoked by applying brief depolarizing pulses to motor nerve endings in a phrenic nerve—diaphragm preparation paralysed by tetrodotoxin (TTX). Without prostigmine, the time to decay from the summit of the e.p.p. to half amplitude (the half‐decay time) was roughly constant (2–4 msec) when the amplitude was increased by increasing stimulus intensity or duration.

2. In the presence of prostigmine (5 × 10−7‐2 × 10−5 g/ml.), the falling phase of the e.p.p. was different in time course depending on the amplitude. The half‐decay time had, very roughly, an exponential dependence on amplitude. The relationship was not affected by increasing the TTX or the prostigmine concentration, but
D‐tubocurarine (10−6 g/ml.) made the relationship less steep.

3. Hyperpolarizing current pulses, applied after the depolarizing current pulse which produced the e.p.p., had no effect on the time course of the e.p.p. No facilitating effect of repetitive stimulation was observed without prostigmine up to a frequency of 40 c/s, but there was a strong effect of repetitive stimulation in increasing the amplitude and duration of the e.p.p. in the presence of prostigmine. During stimulation, the endplate was continuously depolarized by 10–20 mV, and its recovery was very slow, the half‐decay time being about 3 sec.

4. The half‐decay time of the acetylcholine potentials produced by iontophoretically applied acetylcholine was almost independent of the amplitude, with or without prostigmine, although it increased the amplitude of the potential and prolonged the falling phase.

5. Possible mechanisms for the alteration of the falling phase of the e.p.p. were discussed. It is speculated that, in the presence of prostigmine, a process which is involved in a conductance increase of the post‐synaptic membrane, after acetylcholine has combined with the receptor molecules, is the main factor determining the falling phase of the e.p.p.
A search for odour encoding in the olfactory lobe
Authors: Yamada Minoru
Published: December 2014

1. Studies were made of quality coding in the olfactory lobe of the insect by recording extracellular action potentials from single cells.

2. Listing cell spectra permits to distinguish two main groups of cells, namely, ‘odour specialist’ which respond very specifically to biologically important substances and ‘odour generalist’ which respond to a large variety of odorants (thirty‐two compounds) in an excitatory or inhibitory manner, or not responding at all.

3. Among more than fifty cells of the ‘odour generalists’, very few had similar, or identical, reaction spectra to an arbitrarily chosen set of thirty‐two odorants, while the ‘odour specialists’ are like each other in their response spectra.

4. There was an indication of a regional and layer differentiation of response in the lobe to the sex attractant.

5. ‘On’, ‘on—off’, and ‘off’ response types, as well as several variations on these response types, were found in single units during odour presentations.

6. Differences in patterning of excitation for each of the thirty‐two compounds can be readily detected by the comparison of the relative amounts of activity in each of the eighty‐one units tested. It is therefore concluded that the mechanism of odour encoding at the olfactory lobe may involve the linear combinations of every olfactory neurone's activity result ing in a unique across‐lobe pattern of discharges (‘odour code pattern’) for each particular odorant.

7. If it follows that odour discrimination by the lobe depends on such differences of ‘odour code patterns’, it would be possible then to distinguish very many odorants simply by having very many neurones possessing differential odour specificity.
Noradrenaline release from isolated muscles of the nictitating membrane of the cat
Authors: Langer S. Z. , Vogt Marthe
Published: December 2014

1. When the splanchnic nerves were stimulated in the cat for periods of up to 2 hr, the amount of adrenaline taken up by the nictitating membrane was very small; the highest figure was 0·37 μg/g, corrected for losses.

2. The noradrenaline (NA) stores of the isolated medial muscle of the nictitating membrane were labelled with [3H]NA, and field stimulation of single muscles was carried out in a small organ bath. A stimulation period of 5 min with supramaximal shocks delivered at a frequency of 25/sec produced a mean release of NA into the bath fluid of 0·46 ± 0·13 μg/g (uncorrected). Phenoxybenzamine, 10 μg/ml., increased this figure by a factor of 2‐3·6. When corrections were made for the amount of transmitter metabolized before it could be collected, 47% of the tissue content of NA were shown to be released during the 5 min stimulation of the normal membrane, and about 55% in the presence of phenoxybenzamine. Prolonged stimulation of a phenoxybenzamine‐treated membrane was apt to lead to loss of tissue stores of NA.

3. Calculation of the degree of labelling of the NA in the tissue, and of NA released by stimulation, indicated that about 21% of endogenous NA had been replaced by labelled compound both in the tissue and in the overflow.

4. Transmitter release per pulse was estimated by applying 720–1330 shocks at frequencies of 4 or 6/sec to membranes exposed to phenoxybenzamine. Mean release of NA per shock and per g tissue was 1·3 ng (corrected for losses). This represents 3·5 × 10−4 of the tissue content determined at the end of the experiment.
Peripheral nerve activity in response to heating the cat's skin
Authors: Stolwijk Jan A. J. , Wexler Ira
Published: December 2014

1. The sensitivity of the cat hind‐limb skin to non‐noxious heating was studied. Neural activity was recorded with micro‐electrodes from intact multifibre fascicles of the saphenous nerve while the skin was actively heated or passively cooled.

2. Moderate warming from indifferent temperatures of 30–34° C to temperatures of 38–39° C produced a reduction in the total rate of firing of the integrated discharge. Firing picked up sharply again at skin temperatures above 39° C. A considerable fraction of the impulse activity elicited above 39° C was carried by C‐fibre afferents.

3. Prolonged heating to temperatures in excess of 45° C rendered the skin insensitive to further non‐noxious heating or to touch.

4. The neural response to a step increase in skin temperature consisted of a delayed overshoot and then a steady‐state level of firing. Steady‐state firing was proportional to the level of skin temperature.

5. Nerves whose C‐fibre input to the spinal cord had been selectively blocked showed a potentiation of the neural response to skin heating.

6. The sensitivity of hind‐limb skin to heating, as judged by the character of the multifibre discharge, appears similar to that reported for a highly warm‐sensitive region of the nose.
Analysis of the effluxes of sodium, potassium and chloride ions from smooth muscle in normal and hypertonic solutions
Authors: Brading Alison F.
Published: December 2014

1. Efflux curves of 24Na, 42K and 36Cl from the guinea‐pig taenia coli were obtained in normal Krebs solution, and in hypertonic Krebs solution in which the osmolarity had been doubled by the addition of sucrose.

2. The efflux curves were complex, and in order to get average curves each was analysed as the sum of three exponential terms, and average curves were constructed from the means of the constants found.

3. In order to estimate the membrane permeability to the ions, it was necessary to make assumptions as to the distribution of ions in the tissue. Several models have been examined and the predictions of the models with respect to the membrane properties were compared with the data obtained by using electrophysiological methods by other workers.

4. It was found that reasonable predictions of membrane properties could only be made using models in which the majority of the rapidly exchanging sodium is considered to be extracellular. This amount of sodium is more than can be accounted for as freely dissolved in the extracellular water.

5. A possible interpretation of the ion exchange and distribution would be to suppose that some proportion of the three ions is contained in an extracellular compartment not available to the normal extracellular markers, and limited in its exchange by the rate of diffusion in the extracellular phase, and that the truly intracellular fractions of the tissue ions do not exchange with the external solution in a simple exponential manner, but in a manner described by an aggregate of exponential terms due to inherent variation in the permeabilities of the individual cell membranes.

6. There is no evidence for any change in the membrane permeabilities to sodium and potassium in hypertonic solution, but there is evidence for a decrease in chloride permeability in this solution.
Heat production in the gastro‐intestinal tract of the dog
Authors: Durotoye A. O. , Grayson J.
Published: December 2014

1. Mean temperature from the lumen of the dog duodenum was 0·6° C hotter than aorta. Ileum, stomach and large intestine were slightly cooler but still about 0·5° C hotter than aorta.

2. Portal vein averaged 0·35° C hotter than the aorta.

3. From portal blood flow data and aortic—portal temperature differentials heat production was calculated for the 10 kg dog as 3·4 kcal/hr.

Evidence is adduced to show in these experiments that the gastro‐intestinal tract produced 60% more heat than the liver.

Total splanchnic heat production was about 33% of the total bodily heat production.

4. The following procedures were carried out: adrenergic neurone blockade, atropine administration, vagotomy, prior starvation, bowel sterilization. All were without effect. It was concluded that smooth muscle activity, active transport or microbiological activity were unlikely to be sufficient to account for the high level of heat production.

5. It was suggested that mucosal activity was the most likely source of heat. The possible involvement of unidentified metabolic pathways was discussed but oxidative mechanisms alone were shown not to be sufficient explanation.

6. Since the rectal temperature was not significantly different from aortic it was concluded that the rectum was metabolically inactive and usually passively assumed the temperature of its blood supply.
The influence of the chloride gradient across red cell membranes on sodium and potassium movements
Authors: Cotterrell D. , Whittam R.
Published: December 2014

1. A study has been made to see whether active and passive movements of sodium and potassium in human red blood cells are influenced by changing the chloride gradient and hence the potential difference across the cell membrane.

2. Chloride distribution was measured between red cells and isotonic solutions with a range of concentrations of chloride and non‐penetrating anions (EDTA, citrate, gluconate). The cell chloride concentration was greater than that outside with low external chloride, suggesting that the sign of the membrane potential was reversed. The chloride ratio (internal/external) was approximately equal to the inverse of the hydrogen ion ratio at normal and low external chloride, and inversely proportional to external pH. These results show that chloride is passively distributed, making it valid to calculate the membrane potential from the chloride ratio.

3. Ouabain‐sensitive (pump) potassium influx and sodium efflux were decreased by not more than 20 and 40% respectively on reversing the chloride gradient, corresponding to a change in membrane potential from −9 to +30 mV. In contrast, passive (ouabain‐insensitive) movements were reversibly altered — potassium influx was decreased about 60% and potassium efflux was increased some tenfold. Sodium influx was unaffected by the nature of the anion and depended only on the external sodium concentration, whereas ouabain‐insensitive sodium efflux was increased about threefold. When external sodium was replaced by potassium there was a decrease in ouabain‐insensitive sodium efflux with normal chloride, but an increase in low‐chloride medium.

4. Net movements of sodium and potassium were roughly in accord with the unidirectional fluxes.

5. The results suggest that reversing the chloride gradient and, therefore, the sign of the membrane potential, had little effect on the sodium pump, but caused a marked increase in passive outward movements of both sodium and potassium ions.
The synthesis, turnover and release of surplus acetylcholine in a sympathetic ganglion
Authors: Collier B. , Katz H. S.
Published: December 2014

1. Surplus acetylcholine (ACh) is the extra ACh that accumulates in cholinergic nerve endings when they are exposed to an anticholinesterase agent. The synthesis and turnover of this ACh was examined in the cat's superior cervical ganglion.

2. Surplus ACh did not accumulate in chronically decentralized ganglia perfused with eserine‐choline‐Locke solution, and this shows that it is stored in presynaptic nerve terminals.

3. Surplus ACh accumulated more rapidly in ganglia perfused with eserine than in ganglia perfused with neostigmine or with ambenonium; accumulation was delayed by 45–60 min when a quaternary anticholinesterase was used. However, the release of ACh upon preganglionic nerve stimulation was the same during perfusion with eserine, neostigmine or ambenonium. It is concluded that intracellular acetylcholinesterase normally destroys surplus ACh, whereas extracellular enzyme destroys released ACh.

4. When ganglia were perfused with [3H]choline and eserine, the surplus ACh that accumulated was labelled but its specific radioactivity was only 38% of that of the choline added to the perfusion fluid.

5. Surplus ACh was not released by nerve stimulation and was not mobilized for release during, or after, prolonged nerve stimulation. It is concluded that ACh released by nerve impulses is replaced by synthesis at the site of ACh storage and not by movement of ACh from the surplus pool.

6. The accumulation of surplus ACh no more than doubled the total ACh content of ganglia, but turnover of ACh continued when the total amount was constant. Surplus ACh may contribute to spontaneous ACh output from eserinized preparations.

7. When ganglia were perfused with a medium containing high K+ (56 m
M), surplus ACh was released.
The transfer of free α‐amino nitrogen across the placental membrane in the guinea‐pig
Authors: Reynolds Margaret L. , Young Maureen
Published: December 2014

1. Transfer of endogenous α‐amino nitrogen from the maternal to foetal side of the placental membrane was studied in the foetal guinea‐pig placenta perfused, in situ via the umbilical vessels, with an artificial fluid. Changes in maternal placental blood flow were followed by measuring the transfer of antipyrine into the perfusate.

2. Active transport by the membrane was demonstrated under these conditions by observing the increased ratio of
L/D leucine appearing in the perfusate in comparison with the maternal plasma ratio.

3. Reduction in maternal placental flow following haemorrhage was associated with a fall in transfer of amino nitrogen to about half of the control values.

4. The concentration of α‐amino nitrogen in the perfusate was inversely proportional to the foetal placental flow which had a smaller influence on amino nitrogen transfer per min than did the maternal blood flow.

5. Hypoxia and some inhibitors of oxidative metabolism were without influence on the transfer of α‐amino nitrogen in this preparation.
Effect of injury on shivering thermogenesis in the rat
Authors: Stoner H. B.
Published: December 2014

1. Shivering in response to changes in ambient or core temperature has been measured in control rats and rats injured by bilateral hind‐limb ischaemia, both with and without fur.

2. Removal of the fur increased the threshold ambient temperature for the onset of shivering.

3. This threshold was lower than in uninjured controls during the latter half of a 4 hr period of bilateral hind‐limb ischaemia in rats with or without fur.

4. The threshold was also lower than in uninjured controls after the period of bilateral hind‐limb ischaemia but was not significantly different from that during the period of ischaemia.

5. The alterations in threshold were not accompanied by any significant changes in the slope of the regression line relating intensity of shivering and ambient temperature.

6. When the core temperature fell after limb ischaemia to levels which provoked shivering in uninjured controls, no shivering was seen in the injured rats.

7. These results are interpreted as further evidence for the lowering of the ‘set‐point’ for thermogenesis after injury in the rat and are discussed in relation to the changes in body temperature after injury in that species.
The effects of electrical stimulation of the distal end of the cut sinus and aortic nerves on peripheral arterial chemoreceptor activity in the cat
Authors: Neil E. , O'Regan R. G.
Published: December 2014

1. In anaesthetized cats, stimulation of efferent components of the carotid sinus or aortic nerves depressed chemoreceptor discharge from the relevant chemoreceptor afferents. The local application of 2% procaine hydrochloride to the sinus nerve trunk, peripheral to the site of the stimulating electrodes and proximal to that of the afferent nerve twig, abolished the depression of afferent chemoreceptor discharge caused by electrical stimulation; on washing the procaine away electrical stimulation once more induced depression of chemoreceptor discharge.

2. The depressant effect of efferent stimulation on carotid chemoreceptor activity was still seen during complete carotid glomeral ischaemia. Atropine given by close intra‐arterial injection to the carotid body did not affect the depressant influence of efferent sinus nerve stimulation on carotid body chemoreceptor discharge.

3. Stimulation of the sinus nerve efferents usually increased carotid body blood flow. Close arterial injection of atropine abolished this effect.

4. The responses of glomeral blood flow and carotid chemoreceptor activity to efferent stimulation of the cut sinus nerve were not temporally related. It seems improbable that the depressant effect of such stimulation on chemoreceptor discharge was due to alterations of glomeral blood flow.

5. Stimulation of the peripheral end of the cervical vagus in atropinized cats reduced chemoreceptor activity recorded in the ipsilateral aortic nerve.