bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of fast and slow alpha motoneurones following motor reinnervation
Authors: Kuno M. , Miyata Y. , Muñoz‐Martinez E. J.
Published: December 2014

1. The properties of medial gastrocnemius (fast alpha) and soleus (slow alpha) motoneurones of the cat were examined with intracellular electrodes 33–154 days after self‐ or cross‐union of the muscle nerves.

2. The original properties of fast and slow alpha motoneurones measured in terms of the axonal conduction velocity, the duration of after‐hyperpolarization and the overshoot amplitude were restored at least in part after self‐union of the muscle nerves.

3. Slow alpha motoneurones recovered their original properties whether the muscle nerve was united to the original, slow red muscle or to the fast pale muscle. In two animals, some of the fast muscle fibres seemed to be doubly innervated by both fast and slow alpha motoneurones.

4. The degree of restoration of the original motoneurone properties was closely related to the degree of motor reinnervation of the muscle.

5. At a given stage of motor reinnervation, the degree of recovery of the motoneurone properties was approximately the same regardless of the presence or absence of functional motor connexions of the motoneurone under study.

6. When the dorsal root ganglia were removed immediately before self‐union of the muscle nerves, recovery of the conduction velocity of motoneurones was impeded without significant effect upon the process of motor reinnervation or upon recovery of the overshoot amplitude and the duration of after‐hyperpolarization.

7. It is concluded that the ‘dedifferentiated’ properties of fast and slow alpha motoneurones after nerve section may be ‘redifferentiated’ following motor reinnervation to any muscle. The possible signal for restoration of the motoneurone properties is discussed.
The secretion of alkali metal ions by the perfused cat pancreas as influenced by the composition and osmolality of the external environment and by inhibitors of metabolism and Na+, K+‐ATPase activity
Authors: Case R. M. , Scratcherd T.
Published: December 2014

1. The secretion of sodium, potassium and lithium has been studied in the isolated cat pancreas, perfused with bicarbonate buffered saline solutions of varying composition and osmolality, and stimulated maximally with secretin.

2. Under isosmolal conditions, when perfusate sodium chloride was replaced by sucrose, sodium secretion and potassium secretion were directly related to perfusate sodium concentration, [Na]p.

3. When osmolality was varied by increasing or decreasing perfusate sodium chloride concentration, the secretion of sodium and of potassium were maximal at [Na]p of about 120 and 80 m
M respectively.

4. At a given [Na]p, sodium secretion was greater under hypo‐osmolal conditions than under isosmolal conditions.

5. When potassium concentration was varied over the range 0–130 m
M under isosmolal conditions, by adjusting perfusate NaCl concentration, the secretion of potassium and of sodium were maximal at [K]p of about 50 and 10 m
M respectively. Water flux was maximal at a [K]p of 10–15 m
M. The concentration of potassium in the secretion was almost identical with that in the perfusate over the whole concentration range.

6. Replacement of perfusate sodium by lithium reduced the volume of secretion, though a small secretion was maintained even in the complete absence of sodium. The concentration of lithium in the secretion was generally slightly greater than that in the perfusate.

7. Omission of potassium from the perfusate reduced secretion by about 65%. Rubidium was a complete substitute for potassium; caesium was not.

8. Energy for secretion is derived largely from oxidative phosphorylation. Secretion was reduced by more than 90% under anaerobic conditions and in the presence of dinitrophenol or cyanide. Removal of glucose from the perfusate reduced secretion by more than 50% within 30 min; lactate was a complete substitute for glucose.

9. Ouabain, ethacrinic acid and frusimide, known inhibitors of Na+, K+‐ATPase activity, all inhibited pancreatic electrolyte secretion.

10. The observations are interpreted with reference to the nature of active transport processes involved in pancreatic electrolyte secretion.
Reconstruction of the electrical responses of turtle cones to flashes and steps of light
Authors: Baylor D. A. , Hodgkin A. L. , Lamb T. D.
Published: December 2014

1. Theoretical equations which predict the electrical response of turtle cones to a wide range of light stimuli are developed from the experiments described in previous papers.

2. The central points in the theory are that (a) light starts a chain of reactions leading to the production of a substance which blocks ionic channels in the outer segment, (b) an equilibrium between blocking molecules and open channels is rapidly established, (c) the blocking molecules are removed or inactivated by a chain of reactions, the first of which is autocatalytic, (d) in addition to the conductance which decreases with light there is also a conductance which increases with a delay when the cone is hyperpolarized.

3. Parameters in the theory were deduced by approximate equations from the experiments described in the previous papers.

4. There was good agreement between the properties of real and model cones in the following cases: (a) the response to 10 msec flashes and 0·7 sec steps of light calculated to give between 20 and 5 × 107 photoisomerizations per cone at times extending to about 2 sec; (b) the complicated changes in the response to a test flash that occur when it is superposed on background lights of increasing intensity; (c) the after‐hyperpolarization and period of reduced sensitivity following a strong flash.

5. The main defect of the theory is that the effect of background light in shortening the time to maximum of the response to a flash was more pronounced in a real cone than in the model.
Thallium and the sodium pump in human red cells
Authors: Cavieres J. D. , Ellory J. C.
Published: December 2014

1. Thallium (Tl) inhibits the ouabain‐sensitive K influx in human red cells in high‐Na medium. At 1 m
M external K concentration [Ko], the ouabain‐sensitive K influx decreases steadily with increasing Tl concentration, up to 0·9 m
M outside; at 0·17 m
M‐Ko, however, Tl stimulates the ouabain‐sensitive K influx below 0·1 m
M‐Tlo and inhibits it at higher concentrations.

2. In a K‐free medium in which all except 5 m
M‐Na is replaced by choline, and into which red cells show zero control ouabain‐sensitive Na efflux, Tl is able to support ouabain‐sensitive Na efflux up to 2·1 m‐mole/l. cells.hr following a sigmoid activation curve which is half‐maximal between 0·03 and 0·05 m
M‐Tlo and that follows two‐site kinetics up to 0·1 m
M‐Tlo. Beyond 0·15 m
M‐Tlo, the Tl‐activated ouabain‐sensitive Na efflux attained is inhibited slightly.

3. When the ouabain‐sensitive Na efflux is measured at 5 m
M‐Nao and 5 m
M‐Ko, increasing concentrations of Tl have little effect on it, 0·9 m
M‐Tlo inhibiting by some 14%; in similar conditions, the ouabain‐sensitive K influx is inhibited by about 40%.

4. The dependence of ouabain‐sensitive K influx on external K concentration at 5 m
M‐Nao, which follows a slightly sigmoid curve in the absence of Tl, changes to hyperbolic at 0·06 m
M‐Tlo at the same time that ouabain‐sensitive K influx is inhibited. The fitted Vmax values for ouabain‐sensitive K influx are the same in the presence and in the absence of 0·06 m
M‐Tlo.

5. In high‐Na cells, loaded by nystatin treatment, the ouabain‐sensitive K influx measured at 0·2 m
M‐Nao follows a hyperbolic curve between 0·05 and 0·4 m
M‐Ko, and is inhibited by Tl in a strictly competitive fashion.

6. The effects of Tl on ouabain‐sensitive Na efflux and ouabain‐sensitive K influx are interpreted in terms of a high‐affinity substitution for K at the external K sites of the Na pump and suggest that in human red cells Tl can be actively transported inwards in exchange for internal Na.

7. Thallium can inhibit about 25% of the ouabain‐insensitive Na efflux into 5 m
M‐Nao and part of this inhibition occurs with a high Tl‐affinity; the ouabain‐insensitive K influx is inhibited by Tl both in high‐Na and in 5 m
M‐Na medium, but with a different concentration dependence than the ouabain‐insensitive Na efflux.
Modification of the postural response of the normal dog by blindfolding
Authors: Talbott Richard E.
Published: December 2014

1. Normal dogs were trained to stand quietly upon a movable platform. The animals' postural adjustments in response to sinusoidal motion of the platform were assessed in both the normal and the blindfolded condition. The induced postural adjustments were described by the Fourier coefficients for the fundamental of the input together with the coefficients which were integral multiples of the fundamental.

2. All of the output variables, including motion at the hind limb joints and of the body, showed modifications when the dogs were blindfolded. The body motion increased in amplitude, as measured by the fundamental Fourier coefficient, and further lagged the input motion. Motion at the knee and phalangeal joints also increased in amplitude and the timing of these movements shifted from the normal in characteristic patterns for different frequencies of input motion.

3. The modifications of the postural response due to blindfolding were most pronounced at the lower input frequencies: 0·2–1·0 Hz. At 1·4 Hz or above the fundamental coefficients of most of the output measures resembled those of the normal condition. Even at the higher input frequencies, however, the postural response of the blindfolded dog was more distorted than that of the normal dog.

4. It is hypothesized that relatively slow movement of the visual surround provides the dog with information which is essential to normal operations of the postural control system.
The effects of raising alveolar PCO2 and ventilation separately and together on the sensitivity and setting of the baroreceptor cardiodepressor reflex in man
Authors: Bristow J. D. , Brown E. B. , Cunningham D. J. C. , Howson M. G. , Lee M. J. R. , Pickering T. G. , Sleight P.
Published: December 2014

1. The effects of changes in ventilation and/or alveolar PCO2 on the baroreflex control of heart rate have been studied in seven experiments on six young men and women who had been trained to control tidal volume and respiratory frequency at various levels independent of alveolar PCO2, during hyperoxia.

2. Intravenous phenylephrine provoked transient rises of directly measured arterial pressure during which individual systolic pressures (P) were linearly related to the following pulse interval (I). Baroreflex sensitivity was expressed as the slope of the regression of I on P, and reflex setting (Iref) as I at a single reference arterial pressure (= mean P for the experiment).

3. Voluntary control of breathing had little effect on heart rate and arterial pressure (baroreflex setting), but diminished reflex sensitivity.

4. Hypercapnia regularly caused tachycardia at the reference pressure (i.e. baroreflex setting lowered). The response was completely or partly reproduced by change of PA, CO2 at constant ventilation in four subjects but not in two others; in them change of ventilation at constant PA, CO2 completely mimicked the effect of free‐breathing hypercapnia.

5. Values of baroreflex sensitivity were relatively scattered. Hypercapnia caused a fall in baroreflex sensitivity in three subjects whether ventilation was fixed or free to rise. After separating the effect of voluntarily controlling ventilation, ventilation per se was without effect on reflex sensitivity.

6. It is concluded that hypercapnia and hyperpnoea have separate effects on the baroreflex, the relative magnitudes of which differ from one subject to another. Baroreflex setting and sensitivity vary independently in response to change of ventilation and of PA, CO2.
Hepatic osmoreceptors?
Authors: Glasby M. A. , Ramsay D. J.
Published: December 2014

1. The effects of 0·45% saline infusions into the portal vein of conscious and anaesthetized dogs have been compared with similar infusions through a systemic vein.

2. Measurements were made of plasma and urinary osmolality, sodium, potassium and chloride concentrations and urine flows; osmolal clearances, free water clearances, the percentage of the infused loads excreted at given times, and rates of sodium and potassium excretion in the urine, were calculated.

3. In the conscious and anaesthetized series of experiments no significant differences were found between the portal and systemic routes of infusion.

4. For both the portal and systemic routes of infusion there was a significantly smaller diuretic response to the saline infusion in anaesthetized as compared with conscious animals.

5. These results do not support the concept of hepatic osmoreceptors occurring in the dog.
The effect of holding potential on the asymmetry currents in squid giant axons
Authors: Meves H.
Published: December 2014

1. Asymmetry currents were recorded from intracellularly perfused squid axons subjected to an equal number of exactly equal positive and negative voltage clamp pulses. The asymmetry currents consisted of an on‐response at the beginning of the pulses and an off‐response at the end of the pulses.

2. The asymmetry currents were markedly reduced by 30 m
M glutaraldehyde applied internally.

3. Clamp pulses of varying height, superimposed on a holding potential of — 80 to — 100 mV, were used to study the voltage and time dependence of the asymmetry current. The magnitude of the on‐ and off‐response increased with increasing pulse height along a sigmoid curve. The time constants of the on‐ and off‐response depended on the potential during the depolarizing pulses; the time constant of the on‐response had a maximum at an internal potential of — 12 mV, the time constant of the off‐response was largest at positive internal potentials.

4. Holding the membrane at a potential of — 80 to — 100 mV for several minutes led to a slow increase of the size of the asymmetry current.

5. Changing the holding potential from — 80 or — 100 mV to a less negative potential caused a decrease of the asymmetry current. At holding potentials less negative than — 65 or — 60 mV the asymmetry current reversed its sign: the transient current at the beginning of the pulses turned into an inward current and the transient current at the end of the pulses became outward. No inactivation of the asymmetry current was seen in the range of holding potentials studied (V < — 3 mV).

6. The results are generally consistent with the idea that the asymmetry currents are in some way related to the opening and closing of the Na gates; they suggest, however, that the asymmetrical charge movement does not simply reflect the voltage and time dependence of the m system.
Two descending nerve pathways activated by distension of guinea‐pig small intestine.
Authors: Hirst G D , Holman M E , McKirdy H C
Published: December 2014

1. Intracellular recordings were made from myenteric neurones of the guinea‐pig small intestine in preparations which had a synaptic input from an orally situated segment of intestine. 2. Excitatory synaptic potentials could be evoked in most neurones by distension of the attached intestinal segment. 3. It was possible to distinguish two distinct firing patterns of synaptic potentials in response to distension. A transient short latency discharge was recorded from some neurones. From the others, a persistent synaptic discharge was recorded only after a long latency (2–11 sec). 4. Distension of intestinal segments evoked short latency transient inhibitory junction potentials in the circular muscle layer followed by excitatory junction potentials in both the circular and longitudinal muscle layers. 5. It is suggested that distension may cause both descending inhibition and, after a delay, descending excitation of the guinea‐pig small intestine.
The electrical basis of excitation and inhibition in the rat anoccygeus muscle.
Authors: Creed K E , Gillespie J S , Muir T C
Published: December 2014

1. The transmembrane potential of smooth muscle cells of the rat anococcygeus muscle was studied with micro‐electrodes. The muscle had a mean resting membrane potential of ‐‐61‐5 mV and normally lacked spontaneous mechanical and electrical activity. 2. Stimulation of intramural nerves with single pulses produced a small depolarization and contraction. At frequencies greater than 0.5 Hz a second component occurred which had a maximum value of 35‐‐51 mV with short trains at 30 Hz. Spike potentials were rarely seen. Depolarization was accompanied by a decrease in membrane resistance. 3. Noradrenaline (3 times 10‐minus 5 M) and guanethidine (3 times 10‐minus 5 M) both depolarized the membrane and produced contraction. Initially, oscillations in the membrane potential were oftern seen. 4. Intramural nerve stimulation in the presence of guanethidine damped the oscillations and produced relaxation. This was accompanied by neither hyperpolarization nor a change in membrane resistance. 5. TEA (1 mM) depolarized the membrane (−‐47‐6 mV) and initiated spontaneous activity. Field stimulation evoked spikes with overshoot.
Renal function in sheep during infusion of alkali metal ions into the renal artery.
Authors: Beal A M , Harrison F A
Published: December 2014

1. The effect on renal function of 1 M solutions of LiCl, NaCl, KCl, RbCl and CsCl and 3 M‐NaCl infused close‐arterially to the kidney for 10 min at 0–7ml./min has been studied in nine experiments on four unilaterally nephrectomized sheep. The levels of flow, electrolyte concentration and electrolyte excretion in the urine were measured before, during and for 50 min after the infusions. 2. The infusion of 1‐M‐NaCl produced little change in urine flow and composition whereas 3 M‐NaCl resulted in relatively small increases in urine flow and sodium excretion. 3. The infusion of lithium, potassium, rubidium and caesium resulted in marked increases in urine flow, urinary sodium concentration and excretion, urinary potassium excretion and osmolal clearance while the urinary potassium concentration decreased. 4. Changes in urine flow and urinary pH during the infusions of all the alkali ions except sodium were consistent with increased urinary bicarbonate excretion. 5. The osmolal clearance was increased by the infusion of lithium, potassium, rubidium and caesium, but equivalent increases in the rate of solutefree water reabsorption did not occur. 6. The infusion of caesium resulted in a depression of the glomerular filtration rate (G.F.R.) which was not observed when the other alkali ions were infused. 7. The effects of lithium, potassium and rubidium on urine flow and composition were rapid in onset and the residual effects on these ions, on cessation of infusion, were relatively short. The effects on caesium were slow in onset and prolonged in duration. 8. It was concluded that lithium, potassium, rubidium, and caesium altered urine flow and electrolyte excretion by acting upon common mechanisms which were predominantly intra‐renal and located in the proximal segment of the nephron.
A quantitative description of tetanic and post‐tetanic potentiation of transmitter release at the frog neuromuscular junction.
Authors: Magleby K L , Zengel J E
Published: December 2014

1. End‐plate potential (e.p.p.s) were recorded with a surface electrode from frog neuromuscular junctions blocked with high Mg and low Ca to study post‐tetanic potentiation (potentiation). 2. The magnitude of potentiation was not directly related to the number of conditioning impulses, but was a function of the frequency and duration of the conditioning stimulation. 3. Potentiation was always greater following an equal number of impulses delivered at a higher frequency of stimulation. 4. Plots of the magnitude of potentiation against the number of conditioning impulses would sometimes show an upward inflexion depending on the parameters of stimulation. 5. These experimental observations were described by a model based on the assumption (1) that potentiation is linearly related to a residual substance, R(t), which accumulates in the nerve terminal during repetitive stimulation, and (2) that each nerve impulse adds an identical increment, r, of this residual substance. The data were not described by assuming a 4th power relationship between potentiation and R(t). 6. The upward inflexion in potentiation (see paragraph 4) is described by the model as resulting from an increase in the time constant for the decay of potentiation as the magnitude of potentiation increases. 7. The increment of residual substance r added by each impulse was independent of the amount of transmitter released during the conditioning train. This increment typically increased transmitter release by amount 1% of the control level in the absence of potentiation. 8. Suggestions are given to explain why potentiation of transmitter release, which is thought to arise from an accumulation of Ca‐2+ in the nerve terminal, can be described assuming a linear relationship between potentiation and R(t), the proposed substance responsible for potentiation, under experimental conditions in which a 3rd to 4th power relationship would be expected to exist between external Ca concentration and evoked transmitter release.
Thyroid control of small intestinal oxygen consumption and the influence of sodium ions, oxyhen tension, glucose and anaesthesia.
Authors: Levin F J , Syme G
Published: December 2014

1. Oxygen consumption of jejunum removed from either killed or anaesthetized euthytoid, hypothyroid and triiodothyronine (T3)‐treated rats was measured polarographically in vitro. 2. Hypothyroidism induced by drinking 6‐n‐propyl‐2‐thiouracil depressed jejunal oxygen consumption. 3. Treatment of euthyroid rats with T3 stimulated jejunal oxygen consumption by 39% in the presence of 28 mM glucose and by 23% in its absence. 4. Sodium ions appear to play a major permissive role in the action of T3 on jejunal oxygen uptake. In the presence of sodium, T3 stimulated significantly the oxygen consumption by 23% while in the absence of sodium the stimulation was only 10% which was not significant. The sodium‐sensitive oxygen uptake of the jejunum was expanded by 57% after T3 treatment.
Acidification in the rat proximal jejunum.
Authors: Blair J A , Lucas M L , Matty A J
Published: December 2014

1. Production of hydrogen ions by the rat proximal jejunum was investigated using the everted sac technique. 2. Acidification occurred in the absence of glucose, increasing on addition of glucose to reach a maximal value. An apparent Km of 1‐78 mM was derived for the glucose‐dependent process. 3. Acidification in the presence of glucose was inhibited by 10 mM‐2:4‐dinitrophenol, 10 mM phlorrhizin, 10 mM aminophylline and anaerobiosis. 4. Histamine, ethylenediamine tetraacetic acid (EDTA), ouabain and acetazolamide, compounds known to alter acid production in gastric mucosa had no effect on jejunal acidification. 5. Galactose and 3‐O‐methylglucose failed to increase acidification; in contrast, mannose and fructose did lead to increases, indicating metabolic origin of the hydrogen ions. 6. Serosal and mucosal lactate production were measured and the calculated percentage of hydrogen ions possibly derived from this source was shown to account for only a small proportion of acidification. 7. The greatest increase in acidification with minimal simultaneous production of lactate occurred with ATP which was shown not to enter intestinal tissues. 8. A hypothesis for acidification, that of the break‐down at the mucosal surface of ATP from intracellular metabolic sources, is proposed and its relevance to the postulated microclimate is discussed.
An electrophysiological and morphological study of normal and denervated chicken latissimus dorsi muscles.
Authors: Cullen M J , Harris J B , Marshall M W , Ward M R
Published: December 2014

1. Some electrophysiological and morphological properties of ‘fast’ (singly innervated) and ‘slow’ (multiply innervated) muscle fibres were studied in normal and denervated posterior and anterior latissimus dorsi muscles of the young chickens. 2. Normal singly and multiply innervated muscle fibres are capable of generating action potentials which in all qualitative respects are similar. 3. The action potentials of multiply innervated muscle fibres are of lower amplitude and slower maximum rate of rise than action potentials in singly innervated muscle fibres. 4. Denervation causes the resting membrane potential and the maximum rate of rise of the action potential to fall. The changes are greater in singly innervated than in multiply innervated fibres, but in neither case are as great as in mammalian skeletal muscle fibres after surgical denervation. 5. In neither singly nor multiply innervated muscle fibres do the action potentials generate any ‘resistance’ to tetrodotoxin as a result of denervation. 6. The diameter of multiply innervated fibres is increased after denervation, but it is reduced in singly innervated fibres. The number of myofilaments increases in multiply innervated fibres, but decreases in single innervated fibres. In both types of muscle fibre the volume fraction of myofibrils is decreased. 7. In the singly innervated muscle fibres there is an increase in the volume fraction of mitochondria. 8. In the singly innervated muscle fibres, there is some rearrangement of the membrane systems in that some of the transversely orientated triads are replaced by longitudinally orientated dyads.
Duodenal control of gastric emptying in the milk‐fed calf.
Authors: Bell F R , Mostaghni K
Published: December 2014

1. It has been ascertained experimentally that an open duodenal cannula does not cause any marked variation in emptying of the abomasum when compared to the rate of emptying of the normal viscus or when the cannulae are closed. 2. Duodenal re‐entrant cannulae provide a preparation whereby it is possible to infuse the duodenum via the distal cannula and to collect simultaneously the effluent fluid of the abomasum from the proximal arm of the cannula (Fig. 1). 3. With this preparation the duodenal infusate is not contaminated by the gastric effluent and thus the duodenal stimulus can be restricted to the single non‐varying effect of the infusate. 4. In the milk‐fed calf using this preparation the following facts have been established. (a) On infusion into the duodenum, hypotonic and isotonic solutions of sodium chloride and sodium bicarbonate increase abomasal emptying; bicarbonate being the more effective stimulus. (b) Potassium chloride, calcium chloride, glucose and hydrochloric acid inhibit gastric emptying when infused into the duodenum. (c) Ammonium chloride, urea, lactose and acetic acid have little effect. (d) Hypertonic solutions of all substances tested were inhibitory to gastric emptying when infused into the duodenum. 5. It has been demonstrated unequivocally that it is the effect of the infusate in the duodenum which controls gastric emptying for when the stomach is isolated from the duodenum, gastric emptying can be manipulated from the duodenum whatever the stomach contents may be. 6. Our results bring firm experimental confirmation of the views discussed by Hunt & Knox (1968) that gastric outflow is regulated by mechanisms initiated from receptors situated in the duodenum.
An analysis of the release of acetylcholine from preganglionic nerve terminals.
Authors: MacLachlan E M
Published: December 2014

1. A study has been made of the release of acetylcholine (ACh) from the preganglionic nerve terminals of the isolated superior cervical ganglion of the guinea‐pig during short trains of impulses, using the amplitude of the excitatory post‐synaptic potential (e.p.s.p.) as a measure of the ACh released by each impulse. 2. The time course of decay of facilitation following a single impulse could be described by two exponential components, with T1 = 200 msec, and T2 = 13–3 sec. The increase in ACh output at the beginning of stimulation at frequencies smaller than or equal to 2Hz was reasonably predicted in terms of summation of the individual facilitatory effects of each impulse in the train, but fell short of the prediction at higher frequencies. 3. The steady‐state output of ACh during repetitive stimulation at frequencies between 0–5 and 20 Hz was lower than that predicted by summation of the facilitatory effects of each impulse, but reached the predicted level at frequencies smaller than or equal to 2Hz in raised Mg2+ concentrations. 4. Statistical analysis of the quantal content (m) of e.p.s.p.s evoked by each of the first five impulses in a train showed that Poisson statistics described release of ACh at the beginning of a train in most cases; when binomial statistics could be applied (two of seven axons studied), the increase in m was accompanied by an increase in the statistical parameter, n. 5. Analyses were also made of release during continuous stimulation; at the time when the steady state of release was reached, the statistical parameter, p, had also increased. Increased release of ACh at increased frequencies of stimulation was associated with increases in p in axons with p smaller than 0–5; however, in most axons (eleven of seventeen), p was greater than 0–5 in the steady state, and increases in m with frequency were due to increases in n.
Studies on convulsants in the isolated frog spinal cord. I. Antagonism of amino acid responses.
Authors: Barker J L , Nicoll R A , Padjen A
Published: December 2014

1. The isolated frog spinal cord was used to study the effects of picrotoxin, bicuculline, and strychnine on the responses of primary afferents to amino acids. Recording was by sucrose gap technique. 2. A series of neutral amino acids was found to depolarize primary afferents. Optimal activity was obtained by an amino acid whose carboxyl and amino groups were separated by a three‐carbon chain length (i.e. GABA). Amino acids with shorter (i.e. beta‐alanine, glycine) or longer (i.e. delta‐aminovaleric acid, epsilon‐aminocaproic acid) distances between the charged groups were less potent. Imidazoleacetic acid was the most potent depolarizing agent tested. 3. Picrotoxin and bicuculline antagonized the primary afferent depolarizations of a number of amino acids tested with equal specificity. Depolarizing responses to standard (10‐ minus 3 M) concentrations of beta‐alanine and taurine were completely blocked by these convulsants, while depolarizations to 10‐ minus 3 gamma‐aminobutyric acid (GABA) were only partially antagonized. Glycine responses were unaffected by these agentsk; Strychnine completely blocked beta‐alanine and taurine depolarizations and incompletely antagonized several other neutral amino acids. GABA, glutamate, and glycine depolarizations were not affected. 5. These results suggest that there are at least three distinct populations of neutral amino acid receptors on primary afferent terminals: a GABA‐like receptor, a taurine/beta‐alanine receptor, and a glycine‐like receptor. The strychnine resistance of the glycine responses indictaes that the primary afferent receptors for glycine differ from those on the somata of spinal neurones.
The sensitivity of adrenal responses to synthetic adrenocorticotrophin in the conscious unrestrained calf.
Authors: Edwards A V , Hardy R N , Malinowska K W
Published: December 2014

1. Changes in cortisol and corticosterone output and blood flow from the adrenal gland have been determined in the conscious unrestrained calf during I.V. infusions of synthetic adrenocorticotrophin (Synacthen) at 0–5 ng‐kg(∓1) min‐ minus 1 (low dose), 5 ng‐kg‐ minus 1 (medium dose), 50 ng‐kg‐ minus 1 min‐ minus 1 (high dose) and 500 ng‐kg‐ minus 1 min‐ minus 1 (medium dose), 50 ng‐kg‐ minus 1 min‐ minus 1 (high dose) and 500 ng‐kg‐ minus 1 min‐ minus 1(very high dose). 2. Infusions at the low dose produced a rise in adrenal output of both cortisol and corticosterone to maximum values of approximately 100 and 30 ng‐kg‐ minus 1 min‐ minus 1 respectively. Mean output of both steroids was significantly increased within 5 min, reached a maximum within 10 min and had fallen to resting levels 10 min after the infusion was discontinued. 3. The effects of infusions at both the high and very high doses were closely similar; maximal cortisol outputs were within the range 600–800 ng‐kg‐ minus 1 min‐ minus 1 and corticosterone 350–500 ng‐kg‐ minus 1 min‐ minus 1 in both groups. 4. When the infusions were terminated, pronounced differences were observed in the rates at which steroid outputs declined. Basal levels were restored within 10 min following the low dose and within 60 min in medium dose animals, but both cortisol and corticosterone output were still elevated 2 hr after infusion in high dose animals. In calves infused at the very high dose, cortisol output did not fall significantly during 2 hr period. The ratio of cortisol: corticosterone released from the adrenal gland immediately before infusion (3–2 +/− 0–3) approximated to the proportions in which the two steroids were found in the arterial plasma, but fell progressively to a minimum (1–3 +/− 0–1) with increasing doses of Synacthen. Conversely, the ratio of the steroids in the arterial plasma was increased during infusions at the low dose, but not at the higher doses. 6. No significant change in adrenal blood flow occurred during Synacthen infusion in low dose animals despite the increase in steroid output. In medium dose animals blood flow through the gland rose during infusion by approximately 75 per cent while in both high and very high dose animals the flow increased by up to 300 percent. 7. In the three groups in which adrenal hyperaemia occurred, blood flow had fallen to within the resting range 45 min after infusion: in each case this fall was much more rapid than the fall in steroid output. No significant increase in aortic blood pressure or heart rate accompanied infusion of Synacthen, indicating that adrenal hyperaemia was dependent upon vasodilatation with the gland. 8. Administration of cycloheximide (10 mg/kg) by I.V. injection either before or during an infusion of Synacthen, inhibited steroidogenesis without affecting the vasodilator response.
Responses of fastigial nucleus neurones to stimulation of the caudate nucleus in the cat.
Authors: Gresty M A , Paul D H
Published: December 2014

1. Extracellular records were made of single unit activity evoked in the fastigial nucleus (FN) by electrical stimulation of the caudate nucleus (CN) in cats anaesthetized with sodium thiopentone. 2. Single shock stimulation evoked bilaterally complex responses having up to three components. These were, in temporal order, with percent of units exhibiting them, (a) a short burst of evoked spikes with either a latency of smaller than 5‐5 msec and no associated field potential (6 percent) or a latency of 7–5–20 msec and associated with a prominent negative‐going field potential (36 percent); (b) suppression of spontaneous discharges for a period of 20–150 msec (90 percent); (c) a resumption of spike discharges with a transient increase in frequency lasting for 25–500 msec (66 percent). 3. Changes in component (c) of the response patterns of some units were noted during repetitive stimulation The nature of the change depended on the laterality of the FN with respect to the stimulated CN. 4. Mechanisms which might account for the responses are discussed, but it is emphasized that some of the results cannot yet be satisfactorily explained.
Periodic excitability changes across the receptive fields of complex cells in the striate and parastriate cortex of the cat.
Authors: Pollen D A , Ronner S F
Published: December 2014

1. Complex cells in cortical areas 17 and 18 of the cat have been studied in response to narrow slits and edges moving across the receptive field in the preferred direction and also to stationary slits of different widths. 2. Average response histograms, recorded as a narrow slit was moved across the receptive field, displayed a periodic series of peaks above a base line level. The response histogram for most area 17 and 18 cells contained five principal peaks; sometimes one or two weaker peaks were present at receptive field borders. The histogram for one cell located at the area 17–18 border showed thirteen distinct peaks. Periodic response patterns were also generated as an extended edge was moved across the receptive field. Plots of cell responses versus slit width for stationary slits of different widths also indicated periodic response pattern. 3. The accuracy of determining the preferred slit orientation was the single most important requirement for demonstrating the periodic response pattern. Significant changes in the appearance of the periodic pattern occurred even upon 5 degrees rotations away from the preferred orientation. 4. Average response histograms were also studied over a wide range of moving slit velocities. The number of peaks across corresponding spacings within the recewptive field remained constant over a range of velocities. Response amplitudes, however, were velocity dependent. Thus the response peaks remain associated with fixed positions within visual space independent of stimulus velocity, even though temporal as well as spatial factors may be involved in response selectivity and the periodic modulation. The most striking periodic response histograms were generated at the velocities which produced the greatest cell firing rates. Area 17 complex cells responded well to velocities of less than 0–5 degrees to 6–0 degrees/sec, but cells in area 18 generally required higher velocities, sometimes as high as 20 degrees‐‐30 degrees/sec, for a good response. 5. Spatial frequencies for the periodic component of the receptive field for area 17 cells in the central visual area covered a range of three octaves up to 5 cycles/degree, and area 18 cells included another octave on the low frequency side. The spatial frequency of a cell was found to be roughly inversely proportional to the receptive field width. Only a small sample of area 18 cells was studied, but these cells tended to represent low spatial frequencies and to respond selectively to high velocity stimuli...
Baroreceptor and chemoreceptor influences on heart rate during the respiratory cycle in the dog.
Authors: Haymet B T , McCloskey D I
Published: December 2014

1. Brief stimuli were delivered to the carotid chemoreceptors or baroreceptors in dogs anaesthetized with pentobarbitone or chloralose. Chemoreceptor stimulation was achieved by rapid retrograde injections of 0‐2‐0‐5 ml. warmed, CO2‐equilibrated saline through a cannula in the external carotid artery. Baroreceptor stimulation was achieved by forceful retrograde injection of 2–5 ml. air‐equilibrated saline, or of freshly drawn arterial blood, into the external carotid artery after first clamping the common carotid artery. 2. Brief baroreceptor stimuli had no noticeable effect on breathing. Brief chemoreceptor stimuli had no effect on breathing in some dogs, but in many produced a reflex increase in the depth of inspiration when delivered during inspiration. In these same dogs, brief chemoreceptor stimuli delivered in expiration either prolonged the expiratory pause or evoked an active expiratory effort. 3. Prompt decreases in heart rate were elicited by brief sudden chemoreceptor or baroreceptor stimuli when these were delivered during the expiratory phase of respiration. The stimuli did not modify the control heart rate pattern when delivered during inspiration. If the carotid sinus nerve or the vagus nerves were cut the responses were abolished. 4. Brief chemoreceptor or baroreceptor stimuli remained effective in evoking prompt decreases in heart rate during periods of apnoea in the end‐inspiratory position (Hering‐Breuer inflation reflex). In periods of apnoea after prolonged artificial hyperventilation the stimuli were sometimes ineffective at first, but were always effective late in the period of apnoea, again producing prompt cardiac slowing. 5. After denervation of the lungs, brief baroreceptor and chemoreceptor stimuli continued to evoke prompt falls in heart rate when given during expiration. When delivered during inspiration the same stimuli were either ineffective, or less effective.
Receptive field organization of ganglion cells in the frog retina: contributions from cones, green rods and red rods.
Authors: Bäckström A C , Reuter T
Published: December 2014

1. The impulse discharge of ganglion cells was recorded with extracellular micro‐electrodes in the excised and opened eye of the common frog, Rana temporaria. 2. When a single unit was isolated, the cell type was first determined according to the Maturana, Lettvin, McCulloch & Pitts (1960) classification with the aid of varying moving and stationary stimuli. 3. Class 4 cells respond only to a decrease of light when cones are stimulated but respond to an increase of light when green rods are stimulated. A distinct class of deviating class 4 cells was found that give a brief high frequency burst at ‘off’ from their small excitatory receptive fields (ERF); unlike typical class 4 cells they possess a purely inhibitory surrounding field (IRF).4. The contributions from the cones and the green and red rods were isolated by measuring the thresholds of the discharges with on‐off stimuli of varying wave‐lengths against strong yellow backgrounds, or against a very weak background or no background at all. The spatial distribution of the contributions to the ERF was determined by mapping threshold profiles, and additional information about ERF and IRF was obtained from area‐threshold curves. 5. The cone‐mediated ERFs were found to be 0‐06‐0‐50 mm wide (1‐5‐12 degrees of visual field), which agrees well with the sizes of the dendritic trees of the ganglion cells. The green rod‐mediated ERFs can be 0‐5‐1‐5 mm wide and have less distinct boundaries than the cone‐mediated. The green rod‐mediated ERF of an individual ganglion cell is always larger than the cone‐mediated ERF of the same cell. The red rod‐mediated ERFs seem to be somewhat larger than the cone‐mediated but smaller than the green rod‐mediated. 6. The green rods contribute only to the on thresholds of class 1, 2 and 4 cells, but both to on and off in typical class 3 cells, while the cones contribute to on and off in classes 1–3 and only to off in class 4.7. When the red rods begin to contribute during dark adaptation they seem to enter the cone but not the green rod channels. 8. All three receptor types contribute to the IRF surrounding the ERF of classes 1, 2, 3 and deviating class 4 cells. Normal class 4 cells have no IRF. 9. The organization of the receptive fields is discussed in relation to the anatomy and electrophysiology of the cell types transmitting the signals from the receptors to the ganglion cells.
Comparison of the hyperglycaemic effect of adrenaline and morphine introduced into the liquor space.
Authors: Dey P K , Feldberg W , Wendlandt S
Published: December 2014

1. In unanaesthetized cats a comparison is made of the hyperglycaemic effects of adrenaline and morphine, when injected or infused through chronically implanted cannulae, into different regions of the cerebral ventricles or of the subarachnoid space, in order to determine their sites of action. 2. On injection into the cerebral ventricles both adrenaline and morphine have to reach the subarachnoid space beneath the ventral surface of the brain stem before they can exert their hyperglycaemic effect. The adrenaline has to reach the region rostral to the pons, i.e. the fossa interpeduncularis, and the morphine the region caudal to the trapezoid bodies. These conclusions are based on the following findings. 3. When adrenaline (55 mug) and morphine (0–75mg) were infused into one or other of these two regions, adrenaline produced strong hyperglycaemia on infusion into the fossa interpeduncularis, but had scarcely any hyperglycaemic effect on infusion into the region caudal to the trapezoid bodies. The reverse result was obtained with morphine. 4. It is concluded that the adrenaline hyperglycaemia is mainly a peripheral effect. It occurs after the adrenaline has been absorbed into the blood stream from the fossa interpeduncularis but an additional central component, an action on brain stem structures reached from the fossa interpeduncularis, cannot be excluded. The morphine hyperglycaemia is a central effect due to an action on superficial structures of the ventral surface of the medulla oblongata, caudal to the trapezoid bodies.
Mechanical deactivation induced by active shortening in isolated muscle fibres of the frog.
Authors: Edman K A
Published: December 2014

1. The effect of active shortening on the time course and magnitude of isometric tension development during a single twitch and during an incompletely fused tetanus was studied at 0‐2‐1‐2 degres C in isolated semitendinosus muscle fibres of the frog. 2. Active shortening caused a depression of the contractile force without markedly affecting the total duration of the twitch. The depressant effect increased with increasing amounts of sarcomere shortening. Sarcomere shortenings of 0–05 mum and 0–3 mum reduced the twitch force by approximately 5 and 20 percent of the maximal tetanic tension, respectively. 3. A given sarcomere shortening induced the same absolute amount of depression of the contractile strength when the movement was carried out at different times during the initial 200–250 msec after the stimulus. 4. The influence of load and velocity of shortening during the movement phase was studied. Differences in load ranging between zero and 1/3 of the maximal tetanic tension (with concomitant changes in speed of shortening from Vmax to approximately 1/5 of Vmax) did not affect the degree of depression markedly. Underthe conditions studied, the extent of movement appeared to be the only significant determinant of the depressant effect. 5. The reduction in force induced by active shortening persisted for 800–900 msec during an incompletely fused tetanus. 6. It is suggested that the depressant effect is based on a structural change in the myofilament system that is produced as the A and I filaments slide along each other during muscle activity.
Preservation of early discharge of muscle afferents in acrylamide neuropathy.
Authors: Sumner A J
Published: December 2014

1. Responses to stretch and the ‘early discharge’ have been studied in acrylamide neuropathy in the expectation that functional block of the nerve terminals would allow these two processes to be dissociated. 2. Of 538 single group I and group II muscle afferents which were nonresponsive to stretch, ninety‐nine displayed ‘early discharge’ which appeared to be identical with that described in normally functioning muscle stretch afferents. 3. Preservation of ‘early discharge’ in non‐responsive fibres indicates these impulses do not arise from excitation of the muscle spindle itself. The evidence indicates that ‘early discharge’ is usually ephaptically excited by the muscle action potential.
Response of primate cones to sinusoidally flickering homochromatic stimuli.
Authors: Baron W S , Boynton R M
Published: December 2014

1. The response of the primate cone photoreceptors to sinusoidally flickering stimuli has been obtained by monitoring the late receptor potential (LRP). 2. By comparing the response characteristics of the foveal local electroretinogram (LERG) before and after the intraocular infusion of sodium aspartate, it was found that the b‐wave in the foveal LERG does not affect the monitoring of the LRP to steady‐state flicker. 3. Functions describing the supra‐threshold frequency response characteristics of the photoreceptors were obtained. 4. Linearity was found to hold for low amplitude responses, and temporal modulation transfer functions (MTFs) were obtained for the photoreceptors at various adaptation levels. 5. The cone photoreceptors were found to act approximately as passive low pass filters compounded with some low frequency attenuation. 6. The high frequency response of the photoreceptors at various adaptation levels tends toward a common high frequency asymptote, much like human psychophysical findings, and can be described by a diffusion model. 7. Non‐linearities (convexity‐upwards) suggest modest positive feedback at the level of the photoreceptors. 8. Mechanisms limiting the magnitude of the receptor response at low frequencies have little effect on the phase lag of the response.