bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationships between motor nerve conduction velocities and motor unit contraction characteristics in a slow twitch muscle of the cat
Authors: Bagust J.
Published: December 2014

1. Isometric contractions of cat soleus muscles and of functionally isolated motor units have been measured under conditions similar to those of Bagust, Knott, Lewis, Luck & Westerman (1973).

2. The muscle lengths at which motor unit twitch and tetanus tensions were maximal were close to the optimal lengths of the parent muscles.

3. Motor unit contraction times and tensions were shown to be related to the conduction velocities of the nerve axons supplying them. These relationships were obscured when a number of small samples from several experiments were grouped together.

4. The ratios of the twitch to the tetanic tensions of the motor units were directly related to their times to peak tension.
Different properties of synapses between a single sensory neurone and two different motor cells in the leech C.N.S
Authors: Muller K. J. , Nicholls J. G.
Published: December 2014

In leech ganglia, an individual sensory cell that responds specifically to noxious mechanical stimulation of the skin (N cell) excites two different motoneurones. One raises the annuli of the skin into ridges (the AE cell), while the other innervates logitudinal muscles and thereby shortens the body segment (L cell). A comparison has been made of the way in which these two synapses behave when their common presynaptic cell is stimulated in various conditions.

1. Using previously described criteria, N sensory cells have been shown to make monosynaptic chemical connexions with both the AE and L motoneurones (Nicholls & Purves, 1972). Following a single stimulus, the excitatory synaptic potential recorded in the AE motoneurone was only about one tenth the size of that in the L cell (approximately 0·5 mV compared to 5 mV). Trains of impulses in the same N sensory cell gave rise to synaptic potentials in the AE and the L motoneurones that underwent phases of facilitation and depression; the facilitation, however, was characteristically greater and longer lasting at synapses upon the AE motoneurone.

2. The differences between the two synapses were accentuated in Ringer fluid containing increased concentrations of Ca and also in the cold. Under both of these conditions repetitive firing by the N sensory cell could give rise to synaptic potentials in the AE motoneurone which progressively increased in amplitude, while those in the L motoneurone became smaller.

3. The results suggest that the differences in synaptic transmission can be accounted for by variations in the amount of transmitter released at the presynaptic N cell terminals, rather than by differences in the post‐synaptic cells. The animal's behaviour corresponds to expectations from the physiology of the synapses.
Vestibulo‐ocular and optokinetic reactions to rotation and their interaction in the rabbit
Authors: Baarsma E. A. , Collewijn H.
Published: December 2014

1. Compensatory eye movements due to sinusoidal yaw movements on a torsion swing were measured in alert rabbits. A range of combinations of frequencies (0·048–1·8 Hz) and amplitudes (1–25°) were used. Gain (cumulative slow phase eye movement amplitude/swing amplitude) and phase (eye position vs. swing position — 180°) were calculated from averaged records.

2. Eyes were either closed (canal‐ocular reactions only), open in earth‐fixed visual surroundings (natural interaction of vestibular and optokinetic reactions), or looking at platform‐fixed surroundings, which rotated with the animal (conflict situation). In some rabbits, the same stimulus programme was applied a month after bilateral destruction of the labyrinths (optokinetic reactions only).

3. For canal‐ocular reactions, no true threshold was found. Yet the system showed a small but systematic non‐linearity which is tentatively explained by an acceleration‐dependence of gain. For the higher frequencies (0·40–1·8 Hz) used, gain was 0·55–0·75, with a decrease at the lower frequencies, down to 0·16–0·33 at 0·048 Hz. The response showed a phase‐lead of about 45° at 0·048 Hz and was nearly in phase at 1–1·8 Hz. The long time constant of the cupula‐endolymph system was estimated at about 3·3 sec.

4. With earth‐fixed visual surroundings a temperature‐independent gain (range 0·55–0·82) with negligible phase error was found for the entire stimulus range tested. This natural combination of canal‐ocular and optokinetic systems appears to function very efficiently, with mutual correction of the defects of the systems apart.

5. With platform‐fixed visual surroundings the canal‐ocular system was severely inhibited and its non‐linearities were markedly enhanced by the optokinetic system, especially when the torsion swing moved slowly.

6. The general shape of input—output relations of optokinetic reactions after labyrinthectomy were similar to those found earlier in normal animals, but gain was subnormal for the entire stimulus range tested.
Centre and surround influences on the proximal negative response of the pigeon retina
Authors: Brooks Barbara , Holden A. L.
Published: December 2014

1. Extracellular field potentials were recorded with micro‐electrodes in the inner plexiform layer of the pigeon retina. Stimulus patterns were projected on a tangent screen.

2. Maximal responses to a 1° spot were produced from a receptive area 2–3° in extent. Annuli centred over this area produced a different response wave form.

3. The responses to centred spots and annuli presented synchronously do not superpose: they interact in a way suggesting transient mutual antagonism. The response to spot onset and offset can be suppressed either by annulus onset or by annulus offset.

4. A steady annulus has little effect on the response to spot stimuli, but a steady centred spot enhances the response to annular stimulation.

5. The results suggest that the PNR results from convergence of on‐centre and off‐centre pathways, which are embedded in a widespread suppressive surround.
Physiological and morphological identification of hypothalamic magnocellular neuroendocrine cells in goldfish preoptic nucleus*
Authors: Hayward James N.
Published: December 2014

1. Intracellular recordings were made from antidromically identified neurones in the goldfish preoptic nucleus and Procion Yellow was ejected from the recording pipette, marking these magnocellular neuroendocrine cells diffusely, for histological identification.

2. In confirmation of earlier studies these preoptic neuroendocrine cells showed resting membrane potentials of 47 mV, action potentials up to 85 mV, action potentials of long duration (3·9 msec) occurring in two steps, long‐lasting hyperpolarizing after‐potentials and orthodromic driving from olfactory input.

3. Magnocellular neuroendocrine cells exhibited all‐or‐none jumps to shorter antidromic latencies as pituitary stimulus strength increased, suggesting multiple branching of the ‘axones’ either near the preoptic nucleus or within the neural lobe.

4. I find three morphological types of neuroendocrine cells throughout the magnocellular part of the preoptic nucleus. Cell Type I is a large (37 μm), multipolar neurone, 48 μm from the ependyma, with fine ‘dendrites’ projecting into the lateral hypothalamus and within the preoptic nucleus, with multiple branched ‘axones’. Cell Type II is a large (31 μm), multipolar neurone, 24 μm from the ependyma, with a coarse ‘dendrite’ to the ependyma and fine ‘dendrites’ within the preoptic nucleus, with limited ‘axonal’ branching. Cell Type III is a small (18 μm), multipolar neurone, 46 μm from the ependyma, with fine ‘dendritic’ processes distributed within the preoptic nucleus, with limited ‘axonal’ branching.

5. I conclude that magnocellular neuroendocrine cells show electrical membrane properties of other central neurones with both physiological and morphological evidence for multiple ‘axonal’ branching. The three identifiable neuroendocrine cell types (I, II, III) are distributed widely within the anatomical limits of the preoptic nucleus, pars magnocellularis, with each type receiving ‘specific’ input connexions and with unique output pathways. I suggest that these three types of neuroendocrine cells may be related to the ‘cellular’ secretion of ‘specific’ neurohypophysial hormones and neurophysins.
Reflex control of discharge in motor fibres to the larynx
Authors: Głogowska Maria , Stransky A. , Widdicombe J. G.
Published: December 2014

1. Action potentials have been recorded from single laryngeal motor fibres, with expiratory or inspiratory phases, in cats anaesthetized with pentobarbitone and breathing through a tracheal cannula.

2. Pneumothorax increased the discharge of both inspiratory and expiratory units, the inspiratory response being greatly reduced by bilateral vagotomy below the origin of the recurrent laryngeal nerves.

3. Addition of a ‘viscous’ resistance to breathing, or asphyxial rebreathing through an added dead space, increased the activity of inspiratory units and decreased that of expiratory units.

4. Induction of pulmonary oedema decreased the discharge of inspiratory units and increased that of expiratory units. After vagotomy the response of inspiratory units was reversed.

5. Intravenous injections of potassium cyanide increased the activity of both types of unit.

6. Chemical irritation of the laryngeal mucosa decreased the discharge of inspiratory units and increased that of expiratory units, whether the vagi were intact or cut.

7. It is concluded that expiratory unit discharge can be correlated with expiratory laryngeal resistance, but that inspiratory unit discharge does not correlate so well with inspiratory laryngeal resistance.

8. The relationship between laryngeal motor‐fibre activity and the contractions of the inspiratory and expiratory muscles of breathing is discussed.
The forces generated at the human elbow joint in response to imposed sinusoidal movements of the forearm
Authors: Joyce G. C. , Rack Peter M. H. , Ross H. F.
Published: December 2014

1. The mechanical resistance of the human forearm has been measured during imposed sinusoidal flexion‐extension movements of the elbow joint.

2. The force required to move the limb can be divided into components required to move the mass, and components required to overcome the resistance offered by elastic and frictional properties of the muscles and other soft tissues.

3. When during a vigorous flexing effort the limb was subjected to a small amplitude sinusoidal movement each extension was followed by a considerable reflex contraction of the flexor muscles. At low frequencies of movement this reflex provided an added resistance to extension, but at 8–12 Hz the delay in the reflex pathway was such that the reflex response to extension occurred after the extension phase of the movement was over and during the subsequent flexion movement. The reflex activity then assisted the movement whereas at other frequencies it impeded it.

4. The reflex response to movement increased as the subject exerted a greater flexing force.

5. Small movements generated a relatively larger reflex response than big ones.

6. Even with large amplitudes of movement when the reflex activity was relatively small, the limb resisted extension with a high level of stiffness; this was comparable with the short range stiffness of muscles in experimental animals.

7. The fact that at some frequencies the reflex response assisted the movement implies that with appropriate loading the limb could undergo a self‐sustaining oscillation at those frequencies.
The effect of firing rate on preoptic neuronal thermosensitivity
Authors: Boulant J. A.
Published: December 2014

1. In anaesthetized rabbits, preoptic single units were recorded having positive or negative thermal coefficients (impulses/sec. ° C) for changes in preoptic temperature.

2. A population of forty‐two positive coefficient units was divided into four groups based on their level of firing rate at 38° C. In each group, the average thermoresponse curve was determined by averaging the firing rates of the units at 1° C intervals over the 33–43° C range of preoptic temperatures.

3. A population of twenty‐six negative coefficient units was divided into three groups based on their firing rates at 38° C. Similar average thermoresponse curves were determined for each group.

4. As the level of firing rate increased in the positive coefficient units, the preoptic thermosensitivity progressively decreased at temperatures above 39° C, but generally increased at temperatures below 39° C.

5. In the negative coefficient units, preoptic thermosensitivity generally increased (especially above 39° C) as the firing rate at 38° C increased.

6. The results indicate that in positive coefficient units the level of firing rate determines the temperature range in which units are most thermosensitive. This range reflects whether a neurone is more likely to function in heat‐loss or heat‐production responses.

7. Since peripheral thermal input affects the level of firing rate of positive coefficient units, a neuronal model is suggested to explain the role of peripheral and central thermal signals in temperature regulation.
Excitability changes in crayfish motor neurone terminals
Authors: Zucker Robert S.
Published: December 2014

1. Changes in the post‐activation excitability of crayfish motor nerve terminals were used to measure afterpotentials that might be related to facilitation of transmitter release.

2. The refractory period is followed by a period of supernormal excitability in which the threshold of nerve terminals drops to about 70% of its pre‐activation level at about 15 msec following an impulse. The threshold returns exponentially to its pre‐activation level with a time constant of about 25 msec at 13° C. Such a supernormal excitability is rarely seen in pre‐terminal nerve branches or in the main axon.

3. Following a brief high‐frequency tetanus the peak of the supernormal excitability is greater than that following a single impulse. At low temperature this peak is reduced and delayed, and the decay rate of the supernormal excitability is prolonged with a Q10 of about 2·5.

4. Depolarization of nerve terminals decreases, and hyperpolarization increases, the magnitude of the post‐activation supernormal excitability.

5. The magnitude of the supernormal excitability depends on the external potassium concentration, but not on sodium. In low calcium the peak supernormal excitability is often reduced. High calcium concentration and manganese ions have no effect, but cobalt abolishes the supernormal excitability, and its effects are only slightly reversible. Both cobalt and manganese reversibly block neuromuscular transmission.

6. Strophanthidin has no effect on the post‐activation supernormal excitability, but proteolytic enzymes reduce or abolish it, and hyperosmotic solutions also affect it.

7. It is suggested that the action potential is followed by a depolarizing afterpotential in nerve terminals which is caused by a transient increase in the potassium concentration around the terminals. There is no evidence that afterpotentials in nerve terminals are related to facilitation in any way.
Physiological characteristics of re‐innervation of skeletal muscle in the mouse
Authors: Tonge D. A.
Published: December 2014

1. Re‐innervation of soleus was studied in the mouse after either crushing the sciatic nerve or re‐implanting the nerve to soleus outside the original end‐plate region.

2. During the early stages of re‐innervation subthreshold end‐plate potentials (e.p.p.s) were recorded in muscle fibres in response to nerve stimulation. Later the e.p.p.s became large enough to evoke action potentials in muscle fibres.

3. The rate of recovery of the release of acetylcholine (ACh) as estimated from the quantal content of e.p.p.s was faster when nerves re‐innervated the old end‐plate region after nerve crush than after re‐implantation so that new neuromuscular junctions were formed.

4. During re‐innervation soleus fatigued more rapidly than normal during repetitive nerve stimulation. The fatigue was due to failure of neuromuscular transmission associated with an impaired release of ACh.

5. During re‐innervation soleus was supersensitive to ACh until nerve stimulation was capable of evoking action potentials in muscle fibres.
Is spatial adaptation an after‐effect of prolonged inhibition?
Authors: Dealy R. S. , Tolhurst D. J.
Published: December 2014

1. The elevation of the thresholds for sinusoidal gratings of 4 c/deg and 6·7 c/deg was examined after adapting to gratings of 4 c/deg. Threshold elevation was determined as a function of the adapting contrast.

2. It was confirmed that, when the adapting and testing spatial‐frequencies were the same, the threshold elevation curve extrapolated to zero elevation at an adapting contrast equal to the pre‐adaptation threshold for the adapting grating.

3. It was found that the threshold elevation curve for 6·7 c/deg gratings also extrapolated to zero elevation at the pre‐adaptation threshold for the adapting grating, even though the testing and adapting frequencies were different.

4. It is argued that the latter result shows that adaptation is not simply an after‐effect of prolonged excitation of a channel. Threshold elevation curves may represent the bandwidths of inhibitory interactions between channels.
The effects of physostigmine on synaptic transmission in the inferior mesenteric ganglion of guinea‐pigs
Authors: Bornstein J. C.
Published: December 2014

1. Synaptic potentials were recorded with intracellular electrodes from cells in the inferior mesenteric ganglion of the guinea‐pig.

2. Half‐widths of the synaptic potentials recorded fell into two groups: type L cells had long synaptic potentials (11·6–15·2 msec) and low thresholds (14·6 mV mean), type S cells had short synaptic potentials (6·1–9·3 msec) and high thresholds (29·9 mV mean).

3. Physostigmine (1·2 × 10−6
M) caused a significant increase in the half‐width of both types of synaptic potential.

4. Physostigmine caused a significant increase in the half‐width of spontaneous synaptic potentials and an increase in their amplitude.

5. Repetitive preganglionic stimulation, in the presence of physostigmine, led to a marked and prolonged depolarization in all cells. In most cells repetitive spontaneous firing of action potentials was then observed. This effect was blocked by atropine (1·4 × 10−7
M).

6. The effect of atropine on the half‐width in a physostigmine‐treated cell was inconsistent: although synaptic potentials in some cells were slightly shortened their half‐widths were always greater than the control.

7. It is concluded that cholinesterase plays a role in limiting the time course of the synaptic potential, by limiting the duration of action of acetylcholine.
Active transport of sodium and potassium by the choroid plexus of the rat
Authors: Johanson Conrad E. , Reed Donal J. , Woodbury Dixon M.
Published: December 2014

1. Choroid plexus from the lateral ventricle in the adult rat was found to contain approximately 54 m‐equiv Na+ and 89 m‐equiv K+ per kg wet tissue.

2. The total water (79%), the extracellular space (21%) and the red blood cell volume (8–9%) in choroid plexus were quantified separately by analysing the distribution of [14C]antipyrine, [14C]inulin and 51Cr‐tagged erythrocytes, respectively, between this tissue and plasma water.

3. The tissue electrolyte data together with the compartmental (space) data were used to calculate an average concentration of Na+ (39 m‐equiv/kg cell H2O) and of K+ (144) in the choroid cell.

4. Under various experimental conditions known to stimulate or inhibit the Na+—K+ transport system in other tissues, there were significant changes (10–40 m‐equiv/kg cell H2O) in the concentrations of both these cations in the plexus epithelial cells.

5. Choroid cell K+ was not independent of the concentration of K+ in plasma since substantial fluctuations in cell K+ occurred in rats rendered either hypo‐ or hyperkalaemic; also, the choroid cell apparently cannot maintain a constant gradient between itself and c.s.f. in the face of kalaemic disturbances.

6. Evidence is offered to support the hypothesis that the choroid plexus of the lateral ventricle has a Na+—K+ pump, the operation of which contributes to the maintenance of K+ homoeostasis in the
C.N.S.
Structural and functional asymmetries of myelinated branches in the frog muscle spindle
Authors: Ito F. , Kanamori N. , Kuroda H.
Published: December 2014

1. Most of the axons innervating single‐type muscle spindles in the frog sartorius muscle divide into myelinated branches at a node; one of the branches subdivides (Bs) and the other does not (Bn).

2. Electrical responses at the afferent nerve terminal of the isolated spindles were recorded extracellularly and intracellularly with micro‐electrodes, concurrently with the terminal responses by the paraffin gap method.

3. By recording spontaneous orthodromic and provoked antidromic impulses and by stimulating the nerve terminals with micro‐electrodes and inactivating the terminals with micro‐application of potassium ion, it was deduced that propagated and abortive spikes are almost always generated at the terminal of Bn (Tn), not at the terminals of Bs (Ta and Tb).

4. The site of impulse initiation, as determined in (3), was found, after measurement of the lengths of the myelinated branches in each preparation, to be essentially the terminal nearest the parent axon.

5. Selective inactivation of Tn by far‐ultra‐violet light removed both propagated and abortive spikes. Both types of spikes survived after irradiation of Ta and Tb, although the relationship between spike frequency and spindle stretch was altered. The same results were obtained after transection of the branches with a laser microbeam.
Cat retinal ganglion cells: size and shape of receptive field centres
Authors: Hammond P.
Published: December 2014

1. Receptive field centres of 144 sustained and transient retinal ganglion cells were mapped in cats under light pentobarbitone anaesthesia.

2. Sustained on‐centre, sustained off‐centre, transient on‐centre and transient off‐centre cells had different mean sizes of receptive field centre, with some overlap between their distributions.

3. For each class of cell, central fields had the smallest field‐centres; progressively larger field‐centres were encountered more peripherally.

4. All classes of ganglion cells tended to have slightly elliptical receptive field centres. Major axes of over half of all receptive fields were oriented within 20° of horizontal. These trends were independent of pupil dimensions, or of receptive field eccentricity or position in the visual field. The results almost certainly reflect asymmetry in retinal wiring.

5. Two cells of thirty‐nine tested were sensitive to axis of motion; in both cases the preferred and major axis were horizontal. A further cell was orientation specific.
Membrane potential and input resistance in acinar cells from cat and rabbit submaxillary glands in vivo: effects of autonomic nerve stimulation
Authors: Kagayama M. , Nishiyama A.
Published: December 2014

1. Membrane potential and input resistance measurements were made from acinar cells of cat and rabbit submaxillary glands in vivo, using intracellular glass micro‐electrodes.

2. The mean resting cell membrane potential was higher than previously reported, but ranged widely from −15 to −80 mV.

3. Single shock electrical stimulation of the parasympathetic nerve fibres evoked characteristic potential changes. In some cases monophasic hyperpolarizations, in others biphasic responses (depolarization — hyperpolarization) were observed.

4. The latency of the hyperpolarizing response was considerably longer (300–550 msec) than the latency of the biphasic response (about 150 msec).

5. Hyperpolarizing and biphasic responses could be observed in the same cell at different levels of membrane potential. The initial depolarization of the biphasic response was dependent on the magnitude of the resting potential in such a manner that it was very small or absent at the lowest potentials and increased gradually with increasing level of the resting potential.

6. Single‐shock stimulation of the sympathetic nerve fibres to the gland did not evoke any response. In the cat, repetitive stimulation evoked hyperpolarizing or biphasic responses similar to those seen after repetitive stimulation of the parasympathetic nerve fibres. In the rabbit small hyperpolarizations were seen in a few cells only; mostly there was no response. Repetitive stimulation of the parasympathetic nerve fibres to the rabbit submaxillary gland evoked complex potential changes mostly of the depolarization—hyperpolarization type.

7. Both single shock and repetitive stimulation of the parasympathetic nerve fibres evoked marked reductions in cell input resistance. In the hyperpolarizing cell type the conductance change sometimes preceded the potential change whereas they always occurred simultaneously in the biphasic cell type.

8. It is concluded that both the hyperpolarizing and the biphasic secretory potentials are derived from the same type of acinar cells. The neurotransmitter released by the parasympathetic nerve endings (ACh) acts on the acinar cell membrane by increasing the ion permeability.
Movements of labelled sodium ions in isolated rat superior cervical ganglia
Authors: Brown D. A. , Scholfield C. N.
Published: December 2014

1. Isolated rat superior cervical ganglia were incubated in Krebs solution containing 24Na and carbachol for 4 min at 25° C. They were then washed at 3° C for 15 min to remove extracellular 24Na and the efflux of residual intracellular 24Na stimulated by warming to 25° C.

2. During the 15 min wash at 3° C desaturation curves became exponential with a rate constant of 0·012 ± 0·001 min−1 (n = 24). This was assumed to represent loss of intracellular 24Na, and initial uptake of 24Na was calculated therefrom by back‐extrapolation to zero wash‐time. After 4 min in 24Na + 180 μ
M carbachol intracellular [24Na] so calculated was 61·6 ± 3·1 m
M (n = 18), representing 83% labelling of intracellular Na. In the absence of carbachol intracellular [24Na] was 10·0 ± 0·5 m
M, representing 49% labelling. Extracellular Na was labelled by > 90% after 4 min in 24Na. The apparent rate constant for washout of extracellular 24Na was 0·6 min−1 at 3° C and 0·95 min−1 at 25° C.

3. The loss of the residual intracellular 24Na during temperature stimulation was interpreted quantitatively in terms of an exponential decline of the bulk of intracellular 24Na with an extrusion rate constant of 0·39 ± 0·1 min−1 (n = 18), efflux being delayed by passage through the extracellular space with an effective rate constant of 0·8–1·2 min−1.

4. The peak rate constant (kC) for the desaturation curve at 25° C was 0·35 ± 0·01 min−1. An Arrhenius plot of log kC/T° K−1 yielded a two‐stage linear regression with a transition at 20° C. Activation energies of 8 and 31 kcal. mole−1 were calculated above and below this transition respectively.

5. Omission of K from the 25° C temperature‐stimulating solution reduced kC by 62%. The K‐sensitive component of extrusion rate constant was a hyperbolic function of [K]e with half‐saturation at 5·6 m
M‐[K]e and maximum kC of 0·58 min−1.

6. Cyanide (2 m
M), 2,4‐dinitrophenol (1 m
M) and ouabain (1·4 m
M) reduced kC by 50–90%. The half‐maximally inhibiting concentration of ouabain was about 60 μ
M.

7. Substitution of sucrose, Li or choline for external Na did not reduce the extrusion rate of 24Na in either 6 m
M‐[K]e or 0 m
M‐[K]e. Li stimulated 24Na extrusion in Na‐free, K‐free solution.

8. The properties of the ganglionic Na pump deduced from rates of temperature‐stimulated 24Na extrusion accord with the view that the ganglion hyperpolarization observed after Na loading by exposure to nicotinic depolarizing agents results from electrogenic Na extrusion. A comparable hyperpolarization is observed after temperature stimulation following Na loading.
Electrical impedance, ultrastructure and ion transport in foetal gastric mucosa
Authors: Wright G. H.
Published: December 2014

1. The voltage transient developed across rabbit foetal gastric mucosa in response to rectangular current pulses was measured under in vitro conditions. The short‐circuit current was also measured.

2. The voltage transients were used to calculate equivalent circuit parameters. The mucosa could be represented as two large capacitances in series, each shunted by a high conductance.

3. Electron microscopy was carried out on some preparations after the electrical measurements had been made. An extensive smooth membrane tubular system was observed on the apical sides of the cells, with openings into the gastric lumen.

4. Anoxia resulted in a reversible reduction in value of the large capacitance and short‐circuit current: the relative changes in these two quantities were very closely linked. Electron microscopy showed a large and reversible decline in the extent of the apical tubular system during anoxia.

5. It was concluded that the apical tubular system plays an important role in ion transport in this preparation. Considerations of the magnitude of the capacitances and of membrane area suggest that the smaller capacitor represents the plasma membrane. The dieletric constant of the smooth membrane of the tubular system is an order of magnitude lower than that of the plasma membrane.
Gastric and pancreatic responses to meals varying in pH
Authors: Dembinski A. , Konturek S. J. , Thor P.
Published: December 2014

1. Gastric acid response to a test meal of 10% peptone was measured in chronic gastric and pancreatic fistula cats using the Fordtran and Walsh method, monitoring the rate at which a solution of 0·5
M sodium bicarbonate had to be added to maintain constant pH of gastric content at pre‐selected values ranging from 5·0 to 1·0. Simultaneously, pancreatic secretion was determined by the standard collection technique. In this way the pH profile for the inhibition of gastric secretion and stimulation of pancreatic secretion has been established in cats.

2. A peptone meal adjusted to pH 5·0 produced gastric acid output similar to the maximal response to histamine or pentagastrin. It provoked a negligible stimulation of pancreatic flow rate and bicarbonate output but a large protein output.

3. Graded decrease of the peptone meal pH to below 4·0 resulted in inhibition of gastric acid production and in a concomitant stimulation of pancreatic secretory volume and bicarbonate output. A meal adjusted to pH 1·0 stimulated gastric secretion only about 30% of the response recorded at pH 5·0. Pancreatic secretion with a meal adjusted to pH 3·0 reached the highest level of about 70% of the maximal response to exogenous secretin.

4. Since the observed changes in the secretory activity of the stomach and the pancreas induced by test meals adjusted to pH 3·0 can be fully reproduced by exogenous secretin, it is suggested that in the cat this hormone may be responsible for the gastric inhibitory and pancreatic stimulatory mechanisms activated during normal digestion of food.
Analysis of hyperpolarizations induced by glutamate and acetylcholine on Onchidium neurones
Authors: Oomura Yutaka , Ooyama Hiroshi , Sawada Masashi
Published: December 2014

1. Four giant neurones, designated G‐H cells, in the right pleural ganglion of the marine pulmonate mollusc, Onchidium verruculatum, showed characteristic membrane hyperpolarization during applications of either acetylcholine (ACh) or
L‐glutamate. In the presence of ACh the membrane was hyperpolarized only transiently, while in the presence of glutamate the response was maintained. Significant increases in membrane conductance accompanied the changes in membrane potential.

2. In excess potassium sea water, a slight hyperpolarization occurred when the normal concentration was increased between one‐ and twofold. However, depolarization usually occurred when the concentration was increased tenfold except on a few occasions when a slight but definite hyperpolarization occurred. These changes were all accompanied by a substantial increase in the membrane conductance. This hyperpolarization was in all probability the result of an increase in chloride ion permeability caused by the release of an ACh‐like transmitter from depolarized presynaptic nerve terminals.

3. The reversal levels for glutamate‐ and ACh‐induced hyperpolarization respectively were approximately — 20 and — 17 mV with respect to the resting membrane potential.

4. By changing the external ion composition, glutamate‐ and ACh‐induced hyperpolarization were shown to be the result of an increased permeability of the subsynaptic membrane to potassium and chloride ions respectively. It appears therefore that inhibition in the same G—H cells can be activated by two different transmitter substances and that each of them activates a change in the membrane permeability to a different ion.

5. The relationship between the concentration of glutamate and the membrane conductance change was suggestive of two glutamate molecules reacting with a single receptor site.
The effect of early astigmatism on the visual resolution of gratings
Authors: Mitchell Donald E. , Wilkinson Frances
Published: December 2014

1. Orientational differences in visual resolution were measured at a number of different luminance levels on two subjects with high astigmatism that had remained optically uncorrected until the age of 10. Because of their astigmatism both of these subjects see vertical contours more clearly than horizontal contours with the unaided eye.

2. The measurements were made using sinusoidal gratings generated on the face of an oscilloscope with the refractive error carefully corrected with lenses and with the gratings viewed through 3 mm artificial pupils.

3. Visual resolution was found to be much better for vertical than for horizontal gratings for both these subjects under these conditions. The difference between the contrast sensitivities for vertical and horizontal gratings was even evident with gratings having spatial frequencies as low as 1 c/deg, but became progressively more pronounced at higher spatial frequencies. In one of the subjects the visual acuity (the cut‐off spatial frequency) for horizontal gratings was more than 3/4 of an octave lower than that for vertical gratings.

4. This is very different from the results obtained from normal subjects who typically show only a slight reduction in contrast sensitivity for oblique gratings but resolve vertical and horizontal gratings equally well.

5. The quantitative differences between the contrast sensitivities for vertical and horizontal gratings of both high and low spatial frequencies cannot be accounted for by either errors of focus in one meridian or by the presence of meridional aniseikonia.

6. In order to completely eliminate any optical explanations for these findings measurements of contrast sensitivity were made using sinusoidal interference fringes formed directly on the retina, thereby bypassing the eye's optics. Since the orientational differences in resolution persisted with this method it must be concluded that they are of neural origin.

7. By analogy with the effects on cortical physiology that follow early selective visual deprivation in cats and monkeys, it is argued that these orientational differences in resolution are a consequence of changes induced in the neural organization of the astigmat's visual system by the distorted visual input provided by the uncorrected astigmatism early in life. It is furthermore argued that the smaller orientational differences in resolution observed in normal eyes might similarly be induced by certain asymmetries in the early visual input.
A calcium ionophore stimulating the secretion of catecholamines from the cat adrenal.
Authors: Garcia A G , Kirpekar S M , Prat J C
Published: December 2014

1. Experiments were performed on perfused cat adrenal glands to examine the effect of a calcium ionophore A‐23187 in the secretion of catecholamines. 2. Ionophore (1–10 muM) caused a dose‐dependent release of catecholamines and the output was about 100‐fold greater at 10 mum than at 1 mum. 3. Release of catecholamines by the ionophore was dependent on the calcium concentration of the perfusion medium. Omission of calcium blocked the response to the ionophore while excess calcium facilitated it. 4. Magnesium antagonized the secretory response to the ionophore. Excess calcium overcame the inhibitory effect of magnesium. 5. The ionophore did not modify release of catecholamines by induced splanchnic nerve stimulation. 6. The results suggest that the ionophore, like depolarization, introduces calcium into the chromaffin cell to cause release of catecholamines.
Electrical activity of grafted myometrium and its recording by radio‐telemetry in unrestrained rabbits.
Authors: Wagner G
Published: December 2014

1. The electrical activity in myometrial grafts in fifty‐one female rabbits with ear chambers fitted with pick‐up electrodes has been monitored. An FM telemetry system has made long‐term studies possible in the freely moving animal. 2. Two distinct patterns of electrical activity were observed either arising spontaneously or provoked by oxytocin. These were the ‘long‐duration burst‘ containing about 50–150 spikes, and the ‘short‐duration burst‘ containing 1‐10 spikes. 3. The spike frequency within the long‐duration bursts varied between 0–9 and 1‐3 spikes sec‐1 and was fairly constant during the first half of the burst. The frequency of the bursts in the long series of short‐duration bursts was about 2‐3 min‐1. 4. When activity from grafts in two chambers in the same animal was monitored for long periods, spontaneous activity occurred at random throughout the day in each graft, indicating that the spontaneous activity was probably myogenic.
Comparison of the actions of porcine secretin and extracts of chicken duodenum on pancreatic exocrine secretion in the cat and turkey.
Authors: Dockray G J
Published: December 2014

1. Extracts were prepared of chicken duodenum and their actions on pancreatic secretion in urethane anasthetized turkeys and in conscious cats were compared with those of pure natural porcine secretin. 2. The chicken extracts and porcine secretin stimulated dose‐dependent increases in the rate of flow, but not the rate of protein secretion, from the pancreas in cats and turkeys. 3. Porcine cholecystokinin stimulated both the rate of flow and the rate of protein secretion from the pancrease in turkeys. 4. The doses of chicken extract required to evoke half maximal rates of flow of pancreatic juice were similar in the turkey (0–55 mg/kg) and in the cat (0–72 mg/kg). The highest concentration of bicarbonate recorded in the turkey responses was 30 m‐equiv/l. compared with 112 m‐equiv/l. in the cat. 5. The dose of porcine secretin required for half maximal rate of flow in the bird (5–9 mug/kg) was 180 times higher than in the mammal (0–33 mug/kg). In the cat the duration of responses to porcine secretin was significantly greater than to the chicken extract. 6. It is concluded that in birds there is a factor with biological properties similar but not identical to those of porcine secretin, and that this factor may regulate pancreatic secretion by a mechanism resembling the secretin mechanism in mammals.
Increased extrajunctional acetylcholine sensitivity produced by chronic acetylcholine sensitivity produced by chronic post‐synaptic neuromuscular blockade.
Authors: Berg D K , Hall Z W
Published: December 2014

1. Anaesthetized rats were paralysed for periods of up to 3 days by chronic administration of D‐tubocurarine (DTC), succinylcholine or alpha‐bungarotoxin. 2. After 3 days of treatment with DTC, the phrenic nerve remained active. Neuromuscular transmission and spontaneous miniature end‐plate potentials (m.e.p.p.s) were restored after removal of the DTC. Resting potentials and input resistances of muscle fibres that had been paralysed for 3 days were similar to those in denervated fibers. 3. Chronic neuromuscular blockade increased the binding of [125‐I]‐alpha‐bungarotoxin by extrajunctional regions of muscle. The time course of the increase was similar to that seen after denervation. Binding to muscles from animals that were anaesthetized and respirated, but not paralysed, was not increased. 4. Three days of paralysis increased the sensitivity of the extrajunctional muscle membrane to acetylcholine (ACh) applied by iontophoresis. 5. Approximately the same proportion of muscle fibres from muscles paralysed for 3 days gave overshooting action potentials in the presence of tetrodotoxin 10‐minus 6 g/ml. as did fibres form muscles denervated for 3 days. 6. Chronic paralysis did not change the accumulation of acetylcholinesterase above a ligation in the sciatic nerve. 7. These results are consistent with the idea that extrajunctional ACh sensitivity is normally controlled by muscle activity.
The distribution and movements of carbon dioxide, carbonic acid and bicarbonate between blood and milk in the goat.
Authors: Linzell J L , Peaker M
Published: December 2014

1. A–V differences and milk concentrations of respiratory gases, pH, HCO3 and H2CO3 have been measured in lactating goats and cows. 2. The pH and [HCO3 minus] of milk were significantly lower than those of plasma while milk PCO2 was virtually identical to that of mammary venous blood. [H2CO3+ dissolved CO2] was similar in milk and blood. 3. 14‐C (from injected [14‐C]HCO3 minus was found to cross the mammary epithelium in both directions. 14‐C also passed across the duct epithelium and since this epithelium has previously been shown to be impermeable to ions it is argued that 14‐C crossed in an unionized form, i.e. as CO2 and/or H2CO3. 4. Hourly milking with the aid of oxytocin raised milk pH, [HCO3 minus], [H2CO3], [Na] and E1Cl], and lowered [K], [lactose] and [phosphate]. These effects are discussed in relation to the hypothesis proposed previously for the action of oxytocin on milk composition. 5. A scheme for the distribution and movements of CO2, H2CO3 and HCO3 minus between extracellular fluid and milk is suggested, and discussed in relation to Cl minus transport.
Effects of activity in single sensory fibres on the discharge patterns of dorsal spinocerebellar tract cells.
Authors: Muñoz‐Martínez E J
Published: December 2014

1. Electrical activity of dorsal spinocerebellar tract (DSCT) was recorded extracellularly and intracellularly in Clarke's column nucleus. 2.Trains of impluses were elicited in DSCT cells by static stretch of the hind limb muscles, and the distributions of intervals between the impulses were computed. These distributions were essentially similar before and after impalement of the cells with the micropipette, suggesting that cell injury caused by penetration was insignificant. 3. Patterns of synaptic activity revealed that the DSCT cells examined were innervated by a limited number of muscle afferents. 4. In some DSCT neurons, all excitatory post‐synaptic potentials (e.p.s.p.s) elicited by a single fibre were suprathreshold, and e.p.s.p.s elicited by other afferents were usually subthreshold. These neurons discharge very regularly during muscle stretch, and the spike initiation followed nearly one‐to‐one relation in response to activity of the sensory fibre eliciting suprathreshold e.p.s.p.s. 5. The discharge pattern was irregular in other DSCT cells. In these cases, single sensory fibres evoked e.p.s.p.s. which did not always reach the firing threshold because of random fluctuation in their amplitude. 6. DSCT neurons often show low frequency discharges (about 10/sec) in the absence of sensory activation. In these conditions only small e.p.s.p.s. were detected (average, 0.53 mV) suggesting that the average membrane potential is very close (1‐i mV) to the firing threshold. 7. It is concluded that the statistical properties of firing patterns in DSCT neurons activated by muscle afferents depend on (a) the large amplitude of e.p.s.p.s., (b) their firing threshold and (c) random fluctuations in the e.p.s.p.s. amplitude.
Depression and recovery of transmission at the squid giant synapse.
Authors: Kusano K , Landau E M
Published: December 2014

1. The process of synaptic depression and recovery were studied in the squid (Loligo pealii) giant synapse with intracellular recording and stimulating electrodes in the prescence of tetrodotoxin (10‐minus 7 M). 2. When the synapse was stimulated at 50 Hz, depression occurred rapidly. Recovery after the tetanus was a first‐order process with an average recovery time constant of 4‐9 sec. The rate of recovery was independent of the amplitude of the post‐synaptic potential (p.s.p.) or the degree of depression. 3. For the first five to seven p.s.p.s in the train there was a linear relationship between depression and the total amount of transmitter previously released. This may indicate that depression in this preparation was caused by the depletion of the presynaptic store of transmitter (S). 4. Assuming that this interpretation was correct, we could show that recovery from depression during the tetanus (i.e. ‘mobilization’) proceeded about 10 times faster than after the end of the tetanus. 5. When the amplitude of the p.s.p. was varied by changing the bathing calcium concentration, [Ca], the degree of depression was correlated to the amplitude of the p.s.p. 6. When the amplitude of the p.s.p. was increased by increasing pre‐synaptic depolarization, synaptic depression was found to increase as well. However, synaptic depression increased less than the amplitude of the p.s.p., the relationship between these two measures being non‐linear. 7. This finding is interpreted to indicate that the transmitter stores, S, are closely related to the area of the presynaptic membrane which is sufficiently depolarized to release transmitter.
Stimulus‐response functions of slowly adapting mechanoreceptors in the human glabrous skin area.
Authors: Knibestöl M
Published: December 2014

1. Single unit impluses were recorded from the ulnar and median nerves of awake human subjects with tungsten electrodes inserted percutaneously in the upper arm. 2. One hundred and one slowly adapting receptors with receptive fields in the glabrous skin area were studied. The units were classified as type SA‐I and type SA‐II largely on the basis of their responses to lateral stretching of the skin. Eighty‐eight receptors did not respond to this type of stimulus (type SA‐I), whereas thirteen receptors readily responded to stretching (type SA‐II), AND OFTEN EXHIBITED DIRECTIONAL SENSITIVITY. 3. The SA‐I receptors showed no spontaneous discharge, and the discharge pattern was mostly rather irregular, whereas most of the SA‐II receptors had a spontaneous discharge, and a very regular discharge pattern. 4. The conduction velocities of the afferent were all in a A alpha range. The mean value for the SA‐I receptors was 58‐7 plus or minus 2‐3m/sec, and for the SA‐II receptors 45.3 plus or minus 3.6 m/sec. 5. The neural response to stimuli of varying skin indentation amplitudes was analyzed. The threshold for a dynamic response ranged for the SA‐I receptors from 0.15 to 1.35 mm and for the SA‐II receptors from 0.25 to 0.95 mm. The threshold for a static discharge ranged for the SA‐I receptors from 0.25 to more than 2.0 mm and for the SA‐II receptors from 0.55 to 1.65 mm. 6. The stimulus‐response functions were analysed for 25 SA‐I receptors and 2 SA‐II receptors. A hyperbolic log tangent function was the best description when the neural response was defined as the total number of impluses evoked by a stimulus of 1 sec duration. When only the static part of this type of plot was analyzed, a power function was a very good description for many units, but other functions (linear, logarithmic exponential, log tanh) were equally good or better for many units. This was also the dase when the mean impulse frequency of the sustained discharge was defined as a measure of the neural response. These two latter types of plots were clearly negatively accelerating, the exponent of the power function being 0.66 (mean).