bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein fractions from mouse salivary glands affecting epithelial cells in organ culture
Authors: Banks Barbara E. C. , Walter S. J.
Published: December 2014

1. Extracts of male mouse submaxillary gland have been fractionated on G 150 Sephadex and DEAE cellulose.

2. A number of the protein fractions obtained appear to cause proliferation of epithelial cells in organ cultures of rat tissues.

3. All fractions active in organ culture possess proteolytic enzyme activity.

4. The proteolytic enzymes trypsin, pronase and collagenase produce epithelial disorganization in organ culture.

5. The organ culture effect is reduced in the presence of proteolytic enzyme inhibitors and abolished by pretreatment of proteins with diisopropylfluorophosphonate.

6. The presence of mitotic inhibitors does not reduce the organ culture effect.

7. The effect is not associated with an increase in the DNA content of tissue explants.

8. No evidence has been found for the existence, in mouse salivary glands, of a specific growth factor acting on epithelial cells.
An electrophysiological dissection of the hypothalamic regions which regulate the pre‐ovulatory secretion of luteinizing hormone in the rat
Authors: Dyer R. G.
Published: December 2014

1. Extracellular action potentials were recorded from 299 single units in the preoptic and anterior hypothalamic areas of fifty‐two female rats anaesthetized with urethane. The units were categorized by their response to single biphasic pulses (ca. 1 mA; 1 msec duration) applied to the ventromedial/arcuate region of the hypothalamus.

2. Experiments with five lactating rats demonstrated that the effective zone of stimulation was confined within the ventromedial/arcuate region. This observation was supported by further evidence obtained during unit recording sessions.

3. Antidromic action potentials were recorded from 122 (41%) of the neurones monitored in preoptic and anterior hypothalamic areas. These Type A cells were characterized by their very slow discharge rate (median for spontaneously active units 1·2 spikes/sec) when contrasted with adjacent cells (median 3·9 spikes/sec). Orthodromic action potentials were not observed in thirty‐six Type A cells. The antidromically identified neurones had an average conduction rate of 0·32 m/sec. The absolute refractory period of the soma, computed by separation of the IS and SD components of the antidromic action potentials recorded from forty‐four neurones, ranged from < 3·0 to > 100 msec. With ten units it was not possible to obtain a soma dendritic (SD) wave by antidromic activation even though the initial segment (IS) wave was seen clearly and the orthodromic potentials consisted of both IS and SD waves.

4. Type B cells (32% of population) were excited and/or inhibited by the ventromedial/arcuate stimulation but were not antidromically activated. This post‐stimulatory change in discharge rate lasted for up to 400 msec.

5. Type C cells (27% of population) showed no change in spontaneous activity after stimulation of the ventromedial arcuate area. These neurones had discharge rates similar to Type B cells.

6. The previously reported prooestrous increase in firing rate, recorded from neurones in the ventral part of the preoptic/anterior hypothalamic area was restricted to cell Types B and C.
Systemic arterial baroreceptors in ducks and the consequences of their denervation on some cardiovascular responses to diving
Authors: Jones D. R.
Published: December 2014

1. In the duck systemic arterial baroreceptors which cause bradycardia in response to induced hypertension are located in the walls of the ascending aorta, innervated by the depressor nerves.

2. The location of the baroreceptors was confirmed both histologically and by recording activity from the depressor nerve. Stimulation of the central cut end of a depressor nerve caused transient bradycardia and a fall in blood pressure which was maintained throughout the period of stimulation.

3. Cardiovascular adjustments to submergence of 2 min duration were monitored in intact, sham‐operated and denervated ducks. The sham‐operated and denervated ducks were used in the experiments some 20–50 days post‐operation. The denervations were checked at post‐mortem.

4. In the first series of experiments on young ducks mean arterial pressure during a 2 min dive fell by 30% in intact, 17·5% in sham‐operated, and 48% in denervated ducks. In all ducks heart rate was reduced by 84–85%.

5. In a second series of experiments on older ducks sciatic artery blood flow was also recorded and mean arterial blood pressure fell by 9·2% in intact and by 53% in denervated animals, although there were no significant differences in heart rate during the 2 min dives. In normal animals sciatic vascular resistance increased after 2 min submergence by 7·86 ± 1·7 times, whereas in denervated ducks it increased by only 2·32 ± 0·5 times.

6. The role of systemic arterial baroreceptors in generation of the cardiovascular responses to submergence in ducks is discussed in terms of the input supplied by the baroreceptors to the central nervous system.
The positive dynamic current and its inactivation properties in cardiac Purkinje fibres
Authors: Fozzard Harry A. , Hiraoka Masayasu
Published: December 2014

1. The positive dynamic current in sheep cardiac Purkinje fibres was studied using ‘voltage clamp’ technique. The major portion of this current was carried by Cl− ions.

2. A pre‐step in membrane potential changed the response of this current to a subsequent depolarization in a way that is similar to the Na inactivation process described by Hodgkin & Huxley (1952a, b).

3. Recovery of this current after its activation could be described reasonably well by a single exponential process, and the time course of the recovery varied with membrane voltage.

4. The relation of steady‐state inactivation of the current to membrane voltage showed a sigmoid shape, varying from 100% at membrane potential of −30 mV to 0% at −80 mV. The membrane potential at 50% inactivation was −53 mV.

5. The Cl− current may play a role in the shape of the Purkinje fibre action potential, but exact definition depends on determining the voltage and time dependence of all the ionic currents that flow during the plateau.
Chemoreceptor properties of glomus tissue found in the carotid region of the cat
Authors: Matsuura S.
Published: December 2014

1. ‘Miniglomera’ appearing as small masses of tissue with ample vascularization were found around the common carotid artery of the cat. Physiological, gross anatomical and electron microscopic studies were conducted on these tissues.

2. The chemosensory function of each ‘miniglomus’ was evident from the behaviour of the afferent nerve fibres supplying the tissue: afferent responses became more active during asphyxia, when the blood flow through the tissue was reduced or blocked and when cyanide or ACh were applied. The afferent impulses became more infrequent during hyperventilation.

3. Sensory frequency response curves constructed against percentage of inhaled O2 showed that the impulses of single units increased in frequency with lowering of O2 content of the inhaled gas.

4. These miniglomera are innervated by afferent fibres emerging from the nodose ganglion; sometimes these fibres are contained in the aortic or common carotid baroreceptor nerves, but sometimes they emerge as independent nerves. None of the miniglomera are supplied by branches of the sinus nerve.

5. The fine structure of the miniglomus is similar to that of the carotid body. The tissue contains two types of cells: glomus cells which contain dense cored granules, and sustentacular cells whose fine processes enclose the former. Membrane densifications occur where glomus cells lie adjacent to one another or where they are contacted by nerve terminals. Nerve fibres are common in the miniglomus but they contact glomus cells less frequently than in the carotid body.
Cyclic variation of potassium conductance in a burst‐generating neurone in Aplysia
Authors: Junge Douglas , Stephens Cathy L.
Published: December 2014

1. The hyperpolarization between bursts in the R 15 cell of Aplysia is accompanied by an increase in membrane slope conductance.

2. The post‐burst hyperpolarization can be observed with ouabain, lithium, or potassium‐free solution if artificial inward current is applied. The hyperpolarization can be observed with dinitrophenol or cooling to 10° C, with no injected current. Thus, the hyperpolarization apparently is not due to the cyclic activity of an electrogenic pump.

3. A reversal potential for the post‐burst hyperpolarization can be demonstrated by passage of inward current during the inter‐burst period. The reversal of direction of the potential depends on recent occurrence of a burst.

4. The reversal potential varies with external potassium concentration, but not with chloride or sodium.

5. The post‐burst hyperpolarization is not blocked by external tetraethylammonium at a concentration which greatly prolongs the action potentials.

6. During the onset of spike blockage by, and recovery from, calcium‐free+tetrodotoxin saline, the bursts of action potentials appear to be driven by endogenous waves of membrane potential.

7. The hyperpolarizing phase of the waves in calcium‐free+tetrodotoxin medium is accompanied by an increased slope conductance.

8. A reversal potential can be demonstrated for the hyperpolarization following a wave in calcium‐free+tetrodotoxin medium by applying inward current during the interwave period.

9. The waves in calcium‐free+tetrodotoxin medium are blocked by ouabain but can be reinstated by artificial hyperpolarization.

10. The post‐burst hyperpolarization and the post‐wave hyperpolarization appear to result from a periodic increase in membrane conductance, primarily to potassium ions.
Temperature dependence of the ionic current kinetics of Myxicola giant axons
Authors: Schauf C. L.
Published: December 2014

1. The temperature dependence of the sodium and potassium conductances of Myxicola giant axons was studied in the range of 1–18° C.

2. Analysis of voltage clamp records for step depolarizations of 20–150 mV yielded Q10's for ḡNa, ḡK, and g1 of 1·3–1·5. The steady‐state parameters m∞ (v), n∞ (v) were independent of temperature. The time constants had Q10's of: 2·64 ± 0·2 for τm; 2·56 ± 0·2 for τh; 3·02 ± 0·3 for τn.

3. τh determined from the effects of prepulse duration rather than the decline in sodium current during a step depolarization had a Q10 of 2·47 ± 0·2.
Calcium inward currents in internally perfused giant axons
Authors: Meves H. , Vogel W.
Published: December 2014

1. Voltage clamp experiments were carried out on squid axons perfused with an isotonic solution of 25 m
M‐CsF + sucrose and placed in a Na‐free solution of 100 m
M‐CaCl2 + sucrose.

2. Depolarizing voltage steps produced inward currents of 4–6 μA/cm2 peak amplitude which decayed slightly during a 60 msec pulse; the inward current disappeared when the internal potential reached +50 to +60 mV and became outward for larger depolarizations.

3. Tetrodotoxin completely blocked the inward current and part of the outward current. No inward currents were seen with 100 m
M‐MgCl2 + sucrose as the external solution. Substituting acetate for external Cl− did not abolish the tetrodotoxin‐sensitive outward currents.

4. It is concluded that the inward current is carried by Ca and the tetrodotoxin‐sensitive outward current by Cs ions, both moving through the Na channel.

5. The reversal potential of the tetrodotoxin‐sensitive current was in the average +54 mV. Raising the external Ca concentration or adding NaCl to the external solution increased the reversal potential; lowering the external Ca concentration or replacing the internal CsF by a Na salt decreased the reversal potential.

6. From the reversal potentials of the tetrodotoxin‐sensitive current measured with varying external and internal solutions the relative permeabilities of the Na channel were calculated as PCa/PCs = 1/0·6, PCa/PNa = 1/10 to 1/7 and PCs/PNa = 1/22 to 1/9 by means of the constant field equation. The permeability ratios suggest that under these experimental conditions the Na channel is still primarily permeable to Na ions, although its selectivity is relatively small.

7. The time course of the tetrodotoxin‐sensitive Ca inward current was different from the time course of the Na inward current. The Na current consisted of an initial peak followed by a more slowly decaying component, the Ca current showed only the slow component.

8. The slowly inactivating tetrodotoxin‐sensitive Ca inward currents give rise to the long lasting action potentials which have first been observed by Tasaki and coworkers under similar conditions.
Sensory receptors in the sheep's foot
Authors: Evans M. H.
Published: December 2014

1. Median and ulnar nerves of anaesthetized Soay sheep have been investigated in vivo.

2. The compound action potentials of these nerves indicate that the most rapidly conducting fibres had mean velocities of 87 m/sec in the median nerve and 57 m/sec in the ulnar nerve. The mean conduction velocities of the axons responsible for the Group A γδ wave in the median nerve were 23–30 m/sec and those responsible for the Group A δ wave in the ulnar nerve conducted at 23–26 m/sec.

3. Single myelinated afferents were isolated by microdissection of median and ulnar nerves in the metacarpal region, and action potentials were recorded from hair follicle units, cutaneous mechanoreceptors, deeply situated proprioceptors, and from units of unknown function which were spontaneously active.

4. The hair follicle units fell into two categories: ‘diffuse’ units which innervated many hairs in an area of about 1–3 cm2 anywhere on the hairy skin above the hoof, and ‘localized’ units which innervated a few hairs within small areas of the skin adjacent to the hoof. The ‘diffuse’ units generally resembled the ordinary hair follicle units of other animals except that in the sheep the afferents had higher conduction velocities. The ‘localized’ units also had large myelinated axons, but their physiological properties differed in several aspects from the guard hair, tylotrich and carpal hair units which have been studied in other animals.
Activation of descending control of the spinocervical tract by impulses ascending the dorsal columns and relaying through the dorsal column nuclei
Authors: Brown A. G. , Martin H. F.
Published: December 2014

1. Micro‐electrode recordings were made from axons of the spinocervical tract in unanaesthetized decerebrate cats.

2. Orthodromic activation of the dorsal columns and dorsal column nuclei was used to condition responses evoked in spinocervical tract neurones from cutaneous nerves. Such conditioning produced inhibition of transmission through the tract. The inhibition had a time course of 200 msec or more with maximal action at 30–70 msec and was most effective against polysynaptic responses.

3. After removal of the cerebellum or section of the cerebellar peduncles the degree of inhibition was reduced but inhibition could still be evoked by activation of the dorsal columns and dorsal column nuclei.

4. Transection of the brain stem just rostral to the dorsal column nuclei removed the inhibitory effects although segmental inhibition was not affected.

5. It is concluded that impulses ascending the dorsal columns and relaying through the dorsal column nuclei can lead to activation of descending control of the spinocervical tract. Parts of the pathways involved include the cerebellum and the brain stem. It is unlikely that the cells in the dorsal column nuclei which have descending axons are concerned with the control of transmission through the spinocervical tract.
Voltage clamp analysis of acetylcholine produced end‐plate current fluctuations at frog neuromuscular junction
Authors: Anderson C. R. , Stevens C. F.
Published: December 2014

1. Acetylcholine produced end‐plate current (e.p.c.) noise is shown to be the results of statistical fluctuations in the ionic conductance of voltage clamped end‐plates of Rana pipiens.

2. These e.p.c. fluctuations are characterized by their e.p.c. spectra which conform to a relation predicted from a simple model of end‐plate channel gating behaviour.

3. The rate constant of channel closing α is determined from e.p.c. spectra and is found to depend on membrane potential V according to the relation α = BeAV (B = 0·17 msec−1±0·04
S.E., A = 0·0058 mV−1±0·0009
S.E. at 8° C) and to vary with temperature T with a Q10 = 2·77, at −70 mV. A and B in this expression both vary with T and therefore produce a membrane potential dependent Q10 for α.

4. Nerve‐evoked e.p.c.s and spontaneous miniature e.p.c.s decay exponentially in time with a rate constant which depends exponentially on V. The magnitude and voltage dependence of this decay constant is exactly that found from e.p.c. spectra for the channel closing rate α.

5. The conductance γ of a single open end‐plate channel has been estimated from e.p.c. spectra and is found not to be detectibly dependent on membrane potential, temperature and mean end‐plate current. γ = 0·32±0·0045 (
S.E.) × 10−10 mhos. Some variation in values for γ occurs from muscle to muscle.

6. It is concluded that the relaxation kinetics of open ACh sensitive ionic channels is the rate limiting step in the decay of synaptic current and that this channel closing has a single time constant. The relaxation rate is independent of how it is estimated (ACh produced e.p.c. fluctuations, e.p.c., m.e.p.c.), and is consistent with the hypothesis that individual ionic channels open rapidly to a specific conductance which remains constant for an exponentially distributed duration.

7. The voltage and temperature dependence of the channel closing rate constant agree with the predictions of a simple dipole‐conformation change model.
Release of noradrenaline from slices of cat spleen by pre‐treatment with calcium, strontium and barium
Authors: Garcia A. G. , Kirpekar S. M.
Published: December 2014

1. Spleen slices pre‐incubated for different periods at 4° C in Krebs solution containing varying concentrations of calcium, up to 96 m
M, lost their endogenous noradrenaline stores when reincubated in normal Krebs solution at 37° C for 2 hr. Rate of loss of noradrenaline was roughly related to the calcium concentration of the pre‐incubation medium and the pre‐exposure time.

2. Pre‐treatment with isotonic barium or strontium (96 m
M) Krebs solution also induced release of noradrenaline from spleen slices when re‐exposed to normal Krebs solution. Barium was more effective than either calcium or strontium.

3. The enhanced release induced by calcium pre‐treatment occurred in the absence of calcium, with or without EGTA.

4. Tissue calcium concentration of spleen slices was 0·68 m‐mole/kg. Pre‐treatment of slices with normal or 96 m
M calcium‐Krebs solution for 4 hr at 4° C increased the calcium concentration to 2·57 and 9·9 m‐mole/kg, respectively.

5. Ouabain, which caused a dose‐dependent release of noradrenaline, did not modify the release induced by calcium pre‐treatment.

6. Spleen slices prepared from cats anaesthetized with sodium pentobarbitone instead of ether were resistant to noradrenaline depletion by calcium pre‐treatment.

7. Evoked release of [3H]noradrenaline by high potassium from calcium‐pre‐treated slices did not occur in the absence of external calcium, even though the calcium pre‐treatment enhanced the tissue concentration of this ion by nearly tenfold.

8. Net uptake of noradrenaline in normal and in treated slices whose noradrenaline content was severely reduced by barium pre‐treatment or sodium withdrawal was comparable.

9. Specific activity of released and endogenous [3H]noradrenaline increased as the tissue stores of noradrenaline were reduced.

10. It is suggested that the spontaneous loss of tissue noradrenaline after pre‐treatment with high‐calcium solution was due to inhibition of sodium‐potassium‐activated ATPase by intracellular accumulation of calcium ions. Evidence is presented to suggest that vesicles depleted of their endogenous transmitter by pre‐treatment with calcium, strontium or barium, or by sodium withdrawal, are re‐used for the storage and release of exogenous noradrenaline.
Influence of previous mechanical events on the contractility of isolated cat papillary muscle
Authors: Jewell B. R. , Rovell J. M.
Published: December 2014

1. The influence of previous mechanical events on myocardial contractility has been investigated in the cat papillary muscle preparation.

2. When a muscle that had been producing a stable response under isometric conditions was allowed to shorten isotonically, its ability to do so increased in successive beats until it reached a steady level, which represented a potentiated state compared with that seen in the first isotonic beat and in the preceding stable isometric contractions.

3. The increase in tension development in the first isometric beat after a period of isotonic beating was used as an index of the degree of potentiation. It was found to be well correlated with the changes in other parameters that could have been used for this purpose.

4. The main determinants of the degree of potentiation produced by a period of isotonic beating were:

(a) the amount by which the muscle shortened. This was inversely related to the force opposing shortening (i.e. the isotonic load);

(b) the number of isotonic beats. There was some potentiation (about 10%) after a single isotonic beat, but the number of beats required for maximal potentiation (up to 25%) depended on the frequency of stimulation; about 8 beats were required at 24 min−1.

5. An isotonic release during the rise of tension in an isometric response was even more effective in potentiating the next isometric beat than an afterloaded contraction against the same load. Isotonic releases at later times had a diminishing influence on tension development in the next isometric beat.

6. In the absence of stimulation, the potentiated state produced by a period of isotonic beating decayed with a half‐time of about 50 sec. When the muscle was stimulated it disappeared sooner, and its rate of decay depended on the frequency of stimulation; at 24 min−1 about 8 beats were required to restore contractility to its previous steady level.

7. The characteristics of the decay of the potentiated state were closely similar to those of the potentiated states that can be produced by various electrical interventions, and the possibility that all of these might have the same underlying mechanism is discussed.

8. Attention is drawn to the practical implications of this phenomenon in the design of experiments in which the muscle contracts under changing mechanical conditions.
The temperature dependence of the movement of sodium ions associated with nerve impulses
Authors: Cohen L. B. , Landowne D.
Published: December 2014

1. The movement of sodium ions across the membrane of the squid giant axon was measured by the use of radioactive tracers. Unidirectional fluxes were measured at rest and when the nerve was stimulated. The difference was considered the extra flux association with nerve impulses.

2. The extra influx in intact axons at room temperature was 5·5 p‐mole/cm2. impulse. At 6° C the extra influx was 6·5 p‐mole/cm2. impulse giving a Q10 of 1/1·2.

3. In perfused axons a Q10 of 1/1·6 was obtained for the extra sodium influx in bracketed experiments on individual axons.

4. The Q10 of the extra sodium efflux associated with nerve impulses was found to be 1/1·2 in intact axons.

5. Hodgkin & Huxley had predicted a much larger temperature dependence for the extra fluxes. If this difference between prediction and experiment does not result from some experimental error, then the class of models for the ion fluxes suggested by Hodgkin & Huxley may be inapplicable.
The significance of deep body temperature in regulating the concentration of thyroxine in the plasma of the pig
Authors: Evans S. E. , Ingram D. L.
Published: December 2014

1. The activity of the thyroid gland in the pig has been assessed while thermosensitive regions of the hypothalamus or the spinal cord were cooled.

2. If the cervical region of the spinal cord was cooled for 3 hr, by means of a thermode in the epidural space, the concentration of thyroxine in the plasma increased to a maximum within the first hour but fell again to the control level or lower within 2 hr of the onset of cooling.

3. When a thermode in the preoptic region of the hypothalamus was cooled to 18 or 25° C for 3 hr, the concentration of thyroxine in the plasma increased within the first hour and then declined again. Cooling the thermode to 10° C led to a sustained increase in thyroxine concentration.

4. The increase in the concentration of thyroxine in the plasma, on cooling the hypothalamus, was of a similar magnitude whether the ambient temperature was 25 or 15°C.

5. Observations on the disappearance of radioactive thyroxine from the plasma indicated that the distribution or metabolism of thyroxine was altered by the cooling of either the hypothalamus or the spinal cord.

6. It was concluded that when the preoptic region of the hypothalamus or the cervical region of the spinal cord was cooled the rise in the concentration of thyroxine in the plasma was due at least in part to a change in the metabolism or distribution of thyroxine within the body and not entirely to the stimulation of the thyroid gland as has previously been suggested.
Dynamic properties of inferior rectus muscle of the rat
Authors: Close R. I. , Luff A. R.
Published: December 2014

1. Isometric responses of rat inferior rectus muscle to indirect and direct stimulation were compared, and conditions were found for selective direct stimulation of twitch fibres in vitro.

2. Most of the twitch fibres were qualitatively ‘fast’.

3. The influence of length on isometric contractions and the relation between relative load and speed of sarcomere shortening of fast‐twitch fibres were determined.

4. The isometric twitch contraction and half‐relaxation times of fast‐twitch inferior rectus fibres were only about one half of those of rat extensor digitorum longus fibres in the same conditions, whereas the force: velocity properties of these two fibre groups were virtually the same. These results show that the relation between intrinsic speed of shortening and duration of the active state of the contractile material is not the same for rat extraocular and hind‐limb muscles.
Two types of neurones in the myenteric plexus of duodenum in the guinea‐pig
Authors: Hirst G. D. S. , Holman Mollie E. , Spence I.
Published: December 2014

1. Intracellular recordings have been made from neurones lying in the myenteric plexus of guinea‐pig duodenum; some aspects of their membrane properties have been studied by passing current through the intracellular electrode while recording changes in membrane potential.

2. The current—voltage relationship was linear for small changes in membrane potential, input resistances ranging from 125 to 250 MΩ. Larger hyperpolarizing currents (causing changes of 20–40 mV) caused the input resistance to fall.

3. Depolarizing currents of 1 to 10 × 10−10 A initiated action potentials with amplitudes of up to 95 mV.

4. Two types of cell were distinguished when an action potential was initiated. In one group the action potential and undershoot had a form similar to that recorded from other mammalian ganglia. In the second group an action potential was followed by both an undershoot and a prolonged afterhyperpolarization which was associated with a decrease in cell resistance.

5. The two groups of cells were further distinguished by their responses to transmural stimulation. Only those cells which did not show an afterhyperpolarization could be shown to receive a synaptic input.

6. The mechanism by which each cell type generates an action potential was different. The action potentials recorded from cells which had a detectable synaptic input were abolished by tetrodotoxin. In contrast, those recorded from the other type of cells persisted in the presence of tetrodotoxin. Preliminary experiments suggest that during an action potential these cells become permeable to both sodium and calcium ions.

7. Abolition of the calcium component of the action potential in cells which generated an afterhyperpolarization abolished this latter potential.

8. The role of these two groups of cells is discussed.
Two factors responsible for the development of denervation hypersensitivity
Authors: Jones Rosemary , Vrbová Gerta
Published: December 2014

1. Innervated adult skeletal muscle is sensitive to acetylcholine at the end‐plate region only. After denervation the entire muscle membrane becomes chemosensitive. The period of greatest increase in sensitivity in rat soleus muscles following section of the sciatic nerve in the thigh is between 48 and 72 hr post‐operatively.

2. Direct electrical stimulation was found to prevent the onset of the development of denervation hypersensitivity during the first 2–3 days after nerve section. Thereafter, electrical stimulation only reduced the sensitivity of denervated muscles to acetylcholine (ACh).

3. The period of greatest increase in sensitivity follows loss of transmission and degeneration of the nerve terminals. Once this degeneration is under way, electrical stimulation is no longer as effective in preventing the development of denervation hypersensitivity.

4. Hypersensitivity is also seen in muscles on which a small piece of thread or degenerating nerve has been placed. Hypersensitivity following these procedures declines within a few days, unlike denervation hypersensitivity which persists until innervation is restored.

5. The present results suggest that activity alone cannot prevent the development of hypersensitivity in the presence of degenerating nerve fibres, or muscle damage. Activity does however counteract increased sensitivity. It is suggested that two factors interact to produce denervation hypersensitivity; the presence of degenerating nerve tissue and concomitant cellular changes bring about changes in the muscle fibre membrane causing it to become hypersensitive; and the loss of muscle activity, resulting in the persistence of hypersensitivity until innervation is restored.
The role of the autonomic innervation in the control of glucagon release during hypoglycaemia in the calf
Authors: Bloom S. R. , Edwards A. V. , Vaughan N. J. A.
Published: December 2014

1. The extent to which the autonomic innervation to the pancreas is implicated in the control of glucagon release during hypoglycaemia has been investigated in calves 3–6 weeks after birth.

2. A pronounced rise in plasma glucagon concentration occurred in normal conscious calves in response to hypoglycaemia following administration of insulin (0·1 u./kg). Prior treatment with atropine caused no significant change in the hypoglycaemic response to insulin in these animals but the rise in plasma glucagon concentration was delayed.

3. Section of both splanchnic nerves produced no significant change in the tolerance of conscious calves to this small dose of insulin and the changes in plasma glucagon concentration in these animals were within the normal range.

4. In contrast, the same dose of insulin produced severe hypoglycaemia, accompanied by convulsions, in atropinized calves with cut splanchnic nerves. In spite of the intensity of the hypoglycaemic stimulus the rise in plasma glucagon concentration was both delayed and diminished in these animals.

5. Administration of atropine alone (0·2 mg/kg) to normal fasting calves produced a significant fall in the mean plasma concentrations of both glucose and glucagon (P < 0·01) within 30 min, without affecting that of insulin.

6. A significant increase in plasma glucagon concentration also occurred in response to stimulation of the peripheral ends of the thoracic vagi in adrenalectomized calves with cut splanchnic nerves under barbiturate anaesthesia. A rise in mean plasma glucose concentration was also observed in these experiments and found to be significantly correlated with the glucagon response.

7. It is concluded that changes in either sympathetic or parasympathetic efferent activity may modify plasma glucagon concentration in the conscious calf, but that only the latter mechanism is likely to be implicated in the response to changes in plasma glucose concentration within the physiological range.
The occurrence in and actions of amino acids on isolated supra oral sphincter preparations of the sea anemone Actinia equina
Authors: Carlyle R. F.
Published: December 2014

1.
L‐glutamic acid reversibly inhibits the contractions of isolated circular muscle preparations from different body regions of the sea anemone Actinia equina to electrical stimulation.

2.
L‐glutamic acid does not cause inhibition of contraction by conversion to ammonia or γ‐amino‐butyric acid, but appears to act on a glutamate receptor.

3. It is postulated that in Actinia equina there is a receptor for glutamic acid whose structural requirements for activation are met by comparatively few analogues of glutamic acid. Of thirty‐four analogues tested, only seven were active, most were less active, and only homocysteic acid had a greater activity than
L‐glutamic acid.

4. Glutamic acid does not depress conduction of contraction in circular muscle preparations.

5. The inhibition produced by
L‐glutamic acid does not appear to be conducted from one part of a preparation to another.

6. Glutamic acid occurs in high concentrations in supra oral sphincter preparations of Actinia equina.

7. Glutamic acid is released into sea water from sphincter preparations at rest and the amount released is increased by electrical stimulation of the preparation. However, many other amino acids are released at rest and following electrical stimulation, so that it is difficult to suggest that glutamic acid may be involved as a neurotransmitter in the sea anemone.
Interocular transfer of a visual after‐effect in normal and stereoblind humans
Authors: Mitchell Donald E. , Ware Colin
Published: December 2014

1. Following inspection of a high contrast grating a test grating of a slightly different orientation will briefly appear rotated from its true orientation in a direction opposite to that of the adapting grating.

2. The extent of interocular transfer of this phenomenon (the tilt after‐effect) was measured in a number of normal subjects and in four subjects (three of whom had a strabismus) who lacked stereopsis.

3. In contrast to the normal subjects, none of the four stereoblind subjects showed any interocular transfer of the tilt after‐effect. Amongst the normal subjects the extent of transfer of this after‐effect was positively correlated with the subject's stereoacuity. Maximum transfer (70%) was found in the subject with the best stereoacuity. In many subjects transfer was greater from the dominant eye to the non‐dominant eye than vice versa.

4. By analogy with experiments on cats deprived of congruent visual input to the two eyes early in life it is argued that the stereoblind subjects lack any binocularly driven cortical neurones.
Conductance changes associated with the secretory potential in the cockroach salivary gland
Authors: Ginsborg B. L. , House C. R. , Silinsky E. M.
Published: December 2014

1. Conductance changes in the acini of the cockroach salivary gland have been examined during nerve stimulation by means of two intracellular electrodes placed in the same acinus, the first electrode being used for recording membrane potential and the second for current injection.

2. The transient hyperpolarization (secretory potential) in the acinus evoked by nerve stimuli is accompanied by a rise in membrane conductance. The conductance, however, remains high for a longer period than that of the response.

3. Applying the analysis of Trautwein & Dudel (1958) to the secretory potentials recorded in the acinus (assumed to behave electrically like a single cell) gives estimates of the ‘transmitter equilibrium potential’. The values indicate that the neurotransmitter increases the membrane potassium conductance.

4. The hyperpolarization of the acinus evoked by 10−6
M dopamine in the bathing fluid is also associated with an increase in membrane potassium conductance.
Effect of denervation on the adaptation of sarcomere number and muscle extensibility to the functional length of the muscle*
Authors: Goldspink G. , Tabary C. , Tabary J. C. , Tardieu C. , Tardieu G.
Published: December 2014

1. The effects of denervation on the response of the cat soleus muscle to immobilization at different lengths by plaster casts has been investigated for a period of 4 weeks.

2. The passive length—tension properties of the denervated immobilized muscles were not significantly different from those of non‐denervated muscles. Muscles immobilized in the shortened position showed a marked decrease in extensibility whether they were denervated or not. In all the other cases the length—tension curves were not significantly differetn from those of normal muscles.

3. The denervated soleus muscle immobilized in the lengthened position was found to produce 25% more sarcomeres in series, whilst those immobilized in the shortened position lost 35%. This adaptation was essentially the same as in muscles that had been immobilized but not denervated.

4. Denervation was found to have no effect on the recovery of muscles that had been subjected to 4 weeks immobilization in the shortened position. In these muscles the sarcomere increased back to the normal level within 4 weeks after removal of the plaster cast.

5. The adjustment of sarcomere number to the functional length of the muscles does not therefore seem to be directly under neuronal control. It appears to be a myogenic response to the amount of passive tension the muscle is subjected to.
Dynamic properties of denervated fast and slow twitch muscle of the cat
Authors: Kean C. J. C. , Lewis D. M. , McGarrick J. D.
Published: December 2014

1. Isometric and isotonic contractions were recorded from cat flexor digitorum longus (FDL) and soleus muscles denervated for 28–35 days and compared with the responses of contralateral control muscles.

2. Isometric twitch time to peak was longer in the denervated muscles than in the controls. Tetanic tension was reduced whether expressed as absolute units, per gram or per unit area. Absolute twitch tensions were reduced less below the control values with a consequent increase of twitch‐tetanus ratio. These results agree with earlier reports; but, in contrast, there was no reduction in the relative rate of rise of tension in the isometric tetanus of denervated compared with control FDL. The maximum rate of rise of tension in the twitch was only a little less than that in the fully fused tetanus in the denervated muscles.

3. Whole muscle shortening velocity was reduced in the denervated soleus with no change in the number of sarcomeres per fibre. There was a smaller change in FDL muscles. This was the result of an increase in the number of sarcomeres per fibre which followed denervation in FDL, compensating for a decreased velocity of shortening of the sarcomere. Maximum sarcomere shortening velocity was reduced by 30% relative to control values in both muscles.

4. Measurements were made of the isometric contractions resulting from pairs of stimuli in an attempt to assess the period of maximal activation in the twitch. Maximum summation occurred when the second stimulus was given close to the time of the peak of the twitch in the denervated muscles.
Potassium: potassium exchange catalysed by the sodium pump in human red cells
Authors: Simons T. J. B.
Published: December 2014

1. When red cells were so depleted of Na that Na:K exchange had almost ceased, the ouabain‐sensitive K efflux seen in K‐containing media was accompanied by an almost equal ouabain‐sensitive K influx.

2. This suggests that the Na pump in these cells was carrying out a one‐for‐one K:K exchange across the erythrocyte membrane.

3. 30–40% of the 42K efflux from resealed ghosts was sensitive to ouabain when the ghosts contained 1 m
M‐ATP, 2 m
M orthophosphate, 10 m
M‐K and less than 1 m
M‐Na, and the suspending medium contained 10 m
M‐K and 0‐Na, choline being the predominant cation.

4. In resealed ghosts, the rate of K:K exchange saturated as internal K was increased, and was half‐maximal at about 10 m
M‐K.

5. When internal ATP was maintained with a phosphocreatine:creatine phosphokinase regenerating system, K:K exchange saturated as internal ATP was increased, and was half‐maximal at about 100 μ
M‐ATP.

6. The rate of K:K exchange did not depend on whether the ADP concentration was roughly the same as the ATP concentration or very much less, suggesting that ADP did not affect the rate of K:K exchange.

7. GTP, ITP and UTP were unable to substitute for ATP in supporting K:K exchange. CTP was a poor substitute.

8. There was no evidence to support the hypothesis that K:K exchange is accompanied by a ouabain‐sensitive hydrolysis of ATP.

9. Internal Na was a strong inhibitor of ouabain‐sensitive K efflux from ghosts containing 9 m
M‐K. 4 m
M‐Na was sufficient to produce 90% inhibition.

10. The rate of K:K exchange depended on the orthophosphate concentration inside the ghosts (confirming Glynn, Lew & Lüthi, 1970). The curve obtained suggested that the rate was half‐maximal at about 1·7 m
M orthophosphate.

11. These experiments suggested that inhibition by internal K is an important factor affecting the Na efflux from intact red cells. Experiments measuring Na:K exchange as a function of internal Na in low‐K ghosts supported this hypothesis.

12. The significance of these findings is discussed.
The effect of contractile activity on fibrillation and extrajunctional acetylcholine‐sensitivity in rat muscle maintained in organ culture
Authors: Purves D. , Sakmann B.
Published: December 2014

1. The effect of contractile activity on the initiation of spontaneous action potentials (fibrillation) and on extrajunctional acetylcholine‐sensitivity has been studied in single fibres in strips of previously denervated rat diaphragm maintained in organ culture for up to 10 days.

2. Following removal of the diaphragm from the animal, fibrillation slowed and usually stopped altogether for about 24–36 hr. Thereafter, spontaneously active fibres were found in all cultured muscle strips.

3. At any one time, about ¼ to ⅓ of fibres impaled with micro‐electrodes were active (defined as more than one action potential/10 sec), with a mean discharge frequency of 4·5/sec (range 0·1–24/sec).

4. The duration of continuous activity in single fibres was, on average, 21–22 hr; a period of activity was followed by a longer inactive interval. Thus activity in single fibres is cyclical.

5. Direct stimulation of fibrillating strips for 24 hr at 10/sec suppressed spontaneous activity for 1–3 days.

6. Conversely, blockade of spontaneous activity with tetrodotoxin for 72 hr led to a two‐ to threefold increase in the number of fibrillating fibres when the drug was washed out; in some strips nearly all fibres became spontaneously active.

7. The mean rate of activity of diaphragm fibres during normal breathing, determined by recording single units from the phrenic nerve in lightly anaesthetized animals, is about 18/sec.

8. Direct stimulation of cultured diaphragm strips in a pattern similar to breathing for 7–8 days at an average rate of 10–12/sec (or 5/sec in some experiments), resulted in a marked reduction (about 95% in experiments at 10/sec) in extrajunctional sensitivity to ionophoretically applied ACh.

9. Direct stimulation for 24 hr at 10/sec (comparable to a period of spontaneous activity) caused only a small reduction in extrajunctional ACh‐sensitivity.

10. We conclude that spontaneous activity in single fibres under these conditions occurs cyclically because activity, over a period of hours, inhibits the ability of the fibrillating fibre to initiate further action potentials. Repeated self‐inhibition of spontaneous activity probably explains why denervated muscle fibres remain highly sensitive to extrajunctionally applied ACh.
Reversal of the physiological effects of monocular deprivation in kittens: further evidence for a sensitive period
Authors: Blakemore Colin , Van Sluyters Richard C.
Published: December 2014

1. It was confirmed that suturing the lids of one eye (monocular deprivation), until only 5 weeks of age, leaves virtually every neurone in the kitten's visual cortex entirely dominated by the other eye. On the other hand, deprivation of both eyes causes no change in the normal ocular dominance of cortical neurones, most cells being clearly binocularly driven.

2. Kittens were monocularly deprived until various ages, from 5 to 14 weeks, at which time reverse suturing was performed: the initially deprived right eye was opened and the left eye closed for a further 9 weeks before recording from the visual cortex.

3. Reverse suturing at 5 weeks caused a complete switch in ocular dominance: every cell was dominated by the initially deprived right eye. Reverse suturing at 14 weeks, however, had almost no further effect on ocular dominance: most cells were still driven solely by the left eye. Animals reverse sutured at intermediate ages had cortical neurones strongly dominated by one eye or the other, and they were organized into clear columnar groups according to ocular dominance.

4. Thus, between 5 weeks and 4 months of age, there is a period of declining sensitivity to both the effects of an initial period of monocular deprivation and the reversal of those effects by reverse suturing.

5. The small proportion of binocular cells in reverse sutured kittens (which have never had simultaneous binocular vision) often differed considerably in their receptive field properties in the two eyes. In particular, if the cells were orientation selective in both eyes the two preferred orientations could differ by up to 70°.

6. The relative importance of innate and environmental contributions to the properties of cortical cells is discussed.
A statistical analysis of the release of acetylcholine at newly formed synapses in striated muscle
Authors: Bennett M. R. , Florin T.
Published: December 2014

1. A statistical analysis has been made of the changes in the binomial parameters n and p during transmitter release from motor‐nerve terminals when synapses are forming in either regenerating or reinnervated mammalian muscle.

2. The amplitude—frequency distribution of e.p.p.s evoked by a single impulse was well predicted by binomial statistics at all junctions analysed allowing values of n and p to be determined. At most of these junctions, p > 0·5 and Poisson statistics did not predict the observed distributions at all.

3. During the changes in quantal content which occur during short trains of impulses or during continual stimulation over minutes, no significant change in p was detected. Changes in quantal content of the e.p.p. were therefore determined by n.