bluuebunny/crossref_metadata_2025 huggingface dataset:
The differential effects of tetraethylammonium and zinc ions on the resting conductance of frog skeletal muscle
Authors: Stanfield P. R.
Published: December 2014

1. The effects of tetraethylammonium (TEA) and zinc ions on the resting conductance of frog muscle were examined using a method which permitted control of the membrane potential near the end of a muscle fibre and measurement of an approximation of the membrane current.

2. TEA reduced the amplitude of the inactivating inward current obtained on hyperpolarizing, both when this was measured as initial current [Im(0)] less the estimated chloride current and as [Im(0) — Im(∞)]. 115 m
M‐TEA reduced the amplitude of [Im(0) — Im(∞)] by about 85%.

3. TEA had little effect on the time constant with which the inward potassium currents inactivated. This finding appeared to be in conflict with the view that the inactivation is due to depletion of potassium from the T‐system, though the results in standard Ringer were in good agreement with such an hypothesis.

4. In the standard chloride Ringer, the resting membrane resistance was 3530 Ω cm2. 115 m
M‐TEA increased this 1·6 times to 5580 Ω cm2.

5. The effect of TEA on voltage—current relations obtained in high K2SO4 solutions was also examined. With large pulses, the voltage—current relations in TEA and control solutions tended to become linear. This linear part could be extrapolated and subtracted from the voltage—current relation.

6. TEA, at a concentration of 150 m
M, reversibly reduced by 88% the amplitude of the currents obtained during both depolarizing and hyperpolarizing pulses; this figure was obtained after subtraction of the linear part of the relation, which was itself unaffected by TEA and which represented a resistance of 5600 Ω cm2.

7. The reductions in the inactivating potassium current and in the current flowing through the inwardly rectifying potassium channel in high K2SO4 solutions fit, fairly closely, a concentration—effect relation for TEA with a dissociation constant of 20 × 10−3
M.

8. Also investigated were the slow time‐dependent changes in membrane potential occurring when [K]o is altered from 2·5 to 10 m
M at constant chloride (120 m
M). The findings were consistent with the view that TEA reduced the potassium conductance without much effect on the chloride conductance. In particular, when muscles equilibrated for 1 hr in 10 m
M‐K Ringer were returned to 2·5 m
M‐K, the initial rate of repolarization was reduced, even though the driving force on K was slightly larger than in the control experiment.

9. Zinc ions appeared to be without effect either on the amplitude of the inactivating potassium current obtained when square hyperpolarizing pulses were applied to the fibre membrane, or on its time constant.

10. In standard Tris‐buffered Ringer, the membrane resistance was 3350 Ω cm2. Zinc Ringer (2·5 m
M) increased this rather more than twice to 6830 Ω cm2.

11. It is concluded that the two agents, TEA+ and Zn2+, which both reduce delayed potassium currents in muscle, act in different ways on the resting conductance of frog muscle.
An analysis of the inhibition of phrenic motoneurones which occurs on stimulation of some cranial nerve afferents
Authors: Biscoe T. J. , Sampson S. R.
Published: December 2014

1. Inhibition and excitation of spontaneous phrenic nerve discharges in response to stimulation of the sinus, glossopharyngeal, aortic and superior laryngeal (SLN) nerves has been investigated in cats.

2. The inhibition, in response to a single shock, had a latency of 5‐10 msec and lasted for 20–40 msec; the response to SLN stimulation was the most prolonged.

3. Excitation of phrenic motoneurones also occurred and was seen either before or after the end of the inhibition of the inspiratory burst and sometimes also during expiration.

4. Intravenous strychnine blocked the inhibition.

5. Intracellular recording from phrenic motoneurones showed that hyperpolarization was evoked by each nerve during the central phrenic depolarizing potential (CPDP) but only rarely in the interval between these potentials.

6. When the CPDP was suppressed, hyperpolarization could sometimes be evoked.

7. There were no changes in amplitude or time course of hyperpolarization during the passage of current through the cell membrane. No change in membrane conductance could be shown by passing current pulses.

8. Raising the pressure in the carotid sinus also depressed phrenic activity and evoked a hyperpolarization whilst the CPDP was suppressed.

9. Inspiratory interneurones in the brain stem were suppressed by nerve stimulation and by a rise in carotid sinus pressure.

10. Expiratory interneurones in the brain stem were both excited and suppressed by electrical stimuli and unaffected by a change in carotid sinus pressure.
Effects of intragastric hyperosmolal solutions on gastric functions
Authors: Harper A. A. , Reed J. D. , Smy J. R.
Published: December 2014

1. The effects of intragastric hyperosmolal solutions on resting and secreting stomachs of anaesthetized cats have been studied.

2. Hyperosmolal solutions reduced acid secretion in response to histamine and gastrin. There was a significant correlation between increase in osmolality and decrease in acid response to small doses of gastrin. A continuous acid secretion produced by large doses of gastrin was not significantly reduced.

3. The loss of H+ from resting stomachs is related to the pH and osmolality of the instilled fluid. The loss was greatest at low pH and high osmolality, but was insufficient to account for the H+ loss from secreting stomachs at similar pH and osmolality.

4. The Na+ output into resting stomachs was increased by hyperosmolal solutions, the increase being related only to the osmolality of the solutions. For the same degree of hyperosmolality there was no difference between the sodium output into resting and secreting stomachs.

5. The H+ deficit associated with intragastric hyperosmolal conditions does not seem to depend upon a neural mechanism, a blood‐borne hormone, or a reduction in gastric blood flow. Evidence is presented that diffusion, exchange or neutralizing mechanisms are unlikely to be responsible for the H+ deficit. It is suggested that inhibition of oxyntic cell activity by release of a chemical agent from the surface cells of the mucosa is the most likely explanation of the results observed.

6. The possible physiological significance of intragastric hyperosmolal inhibition of acid secretion is discussed.
Acetylcholine in adrenergic terminals of the cat iris
Authors: Ehinger B. , Falck B. , Persson H. , Rosengren A.-M. , Sporrong B.
Published: December 2014

1. Acetylcholine was bio‐assayed in the normal cat iris, and also after selective sympathetic or parasympathetic denervation. Sympathetic denervation caused no significant change in the acetylcholine content of the cat iris, whereas selective parasympathetic denervation reduced the acetylcholine content below the level of detectability, which on the average was at about 5% of the acetylcholine content of the normal iris.

2. It is concluded that if adrenergic terminals contain any acetylcholine, it is less than what is detectable with the methods available at present, and most certainly less than 6% of the acetylcholine content of cholinergic neurones.

3. On the basis of these and other recently obtained observations, the hypothesis of Burn & Rand (1965) of a cholinergic link in the adrenergic transmission is discussed. It is proposed that it is more reasonable to suppose an interaction between peripheral adrenergic and cholinergic terminals than to presume a cholinergic mechanism within adrenergic nerve fibres.
The effect of procaine on neuromuscular transmission
Authors: Kordaš M.
Published: December 2014

1. The mechanism of procaine action on post‐synaptic receptors for acetylcholine was studied by recording the end‐plate current at membrane potentials ranging from about +30 to about −140 mV.

2. It has been found that at resting membrane potential of about −60 to −80 mV the end‐plate current has a fast initial and a slow late component. During hyperpolarization of the muscle fibre the amplitude of the slow component is depressed and its half‐time lengthened. When the membrane potential is inverted the difference in the time course of both components is much less pronounced or absent.

3. It is suggested that procaine modifies the receptor response induced by acetylcholine, and that this modification is dependent on membrane potential.
The proprioceptive reflex control of the intercostal muscles during their voluntary activation
Authors: Davis J. Newsom , Sears T. A.
Published: December 2014

1. A quantitative study has been made of the reflex effects of sudden changes in mechanical load on contracting human intercostal muscles during willed breathing movements involving the chest wall. Averaging techniques were applied to recordings of electromyogram (EMG) and lung volume, and to other parameters of breathing.

2. Load changes were effected for brief periods (10–150 msec) at any predetermined lung volume by sudden connexion of the airway to a pressure source variable between ± 80 cm H2O so that respiratory movement could be either assisted or opposed. In some experiments airway resistance was suddenly reduced by porting from a high to a low resistance external airway.

3. Contracting inspiratory and expiratory intercostal muscles showed a ‘silent period’ with unloading which is attributed to the sudden withdrawal from intercostal motoneurones of monosynaptic excitation of muscle spindle origin.

4. For both inspiratory and expiratory intercostal muscles the typical immediate effect of an increase in load was an inhibitory response (IR) with a latency of about 22 msec followed by an excitatory response (ER) with a latency of 50–60 msec.

5. It was established using brief duration stimuli (< 40 msec) that the IR depended on mechanical events associated with the onset of stimulation, whereas stimuli greater than 40 msec in duration were required to evoke the ER.

6. For constant expiratory flow rate and a constant load, the ER of expiratory intercostal muscles increased as lung volume decreased within the limits set by maximal activation of the motoneurone pool as residual volume was approached.

7. The ER to a constant load increased directly with the expiratory flow rate at which the load applied, also within limits set by maximal activation of the motoneurone pool.

8. For a given load, the ER during phonation was greater than that occurring at a similar expiratory flow rate without phonation when the resistance of the phonating larynx was mimicked by an external airway resistance.

9. It is argued that the IR is due to autogenetic inhibition arising from tendon organs and that the ER is due to autogenetic excitation arising from intercostal muscle spindles.

10. The initial dominance of inhibition in this dual proprioceptive reflex control was not predicted by the servo theory. It is proposed that the reflex pathways subserving autogenetic inhibition are under a centrifugal control which determines in relation to previous experience (learning) the conditions under which autogenetic facilitation is allowed.
The relationship of blood flow to myoglobin, capillary density, and twitch characteristics in red and white skeletal muscle in cat
Authors: Reis Donald J. , Wooten G. Frederick
Published: December 2014

1. The fractional distribution of blood flow was measured by the isotope dilution method and absolute blood flow estimated in twenty‐four muscles of chronically prepared, unanaesthetized cats.

2. In the quiet, alert cat the estimated mean muscle blood flow ranged from 5·9 to 39·3 ml./min 100 g muscle. Flow was three times greater in grouped red than white limb muscles.

3. The myoglobin concentration ranged from 0·88 to 3·91 mg/g muscle. The myoglobin concentration of grouped red exceeded that of white muscle and varied in each muscle directly and linearly with blood flow with a high correlation (P < 0·001).

4. Capillary density was estimated by determination of alkaline phosphatase activity. Alkaline phosphatase activity was significantly greater in red than white muscles and varied directly with fractional blood flow in these same muscles with a high correlation (P < 0·001).

5. Contraction time was generally two to three times longer in red than white muscle. There was a direct and highly correlated relationship (P < 0·001) between blood flow and contraction time.

6. The direct linear relationship between muscle blood flow and myoglobin concentration, capillary density, and contraction time characteristic of quiet wakefulness was lost during rapid eye movement sleep or excitement produced by electrical stimulation of the hypothalamus as a consequence of selective changes in flow in red and white skeletal muscle.

7. The type of metabolism of any skeletal muscle is adapted to its activity during quiet, alert behaviour, rather than during sleep or excitement.
Effect of neurohypophysial hormones on fluid movement across isolated bladder of Rana cancrivora, Rana temporaria and Bufo melanostictus
Authors: Dicker S. E. , Elliott Annie B.
Published: December 2014

1. The rate of fluid movement across the wall of isolated amphibian urinary bladder was estimated using hemi‐bladders of the tropical euryhaline Rana cancrivora, the temperate R. temporaria and the tropical Bufo melanostictus.

2. The rate of water outflow across the bladder walls was: Rana cancrivora, 4·8 μl./cm2.hr; R. temporaria, 7·2 μl./cm2.hr; Bufo melanostictus, 3·7 μl./cm2.hr.

3. When neurohypophysial peptides were added to the serosal solution the rates of water outflow were increased; dose—response curves were prepared relating the augmented rate of fluid movement to the concentration in the bathing fluid of vasopressin, oxytocin or vasotocin.

4. The potencies of the peptides in respect of bladders of each species were:

Vasopressin, B. melanostictus:Rana temporaria:R. cancrivora, 500:20:1.

Oxytocin, R. temporaria:B. melanostictus:Rana cancrivora, 100:5:1.

5. The ratio of sensitivity of the bladder of each species to the presence of the different peptides was:

R. cancrivora, vasotocin:oxytocin:vasopressin, 1000:5:1.

R. temporaria, oxytocin:vasopressin, 15:1.

Bufo melanostictus, oxytocin:vasopressin, 1:30.

6. The effect of extract of the pituitary gland of Rana cancrivora was examined on R. cancrivora bladder. It had a dose—response curve similar to the dose—response curve of vasotocin.

7. The vasotocin content of the pituitary gland of R. cancrivora was estimated

(a) from the dose—response curves using R. cancrivora bladder,

(b) by a three‐point assay using R. cancrivora bladder and

(c) by its effect on water uptake across the skin of Bufo melanostictus. One pituitary gland of Rana cancrivora was found to contain about 0·1 μg vasotocin.

8. The urinary bladder of R. cancrivora was less responsive to neurohypophysial peptides than the bladder of R. temporaria or Bufo melanostictus.

9. The hormonal content of the pituitary gland of Rana cancrivora was smaller than that found in other amphibians.
Electrical activity in pancreatic islet cells: effect of ions
Authors: Dean P. M. , Matthews E. K.
Published: December 2014

1. Intracellular micro‐electrode recording techniques have been used to study the effects of varying the external ion concentration on the membrane potential and glucose‐induced electrical activity in cells from mouse islets of Langerhans.

2. Increasing [K]o to 47 m
M depolarized islet cells without inducing electrical activity. Normal action potentials were generated in response to glucose after removal of [K]o for 60 min.

3. Reduction of [Cl]o to 12 m
M did not affect the membrane potential and glucose still induced electrical activity.

4. Reduction of [Na]o to 26 m
M increased the amplitude of action potentials; subsequently the cells depolarized.

5. Removal of [Ca]o caused cells, already firing action potentials intermittently in response to glucose, to change their pattern of discharge to one of continuous firing. The time constant of the action potentials was also increased. Depletion of calcium for 60 min before addition of glucose prevented the appearance of electrical activity.

6. Increasing [Ca]o threefold to 7·7 m
M in the presence of glucose, 11·1 m
M, increased action potential amplitude to 12 mV, but a tenfold increase of [Ca]o to 25·6 m
M completely blocked action potential discharge.

7. Exposure of islet cells simultaneously to reduced [Na]o (26 m
M) and increased [Ca]o (7·7 m
M) increased the amplitude of glucose‐induced action potentials to about 20 mV.

8. Strontium, 2·56 m
M, was an effective substitute for [Ca]o, 2·56 m
M, and maintained a normal pattern of electrical activity in response to glucose.

9. Increasing the magnesium concentration tenfold to 11·3 m
M did not block electrical activity whereas manganese, 2 m
M, blocked glucose‐induced action potentials and depolarized islet cells.

10. It was concluded that the action potential induced by glucose in islet β‐cells is due predominantly to calcium entry and that sodium ions tend to repress this calcium influx.
Decamethonium in depolarized muscle and the effects of tubocurarine
Authors: Creese R. , England J. M.
Published: December 2014

1. In rat diaphragms immersed in solution containing 5 m
M potassium the maximum uptake of labelled decamethonium was found at the end‐plate region. In muscles depolarized in solution containing potassium methyl sulphate the uptake was reduced but a peak concentration at the end‐plate region was still demonstrated.

2. The uptake of labelled decamethonium increased steadily with time and was interpreted in terms of the entry of decamethonium into the fibres. The permeability at 10–100 μ
M was similar to that of sodium.

3. The uptake of decamethonium at the end‐plate region was dependent on the concentration. At low values the uptake in depolarized muscle was uniform along the fibres. Increase in concentration produced a peak at the end‐plate region. This was interpreted as a change in permeability such that half the maximum effect was present at a concentration of approximately 5 μ
M.

4. At high concentrations the influx showed saturation and carrier‐like kinetics with a half‐saturation concentration of 400 μ
M.

5. Tubocurarine inhibited the peak uptake in depolarized diaphragm. The results were consistent with competitive inhibition with an inhibitory constant of 0·07 μ
M.

6. Acetylcholine in high concentration also inhibited the uptake of decamethonium in the end‐plate region of depolarized muscle.
Entry of decamethonium in rat muscle studied by autoradiography
Authors: Creese R. , Maclagan Jennifer
Published: December 2014

1. When a steady plasma level of decamethonium was maintained by infusion in rats, the labelled compound became concentrated in the region of the end‐plate of skeletal muscle, as shown by scintillation counting.

2. The distribution of tritium‐labelled decamethonium in single muscle fibres was studied by autoradiography of frozen sections, with resolution less than 1 μ.

3. After intravenous injection of a dose of decamethonium which produced partial paralysis it was shown that the labelled compound had entered muscle fibres in the region of the end‐plate, and for several hundred microns on either side of the end‐plate.

4. Entry of decamethonium could be demonstrated as early as 30 sec after intra‐arterial injection. There was no evidence of any redistribution of labelled drug for a period of 2 hr after the initial entry.

5. Previous administration of tubocurarine markedly reduced the entry of labelled decamethonium.
Observations on the mechanism of salicylate‐induced antipyresis
Authors: Cranston W. I. , Hellon R. F. , Luff R. H. , Rawlins M. D. , Rosendorff C.
Published: December 2014

1. Fever has been produced in conscious rabbits, first, by injection of leucocyte pyrogen into the lateral cerebral ventricle and, second, by local cooling of the hypothalamus.

2. Both intravenous and intraventricular salicylate produce antipyresis during an established fever due to intraventricular leucocyte pyrogen. This is incompatible with the hypothesis that salicylate acts by interfering with the passage of leucocyte pyrogen from the circulation into the hypothalamus.

3. Intravenous sodium salicylate has no effect on the fever due to local cooling of the hypothalamus. This suggests that salicylates do not act on central or peripheral efferent pathways involved in thermoregulation.
The transparency of the mammalian cornea
Authors: Cox J. L. , Farrell R. A. , Hart R. W. , Langham M. E.
Published: December 2014

1. A theoretical and experimental analysis of the relationship of the corneal stromal ultrastructure with light transmission has been made in an attempt to resolve recent contradictory explanations of corneal transparency.

2. The spatial distribution of collagen fibrils in electronmicrographs of rabbit corneal stroma has been analysed in terms of a radial distribution function. The results indicate the presence of local order extending to at least 200 nm from individual fibrils.

3. The observed spatial distribution of the collagen fibrils was used as a basis to compare the theoretically derived and the experimentally determined values of light transmission. It has been found that the transparency of the normal cornea may be explained by the quasi‐random structure revealed by the electronmicroscope.

4. Histograms of the collagen fibril diameter in normal rabbit corneal stroma revealed the range to be 12·5–32·5 nm and the mean value to be approximately 20 ± 1·5 nm. Corneal swelling did not change the collagen fibril diameter significantly.

5. It is concluded that the size and distribution of collagen fibrils revealed in electronmicrographs are consistent with the observed transparency of normal stromas.

6. A marked heterogeneity in the spatial distribution of collagen fibrils was found in the swollen cornea. This is qualitatively consistent with the observed decrease in transparency.
Skeleto‐fusimotor fibres in the rabbit
Authors: Emonet‐Dénand Françoise , Jankowska Elżbieta , Laporte Y.
Published: December 2014

1. In rabbits, repetitive stimulation of single motor axons to lumbrical muscles elicits both a contraction of extrafusal muscle fibres and an increase in the discharge frequency of spindle primary endings.

2. This activation of the sensory endings can be attributed to the contraction of intrafusal muscle fibres because it persists after the contraction of extrafusal muscle fibres has been suppressed by selective curarization of their neuromuscular junctions.

3. In non‐curarized preparations the frequency of most of the afferent discharges continues to increase when rates of stimulation of motor fibres exceed the tetanic fusion frequency of the extrafusal muscle fibres.

4. The effect of repetitive stimulation of motor fibres that supply extrafusal and intrafusal muscle fibres was studied on the responses of primary endings to phasic stretch. Of twelve fibres, eight were found to exert a dynamic effect and four a static one.

5. Selective curarization of the extrafusal neuromuscular junctions does not modify the nature of the static and dynamic effects.
Urinary excretion of adrenal steroids, catecholamines and electrolytes in man, before and after acclimatization to cold in Antarctica
Authors: Budd G. M. , Warhaft N.
Published: December 2014

1. Urine samples were collected from four men before and during test cold exposures in Melbourne, Australia, and Mawson, Antarctica. Changes in the response of body temperature to the test exposures showed that the men had acclimatized to cold at Mawson.

2. Excretion rates of 17‐hydroxycorticosteroids and 17‐ketosteroids were significantly greater at Mawson than in Melbourne, in both the pre‐exposure and exposure periods.

3. Excretion rates of noradrenaline, adrenaline, sodium, potassium and creatinine did not differ significantly between Mawson and Melbourne, nor did urine flow rates.

4. During the cold exposure significant increases occurred, to the same extent at Mawson as in Melbourne, in urine flow rate and in all measured urinary constituents except creatinine.
The kinetics of influx of calcium and strontium into rat intestine in vitro
Authors: Papworth D. G. , Patrick G.
Published: December 2014

1. The role of uptake across the brush border in the intestinal absorption of calcium has been studied by examining the kinetics of influx into slices of rat intestine in vitro. Both mucosal and serosal surfaces were exposed to the medium.

2. The rate of influx was accurately defined by a two‐component expression comprising a saturable (Michaelis—Menten) term and a second term linear with concentration. Influx across the mucosal surface of closed sacs was similar, and the saturable component for slice influx could be ascribed mainly to transport across the mucosal surface. The half‐saturation constant for Ca was near 1 m
M. This component was predominant at normal luminal concentrations of free Ca in the duodenum of young rats, but less so in jejunum and ileum and in older rats.

3. The same kinetic expression applied to Sr influx, with a half‐saturation constant of 2‐3 m
M, and possibly also to Ba with an even higher value.

4. The saturable component of Ca influx was greatly reduced by 2,4: dinitrophenol (DNP); influx was also inhibited by iodoacetate, cyanide and at 0° C. Inhibition commenced soon after exposure of the slices. A high concentration of DNP also caused an increase in the linear component of Ca influx.

5. The kinetics of Ca influx across the mucosal surface agreed closely with the kinetics of steady‐state absorption of Ca either across the whole mucosal epithelium in vivo or across the entire intestinal wall in vitro. This agreement supports the hypothesis that Ca entry across the brush border is the rate‐limiting step in absorption; such a hypothesis would allow net Ca translocation while preserving a low intracellular concentration of ionic Ca in the mucosal epithelial cells.
Afferent vagal fibres with an expiratory discharge in the rabbit
Authors: Luck J. C.
Published: December 2014

1. An investigation was undertaken in the spontaneously breathing, anaesthetized rabbit to observe the response of vagal sensory endings to inflation and deflation stimuli which were sufficient to produce Hering—Breuer reflexes.

2. When artificial changes in lung volume were produced by applying step changes in intratracheal pressure, activity in pulmonary stretch receptors increased with inflation and decreased with deflation.

3. A small number of vagal afferent fibres were encountered which exhibited a discharge with a respiratory modulation consisting of an increase in activity during the phase of expiration. This pattern of discharge was accentuated when the animal was artificially ventilated with the chest either open or closed.

4. These expiratory receptors were stimulated by step changes in intratracheal pressure of −5 and +15 mm Hg to produce a high frequency, slowly adapting discharge which persisted for the 10 sec period of the pressure application. The endings were localized in the extrapulmonary bronchi and lung parenchyma and the afferent fibres were myelinated with conduction velocities of 10·6–29·5 m/sec.

5. The pronounced effect of deflation stimuli on the endings indicates that they probably act as one of the afferent mechanisms in the Hering—Breuer deflation reflex.
Permeation and distribution of deuterated and triated water in smooth and striated muscle
Authors: Elford B. C.
Published: December 2014

1. The diffusion of deuterated water (HDO) into and out of isolated guinea‐pig taenia coli and frog sartorius was followed by means of a recording electronic microbalance.

2. A comparison was made of the rates of efflux of deuterated and tritiated (HTO) water using the microbalance and a standard tracer technique.

3. The time course of the exchange of HDO in both smooth and striated muscle was fitted to the sum of two exponential functions; however, it was not possible to correlate sizes of the intra‐ and extracellular spaces in the muscles with the sizes of the two compartments in model systems based on compartmental theory of tracer kinetics.

4. The efflux of HDO, which was measured by means of the microbalance under stagnant conditions, occurred at a rate approximately 3 times slower than the efflux of HTO which took place while muscles were agitated vigorously in their bathing media.

5. There was a marked deviation at short times from a double exponential time course during the efflux of HTO.

6. Values of the tracer water permeability, Pd, of smooth and striated muscle fibres, and the extracellular space, E, of the muscles were obtained using a computer to numerically evaluate the series solutions of the equations describing the permeation of labelled water in the muscles.

7. It was necessary to assume a value for the diffusion coefficient of the tracer in extracellular fluid in order to compute a unique fit to an exchange curve.

8. Values of Pd and E given by the analysis depended upon the method used for monitoring the exchange, and an interpretation of this dependence was made difficult by the variation in the thickness of unstirred layers on the surface of the muscles under the different experimental conditions.
Selective reinnervation of two cell populations in the adult pigeon ciliary ganglion
Authors: Landmesser Lynn , Pilar G.
Published: December 2014

1. Presynaptic fibres innervating the adult pigeon ciliary ganglion were cut 2 mm proximal to the ganglion. The modification of transmission in the ciliary and choroid cell populations was studied after periods of 6 hr—100 days.

2. Transmission failed after 2 days and for the next 10 days there was no transmission through the ganglion. Long latency responses in both ciliary and choroid nerves were first observed at 13–15 days, and the latency decreased toward control values in 40 days. Electrical transmission reappeared in the ciliary population in about 26 days.

3. Presynaptic fibres innervating the ciliary population have higher conduction velocities and lower electrical thresholds than those innervating the choroid group. This relation was maintained throughout the reinnervation process. Fibres innervating the extraocular muscles also regenerated and achieved conduction velocities similar to their control values.

4. In two experiments out of seventeen, a few fast conducting, low threshold fibres, presumably stray ciliary fibres, innervated choroid cells and induced electrical transmission.

5. It is concluded that each group of cells, ciliary and choroid, was reinnervated in a highly selective manner by its original class of presynaptic fibres, and that the presynaptic ciliary elements cause the specializations necessary for electrical transmission.
Voltage clamp of the Aplysia giant neurone: early sodium and calcium currents
Authors: Geduldig D. , Gruener R.
Published: December 2014

1. The membrane properties of the Aplysia giant neurone were studied under controlled voltage conditions. Emphasis was placed on the early transient currents resulting from step polarizations applied while the ganglion was immersed in different test solutions.

2. Early inward‐going currents were observed when the neurone was bathed in normal saline (containing both Na and Ca), in Ca‐free (Na‐containing) saline, in Na‐free (Ca‐containing) saline, and in the normal saline to which tetrodotoxin 10−5 g/ml. was added. When both Na and Ca are absent from the bathing solution no evidence for early inward‐going current could be found.

3. When tetrodotoxin is added to the normal saline, the maximum inward‐going current is reduced, and no further reduction of this current is observed when the external Na‐concentration is subsequently halved in the presence of the drug. When the external Ca‐concentration is increased fivefold in the presence of the drug, the maximum transient current increases significantly.

4. Hyperpolarizing prepulses result in a membrane inactivation in the presence of tetrodotoxin or in the absence of Na. In the presence of Na (and absence of tetrodotoxin) no such voltage‐dependent inactivation occurs, and for this case, inactivation results only from depolarizing prepulses.
The effect of carotid body denervation upon the respiratory response to hypoxia and hypercapnia in the duck
Authors: Jones D. R. , Purves M. J.
Published: December 2014

1. Respiratory responses to altered Pa, O2 at constant Pa, CO2 and altered Pa, CO2 at constant Pa, O2 were measured in fourteen unanaesthetized ducks 5‐9 weeks old.

2. All the ducks responded to the inhalation of a few breaths of 100% O2 with a fall in V̇E of between 11 and 17% of control, and to the reduction in Pa, O2 from control levels (93–101 mm Hg) to 38–47 mm Hg with an average increase in V̇E of 190% of control which was potentiated by raising the level of CO2.

3. Ventilation approximately doubled when Pa, CO2 was raised to 55 mm Hg, the greatest sensitivity to changes in Pa, CO2 being over the range 40–45 mm Hg.

4. Carotid body denervation was carried out in nine ducks and the respiratory responses were modified. The fall in V̇E with inhalation of 100% O2 was abolished in all ducks and the rise in V̇E with hypoxia was abolished in six. The increase in V̇E as Pa, CO2 was altered in steps was unaffected but the rate at which V̇E increased in response to 4% CO2 was markedly reduced.

5. It is concluded that the chemoreceptor regulation of respiration in ducks is similar to that observed in non‐diving animals.
The effect of ions on the photoresponses of pigeon cones
Authors: Arden G. B. , Ernst W.
Published: December 2014

1. Pigeon cone receptor potentials have been identified in a preparation of isolated, incubated retina.

2. There is an approximately linear relationship between response amplitude and sodium concentration of the bathing medium.

3. A decrease of chloride ions produces results equivalent to a decrease of sodium ions. The response amplitude is a power function of the product of the sodium and chloride concentrations. For most experiments, the exponent is ca. 1.

4. After treatment of the retina with ouabain, responses vanish, but can be temporarily restored, in normal, or inverted polarity, by appropriate changes in sodium or chloride concentration.

5. Ammonium and potassium ions can substitute quantitatively for sodium ions. Lithium ions initially carry response currents, but later block all responses. Bromide, nitrate and thiocyanate can substitute for chloride ions.

6. The response wave form, and the amplitude/light intensity relationship are independent of ions.

7. Models of the photoreceptor are discussed. It is concluded that the membrane potential of the cone in light is chiefly determined by the distribution of anions across the membrane, and in darkness there is an increase in outer limb cation permeability.
Effects of tetraethylammonium chloride on the membrane activity of guinea‐pig stomach smooth muscle
Authors: Ito Y. , Kuriyama H. , Sakamoto Y.
Published: December 2014

1. The effects of tetraethylammonium (TEA) on the membrane activity of the antral circular muscle of the guinea‐pig stomach were investigated with micro‐electrode and double sucrose gap methods.

2. In a concentration of 1‐1·5 × 10−3 g/ml. (3‒5 m
M), the membrane potential was not influenced; the membrane resistance measured by inward current pulses remained the same but the rectifying property of the membrane was suppressed.

3. TEA (1–1·5 × 10−3 g/ml.) enhanced the spike amplitude markedly even from fibres which generated graded responses.

4. TEA (1–1·5 × 10−3 g/ml.) did not increase the maximum rate of rise of the spike but decreased the maximum rate of fall of the spike markedly.

5. In Na‐free (Tris or sucrose) solution, in K‐deficient and excess‐K solutions, TEA (1–1·5 × 10−3 g/ml.) suppressed the rectifying property of the membrane and enhanced the spike amplitude.

6. Atropine (10−6 g/ml.) had no effect on the enhancement of the spike amplitude produced by TEA.

7. The minimum concentration of Ca ions required for the effect of TEA on the spike amplitude was one fifth of the normal concentration. TEA also enhanced the spike amplitude in Sr—Krebs.

8. The possible role of TEA on the membrane activity is considered to be due to suppression of the K conductance when the membrane is depolarized. Alternative possible roles of TEA on the spike amplitude are also discussed.
The relation between L‐methionine uptake and sodium in rat small intestine in vitro
Authors: Newey H. , Rampone A. J. , Smyth D. H.
Published: December 2014

1. Uptakes of
L‐methionine and mannitol by rat jejunum in vitro were measured over test periods from 5 to 120 sec after 30 min pre‐test periods in the presence or absence of Na.

2. The initial stage in methionine uptake was dependent on the presence of Na+ and to a lesser extent on the K+ concentration. In contrast mannitol uptake was independent of Na and K.

3. The initial stage in methionine uptake can be reactivated 30–60% within 5 sec by replacing an Na‐deficient intestine into an Na‐containing medium.

4. Initial methionine uptake was greater with a normal intracellular and low medium Na concentration than with a high medium and low intracellular Na concentration. It is suggested that the intracellular Na concentration is a critical factor, more important than the Na gradient, in determining the rate of amino acid transfer across the luminal membrane.
Evidence for two types of sodium conductance in axons perfused with sodium fluoride solution
Authors: Chandler W. K. , Meves H.
Published: December 2014

1. Voltage clamp experiments were carried out on squid giant axons internally perfused with 300 m
M‐NaF + sucrose. K‐free artificial sea‐water, −0·3 to 3·5° C, was used externally.

2. Membrane currents were corrected for capacitative and leakage components, and the resulting Na current was converted to Na conductance, gNa. An attempt was made to fit changes in gNa according to the Hodgkin—Huxley model, namely [Formula: see text].

According to the model ḡNa is a constant, m∞ and h∞ are steady‐state values which depend only on voltage, τm−1 and τh−1 are rate constants which also are functions only of voltage.

3. Stepwise depolarizations from the holding potential (−67 to −83 mV) to a potential which varied from −10 to +63 mV resulted in an exponential decline of h from its initial level to a final, non‐zero level. If the test depolarization was preceded by a positive prepulse (duration, 19–105 msec; voltage, −6 to 94 mV) the rate constant for h, τh−1, was increased roughly threefold with practically no change in the final level.

4. The steady‐state level of h was studied by using prepulses of varying amplitude followed by a test depolarization. In one such experiment a value of 0·34 was obtained for a 105 msec prepulse to −49 mV. The same value for the steady level of h was obtained from analysing a record taken at +52 mV. If the potential was switched from −49 to +52 mV there was a transient increase in gNa although h∞ had the same value at these two potentials.

5. Recovery from depolarization was studied by repolarizing the fibre for varying lengths of time, then applying a test depolarization. If the first depolarization was strongly positive (for example, 70 mV), so that the steady level of h was large (0·39), the currents associated with the test pulse could not be fitted on the basis of an exponential increase in h during the recovery period. Rather, the results suggested that on repolarization h rapidly decreased initially, then slowly increased.

6. These results can be explained by assuming that h is given by the sum of two components, h1 and h2. Changes are represented kinetically by h1 ⇌ x ⇌ h2, where x signifies the inactive state. The distribution is shifted to the left at negative potentials and to the right for positive ones. The resulting Na conductance is comprised of two types: the first type, ḡNam3h1, is similar to the Hodgkin—Huxley system and underlines the usual transient increase in gNa associated with depolarization; the second type, ḡNam3h2, is maintained with depolarization and gives rise to a steady level of gNa.
Rates of oxygen consumption and of anaerobic glycolysis in renal cortex and medulla of adult and new‐born rats and guinea‐pigs
Authors: Dicker S. E. , Shirley D. G.
Published: December 2014

1. Rates of oxygen uptake and of anaerobic glycolysis were estimated in slices from the renal cortex and medulla (a) of adult rats and guinea‐pigs, (b) of new‐born (1−, 5‐ and 21‐day‐old) rats and of guinea‐pigs of 1, 12, 21, 24 and 120 hr age.

2. In the adult rat, QO2 values for the cortex were 12·55 ± 0·20 (22) and for the medulla: 8·56 ± 0·17 (22) μl./hr.mg dry weight, while in the new‐born rat (24 hr old) they were 10·99 ± 0·46 (12) and 9·33 ± 0·18 (9) μl./hr.mg dry weight respectively.

3. Values for QCO2N2 (anaerobic glycolysis) in the 14 hr old new‐born rat were in the renal cortex 9·65 ± 0·35 (5) and in the medulla 7·39 ± 0·43 (5) μl./hr.mg dry weight; while in the adult they were 2·25 ± 0·08 (16) and 5·76 ± 0·14 (16) μl./hr.mg dry weight, respectively.

4. In the adult guinea‐pig values for QCO2N2 were of the same order as in the adult rat, though the rate of O2 uptake was for the cortex 8·12 ± 0·22 (12) and for the medulla 5·02 ± 0·23 (11) μl./hr.mg dry weight.

5. Though the QO2 values in the renal cortex and medulla were smaller in the 1 hr old new‐born guinea‐pig, they were already increasing in the 12 hr old neonate.

6. The results are discussed in the light of enzyme changes occurring during the process of maturation of the nephron as indicated by histochemical observations.
Galactose transport across the hamster small intestine; the effect of sodium electrochemical potential gradients
Authors: Smulders Anthony P. , Wright Ernest M.
Published: December 2014

1. Measurements of galactose unidirectional fluxes across the isolated mucosa of the hamster small intestine were made under a variety of experimental conditions designed to investigate the interrelationships between galactose transport, the sodium ion and electrical potentials.

2. Galactose transport was inhibited by lowering the sodium concentration in the mucosal and/or serosal solutions and by increasing the p.d. across the tissue. This inhibition of galactose transport was judged to be irreversible.

3. Transport was unaffected by decreasing the p.d. across the tissue.

4. These results are discussed in relation to the model proposed to explain galactose transport across the intestine.
Relation of cardiovascular changes in fighting to emotion and exercise*
Authors: Adams D. B. , Baccelli G. , Mancia G. , Zanchetti A.
Published: December 2014

1. To obtain evidence on the relative importance of exercise and emotion in the cardiovascular changes of fighting in the cat, the changes during fighting were compared with changes during a mild non‐emotional exercise (walking on a treadmill at low speed), and during confrontation without fighting (preparation for fighting), an emotional condition accompanied by no or very little motor activity.

2. The direction of change of all variables we measured, iliac and mesenteric flows and conductances, total peripheral conductance, heart rate, cardiac output and blood pressure, was similar in both fighting and exercise.

3. Some of the cardiovascular manifestations of preparation for fighting were very different from those of motor activity. These were iliac vasoconstriction, a fall in cardiac output, and often a strong bradycardia, all of these changes being in the opposite direction to changes during exercise and fighting.

4. It is suggested that the changes during preparation for fighting represent the cardiovascular manifestations of an emotional state, and that during fighting these manifestations are superseded and masked by changes due to motor activity.
Unit activity in rat diencephalic islands — the effect of anaesthetics
Authors: Cross B. A. , Dyer R. G.
Published: December 2014

1. Unit activity was recorded with steel micro‐electrodes from 486 hypothalamic neurones in rat diencephalic island preparations.

2. The histograms of firing frequencies for populations of hypothalamic units from unanaesthetized preparations and from those under urethane anaesthesia were not significantly different. The firing rates of both were significantly faster than those observed in intact brains under urethane.

3. The mean distance between stable units in unanaesthetized island preparations did not differ significantly from that in preparations anaesthetized with urethane.

4. The response of individual neurones to intravenous injections of urethane was variable, and apparently not associated with the onset or maintenance of anaesthesia. Some showed transient acceleration, some deceleration and some no change in rate or pattern of discharge.

5. All neurones tested were slowed or stopped by intravenous injections of subanaesthetic doses of sodium methohexitone (Brietal). The responses were highly reproducible and dose‐dependent.

6. Brietal also produced a fall in arterial pressure and depressed respiration. Inhalation of amyl nitrite evoked larger hypotensive responses but did not affect unit activity; nor did inhalation of CO2 (hypercapnia) or N2O (hypoxia).

7. It is concluded that urethane anaesthesia is not associated with any direct action on hypothalamic neurones. The depression of firing rate in hypothalamic neurones induced by Brietal may represent an important forebrain mechanism in anaesthesia by this agent.
Changes in monoamine oxidase and catechol‐o‐methyl transferase activities after denervation of the nictitating membrane of the cat
Authors: Jarrott B. , Langer S. Z.
Published: December 2014

1. The question of cellular localizations of monoamine oxidase and catechol‐o‐methyl transferase, enzymes involved in the metabolism of noradrenaline, has been investigated by following the changes in the enzyme activity of the smooth muscle of the cat nictitating membrane after sympathetic denervation. Any falls in enzyme activity coinciding with the time course for degeneration of the sympathetic nerve endings (2–3 days) can reasonably be ascribed to a former localization of the enzyme within the sympathetic nerve.

2. Monoamine oxidase activity of the inferior and medial smooth muscle was significantly reduced 3 days after sympathectomy and remained reduced 14 days after sympathectomy.

3. A correlation was found between the fall in monoamine oxidase activity and the endogenous noradrenaline concentration of the contralateral normal muscle, indicating that the higher the endogenous noradrenaline concentration, the greater the fall in monoamine oxidase activity after denervation.

4. It was concluded that the fall in monoamine oxidase activity after denervation indicated a former localization of the enzyme within the sympathetic nerve endings.

5. The fall in monoamine oxidase activity of the denervated muscle was significantly less measured with benzylamine as a substrate than with tyramine. This suggested that the neuronal monoamine oxidase may have different properties than the extraneuronal enzyme.

6. A small fall in the catechol‐o‐methyl transferase activity of denervated smooth muscle was found and a correlation between the fall in enzyme activity and endogenous noradrenaline indicated that in this smooth muscle a proportion of the catechol‐o‐methyl transferase activity may be of presynaptic origin.