bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of depolarization of motor nerve terminals upon the release of transmitter by nerve impulses
Authors: Hubbard J. I. , Willis W. D.
Published: December 2014

1. Depolarizing currents were applied to motor nerve terminals in the rat phrenic nerve—diaphragm muscle preparation in vitro.

2. During the passage of depolarizing currents the amplitude of the presynaptic nerve action potentials and of end‐plate potentials (e.p.p.s) was reduced in proportion to the current strength.

3. The reduction in e.p.p. amplitudes was shown to be due to a reduction in the number of quanta released.

4. An excess of Mg ions or the previous application of a hyperpolarizing current could prevent the reduction of e.p.p. amplitudes and quantal contents by depolarizing current.

5. Depolarizing current application prevented later hyperpolarizing currents affecting e.p.p. amplitudes.
The release of 5‐hydroxytryptamine from rabbit small intestine in vitro
Authors: Gwee M. C. E. , Yeoh T. S.
Published: December 2014

1. A method is described by which the lumen of intestinal segments may be perfused separately and simultaneously under identical conditions of perfusion pressure and temperature, and the rate of appearance of 5‐hydroxytryptamine (5‐HT) into the serosal fluid measured.

2. 5‐HT appeared in the serosal fluid from quiescent segments of rabbit intestine at a rate of about 4·0 ng/cm intestine/hr and about 14·0 ng/cm intestine/hr from segments performing active peristaltic movements.

3. For both quiescent and active segments, when the perfusion fluid contained a monoamine oxidase inhibitor, nialamide (Niamid), the rate of appearance of 5‐HT was increased and if, in addition, 5‐HT was present in the perfusion fluid the rate of appearance of 5‐HT in the serosal fluid was even greater.

4. The rate of appearance of 5‐HT from the intestine of rabbits pretreated with reserpine was about 0·8 ng/cm intestine/hr and Niamid only slightly increased this rate. However, if 5‐HT as well as Niamid were present the rate of appearance of 5‐HT was about 6·0 ng/cm intestine/hr.

5. Possible explanations for these findings are discussed.
The effect of small hydrostatic pressure gradients on the rate of active sodium transport across isolated living frog‐skin membranes
Authors: Nutbourne D. M.
Published: December 2014

1. The rate of active sodium transport across living isolated skins from Rana temporaria was measured when the skins were bulged inwards and outwards by small constant hydrostatic pressure gradients and by pushing them mechanically in the absence of such gradients. The effect of pressure gradients in the absence of bulging was also studied.

2. An apparatus was designed to circulate Ringer solution to each side of the skin at constant temperature, flow and pressure. The pressures were controlled to within 0·5 mm H2O.

3. It was found that bulging the skins in the absence of hydrostatic pressure gradients had no effect on sodium transport but that pressure gradients of less than 5 mm H2O had a marked effect, increasing transport when the pressure was higher on the outside of the skin, and decreasing it when the pressure was higher on the inside.

4. It is concluded that increasing surface area does not influence sodium transport, whereas small hydrostatic pressure gradients have a marked effect.

5. Possible causes for this phenomenon are discussed and its significance is considered with special reference to sodium reabsorption from the proximal tubule of the kidney.
The effect of hypo‐ and hypertonic solutions on volume and ion distribution of smooth muscle of guinea‐pig taenia coli
Authors: Brading Alison F. , Setekleiv J.
Published: December 2014

1. The intra‐ and extracellular spaces and ionic content of the taenia coli of the guinea‐pig have been measured in a series of bathing solutions in which the tonicity varied from 0·5 to 3 times the tonicity of the normal Krebs solution.

2. Equilibrium of the tissue in the experimental solution is reached within about 30 min.

3. The absolute values of the parameters measured have been shown to depend on the blotting technique used. These differences were eliminated by expressing the results as a percentage of the values found in the normal Krebs solution.

4. In hypertonic solutions the cell behaves as a perfect osmometer, the cell volume changing in proportion to the tonicity of the bathing medium. Only a small amount of cations is lost from the cells. A considerable amount of chloride is lost, making the postulation of its replacement by some other anions necessary in order to maintain electroneutrality of the intracellular solution.

5. In hypotonic solutions the cells do not behave as predicted for a perfect osmometer. In 0·5 hypotonic solution an actual decrease in cell volume was observed associated with an increase of the extracellular space probably due to penetration of [14C]sorbitol into the cell. The intracellular ionic concentration was decreased. These findings suggest damage of the cell membrane.

6. The observed hyperpolarization of the membrane in hypertonic solution can be explained by the increased intracellular potassium concentration.
Response of the cat's pad eccrine sweat glands to intravascular injections of catecholamines
Authors: Foster K. G.
Published: December 2014

1. Using a sensitive method for detecting and monitoring sweat secretion, a study has been made of the effects of adrenaline and noradrenaline on the cat's pad sweat gland activity in the anaesthetized cat.

2. Intravenous or intra‐arterial injections of adrenaline or noradrenaline only very occasionally caused these glands to secrete.

3. The predominant effect of these drugs on glands which are already secreting in response to plantar nerve stimulation is inhibitory.

4. The catecholamine inhibition could be reduced or blocked by phentolamine, but not by propranolol, dibenamine or phenoxybenzamine.

5. It is concluded that these glands can be directly activated by intravascular injections of adrenaline or noradrenaline, but that the inhibitory effect of concomitant vasoconstriction usually prevents a response being detected at the skin surface.
Degeneration secretion from parotid glands after section of the auriculotemporal nerves at different levels
Authors: Emmelin N.
Published: December 2014

1. In cats under ether or hexobarbitone anaesthesia the auriculotemporal nerve was cut near the parotid gland on one side and 12‐20 mm more proximally on the other. After 22‐64½ hr the cats were anaesthetized with chloralose and the parotid ducts cannulated. Degeneration secretion of saliva which appears after post‐ganglionic parasympathetic denervation was found to start 2‐5½ hr later in the gland denervated proximally than in that denervated distally. It ceased, on the other hand, later in the former than in the latter gland.

2. Before degeneration secretion had started spontaneously it could be provoked by intravenous injection of acetylcholine, methacholine, carbachol or eserine and the effect was more pronounced on the gland denervated distally. When it had ceased spontaneously it could also be provoked, and the effect on the other gland was now more marked.

3. Earlier it has been assumed that while a nerve is degenerating there is a period when the nerve endings are unable to retain in a normal way acetylcholine still being synthesized. It is now suggested that this period starts later after proximal than after distal denervation because more of the material required for the normal function of the endings is available in a long piece than in a short piece of nerve.
Spectral properties of dark‐adapted retinal ganglion cells in the plaice (Pleuronectes platessa, L.)
Authors: Hammond P.
Published: December 2014

1. Spectral, spatial and temporal properties of receptive fields of dark‐adapted, on—off retinal ganglion cells in the intact eye of the plaice, were analysed by recording from their axon terminals in the superficial layers of the optic tectum with indium micro‐electrodes.

2. Two cell‐types were identified. The first gave fast‐adapting, spectrally opponent on—off responses without centre‐surround subdivisions of the receptive field. On and off response‐components were mutually antagonistic. The second type gave slow‐adapting on—off or off responses for different stimulus positions within the receptive field, with centre‐surround or adjacent field configurations. Only on—off centre cells, showing mutual antagonism between field centre and surround, or off centre cells with inhibitory centres, were found. These cells had weak opponent or non‐opponent properties.

3. Most cells of each type received inputs both from cones and rods. At stimulus intensities suprathreshold for cones, response‐components gave spectral peaks which have been classified into one of four wave‐length ranges; blue, 440‐460 nm; blue‐green, 470‐490 nm; green, 510‐540 nm; and orange, 560‐590 nm. No cells analysed gave sensitivity maxima in the red. At low stimulus intensities all cells with rod input gave a single spectral peak between 510 and 530 nm.
Effect of sodium content on sodium efflux from human red cells suspended in sodium‐free media containing potassium, rubidium, caesium or lithium chloride
Authors: Maizels M.
Published: December 2014

1. Human red cells treated with lactose solution and loaded with NaCl and BCl subsequently exchange cation with a nutrient BCl medium. B is the same in cells and medium, and is either K, Rb, Cs or Li. In these circumstances Na always moves outwards with the concentration gradient, but the efflux is largely active.

2. With suspensions in media containing Ca2+, the total Na efflux depends on the amount of Na in the cells and on the nature of cation B. Thus for any given value of mean cell Na (Nam) in excess of 30 m‐equiv/l. cells, the effect of B on the amount of Na efflux is K > Cs > Rb > Li, while with Nam between 0·7 and 5 m‐equiv/l. cells, the sequence is Cs > Li > K, Rb. With Nam between 5 and 30 m‐equiv/l. cells, intermediate sequences may be demonstrated for the effects of B on Na efflux. This applies both to the efflux itself and to the flux: concentration ratio, FCR.

3. FCR for passive Na efflux in these circumstances is determined by adding strophanthin G to the medium. It varies inversely with the duration of exposure to Ca2+ in the exchange and nutrient media, but not with the nature of cation B. FCR for passive efflux is probably little affected by the value of Nam.

4. By deducting passive from total Na efflux, active Na efflux is obtained, and variations in the latter with cell Na content, and with B, result in FCR curves similar to those obtained with total Na efflux.

5. Total and passive Na efflux have also been measured in Ca‐free media. Here the passive efflux is considerable, and with Na + K cells in KCl media FCR increases with Nam, but in other systems this change is not significant. However, the rate of passive efflux into LiCl media is less than that for KCl or CsCl media. Owing to the magnitude of passive flux in Ca‐free systems, the total Na efflux is also increased, but FCR for active Na efflux is quantitatively and qualitatively similar to that occurring in systems containing Ca2+.

6. The effects of B and Nam on Na efflux give a series of sequences for B which recall some of those obtainable when chemically modified glass membranes separate solutions of salts, and which are attributable to the charge on the membrane and the hydration of the cations involved. However, certain sequences obtained with red cells do not occur with glass membranes. This difficulty is resolved if it be assumed that throughout the range of Nam (0‐80 m‐equiv/l. cells) active B influx at the external cell face modifies linked Na efflux according to the series K > Rb, Cs > Li, while with Nam between 0 and 30 m‐equiv/l. cells (and high complementary B), cations escaping passively compete with active efflux of Na inhibiting the latter according to the series K, Rb > Li > Cs. Both these series could theoretically be explained in terms of surface charges and hydration of cations.

7. Li‐loaded cells in nutrient KCl or other media failed to show active Li efflux.
A note on transmembrane potential in dermal melanophores of the frog and movement of melanin granules
Authors: Martin A. R. , Snell R. S.
Published: December 2014

1. Transmembrane potentials were measured and distribution of melanin granules observed in dermal melanophores of the isolated frog's web.

2. In normal Ringer solution, melanin granules were aggregated in the cell bodies and the transmembrane potentials were usually in the range 70‐90 mV.

3. Addition of alpha‐melanocyte stimulating hormone (α‐MSH) to the bathing solution resulted in dispersion of the melanin granules into the processes of the cells, without any accompanying change in membrane potentials. Altering the membrane potentials by changing the external K+ concentration had no effect on melanin migration.

4. It is concluded that migration of melanin granules in these cells is unrelated to cell membrane polarization.
Cable properties of smooth muscle
Authors: Abe Y. , Tomita T.
Published: December 2014

1. The cable properties of smooth muscle of guinea‐pig taenia coli were studied by intracellular recording of electrotonic potentials produced by square current pulses and alternating current applied with external electrodes.

2. An electrical model of the smooth muscle was constructed to test how the junctional resistance between cells affected the cable properties. The model consisted of a series of short cables (representing cells) which were connected by junctional resistances.

3. It was concluded, from the experiments on the living tissue and on the model, that the electrotonic potential in smooth muscle can be expressed by the ordinary cable equation used for nerve and skeletal muscle fibres, even though the junctional resistance is of the same order of magnitude as that of the myoplasmic resistance.

4. The cable equation was used to analyse the membrane parameters from the electrotonic potential, from the time course of the foot of the spike and from the conduction velocity. The analysis indicates that the smooth muscle has a membrane capacity of 2‐3 μF/cm2 and a membrane resistance of 30‐50 kΩ cm2.
The effect of an exteroceptive stimulus on the concentration of melanocyte‐stimulating hormone in the pituitary of lactating rats
Authors: Deis R. P. , Orias R.
Published: December 2014

1. A study was made of the effect of an exteroceptive stimulus, produced by a team of lactating rats and of litters while suckling, on the pituitary melanocyte‐stimulating hormone (MSH) activity of a group of lactating rats.

2. After being isolated for 9 hr from their litter, one group of lactating rats was killed after being allowed to nurse for 30 min, another group was subjected to the exteroceptive stimulus for 15 min and then killed. Control rats were killed after 9 hr of isolation from the litter without being subjected to either suckling or the exteroceptive stimulus.

3. The group of rats which had suckled their young showed a pituitary MSH activity equal to 35 ± 2·29%, and the group exposed to the exteroceptive stimulus an activity equal to 59·5 ± 3·16% of that in the control animals.

4. When deaf rats were used, only the suckled mother showed a decrease of the pituitary MSH activity which was similar to that obtained with the normal suckled mother, indicating that the exteroceptive stimulus depended on hearing for its effect.

5. A light dose of sodium pentobarbitone was sufficient to block the effect of suckling and the auditory stimuli on the pituitary MSH activity.

6. The role of the central nervous system in this phenomenon and the possibility that MSH is implicated in the process of lactation are discussed.
Thyroxine deiodination during cold exposure in the rat
Authors: Hillier A. P.
Published: December 2014

1. The urinary radio‐iodide excretion following injection of [131I]thyroxine and tri‐iodothyronine is increased in acutely cold‐exposed, thyroidectomized rats.

2. This cold response is demonstrable in animals which are fed or fasted or deprived of both food and water. Cold exposure does not increase the rate of urinary excretion of a tracer dose of radio‐iodide. It is concluded that cold exposure accelerates the rate of deiodination of both thyroxine and tri‐iodothyronine.

3. It is confirmed that both adrenaline and noradrenaline administered in vivo can enhance the rate of thyroxide deiodination.

4. The sympathetic blocking agents guanethidine and bethanidine reduce the extra deiodination of thyroxine induced by cold exposure. Bethanidine was also found to reduce the deiodination of tri‐iodothyronine during cold.

5. There is a positive correlation between the deiodination of thyroxine and the urinary catecholamine excretion in the cold‐exposed but not the warm‐exposed rat.

6. It is suggested that the enhanced deiodination during cold exposure is mediated by the release of noradrenaline from the sympathetic nervous system.
Cortical conditions for fused binocular vision
Authors: Burns B. Delisle , Pritchard R.
Published: December 2014

1. The behaviour of twenty‐six single neurones has been studied in the visual cerebral cortex of the cat's neurologically isolated and unanaesthetized forebrain. In a separate series of experiments binocular vision was investigated in five human subjects.

2. Units in the cat's brain were excited by two straight, light‐dark edges, projected independently, one upon each retina; these edges were given identical, artificial saccadic movements. The average response of neurones was measured from the post‐stimulus‐histogram (
P.S.H.), which provided the probability of unit‐discharge at various times after the pattern movement.

3. A district within either eye‐field could usually be found, such that the saccadic movements of edges passing through this part of the field, caused maximal responses; this part of each field is termed the ‘representative district’. The most exciting orientations of the stimulating patterns were similar for both eyes. A cell excited by similarly oriented patterns, ‘aligned’ through the representative districts for each eye, exhibited dramatic spatial summation. Mutual inhibition between retinal inputs was never seen.

4. The response of cortical neurones to such aligned patterns was always greater than that when one pattern was misaligned by displacement in either direction from its representative district.

5. When the pattern in one eye was inverted, the cell gave less response to aligned than to misaligned patterns.

6. Human subjects, viewing similar inverted patterns through a mirror stereoscope, could only obtain stable fusion with a 5 min arc misalignment of the optic axes.

7. In other experiments, one eye of each subject was presented with a white rectangular bar upon a black background, while the other eye was excited by a similar black bar upon a white background. Stable fusion was reported, providing percepts of either one single low contrast bar or two neighbouring bars of high contrast. There was a range of relative pattern positions over which alignment of the eyes sought the former percept in preference to the high contrast pattern.

8. These results are consistent with the hypothesis that the mammalian visual system maintains binocular fusion by continuously hunting those eye directions that provide the greatest local cortical responses to saccadic movements, restricted to the smallest possible areas of the visual cortex.
The relationship of energy expenditure and spontaneous activity to the aphagia of rats with lesions in the lateral hypothalamus
Authors: Morrison S. D.
Published: December 2014

1. Lesions in the lateral hypothalamus of rats always produced an immediate increase in total energy expenditure. The increase was maintained for 24 hr or longer only in rats that became and remained aphagic. Rats that showed no recovery from the aphagia and were maintained by tube feeding showed a second, larger increase in metabolic rate after about 7 days.

2. The increase in total energy expenditure was associated, initially, with almost continuous motor activity. With continued aphagia an abnormally differentiated pattern of activity appeared at the same time as the second increase in metabolic rate, and the compartment of energy attributable to activity remained high (34% as compared with 23% in normal rats). These changes were accompanied by a recovery of an instrumental response for food (lever pressing), of interest in offered foods and of grooming activity.

3. Metabolic abnormality not attributable to activity was indicated by increased creatinine excretion of aphagic but not of hypophagic rats.

4. Rats that recovered spontaneous feeding after aphagia returned towards a normal differentiated pattern of activity, with bursts of activity separated by periods of rest, but showed residual abnormality in creatinine excretion.

5. The intimate association between increase of energy expenditure, abnormality of motor activity and the aphagia produced by lateral hypothalamic lesions is consistent with the hypothesis that motor incoordination or disorganization is a cause of the aphagia.
Ionic environment of neurones and glial cells in the brain of an amphibian
Authors: Cohen M. W. , Gerschenfeld H. M. , Kuffler S. W.
Published: December 2014

1. Experiments were performed to determine the relative contribution of the blood plasma and of the cerebrospinal fluid (c.s.f.) to the ionic environment of neurones and glial cells within the brain of the amphibian Necturus maculosus.

2. The concentrations in the blood plasma of untreated control animals were 99 ± 2 m
M for Na+ and 2·0 ± 0·1 m
M for K+. In the c.s.f. the corresponding values were 112 ± 2 m
M‐Na+ and 1·9 ± 0·1 m
M‐K+.

3. By keeping animals in K+‐rich water it was possible to raise chronically the concentrations of K+ in the blood plasma up to almost 5 times the normal value, close to 9 m
M, while the c.s.f. concentration of K+ was only doubled, to about 4 m
M. This behaviour of Necturus, tending to keep the K+ in the c.s.f. low, resembles that of mammals.

4. The membrane potential of glial cells in the optic nerve can be used as an accurate indicator for determining the K+ concentration in the intercellular spaces. Such determinations were made in vivo, and it was shown that the glial cells adjust their membrane potential to the changes of K+ concentrations in the c.s.f. and not to those of the blood plasma. In contrast, the membrane potential of skeletal muscle fibres changes according to the K+ concentration in the blood plasma.

5. It is concluded that the cells within the optic nerve are surrounded by an ionic environment which corresponds to that of the c.s.f. and not to that of the blood plasma. The intercellular spaces are open and ions diffuse freely into them from the c.s.f. A homeostatic mechanism operates, keeping the ion concentrations around neurones and glia within a narrow range and relatively independent of large changes in the blood plasma. This may provide relative stability for the signalling system. Similarities between the optic nerve and other parts of the central nervous system in respect to their relation to c.s.f. and blood are discussed. It seems likely that the mechanisms which control the electrolyte concentrations are similar in Necturus and in mammals.
Diffusional resistance of the innermost layer of the placental barrier of the rabbit
Authors: Faber J. Job , Hart Frederick M. , Poutala Arnold C.
Published: December 2014

1. The permeability of the endothelial cell layer of the foetal capillaries of the rabbit placenta was measured by the tracer‐dilution method. Isotopically labelled water, urea, chloride and sodium ions, and inulin were used. Radio‐iodinated human serum albumin served as reference tracer. The measurements were made in in situ placentas of 27‐29 days gestation of which the foetal circulation was perfused with homologous blood.

2. The permeability of water was found to be 1·7 ml. min−1.g−1, the permeabilities of urea, chloride ions and sodium ions were in the range of 0·28‐0·42 ml. min−1.g−1 and the permeability of inulin was 0·053 ml. min−1.g−1. These values may be underestimates, particularly the value of water.

3. The approximate maternal blood space, foetal blood space, and extravascular sodium space were determined in rabbit placentas of 27‐29 days gestation and found to be 0·16, 0·07, and 0·48 ml./g respectively.

4. The permeabilities of the endothelial layer were compared to those published for the entire placenta and found to be far greater. The resistance to diffusion of the endothelial layer is only a small part of the total resistance to diffusion. Most of the resistance is localized in the syncytioand/or cellular trophoblasts.

5. It was concluded that lipid insoluble molecules diffuse through the interstitial water spaces of the trophoblast in few, relatively wide channels but that diffusing water can make use of intracellular as well as extracellular paths.
The effect of infusions of plasma and of saline on the renal response to water‐loading in sodium‐depleted dogs
Authors: Coxon R. V. , Ramsay D. J.
Published: December 2014

1. Infusion of 150 ml. of plasma to dogs acutely depleted of sodium chloride by peritoneal dialysis with glucose (5 g/100 ml.) does not restore their ability to respond by diuresis when given 2·5% body weight of water by mouth.

2. Infusion of 300 ml. of saline (0·73g NaCl/100 ml.) to these animals results in a brisk increase in urinary flow.

3. Infusion of 100 ml. of saline (0·73g NaCl/100 ml.) to sodium‐depleted dogs restores their ability to respond to a water‐load of 2·5% of body weight by diuresis.

4. The results are discussed and a tentative explanation put forward.
Electrical activity observed in guinea‐pig olfactory cortex maintained in vitro
Authors: Richards C. D. , Sercombe R.
Published: December 2014

1. Electrical recordings were made from a preparation of guinea‐pig olfactory cortex maintained in vitro.

2. The response of the prepiriform area to a volley delivered to the lateral olfactory tract comprised a sharp negative deflexion upon which several positive notches were superimposed followed by a long‐duration low‐amplitude positive wave.

3. Both the negative and positive waves were of maximal amplitude near the top surface of the preparation (the original cortical surface).

4. Units recorded at depths of 250‐350 μ showed facilitation and latency variation. The latency distribution of these spikes was very similar to that of the positive notches observed on the surface of the slice.

5. The surface observed negative waves were rapidly abolished by oxygen lack.

6. The negative and positive waves have been tentatively identified as the extracellular manifestations of the excitatory post‐synaptic potentials (EPSPs) and inhibitory post‐synaptic potentials (IPSPs) occurring in the apical dendrites.

7. Some spontaneous activity was observed in a proportion of the preparations studied.

8. The evidence presented here strongly supports the contention that portions of the mammalian brain may be maintained in a satisfactory functional condition when isolated from the body, provided that they are maintained in a suitable environment. We believe that such preparations will prove very useful for physiological studies of the mammalian brain.
Effects of nerve cross‐union on fast‐twitch and slow‐graded muscle fibres in the toad
Authors: Close R. , Hoh J. F. Y.
Published: December 2014

1. A method is described for resolving isometric tetanic tension developed by fast‐twitch and slow‐graded components of heterogeneous toad muscles. This makes use of the difference in threshold for excitation of low threshold nerve fibres which normally innervate the fast‐twitch muscle fibres and high threshold nerve fibres which innervate slow‐graded muscle fibres.

2. The sartorius muscle contains only fast‐twitch muscle fibres whereas the posterior semitendinosus (PST) contains both fast‐twitch and slow‐graded muscle fibres, the latter contributing 10‐15% of the maximum isometric tetanic tension.

3. Following surgical cross‐union of nerve to sartorius and PST muscles, both the fast‐twitch and slow‐graded muscle fibre components of the PST are reinnervated by low threshold nerves originally innervating sartorius fast‐twitch fibres, and sartorius fast‐twitch muscle fibres are reinnervated by both low threshold and high threshold nerves formerly supplying the fast‐twitch and slow‐graded muscle fibre components of the PST.

4. The characteristic mechanical responses of fast‐twitch muscle fibres and slow‐graded muscle fibres were not transformed up to 134 and 200 days respectively following nerve cross‐union.

5. PST nerve partially innervated the sartorius muscle whereas sartorius nerves completely innervated the PST muscle. Isometric tetanic tension declined markedly during repetitive indirect stimulation of cross‐innervated sartorius muscles, whereas the tetanic contractions of cross‐innervated PST showed a plateau of tension and resembled the response of normal muscles.

6. Normal, cross‐innervated and self‐innervated PST muscles gave sustained contractures in the presence of acetylcholine whereas PST muscles denervated for 120 days gave phasic contractures similar to those of normal, cross‐innervated and self‐innervated sartorius muscles.
Conduction velocity in proximal and distal portions of forelimb axons in the baboon
Authors: Clough J. F. M. , Kernell D. , Phillips C. G.
Published: December 2014

1. Peripheral nerves of the baboon's forelimb were stimulated at different sites, and the latencies of antidromic action potentials were measured in intracellular records from forelimb motoneurones.

2. The conduction velocity of single motor axons was slower in the brachial plexus than in the nerves of the arm and forearm. This proximal slowing of conduction velocity was more marked for rapidly conducting axons than for the more slowly conducting ones.

3. Gross recordings from dorsal and ventral roots showed that the conduction velocity was slower in the brachial plexus than in the arm for fast afferent as well as efferent nerve fibres.

4. The proximal slowing of conduction velocity was shown to be due neither to errors of measurement nor to proximo‐distal differences of temperature.
Motor innervation, motor unit organization and afferent innervation of m. extensor digitorum communis of the baboon's forearm
Authors: Eccles Rosamond M. , Phillips C. G. , Chien-Ping Wu
Published: December 2014

1. One hundred and fifty efferent axons innervating m. extensor digitorum communis (EDC) were isolated in filaments of C7 and C8 ventral roots of baboons. Conduction velocities were measured antidromically by stimulating the muscle nerve and recording from the filaments, and fell into two groups: a fast (49‐84 m/sec) and a slow (22‐41m/sec), presumably fusimotor group. The threshold for these latter axons exceeded the strength needed to elicit the maximal motor twitch.

2. Stimulation of ventral root filaments containing slow axons produced no contractile tension in EDC.

3. Stimulation of ventral root filaments containing fast‐group axons elicited all‐or‐nothing twitches of motor units of EDC. The twitch tensions of 66·3% of the units were < 2·0 g wt.; only 8·7% were > 5·0 g wt. Tetanus‐twitch ratios were 1·4‐4·7 in a sample of 14 units. Contraction times were between 15 and 35 msec in 97% of the units. There was no correlation between contractile properties and axonal conduction velocity.

4. Afferent volleys from the stimulated EDC nerve were recorded from C6 or C7 dorsal roots. The threshold was below the threshold for a just‐detectable motor twitch in ten out of eleven baboons. Conduction velocity of the earliest component of the muscle afferent volley was 67‐83 m/sec.

5. The conduction velocities of twenty‐eight spindle afferents, identified by their responses to linear stretches of EDC and by their unloading by maximal twitches, were all < 70 m/sec. Higher dynamic sensitivity tended to be associated with higher conduction velocity.
Interaction between sodium and calcium ions in the process of transmitter release at the neuromuscular junction
Authors: Colomo F. , Rahamimoff R.
Published: December 2014

1. The interaction between Na and Ca ions on quantal transmitter release at the frog neuromuscular junction has been studied, using intracellular recording and averaging of responses.

2. At low calcium concentrations, partial withdrawal of Na ions increases end‐plate potential (e.p.p.) amplitudes and quantal content (m) and decreases the amplitude of the miniature e.p.p.s (m.e.p.p.s). Under these conditions the relation between [Ca] and m is highly non‐linear. When plotted on double logarithmic co‐ordinates withdrawal of [Na] causes a nearly parallel shift of this relation.

3. Mutual interaction occurs between Ca, Na and Mg in transmitter release. With a constant low [Ca] in the medium, withdrawal of [Na] produces a smaller increase in m when [Mg] is high, than when [Mg] is low.

4. In the presence of normal [Ca] (1·8 m
M), [Na] withdrawal decreases the amplitude of the e.p.p. and produces a small decrease in m.

5. The results can be explained by assuming that [Na] reduction has two mutually opposing effects on transmitter release: it makes more sites available for the action of Ca, and it lowers the amplitude of the action potential in the nerve terminals. The former effect dominates at low, the latter at high, calcium concentrations.
Changes in plasma glucose, lactate and free fatty acids in lambs during summit metabolism and treatment with catecholamines
Authors: Alexander G. , Mills S. C. , Scott T. W.
Published: December 2014

1. Exposure to cold increased the plasma levels of glucose and lactate in young lambs (< 1‐63 days old). Free fatty acid concentrations also increased, the increase being much greater in lambs older than 20 days.

2. Intravenous infusions of adrenaline and noradrenaline into lambs under a neutral thermal environment caused large increases in plasma glucose, lactate and free fatty acids.

3. Adrenaline and noradrenaline infusions increased the concentration of palmitic, stearic and oleic acids in the plasma of young lambs.

4. Treatment of lambs in summit metabolism with either α‐ or β‐adrenergic blocking agents (phentolamine or propranolol, respectively) caused the plasma levels of free fatty acids to fall. Phentolamine hydrochloride decreased the concentration of plasma glucose, but did not change the lactate level. In contrast, propranolol decreased the concentration of both of these metabolites in a significant proportion of the experiments.

5. Induction of muscular paralysis by suxamethonium chloride, in lambs exposed to cold, resulted in a rise in plasma free fatty acids, and a fall in glucose and lactate levels.

6. These observations suggest that the circulating level of plasma metabolites in young lambs is not the limiting factor in the metabolic response to cold exposure.
Interdependence of albumin and sodium transport in the foetal and new‐born pig intestine
Authors: Brown Pat , Smith M. W. , Witty R.
Published: December 2014

1. Everted sacs of new‐born pig intestines incubated in bicarbonate saline at 37° C, transferred bovine plasma albumin across the mucosa into fluid bathing the serosa, the amount transferred increasing as the concentration of albumin in the mucosal fluid was raised from 0·5 to 16 g/100 ml.

2. The rate of albumin transfer across the foetal pig intestine showed an apparent maximum, about 400 μg/g intestine/hr, 2 weeks before birth. The transfer at birth, about 200 μg/g intestine/hr, fell sharply during the next 2 days but later returned to that previously found at birth.

3. When sacs were prepared from the intestines of 1 to 7‐day‐old pigs part of the recovered albumin was degraded. No digestion was found when the intestines of new‐born or foetal pigs were used.

4. The transfer of water and sodium, but not glucose, measured across the foetal and new‐born pig intestine, was consistently higher when albumin was present in the mucosal fluid: the transmural potential difference was lowered by the presence of albumin. These differences disappeared during the first 2 days of life.

5. Both the total and ouabain‐sensitive adenosine triphosphatase (ATPase) activities of the pig intestinal epithelium fell within 24 hr of birth. There was some increase in total ATPase activity in older pigs but the ouabain‐sensitive activity remained low.

6. The relation between albumin and sodium transport, seen at a time when albumin is not being metabolized, suggests that the transfers are closely coupled. The movement of sodium into a mucosal cell down its own concentration gradient may provide energy for the translocation of albumin.
A preparation of perfused small intestine for the study of absorption in amphibia
Authors: Parsons D. S. , Prichard J. S.
Published: December 2014

1. A preparation of amphibian small intestine perfused through its vascular system is described. Vascular perfusion with a bicarbonate Ringer solution containing a colloid is used to control the composition of the environment of the submucosal faces of the absorbing cells and to carry away for collection any material extruded from these cells. Oxygenation of the mucosal cells is derived primarily from fluid circulated through the intestinal lumen. The preparation exhibits physiological properties of transport for periods of up to 5 hr. After 5 hr perfusion the epithelial cells show no signs of gross cellular damage when examined either by light or by electron microscopy.

2. The relationship between the hydrostatic pressure at the mesenteric artery and the rate of perfusion through the vascular bed is substantially linear. The pressure—flow relationships in the mesenteric bed, including an apparent ‘critical closing pressure’, are primarily determined by the hydrostatic pressure in the intestinal lumen. Alterations in the hydrostatic pressure in the intestinal lumen also change the relative proportions of the vascular infusate which appear in the portal venous effluent and in the fluid exuded from the serosal surface of the preparation (‘sweat’). Hydrostatic distension pressures above about 10 cm H2O reduce the rate of collection of fluid from the portal vein and increase the rate of collection of ‘sweat’.

3. An increase in the rate of vascular perfusion increases the total rate of glucose appearance although the glucose concentrations in both the portal effluent and the ‘sweat’ are reduced.

4. The glucose translocation rate is related in an alinear saturable fashion to the luminal concentration of glucose. By making a correction for metabolic loss of glucose during its passage through the intestinal cell, the relationship existing between the lumen concentration and the uptake of the sugar by the mucosal cells has been calculated. This relationship is found to fit Michaelis—Menten type kinetics. The Km of the intestinal translocation process for glucose in Rana pipiens was 0·45 ± 0·13 (4) μ
M. The mean Vmax was 137·5 ± 35·3 (4) μ
M/hr/g fat‐free dry wt.

5. When phlorrhizin (10−5
M) is added to the vascular perfusate, no inhibition of glucose transport is seen for at least 60 min. When strophanthin is added to the vascular perfusate (5 × 10−5
M), a markedly greater inhibition of glucose transport is observed than when it is introduced to the luminal circulation.

6. Earlier studies of the vascular perfusion of isolated small intestine are tabulated. The experimental findings are discussed in relation to a model of the mode of action of the epithelial cell for glucose transport.
Absorption of histamine from the gastrointestinal tract of dogs in vivo
Authors: Duncan Jessie G. C. , Waton N. G.
Published: December 2014

1. In anaesthetized dogs, various amounts of [14C]histamine were introduced into the lumen of a ligated intestinal loop or of the ligated stomach and the absorption of this histamine was studied by determining the radioactive histamine in the venous blood coming from the ligated part.

2. After the introduction of 5‐5000 μg [14C]histamine, into a loop of jejunum, or of 50 μg into a loop of duodenum, ileum or colon, radioactive histamine was detected in all eight successive 15 min samples of venous blood collected during 2 hr. The percentage recovery of the [14C]histamine in the blood during this period varied between 0·04 and 3·7.

3. After the introduction of 10 mg [14C]histamine into the stomach, radioactive histamine was detected in all samples of gastric venous blood collected at various times during the following 4 hr.

4. After the introduction of 50‐5000 μg [14C]histamine into a loop of jejunum, radioactive histamine was also detected in the general arterial blood.

5. When a jejunal loop was perfused through its artery with a dextransaline solution, the absorption of [14C]histamine from the lumen into the venous effluent was much greater than when the blood supply was kept intact.

6. A large part of the [14C]histamine introduced into an intestinal loop was inactivated or destroyed either in the lumen or the wall since only a part was recovered in the venous blood, contents and wall of the loop at the end of 2 hr. When different amounts of [14C]histamine were introduced into a jejunal loop the recovery was shown to be dependent on the dose. With 5 μg it amounted to about 1% whereas with 5000 μg to 29‐42%. The recovery of the [14C]histamine introduced into a perfused jejunal loop was greater.

7. In dogs and cats large amounts of free histamine were found in the contents of the stomach 2 hr after a meat meal, and much smaller amounts in the contents of loops from the small intestine. The amounts found in the contents of loops from the colon varied greatly.

8. In eighteen commercial dog and cat foods the free histamine contents were found to vary over fiftyfold, from 0·06 to 3·5 mg/100 g.

9. The significance of the results is discussed in relation to the role of histamine as a humoral agent in the ‘gastric’ and ‘intestinal phases’ of gastric secretion.
Visual adaptation of the rhodopsin rods in the frog's retina
Authors: Donner K. O. , Reuter Tom
Published: December 2014

1. The threshold of the discharge from single ganglion cells in the excised and opened frog's eye has been measured with on/off stimuli and test parameters that make it possible to activate the rhodopsin rods only. The test stimuli have been restricted to the central part of the receptive field, where no nervous reorganization can be observed with changes in the state of adaptation.

2. When such thresholds and the intensities of the background lights are expressed in terms of the number of quanta absorbed per unit time, it is found that three factors can be correlated with the thresholds measured in various states of light‐ and dark‐adaptation: (i) the intensity of a steady background, (ii) the rate of regeneration of rhodopsin, and (iii) the amount of metarhodopsin II present in the rods.

3. The threshold is found to be proportional both to the intensity of a background and to the rate of regeneration, whereas there is a linear relationship between the logarithm of the threshold and the amount of metarhodopsin II.

4. The presence of metarhodopsin elevates all thresholds, the absolute threshold, increment thresholds and the thresholds elevated by regenerating rhodopsin in the same way.

5. The saturation of the rods at high background intensities is found to be correlated with the accumulation of significant amounts of metarhodopsin in the rods, caused by the bleaching effect of the background.

6. The effect of metarhodopsin on the threshold is independent of the amount of rhodopsin present in the rods.

7. The combined effect of all three factors can be expressed in a general formula, given as eqn. (7) on p. 74.

8. A background not only reduces the signals from the rods illuminated, but also those from neighbouring unilluminated rods. This effect is rapidly decreased with increasing distance from rods covered by the background. This kind of lateral spread in the retina probably occurs also when the rate of regeneration affects the threshold. The effect of metarhodopsin, on the other hand, appears restricted to those receptors that contain this substance.
Miniature synaptic potentials at frog spinal neurones in the presence of tetrodotoxin
Authors: Colomo F. , Erulkar S. D.
Published: December 2014

1. Spontaneous subthreshold potentials have been recorded with an intracellular electrode from neurones of the isolated spinal cord of the frog.

2. Records of both depolarizing and hyperpolarizing potentials were obtained from cells in normal Ringer solution and also when impulse conduction in the cord had been abolished by tetrodotoxin (TTX).

3. Comparisons of results before and after TTX show that the majority of the spontaneous potentials are analogous to miniature end‐plate potentials.
Multiple sensitivity of chorda tympani fibres of the rat and hamster to gustatory and thermal stimuli
Authors: Ogawa H. , Sato M. , Yamashita S.
Published: December 2014

1. Impulse discharges in single chorda tympani fibres of rats and hamsters in response to gustatory stimuli representing the four basic qualities of taste as well as to cooling and warming of the tongue were recorded.

2. In both rats and hamsters many fibres responded to more than one kind of gustatory stimulus as well as to thermal ones. The thermal sensitivity of these fibres was found to be about ‐0·5 impulses/sec. °C for cooling and 0·5 impulses/sec. °C for warming.

3. Statistical calculations of the frequency of responses of chorda tympani fibres to single gustatory stimuli or combinations of stimuli were made, assuming that responsiveness to any one stimulus is independent of that to other stimuli. Evidence for relatively specific sensitivity to a particular stimulus or a particular combination of stimuli was obtained in the rat and the hamster.

4. Across‐fibre correlation coefficients between the amounts of responses to a pair of stimuli were calculated. In both the rat and the hamster, significant positive correlations were obtained with HCl, quinine and cooling. In addition, a positive correlation between sucrose and warming and a negative correlation between sucrose and NaCl were obtained in the hamster. The results are discussed in relation to the interaction of gustatory and thermal sensations of the human tongue.
Sodium and calcium components of action potentials in Aplysia giant neurone
Authors: Geduldig D. , Junge D.
Published: December 2014

1. Action potentials resulting from direct stimulation can be recorded from the soma of the Aplysia giant neurone (located in the visceral ganglion) in sodium‐free and in calcium‐free external solutions. The neurones were impaled by internal micro‐electrodes throughout the change of external solutions.

2. Complete replacement of either sodium or calcium in the bathing medium with Tris results in only a partial reduction of spike overshoot. Simultaneous replacement of both sodium and calcium reversibly and quickly abolishes the spike.

3. The sodium component of the spike in a calcium‐free medium is blocked by tetrodotoxin; the drug has no effect on the calcium‐dependent spike in sodium‐free medium. Externally applied cobalt chloride blocks only the calcium‐dependent component.

4. In calcium‐free media, the overshoot value varies with sodium concentration in the manner predicted for a sodium electrode. In sodium‐free media, the membrane behaves like a calcium electrode.

5. These results suggest that, during the normal action potential, both sodium and calcium act as carriers of the inward‐directed current.