bluuebunny/crossref_metadata_2025 huggingface dataset:
The calcium content of human erythrocytes
Authors: Harrison D. G. , Long C.
Published: December 2014

1. The calcium content of human erythrocytes, after removal of the buffy coat and washing free from plasma with isotonic sodium chloride, has been determined by atomic absorption spectrophotometry. The mean value found for normal subjects was 0·634 μg/ml. of packed erythrocytes (0·0158 μg‐atom/ml.). The corresponding values for magnesium and zinc were 79·7 and 20·1 μg/ml., respectively.

2. The calcium is considered to be mostly and perhaps exclusively located in the erythrocyte membrane, since, after osmotic haemolysis, the same amount was found in the ghost cells as was present in the erythrocytes from which they were prepared. By contrast, magnesium and zinc, which are essentially intracellular, were lost to the extent of about 96 and 92%, respectively.

3. About 90% of the calcium was removed from erythrocytes by washing with isotonic sodium chloride containing 5 m
M ethylenediaminetetraacetate (EDTA), or other complexing agents of high stability constant for calcium. A small fraction of the magnesium but none of the zinc was removed by this treatment.

4. Other complexing agents of lower stability constant removed somewhat less calcium from the erythrocytes. Citrate was totally ineffective.

5. The buffy coat had a high calcium content, but this could not be removed by washing with EDTA.

6. Calcium was also determined in trichloroacetic acid extracts of ghost cells after ashing and treatment with bis‐(o‐hydroxyphenylimino)‐ethane and measuring the red complex spectrophotometrically. The values obtained confirmed the atomic absorption measurements.
post‐synaptic excitation and inhibition from primary afferents in neurones of the spinocervical tract
Authors: Hongo T. , Jankowska Elżbieta , Lundberg A.
Published: December 2014

1. Intra‐ and extracellular recordings were made from cells of the spinocervical tract in the lumbosacral spinal cord. A convergence of monosynaptic excitatory post‐synaptic potentials (EPSPs) and disynaptic inhibitory post‐synaptic potentials (IPSPs) was a general pattern of effects from the low threshold cutaneous fibres. Unitary IPSPs, probably mediated via the same disynaptic path, were evoked by light touch of hairs, which was also the adequate stimulus for exciting the cells. The receptive field for unitary IPSPs was closely related to the excitatory receptive field but was eccentric, not of a surround type.

2. EPSPs, IPSPs, or both, were evoked from the flexor reflex afferents in the great majority of neurones. Disynaptic IPSPs may be evoked from the interosseous nerve. No effects were produced by volleys in group I muscle afferents.

3. It is suggested, on the basis of the spatial organization of the excitatory and inhibitory receptive skin fields, that the spinocervical tract may give information regarding the direction of tactile stimuli.
The effect of cyanide on the efflux of calcium from squid axons
Authors: Blaustein M. P. , Hodgkin A. L.
Published: December 2014

1. The average rate constant for loss of 45Ca from an unpoisoned squid axon was 1·8 × 10−3 min−1, corresponding to an efflux of 0·2 p‐mole/cm2 sec.

2. The Ca efflux from unpoisoned axons was reduced if external calcium was replaced with magnesium, or external sodium with lithium, choline or dextrose. Replacing both sodium and calcium reduced the efflux to about 40%.

3. Cyanide caused little immediate change in Ca efflux but after 1½‐2½ hr the efflux increased to 5‐15 times its normal value. The effect was rapidly reversed when cyanide was removed.

4. The large Ca efflux into cyanide was reduced by a factor of three when external calcium was replaced with magnesium and by a further factor of about six when external sodium was replaced with lithium.

5. The Ca efflux from both poisoned and unpoisoned axons had a Q10 of 2‐3, was not affected by ouabain and was greatly reduced by injecting ethyleneglycol bis (aminoethylether)‐N,N′‐tetra‐acetic acid (EGTA).

6. After injecting 45Ca along the axis, the efflux of calcium reached its maximum much more rapidly in a cyanide‐treated axon than in an unpoisoned axon.

7. Pre‐treatment with cyanide greatly increased the rate at which calcium was lost from axoplasm extruded into flattened dialysis bags. A similar effect was observed when cyanide was applied after extrusion.

8. Replacing external sodium glutamate with potassium glutamate greatly reduced the loss of 45Ca from intact axons poisoned with cyanide but had little effect on the loss from extruded axoplasm.

9. The rate constant for loss of the Ca EGTA complex was about 3 × 10−5 min−1 for intact axons and 2 × 10−2 min−1 for extruded axoplasm.

10. A possible explanation of the cyanide effect is that, after poisoning, calcium ions are released from a store and can then exchange at a higher rate with external sodium or calcium.

11. The experiments suggest that part of the calcium efflux may be coupled to sodium entry.

12. Theoretical equations for ‘diffusion and chemical reaction in a cylinder’ are described in the Appendix.
A study of the mechanism of water transfer across frog skin by a comparison of the permeability of the skin to deuterated and tritiated water
Authors: King Venetia
Published: December 2014

1. Frog abdominal skins were placed between the two half‐cells of a modified version of Ussing's frog skin apparatus.

2. The rate of equilibration of deuterated and tritiated water across the skin was followed at pH 5·0, 6·9, and 8·0 with Ringer solution bathing both surfaces of the skin; and at pH 7·0 with sulphate Ringer solution bathing both surfaces of the skin.

3. The ratio of the permeability coefficients for the influx of deuterated and tritiated water had a mean value over all the experiments of 0·9954 ± 0·0207, n = 27, indicating that no isotope effect was observable within the limits of accuracy of the experimental method.

4. The thickness of the unstirred layers associated with the frog skin was measured, and, from the data obtained, values of the true permeability coefficients for each isotope were calculated.
The sensitivity of muscle spindle afferents to small sinusoidal changes of length
Authors: Matthews P. B. C. , Stein R. B.
Published: December 2014

1. Nerve impulses were recorded from spindle afferents of the soleus muscle during sinusoidal changes in muscle length at frequencies from 0·03 to 300 c/s. This was done in the decerebrate cat with intact motor outflow and ‘spontaneous’ fusimotor activity. Computer averaging over a number of cycles was used to measure the response, in impulses/sec, at different phases of the cycle.

2. A linear range was described in which the discharges of the endings were approximately sinusoidally modulated, and in which increasing the amplitude of the stretching produced a proportional increase in the response. At 1 c/s the linear range extended up to only about 0·1 mm for primary endings, but was greater than 1 mm for secondary endings.

3. The sensitivity of an ending in its linear range was defined as the amplitude of its response divided by the amplitude of the length change. The sensitivity of both primary and secondary endings increased progressively on increasing the frequency of stretching above 1 c/s. The experimental observations relating the sensitivity to the sinusoidal frequency were fitted over much of the range by a curve given by the vector sum of components proportional to the length and to the velocity of stretching. This curve has two parameters, a sensitivity at low frequencies (S), and a corner frequency (F) at which the length and velocity contributions are equal. The value of F was about 1·5 c/s for both primary and secondary muscle spindle endings. The value of S was very much greater for primary endings (median value 95 impulses/sec/mm) than for secondary endings (median value 7 impulses/sec/mm). The increasing sensitivity of the endings at higher frequencies caused a progressive reduction in the linear range when it was expressed as an amplitude of stretching, but it remained approximately constant when it was expressed as a modulation of the frequency of discharge.

4. The primary endings were also extremely sensitive to maintained changes in length provided they were of sufficiently small amplitude.

5. In the presence of fusimotor activity a high sensitivity of small changes was found over a wide range of muscle lengths. De‐efferented endings had a comparable high sensitivity when the muscle was at or beyond physiological full extension, but not when the muscle was shorter.

6. The results are contrasted with those obtained previously using stretches of large amplitude, and the physiological significance of the high sensitivity of primary endings to small stretches is discussed in relation to the reflex control of movement.
The site of action of calcium in producing contraction in striated muscle
Authors: Gillis J. M.
Published: December 2014

1. Contraction of glycerinated crab myofibrils, suspended in a relaxing medium containing Mg‐ATP and EGTA, was induced by iontophoretic application of Ca ions through a micropipette. Contraction was observed by phase‐contrast microscopy.

2. The large size of the sarcomere (10‐15 μ) in the crab Cancer allowed applications of Ca ions at several discrete points along a single sarcomere.

3. The threshold iontophoretic current needed to produce just visible contraction was measured for each position of the micropipette along the sarcomere. It was always lowest at the A—I junction.

4. When Ca was delivered to the I band, the threshold current increased with the distance of the pipette from the A—I junction. Along the A band, the results depended on the sarcomere length: for short sarcomere lengths, the threshold current remained roughly constant over a large part of the A band; for long sarcomeres, it increased with the distance from the A—I junction in the same manner as in the case of the I band.

5. As Ca reached the fibril by diffusion from the micropipette, the influence of the diffusion path on the threshold current was investigated.

6. The length of the region of overlap of the thick and thin filaments in the A band was estimated by electron microscopy.

7. The results demonstrate that, in order to produce contraction, Ca has to reach the region of overlap of the myofilaments.
The relation between the 5‐hydroxytryptamine content and aggregation of rabbit platelets
Authors: Baumgartner H. R. , Born G. V. R.
Published: December 2014

1. Blood platelets containing different amounts of 5‐hydroxytryptamine (5–HT) were produced in vivo by the injection of 5‐hydroxytryptamine or of reserpine into normal rabbits and of 5‐hydroxytryptamine into reserpinized rabbits. Before and after these injections the aggregation of platelets was measured in vitro.

2. Platelets of untreated rabbits were aggregated by adenosine diphosphate (ADP) and by 5‐hydroxytryptamine; (—)‐adrenaline alone did not produce aggregation but markedly increased aggregation by 5‐hydroxytryptamine.

3. Platelets saturated with 5‐hydroxytryptamine in vivo were no longer aggregated in vitro by 5‐hydroxytryptamine or by 5‐hydroxytryptamine plus adrenaline, but their aggregation by ADP was unchanged.

4. Platelets from reserpinized rabbits lost about 99% of their 5‐hydroxytryptamine; the aggregation of these platelets did not differ significantly from that of platelets from control rabbits.

5. Platelets from reserpinized rabbits injected with 5‐hydroxytryptamine were aggregated neither by the amine alone nor by 5‐hydroxytryptamine plus adrenaline, although these platelets contained much less 5‐hydroxytryptamine than saturated platelets and only about one tenth as much as platelets from untreated rabbits.

6. The findings support the hypothesis that the inhibitory effect of 5‐hydroxytryptamine administered in vivo on platelet aggregation in vitro is due to the association of the amine with the platelet membrane.
The relation of membrane changes to contraction in twitch muscle fibres
Authors: Heistracher P. , Hunt C. C.
Published: December 2014

1. Contractile responses in short twitch‐type snake muscle fibres have been studied. These fibres are sufficiently short to allow fairly uniform changes in membrane potential along their length when current is passed through an intracellular micropipette. Active sodium permeability changes were blocked with tetrodotoxin (TTX), procaine, or by using solutions low in sodium. Current and voltage micropipettes were used to voltage‐clamp these fibres. Depolarization steps to about −40 mV evoked contractile responses, maximal tension being developed between −10 and 0 mV. The relation between contraction and membrane potential was sigmoid.

2. Depolarization beyond a critical threshold produced an increment of outward current which inactivated with time. The threshold for this delayed rectification was normally similar to the threshold for contractile activation. Fibres exposed to high potassium showed a reversal of this inactivating current to slightly super‐threshold depolarizing pulses. At membrane potentials near 0 mV, no inactivating current was noted, while stronger depolarizing pulses produced an inactivating current in the normal direction. Fibres in high potassium show the same threshold for initiation of contraction as in normal solution.

3. Thiocyanate, nitrate, and caffeine shifted the relation between membrane potential and contraction toward higher levels of membrane potential. The threshold for inactivating rectifying current failed to shift to a corresponding extent, although some shift in rectification which did not inactivate was evident.

4. When depolarization was maintained, contractile tension was maximal for several seconds, then gradually disappeared. The rate of this contractile inactivation depended upon the level of depolarization.
The effects of age and environmental temperature on the blood concentrations of glucose, free fatty acids and glycerol in new‐born rabbits
Authors: Hardman M. J. , Hull D.
Published: December 2014

1. The concentration of blood glucose, free fatty acids and serum glycerol of the doe, new‐born and young rabbits have been measured in order to evaluate the effects of age, starvation and environmental temperature on the circulating concentrations of these metabolites.

2. The blood glucose, free fatty acid and glycerol concentrations were lower in the new‐born than in the mother rabbit.

3. Starvation for 24 hr of new‐born and young rabbits in a thermal neutral environment did not alter the serum free fatty acid or glycerol concentrations. The blood glucose of unfed rabbits fell during the first 24 hr of life.

4. Cold exposure (15 or 25° C) for 1 hr caused a rise in the concentration of blood glucose, serum free fatty acids and glycerol.

5. When the metabolic response of new‐born and young rabbits to cold exposure was measured, it was found that there was a direct correlation between the serum glycerol concentration and the metabolic response. The greatest rise in the serum free fatty acids occurred in the blood of rabbits with the poorest metabolic response to cold.

6. It is suggested that in the steady state during cold exposure the serum glycerol concentration may indicate the rate of triglyceride hydrolysis in brown adipose tissue.
Types of nervous activity which may be recorded from the carotid sinus nerve in the sheep foetus
Authors: Biscoe T. J. , Purves M. J. , Sampson S. R.
Published: December 2014

1. In the sinus nerve of mature foetal sheep (120–147 days gestational age) three types of nerve activity have been demonstrated: (a) baroreceptor afferent, in which the nerve activity was synchronous with the pulse pressure wave and which followed pressure changes in the carotid sinus including those caused by compressing the umbilical cord. The discharge of nine out of twelve baroreceptor afferents increased with sympathetic stimulation, (b) a subtype of (a) in which there was irregular activity from pressure receptors which most probably represented baroreceptors discharging at or about threshold, and (c) in the older foetuses (130–147 days), there was activity which was unaffected by changes in carotid sinus pressure, Pa, O2 or NaCN but which increased in discharge rate with compression of the umbilical cord or with stimulation of the cervical sympathetic; this activity then increased with injection of NaCN and was thus identified as chemoreceptor in origin. In addition, a pathway originating in the cervical sympathetic and which passed through the superior cervical ganglion was demonstrated by evoking a compound action potential on stimulation of the preganglionic cervical sympathetic nerve.

2. Recordings from pre‐ or post‐ganglionic cervical sympathetic nerves showed that spontaneous activity was present and increased when the umbilical cord was compressed.

3. These results suggest that the carotid body chemoreceptors in the foetus are relatively insensitive to chemical changes and that, in their activation at birth, the sympathetic could be involved. Possible neural pathways and the mechanism of activation are discussed.
The secretion of gastric acid in response to a lack of metabolizable glucose
Authors: Colin-Jones D. G. , Himsworth R. L.
Published: December 2014

1. The onset of the secretion of acid from the stomach of rats during insulin‐induced hypoglycaemia has been found to correspond to a mean plasma glucose concentration of 72 mg/100 ml. (equivalent to a blood glucose concentration of 44 mg/100 ml.).

2. Infusions of the non‐metabolizable sugar, 3‐O‐methylglucose, into rats with denervated adrenal glands caused a large and sustained rise in the gastric acid output. This gastric acid secretion could be prevented by prior vagotomy or stopped, when previously established, by cutting the vagi or by the administration of glucose.

3. A consistent relationship was demonstrated between the plasma concentration of glucose and the total concentration of glucoses (glucose plus 3‐O‐methylglucose) in the plasma at the onset of gastric acid secretion during the infusion of 3‐O‐methylglucose into these rats. The theoretical basis for this relationship is discussed.

4. 3‐O‐methylglucose did not cause the release of gastric acid when infused into rats with intact sympathetic nervous systems owing to the effects of the secretion of adrenaline provoked by this agent.

5. The qualitative and quantitative similarities between the factors governing both the secretion of gastric acid and the release of adrenaline in the absence of a sufficiency of metabolizable glucose are discussed. It is suggested that the reactions of both these systems under such circumstances are determined by chemoreceptors which possess identical characteristics.
The effect of ambient temperature upon post‐natal changes in oxygen consumption of the guinea‐pig
Authors: Adamsons K. , Blumberg E. , Joelsson I.
Published: December 2014

1. The effect of thermal environment and administration of progesterone upon minimal oxygen consumption and thermal stability of the new‐born guinea‐pig has been investigated.

2. It was found that the ambient temperature at which the new‐born is reared does not influence minimal oxygen consumption although it modifies the response to cold.

3. Thermal stability was decreased in animals raised in a warm environment.

4. Minimal oxygen consumption per unit body weight during the neonatal period increased 25%, most of the increase taking place within 16 hr after birth.

5. Decrease in the relative mass of brown adipose tissue was least in new‐borns maintained at a high ambient temperature.

6. Administration of progesterone did not affect oxygen consumption, body temperature and thermal stability of the new‐born.
Correlation between transmission and structure in avian ciliary ganglion synapses
Authors: Hess A. , Pilar G. , Weakly J. N.
Published: December 2014

1. Extracellular responses from post‐ganglionic axons of pigeon and chick isolated ciliary ganglia were elicited by stimulation of the presynaptic nerve. Intracellular recordings were also obtained from newly hatched pigeon and chick ganglion cells. The fine structure of ganglia from pigeons of various ages was examined with the electron microscope.

2. In ganglia from chick embryos and pigeons up to 10 days old, the extracellular response was unimodal with a long latency and could be blocked by the addition of
D‐tubocurarine (
D‐TC) or hexamethonium to the bathing solution. A bimodal extracellular response appeared in pigeons about 10 days after hatching. Only the second peak of the response could be blocked by
D‐TC or hexamethonium. The response recorded from 22 to 26‐day‐old pigeons was similar to that seen in the adult.

3. The intracellular recordings from ganglion cells of 2‐week‐old pigeons exhibit two post‐synaptic potentials elicited by presynaptic stimulation. The first post‐synaptic potential appears to be due to current flow through the ganglion cell during the presynaptic action potential. The second is chemically mediated. In pigeons from 1 to 6 days old, only the second post‐synaptic potential is observed.

4. The presynaptic terminals in the 4‐day‐old birds were in the form of calyces. In pigeons 7 days old or older, boutons appeared. The boutons were presumably formed as a result of cleavage of calyciform nerve terminals. Myelin was seen first in the 7‐day‐old pigeon, was well developed in the 16‐day‐old bird, and persisted in the adults.

5. In adult ganglia, the first component of the extracellular response decreased and was finally abolished after 10–12 hr of superfusion with Tyrode solution. The second component of the response increased concomitantly. The only anatomical change noted in the ganglia after soaking was the disruption and separation of the myelin lamellae from each other and from around the ganglion and presynaptic terminals.

6. It is concluded that the myelin is necessary for electrical transmission in the pigeon ciliary ganglion.
Impulse functions for human rod vision
Authors: Hallett P. E.
Published: December 2014

1. This paper presents accurate increment threshold data for human rod vision for a small number of experimental parameters. The test is small and brief and the large background is either steady or transient.

2. The linear threshold disturbance due to an impulse background consists of an input dependent exponential growth phase and an exponential recovery phase of more or less fixed time constant (ca. 0·08 sec).

3. The data are treated by applying signal/noise decision theory to a hypothetical filter with two shot noise inputs, viz. the testing signal and the background. The gain and time course of the impulse function of the filter are slightly affected by the magnitude of the input.

4. A linear approach is useful since the impulse functions for dark or light‐adapted rod vision yield independent information about quantities which have previously only been used to describe the increment thresholds for small tests on steady backgrounds, viz. the integration time and dark light of the fully dark‐adapted eye and the gain changes (or changes in the signal/background ratio) which occur on progressive light adaptation.
The permeation of non‐electrolytes through the single barnacle muscle cell
Authors: Bunch Wilton , Edwards Charles
Published: December 2014

The rate of movement of non‐electrolytes and tritiated water (THO) across the muscle cell membrane of the giant barnacle Balanus nubilus has been studied and permeability coefficient calculated. The rate of permeation is more closely related to the oil—water partition coefficient than to size of the molecule or degree of hydrogen bonding. Calculations based on efflux from an ideal cylinder suggest that the membrane acts as a significant barrier to movement of these molecules. The cell was unable to concentrate dimethyl sulphoxide (DMSO); the steady state was reached at about 60% of the extracellular concentration. The energies of activation for water, urea and DMSO are 7·5, 20·3 and 26·1 kcal/mol. At 4° C the apparent pore size measured with urea, glycerol and DMSO was 3·5 Å. At 25° C the apparent pore size for urea and glycerol is unchanged but that for DMSO is 14 Å.
A study of the parameters of electrical stimulation of unmyelinated fibres in the pituitary stalk
Authors: Harris G. W. , Manabe Y. , Ruf K. B.
Published: December 2014

1. The milk‐ejection response in lactating rabbits has been used to study the effect of electrical stimuli of different types applied to the supraopticohypophysial tract in the pituitary stalk.

2. Sine‐wave alternating‐current pulses were compared with balanced biphasic square‐wave pulses of the same frequency and peak‐to‐peak current strength. At a pulse duration of 2‐4 msec the square‐wave stimulation was less effective than the sine wave, but at a pulse duration of 8 msec and over, more effective.

3. Above threshold levels of 0·12 mA for the current strength, and of 0·5 msec for the pulse duration, the response increased with increasing current strengths to 2·4 mA and increasing pulse durations to 10 msec.

4. With constant and effective strength and duration of the pulse a slight diminution of the response was seen as the frequency was diminished from 100/sec to 50/sec. Further diminution in the frequency revealed that at some point between 50 and 10 c/s a sudden abrupt diminution in the magnitude of the responses occurred over a small range of frequency. This was a reversible phenomenon and it is suggested that it may be related to neurosecretory events occurring in the nerve terminals.

5. Stimuli with parameters within the ranges mentioned above are effective in eliciting an oxytocic response on the uterus in the rabbit and ovulation responses (when applied to the hypothalamus) in rats and rabbits. It appears likely that stimuli with such parameters are suitable for experiments concerned with stimulation of the hypothalamus.
Modulation of noradrenaline incorporation by nerve activities in the rat submaxillary gland
Authors: Chang C. C. , Chiueh C. C.
Published: December 2014

1. Rats were anaesthetized with chloralose and prepared for electrical stimulation of the cervical sympathetic trunk. The effect of such stimulation was studied on the incorporation of intravenously infused [3H]noradrenaline, [3H]adrenaline or [3H]dopamine by the submaxillary gland.

2. A train of 200 stimuli every min for 30 min at 20/sec increased the total incorporation of [3H]noradrenaline by 92% over the unstimulated side of the gland, at 50/sec by about 200% and at 3·3/sec by about 30%. The incorporation of [3H]adrenaline and of [3H]dopamine was also increased by sympathetic stimulation.

3. The increases in unaltered [3H]noradrenaline and its metabolites were proportional to the increase in total radioactivity.

4. Mean venous outflow from the gland was decreased by 15–30% by the sympathetic stimulation.

5. After elimination of extraneuronal binding of noradrenaline by ligation of the common excretory ducts, nerve stimulation still increased incorporation.

6. Inhibition of normetanephrine production by pyrogallol did not antagonize the nerve impulse‐mediated increase of [3H]noradrenaline incorporation. α‐Methyltyrosine was also without effect.

7. Desmethylimipramine and bretylium completely abolished the nerve impulse‐mediated increase of [3H]noradrenaline incorporation in concentrations which did not affect the control uptake or abolish adrenergic transmission.

8. Reserpine, guanethidine and phenoxybenzamine antagonized both the control and nerve impulse‐mediated incorporations of [3H]noradrenaline.

9. The results indicate that nerve impulses modulate the incorporation of transmitter amine at the neuronal membrane. Possible mechanisms for this modulation are discussed.
Changes in extracellular potassium concentration produced by neuronal activity in the central nervous system of the leech
Authors: Baylor D. A. , Nicholls J. G.
Published: December 2014

1. Experiments were made on single neurones and glial cells in the central nervous system of the leech to study the accumulation of K that occurs in the extracellular spaces around neurones as a result of impulse activity.

2. The resting potential of a neurone is too insensitive to be used for the estimation of small changes in K concentration. The undershoot of the action potential, however, provided a reliable indicator of the K accumulation that occurs around a neurone during activity.

3. After a single impluse the amplitude of the undershoot of a second action potential was decreased; the effect corresponded to a peak increase in K concentration of about 0·8 m
M/l. immediately after the spike and declined exponentially with a time constant of about 100 msec. With trains of impulses the K concentration increased exponentially, again with a time constant of about 100 msec. The final value of K depended on the frequency and could build up to about double the normal concentration of 4 m
M/l.

4. The build‐up of K was markedly reduced when the extracellular space surrounding a neurone was enlarged by removing its glial investment.

5. Synchronous, repetitive activation of groups of neurones caused a slow depolarization of neighbouring glial cells in the
C.N.S. of the leech, similar to that observed in amphibia and mammals. The change in glial membrane potential was also used to estimate the changes in K concentration and these values agreed with measurements derived from the undershoot.

6. Increases of K concentration in the bathing fluid of the same order as those caused by neural firing markedly affected the frequency of ‘spontaneous’ neuronal discharges and synaptic potentials occurring within certain neurones in the
C.N.S.

7. The possible effects of physiologically occurring increases of K concentration on integration are discussed.
Chemical and electrical synaptic connexions between cutaneous mechanoreceptor neurones in the central nervous system of the leech
Authors: Baylor D. A. , Nicholls J. G.
Published: December 2014

Experiments have been made to study the synaptic connexions between sensory cells in the
C.N.S. of the leech. Each segmental ganglion contains six neurones that respond specifically to light touch applied to the skin; each of these ‘touch cells’ innervates a discrete area on the surface of the body and has a characteristic set of properties by which it can be recognized. Using intracellular electrodes it has been shown that these sensory cells interact with one another through chemical and electrical synapses by way of a stereotyped set of pathways.

1. Action potentials occurring in one touch cell gave rise to synaptic potentials in the five other touch cells in the same ganglion and also in the three ipsilateral touch cells in the adjacent ganglia. Thus, synaptic interactions took place between sensory cells whose receptive fields lay within the same segment and on the same side of adjacent segments.

2. The post‐synaptic potentials consisted of a short‐latency coupling potential, followed by an excitatory potential and a number of inhibitory potentials. These delayed synaptic potentials occurred inconsistently and with a variable latency; they could also be recorded in the cell which had been stimulated. All of the touch cells appeared to be equally effective in initiating synaptic potentials.

3. The short‐latency coupling potential was shown to be mediated through an electrical synapse by observing a voltage change in one touch cell when current was injected into its neighbour. It was not abolished by high concentrations of Mg in the bathing fluid, which blocked chemical synapses in this ganglion. This electrical synapse displayed remarkable rectification; a depolarization could spread from cell to cell in both directions, while a hyperpolarization could spread in neither.

4. The inhibitory potentials were reversed by injecting Cl into the cell. In Cl‐free Ringer solution this effect was so marked that the reversed IPSPs caused long trains of impulses in touch cells, which tended to excite each other by a process of positive feed‐back.

5. Synaptic potentials evoked by activation of a touch cell did not usually reach threshold since excitation and inhibition tended to cancel. The connexions between touch cells that mediated the delayed excitatory and inhibitory potentials are polysynaptic; the interneurones have not yet been found but some of their connexions could be inferred from electrical recordings.

6. Action potentials in sensory cells of a different modality (responding to pressure) also initiated synaptic potentials in the same family of touch cells.

7. The possible significance for integration of these synaptic interactions between sensory cells is discussed.
Hypothalamic temperature and the regulation of respiration of the ox exposed to severe heat
Authors: Findlay J. D. , Hales J. R. S.
Published: December 2014

1. Thermodes have been chronically implanted in the hypothalamus of the ox.

2. During exposure of the ox to severe heat stress, rapid shallow panting changed to slower deeper panting when hypothalamic temperature (Thy) was approximately 40·5° C. With subsequent rapid ambient cooling, hypothalamic temperature declined rapidly, and there was a reversion to rapid shallow panting before respiration slowly returned to normal.

3. When hypothalamic temperature and rectal temperature (TR) had reached about 40° C, raising hypothalamic temperature to about 41·4° C did not cause the onset of slower deeper panting.

4. When hypothalamic temperature and rectal temperature had exceeded about 41° C and slower deeper panting was well established, lowering hypothalamic temperature to about 40° C did not cause any reversion to rapid shallow panting.

5. When hypothalamic temperature and rectal temperature had reached about 40° C, holding hypothalamic temperature at 40° C did not prevent the onset of the slower deeper phase of panting.

6. Under moderate heat stress when hypothalamic temperature was approximately 39·9° C and rectal temperature was approximately 40·4° C, raising hypothalamic temperature at the same rate as that which was associated with the onset of slower deeper panting during severe heat stress, resulted in a parallel increase in the respiratory frequency and fall in rectal temperature; there was no change to the slower deeper form of panting.

7. Holding hypothalamic temperature at 41·7–42° C during post‐heat cooling did not prevent the reversion to rapid shallow panting.

8. It was concluded that the change from rapid shallow to slower deeper panting during severe heat stress, and the reversion to rapid shallow panting during subsequent cooling, were not the result of changes in temperature of the hypothalamic thermoregulatory centres.
Echo‐location and evoked potentials of bats after ablation of inferior colliculus
Authors: Suga N.
Published: December 2014

1. Echo‐location and evoked potentials of blinded Yuma bats (Myotis yumanensis) were studied before and after ablation of the inferior colliculus (I.C.). A task of obstacle‐avoidance was given to the bats: hits and misses of strands in the flight path were counted. Orientation sounds emitted by the bats during flight were recorded.

2. Bilateral ablation of the dorso‐medial region of I.C. including the internuclear cortex and commissure had no effect on obstacle‐avoidance performance. The bats avoided even strands of 0·2 mm diameter with orientation sounds.

3. Bilateral ablation of the dorsal half of I.C. including the external nucleus (lateral cortex) also had no effect on echo‐location.

4. Bilateral ablation of the ventral half of I.C. caused severe deficiency in ability to avoid obstacles. The main nucleus appeared to be very important for echo‐location. When bilateral ablation including the main nucleus was moderate, the bats failed to avoid strands of less than 0·5 mm diameter in spite of detecting them, but avoided large obstacles such as 3·7 mm strands. With severe bilateral ablation including the main nucleus, the bats did not avoid even the 3·7 mm strands in spite of frequent emission of orientation sounds, but often avoided crashing into the wall.

5. Severe unilateral ablation of I.C. including the main nucleus and a part of the lateral lemniscus had no effect on ability to avoid obstacles. Since sound localization by such bats are not explained by Van Bergeijk's model based on Békésy's, a modification of Van Bergeijk's model has to be considered.

6. Of the positive evoked potentials recorded with an active electrode placed at the dorsal surface of I.C., the slow component with a 7–9 msec peak latency reflected activity of inferior collicular neurones, while the fast component (N4) with a 3 msec peak latency represented activity of ascending lateral lemniscal fibres.
An analysis of the mechanism of cessation of uptake of macro‐molecular substances by the intestine of the young rat (‘closure’)
Authors: Clarke Rufus M. , Hardy R. N.
Published: December 2014

1. The longitudinal distribution of cells capable of absorbing macro‐molecular material has been determined in the small intestine of the young rat by measurements of the uptake of [125I]polyvinyl pyrrolidone (PVP).

2. PVP uptake was never seen in the duodenum and became restricted to the distal half of the small intestine by the 18th day of life. The subsequent decline to zero in PVP uptake was due to an almost uniform decrease in PVP uptake by the distal half of the small intestine.

3. Histological studies indicate that this rapid decline in PVP uptake did not reflect a decrease in uptake by individual cells, but rather their replacement by new cells incapable of taking up PVP.

4. Autoradiographic estimates of turnover time in the intestinal epithelium using tritiated thymidine reveal good agreement between the time needed to replace completely the epithelium of the ileum (62 hr) and the duration of the rapid decline in PVP uptake (approximately 3 days).

5. It is concluded that on or about the 18th post‐natal day there is an abrupt change in the functional characteristics of the apical plasma membrane of cells produced by the crypts of Lieberkühn in the distal half of the small intestine. The stimulus for this change is unknown, but cells produced subsequently cannot take up PVP.
Composition of alveolar liquid in the foetal lamb
Authors: Adamson T. M. , Boyd R. D. H. , Platt H. S. , Strang L. B.
Published: December 2014

1. Experiments were performed on foetal lambs at gestations between 125 days and term. The foetus was exteriorized at Caesarean section with the umbilical cord and placental attachment maintained intact. Samples of liquid from the alveolar parts of the lung were withdrawn through a tracheal cannula and samples of lung lymph, plasma and amniotic liquid were also obtained. Measurements were made of total osmolality, concentrations of electrolytes and urea, pH and PCO2. Titrations were carried out with
N/10 HCl and
N/10 NaOH. The water content of the liquids was estimated and concentrations expressed per kg H2O.

2. In alveolar liquid [H+], [K+] and [Cl−] were higher and [Ca2+], [phosphates] and [HCO3−] were lower than in plasma or lymph. In amniotic liquid osmolality [Na+], [Cl−] and [Ca2+] were lower and [phosphates] higher than in plasma or lymph. Alveolar liquid/plasma ratios of [HCO3−], [Ca2+], [Cl−] and [K+] differed from ultra filtrate/plasma ratios of these ions.

3. Titration curves demonstrated a very small amount of buffering in alveolar liquid at its in vivo pH of 6·27 mostly due to HCO3− at an average concentration of 2·8 m
M/kg H2O.

4. It is concluded that foetal alveolar liquid is not an ultrafiltrate of plasma nor a mixture of amniotic liquid and plasma ultrafiltrate, but a special material elaborated by the foetal lung.
The effect of chronic osmotic disturbance on the concentrations of cations in cerebrospinal fluid
Authors: Bradbury M. W. B. , Kleeman C. R.
Published: December 2014

1. Adult cats were rendered hypo‐ and hypernatraemic by peritoneal dialysis. These states were maintained for periods of 2‐5 days.

2. The concentrations in cerebrospinal fluid (c.s.f.) of the cations, potassium, calcium and magnesium all decreased in the hyponatraemic animals and increased in the hypernatraemic animals. These shifts in c.s.f. cation concentrations did not relate to plasma changes in the same cations, which were often in the opposite direction.

3. The relations of the cation concentrations to c.s.f. sodium were not linear and, in the cases of calcium and magnesium, the relevant cation concentration related better to the square rather than the first power of the c.s.f. sodium concentration.

4. Brain water changed much less in the hypo‐ and hypernatraemic animals than might be anticipated from the shifts in blood osmolarity, plasma sodium concentration and muscle water.

5. Isotonicity of the fluids in brain with blood plasma and c.s.f. appeared to be largely maintained by loss or gain of sodium and chloride ions by this tissue.

6. The c.s.f. results may be partly due to a constant influx of the cation in question being diluted with more formed c.s.f. in hyponatraemia and less c.s.f. in hypernatraemia, but the deviations from linearity in the plots of c.s.f. cation against c.s.f. sodium suggest the influence of other factors.
The isolation of a substance very closely resembling the 18‐monoacetate of D‐aldosterone from the venous blood of activated muscle and from contracting muscle
Authors: Lockett Mary F. , Retallack R. W.
Published: December 2014

1. A renally active substance can be extracted in detectable quantity from 150 g flash‐frozen active but not from 150 g flash‐frozen flaccid striped muscle. This substance is identical to the 18‐monoacetate of
D‐aldosterone (18‐MA) in RF value in three solvent systems and in biological activity.

2. The renally active substance is secreted into the blood stream by active but not by flaccid muscles.

3. Bilateral stimulation of decentralized sciatic nerves causes diuresis, natriuresis, a rise in the clearances of creatinine and PAH without change in heart or respiratory rates, in cats under chloralose anaesthesia. These changes can be matched by
I.V. infusion of ADH, 0·3–0·45 m‐u./kg.min.

4. The urinary changes caused by sciatic stimulation are not prevented by transection of the spinal cord but are abolished by hypophysectomy.

5. Hence, like 18‐MA, the muscle substance liberates ADH from the neurohypophysis.
Isotonic lengthening and shortening movements of cat soleus muscle
Authors: Joyce G. C. , Rack P. M. H.
Published: December 2014

1. By supplying pulses to different subdivisions of the ventral nerve roots in rotation it was possible to obtain smooth contractions of cat soleus with low rates of stimulation.

2. After contracting isometrically the muscle was subjected to ‘step’ changes in tension after which it lengthened or shortened isotonically.

3. Isotonic lengthening movements usually began relatively slowly but proceeded with increasing velocity; this acceleration was most conspicuous when low rates of stimulation were used.

4. At low rates of stimulation the isotonic lengthening movement often continued beyond the length at which the muscle could have generated that tension in an isometric contraction. The muscle then shortened slowly back toward that length.

5. Isotonic shortening movements began relatively rapidly, but as shortening continued the movement became slower, and often had an irregular oscillatory course.

6. The isotonic movements are discussed in relation to the sliding filament theory of muscle contraction.

7. The compliance of the series elastic elements was calculated from the relative amplitudes of the ‘step’ changes in tension and length. The stiffness of this component increased with increasing muscle tension.
The distribution of dopamine in the brain of a tortoise, Geochelone chilensis (Gray)
Authors: Juorio A. V.
Published: December 2014

1. Dopamine was found in the tortoise brain; the highest concentration (3·7 μg/g) occurred in a region of the telencephalon containing the nucleus basalis and cortex olfactoria. This region may be considered similar to the mammalian and avian corpus striatum with respect to dopamine.

2. The administration of reserpine or prenylamine substantially decreased the concentration of dopamine in the tortoise brain. This effect appeared later and lasted longer than in birds or mammals. When these drugs were given in doses which nearly depleted brain dopamine the characteristic signs observed in birds or mammals were not present.
The steps between depolarization and the increase in the respiration of frog skeletal muscle
Authors: van der Kloot William
Published: December 2014

1. For many years it has been known that when muscles are depolarized by raising [K+]out there is an increase in respiration, even at levels of depolarization below the threshold for a detectable contracture.

2. K+‐stimulated respiration occurs in muscles in which protein synthesis is blocked with puromycin. Stimulation does not depend upon activation of phosphorylase kinase. In muscle poisoned with IIA and kept in N2, depolarizations below the threshold for contracture cause a fall in creatine phosphate. Apparently an ATPase is activated by depolarization; the resulting ADP is probably the trigger for the increase in oxygen uptake.

3. When the T‐tubules are destroyed by the glycerol‐osmotic shock method depolarization does not produce an increase in respiration.

4. Caffeine is known to stimulate respiration at concentrations below the threshold for producing a contracture. Muscles that have been made refractory to stimulation by potassium are still stimulated by caffeine: the action of caffeine is not antagonized by an increase in extracellular Mg2+. Caffeine must act on a later step in excitation—contraction coupling.

5. K+‐stimulated respiration ultimately depends on the presence of Ca2+ in the Ringer. However, the Ca2+ can be replaced by Ni2+. It is known that Ni2+ does not activate actomyosin. Ni2+ is not sequestered by isolated fragments of the sarcoplasmic reticulum. It seems that the Ni2+ or Ca2+ in the extracellular solution is required for a superficial step in excitation—contraction coupling.

6. Respiration is also often stimulated when muscles are placed in an isotonic sucrose solution, even though the fibres are hyperpolarized. A trace amount of Ca2+ in the sucrose solution is probably necessary for the response.

7. An interaction between Ca2+ and a superficial membrane receptor appears to be an essential, early step in excitation—contraction coupling.
Distribution of granular vesicles in normal and constricted sympathetic neurones
Authors: Geffen L. B. , Ostberg Anna
Published: December 2014

1. A quantitative analysis has been made of the characteristics of granular vesicles in different parts of normal and ligated post‐ganglionic sympathetic neurones supplying the cat spleen. The least diameter of the vesicle membrane and its electron‐dense core was measured from electron micrographs with an automated particle size analyser.

2. Vesicles of average diameter 443 Å, with and without electron‐dense cores (192 Å), were concentrated in the axon terminals of the spleen, whereas in the cell bodies in the coeliac ganglion and their axons there were only a few large vesicles (787 Å) with large granules (562 Å).

3. Ligation of the splenic nerves for 24 hr resulted in an accumulation proximal to the constriction of granular vesicles significantly larger (688 Å) and more completely granulated (478 Å) than those in the terminals.

4. Reserpine reduced the number of vesicles with granular cores without discrimination between the two populations.

5. Since the distribution of noradrenaline in sympathetic neurones can be correlated with the presence of large as well as small granular vesicles, it is suggested that the larger, more granular type found mainly proximally in the neurone is in transit from its perikaryal site of synthesis to the axon terminals, where it is transformed into the smaller synaptic vesicles.