bluuebunny/crossref_metadata_2025 huggingface dataset:
The interaction of calcium and strontium with phosphatidyl serine in the anaphylactic secretion of histamine
Authors: Foreman J. C. , Mongar J. L.
Published: December 2014

1. Spontaneous histamine release from isolated mast cells was found to be independent of calcium in the concentration range up to 1 m‐mole/l. Phosphatidyl serine did not change the effect of calcium on spontaneous release.

2. Spontaneous histamine release was found to vary with the strontium ion concentration. Graded increase in the release occurred as the concentration of strontium was raised from 1 to 10 m‐mole/l. Phosphatidyl serine potentiated this action of strontium; the potentiation showed a graded increase as the phosphatidyl serine concentration was raised from 1 to 100 μg/ml.

3. The activation of anaphylactic histamine release by calcium was potentiated by phosphatidyl serine; the degree of potentiation showed a graded increase as the calcium concentration was raised from 0·1 to 1·0 m‐mole/l.

4. The activation of anaphylactic histamine release by strontium showed little, if any, potentiation by phosphatidyl serine.

5. The response of the mast cells, in terms of anaphylactic histamine release, to calcium, in the presence of optimal concentrations of phosphatidyl serine, was found to be similar to that observed in the presence of strontium alone.

6. These observations are discussed in terms of the concepts of affinity and efficacy of the ions at their receptor sites.
The optical density of erythrolabe determined by retinal densitometry using the self‐screening method
Authors: King‐Smith P. E.
Published: December 2014

1. Retinal densitometry has been used to determine the optical density of erythrolabe in foveal cones.

2. A self‐screening method was used, as in Rushton's (1963b) measurements on chlorolabe.

3. Psychophysical experiments have demonstrated that self‐screening in cones depends on the direction of the light in the same manner as the Stiles—Crawford efficiency. Stiles—Crawford measurements were therefore made on each subject and a method was devised to allow for the corresponding reduction in self‐screening in densitometry.

4. Complications arising from coloured bleaching products, the presence of a second visual pigment and the fluorescence of visual pigments are considered.

5. The mean value for optical density at 560 nm was found to be 0·40 ± 0·07
S.E. of mean for the five subjects (two deuteranopes, two deuteranomalous subjects and one normal subject).

6. This result is in good agreement with Rushton's (1963b) value of 0·35 for chlorolabe using retinal densitometry.

7. The densitometry results are also in reasonable accord with recent psychophysical and microspectrophotometry measurements. This provides evidence that densitometry measures all the cone pigment in an unbiased manner and not just a superficial sample.
The optical density of erythrolabe determined by a new method
Authors: King‐Smith P. E.
Published: December 2014

1. A new method is described for the determination of optical density by retinal densitometry based on an analysis of stray light.

2. The basic assumption used is that the stray light present in retinal densitometry is independent of wave‐length. The justification for this assumption is considered.

3. The stray light and hence the optical density was determined by a method of successive approximations using a Linc 8 computer.

4. The optical density of erythrolabe for the direction of maximum Stiles—Crawford efficiency was determined for five subjects, two deuteranopes, two deuteranomalous and one red‐rich normal subject. The mean values for three of the subjects were close to the grand mean value of 0·42, but the other two subjects had considerably higher and lower values respectively.

5. The results are in satisfactory agreement with optical density values determined by the self‐screening method using retinal densitometry, and also with determinations using microspectrophotometry and psychophysics.

6. The relevance of dielectric wave‐guide modes in the outer segments is considered.
Amylase secretion by the perfused cat pancreas in relation to the secretion of calcium and other electrolytes and as influenced by the extrenal ionic environment*
Authors: Argent B. E. , Case R. M. , Scratcherd T.
Published: December 2014

1. Amylase secretion from the perfused pancreas consists of two components: a small continuous basal secretion and a stimulated secretion in response to acetylcholine or cholecystokinin‐pancreozymin. The response to small doses of either stimulant was repeatable over several hours.

2. The calcium concentration of pancreatic juice, always less than that of the perfusate, was normally constant above secretory rates of 0·15 g/10 min. However, when the concentration of enzymes in the juice rose, either after stimulation or at very low secretory rates, the calcium concentration rose in parallel, suggesting that this calcium is bound to, or is a component of, pancreatic enzymes.

3. Elevation of the perfusate calcium concentration resulted in a parallel increase in the calcium concentration of the pancreatic juice.

4. Calcium‐free solutions initially caused a small reduction in basal and stimulated amylase secretion and, after prolonged periods of perfusion, abolished stimulated secretion and caused a reduction in electrolyte secretion. The latter was completely reversed by calcium‐rich perfusates but the effects on enzyme secretion were only partially reversible.

5. Calcium‐rich perfusates had no effect on the rate of electrolyte secretion but potentiated submaximally stimulated amylase secretion.

6. Barium did not substitute for calcium in supporting pancreatic secretion.

7. Alterations in the extracellular concentrations of sodium, potassium and magnesium had no direct effect on amylase secretion.

8. The local anaesthetic tetracaine inhibited amylase secretion at a lower concentration than that required to inhibit electrolyte secretion.

9. It is concluded (a) that calcium is secreted into the pancreatic juice in two fractions, one associated with enzymes and the other with the electrolyte component of the juice; and (b) that calcium ions play an important role in the stimulus‐secretion coupling of pancreatic acinar cells, but that the effects of calcium depletion on electrolyte secretion may principally be due to alterations in the permeability of the duct system.
Electrical properties of toad sartorius muscle fibres in summer and winter
Authors: Dulhunty Angela F. , Gage Peter W.
Published: December 2014

1. The area and circumference of surface fibres of sartorius muscles were measured from photomicrographs of frozen sections of whole muscles, and compared with the values obtained assuming a circular cross‐section. The latter assumption gave an over‐estimate of the mean area of 28%, but only a 2% over‐estimate of the circumference. In isolated, single fibres, the assumption gave over‐estimates of 25 and 6%, of area and circumference respectively.

2. The passive electrical properties of fibres were different in summer and winter. The mean internal resistivity, membrane resistance and membrane capacitance were 147 Ω.cm, 7·6 kΩ.cm2 and 4 μF/cm2 in summer, and 194 Ω.cm, 3·9 kΩ.cm2 and 6·7 μF/cm2 in winter, in fibres of comparable diameters in situ. In single fibres in summer, the mean values were 120 Ω.cm, 8·6 kΩ.cm2 and 3·6 μF/cm2.

3. In glycerol‐treated fibres the mean specific membrane capacitance was 1·0 μF/cm2 in summer and 2·0 μF/cm2 in winter. The internal resistivity and specific membrane resistance were 167 Ω.cm and 8·9 kΩ.cm2 in summer, and 232 Ω.cm and 3·9 kΩ.cm2 in winter.

4. Early after‐depolarizations were recorded in glycerol‐treated fibres which had a low membrane capacitance, did not twitch and showed little ‘creep’. Electron micrographs of glycerol‐treated fibres showed disruption of the transverse tubular system and sarcoplasmic reticulum.

5. After exposure of muscles to 400 m
M urea or acetamide for 1 hr, muscle fibres did not twitch and had a reduced membrane capacitance in Ringer solution.
Effects of proteolytic enzymes on function and structure of frog neuromuscular junctions
Authors: Betz W. , Sakmann B.
Published: December 2014

1. Frog cutaneous pectoris nerve‐muscle preparations were incubated with collagenase and protease and examined with electrophysiological and electron microscopic techniques.

2. The physiological properties and intracellular ultrastructural appearance of individual muscle and nerve cells were not affected by the enzyme treatment. However, neuromuscular transmission and the morphology of the nerve‐muscle junction were altered.

3. Collagenase produced an irreversible loss of activity of end‐plate cholinesterase and a partial loss of stainable ‘synaptic cleft material’.

4. Protease produced these changes and, in addition, the entire basement membrane was digested, which led to ‘synaptic disjunction’ of nerve terminals and muscle end‐plates.
Location of inexchangeable sodium in the nucleus and cytoplasm of oocytes of Bufo bufo exposed to sodium‐free solutions
Authors: Dick D. A. T. , Fry D. J.
Published: December 2014

1. In oocytes exposed to Ringer solution in which Li substitutes for Na, 13–62% Na is inexchangeable with Li.

2. Nuclei of oocytes isolated by dissection in salt solutions swell irrespective of the concentration or ionic components of the solution. When isolated in 4% bovine albumin solutions, swelling is negligible.

3. When the nuclei of cells exposed to Li are isolated in 4% albumin solution, less than 6% of the inexchangeable Na is found in the nucleus, while 36–88% of it is found in the cytoplasmic fragments remaining after removal of the nucleus.

4. When a Li‐exposed cell is crushed in a cellophane bag and dialysed against Ringer or Li‐substituted Ringer, 86–92% of the inexchangeable Na diffuses out.

5. It thus appears that the inexchangeable Na is located almost entirely in the cytoplasm and hardly at all in the nucleus, and is not bound to macromolecules within the cell.
The effect of salt adaptation on the permeability and cation selectivity of the goldfish intestinal epithelium
Authors: Ellory J. C. , Nibelle Jacqueline , Smith M. W.
Published: December 2014

1. The short‐term uptake of Na by the goldfish mucosa was compared using both inulin and choline as markers of extracellular space. The results were virtually identical, the distribution of both choline and inulin increasing rapidly to measure a space at 1 min which then remained nearly constant during a following 4 min incubation.

2. Using inulin as space marker, the uptake of various alkali metal cations was determined from a 1 min contact with the mucosa. The relative rates of uptake were Tl > K > Rb > Cs > Na > Li, with a low selectivity ratio, the range of permeabilities being no greater than 5.

3. The selectivity sequence was the same in both salt and fresh‐water adapted fish. Of the alkali metal cations tested, only Na showed a significantly decreased uptake on adaptation to salt.

4. Isolated intestinal preparations from salt‐adapted fish showed a reduced short‐circuit current compared with fish adapted to fresh water, the values being 12·3 ± 1·2 and 35·7 ± 1·5 μA cm−2 respectively. In both cases the short‐circuit current was equivalent to the net transport of Na measured isotopically.

5. In Krebs—Henseleit medium, the measured tissue resistance was approximately 100 Ω cm−2 for both salt and fresh‐water adapted fish.

6. It is concluded that regulation of cation transport in goldfish intestinal epithelium is specific for Na and mediated primarily through cellular rather than extracellular pathways.
The ionic dependence of the strength and spontaneous relaxation of the potassium contracture induced in the heart of the frog Rana pipiens
Authors: Chapman R. A.
Published: December 2014

1. The tension generated by isolated frog atrial trabecules, during exposure to solutions containing a high potassium concentration, is not maintained but spontaneously relaxes. The final part of this relaxation can be fitted by a single exponential function.

2. The recovery of the tension generating mechanisms following the spontaneous relaxation of a potassium contracture depends on the preceding membrane potential and the time since the last contracture.

3. The rate of the exponential phase of the spontaneous relaxation is independent of the [K]o and hence the membrane potential, the [Ca]o; and when the [Ca]o/[Na]o2 ratio is maintained it is also independent of the [Na]o. This relaxation is not influenced by atropine or pronethalol.

4. When sodium is totally excluded from the bathing medium the rate of relaxation of a later potassium contracture is much increased. It is argued that this change is due to a fall in the intracellular sodium concentration.

5. The consequences of these results are discussed, and the hypothesis that is favoured would require that contraction is induced by a transient release of calcium into the sarcoplasm, probably triggered by a potential dependent, and probably also transient, influx of calcium through the cell membrane. Relaxation is supposed to occur when this activator‐calcium is then removed by an intracellular relaxing system that resembles the sarcoplasmic reticulum of other muscles. What this intracellular structure might be, is also discussed.
An inhibition of post‐ganglionic motor transmission in the mammalian vas deferens by D‐lysergic acid diethylamide
Authors: Ambache N. , Dunk Linda P. , Verney J. , Zar M. Aboo
Published: December 2014

1. Under certain conditions
D‐lysergic acid diethylamide (LSD), 10−9‐10−6 g/ml., exerted an immediate, prolonged and slowly reversible inhibitory effect upon the post‐ganglionic motor transmission in desheathed guinea‐pig vas deferens preparations.

2. The most critical factor influencing this action of LSD appeared to be the train length. With short trains of less than 4 or 5 pulses the twitch inhibition produced by LSD was often total. With longer trains (5–20 pulses), the degree of inhibition declined with increase in train length. These results suggest the existence of two components in the motor response to post‐ganglionic stimulation, distinguished by their susceptibility to LSD.

3. The inhibition of the LSD‐susceptible component was related to the dose of LSD in the range 10−9‐10−6 g/ml., reaching a maximum at 0·5‐1 × 10−6 g/ml. The response remnants elicited by trains of more than 5 pulses under these conditions could not be reduced further by a ten‐ to twenty‐fold increase in LSD concentration to 10−5 g/ml. and were in fact slightly potentiated.

4. The inhibition of post‐ganglionic motor transmission by LSD was not explicable on the basis of an α‐adrenoceptor blockade because it was not associated with any reduction in motor responses to noradrenaline.

5. The use of propranolol excluded mediation of the LSD‐inhibition by β‐adrenoceptors.

6. The LSD effect was not due to a non‐specific smooth muscle depression because it was not associated with any reduction in motor responses to acetylcholine, ATP or bradykinin.

7. The inhibitory effect of LSD on post‐ganglionic transmission resembled that of noradrenaline in that it was antagonized by phentolamine; another α‐adrenoceptor blocking agent, phenoxybenzamine, was less effective than phentolamine in this respect.

8. The LSD‐inhibition was obtained in preparations taken from reserpinized guinea‐pigs.

9. The inhibition of motor transmission in the vas deferens by LSD was confirmed in rats, Meriones shawii and rabbits.

10. The inhibition of post‐ganglionic transmission by LSD was unrelated to its ability to antagonize 5‐hydroxytryptamine (5‐HT), to which the longitudinal muscle of the guinea‐pig vas deferens is insensitive. The more potent 5‐HT antagonists, methysergide and BOL 148 were either virtually inactive or considerably weaker than LSD.
The effects of changes in arterial plasma calcium concentration on submandibular secretory potentials
Authors: Creed Kate E. , McDonald I. R.
Published: December 2014

1. The concentration of Ca in the arterial blood plasma perfusing submandibular glands of anaesthetized cats and possums (Trichosurus vulpecula) was altered by constant‐rate close arterial injection of isotonic CaCl2 or EDTA solutions.

2. There were no significant changes in the resting potentials of surface acinar cells in either species when the arterial plasma Ca concentration was altered over the range 0–30 m
M.

3. Secretory potentials in response to parasympathetic stimuli and close arterial injection of ACh were reduced and finally abolished during EDTA injection, but temporarily restored by injection of CaCl2.

4. Secretory potentials in response to 1 Hz parasympathetic stimuli in the cat were enhanced by increasing the gland arterial Ca concentration up to 5 m
M; but responses to 10 Hz stimuli or close arterial ACh injection were not affected. There was no such enhancement of secretory potentials in the possum.

5. Increase in the gland arterial plasma Ca concentration above 5 m
M caused reduction in the amplitudes of the secretory potentials to all stimuli in both species, until they were abolished at 7–10 m
M in the possum and 15–20 m
M in the cat.

6. In both species, increase in the gland arterial plasma Ca concentration caused increase in the gland blood flow and enhancement of the vasodilator effects of parasympathetic stimuli and ACh injection. EDTA injection was sometimes associated with a vasoconstrictor response to parasympathetic stimuli.

7. It is concluded that the secretory potentials, but not the resting potentials, of submandibular secretory cells require the presence of Ca in the interstitial fluid. It is suggested that Ca affects both the release of transmitter and at higher concentration the mechanism by which it activates the secretory cells.
Release of transmitters into the perfused third cerebral ventricle of the cat
Authors: Ashkenazi Ruth , Holman R. B. , Vogt Marthe
Published: December 2014

1. The third cerebral ventricle of cats treated with nialamide and anaesthetized with chloralose was perfused, and the effluent was tested for 5‐hydroxytryptamine (5‐HT) and also for acetylcholine (ACh) when the perfusion fluid contained neostigmine.

2. Under ‘resting’ conditions a 25 min sample of effluent contained from < 1 to 6 ng 5‐HT; the release remained steady during many hours of perfusion. It was necessary to watch out for traces of blood which might contribute to the 5‐HT content and which were only visible after centrifugation.

3. A number of regions in the ventral mid‐brain and hind‐brain were stimulated, including the two most anterior nuclei of the raphe, nucleus linearis rostralis and intermedius. Release of 5‐HT (rarely more than 2 ng) was only obtained on stimulation of these two nuclei, whereas ACh was released by stimulating many points, such as the reticular formation or the decussation of the superior cerebellar peduncles, but not the two raphe nuclei.

4. Low frequencies of stimulation were more effective at releasing 5‐HT, and high frequencies at releasing ACh.

5. Since the amount of 5‐HT released on stimulation was rarely more than 2 ng, a powerful re‐uptake process was suspected and confirmed by the use of chlorimipramine. Intravenous, intraperitoneal and intraventricular use of this drug temporarily increased the basal release to values ranging from 20 to 50 ng in 25 min samples, and about trebled the release on stimulation of either of the linear nuclei.

6. Intravenous administration of chlorimipramine (10 mg/kg) caused the disappearance of electrical responses evoked in the brain stem by afferent sensory stimuli.
Studies on the site of termination of static and dynamic fusimotor fibres within muscle spindles of the tenuissimus muscle of the cat
Authors: Brown M. C. , Butler R. G.
Published: December 2014

1. The site of termination of static and dynamic fusimotor fibres has been mapped by finding which intrafusal muscle fibres have been depleted of glycogen as a result of tetanic stimulation of single γ fibres. Long periods of stimulation coupled with occlusion of the blood supply were necessary to cause glycogen depletion.

2. In cat tenuissimus muscle, dynamic γ motor fibres always activated bag intrafusal muscle fibres, and occasionally chain fibres. Static γ fibres always activated chain fibres and frequently activated bag fibres as well.

3. It is argued that these results can be fitted into the hypothesis of the mechanism of internal functioning of the spindle originally proposed by Jansen & Matthews (1962). It is also pointed out that the results raise problems concerning the mechanism of development of the spindle motor innervation.
Effects of anions and cations on the resting membrane potential of internally perfused barnacle muscle fibres
Authors: Lakshminarayanaiah N. , Rojas E.
Published: December 2014

1. Single barnacle muscle fibres from Megabalanus psittacus (Darwin) were internally perfused with a number of K salt solutions (200 m
M) which were made isotonic to the barnacle saline with sucrose.

2. 200 m
M‐K acetate solution, in general, was found to be more effective than other solutions of K salts in generating and maintaining stable resting membrane potential of −56·0 ± 0·7 mV (all potentials are referred to the external solutions as ground). The various K salts, on the basis of the magnitude of the resting potential they generated in the muscle fibres, followed the sequence, acetate > isethionate > aspartate > glutamate > fluoride > monohydrogen phosphate > succinate > citrate > sulphate > oxalate > iodobenzoate > ferrocyanide > chlorate > nitrate > chloride > thiocyanate > iodide > bromide > cyanide.

3. The resting potential in muscle fibres perfused with solutions of acetate, aspartate and glutamate increased linearly with the logarithm of the K concentration (slope = 30·4 mV for K acetate and 27·4 for K aspartate and glutamate) when the ionic strength of the solutions was progressively increased from 50 to 650 m
M. On the other hand, similar increase of ionic strength beyond 200 m
M of solutions of K isethionate, fluoride, monohydrogen phosphate, succinate and citrate depolarized the muscle fibres.

4. Perfusion of acetate solutions of other alkali metal ions gave low values for the resting potential and followed the sequence K > Na > Rb > Li > Cs. Also NH4 and Tris ions gave low values for the resting potential which underwent oscillations associated with the twitching of the fibre and occasionally became positive in value (action potential).

5. Addition of tetraethyl ammonium chloride (TEA‐Cl), 20–100 m
M, to K acetate solutions (200 m
M) depolarized the fibre membrane and the consequent reduction of resting potential varied linearly with the logarithm of TEA concentration.

6. Replacement of chloride ion by acetate or isethionate in the external solution did not change significantly the resting potential although the values were consistently lower by about 2 mV.

7. Complete elimination of K in the external solution and reduction of its ionic strength using sucrose depolarized the muscle fibres by about 27 mV when Na was changed from 475 to 1 m
M. Under these conditions, external solutions completely in acetate form gave resting potentials which were more positive than those observed in completely chloride solutions by 6–8 mV.

8. Replacement of Na by Li, Tris, choline, tetramethyl or tetraethyl ammonium ion in the external solution made the values of the resting potential more positive (depolarization). Similarly increasing the concentration of K (or Cs or Rb in place of K) by correspondingly decreasing the concentration of Na in the outside solution depolarized the fibres and the resting potential became zero at a concentration of 280 m
M (or 308 or 1500 m
M for Rb or Cs, respectively) on extrapolation.
Pancreatic enzyme response to secretin and cholecystokinin‐pancreozymin in the rat
Authors: Fölsch U. R. , Wormsley K. G.
Published: December 2014

1. The report describes a new technique for collecting pancreatic juice in anaesthetized rats. The technique, which involves perfusion of the duodenum, is particularly suitable for analysing the characteristics of pancreatic enzyme secretion. To ensure stable secretory conditions, the rats were kept at 30° C.

2. Different combinations of secretin and cholecystokinin‐pancreozymin have been given by continuous intravenous infusion and the patterns of secretion of amylase and trypsin have been defined.

3. Maximal secretion of the pancreatic enzymes was observed with 60 IU/kg.hr CCK‐PZ (amylase) or 120 CU/kg.hr (trypsin) combined with 0·5 CU/kg.hr (secretin).

4. Pancreatic enzyme secretion in response to submaximal stimulation with CCK‐PZ was potentiated by secretin.

5. Supramaximal stimulation with CCK‐PZ resulted in significantly less secretion of pancreatic enzymes than in response to maximal stimulation.

6. The pancreatic secretion of enzymes was poorly sustained during constant‐rate stimulation with intravenous hormones, at all dose rates.

7. The significance and possible mechanisms of the biphasic pattern of enzyme secretion in response to increasing doses of stimulant hormones and the fall‐off in enzyme secretion during constant‐rate stimulation are discussed.
The maturation of neuromuscular function in a multiply innervated structure: development of the longitudinal smooth muscle of the foetal mammalian gut and its cholinergic excitatory, adrenergic inhibitory, and non‐adrenergic inhibitory innervation
Authors: Gershon Michael D. , Thompson Elizabeth Barnes
Published: December 2014

1. The earliest components of the developing innervation of the rabbit intestine to be detected in this study were the cholinergic excitatory and the intrinsic inhibitory innervation. These developed simultaneously in the rabbit at 17 days of gestation. Both were also present in the mouse by the 16th day of gestation. Responsiveness of rabbit tissue to exogenous acetylcholine appeared together with the advent of a functional cholinergic innervation. Since excitatory responses were potentiated by eserine, the tissue was probably able to inactivate acetylcholine through hydrolysis mediated by cholinesterase. Early relaxant responses resisted blockade by adrenergic neurone blocking agents and by antagonists active at α‐ and β‐adrenoceptors.

2. The development of the adrenergic innervation lagged far behind that of the other two components. Specific uptake of noradrenaline in the rabbit was detected for the first time at the 21st day of gestation and stores of noradrenaline could not be detected histochemically until 26‐28 days. However, relaxant responses to stimulation of the perivascular sympathetic supply, such as characterize adult tissues, had not yet developed by the time of birth. Relaxation in response to perivascular stimulation could be seen 30 days after birth.

3. Morphologic studies indicated that the longitudinal layer of smooth muscle was very primitive when an effective innervation was established. Although contractile, the cells were still myoblasts. Neural elements also appeared primitive. Thus considerable morphological maturation follows the development both of a functioning contractile machinery and innervation in the foetal gut.

4. This study helps establish that the intrinsic inhibitory innervation of the gut is not adrenergic.
Uptake of [3H]glycine and [14C]glutamate by cultures of chick spinal cord
Authors: Cho Y. D. , Martin R. O. , Tunnicliff G.
Published: December 2014

1. Spinal cord explants from chick embryos, grown in culture for up to 16 days, rapidly accumulated [3H]glycine and [14C]glutamate when incubated at 25° C in a medium containing either 2 × 10−10
M glycine or 4·8 × 10−8
M glutamate.

2. After 90 min incubation, a tissue/medium ratio of 60:1 and 20:1 was attained for [14C]glutamate and [3H]glycine respectively.

3. The uptake systems, in addition to requiring sodium ions in the medium, were temperature sensitive, showed saturation kinetics, and were inhibited by ouabain.

4. For the glutamate and glycine accumulation the Km value was 4·3 × 10−5 and 4·1 × 10−5
M respectively, indicating that a high affinity uptake process is involved.

5. The rate of accumulation of both glutamate and glycine increased in cultures between the ages of 3 and 10 days thus matching their morphological development.

6. In light of previous evidence, the demonstration of an active transport mechanism for both glutamate and glycine in spinal‐cord‐cultures that also shows a relationship with morphological maturity, suggests that these two amino acids may play a major role in spinal cord function.
The maximum derivatives of left ventricular pressure and transverse internal diameter as indices of the inotropic state of the left ventricle in conscious dogs
Authors: Barnes G. E. , Bishop V. S. , Horwitz L. D. , Kaspar R. L.
Published: December 2014

1. In normal, conscious dogs,
I.V. infusion of isoprenaline caused inases in heart rate and the maximal derivatives of left ventricular pressure (dP/dt max) and left ventricular internal diameter (dD/dt max). The changes in both derivatives were linearly related to the increase in heart rate.

2. Increments in heart rate produced by right atrial pacing caused only minimally significant increases in both dP/dt max and dD/dt max at heart rates of 180 beats/min. Increases in heart rate, with end diastolic diameter maintained constant, resulted in small but significant increases in dP/dt max and no significant increase in dD/dt max.

3. Increasing preload by volume infusion had little effect on either derivative, while increasing afterload by phenylephrine administration produced a small but significant increase in dP/dt max and no change in dD/dt max.

4. Both dP/dt max and dD/dt max are equally reliable as indices of the inotropic state of the myocardium and are minimally influenced by changes in preload, afterload or heart rate.
The binding of labelled saxitoxin to the sodium channels in nerve membranes
Authors: Henderson R. , Ritchie J. M. , Strichartz G. R.
Published: December 2014

1. Tritium labelled saxitoxin has been prepared and purified, and its binding both to intact rabbit vagus nerves and to a solubilized preparation of garfish olfactory nerve membranes has been examined.

2. In intact and solubilized nerves there is a saturable binding component of magnitude equal to that previously obtained for labelled tetrodotoxin.

3. This component of bound saxitoxin is displaced competitively by tetrodotoxin, and it is concluded that the two toxins bind to the same site.

4. The saturable saxitoxin (STX) interaction with the nerve membrane is reversible and can be described by the equation STX + R ⇌ STX.R where R is the binding site or receptor. With the solubilized preparation of garfish nerve membranes the saxitoxin‐receptor reaction rates are almost four times faster than those of tetrodotoxin. The half‐life of the saxitoxin‐receptor complexes is 13 sec compared with 44 sec for the tetrodotoxin‐receptor complex.

5. A number of agents were tested for their ability to displace the labelled saxitoxin. Calcium and thallous ions each produced significant reversible reduction in binding, with apparent equilibrium dissociation constants of about 20–30 m
M. Toxin binding is also inhibited reversibly in acidic solutions by protons competing with toxin for a binding site with a pKa of 5·6–5·9. All three ions are known to block sodium currents in myelinated nerve at similar concentrations. Our experiments indicate that they do so at the site of toxin binding.

6. Lidocaine and veratrine do not affect the binding of saxitoxin.
The intervals between miniature end‐plate potentials in the frog are unlikely to be independently or exponentially distributed
Authors: Cohen Ira , Kita Hiroshi , Van Der Kloot William
Published: December 2014

1. It has been suggested that spontaneous quantal release of transmitter at the neuromuscular junction is a Poisson process. One logical argument against accepting the Poisson hypothesis is that so far relatively few intervals between miniature end‐plate potentials (min.e.p.p.s) have been studied in any single experiment. Release is known to occur from many sites on the nerve terminal, so many intervals must be studied before drawing any conclusions about the timing of release from the individual sites. Moreover, the statistical methods that have been used are relatively insensitive to deviations from Poisson predictions.

2. The Poisson hypothesis is evaluated with respect to three major criteria:

(a) The fit to the exponential distribution is analysed by five goodness of fit tests which were applied to eleven sets of data, showing that it is unlikely that the data sets were generated by an exponential distribution.

(b) The independence of intervals is assessed in two ways. First, the autocorrelogram of intervals is constructed. This shows an excess of significant positive correlations beyond the 5% limits of the Poisson expectation. Secondly, the unsmoothed power spectrum is calculated, and compared to the Poisson prediction by means of the modified mean test. Again, most sets deviate significantly from the Poisson expectation. It is unlikely that the intervals are independent.

(c) The possibility of simultaneous occurrences is evaluated by construction of the amplitude histogram of min.e.p.p.s. In all sets the Poisson prediction for the frequency of multiples of the unit height was exceeded by the empirical data sets. The over‐all conclusion is that the process which generates spontaneous releases is unlikely to be Poisson.
Post‐tetanic effects in motor units of fast and slow twitch muscle of the cat
Authors: Bagust J. , Lewis D. M. , Luck J. C.
Published: December 2014

1. Motor unit twitches were examined in cat flexor digitorum longus (fast twitch) and soleus (slow twitch) muscles. The time course of the effects of a standard tetanus on the peak twitch tension was plotted and the maximal potentiation or depression (the post‐tetanic ratio) was measured.

2. The post‐tetanic ratio decreased continuously as the twitch time to peak of motor units increased; motor units from flexor digitorum longus and soleus could be described as a single population. The closest approximation to a linear relationship was found by plotting post‐tetanic ratio against the reciprocal of time to peak.

3. The post‐tetanic ratio was also related to the ratio of tetanic to twitch tension. The time of maximum potentiation or depression occurred between 1 and 11 sec, but this variable was unrelated to the time to peak or any other characteristic of the motor unit.
Capacitance effects and blood reservoir function in the splanchnic vascular bed during non‐hypotensive haemorrhage and blood volume expansion in anaesthetized cats
Authors: Greenway C. V. , Lister G. E.
Published: December 2014

1. These experiments were designed to measure how much blood is mobilized from or pooled in the liver, spleen and gastro‐intestinal tract to compensate for a haemorrhage or infusion of blood.

2. Hepatic volume, splenic weight and intestinal volume were recorded in cats anaesthetized with sodium pentobarbitone. Whole blood was removed or infused at rates of 0·5–0·6 ml. kg−1.min−1 until 10 ml./kg (19% blood volume) had been removed or 18 ml./kg (34% blood volume) had been infused. These blood volume changes produced only small changes in arterial and portal pressures except after removal of 8 ml./kg (15% blood volume) when arterial pressure began to decrease rapidly.

3. With small haemorrhages of up to 4% blood volume, the liver contributed 16%, the gastro‐intestinal tract 23% and the spleen a negligible proportion of the blood volume removed. With haemorrhages of 15% blood volume, the liver contributed 21%, the gastro‐intestinal tract 22% and the spleen 19% of the volume removed; a total splanchnic contribution of 62%.

4. During infusions of 5–18 ml./kg (10–34% blood volume), the liver pooled 20%, the gastro‐intestinal tract 40% and the spleen 6% of the volume infused; a total splanchnic contribution of 66%.

5. It is concluded that the splanchnic bed mobilizes or pools up to 65% of the volume of blood removed from or infused into the cats. The mechanisms responsible for this blood reservoir function are discussed. While several factors may be involved, it seems likely that a reflex regulation involving atrial receptors and the sympathetic innervation of the splanchnic capacitance vessels is of predominant importance.
A note on the interaction of spontaneous and evoked release at the frog neuromuscular junction
Authors: Barrett Ellen F. , Barrett J. N. , Martin A. R. , Rahamimoff R.
Published: December 2014

1. The interaction between spontaneous miniature end‐plate potentials and evoked end‐plate potentials was investigated at the frog neuromuscular junction using focal extracellular recording techniques.

2. End‐plate potentials evoked immediately after a spontaneous miniature potential were facilitated by up to 20%. The percentage facilitation was negatively correlated with the average quantal content of the end‐plate potential.
The response to distension of the pulmonary vein—left atrial junctions in dogs with spinal section
Authors: Burkhart Sally M. , Ledsome J. R.
Published: December 2014

1. A reflex increase in heart rate in response to pulmonary vein distension was observed in decerebrate dogs. This increase could not be totally abolished by treatment with both propranolol and bretylium tosylate. Only bilateral cervical vagotomy abolished the reflex increase in heart rate.

2. A significant increase in heart rate occurred in a total of seventeen spinal dogs during pulmonary vein distension.

3. In seven spinal animals in which blood pressure was maintained by the continuous infusion of noradrenaline, the increase in heart rate could be totally prevented by cervical vagotomy.

4. The time course of the increase in heart rate observed in the spinal animals was rapid, reaching maximum expression within 10 sec of pulmonary vein distension. Such a time course is dissimilar from that associated with pulmonary vein distension in intact or decerebrate dogs in which maximum increases in heart rate take 1–3 min to develop.

5. It is concluded that the reflex tachycardia resulting from pulmonary vein distension may be mediated by both an efferent sympathetic and an efferent vagal pathway, the relative significance of each component being dependent upon the prevailing autonomic drive existent in the animal at any specific time.
The formation of synapses in regenerating mammalian striated muscle
Authors: Bennett M. R. , Florin T. , Woog R.
Published: December 2014

1. A histological and electrophysiological study has been made of the formation of synapses in soleus and extensor digitorum longus muscles of adult rats regenerating from minced muscle fragments.

2. In the first 8 days of regeneration, myoblast and myotubes formed within the basement membranes of degenerating myofibres.

3. Eleven‐ to fourteen‐day regenerates contained fasicles of myotubes and myofibres and both nerves and spontaneous miniature end‐plate potentials (m.e.p.p.s) were observed for the first time, although very few synapses show evoked end‐plate potentials (e.p.p.s).

4. Eighteen‐ to twenty‐six‐day regenerates contained. myofibres on which only a single end‐plate could be detected; 30% of these synapses had a normal amplitude—frequency distribution of m.e.p.p.s and subthreshold e.p.p.s whilst at the remainder the e.p.p. was either suprathreshold or did not occur.

5. Thirty‐ to sixty‐day regenerates contained myofibres and end‐plates with the same morphological and functional characteristics as those in normal muscle.
Mechanism of anion permeation through the muscle fibre membrane of an elasmobranch fish, Taeniura lymma
Authors: Hagiwara Susumu , Takahashi Kunitaro
Published: December 2014

1. Properties of anion permeation through the membrane of skeletal muscle fibres of the stingray, Taeniura lymma, were studied with intracellular recording and polarization techniques.

2. The Cl conductance of the resting membrane in the normal stingray saline at pH 7·7 is 8–10 times greater than the K conductance.

3. The Cl conductance decreases with decreasing external pH, with an apparent pK of 5·3, whereas the K conductance is independent of pH between 4 and 9.

4. The Q10 of the Cl conductance is about 2·0, compared with a value of 1·2–1·4 for the K conductance.

5. The Cl conductance is proportional to the external Cl concentration when observed after the fibre is equilibrated in the test solution.

6. The permeability sequence obtained by potential measurement is SCN > NO3 > Cl = Br > I > ClO3 and the permeability ratio is independent of the mole fraction of anions.

7. The conductance sequence determined by total replacement of the external Cl with other anion species differs from the permeability sequence and the conductance observed for partial replacement deviates significantly from that expected from the independence principle.

8. Possible mechanisms of anion permeation are discussed.
The accumulative properties of facilitation at crayfish neuromuscular synapses
Authors: Linder T. M.
Published: December 2014

1. Synaptic facilitation was measured with intracellular recording at two classes of neuromuscular synapses in the opener muscle of the crayfish dactyl by placing a test stimulus at various intervals after either a single conditioning stimulus or a short conditioning train.

2. The facilitative effect of one stimulus reaches approximately the same level with both the superficial central and superficial distal synapses. The facilitation decreases smoothly in two phases after the conditioning stimulus at superficial central synapses and in a more complex fashion at superficial distal synapses.

3. The two synaptic types differ in the manner in which they add up the facilitative effects produced by each of the stimuli in a short train. With superficial distal synapses the facilitative effects of conditioning stimuli add linearly, while with superficial central synapses the facilitative effects accumulate exponentially.

4. The linear addition of facilitation at superficial distal synapses is not altered when the quantal content is lowered by decreasing the external Ca concentration from 13·5 to 3 m
M.

5. The rate of decay of facilitation is the same following both one and three conditioning stimuli, even though the facilitation is nearly six times larger in the latter case.

6. The results are discussed in terms of mechanisms for synaptic facilitation.
An outflow of acetylcholine from normal and regenerating ventral roots of the cat
Authors: Evans C. A. N. , Saunders N. R.
Published: December 2014

1. An outflow of acetylcholine (ACh) has been measured from cat ventral roots in situ and in vitro, using standard bio‐assay techniques. The ACh was collected in chambers, filled with physiological solution containing anticholinesterase, which surrounded the root.

2. The outflow fell rapidly at first and then progressively more slowly, taking several hours to fall to a level near the assay threshold. The outflow of ACh resulted from cutting a root or from such conventional manipulations as stretching the root or teasing apart root filaments. The outflow could occur either from the end of a root (following cutting) or from along the length of the root (following stretching or teasing). The outflow was only detected in the presence of an anticholinesterase.

3. ACh was resynthesized by roots at a rate which was usually rapid enough to maintain their ACh content at its original level in spite of a considerable ACh outflow. In roots subjected to a minimum of interference their ACh content built up to about twice the initial content after 5‐7 hr soaking in eserinized Krebs solution although the total ACh outflow was equivalent to the original ACh content.

Roots which were cut or stretched several times within a few hours put out a large amount of ACh and showed a fall in their ACh content below the initial level.

4. The time course of sealing of the damaged ends of axons following crushing was assessed by measuring the injury potential for 1–2 hr after crushing at room temperature; in normal roots the half‐time for decline of the injury potential was 91 ± 10 min. This was slower than the rate of decline of the ACh outflow.

5. An explanation for the observed outflow of ACh is discussed in terms of diffusion of ACh and sealing of axon ends. It is concluded that much of the ACh in normal ventral root axons is present in a readily diffusible form.

6. Similar experiments on roots regenerating 9–10 days after crushing showed that the ACh outflow from regenerating roots was much smaller than from normal axons, although their ACh content was similar. This could have been due to more rapid sealing of the cut regenerating axons since the half‐time for the decline of the injury potential following crushing of the regenerating axons was less than half that in control roots. The alternative possibility is considered that a high proportion of the ACh might be much less diffusible than in normal axons.

7. The subcellular distribution of ACh in normal and regenerating peripheral axons is discussed.
Ventilation and sleep state in the new‐born
Authors: Bolton David P. G. , Herman Stephen
Published: December 2014

1. Ventilation, oesophageal pressure and sleep state were measured in fourteen babies between 25 hr and 7 days of age.

2. Trunk plethysmograph records showed that respiratory rate and minute volume were significantly higher in REM sleep than non‐REM sleep. Tidal volume was not significantly altered.

3. Tidal volume, respiratory rate and minute volume were all more variable in each baby in REM sleep, both on breath to breath analysis and over successive 20 sec periods.

4. Major oesophageal peristaltic activity was observed in REM sleep only.

5. In response to a sharp rise in PO2 the tidal volume and minute volume fell significantly by the same proportion in both sleep states. Respiratory rate did not change significantly.
The effect of carbon dioxide in the airways and alveoli on ventilation; a vagal reflex studied in the dog
Authors: Bartoli A. , Cross Brenda A. , Guz A. , Jain S. K. , Noble M. I. M. , Trenchard Diana W.
Published: December 2014

1. The inhalation of CO2 produces a tachypnoea only in the presence of intact vagus nerves; the present study was designed to examine the mechanism of this phenomenon in the dog.

2. Closed‐chest cardiopulmonary bypass was established in dogs weighing 16–24 kg, anaesthetized with chloralose. When the ‘bypass’ was established pulmonary blood flow ceased, PA, CO2 was reduced and the respiratory rate slowed. 3‐10% CO2 in O2 could then be inhaled without change in the level of Pa, CO2 set at the oxygenator.

3. The addition of CO2 in these concentrations to the inspired oxygen resulted in an increase in respiratory frequency, maximal at the first breath and sustained for the 1 min period of exposure. The increase in respiratory frequency was due to a shortening of expiratory duration. Inspiratory duration did not change. The response was absent after vagotomy.

4. Inert gases in O2, given as a control, had no effect on breathing.

5. The effect of raising Pa, CO2 (by increasing the concentration of CO2 in the gas equilibrating the blood in the oxygenator), was primarily to increase tidal volume.

6. The ventilatory effect of inspiring CO2/O2 mixtures was shown to be additive to the effect of raising Pa, CO2.

7. These experiments show that an afferent vagal reflex originating from the lungs causes tachypnoea, when a dog, on ‘bypass’, inhales low concentrations of CO2 in O2.