bluuebunny/crossref_metadata_2025 huggingface dataset:
Rubidium, sodium and ouabain interactions on the influx of rubidium in rat red blood cells
Authors: Beaugé L. A. , Ortíz Olga
Published: December 2014

1. The activation curve of rubidium influx by external rubidium in rat red cells showed an inflexion at a concentration around 0·2 m
M. This inflexion point was displaced to the right by ouabain.

2. The removal of sodium from the external solution changed the characteristics of the activation curve of rubidium influx. At external rubidium below 0·5 m
M the uptake increased whereas above that concentration there was marked reduction. Thus the sodium‐free effect on rubidium uptake is dependent on the external rubidium concentration.

3. With 0·25 m
M rubidium, the relationship between increase of rubidium influx and reduction of external sodium followed a more or less exponential function. All the increment was ouabain‐sensitive.

4. With a rubidium concentration above 0·5 m
M the reduction of the rubidium uptake, as sodium was removed, followed curves of complex shape. With 10 m
M rubidium, when sodium was reduced from 5 m
M to zero, there was an increase instead of a further reduction. These results suggest interactions of several effects.

5. The ouabain sensitivity of the rubidium influx in rat red cells is smaller than in other systems studied up to now. The dose—response curve was shifted to the right as the rubidium concentration increased and a plateau was obtained with rubidium only below 1 m
M at 10−5
M ouabain. When plotted as a percentage of the maximal inhibition the points fell into the theoretical curve following a simple one reactant/one site reaction.

6. Ouabain inhibition seems to be a complex function of at least three variables: the concentration of the glycoside, the concentration of sodium and the concentration of rubidium. When sodium was absent, 10 μ
M rubidium was able to prevent, to a great extent, the inhibition produced by 10−5 and 10−4
M ouabain.
The contribution by glial cells to surface recordings from the optic nerve of an amphibian
Authors: Cohen M. W.
Published: December 2014

1. The contribution by glial cells to surface recordings has been examined in the optic nerve of the amphibian Necturus maculosus. The method of current injection was employed selectively to alter the membrane potential of glial cells without affecting that of the axons. The resulting changes in potential were recorded simultaneously from the surface of the nerve using the sucrose gap method and intracellularly from a glial cell near the gap.

2. The sucrose gap method recorded 40% of the changes in glial membrane potential. This percentage was not affected when the current electrode was inserted into different glial cells while maintaining the recording conditions constant.

3. Following axonal degeneration, produced by removing the eye 2‐3 months earlier, the percentage contribution by glia increased to 84%.

4. By measuring sucrose gap responses to changes in Ko it was possible to estimate that the sucrose gap method recorded 31–60% of changes in axonal membrane potential. It was also determined that the axons, unlike glial cells, are relatively insensitive to reductions in Ko. Surface responses to decreases in external potassium thus reflect the magnitude of the glial contribution.

5. It is concluded that changes in glial membrane potential contribute about as much to surface recordings from the optic nerve of Necturus as do equivalent changes in axonal membrane potential. The contributions by the glial cells and axons are related to the relative volumes of tissue they respectively occupy. The significance of these findings to the analysis of surface recordings from the mammalian brain is discussed. Since mammalian glial cells, like those in Amphibia and the leech, become depolarized during neuronal activity and on the basis of electron microscopic evidence appear to be electrically coupled, it is likely that they contribute to the electroencephalogram.
Centrifugal inhibitory processes affecting neurones in the cat cochlear nucleus
Authors: Comis S. D.
Published: December 2014

1. Stimulation of the lateral part of the olivary S‐segment in the cat inhibited neurones in the ipsilateral cochlear nucleus. A smaller number of neurones located in the ventral division of the cochlear nucleus were excited.

2. It is suggested that inhibition in the ipsilateral cochlear nucleus may be mediated directly by fibres making synaptic connexions on the cochlear nucleus neurones, or indirectly by inhibitory fibres acting at the cochlea.

3. The direct inhibitory process at the cochlear nucleus is unaffected by strychnine, whereas the inhibitory process at the cochlea is abolished by strychnine.

4. A cochlear nucleus neurone can be influenced simultaneously by excitatory and inhibitory processes.
Effects of cholinergic and adrenergic blocking agents on the activity of the eccrine sweat glands
Authors: Foster K. G. , Weiner J. S.
Published: December 2014

1. The effects of blocking agents on the responsiveness of the cast' pad and human forearm sweat glands have been studied.

2. Of the anti‐adrenergic substances examined (dibenamine, phenoxybenzamine, bretylium, guanethidine and phentolamine) only high doses of guanethidine and phentolamine produced any consistent and significant measure of blockade, and small doses of atropine were as effective as these large doses of guanethidine or phentolamine.

3. It is concluded from the blockade of chemical stimulation as well as transmission by these substances that (1) there are only cholinergic fibres innervating eccrine sweat glands, and (2) any inhibitory action by anti‐adrenergic substances is due to interaction with cholinergic receptors in the glands.
Estimates of probability of transmitter release at the mammalian neuromuscular junction
Authors: Christensen B. N. , Martin A. R.
Published: December 2014

1. Intracellular records of end‐plate potentials (e.p.p.s) were obtained from curarized neuromuscular junctions in the rat diaphragm.

2. Statistical estimates of the quantal release probability (p) were made at individual junctions from measurements of the means and variances of e.p.p. amplitudes at two different levels of Ca concentration. It was assumed that the release process was binomial and that the number of quanta available for release (n) was independent of external Ca.

3. These estimates of p were compared with those obtained by measuring depression of e.p.p. amplitudes after single conditioning shocks and assuming that the depression was due to depletion of n. The statistical estimates were consistently smaller.

4. This disparity, plus the additional observation that depression was not linearly related to the number of quanta released by one or more conditioning shocks, suggested that depression was not due entirely to depletion and that the depletion assumption led to an over‐estimate of p.

5. A third method of estimating p from measurements of the decline of e.p.p. amplitudes during rapid stimulation also appeared to result in an over‐estimate.
Effects of cations on prolactin and growth hormone secretion by rat adenohypophyses in vitro
Authors: Parsons J. A.
Published: December 2014

1. Explants of rat adenohypophyses were incubated in medium 199, Earle's saline, or modified Earle's saline (K‐Earle's) with different calcium, magnesium, sodium and potassium concentrations for 4‐6 hr at 37° C in 5% CO2 in O2.

2. The amount of prolactin and growth hormone in explants and in medium was estimated by disk electrophoresis and densitometry.

3. Low calcium inhibited prolactin secretion by 40–60%. Low magnesium and slightly increased (5×) magnesium (4·1 m
M) did not influence prolactin secretion in either 1·8 m
M or low calcium, but 10 and 20 m
M magnesium inhibited secretion by 50 and 70%, respectively. Inhibition of prolactin secretion by high magnesium was reversible.

4. Decreasing sodium by 80% had no effect on prolactin secretion, but low sodium inhibited the sustained, although not acute, secretion of this hormone.

5. Low potassium did not affect the secretion of either prolactin or growth hormone. Increased potassium (32 or 54 m
M) slightly stimulated prolactin secretion by adenohypophyses of males but had no effect on the secretion of this hormone by female glands.

6. In 1·8 m
M calcium, growth hormone secretion by pituitaries of males and females was markedly stimulated by increased potassium, but it was not appreciably affected by high potasium in low calcium. Increased potassium did not stimulate growth hormone secretion in medium containing low sodium with normal calcium.

7. Secretion of prolactin and growth hormone by rat adenohypophyses is dependent upon calcium, but only growth hormone secretion is markedly stimulated by increased potassium. The difference in responsiveness to increased potassium, between the somatotrophs and lactotrophs, may be related to the predominant mode of hypothalamic control of these hormones.
The relation between calcium and contraction kinetics in skinned muscle fibres
Authors: Podolsky R. J. , Teichholz L. E.
Published: December 2014

1. Segments of skinned frog muscle fibres were immersed in solutions in which the calcium ion concentration, and therefore the steady isometric force, was controlled with an EGTA buffer system. The contraction kinetics were measured when the load was quickly reduced to values less than the isometric force.

2. The velocity of shortening following release from steady force was a hyperbolic function of relative load. The minimum quick displacement required to reduce the force from the steady isometric value to half this value was about 1% of the fibre segment length.

3. The relative force—velocity relation was independent of pCa in the range 5·0–6·75. Thus calcium ions appear to control the number of sites at which cross‐bridges can be formed but have no significant effect on the kinetic properties of an individual bridge.

4. Cross‐bridges along the length of a myofilament appear to act independently of each other.

5. The force—velocity relations reported for intact muscle fibres during relaxation, when compared with those of skinned fibres at different calcium levels, indicate that the time course of the fall in force after a stimulus is essentially that of calcium removal from the myofilaments.
Consumption of kininogen in the submandibular salivary gland when activated by chorda stimulation
Authors: Gautvik K. M. , Hilton S. M. , Torres Sonia H.
Published: December 2014

1. A method is described for determination of kininogen 1 (substrate mainly for plasma kallikrein) and kininogen 2 (substrate for glandular kallikrein) independently in cat plasma.

2. In anaesthetized cats the arterial inflow to, and venous outflow from, the submandibular salivary gland were isolated: a roller pump giving constant volume inflow was interposed in the arterial circuit.

3. Venous blood was collected at rest, during and after stimulation of the chorda tympani, and its content of kininogens 1 and 2 were estimated. Kininogen 2 was reduced up to 60% by chorda stimulation, whereas the level of kininogen 1 was unchanged.

4. On close arterial infusion of bradykinin or histamine in amounts which produce large vascular effects, including increased capillary permeability, the venous blood levels of both kininogens 1 and 2 were unchanged.

5. It is concluded that the selective loss of kininogen 2 on chorda stimulation results from the release of kallikrein into the tissue spaces and reflects the extent of kinin formation within the gland.
Effect of environmental temperature on the turnover of 5‐hydroxytryptamine in various areas of rat brain
Authors: Simmonds M. A.
Published: December 2014

1. Rats were exposed to environmental temperatures of 9, 24 or 32° C and the turnover of 5‐hydroxytryptamine (5‐HT) was estimated in various areas of brain by two different methods in separate series of experiments. In the first method, small amounts of tritium labelled 5‐HT, [3H]5‐HT, were injected into the c.s.f. in order to label radioactively the endogenous 5‐HT in the brain. The rates of disappearance of [3H]5‐HT from discrete areas of brain were taken as indices of the rates of turnover of endogenous 5‐HT in these areas. In the second method, the rate of accumulation of endogenous 5‐HT after inhibition of monoamine oxidase by pargyline was taken as an estimate of 5‐HT turnover.

2. The results obtained by each method were in agreement. The turnover of 5‐HT increased with increasing environmental temperature from 9 to 32° C in specific brain areas. During the first hour of exposure to 32° C, the turnover of 5‐HT increased in the preoptic area, hypothalamus and cortex + hippocampus, but not in striatum or midbrain. During the subsequent 2 hr at 32° C, however, the turnover of 5‐HT in the preoptic area and hypothalamus fell while that in the striatum showed a delayed rise.

3. It is concluded that 5‐HT is involved in several different cerebral pathways which increase their activity upon exposure of the rat to heat. These pathways are not located exclusively in the preoptic area and hypothalamus.
Stimulus—response curves for the pulmonary vascular bed to hypoxia and hypercapnia
Authors: Barer Gwenda R. , Howard P. , Shaw J. W.
Published: December 2014

1. In anaesthetized open‐chest cats and dogs, blood flow and gas tensions were measured in a circuit inserted into a pulmonary vein while ventilating the lobe which it drained with low O2 and high CO2 mixtures.

2. Both hypoxic and hypercapnic mixtures caused a reduction in blood flow from the lobe.

3. Stimulus—response curves relating blood flow to pulmonary venous PO2 and PCO2 were obtained. Those for hypoxia were usually asymptotic in shape; the curves became steep below 100 torr and flow sometimes fell to zero. The mean reduction in blood flow for every 20 torr fall in PO2 was 15·7% in cats and 11·8% in dogs. Those for hypercapnia were steep at first but levelled out at high PCO2 values; the maximum reduction in flow was 40–60% as vasoconstriction was only observed over a limited PCO2 range.

4. Hypoventilation of the lobe led to a reduction in blood flow. This was mainly attributable to hypoxia though other factors such as hypercapnia may sometimes have contributed.

5. Total occlusion of the bronchus of an O2‐filled lobe caused blood flow to fall in two phases. The first phase could be attributed to a rise in PCO2 and the second to a fall in PO2.

6. The results confirm the hypothesis that hypoxia is an important factor regulating local blood flow in relation to local ventilation.
Thyroxine utilization in the new‐born lamb
Authors: Nathanielsz P. W.
Published: December 2014

1. From previous studies on foetal thyroid function in various mammalian species it would appear that the foetal pituitary—thyroid axis is capable of function before birth. Few studies are available to indicate the level of function before birth and in the immediate post‐natal period.

2. Plasma thyroxine levels, thyroxine pool and utilization rate of thyroxine have been followed in new‐born Welsh mountain lambs from birth to 39 days of age.

3. Plasma thyroxine levels are high within the first hour of life after birth (18·2 ± 2·0 μg/100 ml.) and fall steadily to a minimum of 5·1 ± 1·1 on day 11 and 12 of post‐natal life. Thereafter they fluctuate about a mean of 6·1 μg/100 ml. The significance of these changes is discussed in respect to foetal thyroxine levels, placental permeability to thyroxine, and foetal and neonatal thyroid and pituitary function.

4. Thyroxine utilization rate is high both in absolute terms and relative to unit body weight on days 1‐4 of post‐natal life. The utilization rate/kg remains fairly constant from days 10–39 of post‐natal life.

5. Thyroxine utilization in the new‐born lamb is compared with that in the new‐born calf in which the post‐natal growth curve is very different.

6. The various factors such as levels of free thyroxine, diet and environmental changes which influence thyroxine utilization are discussed and the rate of utilization is compared with other indices of thyroid function in new‐born and adult animals of different species.
Effect of stimulation and hyperpolarization on non‐electrolyte and sodium permeability in perfused axons of squid
Authors: Hidalgo Cecilia , Latorre Ramón
Published: December 2014

1. The permeability for micro‐injected [3H]ethylene glycol was measured in resting state and during stimulation at 100/sec in squid giant axons. No detectable changes during electrical activity were observed.

2. The influxes of urethane, tritiated water, ethylene glycol, urea and sodium were measured in internally perfused squid axons. Ethylene glycol and urea influxes were determined simultaneously with sodium influxes. The electrical stimulation of the fibre produced an increase in the influx of sodium but did not alter the influxes of the non‐electrolytes listed above.

3. Experiments were done with the combined voltage clamp—perfusion technique. The influxes of ethylene glycol and sodium were simultaneously measured in resting state and during maximum sodium current under stimulation at 10/sec. The influx of sodium increased in these conditions but the influx of ethylene glycol remained constant. In some experiments, the fibre was hyperpolarized to 10 or 20 mV, above the resting potential and the influxes of ethylene glycol and sodium were measured. The sodium influx decreased to 60% at 20 mV above the resting potential whereas the influx of ethylene glycol remained constant.

4. These results indicate that in the giant axons of the squid Dosidicus gigas, sodium and non‐electrolytes fluxes are not coupled.
The role of hypothalamic temperature in the control of panting in the chicken exposed to heat
Authors: Richards S. A.
Published: December 2014

1. In unanaesthetized chickens, the temperatures of the hypothalamus, colon and skin have been recorded in relation to the onset and cessation of thermally induced panting.

2. During control conditions, hypothalamic temperature showed fluctuations associated with arousal and movement. It was lower than colonic temperature by about 0·9° C but this difference generally decreased during exposure to heat.

3. When the birds were exposed abruptly to 40° C, or to ambient temperatures increasing gradually from 20 to 52° C, there was a delay of 15–65 min and marked increases in both peripheral and central body temperatures before panting commenced.

4. Infra‐red irradiation of the thorax and abdomen caused vasodilatation in the comb and toe before detectable increases in the deep body temperatures. Increasing the colonic temperature by up to 2° C did not cause panting until hypothalamic temperature was also raised. This inhibitory effect of normal hypothalamic temperature was enhanced by low ambient temperature.

5. Infra‐red irradiation of the head increased hypothalamic temperature by up to 3·5° C and caused vasodilatation in the toe without changes in colonic temperature. Panting, however, did not occur so long as colonic temperature was within the normal range. The inhibitory effect of normal colonic temperature was again enhanced by low ambient temperature.

6. In anaesthetized chickens, selective heating of the head and body caused panting only after increases in both the hypothalamic and colonic temperatures.

7. Repeated exposure of birds to 40° C did not reduce the time delay before panting started.

8. It is concluded that panting in the fowl requires an increase in some extracranial deep body temperature as well as in that of the hypothalamus.
The effect of progressive hypoxia on the respiratory and cardiovascular systems of the pigeon and duck
Authors: Butler P. J.
Published: December 2014

1. During the initial stages of progressive hypoxia in ducks and pigeons (Pa, O2 100 → 60 mm Hg) there were no significant changes in heart rate, blood pressure or oxygen uptake, but respiratory frequency increased.

2. As hypoxia became more profound (Pa, O2 60 → 30 mm Hg), there was a significant tachycardia, and blood pressure fell slightly in both animals. Respiratory frequency continued to increase in both species, and ducks were able to maintain their oxygen uptake at control levels at a lower Pa, O2 than pigeons.

3. The response to progressive hypoxia of pigeons and ducks was compared with that of the domestic fowl. The former two birds could maintain control of their cardiovascular system at a lower environmental oxygen concentration than the latter. Arterial PO2 followed a similar course in all three birds in relation to environmental oxygen content. Pigeons and ducks were therefore able to endure a lower arterial PO2 than chickens.
The binding of thyroid hormones to phospholipid membranes
Authors: Hillier A. P.
Published: December 2014

1. Thyroxine and tri‐iodothyronine are bound by liposomes (bimolecular phospholipid membranes produced by dispersing egg‐yolk lecithin in water). At pH 7·4 the ‘partition coefficient’ between water and the phospholipid is 1·2 × 104 for thyroxine and 2·2 × 104 for tri‐iodothyronine. The partition coefficient falls off rapidly in more alkaline solutions as the phenolic group on the hormones becomes ionized.

2. The binding of thyroxine by membranes is very rapid, occurring at rates equivalent to those found in the binding of thyroxine by serum.

3. Lecithin membranes are readily permeable to thyroxine (the oil:water partition coefficient is 1·7).

4. The binding of thyroid hormones by perfused rat hearts and the binding of thyroid hormones by liposomes are similar in their sensitivity to pH. Simple alcoholic extracts of tissues have strong thyroxine‐binding activity.

5. These results are discussed in relation to the nature and function of the tissue thyroxine‐binding reaction.
The range and scope of binocular depth discrimination in man
Authors: Blakemore Colin
Published: December 2014

1. Depth discrimination, using disparity cues alone, was studied with a small fixation point and briefly exposed, vertical slit‐shaped targets.

2. The upper limit for reliable qualitative localization of a slit as nearer or further than the fixation point is 4‐7 deg of absolute disparity in a convergent direction and 9–12 deg in a divergent direction. Even larger absolute disparities can be recognized in the peripheral visual field.

3. Relative depth discrimination between two slit targets was measured as a function of their spatial position. The horopter (the locus of targets that appear to be fused binocularly) is the region of maximum stereoacuity and this does not necessarily coincide with the Vieth—Müller circle (the locus of zero geometric or absolute disparity). There is a gradual increase in stereo‐threshold as the targets are moved out along the horopter, away from the fixation point into the peripheral visual field. The relative disparity threshold also rises, approximately exponentially, as the targets are moved in depth or absolute disparity away from the horopter.

4. Relative depth discrimination is, then, operative over a very wide band of visual space around the horopter (about 3 deg of absolute disparity in the centre of the visual field and even more in the periphery).

5. The findings are discussed in relation to the neurophysiology of binocular neurones of the cat cortex. The dimensions of visual space under observation by the binocular apparatus of cat and man are rather similar. The sharper decline of stereo‐acuity with absolute disparity in the centre of the visual field may be related to the limits of bilateral representation of a central strip of retina in the human brain.
Slow changes in membrane permeability and long‐lasting action potentials in axons perfused with fluoride solutions
Authors: Chandler W. K. , Meves H.
Published: December 2014

1. Voltage clamp experiments were carried out on squid giant axons which were perfused internally with 300 m
M‐NaF + sucrose and placed in K‐free artificial sea‐water at 16–17° C. On stepwise depolarization (V = −38·5 to 68 mV) the Na conductance gNa rapidly reached a peak value and then declined to a new level; this ‘maintained’ level was slowly inactivated in an exponential manner with a rate constant which varied from 0·3 to 1·1 sec−1. This process was not influenced appreciably by replacing 50 m
M‐NaF with KF.

2. On repolarization to a potential which varied between −73 and −101 mV the slow inactivation was removed with a rate constant of 0·11–0·73 sec−1.

3. Prolonged depolarization also produced a slow inactivation of the ability of the membrane to give a transient increase in gNa. This effect developed at a rate about ⅓‐½ that associated with the inactivation of the ‘maintained’ component; on repolarization, recovery of the peak gNa was 1–2 times as fast as recovery of the ‘maintained’ gNa.

4. In experiments on fibres perfused with 300 m
M‐KF after internal NaF had removed the usual delayed K conductance, depolarization resulted in an outward current which developed in an exponential manner with a time constant of a fraction of a second. The equilibrium potential for this component was more negative than −50 mV.

5. Long‐lasting action potentials were computed on the basis of the above slow changes and, except for the period of final repolarization, were found to be in satisfactory agreement with experimental records. The discrepancies suggest that there may be additional slow changes in permeability which could not be resolved in the present experiments.
Electrophysiological studies of neuromuscular transmission in hereditary ‘motor end‐plate disease’ of the mouse
Authors: Duchen L. W. , Stefani E.
Published: December 2014

1. Studies have been made on isolated nerve—muscle preparations from mice with hereditary ‘motor end‐plate disease’.

2. Spontaneous fibrillation was observed in the isolated preparation.

3. Muscles gave only a weak twitch or failed to contract in response to nerve stimulation. Direct stimulation of muscles caused a twitch response which had a slower time course than normal. Peripheral nerve conduction was normal.

4. Intracellular recording from single muscle fibres showed that with longer survival of the animal an increasing proportion of fibres failed to show end‐plate potentials or action potentials in response to nerve stimulation.

5. Miniature end‐plate potentials (m.e.p.p.s) were recorded in almost all muscle fibres including those in which neuromuscular transmission had failed. The frequency of m.e.p.p.s was greater than normal, was not increased by tetanic stimulation of the nerve but was increased by a raised external potassium concentration.

6. Muscle fibres were supersensitive to acetylcholine.

7. The results suggest that the muscular weakness in this disease is due to the failure of nerve action potentials to invade motor nerve terminals so that muscle fibres become ‘functionally denervated’.
Effects of mecamylamine on responses of carotid body chemoreceptors in vivo to physiological and pharmacological stimuli
Authors: Sampson S. R.
Published: December 2014

1. Effects of mecamylamine on the spontaneous discharge rate of afferent fibres of carotid body chemoreceptors in vivo and their responses to ACh, NaCN, HCl and hypoxia were studied in sixteen cats.

2. Cats were anaesthetized with sodium pentobarbitone, paralysed with gallamine triethiodide and artificially ventilated. Chemoreceptor excitants were injected into the common carotid artery; mecamylamine was given intravenously.

3. Mecamylamine, 230 μg/kg or greater, failed to diminish either the rate of spontaneous discharge of carotid body chemoreceptors at high arterial oxygen tensions (greater than 130 mm Hg), or the responses of these receptors to NaCN (0·5–25 μg), HCl or hypoxic blood.

4. Responses of chemoreceptor afferent fibres to ACh (1·0–50 μg) in the same preparations were either completely abolished or considerably reduced by mecamylamine.

5. These data do not support the hypothesis of a cholinergic mechanism for the initiation of chemosensory discharges in the carotid body, either at rest or in response to stimuli such as NaCN, acid or hypoxia.
Passive vasodilatation of the hind limb after sympathetic preganglionic stimulation
Authors: Lioy Franco , Polosa Canio
Published: December 2014

1. The post‐vasoconstriction dilatation (PVCD) observed after release of carotid clamping has been attributed to baroreceptor stimulation. However, PVCD has been observed in baroreceptor deafferented animals following cessation of stimulation of the diencephalon or of chemoreceptor fibres.

2. The effects of preganglionic (ventral roots) and post‐ganglionic (sciatic nerve) stimulation upon the vascular resistance of the hind limb of anaesthetized cats and dogs was investigated. The limb was vascularly isolated and perfused at constant flow with the animal's own arterial blood. The animals were atropinized and neuromuscular block was obtained with gallamine triethiodide.

3. PVCD was observed upon cessation of stimulation of intact preganglionic fibres or of their peripheral stump.

4. PVCD was dependent upon the existence of neurogenic vasomotor tone in the vessels, but independent from baroreceptor influences.

5. PVCD was never observed after cessation of stimulation of the post‐ganglionic fibres.

6. Similar results were obtained after removal of the skin of the perfused limb.

7. The possibility that the post‐vasoconstriction dilatation observed in these experiments is due to the existence of a preganglionic inhibitory system is discussed.
Vasoactive hormones in endotoxin shock: A comparative study in cats and dogs
Authors: Hall R. C. , Hodge R. L.
Published: December 2014

1. Entamoeba coli endotoxin was administered intravenously to cats and dogs.

2. The changes in circulating levels of catecholamines and angiotensin following endotoxin were assayed by a continuous superfusion technique.

3. The response of the dog was characterized by an immediate sustained rise in angiotensin levels and a later variable rise in catecholamine levels.

4. The response of the cat was characterized by an early rise in catecholamine levels and a later rise in angiotensin levels.

5. It is concluded that this species difference may reflect the relative importance of renin‐angiotensin and sympatho‐adrenal systems of dogs and cats, respectively.
Cardiovascular responses to salt‐loading in conscious domestic geese
Authors: Hanwell Ann , Linzell J. L. , Peaker M.
Published: December 2014

1. The intravenous injection of large volumes of 0·5
M‐NaCl that are usually used to induce nasal gland secretion in marine birds has been shown in geese to increase greatly plasma volume, cardiac output, heart rate and stroke volume at the time secretion commences after 2‐8 min.

2. There were no consistent changes in mean arterial blood pressure or in the distribution of the cardiac output to major organs except to the salt‐glands whose share increased approximately fourteenfold. Salt‐gland blood flow remained high for 10–20 min after cardiac output and heart rate had returned to nearly normal levels.

3. The increases in plasma volume and venous return are unlikely to be the stimuli for salt‐gland secretion because secretion was also initiated by giving artificial sea water into the proventriculus and this produced no changes in these variables at the time secretion commenced, 5‐14 min later.

4. At the start of secretion in orally loaded birds, the only detectable changes in the plasma were small increases in osmolality (from 1·3 to 4·6%), Na (from 0·3 to 6%) and Cl (from 1·3 to 7·1%) concentrations.
Experiments on the liberation of phosphate from the muscles of the human forearm during vigorous exercise and on the action of sodium phosphate on forearm muscle blood vessels
Authors: Barcroft H. , Foley T. H. , McSwiney R. R.
Published: December 2014

1. During vigorous sustained or rhythmic exercise of the forearm muscles, plasma phosphate in the venous effluent from the active muscles increased by about 20%.

2. The forearm muscles liberate phosphate during vigorous activity. This confirms observations made by Hilton & Vrbová (1970) on fast muscles in the cat.

3. Infusions of sodium phosphate into the brachial artery which raised plasma phosphate in the venous effluent from the resting muscles by 400% had no effect upon the rate of the forearm blood flow.

4. These results do not suggest that the liberation of phosphate plays any significant part in mediating the vasodilatation accompanying vigorous exercise of the muscles in the forearm.
Effects of hexoses and anions on the erythritol permeability of human red cells
Authors: Wieth Jens Otto
Published: December 2014

1. The effect of hexoses and of the anions chloride, thiocyanate, and salicylate on the permeability of human red cells to [14C]erythritol has been studied.

2. It was confirmed that erythritol competes with glucose, mannose, and galactose for the hexose transfer system of the red cell membrane. Approximately 25% of the erythritol influx was insensitive to the presence of hexoses or phloretin. Identical maximum degrees of inhibition were obtained with 0·3
M glucose and with phloretin (0·5 × 10−3
M). In the absence of competing inhibitors the erythritol permeability, P, was 1·2 × 10−7 cm/sec at 38° C. At maximum inhibition P was 0·3 × 10−7 cm/sec.

3. Erythritol is able to penetrate the membrane by two pathways, only one of which is sensitive to hexoses. Both hexose‐sensitive and hexose‐insensitive erythritol influx are well described by first‐order diffusion kinetics. The affinity of erythritol for the hexose transfer system is very low, and the half saturation constants of hexoses can be determined from their ability to retard erythritol permeation. The following values were found for the half saturation of the transport system with hexoses at 38° C: glucose 6 m
M, mannose 11 m
M, and galactose 40 m
M.

4. Thiocyanate and salicylate reduce the hexose‐sensitive fraction of erythritol influx, but the hexose‐insensitive erythritol permeability is not affected when chloride is replaced by the foreign anions. This applies to the whole temperature range between 0 and 38° C, where the ionic permeabilities of red cells have been shown to be profoundly changed by thiocyanate and salicylate.
The transformation of myosin in cross‐innervated rat muscles
Authors: Bárány M. , Close R. I.
Published: December 2014

1. The characteristics of isometric twitch and tetanic contractions have been determined for normal (N‐EDL, N‐SOL), self‐innervated (S‐EDL, S‐SOL) and cross‐innervated (X‐EDL, X‐SOL) extensor digitorum longus (EDL) and soleus (SOL) muscles of the rat at 35° C. The muscles were then used for biochemical analyses of properties of myosin and actomyosin.

2. The ATPase activities of myosin and actomyosin of X‐EDL decreased to the level of those of N‐SOL or S‐SOL, and the ATPase activities of X‐SOL approached those of N‐EDL or S‐EDL. Of the various ATPase activities, the actin‐ and Mg2+‐activated ATPase activity of myosin and the Mg2+‐activated ATPase activity of actomyosin showed the highest degree of correlation with the intrinsic speed of shortening of the muscles.

3. Myosin of normal, self‐innervated, and cross‐innervated muscles combined with F‐actin superprecipitated at rates which were proportional to the speed of muscle contraction.

4. The pH profile curve and the ATP‐induced dinitrophenylation reaction revealed that the structure of myosin of X‐EDL was altered to that of N‐SOL or S‐SOL, and the structure of myosin of X‐SOL was modified to that of N‐EDL or S‐EDL.

5. No differences were found in the yield of myosin of normal, self‐innervated, and cross‐innervated extensor digitorum longus and soleus muscles.
The distribution of cutaneous receptors in the rabbit's hind limb and differential electrical stimulation of their axons
Authors: Brown A. G. , Hayden R. E.
Published: December 2014

1. The receptive field properties and conduction velocities of single dorsal root axons, activated from the sural and cutaneous branches of the posterior tibial (medial plantar) nerves, were examined in anaesthetized rabbits.

2. The sural nerve sample included all types of units previously recorded from the saphenous nerve (Brown & Iggo, 1967). In particular it was shown that electrical stimulation of the sural nerve at strengths up to 1·3T produced a volley of impulses in a pure population of slowly adapting units (Type I units).

3. The medial plantar sample showed an absence of Type I slowly adapting units and Type T hair follicle units. Corresponding to this there were no touch corpuscles or tylotrich hairs in the skin of the hind foot and the fastest medial plantar axons conducted at 60–70 m/sec as opposed to 80–85 m/sec for the sural nerve. Stimulation of the medial plantar nerve at stimulus strengths close to threshold produced a volley of impulses in a nearly pure population of Type G hair follicle units.
Correlation between nerve terminal size and transmitter release at the neuromuscular junction of the frog
Authors: Kuno M. , Turkanis S. A. , Weakly J. N.
Published: December 2014

1. End‐plate potentials were recorded intracellularly at the frog neuromuscular junction bathed in a solution containing a low concentration of calcium and a high concentration of magnesium.

2. The muscle was subsequently subjected to ‘cholinesterase staining’, and the area of the individual end‐plates, studied with intracellular electrodes, was measured.

3. A positive correlation was found between the end‐plate area and the diameter of muscle fibres.

4. The mean quantum content (m) showed a positive correlation with the size of end‐plates.

5. The frequency of spontaneous miniature end‐plate potentials was positively correlated with m as well as with end‐plate area.

6. It is concluded that the amount of transmitter released following nerve stimulation is related to the size of nerve endings.
The action of nerveside, a peptide extracted from brain, on myenteric ganglia in Auerbach's plexus
Authors: Soh N. M. , Toh C. C.
Published: December 2014

1. In the rabbit jejunum nerveside causes alternating contractions of the longitudinal and circular muscles, which are similar to the peristaltic reflex produced by distension of the gut. These effects are abolished by dibucaine (Nupercaine) and tetrodotoxin. The site of action is located in Auerbach's plexus.

2. Circular muscle contractions due to nerveside are blocked by hexamethonium, nicotine, morphine, atropine and hyoscine. There is no circular response to nerveside after removal of Auerbach's plexus. It is suggested that nerveside acts by stimulating presynaptic nerve terminals which are cholinergic and that the circular muscle is innervated by cholinergic nerve fibres.

3. Longitudinal muscle contractions due to nerveside are not affected by hexamethonium but can be blocked by paralysis of myenteric ganglia with nicotine. They are not abolished by morphine or by cholinolytic drugs. It is suggested that nerveside acts by stimulating either receptors insensitive to acetylcholine in ganglion cells or non‐cholinergic presynaptic nerve terminals. It is further suggested that the longitudinal muscle of the rabbit gut is supplied by non‐cholinergic as well as cholinergic nerve fibres.
Geometrical illusions and the response of neurones in the cat's visual cortex to angle patterns
Authors: Burns B. Delisle , Pritchard Roy
Published: December 2014

1. This report describes the responses of thirty‐six single neurones in the primary visual area of the cat's neurologically isolated and unanaesthetized forebrain, to movements of thin white lines across the visual field. The experiments were designed to record the effects upon the response to a single test line of an added line, which was either parallel to the test line or joined it, making an angle‐pattern of 30°. Unit responses were measured in terms of the peak probability of firing derived from a post‐stimulus histogram.

2. All of the cortical neurones tested exhibited a preferred orientation for stimulation by the test line, i.e. an orientation of the line which produced a maximal response when the line passed through the centre of the unit's receptive field.

3. There was no evidence that the orientation of a single test line preferred by cortical neurones was different from that preferred by the same cell when excited by an angle pattern, one arm of which was the original test line.

4. The position of a test line (with preferred orientation) in the visual field that produced a maximal response from cortical neurones, was not always the same as the position for maximal response, when a second line was added to make either an angle pattern or to make a pattern of two parallel lines.

5. Where the two lines of these patterns were close together and separated by less than the radius of the receptive field, the position for maximal response to the test line was shifted towards the added line. Where the two lines were further apart than this but separated by less than a receptive field diameter, the optimal position for the test line was displaced away from the added line.

6. Some evidence was found of a lateral inhibition in the visual system, sufficient to account for the displacements described in paragraphs 4 and 5 above.

7. It is concluded that the tip of an angle pattern of 30° produces a distorted cortical image within the primary visual area.

8. This neural distortion of sensory information seems adequate to explain the well known illusions of orientation that are associated with human perception of patterns containing acute angles.
The mechanical and thermal properties of frog slow muscle fibres
Authors: Floyd K. , Smith I. C. H.
Published: December 2014

1. A study has been made of the mechanical behaviour and the heat production of frog slow muscle fibres in iliofibularis nerve—muscle preparations at 20° C.

2. The slow fibre isometric tension and its rate of development increase with stimulation frequency, the increases beyond 30 Hz being relatively small. Relaxation rate also increases with stimulation frequency. The tension—length curve and maximum isometric tension (250 mN.mm−2) are similar to those of twitch fibres. The maximum shortening velocity is estimated to be 0·11 tonus bundle lengths per second.

3. For contractions up to 60 sec at 30–50 Hz the slow fibre heat rate is steady at 6 mJ.g−1.sec−1. Slow fibres produce aerobic recovery heat with a time course similar to that of twitch fibres.

4. The accuracy of the results is discussed, and a comparison is made with the properties of twitch fibres. It is concluded that the tension‐producing reactions are thirty times slower in the slow fibres.
The functional organization of the parasympathetic secretory innervation of the submandibular gland
Authors: Ekström J. , Emmelin N.
Published: December 2014

1. In cats the hypoglossal and chorda‐lingual nerves were cut and their central ends sewn to the peripheral end of the latter nerve. At monthly intervals the sensitivity of the submandibular gland to a secretory agent was then estimated.

2 When the supersensitivity resulting from the decentralization of the gland had been lowered to a constant level acute experiments were made. Electrical stimulation of both nerves caused secretion, which was abolished by ganglion blocking drugs and atropine.

3. Simultaneous stimulation of the nerves at frequencies subliminal for each nerve did not cause any secretion.

4. Stimulation of one nerve at a subliminal frequency did not increase a flow of saliva evoked by stimulation of the other nerve. However, as soon as the secretory threshold was reached, the flow was markedly accelerated, provided it was submaximal.

5. In many cases stimulation of the regenerated chorda fibres at a high frequency caused a flow corresponding to the maximal secretory capacity of the gland. In some experiments this was true for the hypoglossal fibres also.

6. The functional organization of the parasympathetic secretory innervation of the submandibular gland of the cat is discussed in the light of these observations.
The inotropic and chronotropic effects of catecholamines on the dog heart
Authors: Furnival C. M. , Linden R. J. , Snow H. M.
Published: December 2014

1. The chronotropic and inotropic responses of the denervated dog heart to intravenous infusions of noradrenaline, adrenaline and isoprenaline were studied.

2. The maximum rate of rise of pressure in the left ventricle of the heart, (dP/dt max) measured at a constant heart rate and mean systemic arterial pressure during each series of infusions, was used as an index of inotropic changes (Furnival, Linden & Snow, 1970).

3. The order of potency of the catecholamines in producing both chronotropic and inotropic effects was isoprenaline > adrenaline > noradrenaline.

4. For the same increase in heart rate produced by an infusion of a catecholamine, noradrenaline caused a greater inotropic effect than adrenaline, which in turn caused a greater increase than isoprenaline.

5. The chronotropic and inotropic effects of noradrenaline were potentiated by an intravenous injection of cocaine HCl (5 mg/kg), whereas those of isoprenaline were unchanged.

6. The relative difference between the responses to noradrenaline and isoprenaline was abolished by an intravenous injection of cocaine HCl.

7. It is concluded that the different relative chronotropic and inotropic effects of isoprenaline and noradrenaline are due to the greater uptake of noradrenaline by sympathetic nerve endings in the sinu‐atrial node than in the muscle of the left ventricle.
Effect of mitosis inhibitors on blood platelet microtubules and aggregation
Authors: Sneddon John M.
Published: December 2014

1. An inhibitory action of the mitosis inhibitors colchicine, colcemid and vinblastine on blood platelet aggregation has been demonstrated.

2. The inhibitory action of low concentrations of these drugs was surmountable by increasing the concentration of the aggregating agents adenosine diphosphate (ADP) or thrombin. High concentrations completely inhibited aggregation.

3. The presence of a circumferential bundle of microtubules has been demonstrated in rabbit platelets.

4. After exposure to aggregating doses of ADP and thrombin the microtubules move to the centre of the cell, ‘trapping’ the platelet intracellular organelles in a relatively clear cytoplasm.

5. Concentrations of the antimitotic agents which reduce platelet aggregation depolymerize the platelet microtubules and prevent the rearrangement of the platelet organelles during aggregation.

6. It is suggested that the microtubules are not essential for platelet aggregation but are intimately involved in the movement of intracellular granules. This may be a preliminary stage in the eventual discharge of the granules during the platelet ‘release reaction’.