bluuebunny/crossref_metadata_2025 huggingface dataset:
Motor activity following the silent period in human muscle
Authors: Alston W. , Angel R. W. , Fink F. S. , Hofmann W. W.
Published: December 2014

1. When a muscle is unloaded during voluntary contraction, there is normally a silent period in the electromyogram. The silence is terminated by a sudden return of muscle action potentials.

2. In order to investigate the mechanism of the terminal motor volley, the unloading reflex was studied in six human subjects. The independent variables were the initial muscular force, the inertia of the limb and the amount of motion permitted. The dependent variables were the size and latency of the terminal volley.

3. During isometric contraction, the amplitude of the surface‐recorded muscle action potentials increased monotonically with increasing muscular tension.

4. The action potentials were significantly larger during the terminal volley than during the period before unloading.

5. When acceleration of the limb was reduced by increasing the inertia, the terminal volley was decreased in size, but the latency was not affected.

6. When movement was interrupted by a mechanical block, the latency of the terminal volley was reduced, but the size was not affected.

7. The results suggest that the terminal motor volley is not the result of a decrease in Renshaw feed‐back or in autogenetic inhibition.

8. The motor volley must be regulated by proprioceptive feed‐back, because it is affected by the velocity and displacement of the limb.

9. The muscle frequently responded within 20 msec after motion of the limb was blocked. Hence it appears that the mechanism involves a spinal reflex.

10. Because the motor discharge occurs while the muscle is shortening, it cannot be an ordinary stretch reflex. If the discharge is attributed to spindle afferent driving, one must assume that the gamma motor neurones are active during the silent period.

11. The authors postulate a fusimotor reflex, which is driven by afferent impulses from the moving limb and excites the alpha motoneurones by way of the ‘gamma loop’.
Some observations on ‘autoregulatory escape’ in cat intestine
Authors: Baker Rosemary , Mendel D.
Published: December 2014

1. ‘Autoregulatory escape’ (Folkow, Lewis, Lundgren, Mellander & Wallentin, 1964a) in which intestinal blood flow escapes from the constrictor influence of splanchnic nerve stimulation, was investigated in the cat. Measurements were made of intestinal blood flow, movements and portal venous pH and oxygen content.

2. ‘Autoregulatory escape’ was observed with sympathetic nerve stimulation and noradrenaline infusion. It did not occur during haemorrhage.

3. The recovery of flow during noradrenaline infusion could not be explained by changes in intestinal motility or loss of effect of noradrenaline due to changes in portal venous hydrogen ion concentration.

4. During a noradrenaline infusion there was a reduction in oxygen consumption associated with a fall in blood flow. During the period of ‘autoregulatory escape’, however, oxygen consumption increased. The significance of these observations is discussed.
Respiratory function during thermal tachypnoea in sheep
Authors: Hales J. R. S. , Webster M. E. D.
Published: December 2014

1. Four Merino wethers were exposed to dry bulb temperatures ranging from approximately 20 to 60° C, and the concurrent changes in respiratory frequency, tidal volume, respiratory minute volume, alveolar ventilation, dead space ventilation, carbon dioxide output, rectal temperature, and arterial and mixed venous blood, CO2 content, CO2 partial pressure and pH were established.

2. The respiratory response to heat exposure showed two phases. Respiratory minute volume was initially increased by a rise in the respiratory frequency, while tidal volume decreased. After more prolonged exposure there was a second phase in which respiratory minute volume was further increased by an increase in the tidal volume; respiratory frequency was now slower than in the first phase but was still well above control values.

3. The increase in respiratory minute volume during the first phase of the response was restricted almost entirely to the respiratory dead space; changes in blood CO2 and pH were slight. In the second phase, respiratory minute volume showed a much greater increase, and a change of alveolar ventilation to about 5 times the control level resulted in severe respiratory alkalosis.

4. Contrary to findings in cattle, the slower, deeper form of respiration could be elicited even with rectal temperature in the normal range. This change in respiration appears to be the result of either peripheral thermoreceptor function or mechanical demands of the respiratory system. The neglect of control of acid—base balance during the second phase indicates the existence of a dominant thermal stimulus or modification of respiratory control mechanisms.
Gastric secretion during pregnancy and lactation in the rat
Authors: Lilja B. , Svensson S. E.
Published: December 2014

1. Gastric acid secretion has been studied in the rat before, during and after pregnancy using different types of stomach preparation. During the same periods the histamine‐forming capacity (HFC) has been determined in gastric mucosa and mammary gland.

2. In rats with a whole stomach fistula interdigestive acid secretion is increased during pregnancy and lactation.

3. In rats with a denervated chronic pouch secretory response to stimulation with gastrin and histamine is augmented during pregnancy and lactation.

4. The histamine forming capacity (HFC) of the gastric mucosa is increased 2‐3 times during the last days of pregnancy and also during lactation.

5. The HFC of the mammary gland is increased 2‐3 times during lactation as compared with the fully developed gland in pregnancy.
The use of a non‐ionic detergent (Triton WR 1339) to determine rates of triglyceride entry into the circulation of the rat under different physiological conditions
Authors: Otway Sheila , Robinson D. S.
Published: December 2014

1. The concentration of triglyceride in the plasma rises linearly for 3 hr after the intravenous injection of the non‐ionic detergent, Triton WR 1339, in the rat.

2. Minimum rates of triglyceride entry into the plasma have been calculated from measurements of the plasma triglyceride concentration at 1·5 hr after Triton injection. These are 30 and 52 μmoles/hr.200 g body weight respectively for male and female animals on a stock laboratory diet and 25 and 33 μmoles/hr.200 g body weight respectively for male and female animals starved for 48 hr. The values may have to be increased by 10 or 20% to take account of a small leak of triglyceride from the plasma in animals injected with Triton and of an effect of ether anaesthesia on the rate of entry of triglyceride into the plasma.

3. Substitution of the stock laboratory diet by diets that are lower in fat content does not alter significantly the rate of triglyceride accumulation in the plasma after Triton injection.

4. There is no change in the triglyceride content of the livers of male and female rats at 24 hr after Triton injection. At 6 hr after Triton, the liver triglyceride content of female rats which have been fed their normal diet is increased.
Water uptake by Bufo melanostictus, as affected by osmotic gradients, vasopressin and temperature
Authors: Dicker S. E. , Elliott Annie B.
Published: December 2014

1. The rate of water uptake across the skin was studied in the live toad, Bufo melanostictus. When toads were kept in distilled water at 29° C the uptake of water amounted to 16·9 ± 1·3 μl./cm2/hr; when bathed in sucrose or urea solutions, the water uptake diminished with increasing osmotic pressure. There was no water uptake observed when toads were kept in 200 m‐osmolar sucrose or urea.

2. Intramuscular injections of vasopressin increased the rate of water uptake from distilled water. There was a good relation between doses and responses over various time intervals. A dose of 4 m‐u. vasopressin/g body wt. doubled the rate of water uptake over a period of 1 hr. The same dose of vasopressin doubled the rate of water uptake when the toads were kept in solutions of sucrose or urea of different osmolarity.

3. The rate of water uptake when the toads were bathed in sodium chloride solutions was consistently 8 μl./cm2/hr greater than when bathed in sucrose or urea solutions of equal osmolarity. There was no water uptake when the sodium chloride solution was 285 m‐osmolar.

4. Vasopressin (4 m‐u./g) injected intramuscularly doubled the rate of water uptake from sodium chloride solutions of different osmolarity.

5. With solutions of potassium chloride, sodium nitrate, and potassium nitrate, in concentrations up to 150 m‐osmoles/l., the rate of water uptake was found to be the same as with solutions of sodium chloride of the same osmolarity. Similarly, it was doubled by injection of vasopressin (4m‐u./g).

6. The effect of temperature on the rate of water uptake before and after injection of vasopressin was investigated in toads kept in distilled water, sucrose, or sodium chloride solutions. For temperatures between 20 and 37° C, vasopressin (4 m‐u./g) reduced the activation energy involved in the process of water uptake by 4000 cal.

7. The results agree with the view that water uptake follows a diffusion process which is facilitated by vasopressin, possibly as a result of increasing the size or number of available pores.
The margin of safety of neuromuscular transmission
Authors: Paton W. D. M. , Waud D. R.
Published: December 2014

1. The margin of safety for neuromuscular transmission in the tibialis and sartorius muscles of the cat has been determined by measuring the ratio by which end‐plate depolarization produced by succinylcholine, decamethonium, octamethonium or iodocholine is antagonized, in the presence of neuromuscular block produced by tubocurarine, gallamine or DF‐596. The estimate of the margin of safety was independent of the particular drugs chosen for the measurement.

2. To produce threshold block to indirect stimulation once every 10 sec, a fractional occupancy by the antagonist of 0·76 ± 0·05 (
S.D.) was required; for nearly complete block, an occupancy of 0·917 ± 0·16 (
S.D.) was required. These figures correspond to factors of safety of 4·1 and 12 for the most sensitive and the most resistant groups of fibres respectively.

3. The interaction between the agonists and the antagonists, when tested over a wide range of dosage, did not conform with the conditions of full competitive equilibrium. It was concluded that this arose, not because of some interfering non‐competitive process, but because, during the relatively brief exposure to agonist, the equilibrium between the antagonist and the receptors is not significantly disturbed. An analysis of this condition of quasi‐equilibrium is given. A correction downwards of the direct estimates of the margin of safety is required, but this proves to be small, about 8%, and may not be significant.

4. The safety factor diminished when the motor nerve had been cut more than 5 hr; it is suggested that this represents an early sign of nerve degeneration.

5. With dog sartorius muscle, results similar to those in the cat were obtained. But for deep block in the rabbit, the safety factor was only about 4.

6. The existence of a substantial margin of safety influences considerably the interpretation of the time course of action of blocking drugs, and of comparisons between responses to nervous excitation and drug injection.
The effect of water diuresis on electrolyte excretion in unanaesthetized dogs
Authors: Coxon R. V. , Ramsay D. J.
Published: December 2014

1. The relation between water loading and electrolyte excretion in dogs fed on a meat diet proved impossible to evaluate owing to the large variability in electrolyte excretion rates in control experiments.

2. In animals fed a synthetic diet of constant and known composition the administration of a water load of 2·5% of body weight caused significant increases in the rate of excretion of sodium (P < 0·01) and potassium (P < 0·05). The chloride excretion rate also increased in the one animal tested.

3. The significance of these results is discussed.
The effect of thyrocalcitonin on blood—bone calcium equilibrium in the perfused tibia of the cat
Authors: Macintyre I. , Parsons J. A. , Robinson C. J.
Published: December 2014

1. In the isolated tibia of the cat, perfused with blood from its own carotid connected to popliteal artery via a pump, infusion of porcine thyrocalcitonin causes an arteriovenous difference in calcium concentration of up to 5%, corresponding to net retention of calcium in bone.

2. When taken in conjunction with determinations of radiocalcium clearance in the tibia, the effect is of the right order of magnitude to account for the hypocalcaemic action of thyrocalcitonin in the whole animal.

3. Calcium retention was accompanied by a small increase in acidity of outflowing venous blood whereas verification of the hypothesis of calcium regulation by pH change in the bone substance would require a decrease.
Cortical responses to paired stimuli applied peripherally and at sites along the somato‐sensory pathway
Authors: Angel A.
Published: December 2014

1. Experiments have been performed on animals anaesthetized with various anaesthetics to determine the responsiveness of the cortex to the second of a pair of identical stimuli applied at three sites along the sensory pathway, i.e. to the periphery, the medial lemniscus and to thalamocortical fibres.

2. It has been found that in deeply anaesthetized animals the mass response recorded from the cerebral cortex to the second of a pair of peripheral or lemniscal stimuli became reduced in size if the interval between the stimuli was 30‐500 msec. If the interval was less than 30 msec for peripheral stimuli or between 10 and 30 msec for lemniscal stimuli responses were not obtained to the second stimulus. This was found to be a basic pattern which could be modified in animals less deeply anaesthetized. In these animals, periods of relatively increased responsiveness were seen after peripheral stimulation.

3. The post‐synaptic responses recorded from the ventrobasal thalamus showed the same behaviour to the second of a pair of peripheral stimuli as did the cortex both as regards size and latency of the responses.

4. The post‐synaptic responses recorded from the cuneate nucleus rarely showed any reduction in size unless the separation between the stimuli was 10 msec or less; even at intervals as low as 3 msec there was no increase in the latency of the response.

5. When a pair of stimuli were applied to thalamocortical fibres, a different pattern of cortical responsiveness was found. At the time the cortical response to stimulation at pre‐thalamic sites was reduced or abolished, the response to stimulation at post‐thalamic sites was unaltered or increased in size.

6. Finally an attempt was made to correlate the mass response recorded from the cortical surface and the activity of single cortical cells. Two types of cell could be distinguished in the rat. Those lying from 0·35 to 1·2 mm deep in the cortex showed a response pattern, to paired stimuli, closely resembling that of the cortical mass response. Others situated deeper in the cortex were found which had a very long absolute unresponsive time, from 50 to 80 msec and a very long relative unresponsive time of 1 sec.
The effects of stimulation of the hepatic nerves, infusions of noradrenaline and occlusion of the carotid arteries on liver blood flow in the anaesthetized cat
Authors: Greenway C. V. , Lawson Anne E. , Mellander S.
Published: December 2014

1. In anaesthetized cats, the hepatic artery, portal vein and inferior vena cava pressures and the hepatic artery and portal vein flows were recorded using pressure transducers and electro‐magnetic flowmeters.

2. The hepatic nerves were stimulated with maximal stimuli for periods of 2‐5 min. The magnitude of the response varied with the frequency of stimulation over the range 1‐10 impulses/sec. The resistance to flow increased in both the hepatic artery and the portal vein.

3. In the hepatic artery, mean pressure remained virtually constant, while the flow showed an initial marked decrease followed by a return towards the control level. In the portal vein, the flow remained constant while portal pressure showed a maintained increase. These responses were unaffected by previous administration of atropine and propranolol, but were blocked by phenoxybenzamine.

4. Infusions of noradrenaline into the hepatic artery produced changes similar to those following stimulation of the nerves. In contrast, when the hepatic arterial pressure was maintained constant, intravenous infusions of noradrenaline produced a maintained decrease in hepatic artery flow.

5. The occurrence of autoregulation of the hepatic artery flow at arterial pressures above 80‐100 mm Hg was confirmed.

6. Occlusion of the carotid arteries caused a rise in arterial pressure with little change in hepatic artery flow, but when the hepatic artery pressure was maintained at the pre‐occlusion level the flow showed an abrupt decrease, usually followed by a recovery towards the control level. This decrease was abolished by section of the hepatic nerves and removal of the adrenal glands.

7. It is concluded that the increase in hepatic artery resistance during occlusion of the carotid arteries was dependent on the hepatic nerves, the adrenal medullary secretions and an intrinsic autoregulatory mechanism.
Pulmonary vasoconstriction and changes in heart rate during asphyxia in immature foetal lambs
Authors: Campbell A. G. M. , Dawes G. S. , Fishman A. P. , Hyman A. I.
Published: December 2014

1. The effect of changing the composition of pulmonary arterial blood on the pulmonary vasoconstrictor response to asphyxia was studied in immature foetal lambs of ∼ 90 days gestation age.

2. When normal foetal carotid arterial blood (withdrawn before asphyxia) was introduced during asphyxia, the pulmonary vasoconstriction was rapidly and wholly relieved as soon as this blood reached the lung. This did not happen when blood was used which had been withdrawn during asphyxia.

3. Conversely introduction into a pulmonary artery of a foetal lamb during recovery, of arterial blood withdrawn during asphyxia, caused an immediate return of pulmonary vasoconstriction.

4. These phenomena could not be explained by the generation of vasodilator agents such as bradykinin, acetylcholine, histamine or isoprenaline.

5. During asphyxia injection of normal foetal arterial blood into the left atrium did not cause pulmonary vasodilatation, but did elicit a large increase in heart rate.

6. Neither the pulmonary vasoconstriction during asphyxia, nor its relief by normal foetal arterial blood, nor the changes in heart rate were affected by previous bilateral vagotomy or administration of atropine or hexamethonium.

7. It was concluded that, in immature foetal lambs, the effect of asphyxia in causing pulmonary vasoconstriction was mainly, if not exclusively, by a local action within the lungs, and that the bradycardia during asphyxia was mainly due to the fall in PO2 acting locally upon the heart.
The incorporation of inorganic phosphate into adenosine triphosphate by reversal of the sodium pump
Authors: Garrahan P. J. , Glynn I. M.
Published: December 2014

1. Resealed ghosts were prepared containing much potassium, very little sodium, and adenosine triphosphate (ATP), adenosine diphosphate (ADP) and 32P‐labelled orthophosphate (Pi) at concentrations such that the ratio [ATP]/([ADP].[Pi]) was low. Iodoacetate, iodoacetamide or both were also present. The ghosts were incubated in high‐sodium, potassium‐free media with and without ouabain, or in high‐potassium media, and the incorporation of 32P into ATP and ADP in 15 min was measured.

2. There was some incorporation of 32P into the nucleotides whatever the medium, possibly because of the residual activity of glycolytic enzymes, but in every experiment there was extra incorporation when the ghosts were in a high‐sodium, potassium‐free medium. This extra incorporation was largely abolished by ouabain (5 experiments) and partly abolished by oligomycin (1 experiment).

3. It seems that if conditions are such that the over‐all reaction associated with transport ATPase activity leads to an increase in free energy, the transport system will run backwards at a measurable rate and ATP will be synthesized at the expense of energy derived from ionic concentration gradients.

4. The nature of the transport system is discussed in the light of the findings of this paper and the four preceding papers.
The effect of chromatic aberration on visual acuity
Authors: Campbell F. W. , Gubisch R. W.
Published: December 2014

1. Differences of threshold contrast are predicted from optical theory for a grating acuity target in monochromatic and white light. The greatest differences, up to 65%, are predicted for gratings of lower contrast and pitch than those normally used in measurements of visual acuity.

2. Using three subjects, we measured contrast thresholds with 1·5 and 2·5 mm diameter artificial pupils for natural and paralysed accommodation, using a tungsten lamp and wave‐lengths of 546 and 578 mm.

3. Excellent agreement is obtained between predicted and measured differences.

4. Results confirm that observed acuity and sensitivity differences between white and monochromatic lights are largely optical in origin, but involve at least two independent colour mechanisms as spectral weighting functions. Stiles's π4 and π5 sensitivities afford a much better fit to observed differences than the C.I.E. visibility curve.
Spontaneous synaptic potentials and quantal release of transmitter in the stellate ganglion of the squid
Authors: Miledi R.
Published: December 2014

1. Several kinds of synapses have been studied in the stellate ganglion of the squid.

2. A small electric coupling was found between giant fibres in different stellar nerves.

3. Post‐synaptic potentials recorded from the cells of small axons are composite, indicating that there are converging inputs from several pre‐ganglionic fibres.

4. Spontaneous miniature synaptic potentials were recorded from all types of synapses. Miniature potentials in the cells of small axons had a slower time course than those in the giant fibre system.

5. Tetrodotoxin abolished nerve impulses in the ganglion but did not prevent the spontaneous quantal release of transmitter from the terminals, or its action on the post‐synaptic membrane; nor did it prevent the increase in rate of release produced by depolarization of the presynaptic fibre.

6. Glutamate depolarized the giant fibre when applied iontophoretically to the synaptic region. Similar doses applied intracellularly were without effect.
The generation and spread of S‐potentials in fish (Cyprinidae)
Authors: Naka K. I. , Rushton W. A. H.
Published: December 2014

1. S‐potentials from Luminosity‐units in the excised eye of the tench (Tinca) were excited by white lights of various intensities and spatial distributions.

2. When a small light spot of fixed size and intensity was presented at various distances from the recording electrode, the S‐potential was found to suffer an exponential attenuation with distance (Fig. 3).

3. A circular patch of light centred upon the electrode and varied in radius gave concordant results.

4. The effects at the electrode site of a distant light flash was not due to light scattered to the electrode which acted upon the retina there; the light acted locally and it was the current that spread.

5. With red and blue light stimuli superposed on the retina, it is the potentials not the lights that add.

6. These experimental results seem to indicate that S‐potentials can spread laterally across the retina within a thin layer at about the horizontal cell level.

7. The layer is bounded by leaky membranes which appear to be electrogenic, no doubt as a result of transmitters released by light which change the permeability. Electric currents have no demonstrable effect.

8. Two simple results were found. (a) The membrane contains an element whose conductance is proportional to the light intensity. (b) The S‐potential is a hyperbolic function of light intensity.

9. All these experimental results can be explained quantitatively in terms of the formal model of Fig. 8F. But the required change of membrane permeability with light has not yet been demonstrated.
The content and localization of catecholamines in the carotid labyrinths and aortic arches of Rana temporaria
Authors: Banister R. J. , Portig P. J. , Vogt M.
Published: December 2014

1. The catecholamine content of the carotid labyrinth of Rana temporaria was estimated by two different methods, and compared with that of the aortic arch. In both tissues adrenaline was found as the dominant amine, with traces of dopamine and noradrenaline detectable in the labyrinth only.

2. Per gram of fresh tissue, the labyrinth usually contained more adrenaline than the aortic arch.

3. On microscopic examination, the aortic arch was found to contain nerve fibres which fluoresced after treatment with formaldehyde, whereas within the carotid labyrinth the formaldehyde‐induced fluorescence was localized in the cytoplasm of clusters of small cells. This fluorescence resembled that exhibited by glomus cells in the mammalian carotid body.
The motor innervation of the rat urinary bladder
Authors: Carpenter F. G. , Rubin R. M.
Published: December 2014

1. The post‐ganglionic nerves visible in silver‐impregnated sections of a normal rat bladder were absent 14 days after both pelvic ganglia had been ablated. After ablation of one ganglion the distribution of nerve trunks in either side of the organ was unchanged. Post‐ganglionic axons from either side appear to distribute bilaterally.

2. The acetylcholine (ACh) content of the rat bladder was reduced from control by 50% after the post‐ganglionic nerves from one ganglion had degenerated. However, the ACh content in the two halves of the bladder sectioned along the mid line was the same after one nerve had degenerated.

3. Motor responses of bladder preparations elicited during stimulation of both pelvic nerves were compared with responses elicited when each nerve was stimulated separately. In three‐quarters of the animals the sum of the individual responses exceeded the response to combined nerve stimulation by no more than 20%. The functional overlap between the two groups of motor nerves to the bladder was therefore no greater than this amount in most animals.

4. Motor responses of normally innervated bladder preparations elicited in vitro by transmural stimulation were compared with responses elicited after the post‐ganglionic innervation from one side had degenerated. The mean response of bladders with half their innervation was 50‐65% of the mean response of bladders normally innervated. The functional overlap by the two groups of nerves was found to be no greater than 15%.
Relation between sodium concentration, electrical potential and transfer capacity of rat small intestine
Authors: Barry R. J. C. , Eggenton Jacqueline , Smyth D. H. , Wright E. M.
Published: December 2014

1. A study has been made of the effect of Na replacement in the incubation media on the hexose‐dependent potential and the capacity of sacs of rat intestine to transfer fluid and galactose.

2. Replacement of NaCl with mannitol or Tris Cl had little effect on the hexose‐dependent potential, while replacement with LiCl and KCl had an inhibitory effect on the potential.

3. Replacement with KCl, LiCl, mannitol and Tris Cl all reduced the capacity to transfer fluid and galactose, but the effects of Li and K replacement were greater than mannitol or Tris replacement.

4. There is not a fixed relation between the magnitude of the potential and the amount of galactose transferred.
Neurohypophysial peptide interaction with magnesium in avian vascular smooth muscle*
Authors: Somlyo Andrew P. , Somlyo Avril V. , Woo Chi-Yuan
Published: December 2014

1. The contractile responses of helically cut vascular strips of chickens to vasoactive agents were studied.

2. Large pulmonary arteries were contracted by neurohypophysial peptides, but not by angiotensin, acetylcholine, histamine, 5‐hydroxytryptamine, bradykinin or eledoisin. The activity of oxytocin was greater than that of arginine vasopressin.

3. Vasodilator effects of oxytocin upon small (200‐500 μ diameter) mesenteric and muscular arteries were demonstrable, but inconsistent.

4. Magnesium potentiated in a parallel fashion the vasoconstrictor effects of oxytocin and of arginine vasopressin.

5. Deamino‐oxytocin was potentiated by magnesium. This finding suggests a difference between the peptide‐protein interactions of tissue receptors and those of neurophysin.
Factors influencing contraction and catch in Mytilus smooth muscle
Authors: Twarog Betty M.
Published: December 2014

1. Conditions are defined which determine the level of catch after acetylcholine stimulation of Mytilus muscle.

2. Catch tension in dissected muscle is absent when connexions with ganglia are intact.

3. Catch tension is absent at temperatures above 30° C.

4. Catch tension decreases when intervals between stimuli are increased.

5. Increasing concentrations of 5‐hydroxytryptamine (5‐HT) from 10−8
M to 10−6
M quantitatively decreases catch tension.

6. The length—tension curve of ganglion‐free Mytilus muscle bundles suggests that catch tension varies in proportion to the tension developed in contraction.

7. External Ca2+ concentration has no selective influence on catch.

8. All factors which reduce catch also increase muscle excitability, suggesting that catch may depend on a mechanism controlling the intracellular concentration of an activator such as Ca2+.
Analysis of the activity of one type of spontaneously discharging unit in the cortex cerebri of the anaesthetized rat
Authors: Holmes O. , Houchin Jane
Published: December 2014

1. Extracellular records from one type of spontaneously active element in the cortex of rats anaesthetized with urethane have been analysed statistically.

2. Intensity functions reveal that the frequency of discharge of a unit tends to be modulated periodically, the period being 1½‐2 sec under fairly deep anaesthesia. When anaesthesia becomes lighter, long intervals occur rarely; the unitary discharge becomes less regular and the intensity function becomes flat. Variations in depth of anaesthesia are accompanied by changes in amplitude of the periodic modulation; the period of the modulation is not significantly altered.

3. Summed interval histograms indicate that the long intervals are separated by groups of short intervals in a significantly regular fashion. The number of short intervals in a group varies from one to about fifteen, according to the mean frequency of discharge of the unit.

4. Serial correlation coefficients reflect the observations of 2 and 3 above but indicate no additional serial correlation. The existence of long intervals obscures any serial patterning of short intervals during bursts.

5. Simultaneous records from two units show that the periods of activity in the two units are highly synchronized.

6. It is probable that all these features are due to a process which causes periodic synchronous excitability changes of all the spontaneously active elements of the type studied.
The districution of biogenic amines in the carotid bifurcation region
Authors: Rees P. M.
Published: December 2014

1. The distribution of phenolic amines in the carotid body and of adrenergic nerves in the arterial walls of the carotid bifurcation region was investigated histochemically using the phenolic amine‐formaldehyde gas condensation reaction, with supplementary electron microscopical examination. Studies were conducted on normal rabbits and on rabbits after superior cervical ganglionectomy.

2. The glomus cells of the carotid body contain phenolic amines. The cellular amine persists after long‐term sympathetic ganglionectomy.

3. The blood vessels supplying the carotid body receive an adrenergic innervation which disappears following superior cervical ganglionectomy.

4. The walls of the carotid sinus contain adrenergic nerve fibres derived from the superior cervical ganglion.

5. There is no penetration of the arterial tunica media by vasomotor fibres in any part of the carotid bifurcation region.

6. Ultimate terminations of adrenergic nerves upon smooth muscle occur across the medio‐adventitial border of the common, internal and external carotid arterial walls but only in relation to smooth‐muscle cells in the adventitia of the carotid sinus wall.
Fast and slow muscles of the chick after nerve cross‐union
Authors: Hník P. , Jirmanová Isa , Vyklický L. , Zelená Jiřina
Published: December 2014

1. The multiply innervated anterior latissimus dorsi (ALD) and the focally innervated posterior latissimus dorsi (PLD) muscles of the chick were investigated 2‐18 months after nerve cross‐union.

2. The fast PLD muscle re‐innervated by the slow muscle nerve became supplied with ‘en grappe’ end‐plates and responded to a single nerve volley with local potentials only. Control PLD muscles re‐innervated by the original nerve, had ‘en plaque’ end‐plates and responded to a single nerve volley by synchronous action potentials in the same way as normal muscles.

3. In the slow ALD muscle re‐innervated with the ‘mixed’ PLD nerve, the type of innervation and of electromyographic response remained practically unchanged, with the exception of transplanted ALD muscles supplied with PLD nerves where, in addition to local responses, propagated action potentials were registered electromyographically in response to single nerve volleys.

4. ALD muscles of young chickens re‐innervated both with an implanted purely fast muscle nerve and with the regenerated original nerve, had two types of innervation: ‘en plaque’ end‐plates around the nerve implant, and multiple ‘en grappe’ end‐plates in areas supplied with the ALD nerve. Accordingly, propagated action potentials were registered in response to single nerve volleys in regions near the implant, whereas local potentials were recorded in areas with original innervation.

5. Contraction velocity was not substantially altered in PLD and ALD muscles after nerve cross‐union.

6. No changes were observed in the fine structure of muscle fibres in extrajunctional regions.
The neural mechanism of binocular depth discrimination
Authors: Barlow H. B. , Blakemore C. , Pettigrew J. D.
Published: December 2014

1. Binocularly driven units were investigated in the cat's primary visual cortex.

2. It was found that a stimulus located correctly in the visual fields of both eyes was more effective in driving the units than a monocular stimulus, and much more effective than a binocular stimulus which was correctly positioned in only one eye: the response to the correctly located image in one eye is vetoed if the image is incorrectly located in the other eye.

3. The vertical and horizontal disparities of the paired retinal images that yielded the maximum response were measured in 87 units from seven cats: the range of horizontal disparities was 6·6°, of vertical disparities 2·2°.

4. With fixed convergence, different units will be optimally excited by objects lying at different distances. This may be the basic mechanism underlying depth discrimination in the cat.
The breakdown of adenosine triphosphate in the contraction cycle of the frog sartorius muscle
Authors: Mommaerts W. F. H. M. , Wallner A.
Published: December 2014

1. It is confirmed that a fluorodinitrobenzene (FDNB)‐treated frog sartorius muscle does not split phosphorylcreatine in the course of its contraction cycle, but does use adenosine triphosphate (ATP).

2. Good stoicheiometric relations between the diminution of ATP and the formation of adenosine diphosphate (ADP), adenosine monophosphate (AMP) and phosphate are obtained, and in a 0·2 sec tetanus at 0° C the net break‐down of ATP amounts to 0·27, the total equivalent break‐down to 0·34 μmoles/g.

3. There is no difference in this quantity between muscles interrupted at the height of contraction and those that have also relaxed, and, in experiments specifically designed to determine relaxation metabolism separately, no such metabolism is found. Thus, all the ATP‐break‐down occurs in the contraction phase.
Central temperature regulation in the conscious rabbit after monoamine oxidase inhibition
Authors: Cranston W. I. , Rosendorff C.
Published: December 2014

1. Measured thermal loads were applied to conscious rabbits by intravenous infusions of hot or cold saline. The responses of the central temperature regulating mechanism were assessed by measuring hypothalamic temperature change. The relationship between thermal load and temperature response was established in normal animals.

2. Intramuscular injection of tranylcypromine (20 mg/kg. day for 6‐8 days) had no effect upon resting temperature or the temperature response to thermal loads, though the diencephalic concentrations of noradrenaline and 5‐hydroxytryptamine (5‐HT) were increased.

3. Either hypothalamic monoamines are not concerned in the regulation of normal temperature or there is a monoamine ‘pool’ in the hypothalamus which is concerned with temperature regulation but which is unaffected by monoamine oxidase inhibition.
Thermal stimulation of hypothalamic neurones in unanaesthetized rabbits
Authors: Hellon R. F.
Published: December 2014

1. A technique has been devised for recording unit activity in the anterior hypothalamus of conscious rabbits during the controlled displacement of local temperature by 1‐2° C. The region at 1 and 2 mm from the mid line was explored.

2. All the units studied showed spontaneous activity before thermal stimulation with a mean rate of 9 impulses/sec (range 1/16 sec to 65/sec).

3. Twenty‐seven (10%) of the recorded neurones showed a change in firing rate which could be related to the temperature changes. Twenty‐one of the cells were ‘warm‐sensitive’ and were excited when temperature was raised or inhibited when it was lowered. The other six units were ‘cold‐sensitive’ and showed the opposite type of response.

4. Apart from this directional grouping, it was possible to classify the responses into four categories: A, five cells whose firing rate was always proportional to local temperature over a range from 2° C below to 2° C above body temperature; B, six cells whose average level of firing changed during the period of observation, but whose sensitivity to temperature was not affected; C, eight cells which showed a threshold and were only affected by temperature above or below a certain level; D, four cells whose changes in frequency either led or lagged behind the temperature changes.

5. The positions of these sensitive units in the hypothalamus did not show any apparent pattern, except that 75% of them were found 1 mm lateral to the mid line; the remaining 25% were 2 mm lateral.
Histamine in the plasma and gastric juice of cats during infusions of [14C]histamine
Authors: Born G. V. R. , Sewing K.-Fr.
Published: December 2014

1. In anaesthetized cats with gastric fistulae, the relation was investigated between the rate of gastric secretion and the histamine contents of the plasma and the gastric juice during intravenous infusions of [14C]histamine for 3 hr.

2. In the first hour only, some endogenous histamine appeared in the gastric juice.

3. There was no quantitative relation between the histamine that was infused and that which appeared in the gastric juice.

4. There was no correlation between the rate of gastric secretion and the concentration of histamine in either plasma or gastric juice.

5. It was concluded that the secretion of histamine into the gastric juice was not essential to gastric secretion.
The uptake of amines by human erythrocytes in vitro
Authors: Born G. V. R. , Day Margaret , Stockbridge Anne
Published: December 2014

1. Human erythrocytes incubated at 37° C in Krebs bicarbonate solution at pH 7·5 took up 5‐hydroxytryptamine, histamine and (‐)‐noradrenaline at slow rates which were proportional to the concentration of the amines in the medium at least up to 16 μg/ml., in accordance with a simple diffusion process.

2. The initial velocity of uptake was greatest for 5‐hydroxytryptamine, about 4 times less for histamine and about 20 times less for (‐)‐noradrenaline; (+)‐noradrenaline was not taken up.

3. Comparison of uptake measurements by bio‐assay and by radioactivity indicated that, after 1 hr, about 10% of each amine taken up had been inactivated.

4. At 2° C the uptake of all three amines was greatly diminished. The presence of the antagonists cocaine, chlorpromazine, lysergic acid diethylamide, mepyramine and pronethalol (at 10−6 or 10−5 g/ml.) did not affect uptake of the amines.

5. In the steady state the ratios of concentration of the amines between cells and medium were greater than could be accounted for by a Donnan distribution.

6. Cells which had taken up amines lost most but not all of them into amine‐free medium, at rates which were slower than the corresponding rates of uptake. It was concluded that the amines are partially bound in the cells, noradrenaline most and histamine least.

7. The slow diffusion of amines into, and the small amounts retained by, erythrocytes indicate that they do not contribute significantly to the rapid termination of the pharmacological actions of these amines in vivo.
The effects of changes in haematocrit on renal function
Authors: Nashat F. S. , Portal R. W.
Published: December 2014

1. Acute changes in total body haematocrit were produced in anaesthetized dogs by the rapid infusion of packed red cells, dextran solution or hypertonic mannitol. A reduction of haematocrit resulted in a decrease in filtration fraction, and a rise of haematocrit in an increase in filtration fraction. A direct relationship between water reabsorption (relative to filtered load) and packed cell volume (
P.C.V.) was also observed.

2. It is suggested that the changes in filtration fraction accompanying changes in haematocrit are mediated largely by a passive alteration of efferent arteriolar resistance resulting from modifications of blood viscosity.
Electrical potentials and ion concentrations across the gut of Cryptochiton stelleri
Authors: Lawrence A. L. , Mailman D. S.
Published: December 2014

1. The electrical potential and concentration differences of Na, K, and Cl in the mucosal and serosal solutions of everted sacs of gut from Cryptochiton stelleri were determined.

2. The parameters were used to determine if active ion transport was present in segments from the anterior and posterior intestine.

3. The electrical potentials were of the order of 0·5 mV, serosa negative, in the anterior intestine, and 1 mV, serosa positive, in the posterior intestine. The potentials, although small, were significantly different from zero.

4. The potentials of all segments responded to anoxia and incubation at different temperatures in a manner indicating that they were of active origin.

5. Ions were accumulated against electrical potentials in some segments but did not respond to anoxia or incubation at different temperatures in a consistent fashion.

6. It was concluded that active ion transport was present but no evidence for active transport of Na, K or Cl across the gut could be found.

7. K leaked from the gut during incubation at non‐physiological temperatures or during hypoxia and was removed upon restoration of physiological conditions.
Auditory responses of neurones in the lateral mesencephalic nucleus (inferior colliculus) of the Barbary dove
Authors: Biederman-Thorson Marguerite
Published: December 2014

1. Auditory responses have been recorded from forty‐five single neurones in the lateral mesencephalic nucleus of the dove, confirming the suspected auditory function of this nucleus.

2. Most of the neurones with sustained responses to tones fell into three response‐categories: inhibitory only, excitatory in a central range of frequencies with inhibition in adjacent frequency regions, and predominantly inhibitory with one or more relatively small excitatory regions. Seven of the neurones studied showed only transient responses: these had high thresholds or were restricted to a narrow range of frequencies.

3. Responses to clicks were sometimes obtained, but were variable in different units and in a single unit were often dependent on repetition rate.

4. Many properties of these neurones are similar to those in the cat inferior colliculus. The most notable difference is the existence in the dove of neurones with exclusively or predominantly inhibitory responses.
CATCh, an Ensemble Classifier for Chimera Detection in 16S rRNA Sequencing Studies
Authors: Mysara Mohamed , Saeys Yvan , Leys Natalie , Raes Jeroen , Monsieurs Pieter
Published: December 2014

In ecological studies, microbial diversity is nowadays mostly assessed via the detection of phylogenetic marker genes, such as 16S rRNA. However, PCR amplification of these marker genes produces a significant amount of artificial sequences, often referred to as chimeras. Different algorithms have been developed to remove these chimeras, but efforts to combine different methodologies are limited. Therefore, two machine learning classifiers (reference-based and
de novo
CATCh) were developed by integrating the output of existing chimera detection tools into a new, more powerful method. When comparing our classifiers with existing tools in either the reference-based or
de novo
mode, a higher performance of our ensemble method was observed on a wide range of sequencing data, including simulated, 454 pyrosequencing, and Illumina MiSeq data sets. Since our algorithm combines the advantages of different individual chimera detection tools, our approach produces more robust results when challenged with chimeric sequences having a low parent divergence, short length of the chimeric range, and various numbers of parents. Additionally, it could be shown that integrating CATCh in the preprocessing pipeline has a beneficial effect on the quality of the clustering in operational taxonomic units.
Multilocus Sequence Analysis of Xanthomonads Causing Bacterial Spot of Tomato and Pepper Plants Reveals Strains Generated by Recombination among Species and Recent Global Spread of Xanthomonas gardneri
Authors: Timilsina Sujan , Jibrin Mustafa O. , Potnis Neha , Minsavage Gerald V. , Kebede Misrak , Schwartz Allison , Bart Rebecca , Staskawicz Brian , Boyer Claudine , Vallad Gary E. , Pruvost Olivier , Jones Jeffrey B. , Goss Erica M.
Published: December 2014

Four
Xanthomonas
species are known to cause bacterial spot of tomato and pepper, but the global distribution and genetic diversity of these species are not well understood. A collection of bacterial spot-causing strains from the Americas, Africa, Southeast Asia, and New Zealand were characterized for genetic diversity and phylogenetic relationships using multilocus sequence analysis of six housekeeping genes. By examining strains from different continents, we found unexpected phylogeographic patterns, including the global distribution of a single multilocus haplotype of
X. gardneri
, possible regional differentiation in
X. vesicatoria
, and high species diversity on tomato in Africa. In addition, we found evidence of multiple recombination events between
X. euvesicatoria
and
X. perforans.
Our results indicate that there have been shifts in the species composition of bacterial spot pathogen populations due to the global spread of dominant genotypes and that recombination between species has generated genetic diversity in these populations.