bluuebunny/crossref_metadata_2025_split huggingface dataset:
The maturation of neuromuscular function in a multiply innervated structure: development of the longitudinal smooth muscle of the foetal mammalian gut and its cholinergic excitatory, adrenergic inhibitory, and non‐adrenergic inhibitory innervation
Authors: Gershon Michael D. , Thompson Elizabeth Barnes 
Published: December 2014

1. The earliest components of the developing innervation of the rabbit intestine to be detected in this study were the cholinergic excitatory and the intrinsic inhibitory innervation. These developed simultaneously in the rabbit at 17 days of gestation. Both were also present in the mouse by the 16th day of gestation. Responsiveness of rabbit tissue to exogenous acetylcholine appeared together with the advent of a functional cholinergic innervation. Since excitatory responses were potentiated by eserine, the tissue was probably able to inactivate acetylcholine through hydrolysis mediated by cholinesterase. Early relaxant responses resisted blockade by adrenergic neurone blocking agents and by antagonists active at α‐ and β‐adrenoceptors.2. The development of the adrenergic innervation lagged far behind that of the other two components. Specific uptake of noradrenaline in the rabbit was detected for the first time at the 21st day of gestation and stores of noradrenaline could not be detected histochemically until 26‐28 days. However, relaxant responses to stimulation of the perivascular sympathetic supply, such as characterize adult tissues, had not yet developed by the time of birth. Relaxation in response to perivascular stimulation could be seen 30 days after birth.3. Morphologic studies indicated that the longitudinal layer of smooth muscle was very primitive when an effective innervation was established. Although contractile, the cells were still myoblasts. Neural elements also appeared primitive. Thus considerable morphological maturation follows the development both of a functioning contractile machinery and innervation in the foetal gut.4. This study helps establish that the intrinsic inhibitory innervation of the gut is not adrenergic.
Uptake of [3H]glycine and [14C]glutamate by cultures of chick spinal cord
Authors: Cho Y. D. , Martin R. O. , Tunnicliff G. 
Published: December 2014

1. Spinal cord explants from chick embryos, grown in culture for up to 16 days, rapidly accumulated [3H]glycine and [14C]glutamate when incubated at 25° C in a medium containing either 2 × 10−10
M glycine or 4·8 × 10−8
M glutamate.2. After 90 min incubation, a tissue/medium ratio of 60:1 and 20:1 was attained for [14C]glutamate and [3H]glycine respectively.3. The uptake systems, in addition to requiring sodium ions in the medium, were temperature sensitive, showed saturation kinetics, and were inhibited by ouabain.4. For the glutamate and glycine accumulation the Km value was 4·3 × 10−5 and 4·1 × 10−5
M respectively, indicating that a high affinity uptake process is involved.5. The rate of accumulation of both glutamate and glycine increased in cultures between the ages of 3 and 10 days thus matching their morphological development.6. In light of previous evidence, the demonstration of an active transport mechanism for both glutamate and glycine in spinal‐cord‐cultures that also shows a relationship with morphological maturity, suggests that these two amino acids may play a major role in spinal cord function.
The maximum derivatives of left ventricular pressure and transverse internal diameter as indices of the inotropic state of the left ventricle in conscious dogs
Authors: Barnes G. E. , Bishop V. S. , Horwitz L. D. , Kaspar R. L. 
Published: December 2014

1. In normal, conscious dogs,
I.V. infusion of isoprenaline caused inases in heart rate and the maximal derivatives of left ventricular pressure (dP/dt max) and left ventricular internal diameter (dD/dt max). The changes in both derivatives were linearly related to the increase in heart rate.2. Increments in heart rate produced by right atrial pacing caused only minimally significant increases in both dP/dt max and dD/dt max at heart rates of 180 beats/min. Increases in heart rate, with end diastolic diameter maintained constant, resulted in small but significant increases in dP/dt max and no significant increase in dD/dt max.3. Increasing preload by volume infusion had little effect on either derivative, while increasing afterload by phenylephrine administration produced a small but significant increase in dP/dt max and no change in dD/dt max.4. Both dP/dt max and dD/dt max are equally reliable as indices of the inotropic state of the myocardium and are minimally influenced by changes in preload, afterload or heart rate.
The binding of labelled saxitoxin to the sodium channels in nerve membranes
Authors: Henderson R. , Ritchie J. M. , Strichartz G. R. 
Published: December 2014

1. Tritium labelled saxitoxin has been prepared and purified, and its binding both to intact rabbit vagus nerves and to a solubilized preparation of garfish olfactory nerve membranes has been examined.2. In intact and solubilized nerves there is a saturable binding component of magnitude equal to that previously obtained for labelled tetrodotoxin.3. This component of bound saxitoxin is displaced competitively by tetrodotoxin, and it is concluded that the two toxins bind to the same site.4. The saturable saxitoxin (STX) interaction with the nerve membrane is reversible and can be described by the equation STX + R ⇌ STX.R where R is the binding site or receptor. With the solubilized preparation of garfish nerve membranes the saxitoxin‐receptor reaction rates are almost four times faster than those of tetrodotoxin. The half‐life of the saxitoxin‐receptor complexes is 13 sec compared with 44 sec for the tetrodotoxin‐receptor complex.5. A number of agents were tested for their ability to displace the labelled saxitoxin. Calcium and thallous ions each produced significant reversible reduction in binding, with apparent equilibrium dissociation constants of about 20–30 m
M. Toxin binding is also inhibited reversibly in acidic solutions by protons competing with toxin for a binding site with a pKa of 5·6–5·9. All three ions are known to block sodium currents in myelinated nerve at similar concentrations. Our experiments indicate that they do so at the site of toxin binding.6. Lidocaine and veratrine do not affect the binding of saxitoxin.
The intervals between miniature end‐plate potentials in the frog are unlikely to be independently or exponentially distributed
Authors: Cohen Ira , Kita Hiroshi , Van Der Kloot William 
Published: December 2014

1. It has been suggested that spontaneous quantal release of transmitter at the neuromuscular junction is a Poisson process. One logical argument against accepting the Poisson hypothesis is that so far relatively few intervals between miniature end‐plate potentials (min.e.p.p.s) have been studied in any single experiment. Release is known to occur from many sites on the nerve terminal, so many intervals must be studied before drawing any conclusions about the timing of release from the individual sites. Moreover, the statistical methods that have been used are relatively insensitive to deviations from Poisson predictions.2. The Poisson hypothesis is evaluated with respect to three major criteria:(a) The fit to the exponential distribution is analysed by five goodness of fit tests which were applied to eleven sets of data, showing that it is unlikely that the data sets were generated by an exponential distribution.(b) The independence of intervals is assessed in two ways. First, the autocorrelogram of intervals is constructed. This shows an excess of significant positive correlations beyond the 5% limits of the Poisson expectation. Secondly, the unsmoothed power spectrum is calculated, and compared to the Poisson prediction by means of the modified mean test. Again, most sets deviate significantly from the Poisson expectation. It is unlikely that the intervals are independent.(c) The possibility of simultaneous occurrences is evaluated by construction of the amplitude histogram of min.e.p.p.s. In all sets the Poisson prediction for the frequency of multiples of the unit height was exceeded by the empirical data sets. The over‐all conclusion is that the process which generates spontaneous releases is unlikely to be Poisson.
Post‐tetanic effects in motor units of fast and slow twitch muscle of the cat
Authors: Bagust J. , Lewis D. M. , Luck J. C. 
Published: December 2014

1. Motor unit twitches were examined in cat flexor digitorum longus (fast twitch) and soleus (slow twitch) muscles. The time course of the effects of a standard tetanus on the peak twitch tension was plotted and the maximal potentiation or depression (the post‐tetanic ratio) was measured.2. The post‐tetanic ratio decreased continuously as the twitch time to peak of motor units increased; motor units from flexor digitorum longus and soleus could be described as a single population. The closest approximation to a linear relationship was found by plotting post‐tetanic ratio against the reciprocal of time to peak.3. The post‐tetanic ratio was also related to the ratio of tetanic to twitch tension. The time of maximum potentiation or depression occurred between 1 and 11 sec, but this variable was unrelated to the time to peak or any other characteristic of the motor unit.
Capacitance effects and blood reservoir function in the splanchnic vascular bed during non‐hypotensive haemorrhage and blood volume expansion in anaesthetized cats
Authors: Greenway C. V. , Lister G. E. 
Published: December 2014

1. These experiments were designed to measure how much blood is mobilized from or pooled in the liver, spleen and gastro‐intestinal tract to compensate for a haemorrhage or infusion of blood.2. Hepatic volume, splenic weight and intestinal volume were recorded in cats anaesthetized with sodium pentobarbitone. Whole blood was removed or infused at rates of 0·5–0·6 ml. kg−1.min−1 until 10 ml./kg (19% blood volume) had been removed or 18 ml./kg (34% blood volume) had been infused. These blood volume changes produced only small changes in arterial and portal pressures except after removal of 8 ml./kg (15% blood volume) when arterial pressure began to decrease rapidly.3. With small haemorrhages of up to 4% blood volume, the liver contributed 16%, the gastro‐intestinal tract 23% and the spleen a negligible proportion of the blood volume removed. With haemorrhages of 15% blood volume, the liver contributed 21%, the gastro‐intestinal tract 22% and the spleen 19% of the volume removed; a total splanchnic contribution of 62%.4. During infusions of 5–18 ml./kg (10–34% blood volume), the liver pooled 20%, the gastro‐intestinal tract 40% and the spleen 6% of the volume infused; a total splanchnic contribution of 66%.5. It is concluded that the splanchnic bed mobilizes or pools up to 65% of the volume of blood removed from or infused into the cats. The mechanisms responsible for this blood reservoir function are discussed. While several factors may be involved, it seems likely that a reflex regulation involving atrial receptors and the sympathetic innervation of the splanchnic capacitance vessels is of predominant importance.
A note on the interaction of spontaneous and evoked release at the frog neuromuscular junction
Authors: Barrett Ellen F. , Barrett J. N. , Martin A. R. , Rahamimoff R. 
Published: December 2014

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

1. A reflex increase in heart rate in response to pulmonary vein distension was observed in decerebrate dogs. This increase could not be totally abolished by treatment with both propranolol and bretylium tosylate. Only bilateral cervical vagotomy abolished the reflex increase in heart rate.2. A significant increase in heart rate occurred in a total of seventeen spinal dogs during pulmonary vein distension.3. In seven spinal animals in which blood pressure was maintained by the continuous infusion of noradrenaline, the increase in heart rate could be totally prevented by cervical vagotomy.4. The time course of the increase in heart rate observed in the spinal animals was rapid, reaching maximum expression within 10 sec of pulmonary vein distension. Such a time course is dissimilar from that associated with pulmonary vein distension in intact or decerebrate dogs in which maximum increases in heart rate take 1–3 min to develop.5. It is concluded that the reflex tachycardia resulting from pulmonary vein distension may be mediated by both an efferent sympathetic and an efferent vagal pathway, the relative significance of each component being dependent upon the prevailing autonomic drive existent in the animal at any specific time.
The formation of synapses in regenerating mammalian striated muscle
Authors: Bennett M. R. , Florin T. , Woog R. 
Published: December 2014

1. A histological and electrophysiological study has been made of the formation of synapses in soleus and extensor digitorum longus muscles of adult rats regenerating from minced muscle fragments.2. In the first 8 days of regeneration, myoblast and myotubes formed within the basement membranes of degenerating myofibres.3. Eleven‐ to fourteen‐day regenerates contained fasicles of myotubes and myofibres and both nerves and spontaneous miniature end‐plate potentials (m.e.p.p.s) were observed for the first time, although very few synapses show evoked end‐plate potentials (e.p.p.s).4. Eighteen‐ to twenty‐six‐day regenerates contained. myofibres on which only a single end‐plate could be detected; 30% of these synapses had a normal amplitude—frequency distribution of m.e.p.p.s and subthreshold e.p.p.s whilst at the remainder the e.p.p. was either suprathreshold or did not occur.5. Thirty‐ to sixty‐day regenerates contained myofibres and end‐plates with the same morphological and functional characteristics as those in normal muscle.
Mechanism of anion permeation through the muscle fibre membrane of an elasmobranch fish, Taeniura lymma
Authors: Hagiwara Susumu , Takahashi Kunitaro 
Published: December 2014

1. Properties of anion permeation through the membrane of skeletal muscle fibres of the stingray, Taeniura lymma, were studied with intracellular recording and polarization techniques.2. The Cl conductance of the resting membrane in the normal stingray saline at pH 7·7 is 8–10 times greater than the K conductance.3. The Cl conductance decreases with decreasing external pH, with an apparent pK of 5·3, whereas the K conductance is independent of pH between 4 and 9.4. The Q10 of the Cl conductance is about 2·0, compared with a value of 1·2–1·4 for the K conductance.5. The Cl conductance is proportional to the external Cl concentration when observed after the fibre is equilibrated in the test solution.6. The permeability sequence obtained by potential measurement is SCN > NO3 > Cl = Br > I > ClO3 and the permeability ratio is independent of the mole fraction of anions.7. The conductance sequence determined by total replacement of the external Cl with other anion species differs from the permeability sequence and the conductance observed for partial replacement deviates significantly from that expected from the independence principle.8. Possible mechanisms of anion permeation are discussed.
The accumulative properties of facilitation at crayfish neuromuscular synapses
Authors: Linder T. M. 
Published: December 2014

1. Synaptic facilitation was measured with intracellular recording at two classes of neuromuscular synapses in the opener muscle of the crayfish dactyl by placing a test stimulus at various intervals after either a single conditioning stimulus or a short conditioning train.2. The facilitative effect of one stimulus reaches approximately the same level with both the superficial central and superficial distal synapses. The facilitation decreases smoothly in two phases after the conditioning stimulus at superficial central synapses and in a more complex fashion at superficial distal synapses.3. The two synaptic types differ in the manner in which they add up the facilitative effects produced by each of the stimuli in a short train. With superficial distal synapses the facilitative effects of conditioning stimuli add linearly, while with superficial central synapses the facilitative effects accumulate exponentially.4. The linear addition of facilitation at superficial distal synapses is not altered when the quantal content is lowered by decreasing the external Ca concentration from 13·5 to 3 m
M.5. The rate of decay of facilitation is the same following both one and three conditioning stimuli, even though the facilitation is nearly six times larger in the latter case.6. The results are discussed in terms of mechanisms for synaptic facilitation.
An outflow of acetylcholine from normal and regenerating ventral roots of the cat
Authors: Evans C. A. N. , Saunders N. R. 
Published: December 2014

1. An outflow of acetylcholine (ACh) has been measured from cat ventral roots in situ and in vitro, using standard bio‐assay techniques. The ACh was collected in chambers, filled with physiological solution containing anticholinesterase, which surrounded the root.2. The outflow fell rapidly at first and then progressively more slowly, taking several hours to fall to a level near the assay threshold. The outflow of ACh resulted from cutting a root or from such conventional manipulations as stretching the root or teasing apart root filaments. The outflow could occur either from the end of a root (following cutting) or from along the length of the root (following stretching or teasing). The outflow was only detected in the presence of an anticholinesterase.3. ACh was resynthesized by roots at a rate which was usually rapid enough to maintain their ACh content at its original level in spite of a considerable ACh outflow. In roots subjected to a minimum of interference their ACh content built up to about twice the initial content after 5‐7 hr soaking in eserinized Krebs solution although the total ACh outflow was equivalent to the original ACh content.Roots which were cut or stretched several times within a few hours put out a large amount of ACh and showed a fall in their ACh content below the initial level.4. The time course of sealing of the damaged ends of axons following crushing was assessed by measuring the injury potential for 1–2 hr after crushing at room temperature; in normal roots the half‐time for decline of the injury potential was 91 ± 10 min. This was slower than the rate of decline of the ACh outflow.5. An explanation for the observed outflow of ACh is discussed in terms of diffusion of ACh and sealing of axon ends. It is concluded that much of the ACh in normal ventral root axons is present in a readily diffusible form.6. Similar experiments on roots regenerating 9–10 days after crushing showed that the ACh outflow from regenerating roots was much smaller than from normal axons, although their ACh content was similar. This could have been due to more rapid sealing of the cut regenerating axons since the half‐time for the decline of the injury potential following crushing of the regenerating axons was less than half that in control roots. The alternative possibility is considered that a high proportion of the ACh might be much less diffusible than in normal axons.7. The subcellular distribution of ACh in normal and regenerating peripheral axons is discussed.
Ventilation and sleep state in the new‐born
Authors: Bolton David P. G. , Herman Stephen 
Published: December 2014

1. Ventilation, oesophageal pressure and sleep state were measured in fourteen babies between 25 hr and 7 days of age.2. Trunk plethysmograph records showed that respiratory rate and minute volume were significantly higher in REM sleep than non‐REM sleep. Tidal volume was not significantly altered.3. Tidal volume, respiratory rate and minute volume were all more variable in each baby in REM sleep, both on breath to breath analysis and over successive 20 sec periods.4. Major oesophageal peristaltic activity was observed in REM sleep only.5. In response to a sharp rise in PO2 the tidal volume and minute volume fell significantly by the same proportion in both sleep states. Respiratory rate did not change significantly.
The effect of carbon dioxide in the airways and alveoli on ventilation; a vagal reflex studied in the dog
Authors: Bartoli A. , Cross Brenda A. , Guz A. , Jain S. K. , Noble M. I. M. , Trenchard Diana W. 
Published: December 2014

1. The inhalation of CO2 produces a tachypnoea only in the presence of intact vagus nerves; the present study was designed to examine the mechanism of this phenomenon in the dog.2. Closed‐chest cardiopulmonary bypass was established in dogs weighing 16–24 kg, anaesthetized with chloralose. When the ‘bypass’ was established pulmonary blood flow ceased, PA, CO2 was reduced and the respiratory rate slowed. 3‐10% CO2 in O2 could then be inhaled without change in the level of Pa, CO2 set at the oxygenator.3. The addition of CO2 in these concentrations to the inspired oxygen resulted in an increase in respiratory frequency, maximal at the first breath and sustained for the 1 min period of exposure. The increase in respiratory frequency was due to a shortening of expiratory duration. Inspiratory duration did not change. The response was absent after vagotomy.4. Inert gases in O2, given as a control, had no effect on breathing.5. The effect of raising Pa, CO2 (by increasing the concentration of CO2 in the gas equilibrating the blood in the oxygenator), was primarily to increase tidal volume.6. The ventilatory effect of inspiring CO2/O2 mixtures was shown to be additive to the effect of raising Pa, CO2.7. These experiments show that an afferent vagal reflex originating from the lungs causes tachypnoea, when a dog, on ‘bypass’, inhales low concentrations of CO2 in O2.
The hyperthermic effect of intracerebroventricular cholera enterotoxin in the unanaesthetized cat
Authors: Clark Wesley G. , Cumby H. Rick , Davis Henry E. 
Published: December 2014

1. Cholera enterotoxin was used to evaluate a possible role of endogenous cyclic AMP in production of hyperthermia. Injection of purified toxin (0·10‐1·0 μg in 0·10 ml.) into the lateral cerebral ventricle of unanaesthetized cats caused dose‐related hyperthermic responses. Heating the toxin for 40 min at 90° C abolished its hyperthermic activity.2. Intraventricular administration of dibutyryl cyclic AMP (250‐1000 μg) also caused hyperthermia which, however, was preceded by transient periods of hypothermia and/or excitation in about half of the tests.3. Paracetamol, indomethacin and sodium salicylate inhibited hyperthermic responses to cholera enterotoxin. Paracetamol and indomethacin also inhibited hyperthermia induced by dibutyryl cyclic AMP (sodium salicylate was not tested).4. It is likely that the hyperthermic effect of cholera enterotoxin in the cat is mediated via endogenous cyclic AMP and that the antipyretics inhibit this effect by an action subsequent to the increase in cyclic AMP.5. It is unlikely that prostaglandin‐induced hyperthermia in the cat is mediated via cyclic AMP since these antipyretics do not inhibit this response to prostaglandin E1.