bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis, storage and release of [14C]acetylcholine in isolated rat diaphragm muscles
Authors: Potter L. T. 
Published: December 2014

1. Segments of rat diaphragms were kept in choline‐free media for 4 hr and were then exposed to a physiological concentration of [14C]‐choline (30 μ
M) at 37° C. The synthesis, storage and subsequent release of [14C]acetylcholine by the muscles was assessed by isotopic‐ and bio‐assays after isolation of the transmitter by paper electrophoresis.2. Replacement of endogenous acetylcholine (0·92 μ‐mole/kg) with labelled acetylcholine proceeded slowly at rest, but rapidly during nerve stimulation. [14C]Acetylcholine accumulated most rapidly when hydrolysis of the released transmitter, and thus the re‐use of endogenous choline, was prevented by an esterase inhibitor. Fully replaced stores were maintained during nerve stimulation by synthesis rates sufficient to replenish at least 35% of the store size in 5 min.3 In the presence of hemicholinium‐3, which inhibits choline uptake, acetylcholine stores declined rapidly during stimulation, and residual synthesis was slight, indicating little intraneural choline. Net choline uptake into nerve terminals was estimated from the highest observed synthesis rate and from previous measurements of the number and size of terminals, as 3‐6 p‐mole/cm2 sec.4. Transmitter synthesis was localized in the region of end‐plates, and was reduced to a few per cent of normal 6 weeks after phrenic nerve section. Release experiments suggested that at least half of the acetylcholine in phrenic nerves is in their terminals; from this content and the morphology of the terminals, the average concentration of transmitter in the whole endings would appear to be about 50 m‐mole/l. Homogenization of the muscles freed choline acetyltransferase into solution, but left some [14C]acetylcholine associated with small particles, presumably synaptic vesicles.5. Resting transmitter release was about 0·013% of stores/sec. With 360 nerve impulses at 1‐20/sec, release increased up to 0·43% of stores/sec, and amounted to 3·5–7 × 10−18 moles per end‐plate per impulse. The release rate was unaffected by the doubling of store size which occurred with eserine, but the extra transmitter did help to maintain releasable stores during prolonged stimulation. Experiments with fractional store labelling indicated that newly synthesized acetylcholine was preferentially released.6. Preformed [3H]acetylcholine was not taken up and retained by muscle or nerve cells in the absence of an esterase inhibitor. With eserine present, labelled acetylcholine was taken up uniformly by muscle segments; when eserine was then removed, radioactive acetylcholine remained only near neuromuscular junctions.
The dorsal nucleus of the vagus as a centre controlling gastric motility in sheep
Authors: Howard B. R. 
Published: December 2014

1. A preparation is described for investigating the central nervous control of gastric motility in decerebrate decerebellate sheep.2. The dorsal vagal nucleus has been electrically stimulated in thirty decerebrate sheep, and the effect on the mechanical responses of the different parts of the reticulo‐rumen have been determined.3. In the absence of recurrent rhythmic gastric contractions, punctate electrical stimulation of the dorsal vagal nucleus did not elicit gastric contraction until the intensity of stimulation was sufficiently high to excite efferent vagal fibres.4. Direct stimulation of the vagus nerve, or of motor fibres running from the nucleus to this nerve, always caused contraction of the reticulum, and dorsal and ventral ruminal sacs.5. Electrical stimulation of certain points within the medulla oblongata, during rhythmic gastric motility, inhibited motility for one or more contraction cycles. These inhibitory points lay on a line commencing at the mid‐point of the dorsal vagal nucleus, and extending forward and ventral to this.6. Excitatory responses were less frequent, and were seen along a line running parallel to, but about 1 mm below, the anterior half of the line of maximum inhibition. They usually followed a period of inhibition, were generally shorter in duration, and consisted of a series of small reticular contractions at a rate of about 1/10 sec.7. The presence of a powerful inhibitory influence on the dorsal vagal nucleus, mediated from an area lying anterior to the nucleus, is argued and its probable action at the level of the gastric motor nucleus is discussed.
The development of the metabolic response to thyroxine in the new‐born pig
Authors: Kaciuba-Uscilko Hanna , Legge K. F. , Mount L. E. 
Published: December 2014

1. Rectal temperature and the rate of oxygen consumption in the new‐born pig were measured following the subcutaneous injection of
L‐thyroxine.2. Thyroxine stimulated oxygen consumption during the post‐natal period; both immediate and latent increases were observed.3. The immediate effect occurred after thyroxine, 80 μg/kg, in suckled pigs aged 1‐11 days; it was most marked at about 1‐4 days of age with a peak increase (20%) in oxygen consumption and a rise in rectal temperature at about 4 hr following the injection.4. The peak increase (30%) in oxygen consumption associated with the latent effect of three successive daily injections of thyroxine, 300 μg/kg, occurred at 5‐7 days of age, whether the pigs were first injected at 1 or at 4 days of age.5. It is concluded that there is a high sensitivity to thyroxine in the pig during the first week after birth, when the hormone is not bound to plasma proteins to the same degree as in the older animal.
Reflex inhibition of monosynaptic reflexes by stimulation of type J pulmonary endings
Authors: Deshpande S. S. , Devanandan M. S. 
Published: December 2014

1. Monosynaptic reflexes, evoked from flexor and extensor hind limb muscle nerves in cats anaesthetized with pentobarbitone sodium, were depressed for several seconds after right intra‐atrial injection of phenyl diguanide. Injection of the drug close to the aortic valves did not produce the same effect on the reflex. There was no obvious depression of polysynaptic reflexes on intra‐atrial injection of phenyl diguanide.2. This depression of the monosynaptic reflex was present even after the administration of atropine, which lessened the hypotension due to phenyl diguanide. The blood gas tensions were also measured after the administration of phenyl diguanide, and were not altered to a degree where one would expect the depression to be secondary to a change in arterial gas tensions. The depression was also present in paralysed and artificially ventilated cats.3. The afferent pathway causing this depression of the monosynaptic reflex runs in the vagus nerve, as shown by experiments done before and after vagotomy. Intercollicular decerebration also abolished this inhibition of the monosynaptic reflex.4. Prior intravenous injection of strychnine (0·1 mg/kg) abolished the effect of intra‐atrial administration of phenyl diguanide.5. It was concluded that stimulation of type J pulmonary endings causes a reflex inhibition of monosynaptic reflexes lasting for several seconds via regions of the brain cephalad to the intercollicular level.
The period of susceptibility to the physiological effects of unilateral eye closure in kittens
Authors: Hubel D. H. , Wiesel T. N. 
Published: December 2014

1. Kittens were visually deprived by suturing the lids of the right eye for various periods of time at different ages. Recordings were subsequently made from the striate cortex, and responses from the two eyes compared. As previously reported, monocular eye closure during the first few months of life causes a sharp decline in the number of cells that can be influenced by the previously closed eye.2. Susceptibility to the effects of eye closure begins suddenly near the start of the fourth week, remains high until some time between the sixth and eighth weeks, and then declines, disappearing finally around the end of the third month. Monocular closure for over a year in an adult cat produces no detectable effects.3. During the period of high susceptibility in the fourth and fifth weeks eye closure for as little as 3‐4 days leads to a sharp decline in the number of cells that can be driven from both eyes, as well as an over‐all decline in the relative influence of the previously closed eye. A 6‐day closure is enough to give a reduction in the number of cells that can be driven by the closed eye to a fraction of the normal. The physiological picture is similar to that following a 3‐month monocular deprivation from birth, in which the proportion of cells the eye can influence drops from 85 to about 7%.4. Cells of the lateral geniculate receiving input from a deprived eye are noticeably smaller and paler to Nissl stain following 3 or 6 days' deprivation during the fourth week.5. Following 3 months of monocular deprivation, opening the eye for up to 5 yr produces only a very limited recovery in the cortical physiology, and no obvious recovery of the geniculate atrophy, even though behaviourally there is some return of vision in the deprived eye. Closing the normal eye, though necessary for behavioural recovery, has no detectable effect on the cortical physiology. The amount of possible recovery in the striate cortex is probably no greater if the period of eye closure is limited to weeks, but after a 5‐week closure there is a definite enhancement of the recovery, even though it is far from complete.
Influence of oestrogen on thyroid function in the ewe
Authors: Falconer Ian R. 
Published: December 2014

1. Thyroid activation at oestrus occurs in several species, which may be related to oestrogen secretion occurring at the same time. In the ewe this relationship has been examined by measuring thyroid activity before and after oestrogen administration.2. Measurements have been made of thyroid 131I release rate and protein‐bound 131I concentration in the plasma in normal and ovariectomized ewes and of protein‐bound 125I in plasma from thyroid vein blood in ewes with exteriorized thyroid glands.3. No evidence of an activation of the thyroid by oestrogen was observed in immature ewes or adult oestrous cycle, anoestrous or ovariectomized ewes, given oestrone or oestradiol dibenzoate in doses of 25–1000 μg by injection.4. It was concluded that oestrogen may not be responsible for thyroid activation observed in normal oestrous ewes.
The extraneuronal uptake and localization of noradrenaline in the cat spleen and the effect on this of some drugs, of cold and of denervation
Authors: Gillespie J. S. , Hamilton D. N. H. , Hosie R. Jeanette A. 
Published: December 2014

1. Extraneuronal uptake of noradrenaline (NA) was examined in the cat spleen first by perfusing with NA for 10 min, followed by a 2‐min wash to clear the extracellular fluid, then measuring the amount retained, its subcellular distribution and the tissue components involved as revealed by the development of the characteristic fluorescence. Secondly, thin spleen slices were exposed to NA in vitro and the development of fluorescence in various structures, particularly arterial smooth muscle, measured.2. The cat spleen accumulated large quantities of NA and this, like the development of fluorescence, was concentration‐dependent. After particle separation most of the retained amine appeared in the high‐speed supernatant, with a lesser amount in the coarse granule fraction. There was little amine in either the mitochondrial or microsomal fraction. The microsomal fraction from unperfused spleens was rich in NA, presumably from storage granules from the adrenergic nerves. On an intermittent sucrose density gradient the NA‐rich particles sedimented between 1·0 and 1·5
M sucrose, corresponding to the recently described dense granules from bovine splenic nerves.3. Fluorescence histochemistry revealed several tissues accumulating NA. At an NA concentration of 10−5 g/ml., arterial smooth muscle and endothelium showed intracellular fluorescence; at 10−4 g/ml., collagen, the perimeter of the smooth muscle cells of the capsule‐trabecula‐vein system and the reticular cells forming the framework of the spleen developed fluorescence. In the reticular cells the fluorescence was intracellular. The fluorescence pattern on the perimeter of non‐arterial smooth muscle corresponded to the pattern of basement membrane as shown by PAS staining. The red pulp, lymphoid tissue and the phagocytic cells of the ellipsoids did not fluoresce.4. Cooling the tissue to 15° C or less, phenoxybenzamine in a concentration of 5 × 10−5 g/ml. or normetanephrine in a concentration of 10−4 g/ml. prevented both uptake and loss of NA in arterial smooth muscle but had no effect on collagen.5. Chronic post‐ganglionic denervation or reserpine had no effect on the development of fluorescence in any extraneuronal tissue.
Depression of transmitter release at the neuromuscular junction of the frog
Authors: Betz W. J. 
Published: December 2014

1. Depression of transmitter release produced by preceding conditioning stimulation was studied at the frog's neuromuscular junction.2. Depression occurred when transmitter release was restricted to a short length of nerve terminal, or when release was initiated by electrotonic depolarization of the terminals after action potentials were abolished by tetrodotoxin.3. Quantitative studies revealed a non‐linear relationship between the estimated magnitude of ‘zero‐time’ depression and the amount of transmitter released by conditioning stimulation.4. Two stimuli separated by 20–200 msec were given and the ratio of the end‐plate potential amplitudes (V2/V1) was measured. This amplitude ratio increased during depression produced by stimuli preceding the test pair.5. These observations may be explained by assuming that depression is associated with a reduction in release probability as well as a depletion of transmitter available for release.
Centrifugal dorsal root discharges induced by motoneurone activation
Authors: Decima E. E. , Goldberg L. J. 
Published: December 2014

1. It has been confirmed that antidromic stimulation of motoneurones in the cat lumbar cord can induce, when properly conditioned, a centrifugal discharge in dorsal root afferent fibres.2. The effective conditioning can be (a) an orthodromic volley to the same or an adjacent dorsal root, (b) a volley to the dorsal column one or two segments above the tested level, or (c) a natural stimulus applied to the ipsi‐ or contralateral hind limb.3. The conditioning stimulus acts by increasing presynaptic excitability; the peak of its effect (maximum presynaptic depolarization) occurs 7–10 msec after the arrival of the conditioning volley to the cord and then quickly decays.4. A large antidromic field potential in the ventral horn is not necessary for the production of a centrifugal dorsal root discharge. Activation of a ventral root filament of approximately 100 μ in diameter can still induce such a discharge in a single dorsal root fibre. Furthermore, antidromic stimulation of the remaining fibres of the same ventral root cannot affect the terminals activated by the thin ventral root filament.5. The phenomenon of motoneurone—presynaptic interaction was obtained in different types of experimental preparations: acute and chronic spinal, anaemic and midcollicular decerebrate, animals with intact supraspinal centres, and one animal without acute laminectomy.
Distribution of ions and electrical potential differences between mother and foetus at different gestational ages in goats and sheep
Authors: Mellor David J. 
Published: December 2014

1. Potential differences associated with the compartments of goat and sheep conceptuses have been measured in vivo and in vitro during the last half of gestation and the osmolarity, and the [Na+], [K+], and [Cl−] of maternal and foetal plasma and amniotic and allantoic fluid taken from these animals were determined.2. The potential difference (p.d.) patterns of both goats and sheep were the same.(a) The transplacental p.d. was about 71 mV (foetus negative) in the goat, and about 51 mV (foetus negative) in the sheep.(b) The amniotic fluid p.d. (i.e. the p.d. measured between the maternal extracellular fluid and the amniotic fluid) decreased as gestation advanced (from 110 to 70 mV in the goat, and 90 to 50 mV in the sheep) and was equal to the sum of the transplacental p.d. and a p.d. between the foetal blood and the amniotic fluid. The amniotic fluid was negative relative to both maternal and foetal blood.(c) An allantoic fluid p.d. (measured between the maternal extracellular fluid and the allantoic fluid) of about 107 mV in the goat, and about 96 mV in the sheep, was equal to the sum of the transplacental p.d. and a p.d. between the foetal blood and the allantoic fluid. The allantoic fluid was negative relative to both maternal and foetal blood.(d) The results suggest that p.d.s of the fluid sacs arise from activity between the foetal fluids and the blood perfusing the foetal membranes, and not from activity across the full thickness of the foetal membranes.3. The ionic concentrations were considered in relation to the electrochemical gradients found between the maternal and foetal fluid compartments to determine whether the ions were distributed according to electrochemical equilibrium.(a) It seems that ions in the amniotic fluid tend to equilibrate with foetal plasma, and not with maternal plasma or allantoic fluid, that changes in the [Na+] and [K+] of amniotic fluid can be accounted for largely in terms of passive factors, and that variations in the [Cl−] are associated with activity of an electrogenic Cl− pump directed from the foetal blood into the amniotic fluid.(b) It appears that ions in the allantoic fluid can exchange with those of both maternal and foetal plasma, that an electrogenic pump effects absorption of Na+ from the allantoic fluid into the foetal blood, and that the [K+] and [Cl−] of allantoic fluid are maintained largely by passive exchange under the action of electrochemical gradients between maternal plasma and allantoic fluid, and between foetal plasma and allantoic fluid.4. The results considered in the context of Na+ passage between mother and foetus call in question the general assumption that all Na+ reaches the foetus by passing across the placenta.
Voltage clamp experiments on ventricular myocardial fibres
Authors: Beeler G. W. , Reuter H. 
Published: December 2014

1. A voltage clamp method utilizing a sucrose gap and glass microelectrodes was developed and used to study dog ventricular myocardial fibre bundles. The limitations and the reliability of this method are demonstrated by a series of tests.2. A dynamic sodium current, excited at membrane potentials more positive than −65 mV, was measured. The equilibrium potential for this large, rapid inward current depends directly on [Na]o, shifting 29·0 ± 2·3 mV (±
S.E. of mean), as opposed to a theoretically expected value of 30·6 mV, when [Na]o is reduced to 31% of normal.3. Sodium current is inactivated by conditioning depolarizations. Complete inactivation occurs with conditioning potentials more positive than −45 mV, and 50% inactivation occurs at about −55 mV. The location of the inactivation curve shifts along the voltage axis, when [Ca]o is varied between 0·2 and 7·2 m
M.4. A second, much smaller and slower net inward current, with a threshold around −30 mV, and an equilibrium potential above +40 mV was also observed.5. The ‘steady‐state’ current—voltage relationship (after 300–600 msec) exhibits inward‐going (anomalous) rectification with negative slope between −50 and −25 mV.6. A small, very slowly developing component of outward current was observed at inside positive potentials. The equilibrium potential for this current, although slightly dependent on [K]o, is neither identical with the potassium equilibrium potential nor with the resting potential in normal Tyrode solution.7. Anatomical limitations, primarily resistance in the extracellular space within the bundle, prevent complete characterization of the rapid, large sodium current, but do not limit the application of the clamp method to the study of other, smaller and slower currents. The evidence for this is discussed extensively in the Appendix.
Membrane calcium current in ventricular myocardial fibres
Authors: Beeler G. W. , Reuter H. 
Published: December 2014

1. A slow inward current in ventricular preparations of the dog heart can be measured by the voltage clamp method without interference from the initial rapid sodium current if the sodium system is inactivated by conditioning depolarization.2. The slow inward current is very sensitive to variation in [Ca]o. It occurs above the equilibrium potential of INa immediately after changing the bathing fluid to a sodium‐free solution and persists under this condition for a long time without much alteration, while INa is rapidly abolished. Tetrodotoxin and [Mg]o have no effect on this current component. These results strongly support the view that the slow inward current in cardiac tissue is carried by calcium ions.3. The threshold for initiation of the calcium current is around −35 mV in Tyrode solution and is shifted to more negative potentials by either increasing [Ca]o or reducing [Na]o.4. Calcium sensitive inward current tails associated with repolarization are assumed to represent a proportional measure of calcium conductance activated during the preceding depolarization. Calcium conductance declines rapidly with time in the inside negative potential range and slowly at positive potentials. The time constants for this ‘inactivation’ process vary between 40 and 700 msec in the potential range −35 to +50 mV.5. By using instantaneous current—voltage relations the reversal potential of calcium current was estimated to be about +60 mV in normal Tyrode solution. As shown in the Appendix, however, the calcium equilibrium potential cannot be considered to be constant.6. The importance of the calcium current for the plateau of the cardiac action potential is discussed.
The influx of orthophosphate into squid giant axons
Authors: Caldwell P. C. , Lowe A. G. 
Published: December 2014

1. The influx of 32P, applied externally as orthophosphate, into the axoplasm of squid giant axons has been studied.2. An average orthophosphate influx of 20·9 f‐mole/cm2.sec is obtained if the 32P found in the axoplasm is assumed to be indicative of orthophosphate which has crossed the axolemma.3. The influx does not show very much dependence on external orthophosphate concentration in the range 0·02–0·5 m
M.4. The influx is reduced by cyanide, 2,4‐dinitrophenol, ouabain and by the absence of external potassium.5. The 32P appears to arrive in the axoplasm as orthophosphate.6. It is concluded that there is an inward movement of orthophosphate into the axons which is mediated by an active transport process and that this may have some connexion with the active transport of sodium and potassium.