bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of catecholamines on the neuromuscular junction in the rat diaphragm
Authors: Kuba K. 
Published: December 2014

1. The effects of noradrenaline, adrenaline and isoprenaline on neuromuscular transmission in the rat diaphragm and the influence of adrenergic blocking agents on these actions were investigated.2. The resting membrane potential of the muscle fibre was increased by adrenaline (5 × 10−6‐10−5 g/ml.) and isoprenaline (5 × 10−6 g/ml.) up to 3‐4 mV, but noradrenaline (5 × 10−6‐10−5 g/ml.) had little effect.3. The amplitude and the half‐decay time of the end‐plate potential (e.p.p.) were increased by noradrenaline (1 × 10−6 g/ml.), adrenaline (1 × 10−7‐10−5 g/ml.) and isoprenaline (1–5 × 10−6 g/ml.). The potentiation of the amplitude of the e.p.p. was greater with noradrenaline than with adrenaline and isoprenaline.4. Noradrenaline (5 × 10−6 g/ml.) increased the frequency of miniature end‐plate potentials (m.e.p.p.), but not their amplitude. However, isoprenaline (5 × 10−6 g/ml.) increased the amplitude of m.e.p.p.s without change in frequency. Adrenaline (5 × 10−6 g/ml.) increased both frequency and amplitude of m.e.p.p.s.5. Adrenaline (5 × 10−6 g/ml.) and isoprenaline (5 × 10−6 g/ml.) increased the input resistance of the muscle membrane. The effect was blocked by the β‐blocker, pronethalol (2 × 10−6 g/ml.), but not by the α‐blocker, phentolamine (2 × 10−6 g/ml.). Noradrenaline did not change the input resistance of the muscle fibre.6. Noradrenaline (5 × 10−6 g/ml.) and adrenaline (5 × 10−6 g/ml.) augmented the extracellularly recorded end‐plate current (e.p.c.), but they had no effect on the half duration, nor on the action current (a.c.) of the nerve terminal, nor on the synaptic delay. Isoprenaline (5 × 10−6 g/ml.) had no effect on any of these parameters. The actions of noradrenaline and adrenaline on e.p.c. were abolished by phentolamine (2 × 10−6 g/ml.), but not by pronethalol (2 × 10−6 g/ml.).7. Adrenaline (5 × 10−6 g/ml.) and isoprenaline (5 × 10−6 g/ml.) enhanced the amplitude of the acetylcholine potential elicited by iontophoretic application of acetylcholine. No such effect was produced by noradrenaline (5 × 10−6 g/ml.).8. It was concluded that noradrenaline acts on the nerve ending increasing the release of transmitter, and that isoprenaline acts on the post‐synaptic membrane enhancing the input resistance, while adrenaline has both presynaptic and post‐synaptic actions. The effect on the nerve ending is concerned with the α‐action, whereas that on post‐synaptic membrane with β‐action of the catecholamines.
Sodium and potassium conductance changes during a membrane action potential
Authors: Bezanilla Francisco , Rojas Eduardo , Taylor Robert E. 
Published: December 2014

1. A method for turning a membrane potential control system on and off in less than 10 μsec is described. This method was used to record membrane currents in perfused giant axons from Dosidicus gigas and Loligo forbesi after turning on the voltage clamp system at various times during the course of a membrane action potential.2. The membrane current measured just after the capacity charging transient was found to have an almost linear relation to the controlled membrane potential.3. The total membrane conductance taken from these current—voltage curves was found to have a time course during the action potential similar to that found by Cole & Curtis (1939).4. The instantaneous current voltage curves were linear enough to make it possible to obtain a good estimate of the individual sodium and potassium channel conductances, either algebraically or by clamping to the sodium, or potassium, reversal potentials. Good general agreement was obtained with the predictions of the Hodgkin—Huxley equations.5. We consider these results to constitute the first direct experimental demonstration of the conductance changes to sodium and potassium during the course of an action potential.
Colour vision in blue‐cone ‘monochromacy’
Authors: Alpern M. , Lee G. B. , Maaseidvaag F. , Miller S. S. 
Published: December 2014

1. Atypical (blue cone) monochromats show two action spectra when tested by the increment threshold method of Stiles with ‘central’ fixation. One spectrum peaks near 450 nm and has the spectral characteristics of normal blue cones. The other resembles rhodopsin (π0) modified slightly by photostable macular pigment.2. Under some circumstances such observers are dichromats. There is a neutral point (matched to Illuminant ‘C’) in the neighbourhood of 460–470 nm.3. The spectral colour matching functions using two primaries have been measured on three such subjects. They can be fit reasonably well, although imperfectly, by linear combinations of π0 and π1. The chromaticity co‐ordinates have been calculated according to the convention of W. D. Wright and compared to the results predicted from π0 and π1. The comparison suggests that part of the imperfections of the colour matching function fit is due to prereceptor differences (e.g. macular pigment) between the blue‐cone monochromats and the hypothetical π0, π1 observer.4. Colour matches made at high light levels continue to hold when the intensity of the field is reduced below the cone threshold.5. Therefore one of the visual pigments participating in the colour matches has an action spectrum which is not measurably different from that of the rod pigment rhodopsin.6. Increment threshold measurements show that the mechanism which has the rhodopsin action spectrum has the directional sensitivity of cones, not rods.7. Blue test threshold during dark adaptation after a full bleach follow a bipartite exponential recovery curve. The first exponential has a time constant of 1 min, the second 2 min. By comparing these curves to the increment thresholds it is possible to relate the first to the π1, the second to the π0 cones.8. Using a broad band blue gelatin filter in the measuring light of the retinal densitometer and studying the same retinal region tested in 7 it is possible to follow the regeneration of a pigment after a full bleach which has an exponential recovery with a time constant of 1·0 min. With a yellow green filter in the measuring light the exponential recovery observed after a full bleach has a time constant of 2·0 min.9. One of the two visual pigments participating in the colour matches resides in receptors which have the action spectrum, the directional sensitivity and probably the dark adaptation curve of normal blue cones.10. The other resides in receptors which have the action spectrum of normal rods but the directional sensitivity and the dark adaptation curve of normal red and green cones.
Tetanic and post‐tetanic rise in frequency of miniature end‐plate potentials in low‐calcium solutions
Authors: Miledi R. , Thies R. 
Published: December 2014

1. Miniature end‐plate potentials (min.e.p.p.s) were recorded intracellularly from frog neuromuscular junctions.2. The ‘phasic’ release of transmitter which is directly related to nerve impulses was suppressed by withdrawal of Ca from the external medium plus addition of Mg.3. Under these conditions, min.e.p.p.s continued to be discharged even when EGTA was added, although in this case min.e.p.p. frequency appeared to decrease to about half the rate in normal Ringer.4. Tetanic stimulation of the nerve approximately doubled the rate of min.e.p.p.s even in Ca‐free solutions with EGTA added.5. The tetanic increase in frequency was greater without EGTA and greater still with some Ca added. Therefore, it is concluded that the tetanic rise in min.e.p.p. frequency can occur even in the absence of the immediate ‘phasic’ release of transmitter normally induced by nerve impulses; and that the magnitude of the increase is related to Ca concentration.A possible relation between ‘phasic’ and ‘residual’ effects of nerve impulses is described.
Properties of ‘two‐tone inhibition’ in primary auditory neurones
Authors: Arthur R. M. , Pfeiffer R. R. , Suga N. 
Published: December 2014

1. Properties of two‐tone inhibition in primary auditory neurones of cats were studied with phase‐locked sound stimuli. One sound was a continuous tone at the best frequency of a given neurone, and the other, a tone burst which was changed in amplitude, frequency, and phase relative to the continuous tone.2. The tone burst which caused two‐tone inhibition had either an excitatory or no effect when it was delivered alone. Inhibitory areas commonly appeared on both sides of the excitatory area when the best frequency was higher than a few kc/s.3. Two‐tone inhibition began and ceased within a few milliseconds of the onset and termination of the excitation caused by a tone burst. The degree of inhibition was greatest at the beginning of the tone burst and reached a plateau within 500 msec. The discharge rate during inhibition could be lower than the rate for either tone alone or for spontaneous activity. At the termination of inhibition, prominent rebound in the discharge rate was found.4. With an increase in amplitude of a tone burst, for either a fixed or equally increased continuous tone, the discharge rate during inhibition decreased to a minimum and then began to increase. That is, the degree of inhibition was non‐monotonically related to the sound level.5. Compound period histograms of discharges during inhibition showed that single neurones usually carried information about the combined wave form of the two tones. The information about each tone was, however, modified by the inhibitory phenomenon in both amplitude and phase from that indicated by the compound period histograms for the individual tones.6. Possible mechanisms and functional significance of two‐tone inhibition are discussed.
Inward and delayed outward membrane currents in isolated neural somata under voltage clamp
Authors: Connor J. A. , Stevens C. F. 
Published: December 2014

1. Membrane current—voltage relationships were investigated under voltage clamp conditions in isolated neural somata of marine gastropods.2. Step depolarizations from the resting potential produce an initial inward current followed by a delayed outward current.3. Inward current appears to be carried by both sodium and calcium ions and displays time and voltage dependent properties similar to those of other excitable membranes.4. Activation and deactivation of the delayed outward current follow a more complicated time course than that of a single exponential raised to a power but can be fitted by the product of two exponential functions.5. Delayed outward current inactivation proceeds with a time constant which decreases as membrane voltage is made more positive. The steady‐state levels of inactivation as a function of membrane voltage are related by an S‐shaped curve similar to that for K inactivation in squid giant axon.
Pulmonary vasodilator and vasoconstrictor actions of carbon dioxide
Authors: Barer Gwenda R. , Shaw J. W. 
Published: December 2014

1. Three preparations were used to study the actions of CO2 on the pulmonary vasculature: isolated rat and cat lungs perfused at a constant flow rate with homologous blood and a lobe of cat lung perfused at a constant flow rate in vivo. In all three changes in pulmonary artery pressure (PPa) reflected changes in pulmonary vascular resistance.2. In the isolated rat lung CO2 caused vasodilatation when vascular tone was high. The lung was first ventilated with N2 causing a rise in PPa. CO2 caused vasodilatation during hypoxia whether the initial blood CO2 level was low or normal and in spite of a fall in blood pH which usually augments the constrictor action of N2.3. In the rat lung ventilation with CO2 from the control state usually caused weak vasoconstriction. Reducing blood pH with acids also caused weak vasoconstriction while alkali caused vasodilatation.4. The over‐all effect of CO2 on the pulmonary vasculature depends on a balance between a vasoconstrictor action probably caused by carbonic acid and vasodilatation caused by some other property of the molecule. The dilator action is powerful in the isolated rat lung.5. By contrast, in both cat lung preparations, no direct evidence for a vasodilator action of CO2 was obtained. Ventilation with CO2 when vascular tone was raised by hypoxia, drugs or acids caused further vasoconstriction. From the control state CO2 caused strong vasoconstriction.6. Indirect evidence from other work suggests that a pulmonary vasodilator action of CO2 exists in the cat but is usually masked by the strong vasoconstrictor action of carbonic acid. In life the dilator mechanism may be important when pH changes caused by CO2 are minimized by renal compensation.
Contractile and electrical responses of vagus‐innervated frog sartorius muscles
Authors: Landmesser Lynn 
Published: December 2014

1. Frog sartorius muscles were transplanted to the thoracic region and re‐innervated by the gastric vagus nerve. Contractile responses of the re‐innervated muscles were studied. Micro‐electrodes were used to measure electrical properties of the muscle fibre membrane. Histological studies of the sartorius and vagus nerves and re‐innervated muscles were also carried out.2. Autonomic nerve fibres of the gastric vagus form functional connexions with the skeletal muscle fibres. Such vagus‐innervated muscle fibres do not atrophy.3. Neither the contractile nor the passive electrical properties of the muscle fibres are altered by vagal innervation.4. Synaptic transmission is quantal in nature and describable by a Poisson distribution as at normal sartorius junctions. The muscle fibres, however, do show extensive multiple‐innervation, and unlike normal sartorius junctions, vagus‐muscle junctions have a low quantal content and show a long‐lasting facilitation.5. Properties of the vagus nerve fibres apparently are not altered by synapsing with skeletal muscle fibres. They remain small diameter and have high threshold for electrical stimulation.6. The ability of these nerve and muscle fibres to influence each other is rather limited in the adult amphibian.
The contribution of the adrenal gland to the total amount of progesterone produced in the female rat
Authors: Fajer A. B. , Holzbauer Margarethe , Newport Helen M. 
Published: December 2014

1. The amount of progesterone contained in both adrenal glands of a rat was similar to or larger than the amount of progesterone in the ovaries of the same rat. This was found in unstressed rats, in stressed rats and also in pregnant rats.2. After ether anaesthesia and exsanguination the adrenal progesterone content was increased by 75%; the ovarian progesterone content remained unchanged.3. In contrast, prolonged operative stress resulted in a rise in the ovarian content of progesterone and 20‐dihydroprogesterone whereas the adrenal progesterone content of these rats was lower than that of unstressed rats.4. The rate at which progesterone was secreted by the adrenal glands of stressed rats was similar to the ovarian progesterone secretion rate. Rats which were kept under mild stress conditions before the experiment showed higher adrenal progesterone secretion rates.
Recurrent inhibition of interneurones monosynaptically activated from group Ia afferents
Authors: Hultborn H. , Jankowska Elẓbieta , Lindström S. 
Published: December 2014

1. Interneurones monosynaptically excited from large muscle spindle (Ia) afferents and inhibited from motor axon collaterals were searched for in the lumbar spinal cord of the cat.2. Monosynaptic Ia excitation was found in sixty‐seven of sixty‐nine interneurones inhibited by antidromic volleys. These interneurones were excited from Ia afferents from one or a few muscles (mainly close synergists). Volleys in high threshold muscle and skin afferents (FRA) evoked polysynaptic excitation or inhibition. Weak inhibition from Ia afferents (from antagonists to those giving Ia excitation) was seen in a few cells. Monosynaptic excitation was evoked from the ventral quadrant of the spinal cord and polysynaptic excitation from the dorsal quadrant.3. Inhibition from motor axon collaterals was evoked with a latency (1·2–2·0 msec) suggesting a disynaptic linkage and had the same time course as in motoneurones. It prevented synaptic activation of 60% of interneurones and decreased the firing index and delayed generation of spikes in the remaining.4. The interneurones with convergence of monosynaptic Ia excitation and inhibition from motor axon collaterals were found in the ventral horn dorsomedial to motor nuclei. No inhibition by antidromic volleys could be detected in interneurones located in intermediate nucleus and activated monosynaptically from Ia, Ib, group I or cutaneous afferents.5. It was concluded that the ventral Ia interneurones inhibited by volleys in recurrent motor axon collaterals mediate the reciprocal Ia inhibition to motoneurones.
Intestinal transfer of choline in rat and hamster
Authors: Sanford P. A. , Smyth D. H. 
Published: December 2014

1. The transfer of choline was studied with sacs of everted intestine of rat and hamster.2. The choline transfer can be divided into two components, a diffusion process and a saturable process. The latter plays a relatively greater part at low concentrations of choline, which include the physiological concentration in the plasma. The saturable process is better seen in the hamster than in the rat.3. Intestinal transfer of choline is influenced by substances altering the availability of energy in the cell, and by some substances chemically or pharmacologically related to choline. These findings are consistent with some kind of specific mechanism for choline transfer.4. Part of the choline taken up by the cell appears as a metabolite not yet identified. The formation of the metabolite is a saturable process and is abolished by anaerobic conditions and by homogenization.5. The results are also discussed in relation to parameters of transfer.
Configuration dependence of scotopic spatial summation
Authors: Sakitt B. 
Published: December 2014

1. Psychophysical experiments were done under conditions of complete dark adaptation, 7° in the human temporal retina, using blue‐green flashes brief enough to be within the range of complete temporal summation.2. Frequency‐of‐seeing experiments were done for two 3·4′ squares separated by 20′ or 23′ and for each square separately. The results were consistent with the hypothesis that the squares acted independently in determining the absolute threshold. There was no observable summation occurring between them.3. The absolute threshold (50% seeing) for two 3·4′ squares (the centre‐to‐centre separation varied from 3·4′ to 56′) was measured relative to the absolute threshold for just one such square. It required more photons at the cornea at threshold for two spots than for one such spot, except when they were actually touching.4. The same subject, in the same retinal region and under otherwise identical test conditions, showed complete spatial summation at absolute threshold for circular spots up to 30′ in diameter.5. Similar experiments were done on other subjects using 3·4′ squares and lines of width 3·4′. All subjects showed complete summation at absolute threshold for lines 34′ long. All showed lack of spatial summation for two squares unless the two squares touched to form a rectangle.6. The absolute threshold for N small spots was compared to the absolute threshold for 1 spot, where N varied from 2 to 25. Again complete spatial summation broke down even when all the spots lay within the Ricco area.7. It was shown that the results are inconsistent with the hypothesis of a linear output and a linear summation of excitations.8. Various hypotheses are examined and it is shown that no simple hypothesis can explain all the results. The conclusion is that spatial summation at absolute threshold is configuration dependent.
Intracellular concentrations of sodium, potassium and chloride in the lactating mammary gland and their relation to the secretory mechanism
Authors: Linzell J. L. , Peaker M. 
Published: December 2014

1. The intracellular (
I.C.) concentrations of Na, K and Cl in mammary cells from lactating guinea‐pigs have been calculated from the analysis of fresh tissue and the measurement of the extracellular (
E.C.) space with [14C]sucrose and the milk content with [14C]lactose.2. Assuming that alveolar milk has the same concentration as teat milk, the intracellular concentrations were calculated to be K 115, Na 42 and Cl 66 m‐equiv. l−1 intracellular water.3. Intracellular concentrations were also calculated in slices incubated in Krebs—bicarbonate medium plus glucose. There was a large increase in the sucrose (
E.C.) space and a rise in total tissue [Na] and [Cl]. On the assumption that the medium had equilibrated with the milk space as well as the
E.C. space, the calculated
I.C. concentrations of Na (43 m‐equiv. l−1), and Cl (62) were very similar while [K] was somewhat higher (143 m‐equiv. l−1
I.C. water).4. The calculated
I.C. concentrations of all three ions are all higher than in milk but the ratios between them are almost identical.5. Similar figures for the
I.C. concentrations of Na, K and Cl have been obtained in the goat, cow and sheep mammary tissue incubated in vitro.6. Moderate changes in the concentrations of Na, K and Cl in the external medium had no effect on cell composition but during incubation without ions [14C]sucrose became distributed throughout the total tissue water indicating that sucrose had entered the
I.C. compartment.7. Acetazolamide (10−2
M), aldosterone (1·4 × 10−6
M) and, in some experiments, lack of glucose lowered
I.C. [Cl−], but oxytocin, vasopressin and low doses of insulin had no effect.8. The data are difficult to reconcile with the hypothesis of Zaks, Natochin, Sokolova, Tanasiichuk & Tverskoi (1965) that freshly secreted milk has the ionic composition of plasma.9. Comparison of
I.C. ion concentrations and the membrane potential between the cells and milk suggests that Na+ and K+ are passively distributed across the apical membrane but that Cl− must be actively held in the cells. Across the basal membrane the data are consistent with the presence of a Na+ pump and with Kinura's (1969) detection of a Na:K ATPase on the basal and lateral membranes. In addition another inward‐facing Cl− pump may exist at this site.
Salt and water permeability of the epithelium of the coprodeum and large intestine in the normal and dehydrated fowl (Gallus domesticus). In vivo perfusion studies
Authors: Bindslev Niels , Skadhauge Erik 
Published: December 2014

1. The transmural net flow of salt and water in the coprodeum and large intestine of normal and dehydrated hens was investigated by means of an intraluminal in vivo perfusion technique.2. The lumen was perfused with a raffinose‐electrolyte solution having a low sodium concentration (Na+ = 1 m‐equiv/l.). The osmolality of the solution was adjusted in the range 66–585 m‐osmolal by adding raffinose. Polyethylene glycol 4000 (PEG) served as a water marker. The experiments permitted estimation of the passive transport parameters: the reflexion coefficient (σ) of the penetrating solutes (predominantly NaCl), the Na+ mobility (ωs), and the osmotic water permeability coefficient (Posm).3. When the luminal fluid had the same osmolality as plasma the net water flow (Jv) was zero, indicating a σ of unity. The net flow of Na+ was zero, (at Jv = 0) and a transmural electric potential difference close to zero was present both in normal and in dehydrated birds. This indicates an ωs of zero. When lumen osmolality was higher than that of plasma, no ‘solvent drag’ effect on Na+ was demonstrated in the serosa to mucosa (s—m) direction.4. The Posm appeared to be independent of the luminal osmolality in the range of ±200 m‐osmolal from plasma osmolality. In normal birds the Posms—m was 3·2 μl./kg.hr.m‐osmolal, the Posmm—s 5·8 μl./kg.hr.m‐osmolal. In dehydrated birds these values were 3·6 and 10·0 respectively. Thus there seems to be rectification of water flow, and it varies with the state of hydration.5. A net K+ flow of 15–50 μ‐equiv/kg.hr in the m—s direction and a net Clμ flow of 10–50 μ‐equiv/kg.hr in the s—m direction were observed. No relationship was observed between the flow of these solutes and the net water flow.