bluuebunny/crossref_metadata_2025_split huggingface dataset:
Negative feedback regulation of noradrenaline release by nerve stimulation in the perfused cat's spleen: differences in potency of phenoxybenzamine in blocking the pre‐ and post‐synaptic adrenergic receptors
Authors: Dubocovich Margarita L. , Langer S. Z. 
Published: December 2014

1. The effects of low concentrations of phenoxybenzamine (8·8 × 10−10 to 2·9 × 10−7
M) on responses and on noradrenaline overflow elicited by nerve stimulation were studied in the perfused cat's spleen.2. In the presence of 8·8 × 10−10
M or 2·9 × 10−9
M phenoxybenzamine there was a significant reduction in responses to nerve stimulation while the overflow of the transmitter did not increase at the two frequencies of stimulation employed: 5 and 30 Hz.3. In the presence of 2·9 × 10−8
M or 2·9 × 10−7
M phenoxybenzamine the responses to nerve stimulation were practically abolished and a significant increase in transmitter overflow was obtained at both frequencies of stimulation. The drug was more effective in increasing transmitter overflow at 5 Hz when compared with 30 Hz.4. The higher effectiveness of phenoxybenzamine in blocking the post‐synaptic α‐receptor when compared with the blockade of the presynaptic α‐receptor that regulates transmitter release is compatible with the view that these two receptors are not identical.5. A second alternative for the difference in effectiveness of phenoxybenzamine is that both types of α receptors are identical, but the spare receptor capacity for the presynaptic adrenergic receptors is higher than that of the post‐synaptic receptors.
The effects of pentobarbitone anaesthesia on the volume and composition of the extracellular fluid of dogs
Authors: Rampton D. S. , Ramsay D. J. 
Published: December 2014

1. The effects of pentobarbitone sodium (Nembutal) anaesthesia in dogs on extracellular fluid and plasma volumes, plasma protein concentration, haematocrit and extracellular fluid electrolyte composition were measured.2. Induction of pentobarbitone anaesthesia caused a rapid rise in extracellular fluid volume, accompanied by decreases in the haematocrit, in extracellular fluid potassium concentration, and in plasma calcium, magnesium, and protein concentrations. There were no significant changes in plasma osmolality and extracellular fluid concentrations of sodium and chloride.3. Extracellular fluid volume did not alter significantly during six hours of anaesthesia, but the haematocrit and extracellular fluid potassium concentration showed an increase towards control values.4. The relevance of these findings to the interpretation of experiments carried out under pentobarbitone anaesthesia is noted.
Studies of radiocalcium efflux in single barnacle muscle fibres: effects of procaine and external divalent cations
Authors: Chen Stephen S. 
Published: December 2014

1. 45Ca efflux from single barnacle muscle fibres loaded with radio‐calcium by microinjection was studied.2. The 45Ca washout curve consisted of three exponential phases with half‐times of 4·8, 12·6 and 111·1 min.3. Removal of external Ca2+ reduced 45Ca efflux by 65%. The 45Ca efflux recovered upon restoring external Ca2+, the magnitude of the recovery being dependent upon the external Ca2+ concentration. 10 m
M procaine was found to reduce the magnitude of the recovery.4. Removal of external Mg2+ resulted in a 38% increase in 45Ca efflux.5. External application of procaine at pH 7·8 caused a dose‐dependent inhibition of 45Ca efflux. The magnitude of the inhibition was reduced in the presence of low external Ca2+ concentrations. 10 m
M procaine at pH 9·3 caused a biphasic effect: inhibition was followed by stimulation.6. Microinjection of 0·5
M procaine caused only inhibition of 45Ca efflux, whereas microinjection of 1·5
M procaine caused stimulation followed by inhibition. These effects were observed at an external pH of 7·8 and 9·3.7. Injection of 100 m
M‐EGTA abolished the stimulatory but not the inhibitory effect produced by procaine injection.8. These results are interpreted as indicating that a major fraction of the 45Ca efflux involves Ca‐Ca exchange which is inhibited by the charged form of procaine in a non‐competitive manner at the external surface of the muscle fibre. The stimulatory action is attributed to release by procaine of Ca2+ from internal binding sites.
Polysensory interactions in the cuneate nucleus
Authors: Atweh S. F. , Banna N. R. , Jabbur S. J. , To'mey G. F. 
Published: December 2014

1. The effects of light flashes or sound clicks on somatic sensory activity in the cuneate nucleus of the cat were studied. Polysensory interactions were demonstrated by means of gross potential recording in the cuneate nucleus or medial lemniscus, single unit recording in the cuneate nucleus, and excitability testing of tract terminals.2. Brief flashes or clicks were found to produce negative (N) and positive (P) waves in the cuneate nucleus similar to those produced by cutaneous stimulation. Furthermore, the P wave evoked by conditioning photic or acoustic stimuli depressed the P wave produced by cutaneous test stimuli.3. Conditioning photic or acoustic stimuli inhibited spontaneously firing cuneate neurones as well as those driven by cutaneous test stimuli.4. Conditioning photic or acoustic stimuli depressed the test discharge in the medial lemniscus evoked by cutaneous test stimuli.5. Micro‐electrode stimulation within the cuneate nucleus evoked an antidromic response in the superficial radial nerve consisting of two spike complexes. Conditioning photic or acoustic stimuli caused an increase in the size of the initial spike complex and a depression in the secondary spike complex. These changes and the time courses of all the interactions observed were suggestive of presynaptic inhibition.6. The modulatory influences of photic and acoustic stimuli on the cuneate nucleus were present under α‐chloralose or pentobarbitone anaesthesia and the acoustic influence persisted after midcollicular decerebration. When added to other evidence, the above findings suggest that the reticular formation of the brain stem plays an important role in these polysensory interactions.
Membrane properties underlying spontaneous activity of denervated muscle fibres
Authors: Purves D. , Sakmann B. 
Published: December 2014

We have examined the events underlying the initiation of spontaneous action potentials (fibrillation) in fibres of previously denervated rat diaphragm maintained in organ culture for up to 10 days.1. Based on discharge pattern, two classes of spontaneously active fibres were found: rhythmically discharging fibres, and fibres in which action potentials occur at irregular intervals.2. Sites of action potentials initiation were located by exploration along the fibre length with two independent extracellular recording electrodes. The majority of sites of origin in both regular and irregular fibres were at the former end‐plate zone; however, there was no region along the length that could not, at least in some fibres, be a site of origin.3. Intracellular recording at or near sites of origin of action potential discharge showed two types of initiating events. Irregularly discharging fibres were brought to threshold by discrete depolarizations of up to 15 mV in amplitude, while regularly occurring action potentials were associated with oscillations of the membrane potential.4. Discrete depolarizations (called fibrillatory origin potentials or f.o.p.s) at sites of origin in irregularly discharging fibres have the following properties: (a) random occurrence and nearly constant amplitude outside a refractory period during which both amplitude and probability of a second f.o.p. are reduced; (b) associated inward current flow which is localized to about 100 μm or less along the fibre length, and (c) dependence of amplitude and frequency on membrane potential.5. Oscillation of membrane potential found at sites of origin of action potential discharge in regular fibres also occurred locally along the fibre length and was sensitive to changes in membrane potential.6. Both f.o.p.s and oscillations of membrane potential were reversibly abolished by low Na+—Ringer fluid or tetrodotoxin.7. Neither type of initiating event was appreciably affected by concentrations of
D‐tubocurarine which blocked extrajunctional sensitivity to acetylcholine.8. We conclude that spontaneous action potentials under these conditions arise from a localized Na+‐conductance change in the membrane of the active fibre; this conductance change is distinct from the increased Na+‐conductance which follows the interaction of acetylcholine with its receptor. Spontaneous activity in single, denervated muscle fibres is cyclical and self‐inhibiting (Purves & Sakmann, 1974); thus the Na+‐conductance change underlying the initiation of spontaneous action potentials is affected by muscle fibre activity.
The response of laryngeal afferent fibres to mechanical and chemical stimuli
Authors: Boushey H. A. , Richardson P. S. , Widdicombe J. G. , Wise J. C. M. 
Published: December 2014

1. We have recorded afferent activity from ‘single fibres’ dissected from the superior laryngeal nerve of anaesthetized cats.2. Units which responded to gentle mechanical stimulation of the larynx epithelium were chosen for study.3. Receptors with myelinated fibres were grouped according to their spontaneous activity. Group 1 fibres had little or no spontaneous activity: group 2 fibres had constant and continuous spontaneous activity.4. Group 1 fibres had a wide range of adaptation rates. Their conduction velocities lay between 3·0 and 30 m/sec. The receptors were generally stimulated by ammonia and distilled water and often by CS riot control agent, 5 and 10% CO2, 200 ppm SO2, and cigarette smoke. Histamine, phenyl diguanide, graphite dust, 100 ppm SO2 and saline drops did not generally excite the fibres.5. Group 2 fibres were slowly adapting. Their conduction velocities ranged between 8·0 and 26·5 m/sec. Ammonia usually, and distilled water sometimes, excited these fibres while 5 and 10% CO2 mixtures inhibited them. A minority of group 2 fibres were pH sensitive, inhibited by acids and stimulated by alkaline buffers. Cigarette smoke had complex actions, either excitation, inhibition or, at different times, both. Histamine, P.d.g., CS, SO2, saline drops and dust had no action on these fibres.6. Recordings were made from one unmyelinated fibre (conduction velocity 1·9 m/sec) which responded to stroking of the epithelium with a thread and to histamine, P.d.g. and ammonia vapour applied to the epithelium.7. We consider the site, method of excitation and reflex actions of the different receptors described.
Cloacal resorption of salt and water in the Galah (Cacatua roseicapilla)
Authors: Skadhauge Erik 
Published: December 2014

1. The transmural net flow of salt and water in the coprodeum and large intestine of the Galah (Cacatua roseicapilla), an Australian xerophilic parrot, was measured by an in vivo perfusion technique. The main goal of the study was to understand what happens when the hyperosmotic ureteral urine formed in the dehydrated state is regurgitated into the cloaca. Buffered perfusion fluids, hyper‐ and isosmotic to plasma, with varying NaCl and KCl concentrations, were used. [14C]polyethylene glycol served as an unabsorbable water marker.2. The cloacal Na+ and Cl− absorption rates were nearly parallel and at low luminal concentrations roughly proportional to the intraluminal concentrations. At higher concentrations the Na+ absorption rate showed saturation. The maximal Na+ flow was 217 μequiv/kg.hr, the concentration at half maximal flow 181 m‐equiv/l. The Na+ absorption rate was not impaired by a high K+ concentration. K+ was secreted into the intestine, except at high intraluminal K+ concentrations where resorption was observed.4. The apparent osmotic permeability coefficient was 0·85 μl./kg.hr.m‐osmole at an average osmotic difference of 446 m‐osmole between lumen and plasma; it was higher at lower differences. In the (near) absence of an osmotic difference across the cloacal epithelium the solute‐linked water flow was 5·0 μl. H2O/μequiv Na+.5. It is concluded that the hyperosmotic ureteral urine formed in the dehydrated state can pass into the cloaca without a water loss. A Na+ absorption of around 70% of the ureteral output is likely.
Some limitations of the double sucrose gap, and its use in a study of the slow outward current in mammalian ventricular muscle. With an Appendix
Authors: McGuigan John A. S. , Tsien R. W. 
Published: December 2014

1. A double sucrose gap method to clamp small bundles (diameter 0·8–1·2 mm) of sheep or calf ventricular fibres is described.2. Comparison between micro‐electrode recordings from the central gap and the externally recorded potentials showed good agreement between the time course and amplitude of the action potentials. The rapid sodium inward current was not controlled on depolarizing clamp steps. On repolarization, control was obtained within 20 msec. The method is regarded as only suitable for a study of slow currents.3. During clamps of several seconds duration slow changes in outward current can be demonstrated. The potential, where the instantaneous current—voltage relationship crosses the voltage axis, shifted in a positive direction as the clamp duration was increased (clamp amplitude constant), and did not alter much if the clamp amplitude was increased while the duration remained constant. For these reasons it is concluded that K ions accumulate round the cells.4. A comparison between the instantaneous current—voltage relationship in various K solutions and after a depolarizing clamp, showed that an increase in external K could not exactly mimic the changes during a clamp. Because of this, a conductance change, unrelated to accumulation, is also postulated.5. To measure the influence of the slowly increasing outward current during an action potential, slowly increasing inward current (to reduce net outward current) was applied during an action potential and the prolongation of the action potential measured. In the same experiment the increase in outward current during a clamp in a solution with tetrodotoxin and Mn was measured. From these experiments it is concluded that the slow increase in outward current does not contribute much to repolarization in sheep or calf.6. Equations are derived for the voltage distribution and leakage current in the double sucrose gap. From the equations it is possible to calculate an optimal gap width. Too small a gap causes the membrane current to be swamped by the leakage current. Too wide a gap gives unequal potential distribution.
A kinetic approach to the study of absorption of solutes by isolated perfused small intestine
Authors: Fisher R. B. , Gardner M. L. G. 
Published: December 2014

1. A new technique has been developed for making serial measurements of water and solute absorption from the lumen of isolated small intestine.2. The isolated intestine is perfused in a single pass with a segmented flow of slugs of liquid separated by bubbles of oxygen‐carbon dioxide mixture. Simultaneous collections are made of effluent from the lumen and of the fluid which is transported across the mucosa. This latter fluid appears to be a fair sample of the tissue fluid.3. Conditions in the lumen can be changed within less than 5 min. The effects of two or more treatments applied to the same segment of intestine can be determined and the time course of a change in luminal conditions.4. The rate of appearance of solutes on the serosal side depends on the rate of water absorption, and changes exponentially towards a steady state. The rate constant is a function of tissue fluid volume.5. In the steady state the concentration of glucose in the tissue fluid is 71 m
M when the luminal concentration is 28 m
M, and is 45 m
M when the luminal concentration is 8·3 m
M.6. For solutes such as glucose for which reflux from tissue fluid to lumen is small relative to flux from lumen to tissue fluid, the time of attainment of a steady state in secretion is usually 50–60 min.7. For solutes such as sodium for which the reflux is relatively high, the steady state may be reached in 15–20 min.8. The Km for glucose absorption (14–19 m
M) is much lower than is found with unsegmented flow perfusion.9. These findings emphasize problems in interpreting results from other types of intestinal preparation.10. The rate of glucose absorption from the lumen falls only gradually when the luminal sodium concentration is reduced abruptly. In contrast the rate of glucose absorption falls suddenly when the luminal glucose concentration is reduced abruptly. This suggests that glucose absorption is not directly dependent on luminal sodium ions.
Calcium movements in single crustacean muscle fibres
Authors: Ashley C. C. , Ellory J. C. , Hainaut K. 
Published: December 2014

1. Internal microinjection of the Ca‐sensitive photoprotein aequorin or the isotope 45Ca have been used to assess Ca movements in single muscle fibres from the barnacle Balanus nubilus and the crab Maia squinado.2. Progressive isosomotic replacement of external Na by Li, choline, sucrose or Tris was associated with a rapid increase in the level of light emission from internally injected aequorin. This response was dependent upon the presence of external Ca. The light output was maximal for Na concentrations < 50 m
M in the replaced salines, while Na concentrations > 350 m
M produced no apparent increase in the resting light emission.3. If the Ca concentration in the external saline was altered, no effect was observed in Na replaced salines when the Ca concentration was < 1 m
M, but maximal effects were observed at concentrations of Ca of ca. 100 m
M.4. The increased light emission from aequorin in Na‐replaced salines was substantially inhibited by 1 m
M‐La3+ applied externally, but not by
N‐ethyl maleimide (NEM), propanolol or D‐600.5. Following microinjection of 45Ca and 2 hr equilibration, the residual efflux of Ca was shown to be sensitive to the removal of external Ca and Na, the extent of each component being variable.6. The Na‐sensitive Ca efflux was partially inhibited by external La3+ (1 m
M), but not by high concentrations of Mg2+, Ca2+, Mn2+ or Co2+. It was stimulated by NEM and ethacrynic acid, which was considered to be due to an indirect effect upon the sarcoplasmic reticulum.7. It is concluded that Ca movements in these single crustacean muscle fibres involve Na gradients and a Ca: Ca exchange and from the relative insensitivity of Ca movements to various inhibitors, in contrast to the Mg system, it seems that there may be two independent modes for divalent cation transport in this preparation.
Persistent modification of synaptic interactions between sensory and motor nerve cells following discrete lesions in the central nervous system of the leech
Authors: Jansen J. K. S. , Muller K. J. , Nicholls J. G. 
Published: December 2014

We have examined changes that develop in the synaptic interactions of sensory and motor nerve cells following surgical lesions to the central nervous system of the leech. In one type of operation an individual ganglion was isolated from the rest of the nervous system by severing all the incoming and outgoing fibres. During the next few weeks, marked changes appeared in synaptic interactions.1. In chronically isolated ganglia inhibitory potentials were recorded in the motoneurone which raises the skin into ridges (the AE cell) following impulses in sensory neurones that respond to pressure (P) or noxious (N) stimuli. In contrast the same AE cell in ganglia taken from normal animals shows excitatory synaptic potentials when the P or N sensory cells are stimulated.2. Another altered synaptic interaction in ganglia isolated by lesions was that between sensory cells responding to touch and a motoneurone that supplies longitudinal muscles (L cell). Instead of the pure, electrical coupling potential seen normally, a large, additional chemically mediated excitatory potential was also apparent.3. Some of the changes in synaptic interactions were not restricted to synapses within the isolated ganglion, but appeared gradually over the following year in successive ganglia along the length of the ventral nerve cord.4. Indirect evidence suggests that the altered synaptic potentials that became conspicuous after operations are also present but smaller and obscured in normal animals.5. It is concluded that some synapses in the leech nervous system are more readily changed than others by cutting the connectives. Furthermore, these changes influence in a predictable manner the way in which the animal behaves in response to mechanical stimuli.
Changes of intracellular sodium and potassium ion concentrations in isolated rat superior cervical ganglia induced by depolarizing agents
Authors: Brown D. A. , Scholfield C. N. 
Published: December 2014

1. Na and K contents of isolated rat superior cervical ganglia were measured by flame photometry, and intracellular Na and K concentrations ([Na]i and [K]i) calculated using Li and 35SO4 to determine extracellular space (e.c.s.).2. Resting concentrations after 1‐2 hr incubation at 25° C in normal Krebs solution were: [Na]i, 19·8 ± 0·9 m‐mole (kg cell water)−1; [K]i, 192·7 ± 2·8 m‐mole (kg cell water)−1 (mean ±
S.E. of mean of thirty‐five ganglia). Correction for losses during e.c.s. measurement gave 22 m
M [Na]i and 207 m
M [K]i as probable fresh concentrations.3. Carbachol (180 μ
M for 4 min) increased [Na]i by 47·8 ± 2·9 m‐mole (kg cell water)−1 and decreased [K]i by 54·6 ± 4·3 m‐mole (kg cell water)−1. Maximal exchange with carbachol or nicotine (at ∼ 1 m
M for 4 min) amounted to 80–100 m‐mole (kg cell water)−1. On washing with Krebs solution containing 2·5 m
M hexamethonium recovery of ionic concentrations occurred with a rate constant of 0·3–0·4 min−1.4. Restitution of ganglionic Na and K after carbachol was inhibited by washing with K‐free solution, and slowed by ouabain (0·14 m
M), cyanide (2 m
M) or cooling (Q10 2·7 between 17 and 27° C).5. Equilibrium potentials for Na and K (ENa, EK) at rest were calculated to be +49 and −88 mV. At a membrane potential (Em) of −70 m
V, the permeability ratio PNa:PK was calculated at 0·04:1 (assuming PCl:PK < 0·1).
Intracellular chloride activity and the effects of acetylcholine in snail neurones
Authors: Neild T. O. , Thomas R. C. 
Published: December 2014

1. Cl−‐sensitive micro‐electrodes were used to measure intracellular Cl− in snail neurones. The electrodes consisted of a sharpened and chlorided silver wire mounted inside a glass micropipette.2. The electrodes appeared to record changes in internal Cl− accurately but in H cells the chloride equilibrium potential (ECl) as measured by the Cl−‐sensitive electrode was always less negative than EACh.3. In some H cells ACh caused a measurable increase in internal Cl− when the cell was at its resting potential. In voltage‐clamped cells there was a close correlation between the change in internal Cl− and the extra clamp current caused by a brief application of ACh. This confirmed that ACh increases the cell's membrane permeability only to Cl− ions, and that EACh was equal to ECl.4. There was good agreement between the measured change in internal Cl− and that calculated from the cell size and clamp charge only when it was assumed that a constant voltage offset was added to the potential of the Cl−‐sensitive electrode while it was inside the nerve cell.5. Cl−‐sensitive electrodes with AgCl as the sensitive material appear to be unsuitable for intracellular measurement of Cl−, although they might be suitable for following changes in ECl.6. In certain D cells ACh also caused an increase in internal Cl− although it decreased the membrane potential. In the presence of hexamethonium, ACh caused a hyperpolarization and a smaller increase in internal chloride.7. It is concluded that the intracellular Cl− in both H and D cells is about 8·3 m
M, giving an ECl of about −58 mV.