bluuebunny/crossref_metadata_2025 huggingface dataset:
The mechanism of acute renal ischaemia caused by adrenalectomy in the rat.
Authors: Peart W S , Pessina A C
Published: December 2014

1. The acute reduction of renal blood flow following adrenalectomy in the rat, which had previously been shown to be associated with sequestration of blood volume in the splanchnic area, was further investigated. An attempt was made to define the role of the renal sympathetic nerves in causing the blood flow change. 2. The systemic and renal intra‐arterial administration of phenoxybenzamine, isoprenaline and propranolol and denervation of the renal pedicle failed to re‐establish normal renal function. 3. Infusion of P113 (sarcosyl1 alanine8), an angiotensin blocker, failed to improve renal function. 4. In contrast, volume replacement with high‐molecular weight PVP caused a prompt increase of RPF and GFR without altering arterial pressure and central venous pressure. 5. Angiographic studies demonstrated that the calibre of the aorta of adrenalectomized rats was significantly smaller than that of the sham operated and increased after the administration of this plasma volume expander. 6. It was concluded that after adrenalectomy the major arteries readjusted their calibre to the reduced volume of blood in the arterial tree with maintenance of a constant pressure/volume relationship. Their contracted state in the case of the kidney then led to flow reduction.
Actions of gamma‐aminobutyric acid on sympathetic ganglion cells.
Authors: Adams P R , Brown D A
Published: December 2014

1. Responses of single ganglion cells in the isolated rat superior cervical ganglion to gamma‐aminobutyric acid (GABA) applied via the bathing medium were recorded using intracellular micro‐electrodes. 2. GABA produced a large fall in cell input resistance, frequently to immeasurable levels. In thirteen cells showing a modest response to 100 muM GABA, input resistance fell from 50–5 +/−9–5 to 15.9 +/− 3‐2 Momega (means +/− S.E. of mean). After correction for resistance leaks introduced by the impaling electrode, the resting membrane resistance Rm and the resistance of the GABA‐shunt Rg in these cells were calculated to be 79–3 +/− 16–6 and 35–0 +/− 9–5 Momega respectively. 3. Cells with recorded resting membrane potentials greater than −42 mV were depolarized by GABA; at resting potential less than −42 mV they were hyperpolarized...
Binomial analysis of quantal transmitter release at glycerol treated frog neuromuscular junctions.
Authors: Miyamoto M D
Published: December 2014

1. Transmitter release was analysed at frog neuromuscular junctions pre‐treated with 400 mM glycerol Ringer. In the absence of added drugs, end‐plate potentials (e.p.p.s) and miniature e.p.p.s (m.e.p.p.s) could be recorded at selected junctions. 2. E.p.p.s were unusually large and calculations of quantal content indicated a high level of release. Also recorded were anomalous action potentials resembling e.p.p.s but these could be distinguished using a summation test. 3. Plots of coefficient of variation of e.p.p.s (0–5 Hz stimulation) versus direct quantal content (M1) showed a marked deviation from Poisson expectations with high M1. Analysis of these results with amplitude‐frequency histograms showed a progressively better fit to binomial predictions with increasing M1. 4. The use of binomial statistics allowed direct calculations of the mean probability of release (p) and the readily available store (n). Increasing Ca/Mg caused increases in both n and p. 5. Plots of M1 vs. Ca/Mg showed a power relationship of 3.58. Maximum m.e.p.p. amplitude occurred at control Ca/Mg. Both results were consistent with studies in muscles not treated with glycerol and indicated that glycerol treatment caused no major alterations pre‐ or post‐junctionally. 6. Estimates of quantum size using Poisson assumptions showed an over‐all increase when stimulus frequency was raised, indicating a shift from binomial to a Poisson distribution. 7. The combined findings demonstrate that the glycerol treated preparation can be used to examine the release process during high output. Such release conforms to binomial statistics and allows direct determinations of the parameters n and p.
Effect of intracellular injection of calcium and strontium on cell communication in heart.
Authors: De Mello W C
Published: December 2014

1. The influence of Ca and Sr on the electrical coupling of canine Purkinje cells was investigated by injecting the ions electrophoretically into the cytoplasm. 2. It was found that the intracellular injection produced electrical uncoupling which was spontaneously reversed. 3. No change in resting potential of the cell adjacent to the injection site was found except in those fibres not completely healed. 4. The input resistance of the injected cell increased concomitantly with the establishment of the electrical uncoupling. 5. Caffeine (6mM), added to the extracellular fluid, reduced the rate of spontaneous recoupling. Reduction of temperature of the Tyrode solution had the same effect. 6. The abolition of cell communication produced by Ca injection seems to indicate that the ion plays an important role in the control of junctional conductance in heart fibres.
Tonic release of transmitter at the neuromuscular junction of the crab.
Authors: Parnas I , Rahamimoff R , Sarney
Published: December 2014

1. Synaptic transmission was studied at the neuromuscular junction of the crab Ocypoda cursor, using conventional electrophysiological technique. 2. It was found that fibres of the extensor muscle and those composing the internal layer of the closer muscle have only post‐synaptic inhibition (S fibres) while the fibres at the external layer of the closer muscle have in addition presynaptic inhibition (R fibres). 3. In S fibres, addition of GABA reduces input membrane resistance (Rm) and e.p.s.p. amplitude approximately to the same degree. The effect shows desensitization. In R type fibres, GABA reduces the e.p.s.p. much more than expected from changes in Rm. The post‐synaptic effect of GABA on Rm shows desensitization, while the presynaptic effect does not show desensitization. 4. In about 50 percent of the cases, after desensitization occurred, Rm increased by about 10–30 percent above the control. Similar increase in Rm occurred after application of picrotoxin. These results suggest that initially the membrane resistance was lower due to tonic release of inhibitory transmitter. 5. The Q10 of Rm was found to vary between 2 and 3. In Ca2+ free media, Cl− free media, or in picrotoxin the Q10 is about 1–3. 6. In R fibres, addition of picrotoxin increased the amplitude of the e.p.s.p. by 30–60 percent above the expected increase due to changes in Rm. 7. In S fibres the mean slope of log e.p.s.p. vs. log [Ca2+] was found to be 1–63, while in R fibres the slope was 0–93. These results suggest the presence of tonic release of the inhibitory transmitter which acts both post‐synaptically and presynaptically.
Stimulation by aldosterone of the sodium efflux in barnacle muscle fibres: effects of RNA inhibitors and spironolactone.
Authors: Bittar E E , Tallitsch R B
Published: December 2014

1. Single muscle fibres from the barnacle Balanus nubilus have been studied to provide information about the mode of action of aldosterone on Na transport in a symmetric cell. 2. Neither internal nor external application of aldosterone modified the course of the Na efflux. However, fibres pre‐exposed overnight to a dose of aldosterone showed a biphasic response to external aldosterone. The first phase was prompt in onset and consisted of a falling rate constant for Na efflux becoming a constant. This has been interpreted as indicating that aldosterone acts by releasing sequestered or bound Na. The second phase was delayed in onset with the average latent period being 68 min. It consisted of a step‐up in the rate of Na efflux, followed by a transitory rise in the efflux rate constant. This second phase was dose‐dependent, the minimum concentration being 10(−9) M. 3. Internal application of aldosterone in a concentration as low as 10(−10) M promptly stopped the rate constant for Na efflux from further falling but failed to cause delayed stimulation. 4. The response of the Na efflux into Li‐ASW following external application of aldosterone was bi‐phasic. The magnitude of the delayed stimulation was comparable to that found in controls. 5. No correlation between latent period or size of the internal Na bound fraction, and the magnitude of the delayed stimulation could be established. 6. Internal application of actinomycin‐D, alpha‐amanitin or cordycepin shortly before application of external aldosterone caused complete abolition of the delayed stimulation. 7. Overnight pre‐exposure of the barnacle to actinomycin‐D caused complete abolition of the falling rate constant for Na efflux, as well as the delayed stimulation caused by external aldosterone. 8. Internal application of spironolactone SC‐14266 shortly before external application of aldosterone caused complete abolition of the biphasic response to the steroid. 9. It is concluded that (i) barnacle fibres can be made sensitive to aldosterone, (ii) the biphasic effects on the Na efflux depend on prior induction of RNA, (iii) the first effect caused by internal or external aldosterone involves mobilization of sequestered Na, (iv) the results obtained with spironolactone are in keeping with the current view that aldosterone interacts with a receptor system before causing de‐repression. 10. The implications of the finding that aldosterone releases sequestered Na are briefly touched upon.
The independence of channels in human vision selective for direction of movement.
Authors: Levinson E , Sekuler R
Published: December 2014

1. Human visual selectivity for direction of movement was determined using a subthreshold summation technique. 2. The threshold contrast for detecting a drifting sinusoidal grating was found to be independent of the contrast of an added subthreshold grating which moved in the opposite direction. 3. The detection threshold for a counterphase flickering grating is twice that for a moving grating, suggesting that the visual system analyses a counterphase grating as the sum of two half‐contrast gratings which move in opposite directions. 4. Threshold for a counterphase grating may be linearly reduced by the addition of subthreshold background gratings drifting in either direction. Additivity between counterphase grating and moving background is complete. 5. After adaptation to a drifting grating, the behaviour of counterphase detection threshold as a function of the contrast of a moving subthreshold background depends upon the direction of background movement. When the background moves in a direction opposite that of the adaptation stimulus, complete linear additivity results. When the background moves in the same direction as the adapting grating, counterphase threshold is constant for low background contrasts, but drops linearly for higher background contrasts. 6. The results support the hypothesis that directionally selective channels in human vision are independent contrast detectors. Counterphase gratings are detected by one or the other of these direction‐specific mechanisms, whichever is momentarily the more sensitive.
Regional differences in the effect of bile salts on absorption by rat small intestine in vivo.
Authors: Saunders D R
Published: December 2014

1. The hypothesis that endogenous bile salts influence water absorption in rat small intestine was tested in vivo. 2. Net water transport was measured under steady‐state conditions during single‐pass infusion of segments from three regions of the small intestine. Each segment served as its own control. 3. Delipidated rat bile, and solutions of the principal bile salts of the rat, taurocholate and glycocholate, reduced absorption in the proximal jejunum but not in the distal ileum. 4. 1‐Palmitoyl,2‐oleoyl lecithin, an important biliary lecithin, counteracted the inhibitory effect of taurocholate and of glycocholate on absorption. The presence of biliary lecithins probably explains why whole rat bile did not depress water absorption in the proximal jejunum. 5. Net water transport in the distal jejunum was inversely related to log10 (taurocholate concentration). 6. Endogenous bile salts may help to maintain the fluidity of the contents of the mid‐small intestine in the rat after biliary and dietary lecithins have been absorbed.
Effects of changes in the composition of the serosal solution on the electrical properties of the toad urinary bladder epithelium.
Authors: Finn A L , Reuss L
Published: December 2014

1. The potential profile and the cellular and paracellular transepithelial resistances of the toad urinary bladder were measured, by means of micro‐electrode techniques, as functions of the osmolality of the serosal solution. 2. Reductions in serosal osmolality (that increase the rate of active sodium transport) produced proportional decreases in the electrical resistances of the apical and basal‐lateral cell membranes, while the changes in resistance of the paracellular pathway were more complex. The apical membrane potential increased. 3. Increases in serosal osmolality (that decrease sodium transport) produced increases in the electrical resistances of both cell membranes, and moderate reduction in the paracellular resistance. The polarity of the apical membrane potential reversed. 4. These results indicate that reductions in serosal solution osmolality stimulate sodium transport by increasing both the sodium permeability of the luminal cell membrane (thus increasing sodium entry), and the electromotive force generated at the serosal border of the cell, thus enhancing the rate of sodium pumping. Conversely, increases in osmolality reduced sodium transport by reducing both the sodium permeability of the luminal membrane and the serosal membrane electromotive force.
Re‐innervation of rat skeleton muscle in the presence of alpha‐bungarotoxin.
Authors: Jansen J K , Van Essen D C
Published: December 2014

1. The possible role of acetylcholine (ACh) receptors in controlling neuromuscular synapse formation was studied by blocking the receptors with alpha‐bungarotoxin during re‐innervationf the rat diaphragm. Anaesthetized and artificially respirated rats were perfused with toxin throughout the 3‐day period when most re‐innervation was shown to take place (from day 4 to day 6 after a nerve crush). 2. The toxin treatment blocked about 99.9% of both junctional and extrajunctional ACh receptors, thereby eliminating virtually all end‐plate potentials. However, a low level of ACh sensitivity returned to the muscle after several hours of washing, and small end‐plate potentials were then recorded from the majority of fibres on the side that previously had been denervated. The degree of re‐innervation was nearly as great as that seen in control denervated muscles that had not been treated with toxin. 3. The presence of bungarotoxin during re‐innervation did not significantly affect either the appearance of newly formed synapses in the light microscope or the amount of transmitter they released during nerve stimulation. 4. Double innervation, which was not seen in normal muscles, was found in about 10–15% of re‐innervated fibres in both the untreated and toxin‐treated preparations. This suggests that some of the synapses formed during re‐innervation may have been made over what previously had been extrajunctional membrane. 5. It is therefore unlikely that the ACh receptor, or at least that part of the receptor to which bungarotoxin binds, plays a direct role in controlling the process of synapse formation in mammalian skeletal muscle...
Sodium/sodium exchange in the smooth muscle of the guinea‐pig taenia coli.
Authors: Brading A F
Published: December 2014

External Na has been shown to initiate a loss of 24 Na from high‐Na smooth muscle of the guinea‐pig taenia coli. This is an ouabain‐insensitive effect, and there appears to be a 1:1 exchange of Na ions, suggesting a classical Na/Na exchange mechanism. 2. The Na/Na exchange has many properties in common with a similar exchange studied in high‐Na beef erythrocytes by Motais (1973), and Motais & Sola (1973). It is very temperature‐sensitive, it is partially inhibited by the sulphydryl reagents studied and it has a fairly low external affinity for Na. 3. The affinity of the external site for alkali metal cations is Na greater than Li greater than K greater than Rb greater than Cs. 4. It has proved impossible to estimate the affinity of the intracellular sites for Na. The curve relating intracellular Na content with the stimulated efflux reaches a maximum and then declines slightly. 5. Another unexpected finding was that after the rate of loss of Na has been reduced in a Na‐free medium, reintroducing Na causes an overshoot in the rate, it increases to a value beyond the original one, and then slowly declines to it. 6. Unlike the classical Na/Na mechanism, the process is reduced, but not abolished by metabolic inhibition that depletes the tissue of ATP. 7. The results are interpreted to suggest that the Na/Na exchange is occurring from a cellular compartment of limited volume, which is itself exchanging with the main cell compartment. It is suggested that this small compartment is the sarcoplasmic reticulum, and the effect of metabolic inhibition is to interfere in some way with the relationship between this compartment and the cell membrane.
Horizontal cell responses in the retina of the larval tiger salamander.
Authors: Lasansky A , Vallerga S
Published: December 2014

The responses to light of horizontal cells were recorded intracellularly in the retina of the larval tiger salamander. 2. All the units studied had a large summation area and were hyperpolarized by circles of light of any wave‐length centred on the recording electrode, but two types could be distinguished according to the properties of their receptive fields. Type A units were hyperpolarized following illumination of any portion of their receptive field, while type B units were not hyperpolarized by illumination of their surround unless the centre was simultaneously illuminated, stimulation of the surround alone resulting in either a small depolarization or virtually no response. 3. Procion yellow injections showed that type A responses are recorded from thick and long processes not directly continuous with an identifiable cell body, while type B responses originate from the cell body of cells that send very fine and tortuous processes towards the receptors. The histological observations also suggested that the type A units represent expansions or swellings of one or more of the fine processes originating from the type B units. Therefore, it seems possible that both types of units are just different parts of a single kind of horizontal cell, and that a majority of the dye injections failed to stain them simultaneously because of the small diameter of the connecting process. 4. The large summation area of type A units can be explained, just as for horizontal cells in other retinae, by supposing that they are electrically coupled to other units of the same type. The receptive field properties of type B units, however, can only be partly explained by electrical coupling, and then only if the existence of voltage‐dependent junctions is postulated. Instead, the reversal of the polarity of responses to an annulus of light during steady illumination of the centre, plus the available electron microscopic evidence, suggest that the effect of the surround on the type B units is due to a chemical synaptic impingement from the type A units.
Effect of ascorbic acid on histamine metabolism in scorbutic guinea‐pigs.
Authors: Chatterjee I B , Gupta S D , Majumder A K , Nandi B K , Subramanian N
Published: December 2014

1. In guinea‐pigs fed an ascorbic‐acid‐free diet, as the ascorbic acid levels decreased the histamine levels in blood and urine rose steadily to maxima in about 10‐12 days. The elevated histamine levels persisted in the blood and urine of scorbutic guinea‐pigs and the histamine levels in lung, gastric mucosa and spleen also increased. The increased histamine content of the urine, blood and other tissues in the ascorbic‐acid‐depleted condition could be brought back to normal levels by administration of a single dose of ascorbic acid 5 mg/100 g body wt. guinea‐pig. 3. The drop in the elevated histamine level was not due to an indirect effect of ascorbic acid on histamine forming capacity, histaminase activity or histamine release.
The number of transmitter molecules in a quantum: an estimate from iontophoretic application of acetylcholine at the neuromuscular synapse.
Authors: Kuffler S W , Yoshikami D
Published: December 2014

1. The sensitivity of the subsynaptic membrane of twitch muscles of the frog and snake to iontophoretically applied acetylcholine (ACh) was determined. Optimal placement of ACh micropipettes on to the postsynaptic membrane resulted in potentials that were similar, though not identical, to the miniature excitatory post‐synaptic potentials (min e.p.s.p.s). A sensitive bio‐assay was developed to measure the output of ACh from micropipettes; this allowed an estimate to be made of the upper limit of the number of ACh molecules in a quantum of transmitter that is released from the nerve to produce a min e.p.s.p. 2. The assay to calibrate the output of ACh from micropipettes used the end‐plate of the snake muscle as an ACh concentration detector. The end‐plate was situated within a few mum of an oil‐water interface, and a 0‐6 nl. droplet of Ringer solution containing a known concentration of ACh (1 muM or less) was formed in the oil phase. The droplet was brought to the interface and, upon touching it, discharged its contents into the Ringer phase immediately above the end‐plate. This resulted in a membrane depolarization that was recorded with an intracellular microelectrode. By applying droplets containing various known ACh concentrations a standard curve was constructed. To measure the ACh output of micropipettes a 0‐6 nl. droplet of Ringer solution was suspended in the oil. The ACh pipette tip was inserted into the droplet and several thousand pulses of ACh were then delivered. The ACh content of the test droplet was measured by comparing its effectiveness in depolarizing the end‐plate with the standard curve. In this manner the number of ACh molecules released in a single pulse was determined as a function of charge passed through the pipette. The output of ACh was linear and an average of 30,000 molecules of ACh were released per pC. 3. The sensitivity of the subsynaptic membrane to iontophoretically applied ACh, using the linear slopes of dose‐response curves, in preparations from frog and snake treated with anticholinesterases was usually about 5 mV/pC. It follows that 6000 molecules of ACh are sufficient to produce a depolarization of 1 mV in the subsynaptic membrane. 4. The mean min e.p.s.p.s of muscle fibres treated with anticholinesterase range from 1 to 3 mV. Since the ACh released from an iontophoretic pipette is less effective than the same amount released from the nerve, it is concluded that a quantum of transmitter consists of less than 10,000 molecules of ACh. 5. It is calculated that for each molecule of ACh released in a quantum there results a minimum net flow of 3000 univalent ions across the synaptic membrane.
The effect of zinc ions on the gating of the delayed potassium conductance of frog sartorius muscle.
Authors: Stanfield P R
Published: December 2014

1. A voltage‐clamp method was used to examine the effects of zinc ions on the delayed potassium currents and also the slowly activating potassium currents that are turned on by depolarizing the membrane of frog sartorius muscle fibres. 2. In a control solution, the delayed potassium conductance had a maximum value of 17‐8 +/‐ 2‐5 mmho.cm‐2. The reversal potential for the currents was ‐76‐9 +/‐ 2‐5 mV. The membrane potential where ninfinity had the value 0‐5 was ‐49 mV. 3. The major effect of zinc ions was to slow the delayed potassium currents. The value of taun was increased approximately tenfold in 0‐1 mM zinc. Zinc does not alter the effective valency of the gating particles of the potassium channel, but the conductance was shifted to more positive membrane potentials: in 0‐1 mM zinc, the membrane potential where ninfinity had the value 0‐5 was ‐32 mV. 4. Zinc ions, at a concentration of 0‐1 mM, also reduced the maximum potassium conductance by about 60% to 7‐3 +/‐ 0‐8 mmho, cm‐2; they did not alter the reversal potential of the currents, which had a value in 0‐1 mM zinc of ‐74‐6 +/‐ 1‐5 mV. 5. Zinc ions had little or no effect on the rate of inactivation of the potassium currents. 6. Zinc ions had little effect on the conductance attributable to the slowly activating potassium system. In 0‐01 mM zinc this conductance had a value at 0 to +10 mV of 1‐25 +/‐ 0‐29 mmho.cm‐2. Zinc did not alter the reversal potential of the slow potassium currents from the value of ‐85 +/‐ 1‐6 mV in the absence of zinc and had no effect on the time course of the turn‐off of these currents at ‐60 mV. 7. The delayed potassium currents obtained in 0‐002 and 0‐01 mM zinc could not be fitted exactly with a simple fourth order equation, but were well fitted by a model proposing that zinc ions slow the opening and closing of the gating mechanism to one tenth the normal rate when they bind to the gating molecule. If the binding sites are not saturated, those gating molecules that do not bind zinc are assumed to be quite unaltered in their properties, though the potential dependence of their rate constants alphan and betan was assumed to be shifted to more positive levels. In one fibre in 0‐01 mM zinc, the model fitted the currents best if 50% of the gating molecules bound zinc.
The effect of saline and hyperoncotic dextran infusion on canine ileal salt and water absorption and regional blood flow.
Authors: Mailman D , Jordan K
Published: December 2014

1. The unidirectional Na and H2O fluxes, vascular pressures and total and absorptive site blood flows in the canine ileum were determined before and during I.V. saline infusion and subsequent I.V. infusion of hyperoncotic dextran. The intestinal perfusion solutions were isotonic saline or isotonic saline and mannitol, but the effects of I.V. saline or I.V. hyperoncotic dextran infusion were generally the same for both luminal solutions. 2. Continuous I.V. infusion of saline caused a continuous increase in the unidirectional flux of Na and H2O into the ileal lumen, an increase in total blood flow, and an increase in venous pressure. 3. The net absorption of Na and H2O was decreased by I.V. saline infusion. 4. The unidirectional fluxes of Na and H2O out of the lumen, arterial pressure, and absorptive site blood flow were not affected by I.V. saline infusion. 5. I.V. hyperoncotic dextran infusion reversed most of the effects of saline infusion. 6. The unidirectional fluxes of Na and H2O into the lumen were significantly correlated with Starling forces during I.V. saline infusion. 7. It was concluded that intestinal transport of salt and water was subject to regulation by physical forces at the capillary level.
Readjustment of retinotectal projection following reimplantation of a rotated or inverted tectal tissue in adult goldfish.
Authors: Yoon M G
Published: December 2014

1. The pattern of visual projection from the retina on to the optic tectum following reimplantation of a piece of the tectal tissue was studied with neurophysiological mapping methods in adult goldfish. 2. When a rectangular piece of the tectum was dissected, lifted free, and then reimplanted to the same tectum after rotation by 180 degrees around the dorsoventral axis, the re‐established visual projection later showed a complete reversal of retinotopic order within the reimplanted area with reference to the normal projection on to the intact surrounding area of the same tectum. The localized reversal was observed as early as 65 days, and also as late as 721 days after the 180 degree rotated reimplantation. 3. If a square piece of the tectal tissue was reimplanted after rotation by 90 degrees anticlockwise around the dorsoventral axis, the restored visual projection later showed a corresponding localized 90 degrees rotation within the reimplanted ares. 4. When the entire laminar structure of a dissected tectal tissue was inverted, and the reimplanted upside‐down along the same rostrocaudal axis of the tectum, the restored visual projection on to the inverted tectal reimplant was found to be organized in a reverse retinotopic order along only the mediolateral axis within the reimplanted area. The restored visual projection retained a correct retinotopic order along the rostrocaudal axis. The same trends were also observed after regeneration of the optic fibres following section of the contralateral optic nerve. 5. If the inverted tectal tissue was reimplanted along the same mediolateral axis of the tectum, the re‐established visual projection showed a localized reversal of retinotopic order along only the rostrocaudal axis within the reimplanted area. Sectioning the contralateral optic nerve made no difference to the result. 6. These results suggest that a piece of adult tectal tissue retains its original topographic polarity regardless of the orientation of reimplantation after either a rotation or an inversion. Furthermore the retention is not a short‐lived transitory phenomenon. It persisted as long as the reimplanted tissue survived. 7. Histological examination of the operated tecta revealed that the reimplanted tectal tissues underwent a severe derangement in their laminar structures. It was impossible to identify the main target zone of retinotectal projection (the stratum fibrosum et griseum superficiale) or the central cellular layer (the stratum griseum centrale) in the reimplants. The prominent feature of the deranged tectal tissue was irregular vortices of tangled fibre bundles. Sparse tectal neurones of bipolar and granular types were irregularly scattered in the deranged structure of the reimplant. 8. Thus, the retention of original topographic polarity did not require an integrity of the cytoarchitectonic structure of the reimplanted tectal tissue.
Mechanism of action of pentagastrin and acetylcholine on the longitudinal muscle of the canine antrum.
Authors: Szurszewski J H
Published: December 2014

1. Electrical and mechanical activities of the longtitudinal muscle of the dog antrum were recorded with the double sucrose‐gap technique. 2. The muscle exhibited spontaneous action potentials which consisted of a spike‐like potential which, after a brief and partial repolarization, was followed by a negative‐going, plateau‐type potential. In 97% of the preparations, no tension changes were produced by spontaneous action potentials. 3. Tetrodotoxin, atropine, alpha‐ and beta‐adrenoceptor antagonists, and H1 and H2 receptor blocking agents had no effect on the action potential. It was concluded that the action potential was myogenic in origin. 4. The mean frequency of the action potential at 37+/‐ 0.5 degrees C was 1.0/min+/‐0.06 (s.e. of mean, n=92) and the mean duration 7.1+/‐0.2 sec (s.e. of mean, n=11). 5. Steady depolarizing current increased whereas hyperpolarizing current decreased the frequency of the action potential. 6. Length‐tension relations were studied. In twelve strips, the average resting, passive, tension at LO was 570 mg. The active force of isometric contraction produced by acetylcholine increased with strip length up to a maximum, then decreased wtih further increased in length. There were no mechanical responses to pentagastrin. 7. Pentagastrin had two sites of action. On smooth muscle, it increased the frequency of the action potential in a dose dependent fashion. Threshold concentraions ranged from 2X10‐14 to 10‐11M. The ED50 was 2X10‐10M. The maximum response, 5.4/min, was reached at 10‐8M. Pentagastrin also released acetylcholine from intramural cholinergic nerves. 8. Pentagastrin reduced the amplitude and duration of the action potential.
Secretion of electrolytes by the pancreas of the anaestetized rat.
Authors: Sewell W A , Young J A
Published: December 2014

1. HCO‐3, Na+ and K+ concentrations were measured in bile‐free pancreatic juice collected from fasted and fed anaesthetized rats. 2. Resting flow rates averaged 0.62 mul. g‐1 .min‐1 (fasted) and 2.8 mul. g‐1. min‐1 (fed) and the mean HCO‐3 concentrations, respectively, were 25.8 and 33.3 mM. 3. In fasted rats, instillation of HCl into the duodenum caused flow rate to increase threefold and HCO‐3 concentrations to double (66 mM). Intravenous infusion of pure natural (GIH) secretin caused a fivefold increase in flow rate; HCO‐3 concentrations, again, doubled (67.5 mM). Infusion of synthetic secretin produced effects essentially the same as those produced by GIH secretin. 4. Infusion of Boots secretin caused a thirteenfold increase in flow rate (8.32 mul.g‐1. min‐1) but HCO‐3 concentrations rose only slightly (43.3 mM). However, following cessation of infusion, when flow rate approximated the maximum obtained with pure secretin, the HCO‐3 concentration was much higher (57.2 mM at 3.19 uml.g‐1.min‐1). In fed animals the responses were similar but maximum flow rates were greater (12 mul. g‐1. min‐1). 5. Infusion of caerulein produced a secretory rate slightly less than with Boots secretin (5.06 mul. g‐1.min‐1) and HCO‐3 concentrations were plasmalike (30.2 mM); infusion of the synthetic octapeptide of cholecystokinin (OP‐CCK) gave similar flow rates and HCO‐3 concentrations. 6. Infusion of a mixture of caerulein and GIH secretin mimicked closely the effect of Boots secretin. At maximum flow rates (7.6 mul. g‐1. min‐1) the HCO‐3 concentration was 43.7 mM and at lower flow rates (3.90 mul.g‐1. min‐1) it rose to 54.2mM. 7. It is concluded that the response of the rat pancreas to secretin is qualitatively similar to that of all other vertebrates so far studied, but, relative to other animals, the response is sluggish. In contrast, the rat pancreas responds well to cholecystokinin (CCK) stimulation, yielding a juice with plasma‐like HCO‐3 concentration. Boots secretin, which is heavily contaminated with CCK, causes a mixed response resembling that of CCK at high secretory rates and that of pure secretin at lower rates. 8. An unexplained feature of rat pancreatic juice was that K+ concentrations, although plasma‐like in unstimulated samples, rose to about 8mM when flow rate increases as a result of secretin, but not CCK, stimulation. In all other animals so far studied, the K+ concentration has been found to be independent of flow rate.
Some electrical and mechanical effects of strontium on toad ventricular muscle: comparison to calcium.
Authors: Bass B G , Ciulla E M , Klop P , Van Baal S
Published: December 2014

1. The mechanical and electrophysiological effects of Sr were evaluated and compared to those of Ca in isolated, electrically driven toad ventricular muscle strips. The effects of Ca and Sr were compared at concentrations from control (2 mM) to 10 mM either by substitution of Sr for Ca at equimolar concentration, or by maintenance of a constant total Ca plus Sr concentration within which individual Ca and Sr concentrations were varied. 2. Changes in the degree of contractile activation were evaluated in terms of changes in maximal dT/dt of isometric contractions, maximal dL/dt of very lightly loaded isotonic contractions, and the shape of after‐loaded force‐velocity curves, with specific attention directed to the shape of the curves as they approached Vmax on the velocity axis. Effects on the cell membrane were evaluated in terms of changes in the transmembrane action potential (recorded with glass micro‐electrodes) and in the mechanical parameters directly related to its duration in amphibian ventricle, viz. the duration of isometric tension and of isotonic shortening. Isometric tension and action potentials were recorded simultaneously. 3. Ca and Sr, at concentrations above control, had similar but not identical effects on dT/dt and dL/dt. Both ions alone in equimolar concentrations, or together at constant total Ca plus Sr concentration, increased dT/dt and dL/dt and shifted force‐velocity curves upward. At constant total Ca plus Sr concentration, force‐velocity curves were virtually superimposable as they approached the velocity intercept. 4. The duration of the action potential was markedly prolonged by Sr and shortened by Ca in concentrations above control. Unlike dT/dt and dL/dt, the total duration of isometric tension and isotonic shortening depended upon the specific Ca and Sr concentrations within a constant total concentration, and were progressively prolonged as the Sr concentration was increased. 5. The similar effects of Ca and Sr on dT/dt, dL/dt, and on the force‐velocity relationship at light loads depended upon the presence of Ca ions. In Sr alone, dT/dt and dL/dt were faster than in an equimolar concentration of Ca, and time to maximal dT/dt and dL/dt was prolonged. The force‐velocity curve in Sr alone was consistently shifted upward beyond the other curves in which Ca was present. These differences between the two ions are attributed in part to the rapid and early repolarization of the action potential in elevated Ca and the resultant abbreviation of the build up in active state and slower dT/dt and dL/dt. 6. The results suggest that Ca and Sr act in a similar although not identical way in activating contraction but are competitive at the cell membrane.
The stages of osmotic haemolysis.
Authors: Jay A W , Rowlands S
Published: December 2014

The haemolysis of individual human erythrocytes has been observed using an inverted microscope and cine‐camera. 2. With each permeant (glycerol, propylene glycol, ethylene glycol, urea and water) haemolysis is a multistage process. The stages are swelling, popping, reduction in volume possibly accompanied by ion leakage and, finally, haemoglobin leakage. 3. The classical haemolysis time (Th) is made up of a swelling time (Tsw) and a stress time (Tst). Tst is not negligible and with the faster permeants it may occupy more than 75% of the haemolysis time. 4. The stress time can also be divided into two parts: a K+ leak time (TK) during which the cell shrinks and a time (THb) during which haemoglobin is leaving the cell. THb occupies a substantial part of Th, from 25 to 65%, and is relatively longer in fast haemolysis. 5. There is a wide spread in the permeability coefficient to glycerol in a population of erythrocytes. The distribution is compatible with a Gaussian distribution. The mean permeability is 1‐79 X 10(‐6) cm/sec and the S.D. is +/0 0‐45 X 10(‐6) cm/sec. 6. The correlation between haemolysis time and swelling time for individual erythrocytes is poor, especially for fast haemolysis. Consequently, a measure of the distribution of haemolysis time does not give a related distribution of the swelling time or of the calculated permeability for individual erythrocytes.
Load compensation in human masseter muscles.
Authors: Lamarre Y , Lund J P
Published: December 2014

The reaction of masseter and digastric muscles to changes in the load applied during a movement was studied in human volunteers. 2. Rapid stretch of the jaw‐closing muscles evoked a monosynaptic jaw‐jerk reflex response in the masseteric electromyogram (e.m.g.) after a delay of 6‐8 msec. 3. The averaged integrated e.m.g. activity of the masseter was increased 5‐10 msec after the rapid application of a load during voluntary closure of the jaw. It was not necessary to stretch the muscle to obtain this apparently monosynaptic response. 4. A compensatory increase in the velocity of movement followed 6‐10 msec after the e.m.g. peak. 5. Unloading the masseter muscle during contraction was followed by a fall in e.m.g. activity, beginning after a latency of 6‐5‐‐1 msec, with later phases of depression beginning 27‐‐36 and 60‐‐70 msec after unloading. 6. The spindle‐poor digastric muscles were not monosynaptically activated during loading, but responded with a latency of 24‐‐34 msec. 7. It is concluded that monosynaptic e.m.g. changes are a prominent feature of the load compensation system in human jaw‐closing muscles but not in jaw‐opening muscles.
Calcium content and exchange in frog skeletal muscle.
Authors: Kirby A C , Lindley B D , Picken J R
Published: December 2014

Calcium content and exchange in frog ELD IV muscle were examined employing the efflux technique. 2. Muscle calcium was found to exchange with four time constants, 21‐5 sec 2‐7, 32 and 1244 min. 3. All calcium was found to be exchangeable with more than half the total amount residing in an extracellular compartment. 4. Results obtained from ELD IV muscles and single fibres were identical. 5. Muscle calcium content was found to remain constant up to 20 hr in vitro. 6. Extra exchange of calcium occurs upon contraction. This extra exchange appears to occur in the most slowly exchanging component. 7. The data are discussed in relation to morphological and autoradiographic findings and a model of calcium exchange in skeletal muscle is presented.
Electromechanical studies on the inotropic effects of acetylstrophanthidin in ventricular muscle.
Authors: Greenspan A M , Morad M
Published: December 2014

Three phases in the inotropic response of acetyl strophanthidin (AcS) on the electromechnical activity of the frog ventricular myocardium were identified and studied using a single sucrose voltage‐clamp technique and other conventional electrophysiological methods. 2. the positive inotropic response of the drug was accompanied by a shift in tension‐voltage relation, so that more tension developed with every depolarization step above the mechanical threshold (‐50mV). Only at higher drug concentrations or with long exposure times did the mechanical threshold shift to more negative membrane potentials (‐60 to‐70 mV). 3. In tetrodotoxin‐treated muscles AcS produced marked potentiation of twitch tension and an appropriate shift in the tension‐voltage relation. 4. the positive inotropic response of the drug was not related to the magnitude of the direction of the fast or slow Na current. 5. in tetrodotoxin‐treated ventricular strips the direction or the magnitude of the secondary inward current (ICa or INa) were not related to the inotropic effect of AcS. 6. AcS shortens the action potential markedly during the later stages of its positive inotropic response. When Ca2+ is omitted from the bathing solution AcS not only fails to shorten the action potential, but often prolongs it. 7. The shortening of the action potential in the presence of AcS is accompanied by an increase in the "instantaneous" membrane conductance both at rest and during the time course of the plateau. 8. The decline in the positive inotropic response of the drug was accompanied by the shortening of the action potential. Electrical or chemical prolongation of the action potential restored the full positive inotropic response if the membrane had not depolarized. 9. Membrane depolarization and the development of diastolic tension always occurred at later stages of drug action. Elevation of [Mg+2]degrees to 5 or 10 mM prevented or suppressed the membrane depolarization and the diastolic tension. 10. KCl‐induced contractures were potentiated throughout the duration of drug exposure. The tonic component of the contracture tension was markedly elevated especially at later stages of drug action. 11. The experimental evidence suggests that no unitary mechanism could account for multiple actions of acetyl strophanthidin. However, the contributions of the Na pump, the Ca+2 sequestering system, and the K‐efflux system to the various stages of drug action are discussed.
Effect of bradykinin on transepithelial transfer of sodium and water in vitro.
Authors: Crocker A D , Willavoys S P
Published: December 2014

Mucosal sodium and water transfer were measured in everted sacs of rat jejunum. 2. Bradykinin (7.86 X 10(‐12)M), when present in both mucosal and serosal solutions, produced a biphasic effect on mucosal sodium and water transfer. When basal transfer was low a stimulation was observed whereas an inhibition of transfer was observed when basal transfer was high. Bradykinin at concentrations of 7‐86 X 10(‐11) and 7‐86 X 10(‐13) M produced qualitatively similar effects. 3. Inhibition of transfer was observed whether bradykinin was present in the mucosal, serosal or both solutions. Stimulation of transfer was observed only when bradykinin was present in the serosal solution. 4. Theophylline (1 mM), alone inhibited water transfer at high and intermediate levels of basal transfer, and significantly potentiated the inhibitory effect of bradykinin (7‐86 X 10(‐12)M) on water transfer at intermediate levels of control transfer. 5. Cyclic AMP (1 mM) inhibited water transfer when basal transfer was high. Dibutyryl cyclic AMP (1 mM) inhibited water transfer at all levels of basal transfer. Dibutyryl cyclic AMP (1 mM) and bradykinin (7‐86 X 10(‐12)M) together produced a significantly greater inhibition of water transfer than either agent alone, at intermediate basal transfer. 6. It was observed that the action of bradykinin upon sodium and water transfer consists of two different and opposing effects. It is possible that the inhibitory effect of bradykinin upon water transfer is related to increased cyclic AMP activity.
The effect of sympathetic nerve stimulation on serum gastrin, gastric acid secretion and mucosal blood flow responses to meat extract stimulation in anaesthetized cats.
Authors: Blair E L , Grund E R , Reed J D , Sanders D J , Sanger G , Shaw B
Published: December 2014

Chloralose anaesthetized cats were prepared with fundic and antral pouches. Fundic mucosal blood flow was measured by the amidopyrine technique and serum gastrin was measured by radioimmunoassay. 2. Meat extract suspension in the pyloric antrum produced a highly significant sixfold increase in arterial serum gastrin concentration (P less than 0‐001). 3. The mean ratio of the fundic mucosal blood flow to acid secretory responses (deltaMBF/deltaH+ ratio) of 0‐142 +/‐ 0‐026 (25) ml./muequiv H+, is very similar to the values previously published for exogenous gastrin stimulation. 4. Splanchnic nerve stimulation, during responses to meat extract stimulation, produced significant reductions in gastric acid secretion (P less than 0‐025), fundic mucosal blood flow (P less than 0‐02), Arterial serum gastrin concentration (P less than 0‐01) And gastrin delivered to the mucosa (P less than 0‐001). 5. In the 30 min period following the end of splanchnic nerve stimulation only arterial serum gastrin concentration remained significantly reduced.
Studies of the contractility of mammalian myocardium at low rates of stimulation.
Authors: Allen D G , Jewell B R , Wood E H
Published: December 2014

1. Measurements have been made of tension development in papillary muscles isolated from the right ventricles of young cats. In some cases membrane potentials have also been recorded, using micro electrodes. 2. Regular contractions at a stimulation rate of 20 min(‐1) (the 'standard' rate used in this study) had the following characteristics (30 degrees C): peak tension developed, about 43mN mm(‐2); time to peak tension and time to 80% repolarization of the cell membrane, about 400 ms. 3. The corresponding figures for the first contraction after a rest of several minutes (rested state contraction) were: tension developed, about 4mN mm(‐2); time to peak tension and time to 80% repolarization of the cell membrane, about 560 ms. Sometimes there was also an early peak in the mechanical response, about 250 ms after stimulation. 4. The time course with which tension development declined when the muscle was allowed to rest was examined under various conditions. It was found to decline more slowly when the muscle was potentiated by raising the bathing Ca2+ concentration and by stimulation at rates above 20 min(‐1). 5. Tension development in rested state contractions was found to depend on the Ca2+ and Na+ concentrations in the bathing solution. The full effect of a change in either could be produced by exposing the resting muscle to the altered ionic conditions. 6. These experimental findings have been interpreted in terms of a simple model of the calcium movements involved in excitation‐contraction coupling in the myocardial cell.