bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity of toad rods: Dependence on wave‐length and background illumination.
Authors: Fain G L
Published: December 2014

1. There are five morphological types of photoreceptors in the retina of the toad, Bufo marinus: red and green rods, single cones, and the principal and accessory members of double cones. The largest and most abundant of these is the red rod. 2. Intracellular recordings were used to investigate the dependence of the sensitivity of red rod responses on wave‐length and background light. 3. The spectral sensitivity of dark‐adapted and moderately light‐adapted red rods can be satisfactorily fitted with the absorbance spectrum of the red rod photopigment. There are no significant contributions to red rod responses from cones or green rods. 4. In contrast, L‐type horizontal cells, whose responses are dominated by input from the red rods near threshold, can be shown also to receive input from cones. 5. Steady background light produces a response in the red rods consisting of an initial hyperpolarization, followed by a decay of potential to a steady‐state plateau level. The slow decay of response amplitude is accompanied by an increase in sensitivity to increment test flashes. 6. The increment sensitivity at steady‐state decreases with increasing background intensity according to a modified Weber‐Fechner relation. The dependence of increment sensitivity on the wave‐length of the background light can be predicted by the red rod spectral sensitivity, showing that cones do not influence the light adaptation of rods. 7. At a backgound intensity of 11‐5 log equivalent quanta cm‐2sec‐1, sensitivity begins to deviate from the Weber‐Fechner relation. In background light one log unit brighter, the rods are completely saturated. 8. Small responses having the spectral sensitivity of cones can be recorded from saturated rods. These potentials have a prominent off response whose wave form resembles the d‐wave of the e.r.g. 9. A comparison of the increment‐‐sensitivity curves of single receptors shows that rods are light‐adapted by backgrounds one thousand times dimmer than those which affect cones. The increment‐‐sensitivity curves of rods and cones cross, so that single cones become more sensitive than single rods even before the rods begin to saturate.
The effect of transmural pressure on pumping activity in isolated bovine lymphatic vessels.
Authors: McHale N G , Roddie I C
Published: December 2014

1. Isolated preparations of bovine mesenteric lymphatics containing about seven valved segments were cannulated and set up in a perfusion system so that, when the preparation was not contracting, the inflow and outflow pressures were exactly equal and there was no flow through the preparation. 2. Transmural pressure was varied by raising or lowering the inflow and outflow pressures simultaneously by the same amount. 3. The isolated vessels showed rhythmic spontaneous activity; it consisted of quick contractions which spread rapidly over the entire preparation, each followed by a rapid relaxation and a diastolic pause. 4. With each contraction, the preparation decreased in both length and diameter and generated an outflow pressure which pumped fluid in the direction determined by the orientation of the values. 5. Raising the transmural pressure in the preparation increased the output of the preparation; this was achieved by an increase in both the frequency and force of the individual contractions. 6. It was concluded that bovine lymphatics could propel fluid by their intrinsic activity at a rate which was related to the degree of distension of their walls.
Gastric emptying of organic acids in the dog.
Authors: Blum A L , Hegglin J , Krejs G J , Largiadèr F , Säuberli H , Schmid P
Published: December 2014

Test meals of 300 ml. of six different organic acids were instilled into the stomach of six healthy mongrel dogs. Citric, acetic, propionic, lactic, tartaric and succinic acid were given in 50, 100, 150, and 200 mN concentrations. 2. During the emptying process, the gastric contents were aspirated and immediately re‐instilled at 10 min intervals, and the following parameters were recorded: volume, concentration of the organic anion, pH, hydrogen ion concentration and osmolarity. 3. By multiple stepwise regression analysis, the combination of parameters which most effectively determines gastric emptying rate was found to be: concentration of the organic anion, followed by intragastric volume and number of previous test meals given on the same day. These three parameters appear in the equation for gastric emptying rate in which the individual characteristic of each acid is expressed by a constant. 4. Among the various acids, inhibition of emptying rate increases with rising number of carboxylic groups of the acid and its molecular weight. 5. After proximal gastric vagotomy, emptying rate of organic acids is independent of volume, and emptying approaches an exponential pattern. 6. A model for gastric emptying of organic acids with at least three different receptors is proposed: one for the structure of the organic acid, one for concentration and one for intragastric volume.
The responses of human muscle spindle endings to vibration during isometric contraction.
Authors: Burke D , Hagbarth K E , Löfstedt L , Wallin B G
Published: December 2014

1. An human subjects, vibration of amplitude 1‐5 mm and frequency 20‐220 Hz was applied to the tendons of muscles in the leg to examine the effects on the discharge of primary and secondary endings during manoeuvres designed to alter the level of fusimotor drive. 2. In four experiments, the peroneal nerve was completely blocked with lidocaine proximal to the recording site in order to de‐efferent spindle endings temporarily. The responses to muscle stretch and vibration, as seen in multi‐unit recordings and in single unit recordings, were similar during the block as in the relaxed state prior to the block. Thus, these experiments provided no evidence for a functionally effective resting fusimotor drive. 3. The responses to vibration of nine primary endings and four secondary endings were examined during isometric voluntary contractions of the receptor‐bearing muscles. Providing that the endings were responding submaximally in the relaxed state, voluntary contraction enhanced the response to vibration, suggesting co‐activation of the fusimotor system sufficient to compensate for mechanical unloading. Unloading effects were observed during contractions of neighbouring synergistic muscles, indicating a close spatial relationship between the co‐activated skeletomotor and fusimotor outflows. 4. Recordings were obtained from ten primary endings and seven secondary endings during isometric reflex contractions resulting from the vibratory stimulus (TVR contractions). For twelve endings, the appearance of the tonic vibration reflex in the receptor‐bearing muscle resulted in a significant decrease in the response to vibration, suggesting that the endings were unloaded by the extrafusal contraction. On voluntary suppression of the reflex contraction spindle responses reverted to their previous levels. 5. These results suggest that the tonic vibration reflex, like the tendon jerk reflex, operates predominantly or exclusively on alpha motoneurones and that it does not utilize the same cortically originating efferent pathways as are used in the performance of voluntary contractions.
Functional and morphologic maturation of superficial and juxtamedullary nephrons in the rat.
Authors: de Rouffignac C , Monnens L
Published: December 2014

The development of single nephron glomerular filtration rate (SNGFER) was studied in both superficial and juxtamedullary nephrons in rats in relation to concomitant morphologic maturation. These experiments were carried out in rats between 23 and 91 days of age (between 36 nad 275 g body weight) with the [14C]ferrocyanide infusion technique. 2. SNGFR of the superficial and juxtamedullary nephrons increased with body weight, glomerular volume and proximal tubular length. 3. The ratio SNGFR of the superficial (S) nephrons/SNGFR of the juxtamedullary (JM) nephrons rose from 0‐60 in the 40‐60 g rats to 0‐84 in the adult rats, demonstrating the centrifugal functional maturation of the nephrons. 4. The S/JM ratio for both glomerular volume and tubular length was constant and averaged 0‐72+/‐‐0‐12 and 0‐81+/‐0‐05, respectively, indicating that while the increase in SNGFR was greater for S than for JM nephrons, this was not accompanied by concomitant disproportionate increases of glomerular volume and/or proximal tubular length between these nephron categories during development in the rat.
Identification of algogenic substances in human erythrocytes.
Authors: Bleehen T , Hobbiger F , Keele C A
Published: December 2014

Lysates of human erythrocytes produce pain when applied to a human blister base. The algogenic material is not potassium, acetylcholine, bradykinin, 5‐hydroxytryptamine, histamine or a prostaglandin, and is dialysable. 2. Fractionation of dialysates of freshly lysed erythrocytes by Sephadex gel filtration coupled with assays on the human blister base preparation showed that the algogenic material was a mixture of the adenyl compounds adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP). 3. On the human blister base preparation ATP, ADP and AMP had comparable activity and produced threshold pain in a concentration of 2 muM. 4. The rabbit isolated jejunum preparation was found useful in these studies since ATP, ADP and AMP produced a relaxation which was proportional to their concentration in test samples obtained from dialysates. Of more limited usefulness was the rat isolated stomach strip preparation on which ATP and ADP produced contractions which also were proportional to their concentrations in text samples. 5. The possible role of adenyl compounds in the production of pain in vivo is discussed.
Current‐voltage relationships in the crystalline lens.
Authors: Eisenberg R S , Rae J L
Published: December 2014

1. Electrical coupling between the cells of the crystalline lens of the frog eye was studied using two intralenticular micro‐electrodes, one to pass current and one to record potential. In most experiments, both electrodes were placed just inside the posterior surface of the lens at a depth of approximately 200 mum from the surface. Step functions of current were applied and the time course of the resulting change in voltage was measured at many different electrode separations. 2. The voltage change has both a fast component, which occurs only locally in the region close to the current passing micro‐electrode, and a slow component, which is spatially uniform, independent of distance from the current micro‐electrode. 3. This behaviour is predicted by an electrical model of a single large spherical cell, and so that model can be used to analyse our data. 4. The resistivity of the lens 'interior' (both cytoplasm and coupling resistivity) is 625 omega cm; the resistance of the lens 'membrane' is 2751 omega cm2. 5. The data and analysis help to reconcile discrepancies between previous measurements of the electrical properties of the lens and show clearly that there is substantial electrical coupling from cell to cell. The method should allow investigation of the role of electrical coupling in cataract formation in the crystalline lens.
The effects of pH changes on the frequency of miniature end‐plate potentials at the frog neuromuscular junction.
Authors: Cohen I , Van Der Kloot W
Published: December 2014

As reported by Landau & Nachshen (1975), a decrease in extracellular pH at the frog neuromuscular junction leads to an increase in min.e.p.p. frequency. 2. Decreasing the extracellular pH still increases the min.e.p.p. frequency when the bathing Ringer contains 10 mM‐Ca2+, in place of the usual 2‐5 mM. At the mammalian neuromuscular junction, the elevated Ca2+ blocks the effect of the pH change on the min.e.p.p. frequency (Hubbard, Jones & Landau, 1968). 3. In Cl‐‐free solution (isethionate or methylsulphate substitution) min.e.p.p. frequency is no longer a monotonic function of decreasing pH. Instead there is an optimum pH for spontaneous release between pH 6‐6 and 8‐6. 4. This suggests that in Cl‐ containing Ringer min.e.p.p. frequency increases with increasing extracellular acidity because there is a change in the PCl of the nerve terminal leading to a depolarization. In agreement with this idea,in low Ca2+ Ringer, acid pH has little effect on the min.e.p.p. frequency. 5. Decreasing the intracellular pH by raising PCO2 produces substantial increases in the min.e.p.p. frequency. The effects are much greater than the effects of equal changes of H+ in the extracellular solution. 6. Possible explanations for the effects of increased PCO2 are discussed. Although release of Ca2+ from mitochondria or other unknown effects of intracellular pH change or molecular CO2 are possible, the results do give some support to the hypothesis that an important step in transmitter release involves an electrostatic repulsion between fixed membrane surface charges on the transmitter containing vesicles and the inner face of the nerve terminal. The surface charge density would be decreased by a lower pH in the axoplasm, and this would increase the rate of spontaneous transmitter release, in agreement with the observations.
Differential effects of tetracaine on delayed potassium channels and displacement currents in frog skeletal muscle.
Authors: Almers W
Published: December 2014

1. Delayed K+‐currents and displacement currents were studied with a voltage‐clamp technique. 2. In normal fibres, the conductance of the delayed channel grows e‐fold per 3 millivolts at sufficiently negative potentials and reaches a limiting value of 2‐10 m‐mho/cm2 (mean 5‐8 m‐mho/cm2) at positive potentials. Adding tetracaine (2 mM) reduces the limiting conductance, shifts the voltage‐dependence of the delayed channel to +25 mV more positive potentials and slows the kinetics fourfold. 3. By contrast, the displacement currents are virtually unaltered by 2 mM tetracaine. Their voltage‐dependence is shifted by less than 5 mV and their kinetics are unaffected. 4. Tetraethylammonium ions (TEA) are known to slow the kinetics of delayed K+‐channels fivefold but fail, like tetracaine, to change the kinetics of the displacement currents. 5. Both tetracaine and TEA have thus large effects on the 'gating' of the delayed channel, yet little or none on the displacement currents. This suggests that the displacement currents in skeletal muscle are for the most part unrelated to the opening and closing of delayed channels. It is estimated that 'gating' the delayed channel in muscle may require no more than 1 or 2% of the observed charge displacement.
The force generated by a visceral smooth muscle.
Authors: Gabella G
Published: December 2014

1. Strips of taenia coli from the caecum of the guinea‐pig were mounted in an organ bath at 37 degrees C; isometric contractions were elicited with 10(5)M carbachol. Each taenia was stretched to the length at which it produced the maximum active tension; it was then fixed and embedded for measurement of the transverse sectional area. 2. The maximal force produced ranged between 96‐1 and 138‐3 mN. This corresponded to a force of between 251 and 513 mN.mm(2) (mean: 416 +/‐28 [n = 10]). Temperature changes in the range 23‐38 degrees C had little effect on the maximal force output.3. When allowance is made for the extracellular space (about 32% of the transverse sectional area), for the non‐muscular cells present in the taenia (about 5%), and for the non‐contractile material present in the muscle cells (about 10%), the maximal force generated was about 734 mN.mm(2) of contractile material (or almost twice as large as in skeletal muscle).4. Electron microscopy revealed terminal apparatuses at the ends of muscle cells, anchoring the cells to the connective tissue, and cell‐to‐cell junctions (attachment plaques). In addition, many dense patches of dense bands, sites near the cell surface where filaments are seen to end, were scattered along the entire length of the muscle cell and lay close to bundles of collagen fibrils. 5. It is suggested that the production of such a large force by this smooth muscle is partly explained by the lateral attachment of some contractile units to sites along the entire cell length, which in their turn are anchored to the collagen network; the latter may be considered a sort of intramuscular tendon.
Cyclic adenosine 3', 5'‐monophosphate in cerebrospinal fluid during thermoregulation and fever.
Authors: Dascombe M J , Milton A S
Published: December 2014

1. Samples of cerebrospinal fluid (c.s.f.) have been taken from the cisterna magna of unanaesthetized cats, whilst rectal temperature was recorded, during exposure of the animals to various ambient temperatures and during fever induced by pyrogen. The concentration of adenosine 3', 5'‐monophosphate (cyclic AMP) in samples of c.s.f. has been assayed. 2. Cats exposed to low ambient temperatures (‐2 to +2 degrees C) for 3 h maintained body temperature by both behavioural and autonomic heat gain activity. Exposure of cats to high ambient temperatures (44 ‐ 45 degrees C) for 3.5 h caused a rise in body temperatures of about 2.5 degrees C, despite behavioural and autonomic heat loss activity. Neither cold nor heat stress had a significant effect on c.s.f. cyclic AMP. 3. Fever induced by intravenous Shigella dysenteriae (2 and 20 mug/kg) was associated with a dose‐related increase in the concentration of cyclic AMP in c.s.f. Paracetamol (75 mg/kg) injected I.P. before the onset of fever, suppressed the increase in both temperature and c.s.f. cyclic AMP in response to pyrogen. Paracetamol (50 and 100 mg/kg), injected after the onset of fever, caused a fall in temperature, which was not associated with a decrease in the concentration of cyclic AMP in c.s.f. 4. Fever induced in cats by intravenous Shigella dysenteriae (20 mug/kg) was associated with an increase in the concentration of cyclic AMP in plasma as well as in c.s.f. 5. The sodium salt of cyclic AMP (0.1‐10 mg/kg) injected I.V. into unanaesthetized cats caused a dose‐related hypothermia, which was associated with autonomic heat loss activity and a dose‐related increase in the concentration of cyclic AMP in cisternal c.s.f., which was not mimicked by adenosine. 6. It is concluded that the raised concentrations of cyclic AMP in c.s.f., in response to pyrogen I.V., do not mediate fever in the cat and that the concentration of cyclic AMP in cisternal c.s.f. may be affected by changes in the plasma concentration of the nucleotide.
Behaviour and aeration of the respiratory system in the domestic fowl embryo.
Authors: Vince M A
Published: December 2014

1. The monitoring of developmental stage and under‐water dissection were used to examine the initial aeration of the respiratory system in domestic fowl embryos. 2. A virtually complete absence of free air within the chorioallantois was found before the beak had begun to make 'beak‐clapping' movements, even when the membranes were already draped over its tip. 3. During the 'beak‐clapping' stage, but before the membranes were pierced and before respiratory movements had begun, many embryos were found to contain free bubbles of air within the trachea and air sacs. 4. All embryos in which the respiratory system was aerated were found also to have froth in the crop or other parts of the digestive system. 5. Air was found in both the respiratory and digestive systems of all embryos examined after membrane penetration by the beak. 6. When air was injected into the chorioallantois before the stage of initial aeration it was recovered 5 min later from both the respiratory and digestive systems in under‐water dissections. 7. It is suggested that lung ventilation takes place in the avian embryo in three distinct stages: the major air‐ways become aerated, then respiratory movements begin and lastly the tertiary bronchi are slowly aerated. It is suggested also that movements involved in the imbibing of fluids play a part in aeration before the membranes are pierced.
Inhibition of spinocervical tract discharges from localized areas of the sensorimotor cortex in the cat.
Authors: Brown A G , Coulter J D , Rose P K , Short A D , Snow P J
Published: December 2014

1. Intracortical microstimualtion (ICMS) was applied within the sensorimotor cortex of cats anaesthetized with chloralose. 2. The effects of the ICMS were examined on the number of impulses in spinocervical tract (SCT) cells (recorded extracellularly in the contralateral lumbosacral spinal cord) evoked by peripheral stimulation. 3. Inhibition of SCT discharges was produced by ICMS in two distinct regions of the sensorimotor cortex. 4. One inhibitory regions was in part of cytoarchitectonic area 4 gamma in the upper bank of the cruciate sulcus. It sometimes extended caudally into area 4 delta, medially into area 3 alpha and/or rostrally into the part of area 4 gamma on the caudal lip of the cruciate sulcus. 5. The other inhibitory region was in the medial part of the posterior sigmoid gyrus and included parts of areas 3 alpha, 3 beta, 1, 5 alpha and 5 beta. 6. Most inhibitory sites were in cortical layers III, V and VI. 7. No regions were found in which ICMS consistently caused facilitation of SCT discharges.
Effects of the calcium ionophore A23187 on pancreatic acinar cell membrane potentials and amylase release.
Authors: Poulsen J H , Williams J A
Published: December 2014

1. The effects of the Ca2+‐ionophore A23187 and the non‐metabolizable cholinergic agonist bethanechol on acinar cell membrane potentials and amylase release from the superfused mouse pancreas were studied. 2. In the presence of extracellular Ca2+ (2.56 mM), A23187 (10(‐5)M) and bethanechol (3 X 10(‐5)M) caused an equal increase in the release of amylase. Both stimulants depolarized theacinar cells, A23187 by 6‐0 mV and bethanechol by 12‐3 mV. 3. When Ca2+ and Mg2+ were removed from the superfusate, the ability of A23187 to increase the rate of amylase release was virtually abolished, while the effect of bethanechol remained unaltered. Similarly, in the absence of these divalent cations, A23187 did not cause depolarization of the acinar cells, while depolarization in response to bethanechol was largely normal. Consequently it is unlikely that cholinergic agonists initiate secretion by activating a Ca2+‐ionophore‐like mechanism in the cell membrane. 4. When the concentration of Ca2+ in the medium was raised to 10 mM was the only extracellular divalent cation present, the depolarization in response to A23187 was increased to 11‐8 mV. When Mg2+ in a concentration of 10 mM was the only extracellular divalent cation, the depolarization was only 2‐1 mV. 5. The Ca2+ dependent, A23187‐induced depolarization was abolished in the absence of Na+ (Tris substitution). Addition of Na+ to the superfusate caused an immediate depolarization. 6. It is concluded that the Ca2+ dependent depolarization of pancreatic acinar cells induced by A23187 is not directly due to an increased divalent cation conductance. Our findings are consistent with the view that the depolarization is due to an increased influx of Na+ resulting from a Ca2+ mediated increase in Na+ permeability.
The effect of insulin on the transport of sodium and potassium in rat soleus muscle.
Authors: Clausen T , Kohn P G
Published: December 2014

1. The action of insulin on the transport and the distribution of Na and K has been studied in rat soleus muscles incubated at 30 degrees C in glucose‐free Krebs‐Ringer bicarbonate buffer. 2. Measurements of the uptake and the wash‐out of 22Na indicate that the muscles contain an intracellular pool of Na available for transport which is confined to the water space not available to sucrose. Ouabain (10(‐4)‐10(‐3)M) inhibited 22Na efflux by 69% (0‐287 micronmole/g tissue wet weight per minute) and 42K‐influx by 40% (0‐196 micronmole/g tissue wet weight per minute). When all extracellular Na was replaced by Li, both 22Na‐efflux adn 42K‐influx were inhibited to about the same extent and ouabain produced very little further inhibition. 2,4‐dinitrophenol decreased the ouabain‐resistant component of 22Na‐efflux by 39%. 3. Insulin (from 0‐1 to 100 mu./ml.) increased the rate coefficient of 22Na‐efflux by from 11 to 46% within 15 min. In the presence of ouabain (10(‐3)M), the same relative increase was obtained, indicating that the hormone stimulates the glycoside‐sensitive and the glycoside‐insensitive Na transport to a similar extent. The effect of insulin on 22Na‐efflux was not abolished by tetracaine (0‐5 X 10(‐3)M), phlorizin (0‐5 X 10(‐2)M) or by the substitution of Na, K, Mg or Ca. In the presence of 2,4‐dinitrophenol (0‐5 X 10(‐4)M) or at temperatures below 15 degrees C, the hormone produced no detectable change in 22Na‐efflux. 4. Insulin increased 42K‐influx from 0‐525 to 0‐664 mumole/g tissue wet weight per minute. This effect was entirely blocked by ouabain but not by tetracaine. Insulin produced a 14% transient decrease in 42K‐efflux. 5. The continued exposure to insulin led to a new steady state, in which the intracellular Na pool was decreased from around 10 to around 5 mumole/g tissue wet weight and the K content increased by an equivalent amount. In the presence of ouabain or at low extracellular concentrations of K, insulin increased the rate of 22Na‐influx by around 35%. This effect was blocked by 2,4‐dinitrophenol but not be tetracaine. 6. It is concluded that insulin stimulates the active coupled transport of Na and K, possibly by increasing the relative Na‐affinity of the system mediating this process.
Comparison of the critical periods for monocular and directional deprivation in cats.
Authors: Berman N , Daw N W
Published: December 2014

1. Earlier experiments rearing kittens with one eye closed and reversing the closure after a certain age, or rearing kittens in a rotating drum and reversing the direction after a certain age, suggest that the critical periods for ocular dominance and directional sensitivity may differ. Since these results were obtained by different investigators in different laboratories, we have made a direct comparison of the two types of visual deprivation. 2. Four pairs of litter‐mate kittens (matched in weight) were reared. One animal in each pair was monocularly deprived with subsequent eye reversal; the other animal was directionally deprived with reversal of drum direction. All reversals took place at age 5 weeks. Both kittens in a given pair were either 'left first' (left eye open first or left direction first) or both were right first. One died prematurely. 3. Recordings were made from the visual cortex at some age after 4 months. Some recordings were made in the left cortex and some in the right. In all cases of monocular deprivation, the majority of cells were driven by the eye that was open last (i.e. open after 5 weeks of age). In all cases of directional deprivation, the majority of the cells preferred movement in the first direction of exposure (i.e. the direction before 5 weeks of age). 4. We conclude that the critical period for directional deprivation terminates earlier than the critical period for monocular deprivation.
Input from ipsilateral proprio‐ and exteroceptive hind limb afferents to nucleus Z of the cat medulla oblongata.
Authors: Johansson H , Silfvenius H
Published: December 2014

1. Extracellular recordings have been made from proprio‐ and exteroceptive neurones in nucleus Z of the cat medulla oblongata. 2. Seventeen non‐relay cells were excited by ipsilateral hind limb group I muscle afferents. Their functional were similar to those of the corresponding relay cells (Johansson & Silfvenius, 1977), i.e. activation by axon‐collaterals of dorsolateral fascicle (DLF) fibres was observed, indicative of an input from the dorsal spinocerebellar tract (DSCT) to these neurones. The non‐relay cells differed, however, from the relay cells in that a larger proportion of them were disynaptically connected to the spinal fibres. It is suggested that the non‐relay cells by inhibition modulate the group I relay transmission in nucleus Z. 3. Fifteen cells were excited by ipsilateral hind limb low threshold skin afferents with their spinal fibres at the first cervical segment located either in the DLF or in the dorsal column (DC). Evidence for a cutaneous hind limb bulbothalamic path independent of that of the DC and of the spinocervicolemniscal path is presented. 4. Six cells were activated by ipsilateral hind limb joint afferents at low threshold. At the C1 level the spinal fibres were located either in the DLF or in the DC. No joint activated relay‐cells were encountered. Axon‐collateral activation of DLF‐linked joint cells was observed during cerebellar stimulation, indicating that segmental DSCT cells mediated the joint input to nucleus Z. 5. The topographical organization within nucleus Z and its input relation to the DSCT is discussed.
The relation of axonal transport of mitochondria with microtubules and other axoplasmic organelles.
Authors: Friede R L , Ho K C
Published: December 2014

Axonal transport of mitochondria was studied in frog sciatic nerves incubated in agents selected for their known or alleged effect on microtubules or axonal flow. Quantitative data on mitochondria, microtubules, neurofilaments, endoplasmic reticulum, and cross‐sectional area of the axon indicate that axonal transport of mitochondria is dependent on microtubules. When more than half of the microtubules are destroyed, the axonal transport of mitochondria is diminished in proportion to the destruction of microtubules. Axonal transport of mitochondria is not related to neurofilaments and endoplasmic reticulum. Changes in the cross‐sectional area of axons, even upon reduction to half the normal size, do not noticeably affect mitochondrial transport. Cyanide which blocks oxidative metabolism also blocks axonal transport of mitochondria, but analysis of fine structure indicates that cyanide is destructive to microtubules as well.
Inhibition of the intracellular release of calcium by Dantrolene in barnacle giant muscle fibres.
Authors: Desmedt J E , Hainaut K
Published: December 2014

1. Ca movements in resting and in activated single giant muscle fibres of the barnacle were analysed before and after exposure to Dantrolene Na, a synthetic hydantoin derivative. 2. In fibres micro‐injected with the photoprotein aequorin, the resting rate of light emission (resting glow) reversibly decreased upon exposure to Dantrolene. Similar results were obtained if the fibre had first been equilibrated in a O Ca‐1 mM‐EGTA medium. 3. The influx of 45Ca into resting muscle fibres was not modified by 35 micronM Dantrolene which also failed to significantly reduce the influx of 45Ca into muscle fibres which had been depolarized by exposure to external solutions in which K+ had been increased to 60 or 200 mM. 4. In fibres micro‐injected with 45Ca, the calcium efflux was reversibly decreased by Dantrolene. This effect was still observed in O Ca medium and in O Ca‐ONa medium. A possible effect of Dantrolene on the Na‐Ca exchange process at the outer membrane was excluded by showing that when the direction of the Ca2+ movement was inverted in aequorin‐loaded fibres by the sudden removal of Na+ from the external medium, a marked increase in the resting glow was recorded which was not affected by exposure to Dantrolene. 5. It is argued that the reduction of Ca2+ efflux by Dantrolene does not result from any direct inhibitory effect on the metabolically driven Ca pump at the outer membrane, but that it is rather related to the reduction of the concentration of myoplasmic Ca2+ which is indeed demonstrated by the reduced resting glow. This in turn is thought to result from a shift in the balance between Ca2+ movements into and out of the intracellular storage sites, and namely the sarcoplasmic reticulum (SR). 6. The Ca2+ transient in aequorin‐loaded fibres and the force of the isometric contraction elicited by imposed membrane depolarizations were markedly reduced by Dantrolene. The electrochemical threshold for eliciting intracellular Ca2+ release was not significantly modified. The linear relation between membrane depolarization and Ca2+ transient became less steep. The process of sequestration of myoplasmic Ca2+ back into SR was not significantly affected by Dantrolene which appeared to inhibit rather selectively the Ca2+ release from SR into the cytosol.
On the effect of calcium on the frequency of miniature end‐plate potentials at the frog neuromuscular junction.
Authors: Matthews G , Wickelgren W O
Published: December 2014

1. The effect of the extracellular Ca concentration on the frequency of miniature end‐plate potentials (min. e.p.p.s) at the frog neuromuscular junction was studied. 2. In saline containing elevated K (5 or 11 mM), the frequency of min. e.p.p.s increased as Ca concentration was increased from 0‐1 to 1‐3 mM. However, with further increases of Ca concentration up to 10 mM, min. E.P.P. frequency declined. 3. In saline containing the normal concentration of K (2 mM), increasing Ca concentration from 0‐1 to 10 mM produced a slight, monotonic increase in min. e.p.p. frequency. 4. The non‐monotonic effect of Ca on min. e.p.p. frequency in preparations depolarized by elevated K is consistent with the existence of two opposing effects of Ca on transmitter release. Firstly, raising the external concentration of Ca increases the electrochemical potential for Ca entry, which tends to increase Ca influx and transmitter release. Secondly, increasing external Ca concentration increases electrostatic screening of fixed negative charges on the outer surface of the nerve terminal membrane. Such an increase in screening of charges near voltage‐sensitive Ca gates would produce a hyperpolarization across the gates and they would tend to close, an effect which would tend to decrease Ca influx. The monotonic increase in min. e.p.p. frequency with increasing Ca concentration in 2 mM‐K is consistent with the voltage insensitivity of the Ca gates at potentials close to the normal resting potential.
Regulation of cerebrospinal fluid bicarbonate by the cat choroid plexus.
Authors: Husted R F , Reed D J
Published: December 2014

1. The regulation of cerebrospinal fluid (c.s.f.) bicarbonate concentration was studied using the cat choroid plexus isolated in a chamber in situ. 2. Decreases in plasma bicarbonate concentration caused relatively small changes in the c.s.f. bicarbonate concentration. 3. Alterations in c.s.f. bicarbonate concentration (c.s.f. HCO3‐=9 or 28 m‐equiv/l.) were countered by changes in the bicarbonate concentration of the fluid produced by the plexus or in the rate of bicarbonate transport which returned c.s.f. bicarbonate towards normal. 4. There was significant regulation of pH in the choroid plexus fluid during hypocapnia and hypercapnia. 5. Alterations of plasma acid‐base status did not significantly alter the potential difference across the choroid plexus. However, the potential difference increased when c.s.f. bicarbonate was increased and decreased when c.s.f. bicarbonate was decreased. 6. The data indicate that the bicarbonate concentration in the c.s.f. is actively regulated by the choroid plexus during acid‐base disturbances occurring either systemically or in the c.s.f.
The site and receptors responsible for the inhibition by sympathetic nerves of intestinal smooth muscle and its parasympathetic motor nerves
Authors: Gillespie J. S. , Khoyi M. A.
Published: December 2014

1. The effects of three inhibitory stimuli, sympathetic nerve stimulation, noradrenaline (NA) and isoprenaline have been examined on three forms of motor activity in the rabbit colon, the response to pelvic (parasympathetic) nerve stimulation, acetylcholine (ACh) and spontaneous tone.

2. The response to pelvic nerve stimulation is most effectively inhibited by sympathetic nerve stimulation, much less effectively by NA and hardly at all by isoprenaline. The sympathetic nerves can inhibit the pelvic response at frequencies of stimulation which do not affect spontaneous tone. The inhibitory effect of sympathetic stimulation, and of NA, on the pelvic response is reduced by phentolamine 5 × 10−6
M and unaffected by propranolol 5 × 10−6
M suggesting the effect is mediated via α receptors.

3. The response to ACh is inhibited by all three stimuli equally. The inhibitory effect of sympathetic nerve stimulation and of isoprenaline is reduced by propranolol 5 × 10−6
M. The inhibitory effect of NA is also reduced by propranolol but to a lesser extent. Phentolamine 5 × 10−6
M has a small effect in reducing the inhibitory effect of sympathetic nerve stimulation or of NA. This effect of phentolamine is lost if the participation of motor nerves in the response to ACh is excluded by either tetrodotoxin 10−7 g/ml. or cold storage for 10‐14 days. These results suggest that inhibition of the ACh response takes place mainly at the muscle by activation of β receptors but that ACh may have a small indirect stimulant action through motor nerves and this is susceptible to inhibition through α receptors.

4. All three stimuli are equally effective in lowering smooth muscle tone. This inhibitory effect of sympathetic nerve stimulation and of isoprenaline is reduced by propranolol 5 × 10−6
M and unaffected by phentolamine 5 × 10−6
M. The inhibitory effect of NA is reduced by propranolol but again is less sensitive to block than the other two inhibitory stimuli. Phentolamine is without effect on the inhibitory action of NA and the combination of phentolamine with propranolol is no more effective than propranolol alone. These results suggest that NA liberated by sympathetic nerves and isoprenaline inhibit myogenic tone in the smooth muscle by an action on β receptors but the action of NA added to the bath cannot be fully explained in this way.
The gecko visual pigments: a microspectrophotometric study
Authors: Crescitelli Frederick , Dartnall H. J. A. , Loew E. R.
Published: December 2014

1. A dual system of visual pigments having absorbance maxima in the green and blue respectively has been found in the retinas of geckos both by single cell microspectrophotometry and by the method of extraction. Microspectrophotometry has shown the system to be present in four species of geckos representing four genera. Along with previous work with extracts (Crescitelli, 1972) this indicates a fundamental property in this family of lizards. No other photopigments have been detected.

2. For Gekko gekko, the species most intensively studied, the two pigments have absorbance maxima at 521 and 467 nm respectively. Both are based on vitamin A1 and both are characterized by absorbance spectra that nearly conform to the Dartnall nomogram.

3. In situ, the 521‐pigment is not temperature‐sensitive, and has virtually the same absorbance spectrum at 23° C as at 5° C. On extraction into digitonin solution, however, the absorbance spectrum of the pigment becomes temperature‐dependent and, though identical when measured at low temperature (2‐5° C) with the constant in situ curve, is displaced to shorter wave‐lengths at higher temperatures (10‐25° C). Thus the extract spectrum is relevant to the in situ spectrum only at low temperature (and in the presence of chloride ions).

4. Unlike the rhodopsins of several vertebrates, the gecko 521‐pigment displays no evidence of a meta‐III stage in the sequence of products following photic bleaching, even at low temperatures. This is true for the pigment in situ as well as in the extracted condition.
The effect of training and detraining on muscle composition in the horse.
Authors: Guy P S , Snow D H
Published: December 2014

1. Percutaneous needle biopsies were obtained from six limb muscles in six horses before and during a training programme of 10 or 15 weeks designed to involve both aerobic and anaerobic work. In a subsequent detraining period, biopsies were also taken after 5 and 10 weeks. 2. Samples were analysed biochemically for enzyme activity of lactic dehydrogenase (LDH), creatine phosphokinase (CPK), aldolase (ALD), citrate synthase (CS), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) and for glycogen content. Fibre typing was carried out histochemically before and 10 weeks after commencement of training. 3. There was a significant increase in the percentage of high myosin ATPase activity pH 9‐4/high oxidative (FTH) fibres with a corresponding decrease in high myosin ATPase activity pH 9‐4/low oxidative (FT) fibres and low myosin ATPase activity pH 9‐4/high oxidative (ST) fibres after 10 weeks training. 4. During training, enzyme activities increased progressively but at different rates with an approximate twofold increase in all of the enzymes except CPK by the end of the training period. Changes in all the muscles studied were similar. Glycogen content increased by approximately 33% which was significant when all the muscles were considered together. 5. A decrease in enzyme activity occurred after 5 weeks detraining. However at 10 weeks a consistent but inexplicable increase in all enzyme levels, except CS again occurred. 6. It is concluded that training increased greatly the activity of enzymes involved in both aerobic and anaerobic metabolism.
Temperature regulation and oxygen consumption in the developing macropod marsupial Setonix brachyurus.
Authors: Loh T T , Shield J
Published: December 2014

1. When kept at ambient temperatures of 17‐5 and 24 degrees C the colonic temperatures of joeys younger than 166 days declined to near ambient temperature. Pouch joeys of 166 days and older were however able to maintain their colonic temperatures at about 35 degrees C. 2. Joeys first developed the ability to sustain high O2 consumption rates in response to cooling, when aged between 144 and 169 days. Only when this latter facility was fully developed in ontogeny could body temperature be maintained in a cool environment. 3. When joeys older than 130 days were kept in a metabolism chamber at pouch temperature (37‐5 degrees C) and at high humidity their body temperatures quickly rose to lethal levels, demonstrating the need for cooling mechanisms whilst still contained within the pouch.
Effects of injections of calcium and EGTA into the outer segments of retinal rods of Bufo marinus
Authors: Brown J. E. , Coles J. A. , Pinto L. H.
Published: December 2014

1. Intracellular recordings were made from the outer segments of rods in the isolated, superfused retina of Bufo marinus. Cells were impaled under observation with a compound microscope fitted with an infra‐red image converter. Changes of membrane voltage and some concomitant changes of input resistance were measured in response to light, membrane polarization and iontophoretic injections.

2. By means of a double barrel micropipette, charge was passed into a rod from a micropipette barrel that contained Ca2+ while no net current crossed the plasma membrane. In about half the cells, immediately after the injection, a hyperpolarization was observed that decayed with a time course similar to the decay of the receptor potential.

3. Membrane hyperpolarization also occurred after a depolarizing current stopped flowing into a rod through a single barrel pipette that contained only K‐acetate. This hyperpolarization was accompanied by an increase of membrane conductance. The reversal potential for the conductance‐increase was between the voltage in the dark and the voltage in the absence of [Na+]out. A larger hyperpolarization became evident after an equal depolarizing current stopped flowing into a rod through a pipette that also contained Ca2+; this larger after‐hyperpolarization was due to both the cessation of depolarizing current and the injection of Ca2+.

4. A depolarization of 10‐20 mV that lasted 2‐60 sec became evident after hyperpolarizing current stopped flowing into a rod through a single‐barrel pipette filled with K‐EGTA. During the after‐depolarization, the responses to small, dim spots of light were attenuated. No depolarization was observed after passing hyperpolarizing currents into rods through pipettes that contained either acetate−, SO2-4 or MOPS−.

5. These results show that sequestration of [Ca2+]in depolarizes the plasma membrane and that an increase in [Ca2+]in hyperpolarizes the membrane mimicking the later part of the receptor potential. These findings support the hypothesis of Yoshikami & Hagins (1971) that Ca2+ is an intracellular messenger for excitation in vertebrate rods.
On the role of junctional cholinesterase in determining the time course of the end‐plate current.
Authors: Kordas M
Published: December 2014

1. The effect of membrane potential on the half‐time (t1/2) of the falling phase of the end‐plate current was studied both in the absence and the presence of anticholinesterase. 2. In absence of anticholinesterase the relation between log t1/2 and membrane potential was linear at negative, and not linear at positive levels of membrane potential. This relation was not affected by the quantity of the released transmitter. 3. In presence of an irreversible anticholinesterase the relation between log t1/2 and membrane potential was shifted towards higher values of log t1/2. This shift could be counteracted by decreasing the quantity of the released transmitter. 4. It is concluded that in presence of anticholinesterase the decay of the end‐plate current is slowed down because in this experimental condition the elimination of transmitter from the synaptic cleft is slowed down. 5. These observations were made in muscles bathed in Tris‐HCl buffered Ringer solution. If a phosphate buffered Ringer solution was used, the relation between log t1/2 and membrane potential was linear throughout the range of membrane potentials studied. The reason why different buffers give different results is not clear and should be further studied.
The effects of external sodium substitution on cell sodium and potassium in vascular smooth muscle
Authors: Friedman Sydney M.
Published: December 2014

1. The entry of Li into the vascular smooth muscle cells of the rat tail artery follows first‐order kinetics with a rate constant of approximately 1·3 hr−1 at 10 m
M‐[Li]o. The rate constant decreases gradually to ca. 0·5 hr−1 when the [Li]o/[Na]o ratio is increased.

2. Replacement of Na with Li over the range of [Li]o from 1 to 115 m
M, accomplished at constant ionic strength and osmolarity of the bathing solution, produces changes in cell Na and K without apparent change in cell water. At equilibrium, cell Li increases in linear proportion to [Li]o, at a ratio of 2:1 throughout the range. The increase in cell Li is associated with inverse falls in both cell K and Na such that the ratio of cell K to cell Na remains constant at ca. 10:1 throughout.

3. The changes in the ionic contents, induced by equilibration of the tissue with a Na‐free, Li‐substituted solution, are reversible.

4. Replacement of Na with sucrose over the range of 40‐115 m
M results, at equilibrium, in a linear fall in cell Na without conspicuous change in cell K. A constant portion of the cell Na, ca. 10 m‐mole/kg dry wt., does not participate in this exchange.

5. At equilibrium, reductions in [Na]o are reflected in corresponding reductions in apparent [Na]i such that the [Na]o/[Na]i ratio remains constant.