bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of remote retinal stimulation on the responses of cat retinal ganglion cells.
Authors: Barlow H B , Derrington A M , Harris L R , Lennie P
Published: December 2014

1. Action potentials were recorded from optic nerve fibres of lightly anaesthetized cats while parts of the retina remote from the receptive field were stimulated by a shifting grating. 2. Vigorous responses can be obtained under these conditions, confirming McIlwain (1966), Krüger & Fischer (1973), and others. 3. These 'shift responses' are not caused by fluctuations of stray light because (a) they cannot be reduced by deliberately increasing or decreasing the light falling on the receptive field synchronously with the shifting grating; (b) a steady adapting light applied to the receptive field does not raise the threshold for the responses, whereas adapting light on the peripheral retina does, and (c) the threshold for the responses is elevated more following bleaching adaptation of the periphery than following bleaching adaptation of the centre. 4. Shift responses are strong, of short latency, and brief in duration in brisk‐transient (Y‐type) neurones. With few exceptions they are weak but long‐lasting in brisk‐sustained (X‐type) neurones. 5. Shift responses are unlike responses from the main receptive field in having a distinct threshold; the magnitude of the response to weak gratings is not simply proportional to contrast, as is the case with weak stimuli applied to the receptive field. 6. It is thought that the excitatory pathway may involve amacrine cells, and that this mechanism may be concerned with the detection of the shifts of the image that occur with saccadic eye movements.
Inhibition of human motoneurones, probably of Renshaw origin, elicited by an orthodromic motor discharge
Authors: Bussel B. , Pierrot-Deseilligny E.
Published: December 2014

1. The pattern of variations of a test H‐reflex after a conditioning H‐reflex was investigated in human subjects by an experimental design in which both reflexes involved the same soleus motoneurones. This was made possible by using a method based upon a collision in the motor axons between the orthodromic conditioning reflex volley and the antidromic volley elicited by a test stimulus supramaximal for the motor axons.

2. The variations of the test reflex amplitude seen when increasing the conditioning reflex discharge were studied. This was made possible by facilitating the conditioning reflex without changing the strength of the afferent volley. This facilitation was obtained through a soleus stretch elicited by a stimulation of the plantar nerves.

3. The amplitude of the test reflex depended only on the size of the conditioning reflex discharge.

4. As long as the conditioning reflex was of low amplitude, all the motoneurones responsible for the conditioning response could be activated by the test volley, even though these motoneurones were undergoing after‐hyperpolarization. This indicates that, in man, the after‐hyperpolarization of the most excitable motoneurones can be completely overcome by a large Ia afferent volley.

5. Increasing the conditioning reflex beyond a specific value resulted in an absolute decrease in the number of motoneurones involved in the test reflex. The amount of this decrease was related only to the amplitude of the conditioning reflex.

6. This inhibition decreased progressively as the time interval separating the test stimulus from the conditioning stimulus increased. The time course of this inhibition was studied with conditioning reflexes of different amplitudes. The duration of the inhibition increased with the size of the conditioning reflex.

7. These results strongly suggest that Renshaw cells excited by the conditioning reflex are responsible for this inhibition. The results are in agreement with observations made in animals on recurrent inhibition.
Rod‐cone interaction in light adaptation
Authors: Latch M. , Lennie P.
Published: December 2014

1. The increment‐threshold for a small test spot in the peripheral visual field was measured against backgrounds that were red or blue.

2. When the background was a large uniform field, threshold over most of the scotopic range depended exactly upon the background's effect upon rods. This confirms Flamant & Stiles (1948). But when the background was small, threshold was elevated more by a long wave‐length than a short wave‐length background equated for its effect on rods.

3. The influence of cones was explored in a further experiment. The scotopic increment‐threshold was established for a short wave‐length test spot on a large, short wave‐length background. Then a steady red circular patch, conspicuous to cones, but below the increment‐threshold for rod vision, was added to the background. When it was small, but not when it was large, this patch substantially raised the threshold for the test.

4. When a similar experiment was made using, instead of a red patch, a short wave‐length one that was conspicuous in rod vision, threshold varied similarly with patch size. These results support the notion that the influence of small backgrounds arises in some size‐selective mechanism that is indifferent to the receptor system in which visual signals originate. Two corollaries of this hypothesis were tested in further experiments.

5. A small patch was chosen so as to lift scotopic threshold substantially above its level on a uniform field. This threshold elevation persisted for minutes after extinction of the patch, but only when the patch was small. A large patch made bright enough to elevate threshold by as much as the small one gave rise to no corresponding after‐effect.

6. Increment‐thresholds for a small red test spot, detected through cones, followed the same course whether a large uniform background was long‐ or short wave‐length. When the background was small, threshold upon the short wave‐length one began to rise for much lower levels of background illumination, suggesting the influence of rods. This was confirmed by repeating the experiment after a strong bleach when the cones, but not rods, had fully recovered their sensitivity. Increment‐thresholds upon small backgrounds of long or short wave‐lengths then followed the same course.
Differentiation of electrical and contractile properties of slow and fast muscle fibres.
Authors: Gordon T , Purves R D , Vrbová G
Published: December 2014

1. The development of the electrical and contractile properties of slow anterior latissimus dorsi (ALD) and fast posterior latissimus dorsi (PLD) muscles of the chick was studied. 2. At the earliest ages studied (14‐16 days of incubation), the membrane resistance was similar in both muscles. Subsequently the membrane resistance of PLD decreased, and that of ALD increased. Electrical differentiation continued after hatching. 3. The contractile speeds of ALD and PLD muscles were similar in embryos at 14‐16 days of incubation, and suddenly differentiated at 17‐18 days. Unlike the electrical properties, contractile speeds changed little after hatching. 4. It is suggested that the different electrical properties of the membrane of the two types of muscle fibre develop as a result of the particular type of excitation imposed by their nerves.
Voltage‐clamp experiments on frog single skeletal muscle fibres: evidence for a tubular sodium current.
Authors: Mandrino M
Published: December 2014

1. A late inward current following the initial sodium current is sometimes observed on frog single skeletal muscle fibres studied in voltage‐clamp conditions by the double sucrose‐gap method. 2. The late inward current is time and voltage dependent; it is sensitive to extracellular sodium concentration and inhibited by tetrodotoxin. Therefore, it is very probably carried by sodium ions. 3. It is assumed that the late current reflects a regenerative increase of sodium conductance in the tubular membrane. The main argument favouring this assumption is that the late current is never observed on detubulated fibres. 4. Inactivation studies show a marked difference between the evolution of the two inward currents when the membrane resting potential is increased by previous hyperpolarizations in a high range of values: the late current is decreased while the initial current remains constant. The decrease of the late current is suppressed by tetraethylammonium ions or in a potassium‐free medium. On detubulated fibres, the sodium current is never decreased by conditioning hyperpolarizations. 5. It is postulated that a fast transient potassium current, located in the bubular membrane, should develop contemporaneously with the sodium current. 6. The decay of the sodium inactivation is anaylsed on semilogarithmic plot: on normal fibres, it runs in two phases while on detubulated fibres, one phase only is found.
Number of glomeruli in normal and hypertrophied kidneys of mice and guinea‐pigs.
Authors: Bonvalet J P , Champion M , Courtalon A , Farman N , Vandewalle A , Wanstok F
Published: December 2014

1. In mice and guinea‐pigs, the number of glomeruli was counted in kidneys during normal growth and in hypertrophy induced by unilateral nephrectomy. 2. In mice, the number of glomeruli increased sharply during the first 2 weeks in life, and more slowly afterwards. Unilateral nephrectomy, when performed during this period of natural increase, induced the formation of supplementary nephrons in the contralateral kidney. 3. In guinea‐pigs, the number of glomeruli was almost complete at birth. No evidence of a supplementary increase in the number of nephrons was found in hypertrophied kidneys following unilateral nephrectomy. 4. These results, together wit previous data obtained in the rat, suggest that the ability to induce new nephrons after unilateral nephrectomy in different species would depend more on the state of kidney maturity at birth than on differences in the renal mechanisms which lead to hypertrophy.
Suppression of rat stomach histidine decarboxylase activity by histamine: H2‐receptor‐mediated feed‐back
Authors: Håkanson R. , Larsson L.-I. , Liedberg G. , Rehfeld J. F. , Sundler F.
Published: December 2014

1. Gastrin activates rat stomach histidine decarboxylase. Exogenous histamine suppressed the basal enzyme activity in unoperated, in nephrectomized, in vagally denervated and in antrectomized rats, and counteracted the pentagastrin‐induced enzyme activation in unoperated rats.

2. Kinetic analysis of enzyme‐catalysed histidine decarboxylation in extracts from untreated vagotomized and from histamine‐treated vagotomized rats showed that the histamine‐induced suppression of histidine decarboxylase activity probably reflects a reduced enzyme concentration. Moreover, the enzyme half‐life in vagotomized rats after treatment with histamine was shorter than the half‐life observed after inhibition of enzyme synthesis. These observations suggest that administration of histamine not only inhibits enzyme synthesis but also causes an accelerated rate of elimination of histidine decarboxylase.

3. Intravenous infusion of histamine caused marked displacement of the pentagastrin dose—response curve, in a manner suggesting a reduced sensitivity to pentagastrin.

4. After H2‐receptor blockade, but not after H1‐receptor blockade, histamine was less effective in suppressing the enzyme activity. Furthermore, H2‐receptor blockade augmented the pentagastrin‐induced enzyme activation.

5. The results suggest that histamine (via H2‐receptors) reduces the sensitivity of the histamine‐storing cells to gastrin and that H2‐receptor blockade induces the opposite effects.

6. We propose that the histamine‐storing cells in the rat stomach are endowed with H2‐receptors and that exogenous histamine is capable of acting directly on the histamine cells. This may reflect a physiological control mechanism whereby mobilized endogenous histamine modifies its own synthesis and release.
Transepithelial sodium transport and carbon dioxide production by the toad urinary bladder in the absence of serosal sodium.
Authors: Macknight A D , McLaughlin C W
Published: December 2014

1. The production of CO2 in relation to sodium transport by toad urinary bladder has been examined in the absence of sodium from the serosal medium. 2. Replacement of serosal sodium by choline increased CO2 production without stimulating short‐circuit current. Replacement of serosal medium by Tris did not have this effect. 3. With serosal sodium Ringer replaced by Tris Ringer, the ratio of sodium transported to CO2 produced was not altered significantly. 4. The results therefore suggest that there is no important recycling of sodium between the serosal medium and the transporting epithelial cells.
Close relation between TEA responses and Ca‐dependent membrane phenomena of four identified leech neurones
Authors: Kleinhaus Anna L. , Prichard James W.
Published: December 2014

1. Tetraethylammonium chloride (TEA) was applied to four kinds of identified neurones in leech segmental ganglia, namely, the sensory cells responding to touch (T), pressure (P) and noxious (N) stimuli and the Retzius cell (R).

2. TEA prolonged the action potentials of these cells to characteristically different degrees, in the order R > N > P > T, regardless of exposure time. This result was the same whether TEA was presented to the whole ganglion via the bathing fluid or injected iontophoretically into the soma of the cell under study.

3. TEA in Na‐free solution caused the behaviour of the N cell membrane to be dominated by a Ca‐dependent, Mn‐blockable event identical in every respect except smaller size to the previously described behaviour of the R cell under the same conditions. The P cell displayed a still smaller event of the same kind, but none was detectable in the T cell.

4. In the absence of both TEA and Na, when Ca was the only extra‐cellular cation available to carry current, active membrane responses to depolarization were present in the R cell (previous study) and the N cell; such responses were minimal in the P cell and absent from the T cell.

5. Differences among the four cells in density of a divalent cation conductance mechanism are the simplest explanation for these observations, though a more complex explanation based on multiple, pharmacologically distinct K conductances is not excluded by our data.
Nasal field loss in cats reared with convergent squint: behavioural studies.
Authors: Ikeda H , Jacobson S G
Published: December 2014

1. The extent of the monocular visual field in cats reared with convergent squint in one eye was determined by a behavioural perimetry technique. 2. Significant reduction in the extent of the visual field was found in the squinting eyes. 3. The visual field defect is a graded one, located mainly in the nasal field, but in some cats extending into the temporal visual field. The defect includes a zone of absolute loss of response to stimuli at the extreme nasal field, adjacent areas of partial response and areas of 100% response in the periphery of the temporal field. 4. A direct relationship was found between the angle of horizontal deviation of the squinting eye and the amount of visual field loss: i.e. the larger the angle of squint, the greater the loss of nasal field. 5. It is suggested that the process leading to a loss in nasal visual field is independent of the loss of visual acuity in squinting cats, since the latter is not related to the angle of squint. 6. The significant loss in nasal visual field found by behavioural experiments in cats reared with a convergent squint thus correlates with comparable deficits found in the physiology and morphology of the lateral geniculate nucleus (Ikeda, Plant & Tremain, 1977), although the behaviourally determined loss of nasal field is greater than would be expected from the study of the response of the LGN neurones.
Regulation of amylase release from dispersed pancreatic acinar cells.
Authors: Gardner J D , Jackson M J
Published: December 2014

1. A study has been made of factors influencing release of amylase from dispersed pancreatic acinar cells. 2. In the basal, unstimulated, condition cells released 2‐3% of the total amylase present in 30 min. 3. The rate of amylase release was stimulated 50‐70% by C‐terminal octapeptide of cholecystokinin (CCK‐OP, maximally effective concentration, 3 X 10(‐10) M); carbamylcholine (maximally effective concentration, 10(‐5 M); secretin (maximally effective concentration greater than 10(‐6) M); vasoactive intestinal peptide (VIP, maximally effective concentration, 10(‐8) M); and adenosine 3':5' monophosphate (cyclic AMP) and guanosine 3':5' monophosphate (cyclic GMP) as well as their dibutyryl derivatives (maximally effective concentrations, 10(‐3) M). 4. The responses to CCK‐OP or carbamylcholine were potentiated by secretin, VIP or dibutyryl cyclic AMP. 5. The responses to secretin or VIP were potentiated by CCK‐OP, carbamylcholine, or dibutyryl cyclic GMP. 6. There appear to be two pathways for the regulation of amylase release from pancreatic acinar cells: one pathway can be stimulated by cholecystokinin or cholinergic agonists, and the response to these stimuli is mediated by cyclic GMP; the other pathway can be stimulated by secretin or VIP, and the response to these stimuli is mediated by cyclic AMP.
Mechanism of milk secretion: milk composition in relation to potential difference across the mammary epithelium
Authors: Peaker M.
Published: December 2014

1. In conscious lactating goats a significant correlation was found between blood—milk potential difference (p.d.) and milk [lactose] such that in goats with a lower milk [lactose], milk was more negative with respect to blood.

2. When mannose was substituted for glucose in the substrate mixture of isolated perfused goat mammary glands, milk yield and milk [lactose] fell while milk [Na] and [K] increased; in parallel experiments the blood—milk p.d. changed such that milk became more negative with respect to blood. These changes were reversed following the addition of glucose.

3. When milk was made hypertonic by the addition of hyperosmotic sucrose or lactose solutions, water entered milk osmotically and milk became electrically less negative or even positive with respect to blood in goats, cows and guinea‐pigs.

4. No effect on p.d. was apparent following the addition of isosmotic sucrose to milk in goats.

5. When milk was held in the teat of goats by a pneumatic cuff around the base of the teat, no effect on p.d. was apparent when hyperosmotic sucrose was introduced into this teat pouch.

6. It is suggested that waterflow‐induced potentials (the streaming potential and the transport number effect) can be induced across the mammary epithelium.

7. In goats exogenous oxytocin lowered milk [lactose] and blood—milk p.d. became less negative with respect to blood.

8. In non‐lactating and mastitic glands of goats the blood—milk p.d. was within 0·5‐2·5 mV of zero.

9. The effects of oxytocin, and the low p.d. in non‐lactating and mastitic glands, are compatible with the view that in such circumstances there is a paracellular pathway across the mammary epithelium which partially short‐circuits the two sides.

10. It is suggested that, with water being drawn osmotically into milk to dilute newly formed lactose, waterflow‐induced potentials may be responsible for establishing the normal p.d. across the apical membrane of the secretary cell, thereby keeping milk [K] and [Na] lower than in intracellular fluid.
Dorsal horn cells that respond to stimulation of distant dorsal roots (cat)
Authors: Devor M. , Merrill E. G. , Wall P. D.
Published: December 2014

Experiments were carried out to find if there were post‐synaptic effects produced by impulses in the long ranging primary afferents, which had been shown by Wall & Werman (1976) to extend from upper lumbar dorsal roots to the sacral segments. Dorsal rootlets were stimulated in decerebrate low‐spinal adult cats.

1. The dorsal root potential and ventral root reflex were recorded on S1 root filaments, in response to stimulation of dorsal rootlets extending from L1 to S1. With increasing distance between stimulating and recording segments, these potentials became smaller and more delayed. In two animals, there was no response at S1 to stimulation of L1 and L2 dorsal roots.

2. In all animals, stimulation of L3 or L4 dorsal roots produced cell responses in dorsal horn segments L7 or S1. The density of such cells was variable, from animal to animal. Responding cells were mainly concentrated laterally in the dorsal horn.

3. The latency and response variability of L7‐S1, dorsal horn cells to L3‐L4 stimulation was consistent with at least some of them being fired monosynaptically.

4. Cells that respond to stimulation of one distant rootlet respond to many closer rootlets as well.

5. The receptive fields of L7‐S1 dorsal horn cells, responsive to stimulation of L3‐L4 rootlets, were typical of those generally found in the L7‐S1 segments, and were at some distance from the L4 dermatome. Only twenty cells had receptive fields which extended into the dermatome of the rootlets stimulated.

6. It was established that some L4 cells respond to S1 dorsal root stimulation, just as the main study had shown that S1 responds to L4.

7. It is concluded that substantial numbers of dorsal horn cells, including cells with many types of cutaneous receptive field, respond to two classes of synaptic in‐put: one effective in firing the cell upon natural cutaneous stimulation, and one relatively ineffective, capable of driving the cell only when stimulated electrically and thus carrying a synchronous volley from a number of highly convergent axons. The contribution of this secondary afferent channel to normal and pathological cord physiology has now to be determined.
Effect of changing the composition of the bathing solution upon the isometric tension—pCa relationship in bundles of crustacean myofibrils
Authors: Ashley C. C. , Moisescu D. G.
Published: December 2014

1. The relative isometric tension—pCa relationship has been determined for isolated bundles of barnacle myofibrils under a variety of ionic conditions using [Ca2+]‐buffered solutions which also contained an ATP regenerating system (creatine phosphate and creatine kinase).

2. The results are in better agreement with the ‘consecutive’ scheme of reaction rather than with the ‘independent’ alternative (Ashley & Moisescu, 1972) for the co‐operative action of two Ca2+ ions in the process of tension activation in crustacean skeletal muscle.

3. Variations in the pH of the activating solutions did have a marked effect on the relative tension—Ca curve, although no effect was observed on the absolute maximum value for isometric tension. A shift in pH by 0·5 u. in the range 6·6‐7·6 shifted the Ca2+—activation curve by 0·5 log u. towards lower free Ca2+ concentrations.

4. Changes in the free Mg2+ concentration of the activating solutions in the millimolar range produced a pronounced shift of the relative tension—pCa curve along the pCa axis. Increasing [Mg2+] from 1 to 5 m
M shifted the curve by about 0·7 log u. to higher free Ca2+ concentrations, without significantly modifying its steepness.

5. Changes in the MgATP concentration of the activating solutions in the range of 1‐13 m
M had no significant effect on the relative tension—pCa relationship.

6. Varying the K+ concentration in the activating solutions was also observed to have a marked effect upon the tension—pCa relationship in barnacle. An increase in the K+ concentration from 90 to 170 m
M shifted the curve by some 0·6 log u. towards higher free Ca2+ concentrations.

7. Cooling the standard activating solutions from room temperature to +4° C made no apparent difference to the relative tension—pCa relationship, but decreased significantly the absolute tension responses.

8. The results presented show that tonicity by itself has a marked effect upon the absolute steady‐state tension levels in isolated bundles of myofibrils.

9. Maximum isometric tension in this preparation was not simply related to ionic strength, or to the monovalent cation concentration, but it depended, as well, upon the anionic composition of the activating solution. In addition, a change in ionic strength of 25 m
M over the range of 245‐270 m
M did not appear to modify the relative tension—pCa relationship.

10. The effect of the physiologically occurring cations H+, K+, Mg2+ upon the relative isometric tension—pCa relationship can be accounted for on the basis of a model of competitive inhibition between these cations and Ca2+ for the functional unit for tension. This inhibitory effect appears to involve at least one H+, one Mg2+ and two K+ per each Ca2+ ion participating in the activation process of the functional unit for tension.
Excitation—contraction coupling in the smooth muscle cells of the rabbit main pulmonary artery
Authors: Casteels R. , Kitamura K. , Kuriyama H. , Suzuki H.
Published: December 2014

1. Increasing the external K concentration depolarizes the smooth muscle cells of the main pulmonary artery, and this depolarization reaches a maximal slope of 58 mV for a tenfold change of [K]o. The threshold depolarization for inducing contraction is at 4 mV and the maximal contraction is reached at a [K]o of 58 m
M.

2. Noradrenaline concentrations between 2 × 10−8
M and 10−7
M induce tension without depolarizing the cells, but at higher concentrations noradrenaline not only elicits a large tension response but also depolarizes the cells in a dose‐dependent way.

3. The effect of noradrenaline on the pulmonary artery is appreciably modified by substituting sucrose for NaCl: the cells are slightly hyperpolarized and the tension response is very much reduced.

4. By studying the tension response to noradrenaline in other experimental conditions which cause a small hyperpolarization of the cells, such as 5 m
M‐[Ca]o, 2.9 m
M‐[K]o or a small depolarization, such as 11·9 m
M‐[K]o, it was found that a slight modification of the membrane potential can exert an important effect on the noradrenaline response.

5. A simultaneous decrease of [Ca]o and [Na]o reduces the tension response to all noradrenaline concentrations. It was found that a reduction of [Na]o exerts a more depressing effect than a reduction of [Ca]o. In interpreting these results we have to take into account changes of the membrane potential, of availability of Ca, and some competition between external Ca and Na.

6. A study of the effect of different concentrations of noradrenaline in Krebs solutions and Ca‐free solution has shown that concentrations up to 2·5 × 10−7
M elicit contraction by increasing the Ca influx, while higher concentrations also induce a release of cellular Ca.

7. Caffeine depolarizes the cells and reduces the membrane resistance. It modifies the K, Cl and Ca fluxes in the same way as noradrenaline, but it suppresses the mechanical response induced by noradrenaline.
Localization of calcium channels in Paramecium caudatum.
Authors: Dunlap K
Published: December 2014

1. Electrical recordings from Paramecium caudatum were made after removal of the cilia with chloral hydrate and during ciliary regrowth to study the electrical properties of that portion of the surface membrane enclosing the ciliary axoneme. 2. Removal of the somatic cilia (a 50% reduction in membrane surface area) results in an almost complete elimination of the regenerative Ca response, all‐or‐none Ba2+ spike, and delayed rectification. 3. A twofold increase in input resistance resulted from the 50% reduction in membrane surface area. 4. The electrical properties remained unchanged, despite prolonged exposure to the chloral hydrate, until the cilia were mechanically removed. 5. Restoration of the Ca response accompanied ciliary regrowth, so that complete excitability returns when the cilia regain their original lengths. 6. It is concluded that the voltage‐sensitive Ca channels are localized to that portion of surface membrane surrounding the cilia. 7. Measurements of membrane constants before and after deciliation and estimations of the cable constants of a single cilium suggest that the cilia of Paramecium may be fully isopotential along their length and with the major cell compartment.
The relationship between histamine secretion and 45calcium‐uptake by mast cells
Authors: Foreman J. C. , Hallett M. B. , Mongar J. L.
Published: December 2014

1. Unstimulated mast cells from the peritoneal cavity of the rat take up 45Ca: the initial phase of rapid uptake being complete after 1 min incubation of the cells with the isotope. Stimulation of the mast cells with an antigen‐antibody reaction, dextran or concanavalin A induces an increase in the uptake of 45Ca which is accompanied by a release of granular material: this increase in 45Ca uptake is also complete in 1 min. The majority of the stimulated 45Ca uptake cannot be explained in terms of binding of Ca to released granular material, or to an enlargement in either the extracellular compartment or the cell surface area.

2. The magnitude of the increase in 45Ca uptake caused by stimulating the mast cells increases when the degree of histamine secretion increases.

3. The increased 45Ca uptake induced by stimulation of the mast cells and the degree of histamine secretion are both dependent on extracellular H ion concentration. Changes of pH cause similar changes in 45Ca uptake and secretion with maxima at pH 7.5.

4. Two thirds of the 45Ca uptake induced by an antigen‐antibody reaction or by the Ca ionophore A 23187 is unaffected by inhibiting glycolysis and oxidative phosphorylation. Histamine secretion on the other hand is practically abolished by this metabolic inhibition. Thus, 45Ca uptake proceeds in the absence of the discharge of granules.

5. Dibutyryl cyclic AMP or theophylline inhibit both the increase in 45Ca uptake and the histamine secretion caused by stimulating mast cells with an antigen‐antibody reaction. Cyclic AMP, cyclic GMP and dibutyryl cyclic GMP have no effect on uptake or secretion.

6. The Ca ionophore, A 23187, induces uptake of 45Ca and histamine secretion, neither effect being inhibited by either dibutyryl cyclic AMP or theophylline.

7. Phosphatidyl serine increases both 45Ca uptake and the histamine release induced by an antigen‐antibody reaction, dextran or concanavalin A.
The interaction of monovalent cations with the sodium pump of low‐potassium goat erythrocytes
Authors: Cavieres J. D. , Ellory J. C.
Published: December 2014

1. The activation by Na ions and the effect of the anti‐L antibody on the sodium pump of low‐potassium type (LK) erythrocytes, have been studied by measuring ouabain‐sensitive ATPase activity of red cell membranes of LK goats. The experimental data were first corrected for incomplete occupation of the external K sites of the pump, using a saturation function obtained from influx experiments.

2. Double‐reciprocal plots of the corrected rates against Na concentration at various fixed K concentrations, yield a pattern of competitive K inhibition when it is assumed that three equivalent sodium sites take part in the internal activation of LK‐(Na+K)‐ATPase. The dissociation constant of Na at each site (Km) lies between 10 and 20 m
M and that of K as competitive inhibitor (Ki), between 1.5 and 4.5 m
M.

3. The maximal rate of hydrolysis of LK goat (Na + K)‐ATPase is not different from those usually obtained with the high‐potassium type (HK) red cell enzyme. Then, the low pumping rate of LK erythrocytes in physiological conditions is only reflecting the poor Na affinity, both absolute and relative, at the internal Na sites of their sodium pumps.

4. The stimulation of the ouabain‐sensitive ATPase activity by sensitization of the membranes with anti‐L serum, is mediated by a threefold reduction of the Km/Ki ratio at each site. Km decreases by a factor of 10, but there is also a smaller diminution of Ki. The maximal rate of hydrolysis, however, is unchanged by the anti‐L treatment. The least‐squares fitting of the pooled data by the rate equation, converges better with less than three and more than two equivalent sodium sites.

5. The affinity sequence at two external K sites of the LK goat erythrocyte sodium pump, determined in the presence of 100 m
M external Na, is Rb > K > Cs. It is obtained from the concentration dependence in influx experiments, and is the same as reported for human red cells.

6. Cubic‐root Dixon plots of the corrected ouabain‐sensitive ATPase activity against the concentration of K and its congeners, show the sequence Tl > K > Rb > Na > Cs for the affinities at the internal cation sites of the LK sodium pump. Anti‐L treatment decreases the relative magnitude of Na and Cs selectivities, it being not certain whether a Rb—Na transition then occurs.

7. The results are discussed in terms of possible mechanisms whereby the sodium pump of LK and HK red cells may adjust the properties of their cation sites upon translocation of monovalent cations.
Sodium chloride transport across the chicken coprodeum. Basic characteristics and dependence on sodium chloride intake
Authors: Choshniak I. , Munck B. G. , Skadhauge E.
Published: December 2014

1. The transport characteristics of the chicken coprodeum have been examined in vitro using the isolated mucosa. The short‐circuit current (Isc), the transepithelial electrical potential difference (p.d.), the unidirectional transmural fluxes (Jms, Jsm) of sodium and chloride measured in the short‐circuited state, and the unidirectional influx of sodium and chloride across the brush border membrane measured under open‐circuit conditions have been studied. The effect of the sodium chloride contents of the diet on these parameters have been investigated.

2. The isolated mucosa depends functionally on the presence of glucose in the incubation media. This dependence reflects the need of glucose as a fuel. There is no indication of coupling between transport of sugars and sodium across the brush border membrane. For preparations from chickens on a low sodium diet a very high and stable Isc can quantitatively be accounted for by the net transport of sodium. Influx of sodium across the brush border membrane is not significantly different from the net flux of sodium. By feeding the chickens a high sodium diet the Isc is reduced by more than 95%, the net transport of sodium is abolished, and the transepithelial electrical conductance is reduced by more than 50%.

3. Both unidirectional transepithelial fluxes of chloride, and the serosa to mucosa flux of sodium appear to proceed through a paracellular shunt.

4. Under the conditions of the low sodium diet the paracellular pathway appears to be anion selective. Whereas, under the conditions of the high sodium regimen the paracellular route appears to be cation selective. After adaptation to a high sodium diet the influx of sodium across the brush border membrane is only moderately reduced. Consequently the decisive event in the adaptation must be localized elsewhere.
The natural discharges of Purkinje cells in paravermal regions of lobules V and VI of the monkey's cerebellum
Authors: Harvey R. J. , Porter R. , Rawson J. A.
Published: December 2014

1. Conscious monkeys were trained with food rewards to perform movement tasks with the left hand and to accept manipulation of the joints and muscles and natural non‐noxious stimulation of the skin of both forelimbs.

2. Recordings were made from 230 Purkinje cells situated in the paravermal region of lobules V and VI or immediately adjacent folia of the left cerebellum in a region from 2 to 7 mm from the mid line. These neurones were all in a zone which was demonstrated to receive inputs from the ipsilateral hand and which is known to receive projections, via the pontine nuclei from the ‘arm area’ of motor cortex in the right hemisphere.

3. Modulation of the natural activity of 182 of these 230 Purkinje cells (79%) occurred in a reproducible manner in temporal association, each with a particular phase of the self‐paced movement tasks performed by the animal using the ipsilateral arm and hand. The patterns of modulation of Purkinje cell firing in this limited zone of cerebellar cortex could be classified into one of four groups, and each cell's discharge was associated with a particular aspect of movement such as general arm flexion, shoulder retraction, elbow extension or elbow flexion whenever it occurred.

4. The cells were spontaneously active at rest. Most commonly, marked accelerations of the discharge were related to one direction of the particular aspect of movement and a reduction of activity or even total silence accompanied movement in the opposite direction.

5. Variation of the amount of discharge demonstrated during a movement performance with which this discharge was characteristically associated could be related to the range of the movement or its duration, more activity being characteristic of more prolonged movement performance through larger angles of joint displacement.

6. Both simple spikes and complex spikes of some cells showed characteristic modulation of their activity during the monkey's self‐initiated movements. Cells whose simple spikes did not change in frequency during the movement task, also showed no modification of complex spike discharge.

7. Of the 182 neurones whose discharges changed during active movement performance, 105 (roughly 60%) were demonstrated to be in receipt of an input from peripheral receptors in the hand which could be activated by brisk tapping of the skin or brushing of hairs. In contrast, none of the Purkinje cells whose discharges were unchanged during arm movements could be demonstrated to receive such an input.

8. Movement of joints through their full range and prodding of muscles were completely ineffective stimuli for causing changes in Purkinje cell firing in this zone of the cerebellar cortex while the animal was passive and relaxed. Imposed perturbations of movement performance injected unexpectedly during the execution of a movement task were also ineffective in modifying the discharge of these Purkinje cells in relation to the task.
Properties of isolated adult rat muscle fibres maintained in tissue culture.
Authors: Bekoff A , Betz W
Published: December 2014

1. Adult rat skeletal muscles were dissociated by collagenase treatment and trituration, and the isolated muscle fibres were maintained in vitro for 2‐3 weeks. At various stages, the fibres were examined physiologically and morphologically. 2. The isolated fibres underwent some changes characteristic of muscle denervated in vivo. For instance, input resistance increased and extrajunctional acetylcholine (ACh) receptors appeared. In addition, the beginning stages of apparent muscle fibre fragmentation were observed. 3. In other respects, the cultured isolated fibres behaved differently than in vivo denervated fibres. Fibrillation developed only occasionally in vitro. The onset of ACh supersensitivity was slower (6 days) than after denervation in vivo (2‐3 days). Some fibres developed localized regions of destriation, which apparently was due to loss of in‐register alignment of myofibrils.
Cation movements in normal and short‐term denervated rat fast twitch muscle
Authors: Robbins Norman
Published: December 2014

1. The earliest known change in rat fast muscle following denervation is a fall in resting membrane potential unaccompanied by change in membrane resistance. The present study tested the hypothesis that increased Na permeability (PNa) accounted for this early depolarization.

2. In all experiments, rat extensor digitorum longus muscles were studied in vitro at 25° C. Li uptake in vitro, used as a measure of PNa, was greater in 1‐ and 2‐day denervated muscles (and in 2‐day denervated diaphragm) than in paired controls.

3. The extra Li taken up by denervated muscle was not sequestered in an extracellular or freely exchangeable compartment, nor was it irreversibly bound.

4. Measurements of resting membrane potential and of internal Na, K, and Li in Krebs solution before and 2 hr after replacement of NaCl by LiCl, were used to compute the ratios PNa/PK and PLi/PK for normal or denervated muscles. PNa and PLi were similar relative to PK within each class of muscle.

5. Both PNa/PK and PLi/PK ratios were elevated more than twofold in denervated muscle, as were most estimates of relative PLi approximated by the flux equation.

6. These data, and measurement of resting membrane potential of normal muscle in 1 m
M external K‐Krebs solution, support the view that an electrogenic Na—K pump does not substantially contribute to this potential of normal or denervated muscle, and that the early depolarization after denervation results from increased PNa.

7. The Na—K pump of denervated muscle was as sensitive to ouabain as normal muscle. An effect of ouabain on PNa may explain previously noted differential effects of ouabain on normal and denervated muscle.
The effect of calcium ions and temperature on the binomial parameters that control acetylcholine release by a nerve impulse at amphibian neuromuscular synapses
Authors: Bennett M. R. , Fisher C. , Florin T. , Quine M. , Robinson J.
Published: December 2014

1. A study has been made of the effects of changing the external calcium concentration, [Ca]o, and the temperature on both the number of quanta available for release by the nerve impulse (n) as well as the increase in release probability of a quantum p(t) during the release period (from 0 to T) following a nerve impulse at synapses in amphibian striated muscle.

2. When [Ca]o was increased in the low range from 0·25 to 0·4 m
M at 18 °C, the average quantal content of the e.p.p. (m̄) increased as the fourth power of [Ca]o and this was primarily due to a third power dependence of n on [Ca]o; the dissociation constants and power dependence of n on calcium determined in the [Ca]o range from 0·25 to 1·0 m
M were successfully used to predict the changes in size of the e.p.p. in the very high [Ca]o range from 1 to 10 m
M. When the temperature was increased from 7 to 18 °C in a [Ca]o of 0·6 m
M or 0·35 m
M, n increased with a Q10 of 2·5.

3. When [Ca]o was increased in the range from 0·25 to 1·0 m
M at 18 °C, the probability that a quantum initially available for release is released during the release period (p(T)) was very sensitive to [Ca]o, increasing as the third power of [Ca]o and with a dissociation constant of 0·13 m
M. When the temperature was increased from 7 to 18 °C in a [Ca]o of 0·6 m
M or 0·35 m
M, p(T) decreased.

4. The histograms of latencies of individual quanta following a nerve impulse was very temperature dependent: the time to peak of the histograms (i.e. the interval in which most quanta fell) had a Q10 of over 4 as did the time constant of decline of the histograms in the temperature range from 7 to 18 °C.

5. The average number of quanta released up to time t during the release period following a nerve impulse, namely np(t), was well described by a stochastic process in which p(t) was determined by two reactions; one of these reactions released available quanta from the nerve terminal whilst the other made some of the available quanta unavailable for release by the nerve impulse.
Synaptic excitation and inhibition resulting from direct action of acetylcholine on two types of chemoreceptors on individual amphibian parasympathetic neurones
Authors: Hartzell H. Criss , Kuffler Stephen W. , Stickgold Robert , Yoshikami Doju
Published: December 2014

1. Synaptic transmission was studied in visually identified parasympathetic ganglion cells that modulate the heart beat of the mudpuppy Necturus maculosus).

2. The brief pulse of acetylcholine (ACh) released from terminals of the vagus nerve after each impulse can produce two distinct post‐synaptic responses in individual principal cells of the ganglion: (i) within a milli‐second of release, ACh generates a rapid and strong excitatory post‐synaptic potential (e.p.s.p.) that normally initiates a post‐synaptic impulse; (ii) this excitation is usually followed by a slow hyperpolarizing inhibitory post‐synaptic potential (i.p.s.p.) that lasts for several seconds. The magnitude and time course of the i.p.s.p. depends on the frequency and number of vagal stimuli. When the hydrolysis of ACh is inhibited by prostigmine, a train of nerve stimuli may be followed by an i.p.s.p. lasting half a minute or longer.

3. The rapid e.p.s.p. and slow i.p.s.p. result from the direct action of ACh on two different types of chemoreceptors in the post‐synaptic membrane of the principal cell. The e.p.s.p. can be preferentially blocked by the nicotinic antagonist dihydro‐β‐erythroidine (5 × 10−7
M), while the i.p.s.p. is selectively blocked by the muscarinic antagonist atropine (5 × 10−9
M).

4. Potentials resembling nerve‐evoked e.p.s.p.s and i.p.s.p.s can be produced by iontophoretic release of ACh from micropipettes onto the post‐synaptic membrane. Application of the muscarinic agonist bethanechol generates exclusively inhibitory responses.

5. The reversal potential for the i.p.s.p. is about ‐105 mV, which is approximately the equilibrium potential for potassium (EK). When the external K+ concentration is altered, the reversal potential for inhibition is shifted to the new value of EK as expected from the Nernst equation. Changes in the external Na+ and Cl− concentrations have no appreciable effect on the reversal potential. Thus, the i.p.s.p. is the result of a conductance increase for K+.

6. The conductance change producing the i.p.s.p. is voltage sensitive. When the membrane potential is shifted from ‐40 to ‐60 mV, the i.p.s.p becomes larger and longer. Beyond ‐60 mV the inhibitory response decreases in proportion to the driving force on K+ without any further change in time course.

7. The inhibitory response produced by an iontophoretically applied pulse of bethanechol has a delayed onset of about 150 msec at 24 °C. The early portion of this response, including the delay, is proportional to t3, where t is time. The proportionality factor (the apparent rate constant) decreases elevenfold when the temperature is lowered by 10 °C. This suggests that a multi‐step process is involved in the activation of the conductance increase that leads to the inhibitory response. Inhibitory responses with similar kinetics were produced in heart muscles of the mudpuppy upon application of ACh.
Passive signal propagation and membrane properties in median photoreceptors of the giant barnacle
Authors: Hudspeth A. J. , Poo Mu Ming , Stuart Ann E.
Published: December 2014

1. The light‐induced electrical responses of barnacle photoreceptors spread decrementally along the cells' axons. The decay of the depolarizing and hyperpolarizing components of the visual signal was studied by recording intracellularly from single receptor axons of the median ocellus of the giant barnacle.

2. The resistance of the photoreceptor neurone decreases markedly when the cell is depolarized with respect to its dark resting potential of ‐60 mV. This rectification results in differential attenuation of the depolarizing and hyperpolarizing components of the visual signal as they spread down the axon. Consequently, the visual signal entering the synaptic region is conspicuously distorted.

3. Bathing the photoreceptor axons in sodium‐free or calcium‐free saline or in isotonic sucrose does not significantly affect the spread of the visual signal to the terminals. Thus the signal is not amplified by an ionic mechanism along the axon.

4. Membrane characteristics of the photoreceptor for hyperpolarizing voltage changes were estimated from (a) the ratio of the amplitudes of the visual signals recorded simultaneously in the axon and in the soma, (b) the time constant, and (c) the input resistance of the cell. All three independent measurements are consistent with a length constant 1 to 2 times the total length of the cell (λ = 10‐18 mm) and an unusually high membrane resistivity of about 300 kΩ cm2. This resistivity enables the receptor potential to spread passively to the terminal region.

5. Electron microscopic examination of receptor axons reveals an investment of glial lamellae, but demonstrates neither unusual structures which would lead to a high apparent membrane resistivity, nor junctions between cells which would seal off the extracellular space. Thus the observed high resistivity appears to be an intrinsic property of the receptor membrane.