bluuebunny/crossref_metadata_2025_split huggingface dataset:
Slow changes in potassium permeability in skeletal muscle
Authors: Adrian R. H. , Chandler W. K. , Hodgkin A. L. 
Published: December 2014

1. Voltage clamp experiments on sartorius muscle fibres at 3° C showed that the potassium current is divisible into three components, namely:(a) Current in the delayed rectifier channel, which reached a maximum in about 0·1 sec at −30 mV, and declined with a time constant of about 4 msec when the fibre was repolarized to −100 mV; this component had an approximately linear instantaneous current—voltage relation and an equilibrium potential E1 at 10–15 mV positive to the resting potential.(b) A slow component which reached a maximum in about 3 sec at −30 mV, and declined with a time constant of about 0·5 sec when the fibre was repolarized to −100 mV; this component had an approximately linear instantaneous current—voltage relation and a mean equilibrium potential E2 at ‒83 mV in fibres where E1 averaged −75 mV.(c) Current in the inward rectifier channel which decreased with a time constant of about 0·25 sec when the fibre was hyperpolarized to −150 mV. This component had an equilibrium potential close to the resting potential and an instantaneous current—voltage relation which was that of an inward rectifier.2. The general characteristics of the late after‐potential in muscles in hypertonic solutions at 3° C are consistent with those of the slow conductance change. The sign of the late after‐potentials was reversed by depolarizing below −80 mV.3. The decline of current during a maintained hyperpolarization cannot be attributed solely to a decrease in tubular potassium concentration, since there may be a large decrease in current without much alteration of equilibrium potential. The negative slope conductance often seen at −150 mV is also difficult to reconcile with the tubular depletion hypothesis.4. Replacement of 10 m
M‐K by 10 m
M‐Rb abolished inward rectification but had less effect on the fast and slow components of the potassium conductance.
Gallamine thiethiodide (Flaxedil) and cat retinal ganglion cell responses
Authors: Enroth‐Cugell Christina , Pinto L. H. 
Published: December 2014

1. Repeated flashes of diffuse light were presented to the cat's eye over long periods of time (hours) while the mixed ganglion cell response was recorded from single axons in the optic tract. This was done for cats receiving gallamine triethiodide intravenously and for cats who did not receive the drug.2. All responses were transformed into instantaneous pulse density tracings. Such tracings from control and gallamine cells were compared to observe possible effects of gallamine: (a) the shape (time course) did not change during gallamine administration; (b) maximum firing frequency, total number of spikes and latency was measured for both the on‐ and the off‐component on the pulse density tracings and plotted versus time. Statistical methods failed to reveal any difference between the manner in which these response features of control cells and of gallamine cells varied with time.
On the mode of action of ACTH on the isolated perfused adrenal gland
Authors: Jaanus Siret D. , Rosenstein M. J. , Rubin R. P. 
Published: December 2014

1. Isolated cat adrenal glands were perfused with Locke solution, and the corticosteroid outputs in response to adrenocorticotrophin (ACTH) were studied.2. Steroid outputs varied with the ACTH concentration, as well as with the duration of exposure to a given ACTH concentration.3. Omission of calcium from the perfusion medium markedly depressed ACTH‐evoked steroid release. The steroid output was directly related to the extracellular calcium concentration up to 0·5 m
M.4. During a constant exposure to ACTH, steroid output was maintained for at least 2‐3 hr, provided that calcium was present in the perfusion medium.5. Strontium, but not barium or magnesium, replaced calcium in maintaining the secretory response to ACTH.6. Magnesium depressed ACTH‐evoked secretion in the presence of calcium, and this depression of secretion was antagonized by increasing the calcium concentration.7. Prolonged perfusion with sodium‐free or potassium‐free solutions did not markedly inhibit steroid output in response to ACTH. Excess potassium (56 m
M) did not produce a consistent or marked increase in spontaneous steroid output and did not affect the response to ACTH.8. The steroid content of adrenal glands perfused with Locke solution and exposed to ACTH was about 10% of the amount which was secreted. By contrast, adrenal glands perfused with calcium‐free media and exposed to ACTH contained much higher amounts of steroid, despite the negligible amount secreted.9. These data suggest that calcium plays a critical role in the mechanism of corticosteroid secretion from the adrenal cortex.
Effects of 0·9% saline infusion on urinary and renal tissue composition in the hydropaenic, normal and hydrated conscious rat
Authors: Atherton J. C. , Green R. , Thomas S. 
Published: December 2014

1. Changes in water and solute outputs of hydropaenic, normal and hydrated conscious rats were determined during intravenous infusion (0·2 ml./min) of isotonic (0·9%) saline for 4 hr; renal tissue composition was determined before, and after 1 or 2 hr, infusion.2. In normal and hydrated rats increased excretion of water and sodium was such that urinary output matched intravenous input from about 2 hr. In hydropaenic rats, the diuretic and natriuretic response was much reduced; a retention of infused saline, equivalent to 15% body weight, occurred over 4 hr.3. A considerable increase in urea output and clearance, and a smaller increase in potassium and ammonium outputs, occurred in all groups.4. The corticomedullary osmolal gradients characteristic of non‐diuretic rats were largely dissipated during saline infusion: by 1 hr in normal and hydrated rats, and by 2 hr in the hydropaenic group.5. These changes were ascribable mainly to an increase in tissue water content in all segments, particularly in the hydropaenic group; and to a profound decrease in urea content in all groups.6. Changes in tissue sodium content were smaller, and differed between segments and between the differently hydrated groups. A decrease in papillary content occurred in hydropaenic and normal groups and an increase in cortical and outer medullary content occurred in all groups.7. After 2 hr saline infusion, incomplete papillary—urinary osmotic equilibration was evident in all groups.8. These changes in medullary osmolality and in papillary—urinary osmotic equilibration preceded the maximal diuresis, and must contribute to the diuresis induced by saline infusion, as in water and osmotic diureses.
The dependence of the transmembrane salivary secretory potential on the external potassium and sodium concentration
Authors: Petersen O. H. 
Published: December 2014

1. The submandibular gland of the cat was perfused with equi‐osmolar Locke solutions of different cationic composition. The increase in acinar membrane potential (secretory potential), measured with a glass capillary micro‐electrode, was recorded after intra‐arterial injection of acetylcholine.2. When nearly all Na in the perfusion fluid was replaced by tetraethylammonium (TEA), the size of the secretory potentials was significantly (P < 0·001) greater than of those recorded during perfusion with normal Locke solution.3. When the K concentration in the TEA Locke solution was augmented, the size of the secretory potentials was greatly diminished. Thus at a [K]o of 4 m‐equiv/l. the size of the secretory potentials was 43·3 mV ± 2·5 (n = 19) but at a [K]o of 10 m‐equiv/l. the size was only 24·7 mV ± 2·0 (n = 13) and at a [K]o of 20 m‐equiv/l. the size of the secretory potentials was 12·0 mV ± 1·0 (n = 21). When the submandibular gland was perfused with a K‐free TEA Locke solution the size of the secretory potentials was 49·7 mV ± 2·2 (n = 17).4. The size of the secretory potentials recorded during perfusion with normal (Na) Locke solution increased significantly (P < 0·001) when K was omitted from the perfusion fluid. The decrease of the size with increasing [K]o was considerably less marked than that found during perfusion with TEA Locke solution. Increasing [K]o by a factor of 5 diminished the size of the secretory potentials recorded in Na Locke solution by a factor of 2, whereas the size of the secretory potentials recorded in TEA Locke solution, with the same changes in [K]o, diminished by a factor of 3·5.5. The results seem to indicate that the increase in acinar membrane potential obtained after stimulation of the gland is due to an enhanced permeability of the basal acinar cell membrane to K. However, it seems that the permeability to Na is also enhanced so that the outwardly directed K current is partly short‐circuited by an inward Na current.
Accessibility of heart water to pentoses
Authors: Fisher R. B. , Gilbert J. C. 
Published: December 2014

1. The raffinose space, the inulin space and the weight loss on compression of perfused rat hearts are indistinguishable in magnitude.2. The inulin space shows systematic variations from day to day and is also affected by the procedure used for removing surplus water from the perfused heart. It is therefore not safe to use a mean figure of extracellular space in permeability experiments.3. Perfusion of hearts with arabinose solutions alters the intracellular water content. These alterations can be accounted for if it is assumed that the arabinose which penetrates the cells is uniformly distributed in the cell water.4. By appropriate choice of pentose concentration and of time of perfusion it can be shown that all the estimated cell water is accessible to pentose.5. It is concluded that no detectable fraction of the extracellular water is inaccessible to inulin and that no detectable fraction of the intracellular water is inaccessible to pentose.
Properties of kallikrein‐containing granules isolated from the submaxillary gland of the guinea‐pig
Authors: Bhoola K. D. , Heap P. F. 
Published: December 2014

1. Granular fractions of high purity consisting of subcellular kallikrein‐ and amylase‐storing organelles have been isolated from homogenates of guinea‐pig submaxillary gland.2. The isolated kallikrein‐ and amylase‐containing granules closely resembled secretory granules observed in situ in serous acinar cells in intra‐granular appearance, size and histochemical reaction.3. The subcellular, histochemical and ultrastructural studies indicate that the serine protease, kallikrein, is like amylase an exocrine enzyme with a functional role in saliva.
The effect of changes in lung volume on the size and shape of alveoli
Authors: Forrest J. B. 
Published: December 2014

1. A technique is described by which living anaesthetized guinea‐pigs were artificially ventilated with a positive and negative pressure cycle, and rapidly frozen at the instant of cessation of ventilation at a preselected point on the respiratory cycle.2. The dimensions of alveoli and alveolar ducts were measured by histological morphometric methods, and related to the degree of lung inflation at the instant of freezing.3. The alveolar volume fraction increased from 0·52 at low lung volumes, up to 0·62 at lung volumes in the mid‐inflation range, then decreased to 0·51 at high lung volumes. The alveolar duct volumetric fraction remained constant at all lung volumes.4. The total volume of alveoli increased linearly with increase in lung volume. The total alveolar duct volume increased little until the lungs were 40% inflated, above which it increased steeply.5. The total number of alveoli was linearly related to the body weight.6. The total alveolar surface area increased steeply between lungs of low lung volume and those which were up to 50% inflated, above which the increase levelled off. The absolute values of total alveolar surface depended on the body weight as well as the degree of lung inflation.7. The mean alveolar duct diameter was 40% greater, and the mean alveolar mouth diameter 35% greater in lungs which were fully inflated than in lungs which were nearly collapsed. The average geometrical shape of alveoli was not related to the degree of lung inflation.8. The harmonic mean thickness of the air—blood barrier was 33% less in lungs which were fully inflated than in lungs which were nearly collapsed. The alveolar surface membrane was smooth whether the lungs were fully inflated or collapsed.
Modification of transmitter release by ions which prolong the presynaptic action potential
Authors: Benoit P. R. , Mambrini J. 
Published: December 2014

1. The action of ions which increase the nerve spike duration at Ranvier's node has been studied at the neuromuscular junction of the frog.The duration of the presynaptic action potential is increased by UO2, Ni, Nz and TEA ions.2. The release of transmitter after a nerve impulse is delayed and prolonged in the presence of the four ions, but the amount of evoked transmitter release estimated from the mean quantal content of e.p.p. is increased only by UO22+ and TEA. Both Ni2+ and Zn2+ decrease it.3. The frequency of m.e.p.p.s is increased by UO22+ and decreased by Ni2+ and Zn2+ at KCl‐depolarized junctions. It is not affected by TEA.4. It has been concluded that the increased presynaptic spike duration is responsible for the delayed and prolonged transmitter release in the presence of ions which increase the nerve spike duration at Ranvier's node.It is demonstrated that some ‘specific’ effects possibly resulting from ionic competition for presynaptic sites between UO22+, Ni2+ or Zn2+ and other ions present in the Ringer may increase, interfere with, or hide the increased transmitter release that may be predicted from the lengthened presynaptic depolarization.
Factors controlling the secretion of a substance biologically resembling the 18‐monoacetate of D‐aldosterone by heart muscle
Authors: Lockett Mary F. , Retallack R. W. 
Published: December 2014

1. Previous work has demonstrated that the cat heart secretes a substance which resembles the 18‐monoacetate of
D‐aldosterone (18 MA) in chromatographic properties and biological actions. This substance (HS) releases ADH from the neurohypophysis and, in higher concentration, causes renal retention of salt and water. HS is extracted from blood, separated chromatographically and assayed in terms of equivalent 18 MA activity either by inhibition of water diuresis in rats or by reduction of the excretion of Na by the isolated kidney. Positive correlation has been demonstrated between heart rate and HS secretion.2. Heart—lung preparations from cats have been used to disclose additional factors controlling the rate of secretion of HS from heart muscle.3. Positive inotropic effects produced by administration of digoxin or adrenaline or by increase in peripheral resistance are associated with increases in the secretion of HS.4. Negative inotropic effects produced by high concentrations of procaine hydrochloride or by increase in venous return without change in external work are associated with decrease in HS secretion.
The perceived spatial frequency shift: evidence for frequency‐selective neurones in the human brain
Authors: Blakemore Colin , Nachmias Jacob , Sutton Peter 
Published: December 2014

1. Prolonged observation of a high‐contrast grating pattern causes an apparent shift in the spatial frequency of gratings subsequently viewed with the same retinal region. Gratings of higher and lower frequency than the adapting pattern seem, respectively, higher and lower than in fact they are.2. There is no significant after‐effect at the adapting frequency itself nor at frequencies more than two octaves away.3. For very low adapting frequencies, the after‐effect remains centred at about 3·0 c/deg and declines in strength as the adapting frequency is successively lowered.4. The magnitude of the after‐effect increases with the contrast of the adapting grating and the length of time spent in adaptation. It takes several hours to recover completely from 30 min adaptation.5. The phenomenon is orientation‐specific: a horizontal adapting grating has no effect on vertical test gratings. There is partial interocular transfer of the after‐effect.6. These findings provide further evidence that the visual system of man, like those of the cat and the monkey, contains neurones selectively sensitive to the orientation and dimensions of retinal images, and that these adaptable cells are actually involved in the encoding and perception of the size of simple patterns.
Post‐tetanic hyperpolarization produced by an electrogenic pump in dorsal spinocerebellar tract neurones of the cat
Authors: Kuno M. , Miyahara J. T. , Weakly J. N. 
Published: December 2014

1. Hyperpolarization following single and repetitive excitation of dorsal spinocerebellar tract (DSCT) neurones of the cat was studied by intracellular recording.2. Hyperpolarization following an antidromic action potential consisted of an initial, brief phase (undershoot) and a late, prolonged phase. The latter hyperpolarization was independent of the membrane potential, whereas the former was reversed in polarity by hyperpolarizing pulses applied across the DSCT cell membrane.3. DSCT neurones showed a prolonged hyperpolarization after a train of antidromic action potentials. The amplitude and duration of the hyperpolarization were dependent on the number and the frequency of action potentials. A similar hyperpolarization was observed following a train of impulses evoked by depolarizing pulses applied through the intracellular electrode.4. There was no detectable conductance change during the post‐tetanic hyperpolarization. The latter showed no reversal potential when the membrane potential was altered.5. The half‐decay time of the post‐tetanic hyperpolarization was lengthened when the cord temperature was lowered. The temperature coefficient (Q10) was 2·4 within the range of 31–40° C.6. The amplitude of the undershoot following each action potential was assumed to provide a criterion for the accumulation of the extracellular K+. Alterations in the amplitude of undershoots during repetitive excitation suggested that the duration of post‐tetanic hyperpolarization depends on the accumulation of extracellular K+ as well as of intracellular Na+ associated with a train of impulses.7. It is suggested that post‐tetanic hyperpolarization is produced by an electrogenic sodium pump. A possible significance of such a hyperpolarization in impulse coding is discussed.
Response characteristics of muscle afferents in the domestic duck
Authors: Dorward Patricia K. 
Published: December 2014

1. Response patterns of 116 muscle stretch receptor units isolated from the sciatic nerve of the duck have been studied, and the units classified as muscle spindles and tendon organs.2. Units classified as spindles had low threshold tensions for maintained discharge. From conduction—velocity measurements, the calculated fibrediameter spectrum appears to be unimodal, ranging from 5 to 11–12 μm.3. Spindle units showed essentially ‘in parallel’ behaviour, though increase in initial tension often led to the appearance of ‘in series’ responses. Although apparent ‘α‐excitation’ during maximal tetanic contractions was a common occurrence, no direct evidence of α‐innervation of spindles was obtained.4. Evidence has been obtained for motor innervation of spindles by fibres distinct from those constituting the alpha supply to extrafusal muscle fibres. Afferent response attributable to this fusimotor innervation is influenced by initial tension and stimulus‐frequency. Electrical thresholds for fusimotor responses ranged from 1·1 to 4·03 times α maximum.5. Tendon organ units consistently showed ‘in series’ response patterns during muscle contractions. They were not influenced by stimulation of the high‐threshold efferent nerve supply to the muscles.6. Threshold tensions required for maintained discharge in tendon organ units from m. gastrocnemius pars lateralis were characteristically high; however, many units from m. flexor perforans et perforatus d. 3 had unexpectedly low mechanical thresholds. The calculated fibre‐diameter spectrum for tendon organ units is unimodal, ranging from 4–7 to 10–11 μm. As in mammals, they contribute to the coarse‐fibre component in the muscle nerve and include the fastest fibres present.
Cat colour vision: evidence for more than one cone process
Authors: Daw N. W. , Pearlman A. L. 
Published: December 2014

1. The ability of cats to distinguish colours was investigated at mesopic and photopic levels to test the hypothesis that cats discriminate wavelength by using rods in conjunction with a single type of cone.2. Cats were trained to distinguish red from cyan, and orange from cyan at the mesopic level. They retained the ability to make this discrimination when the coloured stimuli were placed against a background bright enough to saturate the rods.3. One cat was also tested after being exposed to a bright white light of 9000 cd/m2 for a period of 5 min, and found able to distinguish red from cyan.4. These results suggest that cats have more than one type of cone. Subsequent recordings from single units in the lateral geniculate nucleus showed that there are rare opponent colour units in layer B with input from a green‐absorbing cone and a blue‐absorbing cone.
Temperature dependence of non‐electrolyte and sodium permeability in giant axon of squid
Authors: Hidalgo Cecilia , Latorre Ramón 
Published: December 2014

1. The efflux of [14C]urea was measured in micro‐injected axons at 18° C. A permeability constant for urea of (0·55 ± 0·18) × 10−6 cm/sec was calculated from these experiments.2. The influxes of urea, thiourea, ethylene glycol, urethane and toluene were measured in perfused axons at 18 ± 1° C. The permeability constants obtained from these determinations increased in the order listed, from (0·76 ± 0·19) × 10−6 cm/sec for urea to 0·80 × 10−4 cm/sec for toluene.3. The influxes of tritiated water and sodium ions at 18° C were measured in perfused axons. An average permeability of (0·78 ± 0·22) × 10−4 cm/sec for titriated water and an average influx of 23 ± 6 p‐mole/cm2 sec for sodium were obtained.4. Lowering the temperature of the external sea‐water bathing the axon from 18 to 5° C produced a decrease of 12% in the permeability of toluene, 30% for tritiated water and urethane, 55% for ethylene glycol and urea and 60% for thiourea. There was a 50% reduction in the influx of sodium for this same temperature change.5. The results obtained with the effect of temperature on permeabilities suggest that the axonal membrane has a non‐homogeneous composition. A model based on the assumption of structured aqueous channels in the membrane is postulated.
The effect on respiration of abrupt changes in carotid artery pH and PCO2 in the cat
Authors: Band D. M. , Cameron I. R. , Semple S. J. G. 
Published: December 2014

1. An in vivo pH monitoring technique was used to assess changes in pH, and by inference changes in PCO2, in the carotid artery of anaesthetized cats. The changes in carotid artery pH and respiration following abrupt injections of various acids into the carotid artery or aorta were investigated.2. Injections of saline equilibrated with 100% CO2, timed to produce changes at the carotid body chemoreceptors during early inspiration caused an increase in the tidal volume of that breath. The amplitude and rate of change of the pH changes so produced were comparable with those of the oscillations in pH produced by respiration itself.3. The respiratory responses to injection of saline equilibrated with 100% CO2 occurred whether the animal was breathing air or 100% O2.4. Injections of lactic or hydrochloric acid were without an effect on respiration, except when pH changes larger than 0·1 pH unit were produced. A NaHCO3 solution equilibrated with 30% CO2 stimulated respiration, even though the solution was alkaline to the cat's arterial blood and induced an alkaline change in arterial pH.5. Infiltration of the carotid sinus nerve area with procaine temporarily abolished the respiratory response to injections of saline equilibrated with 100% CO2.