bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluxes and distribution of calcium in rat liver cells: kinetic analysis and identification of pools
Authors: Claret-Berthon Brigitte , Claret M. , Mazet J. L. 
Published: December 2014

1. Fluxes and distribution of Ca were studied in the perfused rat liver. Kinetic analysis of 45Ca exchange revealed three compartments with time constants of 4, 14 and 223 min, pool sizes of 250, 385 and 670 μmole.kg−1 wet wt. respectively, and one non‐exchangeable compartment of 400 μmole.kg−1.2. 45Ca uptake by in situ mitochondria followed, as a function of cell loading time, a mono‐exponential function with a time constant of 16 min. This suggests that the second compartment may be identified as the intracellular pool of Ca. The calculated cell transmembrane flux of Ca was 28 μmole.kg−1 min−1 or 0·17 p‐mole.cm−2.sec−1.3. The maximum 45Ca uptake by in situ mitochondria was 2·3 n‐mole.mg−1 of protein which represents, on the basis of 50 mg of mitochondrial protein per g of fresh liver, 115 μmole.kg−1 or 30% of the cytoplasmic pool. A pool of 10·8 n‐mole.mg−1 protein (or 540 μmole.kg−1) of non‐exchangeable Ca (at steady state) was probably in the form of Ca phosphate precipitated in the mitochondrial matrix.4. Extracellular Ca pools were studied using competitor of Ca binding (La) or Ca chelators (EGTA). La displaced specifically a homogeneous pool of Ca (τ = 5·1 min) which represented a fraction (55 μmole.kg−1) of the rapidly exchangeable Ca (first compartment) without perturbing other external pools. On the other hand, EGTA displaced completely that compartment, and about 85% of the Ca of the third compartment. These results suggest that the first and the major fraction of the third compartments are extracellular. They account for 63% of total exchangeable Ca.5. A model of distribution and exchange of Ca in hepatocytes is proposed.
Left ventricular mechanoreceptors: a haemodynamic study
Authors: Fox I. J. , Gerasch D. A. , Leonard J. J. 
Published: December 2014

1. To study the function of the left ventricular mechanoreceptors, a working left ventricle preparation was devised in dogs which permitted control of pressure and flow of the isolated perfused coronary circulation and of the flow of the isolated, separately perfused systemic circulation. The systemic circulation was perfused at a constant rate so that changes in systemic pressure reflected changes in systemic resistance.2. Increases in myocardial contractility produced by injection of catecholamines into the isolated, perfused coronary circulation produced a fall in the pressure (resistance) of the isolated, separately perfused (at a constant rate) systemic circulation.3. Completeness of isolation of the coronary and systemic circulations was shown by the marked difference in appearance times between the reflex hypotensive responses from catecholamine injections into the isolated coronary circulation and the direct hypertensive response from a similar injection when the circulations were connected as well as by the marked difference between the pressure pulses recorded simultaneously on both sides of the aortic balloon separating the two circulations.4. Myocardial β receptor blockade produced by injection of propranolol into the isolated coronary circulation abolished or attenuated the changes in left ventricular myocardial contractility as well as the subsequent hypotensive responses following the similar injection of catecholamines.5. Electrical stimulation of a sympathetic nerve innervating the heart resulted in increases in left ventricular myocardial contractility and subsequent systemic hypotensive responses indistinguishable from those following injection of catecholamines.6. That distortion of the mechano‐ or stretch receptors in the left ventricular myocardium was the cause of the hypotensive responses was demonstrated by increasing left ventricular myocardial contractility by mechanically obstructing the left ventricular outflow which produced hypotensive responses similar to those following the injection of catecholamines or nerve stimulation.7. Bilateral high cervical vagotomy abolished the hypotensive responses following injection of catecholamines into the isolated coronary circulation or following left ventricular outflow obstruction in all but one instance, indicating the importance of vagal fibres to the afferent arm of the reflex.8. It is suggested that the left ventricular mechanoreceptors function normally to reduce the peripheral resistance in order to prepare the systemic circulation to receive the left ventricular output and, especially during exercise, to prepare the systemic circulation to receive the augmented cardiac output with a minimum alteration in the systemic blood pressure and to distribute this augmented output preferentially to the skeletal muscles.
Inactivation of sodium channels: second order kinetics in myelinated nerve
Authors: Chiu S. Y. 
Published: December 2014

1. Kinetics of inactivation of sodium channels in myelinated nerve from Rana pipiens were studied at 4·5 °C using the voltage clamp technique of Dodge & Frankenhaeuser (1958).2. Potassium currents were blocked by cutting the internodes in 20 m
M‐TEA‐Cl + 100 m
M‐KCl and by adding 12 m
M‐TEA‐Cl to the external Ringer. Leakage and capacitative currents were subtracted electronically.3. Kinetics of recovery from inactivation of the sodium channels were studied by inactivating the channels with a large depolarizing prepulse and allowing the channels to recover at different potentials; the extent of recovery was measured by applying a test pulse at various times after the prepulse.4. Kinetics of development of inactivation were studied by two different methods. The first was to measure the decay of sodium current under a maintained depolarization. The second method was to measure the decay of the peak sodium current in a test pulse as a function of time after the onset of a maintained depolarization. These two methods yielded similar results for the kinetics of inactivation development.5. Contrary to expectations of the Hodgkin—Huxley formalism, the time course of recovery from and development of inactivation is not strictly exponential. Rather, recovery from complete inactivation shows an initial delay which depends on recovery potentials. Development of inactivation at a fixed potential exhibits at least two exponentials.6. The steady‐state inactivation curve h∞(E) is asymmetrical and is fitted better by 1/[1+exp (A1E+B1) +exp (A2E+B2)] than by 1/[1+exp (AE+B)].7. Most of the above kinetic observation on inactivation can be fitted by the following modification of the h system of the Hodgkin—Huxley formalism: [Formula: see text]8. In the analysis it was not necessary to modify the concept of two separate processes, activation and inactivation, governing the opening and closing of the sodium channels.
The spatial extent of excitatory and inhibitory zones in the receptive field of superficial layer hypercomplex cells
Authors: Sillito A. M. 
Published: December 2014

1. An investigation has been made of the extent of inhibitory and excitatory components in the receptive field of superficial layer hypercomplex cells in the cat's striate cortex and the relation of the components to the length preference exhibited by these cells.2. Maximal responses were produced by an optimal length stimulus moving through a restricted region of the receptive field. The length of this receptive field region was less than the total length of the excitatory zone as mapped with a very short slit. Slits of similar length to the excitatory zone produced a smaller response than an optimal length slit.3. An increase of slit length so that it passed over receptive field regions either side of the excitatory zone resulted in an elimination of the response. When background discharge levels were increased by the iontophoretic application of
D, L‐homocysteic acid slits of this length were observed to produce a suppression of the resting discharge as they passed over the receptive field. They did not modify the resting discharge level when it was induced by the iontophoretic application of the GABA antagonist bicuculline. This data is taken to indicate that long slits activate a powerful post‐synaptic inhibitory input to the cell.4. Maximal inhibitory effects were only observed if the testing slit passed over the receptive field centre. That is slits with a gap positioned midway along their length so as to exclude the optimal excitatory response region surprisingly tended to produce excitatory effects rather than the expected inhibitory effects. It appears that simultaneous stimulation of the receptive field centre is a precondition for the inhibitory effect of stimulation of regions either side of the excitatory zone to be activated.5. It is suggested that the interneurones mediating the inhibitory input to the superficial layer hypercomplex cells are driven both by cells in adjacent hypercolumns with receptive fields spatially displaced to either side of the excitatory zone and by cells in the same column, optimal inhibitory effects only being achieved when both sets of input to the interneurone are activated.
The effects of position and skin temperature on the capillary pressures in the fingers and toes
Authors: Levick J. R. , Michel C. C. 
Published: December 2014

1. Direct measurements of the capillary pressure (Pc) were made in capillaries at the base of the nails of the fingers and toes of two subjects (the authors of this paper).2. With the hand or foot at heart level, Pc varied over the range of 7‐70 cm H2O with mean values of 43 cm H2O in both the fingers and the toes. Pc was higher in the arterial limb (mean 49 cm H2O) than in the venous limb (mean 34 cm H2O) of the capillary loops. The plasma colloid osmotic pressures for the two subjects were 33 and 34 cm H2O.3. For capillaries at heart level there was a strong positive correlation between Pc and skin temperature when the latter was varied over the range 23‐36 °C.4. When the hand or foot was lowered, Pc increased less than the local arterial (Pa) and venous pressures (Pv). Furthermore the variation in Pc was reduced. In fourteen measurements of Pc made on capillaries in the toes of standing subjects, Pc was no more than 10 cm H2O greater than Pv. It is argued that the increase in the ratio (Pa — Pc)/(Pc — Pv) with hydrostatic load represents an increase in the ratio of pre‐ to post‐capillary resistance.5. When Pv was increased by inflating a sphygmomanometer cuff around the upper arm, (Pa — Pc)/(Pc — Pv) increased in the hand held at heart level. These changes were similar to those seen with changes in position.6. The implications of the results are discussed with respect to fluid balance between the blood and tissues. It is argued that since Pc in the warm hand was never less than the plasma colloid osmotic pressure, fluid is not reabsorbed from the tissues into the capillaries of the warm skin of the hand even at heart level. Compensatory changes in the circulation appear to minimise the filtration of fluid into the feet of the standing subject but the mechanism of these changes remains obscure.
THE POTASSIUM CURRENT UNDERLYING DELAYED RECTIFICATION IN CAT VENTRICULAR MUSCLE
Authors: McDonald T. F. , Trautwein W. 
Published: December 2014

1. Outward currents in cat ventricular fibres have been studied using the single sucrose gap method. The time dependent outward currents can be separated into a fast component, IK, and a slow component, Ix. The voltage dependence of the IK time constant was bell‐shaped, being about 150 msec at ‐90 mV, 500 msec at ‐25 mV and 300 msec at +30 mV. The combination of much faster time constants and larger amplitudes relative to Ix allowed the estimation of IK amplitude, but not time course, from semilog plots of membrane currents accompanying 2 sec depolarizations.2. The ‘steady‐state’ outward current at 2 sec (Iss) was separated into time independent background current (Ibg) and time dependent IK. The activation threshold for IK was about ‐50 mV and its amplitude increased steeply between ‐30 and +10 mV. The ratio of Ibg to IK was about 1 between ‐30 and +30 mV.3. The current—voltage relations of Iss and Ibg showed inward going rectification but negative slope regions were not observed. Raising the external K concentration from 3 to 10, 20 and 30 m
M increased conductance and induced ‘cross‐overs’ in the current—voltage relations. Increases in conductance were offset by the reductions in driving force, i.e. currents at plateau potentials were not larger in high K solutions.4. K accumulation occurs in response to prolonged membrane depolarization but conductance rather than accumulation appears to be responsible for the slowly rising outward current, Ix. However, the accumulation which takes place during the activation of Ix may preclude an accurate determination of its time course and reversal potential.5. The potential at which outward IK tails declined to zero was strongly dependent on external K concentration in the range 3‐30 m
M. Inward going IK tails were difficult to detect because control hyperpolarization from the resting potential triggered large inward time dependent currents. Evidence is presented suggesting that much of this time dependency is due to the depletion of extracellular K from regions of restricted diffusion.6. The steady‐state activation variable (n∞) of the IK‐system had to be calculated from isochronic (300 msec activating pulses) activation relations and τns because shifts in VK due to K accumulation precluded complete activations. The shape of n∞ was sigmoid approaching 0 at ‐60 mV, 0·5 at ‐20 mV and 1 at +20 mV.7. The fully activated current—voltage relation of IK displayed inward going rectification.8. It is concluded that there are strong similarities between IK in ventricular muscle and ix1 in Purkinje fibres. Possible counterparts in frog atrial muscle include the currents labelled I1 and ix.slow.
The control of enzyme secretion from fly salivary glands
Authors: Bay Christina M. Hansen 
Published: December 2014

1. Stimulation of fluid secretion from fly salivary glands by 5‐hydroxytryptamine (5‐HT) is known to involve calcium and cyclic AMP. Isolated salivary glands were used to investigate the role of these second messengers in the control of enzyme (sucrase) secretion.2. The protein component of secretion from isolated glands treated with 5‐HT appears to be identical to that of saliva secreted by flies during feeding.3. Stimulation of fluid secretion by 5‐HT follows a definite dose‐response curve, but there is no consistent relationship between the rate of enzyme secretion and the stimulating concentration of 5‐HT.4. Exogenous cyclic AMP causes secretion of enzymes as well as of fluid, thus mimicking the action of 5‐HT. The phosphodiesterase inhibitor theophylline enhances the rate of 5‐HT‐stimulated enzyme secretion.5. Removal of calcium from the bathing medium enhances enzyme secretion in response to 5 or 10 n
M‐5‐HT but has no effect on enzyme secretion stimulated by 100 n
M‐5‐HT or by cyclic AMP.6. Addition of 0·1 m
M‐lanthanum to medium containing 2 m
M‐calcium mimics the effect of calcium‐free solution on 5‐HT‐stimulated enzyme secretion.7. The ionophore A 23187 causes secretion of both fluid and enzyme. The secretory rate is initially high but soon declines and ceases after about 40 min.8. Enzyme secretion in response to 5‐HT or to cyclic AMP is progressively inhibited as the concentration of potassium is increased from 10 to 80 m
M. Secretion in response to A 23187 is initially inhibited by 80 m
M‐potassium but then partially recovers.9. The rate of enzyme secretion appears to be affected by the intracellular concentrations of both calcium and cyclic AMP. It is possible that the rate of enzyme secretion increases as the intracellular calcium concentration rises, until the optimal calcium concentration is reached when further increase in the level of calcium progressively inhibits secretion. The optimal calcium concentration for enzyme secretion is lower than that for fluid secretion, and 5‐HT normally causes maximal fluid secretion and submaximal enzyme secretion.
Effect of prior visual experience on cortical recovery from the effects of unilateral eyelid suture in kittens
Authors: Blasdel Gary G. , Pettigrew John D. 
Published: December 2014

The reversibility of monocular deprivation was tested physiologically in twelve kittens which had received varying amounts of normal visual experience prior to unilateral eye closure. Recordings obtained from cells in cortical area 17 indicated that the effects of monocular deprivation are reversible in cats as old as 8 weeks if the animals have been allowed normal visual experience before eye closure.1. Four kittens had their right eyes closed at 3, 4, and 5 weeks of age. All animals were reverse sutured at about 8 weeks of age, and after 2 weeks forced usage of the deprived eye, each animal was tested physiologically for recovery. Single unit recordings revealed a consistent relation between the extent to which the effects of initial deprivation could reverse and the age of the animal at the time of this deprivation. Recordings from a fifth, 8 week old kitten, which had been monocularly deprived for 3 weeks, ensured that our shortest period of deprivation induces a severe deficit.2. Two kittens which were reared in the dark for 4 and 5 weeks before unilateral eye closure, failed to show substantial (greater than 20%) reversal when reverse lid‐sutured at 8 weeks of age. This failure suggests that kittens having their eyes closed after normal experience show enhanced reversibility, at least in part, on account of their early experience and not necessarily because of shorter deprivation. A litter‐mate of one of these kittens was allowed 9 days of normal vision after dark rearing and before lid suture. Recordings which were performed both before and after 6 days of reverse suture demonstrated a near total (85%) reversal in ocular dominance.3. Three animals, monocularly deprived after some normal experience, recovered substantial numbers of binocular cells after both eyes had been allowed to remain open. In one of these cats the effectiveness of monocular deprivation was confirmed physiologically before eye opening. These findings contrast with those of other workers who have failed to find many binocular cells in kittens that had been allowed to recover, with eye opening, from monocular deprivation which had lasted since birth.4. One kitten was reared for 2 weeks (3‐5 weeks of age) with alternating monocular deprivation. Single unit recordings from this cat, which were made after four additional weeks of unilateral eye closure, revealed some cells which had resisted monocular deprivation and which responded strongly to stimulation of the deprived eye. Reverse suture in the same animal led to the recovery of many cells (36%), dominated by the initially deprived eye, but did not result in a reversal in ocular dominance.
Studies on kallikrein in the duct systems of the salivary glands of the cat
Authors: Shnitka T. K. , Maranda B. , Rodrigues J. A. A. , Schachter M. , Weinberg J. 
Published: December 2014

By correlating immunofluorescence light microscopy with electron microscope studies and with kallikrein concentrations under various conditions, we have made the following observations and conclusions about kallikrein in the submandibular and other salivary glands.1. In the submandibular gland, specific immunofluorescence to kallikrein was observed in the luminal region of the striated ducts particularly, but also in the outer epithelial cells of the stratified epithelial collecting ducts. Sympathetic nerve stimulation resulted in a reduction in intensity of specific fluorescence and in its increased localization towards the lumen. The nearly complete elimination of kallikrein from the gland by duct obstruction for four days resulted in complete disappearance of specific fluorescence in the gland. Prolonged parasympathetic nerve stimulation at frequencies which did not reduce the kallikrein concentration of the gland failed to alter the specific immunofluorescence despite copious secretion of saliva. Our results failed to reveal evidence of secretion of kallikrein either into or towards the interstitium of the gland.The luminal layer of stratified epithelial cells in the collecting ducts contained small secretory granules closely resembling those in the striated ducts. Our results are not conclusive, but do suggest that kallikrein is located in these granules whence it is secreted into the lumen of the duct.2. The parotid gland was found to contain much lower concentrations of kallikrein than the submandibular gland. This finding was associated with the presence of far fewer striated ducts in the parotid gland. Otherwise, specific fluorescence and the response to sympathetic nerve stimulation was like that of the submandibular gland. Small secretory granules in the striated and collecting ducts resembled those of the submandibular gland.3. The sublingual gland, like the parotid, had a low concentration of kallikrein and very few striated ducts. These ducts were unevenly distributed and were concentrated in only a few lobules of the gland. Specific immunofluorescence was seen only in sections containing striated ducts.4. The possible physiological role of kallikrein in the salivary glands is discussed.
Oxytocin release following osmotic activation of oxytocin neurones in the paraventricular and supraoptic nuclei
Authors: Brimble M. J. , Dyball R. E. J. , Forsling Mary L. 
Published: December 2014

1. Recordings were made from a total of 35 antidromically identified neurones in the paraventricular (PV) and supraoptic (SO) nuclei of urethane‐anaesthetized lactating rats. During recording plasma osmotic pressure was raised by 12 m‐osmole/kg by injection of hypertonic solutions of NaCl, LiCl, or mannitol.2. Nine PV neurones (mean firing rate 4·2 ± 1·0 (
S.E.) spikes/sec) were classified as oxytocin cells because they gave a burst of activity before reflex milk‐ejections. None of these showed a bursting (phasic) firing pattern. Ten PV neurones (mean firing rate 1·8 ± 0·2 spikes/sec) fired phasically either before or after injection of hypertonic NaCl and were classified as vasopressin cells. The remaining six PV cells (mean firing rate 1·6 ± 0·9 spikes/sec) showed no bursts of firing related to milk ejection and did not fire phasically.3. Increasing plasma osmotic pressure by injection of hypertonic NaCl increased the mean firing rate of PV oxytocin cells to 7·0 ± 1·0 spikes/sec. Vasopressin cells in the PV nucleus were much less responsive and the mean firing rate after injection was 2·9 ± 0·4 spikes/sec. The third group of PV neurones was unresponsive.4. Plasma oxytocin concentration (determined by radioimmunoassay) increased from 2·1 ± 0·3 μu./ml. in the control period to 10·9 ± 2·8 μu./ml. 30 min after
I.P. injection of 1 ml. 1·5
M‐NaCl and to 14·8 ± 2·8 μu./ml. following injection of a second 1 ml. 1·5
M‐NaCl.5. The responses of oxytocin and vasopressin neurones in the SO nucleus to an increase in plasma osmotic pressure following injections of hypertonic solutions of LiCl or mannitol were similar to those observed when plasma osmotic pressure was raised by NaCl.6. It may be concluded that both oxytocin and vasopressin cells in the neurohypophysical system are responsive to the osmotic pressure of the blood plasma rather than to Na+ or Cl− concentration, that osmotic activation of oxytocin cells releases sufficient oxytocin to increase its plasma concentration, and that there may be a functional difference between the SO and PV nuclei.