bluuebunny/crossref_metadata_2025 huggingface dataset:
Depolarization‐induced influx of sodium in response to phenylephrine in rat atrial heart muscle.
Authors: Jahnel U , Nawrath H , Carmeliet E , Vereecke J
Published: December 2014

1. The effects of alpha 1‐adrenoceptor stimulation on transmembrane potential, currents and ion fluxes were investigated in multicellular preparations and/or single cells obtained from the left atrium of rat hearts. 2. In multicellular preparations, phenylephrine caused a concentration‐dependent positive inotropic effect, an increase in action potential duration, and a decrease in resting potential; the effects were antagonized by phentolamine. 3. In the presence of phenylephrine (100 mumol/1), two levels of resting potential were observed when the preparations were, alternately, electrically stimulated or kept at rest (‐74 +/‐ 1 mV during activity and ‐62 +/‐ 4 mV at rest; mean +/‐ S.E.M.; n = 9). 4. In resting preparations, the depolarization in response to phenylephrine was eliminated in low‐Na+ solution (12 mmol/l) and antagonized by tetrodotoxin (10 mumol/l). 5. The phenylephrine‐induced depolarization was also seen in nominally Ca(2+)‐free solution and in the presence of (‐)‐devapamil (1 mumol/l). 6. The alkylating agent N‐ethyl‐maleimide (30 mumol/l) abolished the depolarizing effect of phenylephrine. 7. Phorbol 12,13‐dibutyrate (10 mumol/l) also abolished the depolarizing effect of phenylephrine. 8. Phenylephrine caused a significant increase of 22Na+ uptake in resting preparations and of 45Ca2+ uptake in beating preparations. 9. The depolarizing effect of phenylephrine was also observed in single atrial myocytes. Steady‐state membrane currents in response to 500 ms depolarizing and hyperpolarizing voltage clamp steps were decreased. The cross‐over of I‐V curves under control and test conditions was at about ‐70 mV. The effects of phenylephrine were antagonized in the presence of phentolamine. 10. After suppression of potassium currents by substitution of CsCl for internal and external KCl ([KCl]o), phenylephrine had no effect on membrane currents. 11. In conclusion, we presume the following sequence of events in response to phenylephrine in rat atrial heart muscle. First, the stimulation of alpha 1‐adrenoceptors decreases the K+ conductance thereby producing a depolarization in the presence of an inward current. Second, the change of the membrane potential in the depolarizing direction induces a TTX‐sensitive Na+ window current which further propels the depolarization. Third, the increase in Na+ influx may increase Ca2+ influx by activating the Na(+)‐Ca2+ exchange in mechanism. The greater influx of Ca2+ may contribute to the positive inotropic effect in response to phenylephrine.
Effects of 2,3‐butanedione monoxime on whole‐cell Ca2+ channel currents in single cells of the guinea‐pig taenia caeci.
Authors: Lang R J , Paul R J
Published: December 2014

1. The inhibitory actions of cadmium (Cd2+), nifedipine and 2,3‐butanedione monoxime (BDM) on whole‐cell Ca2+ channel currents in single cells of the guinea‐pig taenia caeci were investigated using a single‐electrode whole‐cell voltage‐clamp technique. 2. Calcium channel currents were isolated using pipette solutions containing Cs+, tetraethylammonium and ATP (3 mM). Ca2+ or Ba2+ (7.5 mM) in the bathing solution acted as the charge carrier during inward current flow. Ca2+ channel currents in 7.5 mM‐Ba2+ (IBa) were recorded at potentials positive to ‐40 mV, were maximal near 0 mV and reversed near +60 mV. Ca2+ channel activation showed a sigmoidal relationship with potential, which was half‐maximal at ‐13 mV. 3. Both the inward and outward flow of current was depressed and eventually blocked by 0.3‐100 microM‐Cd2+, 0.1‐10 microM‐nifedipine and 2‐20 mM‐BDM. Half‐maximal blockade of IBa at 0 mV was achieved with approximately 3 microM‐Cd2+, 1 microM‐nifedipine and 10 microM‐BDM. Steady‐state activation curves were not affected by Cd2+ or BDM, but were shifted in the hyperpolarizing direction by nifedipine at concentrations > 1 microM. 4. Calcium channel currents in single cells and K+ contractures in intact strips were both blocked in a voltage‐dependent manner. Steady‐state inactivation curves (f infinity (V)) for IBa were shifted 20 mV in the hyperpolarizing direction by 0.3 microM‐nifedipine and 4 mV by 10 mM‐BDM. From these shifts a dissociation binding constant to inactivated Ca2+ channels for nifedipine was estimated as 78 nM, and for BDM, 5 mM. 5. At 10 microM Cd2+ produced a 43 +/‐ 6% (n = 3) block of the inward current at 0 mV when Ca2+ (7.5 mM) was the charge carrier (ICa), compared with the 36 +/‐ 3% block of IBa induced by 1 microM‐Cd2+, consistent with the suggestion that Ca2+, Ba2+ and Cd2+ compete for the same binding site. In contrast, nifedipine (1 microM) and BDM (10 mM) blocked ICa more effectively than IBa. 6. Bay K 8644 (1.0 microM) increased Ca2+ channel currents two‐ to fourfold at all potentials due to a shift, of approximately 10 mV in the negative direction, of their activation curve and an equal shift in the positive direction of their inactivation curve. BDM (5‐10 mM) could antagonize the action of Bay K 8644, shifting both curves back towards their control.(ABSTRACT TRUNCATED AT 400 WORDS)
Changes in the response to magnetic and electrical stimulation of the motor cortex following muscle stretch in man.
Authors: Day B L , Riescher H , Struppler A , Rothwell J C , Marsden C D
Published: December 2014

1. The effect of muscle stretch on the EMG response from the stretched muscle to transcranial magnetic stimulation of the motor cortex was studied in eight subjects. Muscle stretch was produced by increasing the torque of a motor acting through a lever which was held at constant position by a flexion force of the index and middle fingers. EMG responses were recorded from fine‐wire electrodes inserted into flexor digitorum profundus muscle in the forearm. They consisted of a spinal latency component and a long‐latency component which could in some subjects be separated into an early and a late phase. 2. In four subjects, four intervals between the stretch and the cortical stimulus were explored using three intensities of cortical stimulation. At all three intensities, when the magnetic cortical stimulus was timed to produce an EMG response in the period of the later part of the long‐latency stretch reflex the response was larger than when it was timed to produce a response in the period of the short‐latency spinal reflex or when superimposed on the tonic muscle activity used to resist the standing torque of the motor. 3. When the intensity of magnetic cortical stimulation was reduced so that it was just below threshold to produce an EMG response in the short‐latency reflex period or on the background tonic EMG activity, it still was capable of producing a response when superimposed on the long‐latency stretch reflex. 4. In four subjects the time course of this effect was studied in more detail using only one intensity of magnetic cortical stimulus set to be just above threshold to produce a response in tonically active muscles. The time course of the facilitatory effect was similar to the time course of the later part of the long‐latency stretch reflex. From these data it was not possible to determine whether the early part of the long‐latency stretch reflex also was accompanied by the facilitatory effect since this component was present in only one of the four subjects. 5. The facilitatory effect persisted after the ulnar and median nerves were totally blocked at the wrist by injections of local anaesthetic. This suggests that inputs from muscle receptors of the stretched muscle contribute to the effect.4=
Activation of ion channels in the frog endplate by several analogues of acetylcholine.
Authors: Marshall C G , Ogden D , Colquhoun D
Published: December 2014

1. Single‐ion‐channel recording has been used to estimate the equilibrium concentration‐response relationship for several acetylcholine analogues. The response, corrected for desensitization, was taken as the probability of a channel being open during clusters of openings that were separated by desensitized periods. 2. All agonists were able to block the channels which they themselves opened. Carbachol, suberyldicholine and the sulphonium analogue of acetylcholine were all found to be efficacious agonists in the sense that the results indicate that all of them, in sufficiently high concentration, would be able to open 90% or more of channels if it were not for channel block. 3. In the case of suberyldicholine the results are much as predicted by the interpretation of the fine structure of channel openings at low agonist concentrations. 4. The maximum probability of opening that could be obtained with decamethonium and with phenyltrimethylammonium was low (below 4%), and it was not possible to distinguish whether this was wholly a result of the powerful (relative to activation potency) channel‐blocking action of these agonists, or whether it was to some extent attributable to their being genuine partial agonists. 5. The results suggest that, for a range of agonists, differences in equilibrium potency are usually more strongly influenced by affinity for binding to the resting state of the receptor than by ability to activate the receptor once bound, though in the case of suxamethonium (relative to acetylcholine) the contributions of each factor are similar.
The influence of lactic acid on adenosine release from skeletal muscle in anaesthetized dogs.
Authors: Ballard H J
Published: December 2014

1. In anaesthetized and artificially ventilated dogs, a gracilis muscle was vascularly isolated and perfused at a constant flow rate of 11.9 +/‐ 2.2 ml min‐1 100 g‐1 (mean +/‐ S.E.M., n = 16; equivalent to 170.2 +/‐ 21.3% of its resting free flow). 2. Stimulation (3 Hz) of the obturator nerve produced twitch contractions of the gracilis muscle, reduced venous pH from 7.366 +/‐ 0.027 to 7.250 +/‐ 0.031 (n = 5), increased oxygen consumption from 0.62 +/‐ 0.24 to 2.76 +/‐ 0.46 ml min‐1 100 g‐1 (n = 5) and increased adenosine release from ‐0.40 +/‐ 0.14 (net uptake) to 1.36 +/‐ 0.50 nmol min‐1 100 g‐1 (n = 8). 3. Infusion of lactic acid (4.2 mM) into the artery reduced venous pH to 7.281 +/‐ 0.026 (n = 5) and increased adenosine release to 0.96 +/‐ 0.40 nmol min‐1 100 g‐1 (n = 8), but did not significantly alter oxygen consumption (0.80 +/‐ 0.19 ml min‐1 100 g‐1; n = 5). Stimulation (3 Hz) in the presence of lactic acid infusion produced no further significant changes in venous pH or adenosine release, but increased oxygen consumption to 2.53 +/‐ 0.37 ml min‐1 100 g‐1 (n = 5). 4. Infusion of a range of lactic acid concentrations (> or = 1.83 mM) produced dose‐dependent increases in adenosine release. The maximum lactic acid concentration tested (5.95 mM) reduced venous pH to 7.249 +/‐ 0.023 (n = 5) and increased adenosine release to 2.64 +/‐ 1.26 nmol min‐1 100 g‐1 (n = 6). 5. A strong correlation existed between the adenosine release and the venous pH (r = ‐0.92); points obtained during muscle stimulation and/or lactic acid infusion fell on a single correlation line. 6. The vasoactivity of adenosine administered by close‐arterial injection was unaltered by infusion of either lactic acid (7.2 mM) or saline. 7. These results suggest that the release of adenosine from skeletal muscle can be induced by a decrease in pH (probably at an intracellular site), and that this mechanism may contribute to the release of adenosine during muscle contractions.
Effect of sodium and calcium on basal secretory activity of rat neurohypophysial peptidergic nerve terminals.
Authors: Toescu E C , Nordmann J J
Published: December 2014

1. The release of arginine vasopressin (AVP) from a perifused preparation of peptidergic nerve terminals isolated from rat neurohypophyses was studied during manipulations of the external sodium and calcium concentrations. Intracellular concentrations of these two ions were manipulated by use of ouabain and a calcium ionophore, respectively. 2. Removal of extracellular Na+ caused, in a concentration‐dependent manner, a significant decrease of secretory activity. Conversely, graded addition of Na+ to a Na(+)‐free perifusion medium increased secretion. Half‐maximal activation of secretory activity was attained at ca 75 mM [Na+]o. 3. Manipulations of extracellular Ca2+ did not affect the level of hormonal secretion in the absence of extracellular Na+. However, when Na+ was present in the perifusion medium, removal of extracellular Ca2+ induced an increase of secretory activity. 4. The effects of manipulations of [Na+]o were not dependent on the presence of Ca2+ in the perifusion medium nor on the nature of the Na+ replacement used (i.e. choline or mannitol). 5. Ouabain (0.1 mM) increased the basal secretory activity and potentiated the secretory response to removal of Ca2+ from the perifusion medium. 6. The Ca2+ ionophore A23187 stimulated, in a concentration‐dependent fashion, the secretory activity of the peptidergic nerve terminals and this stimulation was strictly dependent on the presence of Ca2+ in the perifusion medium. 7. These results show that basal secretion is directly dependent on [Na]o and indicate that intracellular Na+ is an important factor in the control of secretory mechanisms. Evidence is presented in regard to a possible antagonistic effect of extracellular Ca2+ and Na+ on secretion.
Evidence for multiple types of Ca2+ channels in acutely isolated hippocampal CA3 neurones of the guinea‐pig.
Authors: Mogul D J , Fox A P
Published: December 2014

1. Current through Ca2+ channels was studied in acutely isolated guinea‐pig pyramidal neurones from the CA3 region of the hippocampus. Both the whole‐cell and single‐channel patch‐clamp configuration were used. 2. Both whole‐cell and single‐channel currents displayed holding potential sensitivity indicative of two high‐threshold currents similar to L‐ and N‐type Ca2+ currents. 3. A low‐threshold whole‐cell current, similar to T‐type current seen in dorsal root ganglion (DRG) neurones, activated at ‐60 to ‐50 mV and was blocked by nickel (100 microM) and amiloride (500 microM). Exposure to 50 microM‐cadmium left a fraction of the T‐type current intact but blocked N‐ and L‐type current. This T‐like component needed extremely negative holding potentials to be completely reprimed. 4. Whole‐cell N‐type Ca2+ channel current was blocked by omega‐conotoxin (1 microM). From a holding potential of ‐90 mV, omega‐conotoxin decreased the peak whole‐cell current by 33%. 5. A slowly inactivating high‐threshold Ca2+ current (L‐type) that was present at depolarized holding potentials, displayed dihydropyridine sensitivity. From a holding potential of ‐50 mV, addition of the dihydropyridine Ca2+ channel antagonist nimodipine (2 microM) to the bath decreased whole‐cell peak current by 45%. Interestingly, at negative holding potentials nimodipine worked as an agonist. From a holding potential of ‐90 mV, nimodipine (2 microM) increased peak current at test potentials from ‐50 to ‐20 mV and shifted the peak of the current‐voltage relationship in the hyperpolarizing direction similar to the effect of Ca2+ channel agonist Bay K 8644. Exposure to Bay K 8644 (2 microM) increased peak current and single channel open probability independent of holding potential while shifting the peak of the whole‐cell current‐voltage relationship 11 mV in the hyperpolarizing direction. Our experiments suggest that there are approximately the same number of L‐type as omega‐conotoxin sensitive N‐type Ca2+ channels in CA3 neurones. 6. A high‐voltage‐activated whole‐cell current was still present in cells exposed to both nimodipine and omega‐conotoxin (2 and 1 microM, respectively) suggesting the existence of a fourth type of Ca2+ channel in these neurones or that a population of either L‐type or N‐type Ca2+ channels did not respond to dihydropyridine antagonists or omega‐conotoxin, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)
Kinetic properties of the caffeine‐induced transient outward current in bull‐frog sympathetic neurones.
Authors: Sadoshima J , Akaike N
Published: December 2014

1. The kinetic properties of the caffeine‐induced transient outward current (ICaff) of the bull‐frog sympathetic neurone were investigated using the extremely rapid concentration‐jump technique. By setting the holding potential at the equilibrium potential for Cl‐ (‐50 mV), the involvement of the Ca(2+)‐activated Cl‐ current was suppressed. Using a Na(+)‐free (Tris) external solution, the involvement of the Na(+)‐dependent sustained outward current was eliminated. The ‘M’ conductance was also occluded by pre‐treatment with muscarine. Under these experimental conditions, ICaff consisted of a TEA‐sensitive Ca(2+)‐activated K+ current. 2. When the latent period from the application of caffeine until the onset of ICaff (termed the ICaff latency) was measured, 10 mM‐caffeine gave a latency of 10.5 +/‐ 0.7 ms (n = 14, mean +/‐ S.E.M.) at 22 degrees C. The latency was independent of caffeine concentration between 3 and 30 mM. 3. The ICaff latency was temperature‐dependent; it was shortened when the temperature was elevated. 4. Both the time to peak and half‐decay time of ICaff were decreased with increasing caffeine concentration. In each cell, these parameters decreased by increasing the amplitude of ICaff. 5. At 22 degrees C, the time to peak and the half‐decay time of ICaff elicited by 10 mM‐caffeine showed a linear relationship, and this relationship was preserved on either elevating or lowering the temperature. On lowering the temperature (12 degrees C), the time to peak shortened whereas the half‐decay time was prolonged. On elevating the temperature (32 degrees C), the time to peak was prolonged whereas the half‐decay time was shortened. 6. When EGTA in the intracellular solution was replaced by equimolar BAPTA, the time to peak was prolonged while the half‐decay time was shortened. 7. It is concluded that caffeine can activate ICaff, with a time course in the order of milliseconds, and that the kinetics of activation and inactivation of ICaff reflect the time‐dependent change in the total amount of intracellular free Ca2+.
Protein kinase C‐mediated desensitization of the muscarinic response in rat lacrimal gland cells.
Authors: Tan Y P , Marty A
Published: December 2014

1. Desensitization of the Ca2+ release response evoked by acetylcholine in acinar cells from rat lacrimal glands was studied using the Ca(2+)‐sensitive dye Fura‐2. The evolution of the amplitude and half‐maximal rise time (t1/2) of the Ca2+ response was followed as a function of trial number in a series of stimulations. 2. Under control conditions repetitive applications of acetylcholine (15 s long applications every minute) led to a linear decrease of the amplitude and to a linear increase of t1/2 with trial number. Both amplitude and t1/2 recovered their control values after 20 min of washing. 3. Staurosporine (0.2‐1 microM), an inhibitor of protein kinase C, was found to decrease the slopes of the variation of amplitude and t1/2 with trial number. 4. Prolonged treatment with 12‐O‐tetradecanoyl phorbol 13‐acetate (TPA), an activator of protein kinase C (100‐250 nM for 2‐4 h), also led to a markedly decreased desensitization, presumably as a result of down‐regulation of protein kinase C. On the other hand moderate pre‐treatments with TPA (16‐32 nM for 10 min) strongly inhibited the response, most probably as a result of protein kinase C activation. 5. Application of oleoylacetylglycerol (50 microM), a weaker activator of protein kinase C, inhibited the response and enhanced desensitization. These effects were, however, not obtained after down‐regulation of protein kinase C with strong exposure to TPA. 6. We conclude that protein kinase C activation following the ACh‐induced Ca2+ rise and the concomitant diacylglycerol production mediates desensitization of the response. 7. Arachidonic acid (100 microM) inhibited the ACh‐induced response and enhanced desensitization. However, this effect did not appear to be mediated by protein kinase C since it was also obtained with docosahexaenoic acid, an analogue of arachidonic acid which does not activate protein kinase C.
Short‐term saralasin blockade of renal hypertension in fetal lambs.
Authors: Anderson D F , Binder N D
Published: December 2014

1. In the fetal lamb, suprarenal aortic blood flow reduction is known to lead to an upper body hypertension. The dependency of this hypertension on the renin‐angiotensin system was investigated. 2. Intravenous infusions of saralasin or saline vehicle were begun before suprarenal aortic blood flow reduction and continued for 24 h. 3. In those fetuses receiving saline, upper body arterial blood pressure was significantly elevated both 60 min (P < 0.05) and 24 h (P < 0.05) after blood flow reduction. In those fetuses receiving an infusion of saralasin, upper body arterial blood pressure failed to rise after 60 min of blood flow reduction. However, 24 h later, blood pressure was elevated (P < 0.05), though the increase was not as great as that seen in the saline infused fetuses (P < 0.05). 4. From these results, we conclude that the initial increase in upper body arterial blood pressure seen after suprarenal aortic blood flow reduction is dependent upon the renin‐angiotensin system. However, as early as 1 day later, some other mechanism is responsible for sustaining the hypertension.
Probabilistic secretion of quanta from nerve terminals in toad (Bufo marinus) muscle modulated by adenosine.
Authors: Bennett M R , Karunanithi S , Lavidis N A
Published: December 2014

1. A study has been made of the effect of blocking endogenous adenosine on the statistics of quantal secretion at nerve terminals in toad (Bufo marinus) muscle during summer and winter. 2. Exogenous adenosine (10‐50 microM) reduces the mean quantal content of the endplate potential (EPP) recorded with an intracellular microelectrode (m) by 36 +/‐ 6% (mean +/‐ S.E.M.), independent of the control value of m in both summer and winter. The variance of the EPP (S2) was reduced by adenosine in proportion to m, so that the probability of quantal secretion (p) remained relatively constant. 3. Exogenous adenosine reduces the mean quantal content of secretion recorded with an extracellular electrode (m(e)) to a similar extent (47 +/‐ 6%) at different relatively high secreting sites along nerve terminal branches in both summer and winter. 4. Both theophylline (20‐100 microM) and adenosine deaminase (2.5 i.u./ml) increase the amplitude of the EPP in summer in a [Ca2+]o of 0.5 mM or greater; a maximum increase of about 40% is reached at a [Ca2+]o of 1.2 mM. The amplitude of the EPP in winter is usually reduced by theophylline in a [Ca2+]o of 0.5 mM, but is always increased in a [Ca2+]o greater than 0.9 mM to reach a maximum increase of about 40% at high [Ca2+]o. 5. The variance of the EPP (S2) was always increased by theophylline to a greater extent than m in summer, so that p decreased and Poisson rather than binomial statistics could be used to describe the distribution of EPP amplitudes. In winter, theophylline generally increased m and S2 to about the same extent, so that p did not change much. 6. An autocorrelation analysis of the amplitude of successive EPPs in a long train at 0.5 Hz in high [Ca2+]o showed that these are likely to be independently distributed. Adenosine secreted by one impulse is then unlikely to affect secretion by a subsequent impulse in the train. 7. These observations are discussed in terms of the hypothesis that endogenously secreted adenosine at a release site inhibits secretion by nearby release sites in summer; this has the effect of reducing m and to a greater extent S2 so that binomial rather than Poisson statistics can describe the frequency distribution of EPP amplitudes.
Electrogenic Na(+)‐Ca2+ exchanger, the link between intra‐ and extracellular calcium in the Limulus ventral photoreceptor.
Authors: Deckert A , Stieve H
Published: December 2014

1. Limulus ventral photoreceptors were injected with Arsenazo III and the internal change in the calcium concentration, [Ca2+]i, was measured under voltage clamp conditions. It is shown that in response to a light flash the rising phase of the [Ca2+]i is independent of the clamp voltage, Vm. This observation is contrary to other results reported in the literature. Experiments are reported that resolve this contradiction (see paragraph 4). 2. The relaxation of the [Ca2+]i after a bright light flash was observed to have a fast and slow phase. A function consisting of the sum of an exponential and a ramp was fitted to the relaxation. The fast phase, characterized by the time constant of the exponential, was observed not to depend on Vm, while the slow phase, characterized by the slope of the ramp, was strongly dependent on Vm. Furthermore the slope of the slow phase is shown to depend on the external Na+ concentration, but not the time constant of the fast phase. 3. In the dark the [Ca2+]i was observed to increase when the cell was depolarized and to decrease when the cell was hyperpolarized. This observation was more pronounced when the cell was continuously illuminated. 4. When the cell was clamped to a depolarizing voltage before illumination of the cell, the maximum of the calcium indicator signal was observed to depend on how long the cell had been clamped before applying the light stimulus. This experiment resolves the contradiction mentioned in paragraph 1. 5. The results presented here are consistent with the interpretation that a Na(+)‐Ca2+ exchanger with a stoichiometry greater than 2:1 is the predominant link between intra‐ and extracellular calcium. Secondly that the light‐induced intracellular calcium increase comes from a release by intracellular stores. Finally a measurable uptake of calcium occurs after a light‐induced release, possibly by the internal calcium stores. The two‐phase recovery of [Ca2+]i after a light flash is interpreted as being a calcium uptake by the internal stores, the fast phase, and removal by the electrogenic Na(+)‐Ca2+ exchanger, the slow phase.
Increasing quantal size at the mouse neuromuscular junction and the role of choline.
Authors: Yu S P , Van der Kloot W
Published: December 2014

1. In frog a variety of treatments have been shown to increase quantal size at the neuromuscular junction (NMJ), apparently by releasing more acetylcholine (ACh) per quantum. The present experiments were undertaken to see whether similar changes occur at the mouse NMJ. 2. None of the hormones tested, adrenaline, insulin or corticosteroids, significantly increased quantal size at the mouse NMJ. 3. Soaking diaphragms in hypertonic solution (about 475 mosmol/kg) for 15‐30 min roughly doubled the size of miniature endplate potentials (MEPPs), miniature endplate currents (MEPCs), and uniquantal endplate potentials (EPPs). We will refer to these as ‘large quanta’. Note that all of the measurements were made after returning the preparation to normal (Tyrode) solution. 4. In frog hypertonic solution made with sodium gluconate replacing NaCl increases quantal size four‐ rather than two‐fold. In mouse there was little difference in the effects of solutions made with the two anions. In Cl(‐)‐free hypertonic solution, made with sodium gluconate and SO4(2‐) solutions, quantal size increase is somewhat less, so there may be a role for Cl‐ in enlarging quantal size. 5. After hypertonic treatment, quantal size remained elevated for at least 1 h and then gradually declined back to usual levels. The data suggest a gradual decrease in mean quantal size, rather than the appearance of a new subpopulation of smaller quanta. 6. Hypertonic treatment did not change the endplate depolarization in response to ionophoretically applied ACh. This suggests that the increased quantal size is not due to a postsynaptic change. Large MEPP's disappear in the presence of tubocurarine and reappear when the drug is washed away. 7. Vesamicol is an inhibitor of active ACh uptake into isolated synaptic vesicles. 5 microM‐vesamicol has no detectable postjunctional effect. However, when vesamicol was included in the Tyrode and the hypertonic solutions the increase in quantal size was blocked. This is further evidence that the large quanta are produced by the release of more ACh per quantum. 8. Even when added after the hypertonic treatment, vesamicol soon decreased quantal size back to the normal level. Two other inhibitors of active ACh uptake into vesicles, tetraphenylboron (TPB) and hexanitrodiphenylamine (HNPA) also decreased quantal size after hypertonic treatment, apparently by a presynaptic action. This suggests that the additional ACh that produces large miniatures may be incorporated into the quanta shortly before release.(ABSTRACT TRUNCATED AT 400 WORDS)
The effect of amiloride on the resting potential and the electrical constants of frog skeletal muscle fibres.
Authors: Estrada F , Sanchez J A
Published: December 2014

1. The effects of amiloride on the membrane potential of frog skeletal muscle fibres were investigated with a single intracellular microelectrode. Two microelectrode current‐ and voltage‐clamp experiments were also performed to determine the effects of amiloride on the electrical constants and membrane current near the resting potential. 2. Amiloride reversibly hyperpolarized muscle fibres up to ca 12 mV in 2.5 mM‐K+, in a concentration‐dependent manner, with a half‐maximum effect at 0.2 mM. Amiloride (0.4 mM) also significantly increased the membrane resistance of muscle fibres. 3. The effects of amiloride were consistent with the classical theory of the resting potential and could be described by assuming that it removes the Na+ permeability factor in the Goldman‐Hodgkin‐Katz equation for [K+]o > or = 2.5 mM. 4. Replacement of [Na+]o by N‐methyl‐glucamine, choline or Mg2+ produced smaller effects on the resting potential and on membrane resistance than those induced by amiloride. 5. It is concluded that an amiloride‐sensitive poorly selective conductance continuously depolarizes the cellular membrane thus playing a role in the resting potential of frog skeletal muscle.
Pharmacological properties and H+ sensitivity of excitatory amino acid receptor channels in rat cerebellar granule neurones.
Authors: Traynelis S F , Cull‐Candy S G
Published: December 2014

1. N‐Methyl‐D‐aspartate (NMDA), alpha‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionate (AMPA), and kainate receptor channels have been examined in rat cerebellar granule neurones with whole‐cell and single‐channel patch‐clamp methods. The whole‐cell peak and steady‐state aspartate and NMDA currents were reversibly inhibited by extracellular protons; the IC50 (concentration producing half‐maximal inhibition) for the full H+ inhibition curve for NMDA receptors corresponded to pH 7.3, near to physiological pH. (S)‐AMPA and kainate whole‐cell currents were inhibited by protons with IC50 values that corresponded to pH 6.3 and 5.7, respectively; these receptors were, however, insensitive to H+ concentrations that inhibited NMDA receptor responses. 2. Proton inhibition of the NMDA, AMPA and kainate receptor‐mediated responses was voltage insensitive, and did not involve a shift in reversal potential. 3. The EC50 (concentration producing half‐maximal effect) for aspartate calculated from the whole‐cell dose‐response curve was similar at pH 6.8 and 7.6 (mean 11.2 microM). Although the EC50 for glycine potentiation of the aspartate response was marginally increased from 273 nM at pH 7.6 to 373 nM at pH 6.8, H+ inhibition was not overcome by up to 1 mM‐external glycine. Inhibiting concentrations of H+ appropriate for AMPA and kainate receptors did not markedly alter the EC50 values determined for (S)‐AMPA (3.4 microM) and kainate (114 microM) at pH 7.2. 4. Treatment of neurones with N‐ethylmaleimide, iodoacetic acid, dithiothretiol or diethyl pyrocarbonate did not influence proton inhibition of NMDA receptor responses. However, treatment with diethyl pyrocarbonate, which potentiated aspartate responses, appeared to reduce the effectiveness of Zn2+ inhibition of NMDA receptors. 5. Desensitization of whole‐cell NMDA and (S)‐AMPA currents was studied with ionophoretic application of agonist to the cell soma. Whole‐cell aspartate currents desensitized rapidly, irrespective of the glycine concentration. Increased H+ concentrations did not detectably alter the ratio of peak/steady‐state current, or the time constants describing the onset of, or recovery from, desensitization. The time constant describing desensitization of (S)‐AMPA‐induced whole‐cell currents also appeared unchanged by inhibiting pH (6.2). 6. The amplitudes of aspartate‐ or NMDA‐activated single‐channel multiple conductance levels were unchanged by decreasing the pH to 6.8.(ABSTRACT TRUNCATED AT 400 WORDS)
Characterization of Incandescent Particles Emitted by a Cut-Off Grinder During Decommissioning Operations for Evaluating Filter Degradation
Authors: Marchal Pierre , Porcheron Emmanuel , Grehan Gérard , Lafanechere Luc , Walter Jonathan , Gelain Thomas
Published: December 2014

The use of mechanical or thermal cutting tools when decommissioning nuclear facilities generates a lot of incandescent particles. These particles may represent a deterioration risk of the containment barriers associated with a potential fire hazard. The aim of this study is to characterize, in terms of temperature, diameter, and velocity, the incandescent particles emitted by a wheel grinder and to follow these parameters all along their path from emission point to their impact on the air filter. The characteristics of the particles correlated with a possible loss of filter efficiency should identify which particles degrade the filter. All the measurement techniques used to experimentally characterize the incandescent particles are presented in this article. Particles are characterized in terms of diameter by microscope visualizations. The particle velocity is measured with a high-speed camera using the particle tracking velocimetry (PTV) technique. An adaptation of a commercial monochromatic pyrometer is achieved to measure the temperature of the in-flight particles in a specific configuration. All of these techniques have been implemented on an experimental facility reproducing representative conditions of the cutting processes realized during dismantling operations. Both a global and a local approach to filter degradation are used to investigate the filter. The decontamination factor of a high efficiency particle air (HEPA) filter is measured, and detailed visualizations of the filter fiber deteriorations are obtained using a scanning electron microscope (SEM).
State of Charge Estimator Design for a Gas Charged Hydraulic Accumulator
Authors: Pfeffer Andreas , Glück Tobias , Kemmetmüller Wolfgang , Kugi Andreas
Published: December 2014

The gas charged hydraulic accumulators under consideration are used as energy storage devices in automotive hydraulic hybrid systems. The knowledge of the state of charge (SOC) is of utmost importance for an efficient energy management of the hybrid drive-train. Since the direct measurement of the SOC is difficult and costly, an SOC estimator design is presented based on a mathematical model of the gas charged hydraulic accumulator. Two different SOC estimation strategies, a signal-based approach and an Extended Kalman-filter, are presented and compared with each other. The performance of the estimators is validated by means of measurement results of a test driving cycle.
Precision Control of Piezoelectric Ultrasonic Motor for Myringotomy With Tube Insertion
Authors: Kiong Tan Kok , Liang Wenyu , Huang Sunan , Pham Le Phuong , Chen Silu , Wee Gan Chee , Yee Lim Hsueh
Published: December 2014

The current treatment of otitis media with effusion (OME) when medication fails is to surgically insert a grommet tube in the tympanic membrane. A novel precision surgical device has been developed, which allows tube insertion to be accomplished in an office setting. The device leverages on a piezoelectric ultrasonic motor (USM) stage to facilitate the motion sequences for the procedures. The core engine of the device is in the USM motion controller to achieve the high precision, fast response, and repeatability necessary to allow these medical procedures to be efficiently and successfully done with minimum trauma to the patient. This paper focuses on the controller design for the USM to meet the unique set of specifications to apply the surgical device optimally on patient with OME. A model of the USM is first built and identified. A proportional-integral-derivative (PID) controller is used as the main tracking controller with the parameters derived optimally using an linear-quadratic regulator (LQR)-assisted tuning approach. A sign function compensator acts to remove nonlinear dynamics due mainly to friction and a sliding mode controller further rejects remnant uncertainty and disturbance. The experimental results show that the constituent control components fulfill their respective functions well, and collectively, the composite controller is effective toward delivering the level of control performance to meet the objectives for the medical procedures.
A rapid antimicrobial susceptibility test based on single-cell morphological analysis
Authors: Choi Jungil , Yoo Jungheon , Lee Mincheol , Kim Eun-Geun , Lee Ji Soo , Lee Seungok , Joo Seik , Song Sang Hoon , Kim Eui-Chong , Lee Jung Chan , Kim Hee Chan , Jung Yong-Gyun , Kwon Sunghoon
Published: December 2014

An antimicrobial susceptibility test rapidly identifies bacterial response to drugs based on imaged morphology of single cells.
Wide-field computational imaging of pathology slides using lens-free on-chip microscopy
Authors: Greenbaum Alon , Zhang Yibo , Feizi Alborz , Chung Ping-Luen , Luo Wei , Kandukuri Shivani R. , Ozcan Aydogan
Published: December 2014

Lens-free holographic microscopy provides wide-field images with 3D focus adjustment of pathology slides for high-throughput and cost-effective human disease diagnostics.
ER-Mitochondrial Communication Gets Stressful
Authors: Erbay Ebru
Published: December 2014

An increase in contacts between the endoplasmic reticulum and mitochondria with a concomitant influx of calcium ions into liver cells may contribute to obesity-induced metabolic syndrome.
Checkpoint Therapy to the Rescue
Authors: Faltas Bishoy M.
Published: December 2014

Nivolumab had substantial activity and was safe in patients with heavily treated relapsed or refractory Hodgkin’s lymphoma.
T Cells Through the Age(s)
Authors: Maus Marcela V.
Published: December 2014

T cell subset distribution throughout the human life span depends on differentiation state and tissue localization.
Sprouting Neurological Function
Authors: Nishijima Daniel K.
Published: December 2014

Blocking the action of a nerve growth inhibitor that accumulates after spinal cord injury promotes better recovery of neural function.
Measurement of Phenotype and Absolute Number of Circulating Heparin-Binding Hemagglutinin, ESAT-6 and CFP-10, and Purified Protein Derivative Antigen-Specific CD4 T Cells Can Discriminate Active from Latent Tuberculosis Infection
Authors: Hutchinson Paul , Barkham Timothy M. S. , Tang Wenying , Kemeny David M. , Chee Cynthia Bin-Eng , Wang Yee T.
Published: December 2014

The tuberculin skin test (TST) and interferon gamma (IFN-γ) release assays (IGRAs) are used as adjunctive tests for the evaluation of suspected cases of active tuberculosis (TB). However, a positive test does not differentiate latent from active TB. We investigated whether flow cytometric measurement of novel combinations of intracellular cytokines and surface makers on CD4 T cells could differentiate between active and latent TB after stimulation withMycobacterium tuberculosis-specific proteins. Blood samples from 60 patients referred to the Singapore Tuberculosis Control Unit for evaluation for active TB or as TB contacts were stimulated with purified protein derivative (PPD), ESAT-6 and CFP-10, or heparin-binding hemagglutinin (HBHA). The CD4 T cell cytokine response (IFN-γ, interleukin-2 [IL-2], interleukin-17A [IL-17A], interleukin-22 [IL-22], granulocyte-macrophage colony-stimulating factor [GM-CSF], and tumor necrosis factor alpha [TNF-α]) and surface marker expression (CD27, CXCR3, and CD154) were then measured. We found that the proportion of PPD-specific CD4 T cells, defined as CD154+TNF-α+cells that were negative for CD27 and positive for GM-CSF, gave the strongest discrimination between subjects with latent and those with active TB (area under the receiver operator characteristic [ROC] curve of 0.9277;P< 0.0001). Also, the proportions and absolute numbers of HBHA-specific CD4 T cells were significantly higher in those with latent TB infection, particularly CD154+TNF-α+IFN-γ+IL-2+and CD154+TNF-α+CXCR3+. Finally, we found that the ratio of ESAT-6- and CFP-10-responding to HBHA-responding CD4 T cells was significantly different between the two study populations. In conclusion, we found novel markers ofM. tuberculosis-specific CD4 cells which differentiate between active and latent TB.
Seroprevalence of Cytomegalovirus among Children 1 to 5 Years of Age in the United States from the National Health and Nutrition Examination Survey of 2011 to 2012
Authors: Lanzieri Tatiana M. , Kruszon-Moran Deanna , Amin Minal M. , Bialek Stephanie R. , Cannon Michael J. , Carroll Margaret D. , Dollard Sheila C.
Published: December 2014

Cytomegalovirus (CMV) seroprevalence among U.S. children 1 to 5 years old was assessed in the National Health and Nutrition Examination Survey of 2011 to 2012. The overall seroprevalence (95% confidence interval) of IgG was 20.7% (14.4 to 28.2%), that of IgM was 1.1% (0.4 to 2.4%), and that of low IgG avidity was 3.6% (1.7 to 6.6%), corresponding to a 17.3% (10.1 to 26.7%) prevalence of recent infection among IgG-positive children.
Tsukamurella pulmonis Bloodstream Infection Identified by
secA1
Gene Sequencing
Authors: Pérez del Molino Bernal Inmaculada C. , Cano María E. , García de la Fuente Celia , Martínez-Martínez Luis , López Mónica , Fernández-Mazarrasa Carlos , Agüero Jesús
Published: December 2014

Recurrent bloodstream infections caused by a Gram-positive bacterium affected an immunocompromised child.
Tsukamurella pulmonis
was the microorganism identified by
secA1
gene sequencing. Antibiotic treatment in combination with removal of the subcutaneous port healed the patient.
Molecular Epidemiology and Genetic Diversity of Fluoroquinolone-Resistant Escherichia coli Isolates from Patients with Community-Onset Infections in 30 Chinese County Hospitals
Authors: Zhao Lina , Zhang Jing , Zheng Beiwen , Wei Zeqing , Shen Ping , Li Sujuan , Li Lanjuan , Xiao Yonghong
Published: December 2014

The high frequency of fluoroquinolone resistance in
Escherichia coli
is a feature of clinical bacteriology in China, where the molecular epidemiology and genetic characteristics of this resistance in county hospitals remain unclear. A total of 590 nonduplicate
E. coli
isolates from 30 county hospitals located across seven Chinese regions were examined for plasmid-mediated quinolone resistance (PMQR) genes and mutations in quinolone resistance-determining regions (QRDRs). Multilocus sequence typing (MLST) and phylogenetic analysis of fluoroquinolone-resistant isolates were used to determine their genetic relatedness. The ciprofloxacin resistance rate of community-onset
E. coli
was 51.2%, and at least one PMQR gene was carried by 220 (37.3%) isolates. These included
qnr
(3.7%),
aac(6
′
)-Ib-cr
(19.7%),
qepA
(14.4%), and
oqxAB
(3.8%). Two novel
oqxB
mutants were identified and named
oqxB20
and
oqxB29
. From 60 sequence types (STs) isolated, 5 novel STs (ST4499 to ST4503) were identified. ST1193 (7.9%) was the second most abundant ST among fluoroquinolone-resistant isolates (ST131 was the most common, with 14.6%), and this is the first report of it in China. This is also the first report of ST2115 and ST3014 isolates from human samples. Ciprofloxacin-resistant
E. coli
isolates fell mainly into phylogroups B2 and D. The rates of fluoroquinolone resistance and the prevalence of PMQR genes in community-onset
E. coli
isolates from Chinese county hospitals were high. The wide-ranging molecular epidemiology of
E. coli
isolates from scattered locations across China indicates that fluoroquinolone resistance evolved from different sources.
Hepatitis C Virus Genotype 7, a New Genotype Originating from Central Africa
Authors: Murphy Donald G. , Sablon Erwin , Chamberland Jasmine , Fournier Eric , Dandavino Raymond , Tremblay Cécile L.
Published: December 2014

We report a new hepatitis C virus (HCV) genotype identified in patients originating from the Democratic Republic of Congo. The prototype QC69 virus is shown to be a new lineage distinct from genotypes 1 to 6. Three additional patients were also found to be infected by a virus from this lineage, confirming its circulation in humans. We propose that these viruses be classified into HCV genotype 7.
Proposing an Empirically Justified Reference Threshold for Blood Culture Sampling Rates in Intensive Care Units
Authors: Karch André , Castell Stefanie , Schwab Frank , Geffers Christine , Bongartz Hannah , Brunkhorst Frank M. , Gastmeier Petra , Mikolajczyk Rafael T.
Published: December 2014

Early and appropriate blood culture sampling is recommended as a standard of care for patients with suspected bloodstream infections (BSI) but is rarely taken into account when quality indicators for BSI are evaluated. To date, sampling of about 100 to 200 blood culture sets per 1,000 patient-days is recommended as the target range for blood culture rates. However, the empirical basis of this recommendation is not clear. The aim of the current study was to analyze the association between blood culture rates and observed BSI rates and to derive a reference threshold for blood culture rates in intensive care units (ICUs). This study is based on data from 223 ICUs taking part in the German hospital infection surveillance system. We applied locally weighted regression and segmented Poisson regression to assess the association between blood culture rates and BSI rates. Below 80 to 90 blood culture sets per 1,000 patient-days, observed BSI rates increased with increasing blood culture rates, while there was no further increase above this threshold. Segmented Poisson regression located the threshold at 87 (95% confidence interval, 54 to 120) blood culture sets per 1,000 patient-days. Only one-third of the investigated ICUs displayed blood culture rates above this threshold. We provided empirical justification for a blood culture target threshold in ICUs. In the majority of the studied ICUs, blood culture sampling rates were below this threshold. This suggests that a substantial fraction of BSI cases might remain undetected; reporting observed BSI rates as a quality indicator without sufficiently high blood culture rates might be misleading.