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131.
NFATc-mediated gene expression constitutes a critical step during neuronal development and synaptic plasticity. Although considerable information is available regarding the activation and functionality of specific NFATc isoforms, in neurons little is known about how sensitive NFAT nuclear translocation is to specific patterns of electrical activity. Here we used high-speed fluo-4 confocal imaging to monitor action potential (AP)-induced cytosolic Ca2+ transients in rat sympathetic neurons. We have recorded phasic and repetitive AP patterns, and corresponding Ca2+ transients initiated by either long (100-800 ms) current-clamp pulses, or single brief (2 ms) electrical field stimulation. We address the functional consequences of these AP and Ca2+ transient patterns, by using an adenoviral construct to express NFATc1-CFP and evaluate NFATc1-CFP nuclear translocation in response to specific patterns of electrical activity. Ten Hertz trains stimulation induced nuclear translocation of NFATc1, whereas 1 Hz trains did not. However, 1 Hz train stimulation did result in NFATc1 translocation in the presence of 2 mM Ba2+, which inhibits M-currents and promotes repetitive firing and the accompanying small (approximately 0.6 DeltaF/F0) repetitive and summating Ca2+ transients. Our results demonstrate that M-current inhibition-mediated spike frequency facilitation enhances cytosolic Ca2+ signals and NFATc1 nuclear translocation during trains of low frequency electrical stimulation. 相似文献
132.
Guan S Ma S Zhu Y Ge R Wang Q Wang JH 《Biochemical and biophysical research communications》2006,345(1):175-180
Cerebellum is involved in the motion coordination and working memory, to which the programming of sequential spikes at Purkinje cells is essential. It is not clear about the intrinsic mechanisms underlying spike capacity and timing precision as well as their postnatal maturation. We investigated the programming and intrinsic property of sequential spikes at Purkinje neurons during postnatal development by whole-cell recording in cerebellar slices. Cerebellar Purkinje neurons demonstrate the increasing of spike capacity and timing precision, as well as the lowering of refractory periods and threshold potentials during the postnatal maturation. In addition, the correlation between spike parameters and intrinsic properties converts to be more linear. This postnatal plasticity of neuronal intrinsic properties improves the timing precision and capacity of spike programming at cerebellar Purkinje neurons. 相似文献
133.
A procedure for creating and imaging capillary bridges in slit-pore geometry is presented. High aspect ratio hydrophobic pillars are fabricated and functionalized to render their top surfaces hydrophilic. The combination of a physical feature (the pillar) with a chemical boundary (the hydrophilic film on the top of the pillar) provides both a physical and chemical heterogeneity that pins the triple contact line, a necessary feature to create stable long but narrow capillary bridges. The substrates with the pillars are attached to glass slides and secured into custom holders. The holders are then mounted onto four axis microstages and positioned such that the pillars are parallel and facing each other. The capillary bridges are formed by introducing a fluid in the gap between the two substrates once the separation between the facing pillars has been reduced to a few hundred micrometers. The custom microstage is then employed to vary the height of the capillary bridge. A CCD camera is positioned to image either the length or the width of the capillary bridge to characterize the morphology of the fluid interface. Pillars with widths down to 250 µm and lengths up to 70 mm were fabricated with this method, leading to capillary bridges with aspect ratios (length/width) of over 1001. 相似文献
134.
Vladimir Kosonogov Author vitae 《Journal of electromyography and kinesiology》2011,21(5):742-745
According to the mirror neurons data there exist areas in the premotor cortex that are activated both during action perception and action execution. It was hypothesized that posture maintenance would be impaired by simultaneous action perception in concordance with cognitive dissonance theory. A test was conducted during which 23 neurologically normal humans were to maintain their posture erect on the forceplate and to listen to the action-related sentences. Tests of differences and Friedman analysis of variance proved that listening to sentences that describe different actions and movements in the first and the third person impairs postural control in comparison with listening to sentences that describe objects of nature and everyday life. 相似文献
135.
Simultaneous electrophysiological and fluorescent imaging recording methods were used to study the role of changes of membrane potential or current in regulating the intracellular calcium concentration. Changing environmental conditions, such as the light-dark cycle, can modify neuronal and neural network activity and the expression of a family of circadian clock genes within the suprachiasmatic nucleus (SCN), the location of the master circadian clock in the mammalian brain. Excitatory synaptic transmission leads to an increase in the postsynaptic Ca2+ concentration that is believed to activate the signaling pathways that shifts the rhythmic expression of circadian clock genes. Hypothalamic slices containing the SCN were patch clamped using microelectrodes filled with an internal solution containing the calcium indicator bis-fura-2. After a seal was formed between the microelectrode and the SCN neuronal membrane, the membrane was ruptured using gentle suction and the calcium probe diffused into the neuron filling both the soma and dendrites. Quantitative ratiometric measurements of the intracellular calcium concentration were recorded simultaneously with membrane potential or current. Using these methods it is possible to study the role of changes of the intracellular calcium concentration produced by synaptic activity and action potential firing of individual neurons. In this presentation we demonstrate the methods to simultaneously record electrophysiological activity along with intracellular calcium from individual SCN neurons maintained in brain slices. 相似文献
136.
The action of a wide range of drugs effective on Ca2+ channels in animal tissues has been measured on Ca2+ channels open during the action potential of the giant-celled green alga,Chara corallina. Of the organic effectors used, only the 1,4-dihydropyridines were found to inhibit reversibly Ca2+ influx, including, unexpectedly, Bay K 8644 and both isomers of 202–791. Methoxyverapamil (D-600), diltiazem, and the diphenylbutylpiperidines,
fluspirilene and pimozide were found not to affect the Ca2+ influx. Conversely, bepridil greatly and irreversibly stimulated Ca2+ influx, and with time, stopped cytoplasmic streaming (which is sensitive to increases in cytoplasmic Ca2+). By apparently altering the cytoplasmic Ca2+ levels with various drugs, it was found that (with the exception of the inorganic cation, La3+) treatments likely to lead to an increase in cytoplasmic Ca2+ levels caused an increase in the rate of closure of the K+ channels. Similarly, treatments likely to lead to a decrease in cytoplasmic Ca2+ decreased the rate of K+ channel closure. The main effect of bepridil on the K+ channels was to increase the rate of voltage-dependent channel closure. The same effect was obtained upon increasing the
external concentration of Ca2+, but it is likely that this was due to effects on the external face of the K+ channel. Addition of any of the 1,4-dihydropyridines had the opposite effect on the K+ channels, slowing the rate of channel closure. They sometimes also reduced K+ conductance, but this could well be a direct effect on the K+ channel; high concentrations (50 to 100 μM) of bepridil also reduced K+ conductance. No effect of photon irradiance or of abscisic acid could be consistently shown on the K+ channels. These results indicate a control of the gating of K+ channels by cytoplasmic Ca2+, with increased free Ca2+ levels leading to an increased rate of K+-channel closure. As well as inhibiting Ca2+ channels, it is suggested that La3+ acts on a Ca2+-binding site of the K+ channel, mimicking the effect of Ca2+ and increasing the rate of channel closure. 相似文献
137.
Hiroshi Kawai 《Journal of plant research》1992,105(1):171-184
A flavin-like green autofluorescent substance is noticed to occur in one of the flagella of flagellated cells in the Phaeophyceae,
Chrysophyceae, Synurophyceae, Xanthophyceae and Prymnesiophyceae. In the phaeophycean swarmers the autofluorescence occurs
in the posterior flagellum throughout its length. It is considered to be involved in the photoreception of phototaxis, since
it almost always occurs in the swarmers which have a flagellar swelling and stigma and show phototaxis. In the phaeophycean
swarmers, the stigma is shown to act as a concave reflector mirror focusing the reflection light onto the flagellar swelling.
In the action spectrum studies, phaeophycean swarmers showed phototaxis between 370 and 520 nm, having two major peaks at
420 or 430 nm and 450 or 460 nm. Their responses were true phototactic and not photophobic. Rotation of the swarmer was shown
to be essential in the photoreception ofEctocarpus gametes.
Recipient of the Botanical Society Award for Young Scientists, 1991. 相似文献
138.
山楂和山楂叶中25种元素的含量 总被引:2,自引:0,他引:2
本文报导了用电感耦合等离子体发射光谱法测定山楂和山楂叶中25种元素的含量,并讨论其中某些元素与山楂、山楂叶的药效之间的关系。 相似文献
139.
140.
Voltage-clamp experiments were performed on single bovine adrenal fasciculata cells in short-term primary culture using either
standard (broken membrane) or perforated whole-cell patch clamp recording. The membrane current measured with the perforated
method was dominated by a very stable transient outward current. By contrast, the transient outward current recorded using
the standard method was unstable. The reversal potential of the transient outward current varied linearly with the logarithm
of [K+]
e
with a slope of 47 mV per decade. The onset of activation was sigmoidal and was fitted with a power function where n= 4. Time constants ranged from 1 to 4 msec with a maximum at −25 mV. The steady-state activation curve spanned the voltage
range −50 to +80 mV without reaching a clear maximum. During a pulse, the current decayed in a biexponential manner. Time
constants τ1 and τ2 were voltage-dependent and ranged from 50 to 200 msec respectively for a voltage step at +50 mV. The steady-state inactivation
was dependent on the conditioning pulse duration. Using short conditioning pulses (1.2 sec), the curve which spanned the voltage
range −40 to −20 mV, was 15 mV more positive than that obtained with longer conditioning pulses (60 sec). Time constants of
this ``very slow inactivation' process (τvs) determined for voltage steps at −60 and −50 mV were 15 and 10 sec respectively. A ``facilitation process' of the peak current
was observed when the duration or the amplitude of conditioning pulses were increased in the voltage range −100 to −50 mV.
Recovery from inactivation followed a biexponential time course which seemed a mixture of both inactivation processes. In
some experimental conditions, isolated cells were able to produce overshooting action potentials. These results are discussed
in relation with the membrane electrogenesis of this cell type.
Received: 14 November 1994/Revised: 24 October 1995 相似文献