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101.
Brief periods of electrical stimulation of cultured Xenopus spinal neurons resulted in a marked alteration in the turning responses of the growth cone induced by gradients of attractive or repulsive guidance cues. Netrin-1-induced attraction was enhanced, and the repulsion induced by myelin-associated glycoprotein (MAG) or myelin membrane fragments was converted to attraction. The effect required the presence of extracellular Ca(2+) during electrical stimulation and appeared to be mediated by an elevation of both cytoplasmic Ca(2+) and cAMP. Thus, electrical activity may influence the axonal path finding of developing neurons, and intermittent electrical stimulation may be effective in promoting nerve regeneration after injury. 相似文献
102.
GABA itself promotes the developmental switch of neuronal GABAergic responses from excitation to inhibition 总被引:25,自引:0,他引:25
GABA is the main inhibitory neurotransmitter in the adult brain. Early in development, however, GABAergic synaptic transmission is excitatory and can exert widespread trophic effects. During the postnatal period, GABAergic responses undergo a switch from being excitatory to inhibitory. Here, we show that the switch is delayed by chronic blockade of GABA(A) receptors, and accelerated by increased GABA(A) receptor activation. In contrast, blockade of glutamatergic transmission or action potentials has no effect. Furthermore, GABAergic activity modulated the mRNA levels of KCC2, a K(+)-Cl(-) cotransporter whose expression correlates with the switch. Finally, we report that GABA can alter the properties of depolarization-induced Ca(2+) influx. Thus, GABA acts as a self-limiting trophic factor during neural development. 相似文献
103.
The role of the target cell in neurotrophin-induced modifications of glutamatergic synaptic transmission was examined in cultured hippocampal neurons. Brain-derived neurotrophic factor (BDNF) induced rapid and persistent potentiation of evoked glutamate release when the postsynaptic neuron was glutamatergic, or excitatory (E-->E), but not when it was GABAergic, or inhibitory (E-->1). This target-specific action of BDNF was also found at divergent outputs of a single presynaptic neuron innervating both glutamatergic and GABAergic neurons, suggesting that individual terminals can be independently modified. Surprisingly, BDNF increased the frequency of miniature postsynaptic currents at both E-->E and E-->I, although it had no effect on evoked currents at E-->I. Finally, potentiation by neurotrophin-3 (NT-3) was also target specific. The selective effect at E-->E suggests that retrograde signaling by the postsynaptic target cell endows a localized presynaptic action of neurotrophins. 相似文献
104.
SJ Park HJ Moon BK Kang M Hong W Na JK Kim H Poo BK Park DS Song 《Journal of virology》2012,86(17):9548-9549
An avian-origin Korean H3N2 canine influenza virus (CIV) strain, designated A/canine/Korea/01/2007 (H3N2), was isolated from nasal swabs of pet dogs exhibiting severe respiratory syndrome in 2007. In the present study, we report the first complete genome sequence containing 3' and 5' noncoding regions (NCRs) of H3N2 CIV, which will provide important insights into the molecular basis of pathogenesis, transmission, and evolution of CIV. 相似文献
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107.
Elevation of cytosolic Ca2+ level in the postsynaptic cell is critical for the induction of many forms of activity-dependent synaptic modulation. Based on our recent evidence that in muscle cells and fibroblasts constitutive exocytosis is increased by elevating cytosolic Ca2+ levels, we hypothesize that Ca2+ -dependent exocytosis at the postsynaptic site may provide a mechanism for a localized, activitt-dependent synaptic modulation. 1994 John Wiley & Sons, Inc. 相似文献
108.
Small, isolated populations often experience increased inbreeding and decreased heterozygosity, which increases the potential risk of inbreeding depression. The relationship between inbreeding and sperm health is well-documented in a variety of taxa, but has yet to be explored in amphibians. The dusky gopher frog, Lithobates sevosus, is a critically endangered species with years of documented inbreeding and low genetic variability as a consequence of isolation and population size reduction. This study investigated the effects of inbreeding on sperm quality in captive L. sevosus using an outbred, sister species (Lithobates pipiens) as a standard for comparison. We found L. sevosus to have severely reduced sperm quality in terms of total motility, forward progressive motility, concentration, and viability. Additionally, we observed a significant, negative relationship between total sperm motility and mean kinship within captive-bred individuals. These data serve to enhance our understanding of the role inbreeding plays in amphibians, and to provide valuable insight into new risk factors declining amphibian populations may face. 相似文献
109.
Poo Jeslyn S. T. Choo Celine Y. L. Hiong Kum C. Boo Mel V. Wong Wai P. Chew Shit F. Ip Yuen K. 《Coral reefs (Online)》2020,39(2):361-374
Coral Reefs - Despite living in oligotrophic tropical waters, giant clams can grow to large sizes because they live in symbiosis with extracellular phototrophic dinoflagellates (zooxanthellae) and... 相似文献
110.
Hui Lu Hyungju Park Mu-Ming Poo 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2014,369(1633)
In acute hippocampal slices, we found that the presence of extracellular brain-derived neurotrophic factor (BDNF) is essential for the induction of spike-timing-dependent long-term potentiation (tLTP). To determine whether BDNF could be secreted from postsynaptic dendrites in a spike-timing-dependent manner, we used a reduced system of dissociated hippocampal neurons in culture. Repetitive pairing of iontophoretically applied glutamate pulses at the dendrite with neuronal spikes could induce persistent alterations of glutamate-induced responses at the same dendritic site in a manner that mimics spike-timing-dependent plasticity (STDP)—the glutamate-induced responses were potentiated and depressed when the glutamate pulses were applied 20 ms before and after neuronal spiking, respectively. By monitoring changes in the green fluorescent protein (GFP) fluorescence at the dendrite of hippocampal neurons expressing GFP-tagged BDNF, we found that pairing of iontophoretic glutamate pulses with neuronal spiking resulted in BDNF secretion from the dendrite at the iontophoretic site only when the glutamate pulses were applied within a time window of approximately 40 ms prior to neuronal spiking, consistent with the timing requirement of synaptic potentiation via STDP. Thus, BDNF is required for tLTP and BDNF secretion could be triggered in a spike-timing-dependent manner from the postsynaptic dendrite. 相似文献