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221.
In order to genotype hybrid genomes of distant asymmetric somatic hybrids, we synthesized hybrid calli and plants via PEG-mediated
protoplast fusion between recipient tall fescue (Festuca. arundinacea Schreb.) and donor wheat (Triticum aestivum L.). Seventeen and 25 putative hybrid clones were produced from the fusion combinations I and II, each with the donor wheat
protoplast treated by UV light for 30 s and 1 min, respectively. Isozyme and RAPD profiles confirmed that ten hybrid clones
were obtained from combination I and 19 from combination II. Out of the 29 hybrids, 12 regenerated hybrid plants with tall
fescue phenotype. Composition and methylation-variation of the nuclear and cytoplasmic genomes of some hybrids, either with
or without regenerative ability, were compared by genomic in situ hybridization, restriction fragment length polymorphism,
and DNA methylation-sensitive amplification polymorphism. Our results indicated that these selected hybrids all contained
introgressed nuclear and cytoplasmic DNA as well as obvious methylation variations compared to both parents. However, there
were no differences either in nuclear/cytoplasmic DNA or methylation degree between the regenerable and non-regenerable hybrid
clones. We conclude that both regeneration complementation and genetic material balance are crucial for hybrid plant regeneration. 相似文献
222.
Hu XT 《Molecular neurobiology》2007,35(1):95-112
Chronic exposure to psychostimulants induces neuro-adaptations in ion channel function of dopamine (DA)-innervated cells localized
within the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc). Although neuroplasticity in ion channel function is
initially found in drug-sensitized animals, it has recently been believed to underlie the withdrawal effects of cocaine, including
craving that leads to relapse in human addicts. Recent studies have also revealed remarkable differences in altered ion channel
activities between mPFC pyramidal neurons and medium spiny NAc neurons in cocaine-withdrawn animals. In response to psychostimulant
or certain “excitatory” stimuli, increased intrinsic excitability is found in mPFC pyramidal neurons, whereas decreased excitability
is observed in medium spiny NAc cells in drug-withdrawn animals compared to drug-free control animals. These changes in ion
channel function are modulated by interrupted DA/Ca2+ signaling with decreased DA D2 receptor function but increased D1 receptor signaling. More importantly, they are correlated
to behavioral changes in cocaine-withdrawn human addicts and sensitized animals. Based on growing evidence, researchers have
proposed that cocaine-induced neuro-adaptations in ion channel activity and DA/Ca2+ signaling in mPFC pyramidal neurons and medium spiny NAc cells may be the fundamental cellular mechanism underlying the cocaine
withdrawal effects observed in human addicts. 相似文献
223.
Feng XJ Shea-Brown E Greenwald B Kosut R Rabitz H 《Journal of computational neuroscience》2007,23(3):265-282
Deep brain stimulation (DBS) of the subthalamic nucleus, typically with periodic, high frequency pulse trains, has proven
to be an effective treatment for the motor symptoms of Parkinson’s disease (PD). Here, we use a biophysically-based model
of spiking cells in the basal ganglia (Terman et al., Journal of Neuroscience, 22, 2963–2976, 2002; Rubin and Terman, Journal of Computational Neuroscience, 16, 211–235, 2004) to provide computational evidence that alternative temporal patterns of DBS inputs might be equally effective as the standard
high-frequency waveforms, but require lower amplitudes. Within this model, DBS performance is assessed in two ways. First,
we determine the extent to which DBS causes Gpi (globus pallidus pars interna) synaptic outputs, which are burstlike and synchronized in the unstimulated Parkinsonian state, to cease their pathological
modulation of simulated thalamocortical cells. Second, we evaluate how DBS affects the GPi cells’ auto- and cross-correlograms.
In both cases, a nonlinear closed-loop learning algorithm identifies effective DBS inputs that are optimized to have minimal
strength. The network dynamics that result differ from the regular, entrained firing which some previous studies have associated
with conventional high-frequency DBS. This type of optimized solution is also found with heterogeneity in both the intrinsic
network dynamics and the strength of DBS inputs received at various cells. Such alternative DBS inputs could potentially be
identified, guided by the model-free learning algorithm, in experimental or eventual clinical settings.
Action Editor: Steven J. Schiff
Xiao-Jiang Feng and Eric Shea-Brown contributed equally to this work. 相似文献
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226.
The purpose of the study was to explore the mechanism underlying the enhanced subthalamic nucleus (STN) neural activity during exhausting exercise from the perspective of monoamine neurotransmitters and changes of their corresponding receptors. Rats were randomly divided into microdialysis and immunohistochemistry study groups. For microdialysis study, extracellular fluid of the STN was continuously collected with a microdialysis probe before, during and 90 min after one bout of exhausting exercise. Dopamine (DA) and 5-hydroxytryptamine (5-HT) levels were subsequently detected with high-performance liquid chromatography (HPLC). For immunohistochemistry study, the expression of DRD2 and HT2C receptors in the STN, before, immediately after and 90 min after exhaustion was detected through immunohistochemistry technique. Microdialysis study results showed that the extracellular DA and 5-HT neurotransmitters increased significantly throughout the procedure of exhausting exercise and the recovery period (P<0.05 or P<0.01). Immunohistochemistry study results showed that the expression levels of DRD2 and HT2C in the rat STN immediately after exhausting exercise and at the time point of 90 min after exhaustion were both higher than those of the rest condition, but the difference was not significant (P>0.05). Our results suggest that the increased extracellular DA and 5-HT in the STN might be one important factor leading to the enhanced STN neural activity and the development of fatigue during exhausting exercise. This study may essentially offer useful evidence for better understanding of the mechanism of the central type of exercise-induced fatigue. 相似文献
227.
Makoto Mogi Susumu Uji Hayato Yokoi Tohru Suzuki 《Development, growth & differentiation》2015,57(6):444-452
Circadian rhythms enable organisms to coordinate multiple physiological processes and behaviors with the earth's rotation. In mammals, the suprachiasmatic nuclei (SCN), the sole master circadian pacemaker, has entrainment mechanisms that set the circadian rhythm to a 24‐h cycle with photic signals from retina. In contrast, the zebrafish SCN is not a circadian pacemaker, instead the pineal gland (PG) houses the major circadian oscillator. The SCN of flounder larvae, unlike that of zebrafish, however, expresses per2 with a rhythmicity of daytime/ON and nighttime/OFF. Here, we examined whether the rhythm of per2 expression in the flounder SCN represents the molecular clock. We also examined early development of the circadian rhythmicity in the SCN and PG. Our three major findings were as follows. First, rhythmic per2 expression in the SCN was maintained under 24 h dark (DD) conditions, indicating that a molecular clock exists in the flounder SCN. Second, onset of circadian rhythmicity in the SCN preceded that in the PG. Third, both 24 h light (LL) and DD conditions deeply affected the development of circadian rhythmicity in the SCN and PG. This is the first report dealing with the early development of circadian rhythmicity in the SCN in fish. 相似文献
228.
We recently showed that inter-keratin disulfide bonding plays an important role in the assembly, organization, and dynamics of keratin intermediate filaments in skin keratinocytes. In particular, cysteine 367 located in the central α-helical rod domain of keratin 14 is necessary for the formation of a stable perinuclear network of keratin filaments (with type II partner keratin 5) in skin keratinocytes analyzed by static and live cell imaging. Here, we show that two additional cysteine residues located in the non-helical head domain of K14, Cys-4 and Cys-40, also participate in inter-keratin disulfide bonding and tandemly play a key role complementary to that of Cys-367 in the assembly, organization, and dynamics of keratin filaments in skin keratinocytes in primary culture. Analysis of K14 variants with single or multiple substitutions of cysteine residues points to a spatial and temporal hierarchy in how Cys-4/Cys-40 and Cys-367 regulate keratin assembly in vitro and filament dynamics in live keratinocytes in culture. Our findings substantiate the importance and complexity of a novel determinant, namely inter-keratin disulfide bonding, for the regulation of several aspects of keratin filaments in surface epithelia. 相似文献
229.
Reduced dopamine and glutamate neurotransmission in the nucleus accumbens of quinpirole‐sensitized rats hints at inhibitory D2 autoreceptor function
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230.