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排序方式: 共有253条查询结果,搜索用时 15 毫秒
41.
Local neurons play key roles in the mammalian olfactory bulb 总被引:1,自引:0,他引:1
Armen Saghatelyan Alan Carleton Samuel Lagier Antoine de Chevigny Pierre-Marie Lledo 《Journal of Physiology》2003,97(4-6):517-528
Over the past few decades, research exploring how the brain perceives, discriminates, and recognizes odorant molecules has received a growing interest. Today, olfaction is no longer considered a matter of poetry. Chemical senses entered the biological era when an increasing number of scientists started to elucidate the early stages of the olfactory pathway. A combination of genetic, biochemical, cellular, electrophysiological and behavioral methods has provided a picture of how odor information is processed in the olfactory system as it moves from the periphery to higher areas of the brain. Our group is exploring the physiology of the main olfactory bulb, the first processing relay in the mammalian brain. From different electrophysiological approaches, we are attempting to understand the cellular rules that contribute to the synaptic transmission and plasticity at this central relay. How olfactory sensory inputs, originating from the olfactory epithelium located in the nasal cavity, are encoded in the main olfactory bulb remains a crucial question for understanding odor processing. More importantly, the persistence of a high level of neurogenesis continuously supplying the adult olfactory bulb with newborn local neurons provides an attractive model to investigate how basic olfactory functions are maintained when a large proportion of local neurons are continuously renewed. For this purpose, we summarize the current ideas concerning the molecular mechanisms and organizational strategies used by the olfactory system to encode and process information in the main olfactory bulb. We discuss the degree of sensitivity of the bulbar neuronal network activity to the persistence of this high level of neurogenesis that is modulated by sensory experience. Finally, it is worth mentioning that analyzing the molecular mechanisms and organizational strategies used by the olfactory system to transduce, encode, and process odorant information in the olfactory bulb should aid in understanding the general neural mechanisms involved in both sensory perception and memory. Due to space constraints, this review focuses exclusively on the olfactory systems of vertebrates and primarily those of mammals. 相似文献
42.
Escherichia coli accumulates K+ by means of multiple uptake systems of which Kup is the major transport system at acidic pH. In cells grown under fermentative conditions at pH 5.5, K+ influx by a wild-type strain upon hyper-osmotic stress at pH 5.5 was accompanied by a marked decrease in H+ efflux, with a 1:1 ratio of K+ to H+ fluxes. This was observed with cells treated with N,N'-dicyclohexylcarbodiimide. Similar results with a mutant defective in Kdp and TrkA but with a functional Kup system but not in a mutant defective in Kdp and Kup but having an active TrkA system suggest that Kup operates as a H+ -K+ -symporter. 相似文献
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World Journal of Microbiology and Biotechnology - Karst caves, considering to be the “arks” of biodiversity, often contain high levels of endemism. In the present study, the... 相似文献
46.
Boris A. Feniouk Alberto Rebecchi Sofie Anefors Armen Y. Mulkidjanian Wolfgang Junge B. Andrea Melandri 《BBA》2007,1767(11):1319-1330
H+-FOF1-ATP synthase couples proton flow through its membrane portion, FO, to the synthesis of ATP in its headpiece, F1. Upon reversal of the reaction the enzyme functions as a proton pumping ATPase. Even in the simplest bacterial enzyme the ATPase activity is regulated by several mechanisms, involving inhibition by MgADP, conformational transitions of the ε subunit, and activation by protonmotive force. Here we report that the Met23Lys mutation in the γ subunit of the Rhodobacter capsulatus ATP synthase significantly impaired the activation of ATP hydrolysis by protonmotive force. The impairment in the mutant was due to faster enzyme deactivation that was particularly evident at low ATP/ADP ratio. We suggest that the electrostatic interaction of the introduced γLys23 with the DELSEED region of subunit β stabilized the ADP-inhibited state of the enzyme by hindering the rotation of subunit γ rotation which is necessary for the activation. 相似文献
47.
Armen E. Aghajanyan Artur A. Hambardzumyan Anichka S. Hovsepyan Rafael A. Asaturian Andranik A. Vardanyan Ashot A. Saghiyan 《Pigment cell & melanoma research》2005,18(2):130-135
Melanins are widely used in medicine, pharmacology, cosmetics and other fields. Although several technologies for the purification of water‐insoluble dioxyphenylalanine (DOPA) melanins have been described, a source of water‐soluble melanin is highly desirable. Here we describe an effective procedure for the isolation and purification of water‐soluble melanin using the culture medium of Bacillus thuringiensis subsp. galleriae strain K1. Water‐soluble melanin from this organism has an isoelectric point (pI = 3.0–3.2) and was purified optimally by adsorbtion using the IA‐1r resin and elution as a concentrated solution. The purified melanin obtained exhibited a similar infra‐red absorbtion spectrum to synthetic melanin and contained quinolic and phenolic structures and an amino acid content of around 20% after acid hydrolysis. The molecular weight of the purified melanin determined by SDS‐PAGE was 4 kDa and the electromagnetic spin resonance spectrum of the purified microbial melanin was a slightly asymmetric singlet without hyperfine structure with about 7 Gauss width of the line between points of the maximum incline and g = 2.006. The concentration of paramagnetic centers in melanin is 0.21 × 1018 spin/g. The results obtained provide a rapid, simple and inexpensive method for the large scale purification of water soluble melanin that may have widespread applications. 相似文献
48.
Kirakosyan G Trchounian K Vardanyan Z Trchounian A 《Cell biochemistry and biophysics》2008,51(1):45-50
The SH-groups in Escherichia coli membrane vesicles, prepared from cells grown in fermentation conditions on glucose at slightly alkaline pH, have a role in the F0F1-ATPase operation. The changes in the number of these groups by ATP are observed under certain conditions. In this study, copper ions (Cu2+) in concentration of 0.1 mM were shown to increase the number of SH-groups in 1.5- to 1.6-fold independent from K+ ions, and the suppression of the increased level of SH-groups by ATP was determined for Cu2+ in the presence of K+. Moreover, the increase in the number of SH-groups by Cu2+ was absent as well as the inhibition in ATP-dependent increasing SH-groups number by Cu2+ lacked when vesicles were treated with N-ethylmaleimide (NEM), specific thiol-reagent. Such an effect was not observed with zinc (Zn2+), cobalt (Co2+), or Cu+ ions. The increased level of SH-groups was observed in the hycE or hyfR mutants with defects in hydrogenases 3 or 4, whereas the ATP-dependent increase in the number of these groups was determined in hycE not in hyfR mutants. Both changes in SH-groups number disappeared in the atp or hyc mutants deleted for the F0F1-ATPase or hydrogenase 3 (no activity of hydrogenase 4 was detected in the hyc mutant used). A direct effect of Cu2+ but not Cu+ on the F0F1-ATPase is suggested to lead to conformational changes or damaging consequences, increasing accessible SH-groups number and disturbing disulfide-dithiol interchange within a protein-protein complex, where this ATPase works with K+ uptake system or hydrogenase 4 (Hyd-4); breaks in disulfides are not ruled out. 相似文献
49.
Destaye M. Moore Justin Karlin Sergio González-Barrera Armen Mardiros Michael Lisby Ana Doughty Jennifer Gilley Rodney Rothstein Errol C. Friedberg Paula L. Fischhaber 《Nucleic acids research》2009,37(19):6429-6438
In the yeast Saccharomyces cerevisiae, the Rad1–Rad10 protein complex participates in nucleotide excision repair (NER) and homologous recombination (HR). During HR, the Rad1–Rad10 endonuclease cleaves 3′ branches of DNA and aberrant 3′ DNA ends that are refractory to other 3′ processing enzymes. Here we show that yeast strains expressing fluorescently labeled Rad10 protein (Rad10-YFP) form foci in response to double-strand breaks (DSBs) induced by a site-specific restriction enzyme, I-SceI or by ionizing radiation (IR). Additionally, for endonuclease-induced DSBs, Rad10-YFP localization to DSB sites depends on both RAD51 and RAD52, but not MRE11 while IR-induced breaks do not require RAD51. Finally, Rad10-YFP colocalizes with Rad51-CFP and with Rad52-CFP at DSB sites, indicating a temporal overlap of Rad52, Rad51 and Rad10 functions at DSBs. These observations are consistent with a putative role of Rad10 protein in excising overhanging DNA ends after homology searching and refine the potential role(s) of the Rad1–Rad10 complex in DSB repair in yeast. 相似文献
50.
Karina Galoian Sean Scully George McNamara Patrick Flynn Armen Galoyan 《Neurochemical research》2009,34(12):2117-2121
Proline rich polypeptide (PRP-1) produced by neurosecretory cells of the hypothalamus is one of the fragments of neurophysin-vasopressin-associated
glycoprotein. The primary structure of the neuropeptide PRP-1 isolated from neurosecretory granules of bovine neurohypophysis.
We investigated PRP-1 action on chondrosarcoma, the second most common malignancy in bone, which primarily affects the cartilage
cells. This deadly disease does not have any effective treatment. Earlier we demonstrated MYC oncogene inactivating effect
by 1 μg/ml concentration brain PRP-1 In the present study we observed reduced viable sarcoma JJ012 cell numbers in comparison
with control (89% growth inhibition) when treated with low concentrations of PRP-1 (0.5–1 μg/ml). Higher concentrations did
not exhibit inhibitory effect. We assume that PRP-1 in low concentration impedes cell cycle progression. The fact that low
concentrations of PRP-1 abolished Myc activity prompts to think that the antitumorigenic effect of PRP-1 in low concentrations
is mediated through oncogene inactivation. 相似文献