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991.
Egg activation and further embryo development require a sperm-induced intracellular Ca2+ signal at the time of fertilization. Prior to fertilization, the egg's Ca2+ machinery is therefore optimized. To this end, during oocyte maturation, the sensitivity, i.e. the Ca2+ releasing ability, of the inositol 1,4,5-trisphosphate receptor type 1 (IP3R1), which is responsible for most of this Ca2+ release, markedly increases. In this study, the recently discovered specific Polo-like kinase (Plk) inhibitor BI2536 was used to investigate the role of Plk1 in this process. BI2536 inactivates Plk1 in oocytes at the early stages of maturation and significantly decreases IP3R1 phosphorylation at an MPM-2 epitope at this stage. Moreover, this decrease in Plk1-dependent MPM-2 phosphorylation significantly lowers IP3R1 sensitivity. Finally, using in vitro phosphorylation techniques we identified T2656 as a major Plk1 site on IP3R1. We therefore propose that the initial increase in IP3R1 sensitivity during oocyte maturation is underpinned by IP3R1 phosphorylation at an MPM-2 epitope(s).  相似文献   
992.
The Dutch elm disease (DED) pathogen Ophiostoma novo-ulmi Buissm. elicited the production of H2O2 in cell suspension cultures of the resistant species Ulmus pumila L. This response was not observed in suspensions of the susceptible elm U. campestris Mill. H2O2 production started after a lag time of 30–40 min following inoculation, peaked between 4 and 6 h and lasted up to 24 h. Treatment of the suspensions with exogenously added H2O2 did not cause accumulation of the sesquiterpene phytoalexins mansonones nor of the coumarin scopoletin. Spore germination and growth of O. novo-ulmi were significantly delayed with different amounts of H2O2 (0.1–1 m M ). These results suggest that H2O2 production is an inducible defence response which may contribute to DED resistance by delaying the growth of the pathogen at the earliest stages of infection. Whether H2O2 is involved in other elm defence responses to the pathogen is presently unknown, but its production seems to be an independent event from phytoalexin formation.  相似文献   
993.
    
By controlling gene expression, DNA methylation contributes to key regulatory processes during plant development. Genomic methylation patterns are dynamic and must be properly maintained and/or re‐established upon DNA replication and active removal, and therefore require sophisticated control mechanisms. Here we identify direct interplay between the DNA repair factor DNA damage‐binding protein 2 (DDB2) and the ROS1‐mediated active DNA demethylation pathway in Arabidopsis thaliana. We show that DDB2 forms a complex with ROS1 and AGO4 and that they act at the ROS1 locus to modulate levels of DNA methylation and therefore ROS1 expression. We found that DDB2 represses enzymatic activity of ROS1. DNA demethylation intermediates generated by ROS1 are processed by the DNA 3′‐phosphatase ZDP and the apurinic/apyrimidinic endonuclease APE1L, and we also show that DDB2 interacts with both enzymes and stimulates their activities. Taken together, our results indicate that DDB2 acts as a critical regulator of ROS1‐mediated active DNA demethylation.  相似文献   
994.

Background and Aims

Cerradão (Brazilian woodland savannas) and seasonally dry forests (SDF) from southeastern Brazil occur under the same climate but are remarkably distinct in species composition. The objective of this study was to evaluate the role of soil origin in the initial growth and distribution of SDF and Cerradão species.

Methods

We conducted a greenhouse experiment growing Cerradão and SDF tree seedlings over their soil and the soil of the contrasting vegetation type. We evaluated soil nutrient availability and seedling survivorship, growth and leaf functional traits.

Results

Despite the higher nutrient availability in SDF soils, soil origin did not affect seedling survivorship. The three SDF species demonstrated home-soil advantage, enhanced growth with increasing soil nutrient availability and had higher growth rates than Cerradão species, even on Cerradão soils. Growth of Cerradão seedlings was not higher on Cerradão soil and, overall, was not positively correlated with soil nutrient availability.

Conclusions

SDF species are fast-growing species while Cerradão trees tend to be slow-growing species. Although savanna soil reduces growth of forest species, our findings suggest that soil chemical attributes, alone, does not exclude the occurrence of SDF seedlings in Cerradão and vice-versa.  相似文献   
995.
    
Transition models are an important framework that can be used to model longitudinal categorical data. They are particularly useful when the primary interest is in prediction. The available methods for this class of models are suitable for the cases in which responses are recorded individually over time. However, in many areas, it is common for categorical data to be recorded as groups, that is, different categories with a number of individuals in each. As motivation we consider a study in insect movement and another in pig behaviou. The first study was developed to understand the movement patterns of female adults of Diaphorina citri, a pest of citrus plantations. The second study investigated how hogs behaved under the influence of environmental enrichment. In both studies, the number of individuals in different response categories was observed over time. We propose a new framework for considering the time dependence in the linear predictor of a generalized logit transition model using a quantitative response, corresponding to the number of individuals in each category. We use maximum likelihood estimation and present the results of the fitted models under stationarity and non-stationarity assumptions, and use recently proposed tests to assess non-stationarity. We evaluated the performance of the proposed model using simulation studies under different scenarios, and concluded that our modeling framework represents a flexible alternative to analyze grouped longitudinal categorical data.  相似文献   
996.
Long-term molecular and cellular stability of human neural stem cell lines   总被引:7,自引:0,他引:7  
Human Neural Stem Cells (hNSCs) are excellent candidates for in vitro and in vivo molecular, cellular, and developmental research, and also for ex-vivo gene transfer and cell therapy in the nervous system. However, hNSCs are mortal somatic cells, and thus invariably enter an irreversible growth arrest after a finite number of cell divisions in culture. It has been proposed that this is due to telomere shortening. Here, we show that long-term cultured (up to 4 years) v-myc perpetuated hNSC lines do preserve short but stable and homogeneous telomeres (TRF and Q-FISH determinations). hNSC lines (but not strains) express high levels of telomerase activity, which is activated by v-myc, as demonstrated here. Telomerase activity is not constitutive, becoming non-detectable after differentiation (in parallel to v-myc down-regulation). hNSC lines also maintain a stable cell cycle length, mitotic potential, differentiation and neuron generation capacity, and do not express senescence-associated beta-galactosidase over years, as studied here. These data, collectively, help to explain the immortal nature of v-myc-perpetuated hNSC lines, and to establish them as excellent research tools for basic and applied neurobiological and translational studies.  相似文献   
997.
998.
The structural and dynamic properties of the oxoglutarate carrier were investigated by introducing a single tryptophan in the Trp-devoid carrier in position 184, 190 or 199 and by monitoring the fluorescence spectra in the presence and absence of the substrate oxoglutarate. In the absence of substrate, the emission maxima of Arg190Trp, Cys184Trp and Leu199Trp are centered at 342, 345 and 348 nm, respectively, indicating that these residues have an increasing degree of solvent exposure. The emission intensity of the Arg190Trp and Cys184Trp mutants is higher than that of Leu199Trp. Addition of substrate increases the emission intensity of Leu199Trp, but not that of Cys184Trp and Arg190Trp. A 3D model of the oxoglutarate carrier was built using the structure of the ADP/ATP carrier as a template and was validated with the experimental results available in the literature. The model identifies Lys122 as the most likely candidate for the quenching of Trp199. Consistently, the double mutant Lys122Ala-Leu199Trp exhibits a higher emission intensity than Leu199Trp and does not display further fluorescence enhancement in response to substrate addition. Substitution of Lys122 with Cys and evaluation of its reactivity with a sulphydryl reagent in the presence and absence of substrate confirms that residue 122 is masked by the substrate, likely through a substrate-induced conformational change.  相似文献   
999.
    
The restoration of body composition (BC) parameters is considered to be one of the most important goals in the treatment of patients with anorexia nervosa (AN). However, little is known about differences between AN diagnostic subtypes [restricting (AN-R) and binge/purging (AN-BP)] and weekly changes in BC during refeeding treatment. Therefore, the main objectives of our study were twofold: 1) to assess the changes in BC throughout nutritional treatment in an AN sample and 2) to analyze predictors of BC changes during treatment, as well as predictors of treatment outcome. The whole sample comprised 261 participants [118 adult females with AN (70 AN-R vs. 48 AN-BP), and 143 healthy controls]. BC was measured weekly during 15 weeks of day-hospital treatment using bioelectrical impedance analysis (BIA). Assessment measures also included the Eating Disorders Inventory-2, as well as a number of other clinical indices. Overall, the results showed that AN-R and AN-BP patients statistically differed in all BC measures at admission. However, no significant time×group interaction was found for almost all BC parameters. Significant time×group interactions were only found for basal metabolic rate (p = .041) and body mass index (BMI) (p = .035). Multiple regression models showed that the best predictors of pre-post changes in BC parameters (namely fat-free mass, muscular mass, total body water and BMI) were the baseline values of BC parameters. Stepwise predictive logistic regressions showed that only BMI and age were significantly associated with outcome, but not with the percentage of body fat. In conclusion, these data suggest that although AN patients tended to restore all BC parameters during nutritional treatment, only AN-BP patients obtained the same fat mass values as healthy controls. Put succinctly, the best predictors of changes in BC were baseline BC values, which did not, however, seem to influence treatment outcome.  相似文献   
1000.
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