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排序方式: 共有128条查询结果,搜索用时 46 毫秒
31.
Martin Madge Sansalone Vittorio Cooper David M. L. Forwood Mark R. Pivonka Peter 《Biomechanics and modeling in mechanobiology》2019,18(5):1475-1496
Biomechanics and Modeling in Mechanobiology - Significant progress has been made to identify the cells and signaling molecules involved in the mechanobiological regulation of bone remodeling. It is... 相似文献
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Cells lacking functional NF-kappaB die after ligation of some tumor necrosis factor (TNF) receptor family members through failure to express NF-kappaB-dependent anti-apoptotic genes. NF-kappaB activation requires the IkappaB kinase (IKK) complex containing two catalytic subunits named IKKalpha and IKKbeta that regulate distinct NF-kappaB pathways. IKKbeta is critical for classical signaling that induces pro-inflammatory and anti-apoptotic gene profiles, whereas IKKalpha regulates the non-canonical pathway involved in lymphoid organogenesis and B-cell development. To determine whether IKKalpha and IKKbeta differentially function in rescuing cells from death induced by activators of the classical and non-canonical pathways, we analyzed death after ligation of the TNF and lymphotoxin-beta receptors, respectively. Using murine embryonic fibroblasts (MEFs) lacking each of the IKKs, the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, and dominant negative Fas-associated death domain protein, we found that deletion of these kinases sensitized MEFs to distinct cell death pathways. MEFs lacking IKKalpha were sensitized to death in response to both cytokines that was entirely caspase-dependent, demonstrating that IKKalpha functions in this process. Surprisingly, death of IKKbeta-/- MEFs was not blocked by caspase inhibition, demonstrating that IKKbeta negatively regulates caspase-independent cell death (CICD). CICD was strongly activated by both TNF and lymphotoxin-beta receptor ligation in IKKbeta-/- MEFs and was accompanied by loss of mitochondrial membrane potential and the generation of reactive oxygen species. CICD was inhibited by the anti-oxidant butylated hydroxyanosole and overexpression of Bcl-2, neither of which blocked caspase-dependent apoptosis. Our findings, therefore, demonstrate that both IKKalpha and IKKbeta regulate cytokine-induced apoptosis, and IKKbeta additionally represses reactive oxygen species- and mitochondrial-dependent CICD. 相似文献
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R Podstawski DJ Choszcz S Konopka J Klimczak M Starczewski 《Biology of sport / Institute of Sport》2014,31(4):315-321
The aim of the study was to evaluate anthropometric characteristics as determinants of 500 m rowing ergometer performance in physically inactive collegiate females. In this cross-sectional study, which included 196 collegiate females aged 19-23 years not participating in regular physical activities, body mass (BM), body height (BH), length of upper limbs (LA), length of lower limbs (LL), body mass index (BMI), slenderness index (SI), and the Choszcz-Podstawski index (CPI) were measured and a stepwise multiple regression analysis was performed. Participants performed 500 m maximal effort on a Concept II rowing ergometer. BM, BH, LA, LL, and the BMI, SI and CPI indices were found to be statistically significant determinants of 500 m performance. The best results (T) were achieved by females whose BH ranged from 170 to 180 cm, with LA and LL ranging from 75 to 80 cm and 85 to 90 cm, respectively. The best fitting statistical model was identified as: T = 11.6793 LR – 0.1130 LR2 – 0.0589 LN2 + 29.2157 CPI2 + 0.1370 LR·LN - 2.6926 LR·CPI – 211.7796. This study supports a need for additional studies focusing on understanding the importance of anthropometric differences in rowing ergometer performance, which could lead to establishing a better quality reference for evaluation of cardiorespiratory fitness tested using a rowing ergometer in collegiate females. 相似文献
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Evolution at the tip and base of the X chromosome in an African population of Drosophila melanogaster 总被引:1,自引:0,他引:1
Hitchhiking effects of advantageous mutations have been invoked to explain
reduced polymorphism in regions of low crossing-over in Drosophila. Besides
reducing DNA heterozygosity, hitchhiking effects should produce strong
linkage disequilibrium and a frequency spectrum skewed toward an excess of
rare polymorphisms (compared to the neutral expectation). We measured DNA
polymorphism in a Zimbabwe population of D. melanogaster at three loci,
yellow, achaete, and suppressor of forked, located in regions of reduced
crossing-over. Similar to previously published surveys of these genomic
regions in other populations, we observed low levels of nucleotide
variability. However, the frequency spectrum was compatible with a neutral
model, and there was abundant evidence for recombination in the history of
the yellow and ac genes. Thus, some aspects of the data cannot be accounted
for by a simple hitchhiking model. An alternative hypothesis, background
selection, might be compatible with the observed patterns of linkage
disequilibrium and the frequency spectrum. However, this model cannot
account for the observed reduction in nucleotide heterozygosity. Thus,
there is currently no satisfactory theoretical model for the data from the
tip and base of the X chromosome in D. melanogaster.
相似文献
40.
Oligogalacturonic acids (OGAs), derived from plant cell wall pectin, have
been implicated in a number of signal transduction pathways involved in
growth, development and defense responses of higher plants. This study
investigates the size range of OGAs capable of inducing ethylene synthesis
in tomato plants, and demonstrates that in contrast with many other
effects, only short chain OGAs are active. Oligomers across a range of DP
from 2-15 were separated and purified to homogeneity by QAE-Sephadex anion
exchange chromatography using a novel elution system. The OGAs were applied
to tomato plants and assayed for their ability to induce ethylene gas
release and changes in steady state levels of mRNA encoding the ethylene
forming enzyme aminocyclopropane-1-carboxylic acid oxidase (ACO). The study
demonstrated that only OGAs in the size range of DP4-6 were active both in
eliciting ACO expression and in the production of ethylene.
相似文献