分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Whether extrapulmonary lesions are avid for 18F-fluorodeoxyglucose (18F-FDG) could help to differentiate the benign or malignant lung lesions. In this trial, the 199 consecutive patients with newly diagnosed lung lesions (169 malignant and 36 benign lesions) were imaged by whole body 18F-FDG PET/CT. Histopathology and clinic results served as the reference standard. The malignancy likelihood were conducted by CTscores; the maximum standardized uptake value (SUVmax) of lung lesions, and PET on FDG negative or positive, as well as metastasis index (MI), by PET combined with CT findings. The data were analyzed by stepwise logistic regression and receiver-operating- characteristic. The malignancy predictive probability (P) was obtained by P =ex/(1+ex), where x= 1.16+0.87 (CTscore) +0.15(SUVmax)+0.27(MI). The area under curve (AUC) for the fitted logistic model was 0.820.04, this was superior and significantly different from SUVmax(AUC, 0.730.05) and CTscores(AUC, 0.710.05). The fitted logistic model could improve the diagnostic performance. The MI could help for differential diagnosis.
分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-11
摘要: In eukaryotic cells, genomic DNA is hierarchically packed into chromatin by histones in the nucleus. Despite of over 30 years' study, the fundamental structure of 30 nm chromatin fiber remains controversial. In this review, we focus on recent progress in revealing the structure of 30 nm chromatin fiber, and emphasize on the most recent left-handed double helix structure of 30 nm chromatin fiber. In addition, we discuss the epigenetic regulation of the 30 nm chromatin structure. Finally, we discuss the possible challenge in elucidating the structure of 30 nm chromatin fiber and its regulation.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-11
摘要: Although there have been many investigations into how trinucleotide repeats affect nucleosome formation and local chromatin structure, the nucleosome positioning of GAA triplet-repeats in the human genome has remained elusive. In this work, the nucleosome occupancy around GAA triplet-repeats across the human genome was computed statistically. The results showed a nucleosome-depleted region in the vicinity of GM triplet-repeats in activated and resting CD4(+) T cells. Furthermore, the A-tract was frequently adjacent to the upstream region of GM triplet-repeats and could enhance the depletion surrounding GAA triplet-repeats. In vitro chromatin reconstitution assays with GM-containing plasmids also demonstrated that the inserted GAA triplet-repeats destabilized the ability of recombinant plasmids to assemble nucleosomes. Our results suggested that GM triplet-repeats have lower affinity to histones and can change local nucleosome positioning. These findings may be helpful for understanding the mechanism of Friedreich's ataxia, which is associated with GM triplet-repeats at the chromatin level. (C) 2015 Elsevier Inc All rights reserved.
分类: 生物学 >> 生物物理学 >> 细胞生物学 提交时间: 2016-05-12
摘要: Specific recognition of centromere-specific histone variant CENP-A-containing chromatin by CENP-N is an essential process in the assembly of the kinetochore complex at centromeres prior to mammalian cell division. However, the mechanisms of CENP-N recruitment to centromeres/kinetochores remain unknown. Here, we show that a CENP-A-specific RG loop (Arg80/Gly81) plays an essential and dual regulatory role in this process. The RG loop assists the formation of a compact "ladder-like" structure of CENP-A chromatin, concealing the loop and thus impairing its role in recruiting CENP-N. Upon G1/S-phase transition, however, centromeric chromatin switches from the compact to an open state, enabling the now exposed RG loop to recruit CENP-N prior to cell division. Our results provide the first insights into the mechanisms by which the recruitment of CENP-N is regulated by the structural transitions between compaction and relaxation of centromeric chromatin during the cell cycle.
分类: 生物学 >> 生物物理学 >> 细胞生物学 提交时间: 2016-05-12
摘要: The H3 histone variant CENP-A is an epigenetic marker critical for the centromere identity and function. However, the precise regulation of the spatiotemporal deposition and propagation of CENP-A at centromeres during the cell cycle is still poorly understood. Here, we show that CENP-A is phosphorylated at Ser68 during early mitosis by Cdk1. Our results demonstrate that phosphorylation of Ser68 eliminates the binding of CENP-A to the assembly factor HJURP, thus preventing the premature loading of CENP-A to the centromere prior to mitotic exit. Because Cdk1 activity is at its minimum at the mitotic exit, the ratio of Cdk1/PP1 alpha activity changes in favor of Ser68 dephosphorylation, thus making CENP-A available for centromeric deposition by HJURP. Thus, we reveal that dynamic phosphorylation of CENP-A Ser68 orchestrates the spatiotemporal assembly of newly synthesized CENP-A at active centromeres during the cell cycle.