Ubiquitin and ubiquitin-conjugated protein expression in the rat cerebral cortex and hippocampus following traumatic brain injury (TBI)
BRAIN RESEARCH
Authors: Yao, Xianglan; Liu, Jiong; McCabe, Joseph T.
Abstract
Regulation of protein turnover is essential to the survival of eukaryotic cells. This important cellular process is partly regulated by the ubiquitin-proteasome system through posttranslational modification by the conjugation of ubiquitin chains to proteins targeted for degradation by proteasomes. The present study examined ubiquitin mRNA and protein expression in the CNS of rats that sustained traumatic brain injury (TBI). Quantitative real-time polymerase chain reaction results indicated that mRNA levels of ubA52, ubB and ubC in the ipsilateral cerebral cortex were significantly decreased on Day I post-TBI, that UbC mRNA levels also were significantly lower than control on Day 3 post-TBI,but that by Day 7 post-TBI, ubA52, ubB and ubC mRNA levels had all returned to control levels. In the ipsilateral hippocampus, ubA52 mRNA levels were significantly lower on Days 1-7 post-TBI, while ubB and ubC mRNA levels were less only on Day I post-TBI. Western blotting found that free ubiquitin protein levels were significantly reduced in both ipsilateral cerebral cortex and hippocampus on Days 1-7 post-TBI, while there was markedly increased ubiquitin-conjugated protein in ipsilateral cerebral cortex on Day 7 and in hippocampus on Days 3-7 post-TBI. Our study suggests that altered ubiquitin system function in the CNS contributes to the pathological outcomes of TBI. (C) 2007 Elsevier B.V. All rights reserved.
A novel method of non-probabilistic reliability-based topology optimization corresponding to continuum structures with unknown but bounded uncertainties
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
Authors: Wang, Lei; Liu, Dongliang; Yang, Yaowen; Wang, Xiaojun; Qiu, Zhiping
Abstract
A new non-probabilistic reliability-based topology optimization (NRBTO) method for detailed design of continuum structures is proposed in this paper, in which the unknown but bounded (UBB) uncertainties existing in material and external loads are considered simultaneously. Based on the interval set-theoretic model, traditional displacement constraint is transformed into the non-probabilistic reliability format, in which a novel measuring index, namely, the optimization feature distance is defined by a combination of the area-ratio ideas. Thus, the optimal layout issue is converted by the lightweight design problem with displacement reliability constraints. Moreover, the interval parametric vertex approach and the adjoint vector method are also employed to obtain the sensitivity information between the reliability measurement and design variables. By utilizing the method of moving asymptotes (MMA), the optimization problem that is investigated can be solved iteratively. Two engineering examples are eventually presented to demonstrate the validity and effectiveness of the methodology that has been developed, and numerical results show that considering the UBB uncertainty effects during the whole procedure of topology optimization may have a significant influence on the final structural configurations. (C) 2017 Elsevier B.V. All rights reserved.