The Regulatory Role of MeAIB in Protein Metabolism and the mTOR Signaling Pathway in Porcine Enterocytes.

Amino acid transporters play an important role in cell growth and metabolism. MeAIB, a transporter-selective substrate, often represses the adaptive regulation of sodium-coupled neutral amino acid transporter 2 (SNAT2), which may act as a receptor and regulate cellular amino acid contents, therefore modulating cellular downstream signaling. The aim of this study was to investigate the effects of MeAIB to SNAT2 on cell proliferation, protein turnover, and the mammalian target of rapamycin (mTOR) signaling pathway in porcine enterocytes. Intestinal porcine epithelial cells (IPEC)-J2 cells were cultured in a high-glucose Dulbecco's modified Eagle's (DMEM-H) medium with 0 or 5 mmoL/L System A amino acid analogue (MeAIB) for 48 h. Cells were collected for analysis of proliferation, cell cycle, protein synthesis and degradation, intracellular free amino acids, and the expression of key genes involved in the mTOR signaling pathway. The results showed that SNAT2 inhibition by MeAIB depleted intracellular concentrations of not only SNAT2 amino acid substrates but also of indispensable amino acids (methionine and leucine), and suppressed cell proliferation and impaired protein synthesis. MeAIB inhibited mTOR phosphorylation, which might be involved in three translation regulators, EIF4EBP1, IGFBP3, and DDIT4 from PCR array analysis of the 84 genes related to the mTOR signaling pathway. These results suggest that SNAT2 inhibition treated with MeAIB plays an important role in regulating protein synthesis and mTOR signaling, and provide some information to further clarify its roles in the absorption of amino acids and signal transduction in the porcine small intestine

Secrecy Outage and Diversity Analysis of Cognitive Radio Systems

In this paper, we investigate the physical-layer security of a multi-user multi-eavesdropper cognitive radio system, which is composed of multiple cognitive users (CUs) transmitting to a common cognitive base station (CBS), while multiple eavesdroppers may collaborate with each other or perform independently in intercepting the CUs-CBS transmissions, which are called the coordinated and uncoordinated eavesdroppers, respectively. Considering multiple CUs available, we propose the round-robin scheduling as well as the optimal and suboptimal user scheduling schemes for improving the security of CUs-CBS transmissions against eavesdropping attacks. Specifically, the optimal user scheduling is designed by assuming that the channel state information (CSI) of all links from CUs to CBS, to primary user (PU) and to eavesdroppers are available. By contrast, the suboptimal user scheduling only requires the CSI of CUs-CBS links without the PU's and eavesdroppers' CSI. We derive closed-form expressions of the secrecy outage probability of these three scheduling schemes in the presence of the coordinated and uncoordinated eavesdroppers. We also carry out the secrecy diversity analysis and show that the round-robin scheduling achieves the diversity order of only one, whereas the optimal and suboptimal scheduling schemes obtain the full secrecy diversity, no matter whether the eavesdroppers collaborate or not. In addition, numerical secrecy outage results demonstrate that for both the coordinated and uncoordinated eavesdroppers, the optimal user scheduling achieves the best security performance and the round-robin scheduling performs the worst. Finally, upon increasing the number of CUs, the secrecy outage probabilities of the optimal and suboptimal user scheduling schemes both improve significantly.Comment: 16 pages, 5 figures, accepted to appear, IEEE Journal on Selected Areas in Communications, 201

Constant self-initiated teacher change, factors, and mechanism: a narrative inquiry

Teachers are difficult to change, and this has long been a challenge for many teacher educators because a fundamental maxim of teacher education programs is to promote reflection and change in teachers. Despite the many studies on teacher change, our understanding of teacher change requires further understanding. Based on a narrative inquiry of teacher “Blue”, the present study found that teacher resilience and reflection, as well as continuing professional development learning are the three most important factors that led to her self-initiated change. In addition, Blue’s change as a teacher developed along with her deepened and broadened reflection of her teaching content, and methods, as well as her beliefs about her students and other socio-cultural issues. Rather than refurbishing her entire belief and practice, Blue’s change was a gradual extension of her schema; she built her new ideas upon the old, through constant reflection, teacher learning, and with her resilience

Validity of non-invasive methods for body composition measurements in older adults

ABSTRACT Purpose: The aim of this study was to investigate the validity of bioelectrical impedance analysis (BIA) and air-displacement plethysmography (ADP) in relation to dual energy X-ray absorptiometry (DXA) (i.e. the reference standard). Methods: Sixty-three older adults aged 60-96 years (40 men, 23 women). Body percent fat (%BF) was estimated by BIA, ADP and DXA. Single frequency (50Hz) BIA that measures whole body impedance was used and Kyle\u27s equation was applied to estimate fat-free mass. Paired sample t-test, absolute percent errors and Cohen\u27s d were used to evaluate differences among the 3 different methods. Methods agreement was assessed by Pearson\u27s correlation, regression analysis and Bland-Altman plots. Classification agreement of obesity was evaluated using Kappa statistics. Results: ADP and BIA significantly overestimated %BF relative to DXA by 3.3% and 3.1%, yielding absolute errors of 14.1% and 12.4%, respectively. However, ADP (Cohen\u27s d=0.35) had better agreement with DXA and BIA (Cohen\u27s d=0.40). Regression analysis indicated smaller individual variations of ADP (SEE=3.23) compared to BIA (SEE=4.78). In addition, ADP (Kappa=0.58) showed better obesity classification agreement relative to DXA in comparison with BIA (Kappa = 0.35). However, Bland-Altman plots showed a positive proportional pattern (Slope= 0.24, R2=0.24, p\u3c0.05) of biases in ADP, while no systematic pattern of biases was observed for BIA. A gender difference was also detected, indicating a better agreement in males than females. Conclusion: Given that both BIA and ADP had acceptable agreement with DXA in estimating %BF of older adults, ADP showed relatively better agreement in body composition measurement (i.e. %BF) and obesity classification in comparison to BIA. However, practitioners and/or researchers should be aware of the potential biases when using ADP to estimate %BF in older populations