低剂量Activin A通过激活CD8+T细胞发挥抗肿瘤效应

Activin A属于转化生长因子-β(transforming growth factor-β,TGF-β)超家族中的多功能细胞因子,存在于多种免疫细胞中.CD8⁺T细胞是发挥抗肿瘤活性的主要免疫细胞类型.以H22细胞移植瘤模型旨在探讨Activin A对CD8⁺T细胞功能的调控和作用机制.本研究首先在分离出的CD8⁺T细胞上发现Activin A受体及下游信号分子的表达.体外实验表明Activin A对小鼠H22肝癌细胞系的凋亡及增殖无显著影响.H22荷瘤鼠的体内研究发现低浓度Activin A抑制肿瘤生长,高浓度Activin A促进肿瘤生长.在Activin A对肿瘤CD8⁺T细胞作用的研究中,发现大剂量Activin A处理的肿瘤中CD8⁺T细胞含量减少,小剂量Activin A处理组中CD8⁺T细胞含量则增加.以上数据表明,不同剂量的Activin A可能通过调控CD8⁺T细胞的浸润对肿瘤的生长发挥双重作用.     

机械电子类科技查新工作的探讨与实践

结合从事机械电子类科技查新的工作经验,探讨了机械电子类科技查新工作的特点,提出了提高机电类科技查新工作水平的途径,对具体的科技查新实例进行了分析。     

Stress and morphology of a nonpolar a-plane GaN layer on r-plane sapphire substrate

The anisotropic strain of a nonpolar (1120) a-plane GaN epilayer on an r-plane (1102) sapphire substrate, grown by low-pressure metal-organic vapour deposition is investigated by Raman spectroscopy. The room-temperature Raman scattering spectra of nonpolar a-plane GaN are measured in surface and edge backscattering geometries. The lattice is contracted in both the c- and the m-axis directions, and the stress in the m-axis direction is larger than that in the c-axis direction. On the surface of this sample, a number of cracks appear only along the m-axis, which is confirmed by the scanning electron micrograph. Atomic force microscopy images reveal a significant decrease in the root-mean-square roughness and the density of submicron pits after the stress relief.