Cell Tropism and Pathogenesis of Measles Virus in Monkeys

Measles virus (MV) is an enveloped negative strand RNA virus belonging to the family of Paramyxoviridae, genus Morbillivirus, and causes one of the most contagious diseases in humans. Experimentally infected non-human primates are used as animal models for studies of the pathogenesis of human measles. We established a reverse genetics system based on a highly pathogenic wild-type MV. Infection of monkeys with recombinant MV strains generated by reverse genetics enabled analysis of the molecular basis of MV pathogenesis. The essential in vivo function of accessory genes was indicated by infecting monkeys with recombinant MV strains deficient in the expression of accessory genes. Furthermore, recombinant wild-type MV strains expressing enhanced green fluorescent protein enabled visual tracking of MV-infected cells in vitro and in vivo. To date, three different molecules have been identified as receptors for MV. Signaling lymphocyte activation molecule (SLAM, also called CD150), expressed on immune cells, is a major receptor for MV. CD46, ubiquitously expressed in all nucleated cells in humans and monkeys, is a receptor for vaccine and laboratory-adapted strains of MV. The newly identified nectin-4 (also called poliovirus-receptor-like-4) is an epithelial cell receptor for MV. However, recent findings have indicated that CD46 acts as an MV receptor in vitro but not in vivo. The impact of the receptor usage of MV in vivo on the disease outcome is now under investigation

Microstructure and mechanical behavior of TiC-reinforced Ti-Mo-Al alloys

Ti-based alloys have gained extensive attractions in high-temperature engineering applications over the past several decades because of their low density, impressive strength and wear resistance. The continuing demands for advanced structural materials in aerospace and automobile sectors encourage further exploits of Ti-based alloys. Solid-solution hardening has been confirmed as an effective way to improve the mechanical performance of Ti-based alloys. Recent studies suggest that the incorporation of fibrous or particulate reinforcements, such as SiC, TiB and TiC, is necessary to maintain their high specific strength at elevated temperatures. In this study, Ti-Mo-Al (Ti50Mo35Al15, at.%) alloys with various TiC additions (1, 5, 10 at.%) were prepared by arc melting technique. We examined the microstructure of these as-cast alloys by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). Their mechanical properties were systematically evaluated via compression experiments at various temperatures (T=298, 1073 and 1273 K), Vickers hardness as well as four-point bending tests. According to the experimental observations, all the alloys prepared in this work were composed of two phases, Ti-Mo-Al solid solution ( phase) matrix and TiC particles. Most of the TiC particles precipitated along grain boundaries, following the N-W crystallographic relationship with the matrix. Moreover, the effect of TiC addition on the microstructure of Ti-Mo-Al alloys was mainly manifested in the reduction of average grain size, which is ~80 m in the alloy without TiC but ~30 m in the 10 at.% TiC-added one. The addition of TiC leads to an obvious enhancement of strength at both room and high temperatures, without impairing the ductility. It is worth noting that the maximum flow stress achieved in the TiC-reinforced Ti-Mo-Al alloys at 1273 K is ~400 MPa. Therefore, the reinforcement by TiC is an effective way in improving the mechanical performance of Ti-Mo-Al alloys