The Role and Regulation of Etv2 in Zebrafish Vascular Development: A Dissertation

Etv2 is an endothelial-specific ETS transcription factor that is essential for endothelial differentiation and vascular morphogenesis in vertebrates. However, etv2 expression dynamics during development and the mechanisms regulating it are poorly understood. I found that etv2 transcript and protein expression are highly transient during zebrafish vascular development, with both expressed early during development and then subsequently downregulated. Inducible knockdown of Etv2 in zebrafish embryos prior to mid-somitogenesis, but not later, causes severe vascular defects, suggesting a role for Etv2 in specifying angioblasts from the lateral mesoderm. I further demonstrate that the 3’UTR of etv2 is post-transcriptionally regulated in part by the let-7 family of microRNAs. Ectopic expression of let-7a represses endogenous Etv2 transcript and protein expression with a concomitant reduction in endothelial cell gene expression. Additionally, overexpressed Etv2 in HEK293T cells is ubiquitinated and degraded by the proteasome. Accordingly, endogenous zebrafish Etv2 protein is rapidly degraded in the presence of the translation inhibitor cycloheximide in vivo. Taken together, our results suggest that etv2 acts during early development to specify endothelial lineages and is subsequently downregulated through post-transcriptional and post-translational mechanisms, to allow normal vascular development to proceed

Space station structures and dynamics test program

The design, construction, and operation of a low-Earth orbit space station poses challenges for development and implementation of technology. One specific challenge is the development of a dynamics test program for defining the space station design requirements, and identifying and characterizing phenomena affecting the space station's design and development. The test proposal, as outlined, is a comprehensive structural dynamics program to be launched in support of the space station (SS). Development of a parametric data base and verification of the mathematical models and analytical analysis tools necessary for engineering support of the station's design, construction, and operation provide the impetus for the dynamics test program. The four test phases planned are discussed: testing of SS applicable structural concepts; testing of SS prototypes; testing of actual SS structural hardware; and on-orbit testing of SS construction

Emerging Issues in Infective Endocarditis

Infective endocarditis, a serious infection of the endocardium of the heart, particularly the heart valves, is associated with a high degree of illness and death. It generally occurs in patients with altered and abnormal heart architecture, in combination with exposure to bacteria through trauma and other potentially high-risk activities involving transient bacteremia. Knowledge about the origins of endocarditis stems from the work of Fernel in the early 1500s, and yet this infection still presents physicians with major diagnostic and management dilemmas. Endocarditis is caused by a variety of bacteria and fungi, as well as emerging infectious agents, including Tropheryma whiplei, Bartonella spp., and Rickettsia spp. We review the evolution of endocarditis and compare its progression with discoveries in microbiology, science, and medicine