Expression of Biologically Active Human Vascular Endothelial Growth Factor in Yeast

Abstract Vascular endothelial growth factor (VEGF) is a glycoprotein consisting of two identical polypeptide chains linked by a disulfide bond. The unique biological activities of VEGF include its potent mitogenic and permeability inducing properties specific for the vascular endothelium. VEGF is implicated in tumor angiogenesis, wound healing, and the stimulation of collateral vessel formation at the site of arterial occlusion. Therefore, in order to produce large quantities of biologically active VEGF, a splice variant (VEGF165) was cloned and expressed in a yeast expression system. The coding region of VEGF165 was isolated from U937 cells by RT-PCR, sequenced and then cloned into the yeast expression vector pHILS1. VEGF165 was secreted into the medium as a dimer. Recombinant VEGF reacted to antibodies raised against the N-terminal and C-terminal synthetic polypeptides of human VEGF. As much as 35-40 mg/L of purified VEGF could be obtained from the yeast expression system. The recombinant protein was biologically active in inducing vascular endothelial cell proliferation in vitro and permeability changes in vivo

The C.B.S. Problem in American Radio Historiography

The Columbia Broadcasting System (C.B.S.) emerged in the late 1920s as the only sustainable competitor to the National Broadcasting Company (NBC) in American network radio. But scholars know far less about C.B.S. than NBC because the C.B.S. corporation failed to retain, and make accessible to media historians, internal archival and documentary materials from its developmental era. This article examines the historical void created by America’s second network while offering two specific historical case studies to establish how the loss of C.B.S. materials continues to hinder knowledge about America’s second network, the American system of broadcasting, and the political economy of the commercial mass media in the United States.</p