The endothelium is the largest organ in the body, consisting of endothelial cells (ECs) lining every blood vessel. Historically ECs were considered to be merely an inert structural component of vasculature to form a semipermeable barrier between the blood and the interstitium of each organ. Currently it is widely appreciated that ECs function in a multitude of physiologic processes, including the control of cellular trafficking, the regulation of vasomotor tone, the maintenance of blood fluidity, and the growth of new blood vessels [1, 2]. Endothelial cell heterogeneity has been recognized at the level of morphology, function, antigen composition, and signaling network . Genetic determinants and environmental cues may critically regulate endothelial cell heterogeneity and contribute to its normal function and its response to pathophysiological stimuli. With the full human genome sequence in hand  and the advent of new powerful DNA microarray technology [5, 6] and serial analysis of gene expression (SAGE ), the research paradigm has been shifted from the traditional search for a single or a few specific genes to the current understanding of the biochemical and molecular functioning of hundreds and thousands of genes and how complicated networks of interaction determine the normal function of ECs and lead to the dysfunction of ECs and pathogenesis of various human diseases. In this chapter, the first part synop-sizes DNA microarray and SAGE technologies and the second part highlights new biological insights derived from the application of DNA microarray and SAGE in the gene expression profiling of EC. The epilogue contains perspectives.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.