Original Articles: PDF OnlyIn Vitro Penetration of Human Corneal Epithelium by Acanthamoeba castellanii: A Scanning and Transmission Electron Microscopy StudyMoore, Mary Beth M.D.1; Ubelaker, John E. Ph.D.2; Martin, James H. Ph.D.3; Silvany, Robert B.S.1; Dougherty, Joel M. Ph.D.1; Meyer, Dale R. Ph.D.1; McCulley, James P. M.D.1 Author Information 1From the Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, U.S.A. 2From the Department of Biological Sciences, Southern Methodist University Dallas, Texas, U.S.A. 3From the Department of Pathology, Baylor University Medical Center, Dallas, Texas, U.S.A. Cornea: July 1991 - Volume 10 - Issue 4 - p 291-298 Buy Abstract Human corneal buttons were exposed to Acanthamoeba castellanii trophozoites and cysts for 12 hours at 35°C. The buttons examined by light microscopy and scanning and transmission electron microscopy had severe epithelial ulceration and penetration by trophozoites. Observations on trophozoites below the surface suggest that penetration is accomplished by both secreted cytolytic enzymes and phagocytosis. It is likely that the secretion of one or more enzymes constitutes the initial step in preparing the host tissue for endocytosis or that the secretory mechanism is used by the amebas to move through the outer squamous layer to the basement epithelium where phagocytosis occurs. Based on this study and a previous study, it appears that entry into the cornea is a two-step process involving adherence and penetration by trophozoites. © Lippincott-Raven Publishers.