Open AccessUltrastructural Characterization of Endogenous Retroviral Particles Isolated from Normal Human Placentas1
Author(s) -
Timothy Lyden,
Peter Johnson,
Jason M. Mwenda,
Neal S. Rote
Publication year - 1994
Publication title -
biology of reproduction
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.366
H-Index - 180
eISSN - 1529-7268
pISSN - 0006-3363
DOI - 10.1095/biolreprod51.1.152
Subject(s) - ultrastructure , biology , phosphotungstic acid , uranyl acetate , endogenous retrovirus , reverse transcriptase , microbiology and biotechnology , capsid , endogeny , electron microscope , biophysics , particle (ecology) , virology , biochemistry , virus , rna , anatomy , gene , genome , ecology , physics , optics , catalysis
Human placental endogenous retroviral (ERV) particle isolates were investigated by ultrastructural evaluation. Although retrovirus-like structures in normal human placental tissue sections have been described, the precise nature of these particles has not previously been defined. By direct electron microscopic (EM) observation of placental ERV isolates that display retroviral reverse transcriptase (RTase) activity and a buoyant density consistent with type-C retroviruses (1.17 g/ml on sucrose), we have shown these to contain particles with characteristic retroviral ultrastructural features. Samples were stained with 1.0% phosphotungstic acid (PTA), 0.5% uranyl acetate (UA), and low-angle-shadowed with platinum/palladium. Isolated placental ERV particles have an apparent diameter of approximately 120 nm, are membrane-bound with a short surface fringe, and contain capsid particles (about 90 nm in diameter) within an internal matrix structure. These observations support the view that human placental cells normally express ERV particles.