title: Ultrastructural changes during in vitro encystment of Blastocystis hominis.
abstract: The morphological changes occurring in Blastocystis hominis at different time points following in vitro encystment were studied by electron microscopy. The following stages of the parasite were sequentially seen: (a) the amoebic form, which was irregular in shape, with a majority of the organelles being concentrated at the condensed cytoplasmic region; (b) the pre-cystic form, which was rounded and had an electron-dense material forming a homogeneous wall around the central body; and (c) the cystic form, which had a very prominent, thick osmiophilic electron-dense wall, within which there were many inclusions and possibly reproductive granules. The amoebic form appeared to be an intermediate stage between the vacuolar form and the pre-cystic form, as this stage allowed the parasite to ingest bacteria to enhance encystment. The pre-cystic stage had previously been shown in experimental infection to be infective. The role of the cystic stage in producing infection is currently being investigated.
authors.affiliation: Department of Microbiology, Faculty of Medicine, National University of Singapore, Kent Ridge.
authors.forename: K
authors.initials: K
authors.lastname: Suresh
authors.forename: J
authors.initials: J
authors.lastname: Howe
authors.forename: S Y
authors.initials: SY
authors.lastname: Chong
authors.forename: G C
authors.initials: GC
authors.lastname: Ng
authors.forename: L C
authors.initials: LC
authors.lastname: Ho
authors.forename: A K
authors.initials: AK
authors.lastname: Loh
authors.forename: N P
authors.initials: NP
authors.lastname: Ramachandran
authors.forename: E H
authors.initials: EH
authors.lastname: Yap
authors.forename: M
authors.initials: M
authors.lastname: Singh
mesh_terms: D000818:Animals; D016845:Blastocystis hominis / Q000502:physiology* / Q000648:ultrastructure; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D008854:Microscopy, Electron