Čo sa stane s epimeritom eugregarín (Apicomplexa) po uvoľnení trofozoita?
| Title in English | What happens to eugregarine epimerite after detachment of the trophozoite from the host epithelium? |
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| Authors | |
| Year of publication | 2007 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | Eugregarines represent a diverse group of apicomplexans parasitizing invertebrates. Their sporozoites generally develop into epicellular trophozoites attached to the host epithelium by a specialized attachment organelle called the epimerite and their attachment strategy is similar to those in cryptosporidia. The architecture of the epimerite with associated structures and the mechanism of trophozoite detachment from the host epithelium were studied in Gregarina polymorpha in the intestine of Tenebrio molitor larvae, using electron and immunofluorescence microscopy. Here we propose a new hypothesis on the mechanism of trophozoite detachment from the host epithelium based on epimerite retraction back into the protomerite, instead of the commonly accepted theory describing gradual epimerite constriction and subsequent separation facilitated by the contractility of osmiophilic ring (membrane fusion site). This conclusion is based on observations on several eugregarine species in which: (i) epimerite appears as a dynamic structure whose shape dramatically changes depending on whether it is embedded into the epithelium or not; (ii) we never observed any remains of recently discarded epimerite in host epithelium; (iii) the epimerite exhibits significant decrease and shrinking at the end of trophozoite development; (iv) there is obvious accumulation of filamentous actin at the epimerite base and in the protomerite apical end, and a patch accumulation in the protomerite of maturing and mature trophozoites, suggesting the presence of contractile elements; (v) the cortical zone and area of the membrane fusion site are structures rich in myosin; (vi) there is no real fusion between the host and epimerite plasma membranes along their interface; (vii) a new plasma membrane would have to form at the protomerite apical end to cover damaged area after eventual epimerite separation; (viii) the protomerite top, formerly bearing the epimerite, is covered by an intact, smooth plasma membrane lacking signs of any damage. |
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