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Giardia muris: ultrastructural analysis of in vitro excystation
Abstract:
Giardia muris cysts were examined by transmission electron microscopy before treatment, after induction, and at timed intervals during the incubation phase of in vitro excystation. Untreated G. muris cysts had a thick cyst wall composed of a fibrous outer wall and a thin, electron-dense inner membrane which extended from the trophozoite plasma membrane. The cytoplasm was devoid of endoplasmic reticulum, Golgi bodies,and mitochondria. Numerous large vacuoles were present within the ectoplasm just beneath the plasma membrane in untreated cysts. Following induction these cysts lacked ectoplasmic vacuoles. Concurrently, numerous membrane bound vesicles were seen in the peritrophic space closely adhering to the surface of the trophozoite. These vesicles appear to be of cytoplasmic origin. The cytoplasm of fully excysted trophozoites lacked ectoplasmic vacuoles but displayed well-developed ribbons of microtubular bodies, probably precursors of ventral disk, lateral flange, and median bodies and also contained extensive granular endoplasmic reticulum. No more than two nuclei were observed within each organism. The earliest excysted organisms were observed 0-5 min after incubation had begun and most organisms had excysted within 10 min. Cytokinesis occurred only after excystation was complete.
Insights
This study reveals the structural changes in Giardia muris during excystation. Key findings show the transformation from a vacuole-rich cyst to a trophozoite with developed organelles and microtubular structures.
Area of Science:
- Parasitology
- Cell Biology
- Microscopy
Background:
- Giardia muris is a protozoan parasite.
- Cyst excystation is a critical step in Giardia infection.
Purpose of the Study:
- To investigate the ultrastructural changes of Giardia muris during in vitro excystation.
- To characterize the morphological transformations from cyst to trophozoite.
Main Methods:
- Transmission electron microscopy (TEM) was used.
- Cysts were examined before treatment, after induction, and during incubation for excystation.
Main Results:
- Untreated cysts had a thick wall and lacked organelles but contained ectoplasmic vacuoles.
- Induced cysts lost vacuoles and showed cytoplasmic vesicles.
- Excysted trophozoites developed endoplasmic reticulum and microtubular structures, with cytokinesis occurring post-excystation.
Conclusions:
- Giardia muris undergoes significant ultrastructural reorganization during excystation.
- The development of specific organelles and structures is crucial for the trophozoite stage.