[Observation on the ultrastructure of Pneumocystis carinii].
OBJECTIVE
To study the life cycle and morphology of Pneumocystis carinii by ultrastructural observation.


METHODS
Wistar rat model of P. carinii infection was established by subcutaneous injection with dexamethasone. Lung tissue of the infected rats was used for the transmission electron microscopical study.


RESULTS
The organisms were mainly present in the lung alveolar cavity, and also in the alveolar septum, pulmonary macrophages and neutrophils. More trophozoites of P. carinii attached to the type I alveolar epithelial cells, and rarely to the type II alveolar epithelial cells. Most of these trophozoites showed pseudopodial evaginations on their pellicles. The nucleus-associated organelle and spindle microtubules were observed in some trophozoites. The precyst phase was in three forms: early, intermediate and late form. Synaptonemal complexes indicating meiotic nuclear divisions and a clump of mitochondria were also observed in the precyst. The pellicle of the cyst has a thickened portion with a pore. There were nucleus with nucleolus, mitochondrion, vesicles, endoplasmic reticulum and numerous ribosomes in the organisms, and tubular expansions on its surface.


CONCLUSIONS
The life cycle of P. carinii consists of trophozoite, precyst and cyst stages. The presence of a single pore in the cyst wall reveals that pore formation may be a mode of excystation for intracystic bodies of P. carinii.
Gong
Yu-Xiang
YX
Department of Parasitology, Qingdao University Medical College, Qingdao 266021, China.
Chang
Zhi-Shang
ZS
Zhang
Zhong-Guang
ZG
Zeng
Xian-Zhong
XZ
Tan
Jin-Shan
JS
Zhao
Rong
R
Wang
Yuan-Song
YS
D000818:Animals; D005260:Female; D046529:Microscopy, Electron, Transmission; D045363:Pneumocystis carinii / Q000302:isolation & purification / Q000648:ultrastructure*; D011020:Pneumonia, Pneumocystis / Q000469:parasitology*; D011650:Pulmonary Alveoli / Q000469:parasitology*; D051381:Rats; D017208:Rats, Wistar