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Morphology, development and behavior of Pneumocystis carinii observed by light-microscopy in nude mice
Abstract:
The present paper describes the morphology, development and behavior of Pneumocystis carinii, especially of the trophozoites in the alveoli of conventionally raised BALB/c nude mice, by using phase-contrast microscopy, paraffin sections and semiultrathin sections embedded in JB-4 plastic. Under phase-contrast microscopy, trophozoites were ameboid in external appearance and 2 to 8 micron in diameter. Usually they have one or more lucid spherical vacuoles and one less lucid nucleus in the cytoplasm. Maturation and independence of intracystic bodies were observed in the developing cysts. The intracystic bodies were polymorphic, i.e. spherical, ameboid or elongated. The paraffin sections using the double staining of P. carinii with Gomori's methenamine silver nitrate (GMS) and Giemsa, showed a small number of mature cysts containing intracystic bodies and a large number of trophozoites within the characteristic honeycombed material in the alveolar spaces. In order to investigate the morphology and parasitizing behavior of the trophozoites and cysts as well as the response of alveolar tissue in more detail, semiultrathin sections of 0.5-2 micron thickness were made from the materials embedded in JB-4 plastic and stained with Giemsa. In lightly infected alveoli, some trophozoites and cysts were found to be closely attached to the Type I alveolar epithelial cells. In heavily infected alveoli, almost all alveoli were filled with trophozoites, cysts, debris of the host cells, and occasionally phagocytic cells (macrophages and neutrophils) containing cysts or trophozoites were found. It was noted that the cysts were very few in number (1%) compared with the number of the trophozoites in nude mice in a 0.4 mm2 area of 2 micron thick lung sections. The host tissue of nude mice in this study was not as strongly affected by the organisms as that in cortisone-treated rats and P. carinii pneumonia patients. In the present study the morphology of P. carinii found in nude mice was not different from that found in rats and in man.
Insights
This study details the morphology and behavior of Pneumocystis carinii in nude mice lungs. Researchers observed trophozoites and cysts, noting their attachment to alveolar cells and minimal host tissue impact.
Area of Science:
- Microbiology
- Cell Biology
- Immunology
Background:
- Pneumocystis carinii is an opportunistic pathogen causing pneumonia in immunocompromised individuals.
- Understanding its morphology and behavior is crucial for developing effective treatments.
- BALB/c nude mice serve as a model to study P. carinii infections.
Purpose of the Study:
- To describe the morphology, development, and behavior of Pneumocystis carinii.
- To investigate the interaction between P. carinii and alveolar epithelial cells in nude mice.
- To assess the host tissue response to P. carinii infection in this model.
Main Methods:
- Phase-contrast microscopy for observing live trophozoites.
- Paraffin and semi-ultrathin sectioning for detailed morphological analysis.
- Staining techniques including Gomori's methenamine silver nitrate (GMS) and Giemsa.
Main Results:
- Trophozoites are ameboid, 2-8 microns, with vacuoles and a nucleus.
- Intracystic bodies mature and become independent within developing cysts.
- P. carinii attaches to Type I alveolar epithelial cells; heavy infections fill alveoli with trophozoites, cysts, and debris.
- Cysts are rare (1%) compared to trophozoites in nude mice lungs.
- Host tissue response in nude mice is less severe than in cortisone-treated rats or human patients.
Conclusions:
- The morphology of P. carinii in nude mice is consistent with findings in rats and humans.
- Nude mice exhibit a distinct, less severe host response to P. carinii compared to other models.
- This study provides detailed insights into P. carinii's lifecycle and host interaction in a relevant animal model.