| Objective To observe the growth , development and morphological structure of Pneumocystis Carinii in the lung tissue of Wistar ratsMethod The experimental group was consisted of Wistar rat models of Pneumocystis Carinii pneumonia established by subcutaneous injection of dexamethasone sodium phosphate. No injection was given to the rats in the control group. The impression preparations of the lung tissue were processed by Wright-Giemsa stain. Optic microscope was used to detect and observe Pneumocystis Carinii. Slices and specimens for transmission electron microscope and scanning electron microscope were made from the samples of lung tissue. Optic microscope, transmission electron microscope and scanning electron microscope were used for the observation of the growth, development and morphological structure of Pneumocystis Carinii as well as the pathological change of the lung.tissues of the infected rats. Digital image analytic technique was used to measure the various morphological indexes of the Pneumocystis Carinii cysts.Result Optic microscope with oil immersion lens was used to examine the impression preparations of the lung tissue processed by Wright-Giemsa stain. The cysts and trophozoites were clearly observed, more often in the pulmonary alveoli while rarely in the cells. No Pneumocystis was detected in the control group. The positive detection rate was 57.14% in the experimental group. Cysts became the main observation from week 4-5, while trophozoites were the main observation after week 7-8. Under the scanning electron microscope, the Pneumocystis Carinii manifested as either smooth-surfaced or rough-surfaced. Three conditions were observed in the rough-surfaced: dense microvilli, tubular structures and granular substances. Also observed were polypides with dent in the wall and in the process of excystation or extending the pseudopodium. Under the transmission electron microscope, three developmental stages were observed: trophozoite, precyst and cyst. Most trophozoites were observed to attach to type I pulmonary epithelial cells. Their attachment to Type II pulmonary epithelial cells was occasionally seen. Some of them extended one or more comparatively wider Pseudopodia. Nucleolus related organelles and spindle microtubules were found in some cytoplasm. The precyst phase was in three forms: early, intermediate and late form and synaptonemal complexes indicating meiosis were found in precyst. One thickening portion with a pore was observed in the wall of the cyst. In week 10, Pneumocystis Carinii can be seen in the pulmonary septum and trachea in the experimental rats. The cysts of the Pneumocystis Carinii were measured by digital image processing techniques. The mean numerical value of the major diameter, minor diameter, projected area, volume, circumference, equivalent diameter and sphericity was 4.8159μm, 3.6923μm,13.07μm~2 ,36.76μm~3 ,14.29μm,4.03μm and 0.8 respectively. HE stained slices were observed under optic microscope. In week 7-8, the pulmonary alveoli of the experimental rats were filled with a large quantity of polypides and exudates. Type II pulmonary cells were found in exfoliation. Thickening of the interalveolar septum was noticed. Under transmission electron microscope, Pneumocystis Carinii was seen in the lung tissues in which fibrous change was observed. Under transmission electron microscope, a lot of vacuoles and electron-dense granules were seen in the cytoplasm of type II pulmonary epithelial cells. In the infected Type II pulmonary epithelial cells with polypides, the cell pellicle protruded and formed plasmalemma alveolus. The nucleolus membrane was invaginated and the chromosome was fiber-like and circumvolated.Conclusion Using Wright-Giemsa re-stains method for the detection of Pneumocystis Carinii has the advantages of easy operation, and clear observation of the polypides. It is ideal for the detection of Pneumocystis Carinii in common laboratories. We are the first in China to report the observation that there are some tubers on the surface of body and in the process of excystation and fibrosis lung tissue in positive rat under scanning electron microscope. As far as we know, there has been no report home or abroad either on the observation of the three developmental stages, trophozoite, precyst and cyst, of Pneumocystis Carinii under transmission electron microscope, or on the finding of the attachment of trophozoites to type II pulmonary epithelial cells and tracheas. There are fewer reports on the observation of a thickening portion with a pore in the wall of the cyst. Data about Pneumocystis Carinii cysts, which are acquired by digital image analytic technique, amplify biological data of Pneumocystis Carinii and provide the reference for etiological diagnosis. |
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