Yoshikawa H, Yoshida Y
Z Parasitenkd. 1986;72(4):463-77. doi: 10.1007/BF00927890.
Pneumocystis carinii has generally been distinguished in three developmental stages, namely, trophozoite, precyst and cyst. The fine structure of the pellicle--the plasma membrane and the outer layer existing outside this plasma membrane--of each stage was studied by freeze-fracture technique. By this technique, P. carinii was cleaved through the cytoplasm or through the hydrophobic region of the plasma membrane, and the cross-fractured face of the outer layer was revealed on the replicas. The outer layer, which is electron-dense in the thin section, consisted of numerous fine granules about 15 nm in diameter in freeze-fracture images, whereas the electron-lucent middle layer which appeared in the precyst and cyst was less granular. Measurement of the intramembranous particles (IMP) also was carried out. The number of IMP per square micrometer of the plasma membrane of the trophozoite was 1,512 +/- 125 on the P face and 417 +/- 44 on the E face. In the precyst, the IMP density decreased, and 1,037 +/- 56 on the P face and 262 +/- 22 on the E face. In the cyst, it further decreased, nd 875 +/- 59 and 150 +/- 20 respectively. It is generally assumed that the density of IMP is related to the physiological activity of the cell membrane, so that the present results obtained in P. carinii suggest that the trophozoite is the most active stage, and that metabolic activity of the pellicle gradually decreases with the progress of development to the precyst then to the cyst.
卡氏肺孢子虫通常可分为三个发育阶段，即滋养体、包囊前期和包囊。采用冷冻蚀刻技术研究了各阶段表膜（质膜及存在于该质膜外的外层）的精细结构。通过该技术，卡氏肺孢子虫在细胞质或质膜的疏水区域被劈开，外层的交叉断裂面在复制品上得以显示。在超薄切片中电子密度较高的外层，在冷冻蚀刻图像中由许多直径约15nm的细颗粒组成，而在包囊前期和包囊中出现的电子透明中层颗粒较少。还对膜内颗粒（IMP）进行了测量。滋养体质膜每平方微米的IMP数量，在P面为1512±125，在E面为417±44。在包囊前期，IMP密度降低，P面为1037±56，E面为262±22。在包囊中，IMP密度进一步降低，分别为875±59和150±20。一般认为IMP密度与细胞膜的生理活性有关，因此卡氏肺孢子虫的目前结果表明，滋养体是最活跃的阶段，并且随着发育进展到包囊前期再到包囊，表膜的代谢活性逐渐降低。
