Johnson J E
Mech Ageing Dev. 1979 Jul;10(6):405-43. doi: 10.1016/0047-6374(79)90022-8.
Cells from the new strain IMR-90 were examined by scanning (SEM) and transmission (TEM) electron microscopy at early, middle, and late population doubling levels. The cells are characteristically flattened and elongated and arranged in clusters from 1 to several cells thick. Long thin processes extend from the poles and sides of the cells. The number of blebs and microvilli on the cell surface varies. In later population doubling level (PDL) cultures, a larger number of cells have greater quantities of microvilli on their surface. It is suggested that the increased number of microvilli might represent an increased level of differentiation. By TEM the cells typically have elongated to oval shaped nuclei which are sometimes deeply invaginated. The cytoplasm contains a well developed Golgi region, elongated mitochondria, microtubules, filaments, a variety of vesicles, vacuoles and dense bodies and large amounts of RNA in the form of granular endoplasmic reticulum and ribosomes. Cytoplasmic appearance, particularly the number of dense bodies, varies widely at all PDL. With increasing PDL, cells tend to have nuclei with more condensed chromatin, and a cytoplasm containing less mitochondria and granular endoplasmic reticulum and more dense bodies. Also at later PDL there is a higher frequency of cells containing long, thin dense mitochondria as well as bizarre shaped mitochondria. In older populations there are many cells in a state of filamentous degeneration. Cells with large numbbers of surface projections (microvilli) tend to be correlated with an osmiophilic cytoplasm containing many filaments and numerous dense bodies.
在早期、中期和晚期群体倍增水平，通过扫描电子显微镜（SEM）和透射电子显微镜（TEM）对新菌株IMR-90的细胞进行了检查。这些细胞的特征是扁平且细长，聚集成1至几层细胞厚的簇状。长而细的突起从细胞的两极和侧面伸出。细胞表面的泡状突起和微绒毛数量各不相同。在后期群体倍增水平（PDL）培养物中，大量细胞表面有更多的微绒毛。有人认为微绒毛数量的增加可能代表分化程度的提高。通过TEM观察，细胞通常具有伸长至椭圆形的细胞核，有时细胞核会深陷。细胞质中含有发育良好的高尔基体区域、细长的线粒体、微管、细丝、各种囊泡、液泡和致密体，以及呈颗粒状内质网和核糖体形式的大量RNA。在所有PDL水平，细胞质外观，尤其是致密体的数量差异很大。随着PDL的增加，细胞倾向于具有染色质更浓缩的细胞核，以及含有较少线粒体和颗粒状内质网以及较多致密体的细胞质。同样在后期PDL，含有长而细的致密线粒体以及形状怪异的线粒体的细胞频率更高。在老龄群体中，有许多细胞处于丝状变性状态。表面有大量突起（微绒毛）的细胞往往与含有许多细丝和大量致密体的嗜锇细胞质相关。
