Howell S H, Blaschko W J, Drew C M
J Cell Biol. 1975 Oct;67(1):126-35. doi: 10.1083/jcb.67.1.126.
A wide variety of inhibitors (drugs, antibiotics, and antimetabolites) will block cell division within an ongoing cell cycle in autotrophic cultures of Chlamydomonas reinhardtii. To determine when during the cell cycle a given inhibitor is effective in preventing cell division, a technique is described which does not rely on the use of synchronous cultures. The technique permits the measurement of transition points, the cell cycle stage at which the subsequent cell division becomes insensitive to the effects of an inhibitor. A map of transition points in the cell cycle reveals that they are grouped into two broad periods, the second and fourth quarters. In general, inhibitors which block organellar DNA, RNA, and protein synthesis have second-quarter transition points, while those which inhibit nuclear cytoplasmic macromolecular synthesis have fourth-quarter transition points. The specific grouping of these transition points into two periods suggests that the synthesis of organellar components is completed midway through the cell cycle and that the synthesis of nonorganellar components required for cell division is not completed until late in the cell cycle.
多种抑制剂（药物、抗生素和抗代谢物）会在莱茵衣藻自养培养物的正在进行的细胞周期内阻断细胞分裂。为了确定在细胞周期的何时给定抑制剂能有效阻止细胞分裂，本文描述了一种不依赖同步培养物使用的技术。该技术允许测量转变点，即后续细胞分裂对抑制剂的作用变得不敏感的细胞周期阶段。细胞周期中转变点的图谱显示它们被分为两个宽泛的时期，即第二和第四季度。一般来说，阻断细胞器DNA、RNA和蛋白质合成的抑制剂具有第二季度的转变点，而抑制核细胞质大分子合成的抑制剂具有第四季度的转变点。这些转变点具体分为两个时期表明，细胞器成分的合成在细胞周期的中途完成，而细胞分裂所需的非细胞器成分的合成直到细胞周期后期才完成。
