Ferguson M J, Gaulden M E, Seibert G B
Environ Mutagen. 1985;7(4):547-61. doi: 10.1002/em.2860070413.
Mitomycin C (MMC) induces acentric chromosome fragments in the neuroblast (Nb) of the grasshopper embryo (Chortophaga viridifasciata) after acute and chronic exposure to concentrations ranging from 10(-8) to 10(-4) M, the dose response being essentially linear up to 10(-5) M. Because Colcemid is not used in the Nb assay, it was possible to detect two additional effects of MMC: (1) Prolonged retardation of many cells occurs when they reach very late prophase; the chromosomes continue condensing and lose their orderly prophase orientation, and the nuclear envelope becomes increasingly fragile. Such cells, which were observed after both acute and chronic exposure, give the false impression of being c-metaphases when they are fixed and squashed. The frequency of retarded very late prophases and the duration of retardation are related to MMC concentration and time of exposure. A rationale is presented supporting the idea that the events associated with retarded very late prophase result from MMC effects on the nuclear envelope. (2) MMC significantly increases the frequency of Nb's with attenuated centromeres at the beginning of early anaphase, an effect that appears to be caused by a delay in the repulsion of sister chromatids that usually occurs immediately after centromere separation begins.
在急性和慢性暴露于浓度范围为10⁻⁸至10⁻⁴M的丝裂霉素C（MMC）后，蝗虫胚胎（绿牧草蝗）的神经母细胞（Nb）中会诱导产生无着丝粒染色体片段，剂量反应在10⁻⁵M之前基本呈线性。由于在Nb检测中未使用秋水仙酰胺，因此有可能检测到MMC的另外两种效应：（1）许多细胞在到达极晚期前期时会出现延长的延迟；染色体继续浓缩并失去其有序的前期取向，核膜变得越来越脆弱。在急性和慢性暴露后均观察到此类细胞，当它们固定并压片时，会给人一种处于c中期的错误印象。极晚期前期延迟的频率和延迟的持续时间与MMC浓度和暴露时间有关。提出了一种理论依据，支持与极晚期前期延迟相关的事件是由MMC对核膜的影响导致的这一观点。（2）MMC显著增加了早期后期开始时着丝粒减弱的Nb的频率，这种效应似乎是由姐妹染色单体通常在着丝粒分离开始后立即发生的排斥延迟引起的。
