Simpson A M, Simpson L
J Protozool. 1976 Nov;23(4):583-7. doi: 10.1111/j.1550-7408.1976.tb03846.x.
Short pulse-labeling of log phase Crithidia fasciculata cells with [3H]thymidine allowed the autoradiographic visualization of 2 sites of replication of kinetoplast DNA situated at the periphery of the networks and separated by 180 degrees. Longer pulse-labeling led to the previously reported total peripheral labeling pattern. Pulse-labeled networks possess an intermediate density in ethidium bromide-CsCl equilibrium gradients between the densities characteristic of closed networks and open or linear DNA. Removal of ethidium bromide by several methods and treatment of intermediate band networks with RNase and pronase had no effect on the equilibrium rebanding pattern. Closed minicircles of Leishmania tarentolae are not labeled by a short pulse of intact cells with [3H]thymidine. A chase of approximately 3-4 hr is required for the appearance of radioactivity in closed minicircles, a time delay which implies the existence of intermediate events between replication and eventual covalent closure of the minicircles.
用[³H]胸腺嘧啶核苷对对数期的纤细无口虫细胞进行短脉冲标记，使得通过放射自显影能够观察到动质体DNA的两个复制位点，它们位于网络的周边，相隔180度。较长时间的脉冲标记导致了先前报道的完全周边标记模式。脉冲标记的网络在溴化乙锭-CsCl平衡梯度中具有中等密度，介于封闭网络和开放或线性DNA的密度特征之间。通过几种方法去除溴化乙锭，并用核糖核酸酶和链霉蛋白酶处理中等密度带的网络，对平衡再带模式没有影响。用[³H]胸腺嘧啶核苷对完整的利什曼原虫细胞进行短脉冲标记，不会标记其封闭的微小环。封闭的微小环中出现放射性需要大约3 - 4小时的追踪期，这种时间延迟意味着在微小环的复制和最终共价闭合之间存在中间事件。
