Cell proliferation is not required for the initiation of early cleft formation in mouse embryonic submandibular epithelium in vitro.
Cell proliferation is not required for the initiation of early cleft formation in mouse embryonic submandibular epithelium in vitro.
复制标题
体外小鼠胚胎颌下上皮早期裂隙形成的启动不需要细胞增殖。
作者：
Y. Nakanishi;Toshiteru Morita;H. Nogawa
采用x射线照射法分析了细胞增殖在早期小鼠胚胎颌下上皮裂隙形成中的作用。当12天中期的腺体暴露在200 rad的x射线下时，生长严重迟缓。相比之下，12天晚期和13天早期的腺体与对照腺体一样，生长正常，持续时间长达40小时。两种情况下，它们都在培养10小时内形成浅裂缝。在1000 rad的辐照下，12天中期的腺体完全不生长，但在培养20 h内形成裂缝，随后迅速退化。在相同的条件下，12天后期腺体的生长发育迟缓，直到培养10 h，上皮大小略有增加，但在6-10 h内也观察到裂缝形成，与对照腺体相同。当暴露于1000 rad的x射线剂量时，13天早期和12天晚期的腺体表现出相似的放射敏感性；培养后6-10 h，上皮内最初的窄裂加深，并开始形成新的裂缝。[3H]胸腺嘧啶掺入研究显示，1000 rad的剂量可使12天中期和晚期腺体的DNA合成分别减少72%和65%。x射线照射后12天腺的组织学检查显示，培养6 h时上皮内很少见有丝分裂象。Aphidicolin是一种特异性的DNA合成抑制剂，不能阻止12天晚期腺体的裂口形成。在本实验中，89%的DNA合成被抑制。用阿霉素治疗x射线照射12天后的腺体，可阻断92%的DNA合成，但不能阻止裂口的形成。这些结果表明，在体外形态发生早期，小鼠胚胎下颌骨上皮的裂缝形成既不需要细胞分裂，也不需要DNA合成。
An X-ray irradiation method was employed to analyse the role of cell proliferation in vitro in the cleft formation of mouse embryonic submandibular epithelium at early stages. When the mid 12-day gland was exposed to 200 rad of X-rays, the growth was severely retarded. In contrast, late 12-day and early 13-day glands grew apparently in a normal fashion, as did the control gland, for up to 40 h. In either case, they formed shallow clefts within 10 h of culture. With 1000 rad irradiation, the mid 12-day gland did not grow at all, but formed clefts within 20 h of culture followed by a rapid degeneration. Under the same conditions, the growth of the late 12-day gland, which was at the stage just before branching, was retarded until 10 h of culture, followed by a slight increase in epithelial size, but cleft formation was also observed within 6-10 h, as in the control gland. When exposed to a dose of 1000 rad of X-rays, the early 13-day and the late 12-day glands exhibited similar radiosensitivity; the initial narrow clefts in the epithelium deepened and new clefts began to form within 6-10 h of culture. [3H]thymidine incorporation studies revealed that a dose of 1000 rad reduced DNA synthesis of mid and late 12-day glands by 72 and 65%, respectively. Histological examination of X-irradiated late 12-day gland showed that mitotic figures were rarely seen in the epithelium at 6 h of culture. Aphidicolin, a specific inhibitor of DNA synthesis, could not halt the cleft formation of the late 12-day gland. In this experiment 89% of DNA synthesis was inhibited. Treatment of an X-ray irradiated late 12-day gland with aphidicolin blocked 92% of the DNA synthesis, but did not prevent cleft formation taking place. These results indicate that neither cell division nor DNA synthesis, is required for the initiation process of the cleft formation of the mouse embryonic submandibular epithelium at early morphogenetic stages in vitro.