体外培养的绒毛细胞中普通脆点的研究

体外培养绒毛细胞,用缺叶酸培养基或在培养基中加入大量鸟苷或胸苷,造成脱氧核苷酸库的不平衡,导致染色体断裂和普通脆点的表达。大量鸟苷对普通脆点的诱导作用较强,而大量胸苷的作用则稍缓和。大量鸟苷与缺叶酸培养基合并使用时,诱导作用减弱,其可能原因是:缺乏叶酸使鸟苷生成受阻,脱氧核苷酸库的不平衡状态减轻。

Study on Common Fragile Sites in Chorionic Villi Cells Cultured in vitro

The chorionic cells cultured in vitro were treated with the inducing factors of fragile sites.These factors could lead to an unbalance of the dNTP pools and thus induce expression of both common fragile sites and Fra(X).Excess guanosine (250 mg/1) or thymidine (250 mg/1) was added to the culture medium 24 hours before harvest.MEM-FA medium was added 48 hrs before harvest and some of these cases were added with guanosine (250 mg/1) 24 hr before harvest.After harvest the slides were stained with Giemsa staining.Chromosome gaps and breaks were observed and recorded.Then slides were destained and G-banded to confirm the chromosome region of breaks.The expression frequencies of the common fragile site 3p14 and others in villi cells were observed.Both guanosine and thymidine had strong inducing effect on common fragile sites.Guanosine inhibited the cell growth more apparently than thymidine.After guanosine being used in MEM-FA medium,the weaker inducing effect was shown.The possible reason is that the lack of folic acid could block the synthesis of guanosine,so the unbalance of dNTP pools caused by excess guanosine tend to be balanced.Because of the counteracting effect between MEM-FA medium and guanosine or thymidine,it is suggested that these two nucleosides should not be used with MEM-FA medium together in inducing Fra(X).