Sandberg G, Ernström U
Int Arch Allergy Appl Immunol. 1979;60(4):407-13. doi: 10.1159/000232371.
DNA synthesis in guinea pig thymocytes suspended in RPMI 1640 medium increased to a peak after 4-5 h in culture and was followed by increased mitotic activity, indicating that many thymocytes in S phase proceeded through G2 into mitosis. Addition of L-alanine to the medium markedly increased the DNA synthesis within 1 h and the mitotic frequency from 6 h. The increase in DNA synthesis when L-alanine was present in the medium was thus caused by an increased number of cells in S phase. Human thymocytes cultured in RPMI 1640 for 18 h had a low mitotic frequency. Addition of L-alanine immediately started DNA synthesis in the arrested thymocytes resulting in increased mitotic activity from 6 h later. The results show that L-alanine is a growth factor for guinea pig and human thymocytes and should be included in tissue culture media used for such cells. Growth of thymocytes in vitro was partly synchronized, and the mitotic studies indicated that many cells had entered S phase near the start of incubation.
悬浮于RPMI 1640培养基中的豚鼠胸腺细胞，其DNA合成在培养4 - 5小时后达到峰值，随后有丝分裂活性增加，这表明许多处于S期的胸腺细胞进入G2期并进而进入有丝分裂。向培养基中添加L - 丙氨酸可在1小时内显著增加DNA合成，并从6小时起增加有丝分裂频率。因此，培养基中存在L - 丙氨酸时DNA合成的增加是由S期细胞数量增加所致。在RPMI 1640中培养18小时的人胸腺细胞有丝分裂频率较低。添加L - 丙氨酸可立即启动停滞的胸腺细胞中的DNA合成，从而从6小时后导致有丝分裂活性增加。结果表明，L - 丙氨酸是豚鼠和人胸腺细胞的生长因子，应包含在用于此类细胞的组织培养基中。胸腺细胞的体外生长部分同步，有丝分裂研究表明许多细胞在培养开始时附近进入S期。
