Yamada H, Kuraishi R, Hirai S, Katoh Y, Fusetani N, Amikura R, Okano K, Nagano H
Department of Physiological Chemistry, Tokyo Metropolitan Institute of Medical Science, Japan.
J Cell Physiol. 1988 Aug;136(2):326-32. doi: 10.1002/jcp.1041360216.
Effects of hydroxyurea, an inhibitor of ribonucleotide reductase, on cleavage of starfish embryos were studied. In the presence of 1 mM hydroxyurea, fertilized eggs of the starfish, Asterina pectinifera, cleaved up to the 256-cell stage and decomposed before blastulation. Before the 16-cell stage, each blastomere contained a normal nucleus or chromosomes with mitotic apparatus. The cleavage after the 16-cell stage was slow compared to the control embryos, and not all blastomeres contained a nucleus or normal chromosomes. During the fifth cell division (between 16-cell- and 32-cell-stage embryos), chromatin mass unassociated with the mitotic apparatus remained near the cleavage furrow. When hydroxyurea was removed before the 16-cell stage, the embryos developed to normal bipinnalia larvae via normal blastulae. However, the embryos were disintegrated before blastulation when hydroxyurea was removed after the 32-cell stage. DNA synthesis was normally observed before the 16-cell stage but not after the 16-cell stage, but dNTP contents in the embryos remained low throughout development in the presence of hydroxyurea. The achromosomal cleavage observed in the presence of hydroxyurea was reversed by the combination of extracellular dAR and dCR. Therefore, it is assumed that the synthesis of dNTPs required for DNA synthesis in the presence of hydroxyurea occurs via the salvage pathway using deoxynucleosides (dNR) (dNR to dNTP via dNMP and dNDP).
研究了核糖核苷酸还原酶抑制剂羟基脲对海星胚胎分裂的影响。在1 mM羟基脲存在的情况下，多棘海盘车的受精卵分裂至256细胞期，然后在囊胚形成前分解。在16细胞期之前，每个卵裂球都含有一个正常的细胞核或带有有丝分裂器的染色体。与对照胚胎相比，16细胞期之后的分裂较慢，并非所有卵裂球都含有细胞核或正常染色体。在第五次细胞分裂期间（16细胞期至32细胞期胚胎之间），与有丝分裂器无关的染色质团块留在卵裂沟附近。如果在16细胞期之前去除羟基脲，胚胎会通过正常囊胚发育成正常的双羽幼虫。然而，如果在32细胞期之后去除羟基脲，胚胎会在囊胚形成前解体。在16细胞期之前正常观察到DNA合成，但在16细胞期之后未观察到，不过在羟基脲存在的情况下，整个发育过程中胚胎中的dNTP含量仍然很低。在羟基脲存在下观察到的无染色体分裂可通过细胞外dAR和dCR的组合逆转。因此，可以推测在羟基脲存在的情况下，DNA合成所需的dNTPs的合成是通过利用脱氧核苷（dNR）的补救途径进行的（dNR通过dNMP和dNDP转化为dNTP）。
