EFFECT OF GROWTHFACTOR (S) ON CEREBRAL HISTOGENESIS : ANALYSIS ON TISSUE CULTRED EXPLANT

在胚胎第13天的小鼠中，已经在体外进行了新皮层神经元发生中的细胞周期调控的分析。将植入胶原凝胶中的脑壁背内侧区的外植体在基本培养基中孵育1小时，然后在含有BUdR的基本培养基中孵育。在用BUdR（体外1.5小时）孵育30分钟后，标记指数（LI，标记/总细胞）为0.41，而先前在体内测定的LI为0.38。在接下来的7小时持续暴露于BUdR的体外LI保持在0.4，然后线性上升至渐近线0.73。这些观察结果证实：（1）在体外，在最初的1.5小时内，存在从G1到S的细胞流，（2）在随后的7小时内，G1到S的细胞流被中断，但（3）随后重新建立G1到S的细胞流。在该相同系统中，有丝分裂像仅在暴露于BUdR 5小时后才被首次标记，但随后超过2小时，所有有丝分裂都被标记。相反，在体内，所有有丝分裂都变成 ...更多信息 在BUdR暴露2小时期间标记。这意味着在从S期到M期的进程中存在短暂的停滞，这在停滞的5小时内明显被克服。细胞周期重建时间为19.2小时，G_1期、G_2期和G_2-M期分别为6.3 - 8.3小时、8.8小时和2.0 - 4.0小时。循环的离开（Q）分数（0，64）是体内值的两倍。三分之二的Q分数细胞仍然在心室上皮，导致在一个相当低的增长分数为0.73相比，在vivo.Also在体外的大脑壁外植体检查的结果是碱性成纤维细胞生长因子（b-FGF）和差距连接解偶联剂，1-辛醇。在内侧和外侧皮质区的扇区中确定LI，分别对应于区域1和40。在区域40中，暴露于b-FGF的外植体的总体LI高于对照外植体，暴露于1-辛醇的外植体的总体LI低于对照外植体。这些观察结果表明，b-FGF降低Q分数，而1-辛醇增加分数。少

Analysis of cell cycle regulation in neocortical neuronogenesis has been undertaken in vitro in the embryonic day 13 mouse. Explants of the dorsomedial region of the cerebral wall, implanted in collagen gel, were incubated for 1 hr in minimal medium and then in minimal medium containing BUdR.After 30 mm with BUdR (1.5 hr in vitro), the labeling index (LI, labeled/total cells) was 0.41 as compared to the previously determined LI of 0.38 in vivo. The in vitro LI remained at 0.4 over the next 7 hr of continued exposure to BUdR and then ascended linearly to asymptote at 0.73. These observations establish (1) that there is a flux of cells from G1 to S for the first 1.5 hr in vitro, (2) that this G1 to S flux is then interrupted for the following 7 hr but (3) that G1 to S flux is subsequently reestablished. In this same system, mitotic figures were first labeled only after a 5 hr exposure to BUdR but then over 2 more hours all mitoses became labeled. In vivo, by contrast, all mitoses become … More labeled during 2 hr of BUdR exposure. By implication there is a transient arrest in the progression from S to M phase which is evidently overcome within 5 hr of explantation. The duration of the reestablished cell cycle and those of G1, Sand combined G2-M phases were estimated to be 19.2, 6.3 -8.3, 8.8, and 2.0 -4.0 hr, respectively. The leaving (Q) fraction of the cycle (0,64) was twice the in vivo value. Two thirds of the Q fraction cells remained in the ventricular epithelium, resulting in a substantially low growth fraction of 0.73 as compared with 1.0 in vivo.Also examined in a cerebral wall explant in vitro was the consequences of basic fibroblast growth factor (b-FGF) and the gap junction uncoupling agent, 1-octanol. LI was determined in the sector of the medial and lateral cortical zones, corresponding to areas 1 and 40, respectively. In area 40, the overall LI in b-FGF-exposed explants was higher and that in 1-octanol-exposed explants was lower than the LI in control explants. Those observations suggest that b-FGF reduces Q fraction while 1-octanol increases the fraction. Less