Lance-Jones C
Brain Res. 1982 Aug;256(4):473-9. doi: 10.1016/0165-3806(82)90192-4.
Motoneuron cell death in the lumbar lateral motor column of the mouse embryo and neonate was examined to determine the timing and position of cell death with respect to events occurring in the limb. Counts of motoneurons in histological sections of the entire lumbar lateral motor column were made in mice ranging in age from 12 1/2 days of embryonic development to 20 days of neonatal life. Between 13 and 18 days of embryonic development, 67% of the motoneurons initially present in the motor column die, or approximately 3350 out of 5000 cells. Peak motoneuron cell death occurs at 14 days. No cell death occurs during the first neonatal weeks when polyneuronal muscle fiber innervation is lost. Counts of the total number of cells present at 18 days were similar to those previously reported for adult mice, suggesting that all motoneuron cell death has occurred by the end of prenatal development. In a few 13- to 14-day mouse embryos, the hindlimbs were totally filled with horseradish peroxidase (HRP) to define the boundaries and size of the lateral motor population which projects to the limb at early stages. Counts of HRP labeled motoneurons in selected lumbar cord segments were close to the total number of lateral motoneurons in the same segments. As the HRP injections were made prior to or at the onset of cell death, these observations indicate that many cells which die have sent axons into the limb.
对小鼠胚胎和新生小鼠腰外侧运动柱中的运动神经元细胞死亡进行了检查，以确定细胞死亡的时间和位置与肢体中发生的事件的关系。在年龄从胚胎发育12.5天到新生期20天的小鼠中，对整个腰外侧运动柱的组织切片中的运动神经元进行计数。在胚胎发育的13至18天之间，最初存在于运动柱中的67%的运动神经元死亡，即5000个细胞中约有3350个死亡。运动神经元细胞死亡高峰发生在14天。在多神经元肌肉纤维神经支配丧失的新生期第一周内没有细胞死亡。18天时存在的细胞总数计数与先前报道的成年小鼠相似，这表明所有运动神经元细胞死亡在产前发育结束时已经发生。在一些13至14天的小鼠胚胎中，后肢完全充满辣根过氧化物酶（HRP），以确定在早期投射到肢体的外侧运动神经元群体的边界和大小。在选定的腰段脊髓中对HRP标记的运动神经元进行计数，结果接近同一段中外侧运动神经元的总数。由于HRP注射是在细胞死亡之前或开始时进行的，这些观察结果表明，许多死亡的细胞已经将轴突发送到肢体中。
