Hamburger V, Yip J W
J Neurosci. 1984 Mar;4(3):767-74. doi: 10.1523/JNEUROSCI.04-03-00767.1984.
Extirpation of the wing bud in 2-day chick embryos results in a conspicuous degeneration of neurons in both populations of brachial dorsal root ganglia (DRG). Daily injections of 1 to 6 micrograms of nerve growth factor (NGF), beginning at 4 1/2 days of incubation, rescued all small, late differentiating (DM) neurons and approximately 50% of large, early differentiating (VL) neurons, which would have died otherwise. The fact that NGF is an effective substitute for the hypothetical trophic maintenance factor for DRG which is normally produced by limb tissues strengthens our belief that NGF is identical with this factor. The control experiment, i.e., wing extirpation without NGF injections, revealed an inconsistency with previous data. Experiments on a number of different neuronal units had shown rather consistently that the period of experimentally induced neuron degeneration, caused by removal of the target, is synchronous with the period of normally occurring neuronal death in the same neuronal unit. This synchrony rule is violated by the VL population of brachial DRG. In this unit, the peak of degeneration resulting from wing bud extirpation occurs considerably earlier than the peak of normally occurring neuronal death. The competition hypothesis for the explanation of neuronal death had been based, in part, on the synchrony rule. We discuss the question of whether the deviation from the synchrony rule observed in our material represents a serious challenge to the competition hypothesis.
切除2日龄鸡胚的翅芽会导致臂部背根神经节（DRG）的两类神经元明显退化。从孵化4.5天时开始，每天注射1至6微克神经生长因子（NGF），挽救了所有小型、晚期分化（DM）神经元以及约50%的大型、早期分化（VL）神经元，否则这些神经元将会死亡。NGF是肢体组织通常产生的DRG假定营养维持因子的有效替代物，这一事实增强了我们认为NGF与该因子相同的信念。对照实验，即未注射NGF的翅芽切除实验，揭示了与先前数据的不一致。对许多不同神经元单位的实验相当一致地表明，由去除靶标引起的实验性诱导神经元退化期与同一神经元单位中正常发生的神经元死亡期是同步的。臂部DRG的VL神经元群体违背了这一同步规则。在这个神经元单位中，翅芽切除导致的退化高峰比正常发生的神经元死亡高峰早得多。神经元死亡解释的竞争假说部分基于同步规则。我们讨论了在我们的材料中观察到的与同步规则的偏差是否对竞争假说构成严重挑战的问题。
