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Dead cells are observed in many developing animal tissues, but the causes of these normal cell deaths are mostly unknown. We show that about 50% of oligodendrocytes normally die in the developing rat optic nerve, apparently as a result of a competition for limiting amounts of survival signals. Both platelet-derived growth factor and insulin-like growth(More)
The signaling mechanisms that control the survival of CNS neurons are poorly understood. Here we show that, in contrast to PNS neurons, the survival of purified postnatal rat retinal ganglion cells (RGCs) in vitro is not promoted by peptide trophic factors unless their intracellular cAMP is increased pharmacologically or they are depolarized by K+ or(More)
We showed previously that oligodendrocytes and their precursors require continuous signalling by protein trophic factors to avoid programmed cell death in culture. Here we show that three classes of such trophic factors promote oligodendrocyte survival in vitro: (1) insulin and insulin-like growth factors (IGFs), (2) neurotrophins, particularly(More)
Although astrocytes constitute nearly half of the cells in our brain, their function is a long-standing neurobiological mystery. Here we show by quantal analyses, FM1-43 imaging, immunostaining, and electron microscopy that few synapses form in the absence of glial cells and that the few synapses that do form are functionally immature. Astrocytes increase(More)
During the development of the vertebrate nervous system, up to 50 percent or more of many types of neurons normally die soon after they form synaptic connections with their target cells. This massive cell death is thought to reflect the failure of these neurons to obtain adequate amounts of specific neurotrophic factors that are produced by the target cells(More)
Oligodendrocytes myelinate axons in the vertebrate central nervous system. It would, therefore, make sense if axons played a part in controlling the number of oligodendrocytes that develop in a myelinated tract. Although oligodendrocytes themselves normally do not divide, the precursor cells that give rise to them do. Here we show that the proliferation of(More)
In the embryonic nervous system, developing axons can be guided to their targets by diffusible factors secreted by their intermediate and final cellular targets. To date only one family of chemoattractants for developing axons has been identified. Grafting and ablation experiments in fish, amphibians, and birds have suggested that spinal motor axons are(More)
BACKGROUND We have shown previously that oligodendrocytes and their precursors require signals from other cells in order to survive in culture. In addition, we have shown that about 50% of the oligodendrocytes produced in the developing rat optic nerve normally die, apparently in a competition for the limiting amounts of survival factors. We have(More)