engleski

APOPTOSIS DURING NEUROGENESIS

Apoptosis or programmed cell death is an important phenomenon in the developrnent of the mature vertebrate nervous system. Neurogenesis produces about twice as many neurons in a given structure as survive in the adult organism. There are two types of apoptosis in developing nervous system: morphogenetic cell death and naturally occurring cell death. Morphogenetic cell death occurs during the embryonic phases of the development and participates in the morphological shaping of the brain. The creation of region-specific densities, or distribution of cells, as well as the creations of spaces, channels and holes reflect morphological cell death. For example, morphological cell death occurs during remodeling of the neural tube. Naturally occurring cell death occurs in a relatively late developmental stages, and involves the loss of a significant number of neurons in a given population (20-80%). This type of cell death may be unique to neural tissue. For many types of neurons that exhibit naturally occurring cell death, the regulation of the timing and extent of cell loss is controlled, at least in part, by influences derived form or associated with the synaptic targets of the cells and with afferent inputs. Other factors including neurotrophic agents and hormones might also be related to neuronal death. Molecular mechanisms of developmental neuronal death are extensively studied, particularly in invertebrates ; however, they are poorly studied in the brain of the humans and monkeys.

APOPTOSIS

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