Optic Nerve Hypoplasia in the Fetal Alcohol Syndrome

Topics: Nervous system, Blood alcohol content, Axon Pages: 4 (1251 words) Published: April 19, 2007
In the United States of America, one out of every seven hundred and fifty children is born with fetal alcohol syndrome (FAS). Mothers who consume alcohol anytime during pregnancy, puts their children at risk for multiple constellations of abnormalities when they are born. A common condition observed in children affected is optic nerve hypoplasia, which basically is the underdevelopment of the optic nerve during pregnancy. The affected child has abnormal shaped eyes that appear closer together, which can contribute to the poor visual acuity and their dysmorphic facial features shown up to ninety percent of the births. Unilateral may occur infrequently in one eye and more commonly in both eyes known as bilateral optic disc hyperplasia. Nystagmus is also associated with over half of the affected children. The optic nerve head is relatively smaller in affected children, then in a normal child. Axons are neurons that form the optic nerve and are myelinated. Since there is a loss of axons in the nerve during optic nerve hypoplasia (ONH), it compensates for the loss of retinal ganglion cells. A lot of the visual disabilities results are located on the retinal ganglion cells when alcohol affects the nervous system. In order to develop a model for optic nerve hypoplasia, researchers used mice as a model for alcohol treated animals instead of humans.

Ethanol is injected into the mice during a period of time where the forebrain target tissues and the retinal ganglion cells are undergoing cell division and the axons are grown into the optic stalk. This period is called gestation, which can appear on day eleven or day twelve. Throughout this experiment the size of the optic nerve, and the calibre and number of myelinated axon cells present is measured.

In order for the mice to become pregnant they were mated overnight. Twenty five percent of ethanol is injected into the pregnant female mice and a control mouse is injected with saline at the same time during...
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