Corneal development: V. Treatment of five-day-old embryos of domestic fowl with 6-diazo-5-oxo- l-norleucine (DON)

Abstract

The embryogenesis of the corneal stroma of the domestic fowl was studied following the injection of the glutamine analog DON (6-diazo-5-oxo- l-norleucine) into the chorioallantoic veins of 5-day-old chick embryos. The 44 survivors were cilled between 1 hr and 13 days following injection. Their corneas were examined histologically and compared with those of untreated animals of similar age. All of the experimentally-treated corneas examined developed abnormally. The defects included: a temporary disappearance of portions of the endothelium; the deposition of disordered arrays of collagen fibers beneath the corneal epithelium, including a reversal in the direction of rotation of the axes of affected portions of the stromal lamellae; the appearance of stromal cysts; and the accumulation, beginning 6 days after injection, of pools of Gomori-silver-positive material within the epithelium. Abnormalities in corneal development following treatment with DON were compared with those previously obtained following administration of l-azetidine-2-carboxylic acid. The findings demonstrated that: (1) the characteristic, progressive rotation of fibril orientation which normally occurs in the outer lamellae of the avian, corneal, primary stroma is not a rigidly-determined configuration since its direction can be reversed consistently following treatment with DON; and (2) the primary stroma dictates the collagenous structure of the secondary stroma deposited within it.