PERSISTENCE AFTER HYPOTHALAMECTOMY OF A TAMOXIFEN-LIKE EFFECT IN THE OVARY OF QUAIL EMBRYOS EXPOSED CYCLICALLY IN OVO TO LOW INCUBATION TEMPERATURES

Three days old quail embryos were hypothalamectomized in ovo by the de capitation technique according to Callebaut (1993). Half of these embr yos was exposed to day cyclically repeated prolonged low subnormal inc ubation temperatures (25 degrees C). The other half of these decapitat ed embryos was normally continuously incubated. As is the case for not decapitated embryos the ovaries of the first group presented a tamoxi fen like effect: cortical rim atrophy with proportional hypertrophy of the medulla and a pronounced decrease in the number of oogonia and oo cytes. By contrast the ovaries of the second group of decapitated embr yos presented a normal aspect without sterilization of the ovigerous s ex cords. It was concluded that: 1. the hypophysis, the hypothalamus o r other prosencephalic tissues play no intermediary role in the establ ishment of a tamoxifen like effect in the ovary; 2. the early embryoni c development of the quail ovary during the considered period takes pl ace without the intervention of the hypothalamus.