Annual Cycle of Responsivity of Castrated Albino Mice to Œstrone Injection

Abstract

LAQUEUR, at the sixteenth International Congress of Physiologists held at Zurich in August last, reported that the response given by capons to a given dose of androgen varies according to the time of year, being lowest in winter and highest in summer. An analogous rhythm in the responsivity of castrated albino mice to monthly injections of 1 I.U. of cestrone has been found to exist, the response being more than three times as great in May as in November. The upper full-line curve in the accompanying figure represents the response given according to the State Hygiene Institute's method of evaluating vaginal smear tests in a group of 60 mice. In this method (not yet published), points are awarded to each smear (cornified epithelial cells only 5, sporadic nucleated cells 4, cornified and nucleated cells in approximately equal number 3, sporadic cornified cells 2, nucleated cells only 1, and absence of epithelial cells 0 points) ; maximum response in a group of 20 mice is thus 100 points. The lower curve represents the percentage of mice developing full oestrus after each injection. A second group of mice was castrated in May 1937 and injections were commenced in June. It will be seen (broken line curves) that the responsiveness attains that of the former group (castrated in January 1937) in August, and that the curves thereafter closely follow the earlier ones.