Abstract
When 0.4mg estrogen (diethylstilbestrol) is administered to White Leghorn chicks daily for 10 consecutive days from 60 days of age, different degrees of increase in the immunological response of serum to vitellin are observed among individual birds. The degree of sensitivity for the serum vitellin production is expressed as the dilution rate of serum for a positive vitellin response. This is shown by the following equation as described by Yamamato and Nakagawa (1965)9:
Y=bX+k, (1),
where Y is the dilution rate of serum, X is the number of days injected with estrogen, b is a regression coefficient and k is a constant.
The regression equations were obtained from 7 groups of White Leghorn male and female chicks of different origins. In these equations, the correlation between b and k become apparent. When k was plotted against b, the mode of distribution of k was different among the groups of the females but not among those of the males.
Based on the correlation between b and k in the equation (1), another equation was obtained:
Y'=b'X'+k', (2),
where Y' is k of the equation (1), X' is b of the equation (1), b' is a regression coefficient and k' is a constant. Comparing the equation (2) among the above seven groups of White Leghorn males and females, it became evident that b' (designated as b-k regression) differed significantly among the groups of females but the differences among the male groups were not significant.
The effect of gonadoectomy on b and k of the equation (1) and on b' of the equation (2) was examined using 6 groups of males and females. Ovaries and testes were removed on 40 days of age. Among these groups of gonadoectomized chicks, the difference in k was evident while the difference in b was not statistically significant. Gonadoectomy did not affect b' (b-k regression) in both males and females. This suggests that the difference in b' between the normal males and females may be due to other factor(s) than the presence of gonad.
