D E V E L O P M E N T S I N S E X U A L O R G A N O G E N E S I S
301
both in culture and as chorioallantoic grafts. The same result is obtained
with ducts from the male if they are removed before the eighth day. By
contrast, male ducts taken after the eighth day regress in culture, as well
as in chorioallantoic grafts.
Male hormones exert a selective necrotic action in culture on undifferentiated or female Mullerian ducts. If androgenic and estrogenic hormones
are added to the culture medium at the same time, the estrogenic hormone
protects the Mullerian ducts against the destructive action of the androgenic hormone. A testis associated in parabiosis with a female Mullerian
duct brings about its involution.
From all of these studies carried out by Wolff and his collaborators on
the hormonal control of sexual differentiation in birds, the following major
points emerge.
From the time of their differentiation, the gonads manufacture hormonal
substances. The action of these substances controls the direction of sexual
differentiation of the gonads and somatic sex characters. The steroid sex
hormones (estradiol, testosterone) produce effects that are very comparable
to those of the hormones from the embryonic gonads.
In completing the discussion of the birds, it should be noted that their
mode of reaction to steroid hormones brings to mind, at least in the chick
and duck, the type of reaction of certain anuran amphibians, such as
Pelodytes. The situation is one of temporary intersexuality. From this
point of view, the birds seem to be situated between the complete and
permanent sex reversal, known in certain amphibians (Pleurodeles, Xenopus,
Rana) and the teleost, Oryzias, and the mode of reaction among mammals.
In the latter group, only the opossum shows a reaction of intersexuality
of the male gonad in response to estradiol (Burns, 1955a, 1956). In this
case the nature of the reaction is like that in the chick and in Pelodytes. In
placental mammals, the gonads do not react to the effects of steroid hormones. This is a situation that has been demonstrated in Bombina among
amphibians.
D. Sexual Organogenesis in Mammals
1. Historical Review of Hormonal Effects
The main facts accumulated up to 1960 will be summarized briefly
(reviewed in Burns, 1955b, 1961; Jost, 1965; Price and Ortiz, 1965). If the
classical analysis of the freemartin effect in cattle (Lillie, 1916, 1917; Keller
and Tandler, 1916) was the beginning of experimental research on sexual
organogenesis in vertebrates, the problem of hormonal effects in sexual
organogenesis has been especially considered in mammals in more recent
years. The freemartin suggests very specifically an effect of the sex hormones of the fetus in sexual differentiations.
301
both in culture and as chorioallantoic grafts. The same result is obtained
with ducts from the male if they are removed before the eighth day. By
contrast, male ducts taken after the eighth day regress in culture, as well
as in chorioallantoic grafts.
Male hormones exert a selective necrotic action in culture on undifferentiated or female Mullerian ducts. If androgenic and estrogenic hormones
are added to the culture medium at the same time, the estrogenic hormone
protects the Mullerian ducts against the destructive action of the androgenic hormone. A testis associated in parabiosis with a female Mullerian
duct brings about its involution.
From all of these studies carried out by Wolff and his collaborators on
the hormonal control of sexual differentiation in birds, the following major
points emerge.
From the time of their differentiation, the gonads manufacture hormonal
substances. The action of these substances controls the direction of sexual
differentiation of the gonads and somatic sex characters. The steroid sex
hormones (estradiol, testosterone) produce effects that are very comparable
to those of the hormones from the embryonic gonads.
In completing the discussion of the birds, it should be noted that their
mode of reaction to steroid hormones brings to mind, at least in the chick
and duck, the type of reaction of certain anuran amphibians, such as
Pelodytes. The situation is one of temporary intersexuality. From this
point of view, the birds seem to be situated between the complete and
permanent sex reversal, known in certain amphibians (Pleurodeles, Xenopus,
Rana) and the teleost, Oryzias, and the mode of reaction among mammals.
In the latter group, only the opossum shows a reaction of intersexuality
of the male gonad in response to estradiol (Burns, 1955a, 1956). In this
case the nature of the reaction is like that in the chick and in Pelodytes. In
placental mammals, the gonads do not react to the effects of steroid hormones. This is a situation that has been demonstrated in Bombina among
amphibians.
D. Sexual Organogenesis in Mammals
1. Historical Review of Hormonal Effects
The main facts accumulated up to 1960 will be summarized briefly
(reviewed in Burns, 1955b, 1961; Jost, 1965; Price and Ortiz, 1965). If the
classical analysis of the freemartin effect in cattle (Lillie, 1916, 1917; Keller
and Tandler, 1916) was the beginning of experimental research on sexual
organogenesis in vertebrates, the problem of hormonal effects in sexual
organogenesis has been especially considered in mammals in more recent
years. The freemartin suggests very specifically an effect of the sex hormones of the fetus in sexual differentiations.