Masculinization

MASCULINIZATION (from Latin masculinus - male), the appearance of male characteristics in a female, usually as a result of the presence of the male sex hormone in the female organism. Masculinization occurring without the introduction of the male sex hormone from the outside is a consequence of bisexuality (see). The bisexual nature of the chicken was established by the studies of M. Zavadovsky, Benoit, and others. The extinction of ovary activity in the chicken leads to the appearance of a number of rooster characteristics (crowing, instinct, comb). After the removal of the ovary in a chicken, over a more or less prolonged period, a right gonad develops, which in its structure approaches a testis to one degree or another. At the same time, the chicken acquires rooster characteristics—comb, voice, and instinct, along with rooster plumage and spurs (a consequence of castration, see). In amphibians, this kind of masculinization is impossible, because the male sex is bisexual in them. The same apparently applies to mammals. Cases of the appearance of a beard and mustache in previously normal women can be interpreted as a manifestation of hirsutism (see Hirsutismus), depending on a hypernephroma of the adrenal cortex (Mathias, Apert, and others). A slight development of hair on the chin and at the corners of the upper lip in women, predominantly elderly, must be regarded as a sign not depending on the hormone of the sex glands. This sign also manifests itself in castrated men. Masculinization by the introduction of the male hormone from the outside was obtained as a result of transplanting testes to a castrated female. Such an experiment was performed by Steinach, who coined the term masculinization (Maskulierung), and then repeated by a number of authors on amphibians, birds, and mammals. When testes are transplanted to castrated female guinea pigs, the latter exhibit male behavior, as well as the development of morphological characteristics of the male sex—change in the skeleton, transformation of the clitoris into a penis-like organ, and so on. In the studied classes of vertebrate animals (amphibians, birds, mammals), masculinization is the result of the intrasecretory activity of the male gonad functioning in the female organism. Individual cases related hereto have not yet received a satisfactory explanation, for example, gynandromorphism (see), described in birds, amphibians, and mammals. This phenomenon boils down to the literal manifestation of characteristics of both sexes. Cases are known when on one side there was a testis and correspondingly a vas deferens and seminal vesicle, and on the other—an ovary with the corresponding parts of the female genital apparatus. The explanation for such partial masculinization must be sought in a defect of the early stage of development, perhaps in an incorrect distribution of sex chromosomes already at the two-blastomere stage. The situation is different in insects than in vertebrate animals, where cases of full or partial masculinization (gynandromorphism, intersexuality) have also been observed. In invertebrate animals, the dependence of sex characteristics on the sex hormone has in most cases not been detected. Thus, the mechanism of masculinization must receive a different interpretation. The possibility of the influence of nerve ganglia is not excluded, which follows from the experiments of Finkler. By transplanting heads from a male to a female in water scavenger beetles (Hydrophilus piceus), Finkler obtained partial masculinization of females, which exhibited male behavior. Partial masculinization of insects occurring without surgical intervention is regarded as the result of a disturbance in the distribution of sex chromosomes at early stages of development.