A radioautographic analysis of the migration and localization of trunk neural crest cells in the chick.

The author reported on the condition of the pilosebaceous apparatus in boys, and eunuchoid and astrate men. These individuals do not develop seborrhea, acne vulgaris, premature alopecia, or common baldness (1, 2). Quantitative determinations were made of urinary estrogenic, anlrogenic and gonadotropic substances before, during and after treatment with male hormone. Treatment was usually carried out by injections of testosterone propionate, usually dissolved 20 mgm. in 1.0 cc. of peanut oil. As a control, injections of the same amount of peanut oil' were given. Methyl testosterone was occasionally substituted by the oral route, or pellets of testosterone propionate were planted subcutaneously. A majority of all patients so treated developed first seborrhea, comedones, and later acne vuigaris, which condition simulated the same ones seen in sexually normal individuals. Cessation of therapy usually resulted in a striking decrease in seborrhea and the signs of acne vulgaris, both of which increased in severity on resumption of treatment. Such signs were never observed after the injection of peanut oil alone. Developing acne pustules which had undergone retrogression redeveloped signs of inflammation if treatment was soon reinstituted. All men who failed to mature sexually had little or no dandruff and did not become bald. Common baldness occurs only in sexually mature individuals of families the members of which tend to become bald. Androgenic therapy induced baldness in eunuchoid and castrate members of such families only. Cessation of treatment, as well as castration of normal men becoming bald, prevents further enlargement of bald areas, but apparently does not promote general re-. growth of hair. The author concludes that the predisposing factors, including congenital, are ineffective in production of seborrhea, acne vulgaris and premature alopeci in the absence of adequate gonadal hormone substance. Androgens cause seborrhea, and acne may result. The presence of acne bears no direct relation to the levels of estrogenic and gonadotropic substances, and needs no postulation of hypopituitarism and hypogonadism. Premature alopecia is produced by daily intramuscular injections of 20 to 30 mgm. of testosterone propionate, a dosage estimated to provide androgenic stimulation roughly equivalent to that in normal adult men. There is no evidence that premature alopecia is caused by excessive quantities or unusual types of androgens. The normal androgenic secretion of the suprarenal gland does not incite bald-

Male hormone stimulation is prerequisite and an incitant in common baldness

The Roles of Experience in the Development of Behavior and the Nervous System

Evidence has been presented to support the concept that malignant tumors are postembryonic differentiations superimposed upon the process of tissue maintenance and renewal. Malignant stem cells are derived from normal stem cells. They have a capacity for proliferation and differentiation that operates at a different level of control than the normal. Even so, malignant stem cells are responsive to enviornmental control, suggesting that it may be possible to direct their differentiation or at least to control their ability to replicate. A tumor is a caricature of normal tissue and appears undifferentiated because of the preponderance of undifferentiated proliferating stem cells in relationship to the number of cells that have differentiated and become benign.

Neoplasms, differentiations and mutations.

Experimental intersexuality. The effects of estrogens on the antenatal sexual development of the rat

Sex-Modification in the Chick Embryo Resulting from Injections of Male and Female Hormones.

T HE interpretation by Lillie (I916, 1917) that the freemartin is the result of the action of male sex hormones led to the belief that the nature of the processes involved in embryonic sex-transformation might be analyzed experimentally in the laboratory. As a consequence, experiments were devised to duplicate in the chick embryo Nature's experiment in cattle twins. By grafting gonad tissue, either embryonic or adult, to a host embryo, a relationship can be set up which simulates rather closely that existing between cattle twins in utero, inasmuch as the significant means of communication between graft and host is by way of the blood circulation of the embryonic membranes. Minoura (1921), the first to make such an analysis, found intersexual structures of various grades which he believed were produced by the action of sex hormones from grafts of pieces of testis or ovary of the adult fowl. Such sex-modifications were subsequently shown not to be specific sex-hormone effects since they occur in the normal embryo with an I8 per cent frequency, which may be readily increased by certain conditions of operation and incubation, especially by low temperature at a critical period in development (Willier and Yuh, 1928; see Willier, 1932, pp. 143-49, for a review of this topic). Furthermore, in reciprocal experiments it has been shown that the gonad-forming area or rudiment of indifferent stages fails to undergo sex-reversal if grafted to the chorioallantois of host embryos already differentiated as to sex (Willier 1927, 1933). Self-differentiation of the indifferent rudiment or area occurs regardless of the sex of the host embryo. In one exceptional case among these, an ovotestis differentiated from a gonadforming area of a 3i-somite donor grown for 9 days on a female host. In this case the gonad area was apparently determined as a left testis, the rudimentary cortical component of which was activated by female sex hormones of the host. The general lack of cases of sex-modification in the chick embryo has led to various hypotheses. One view is that sex hormones are absent, the early differentiation being dependent entirely upon genetic determiners of sex. Another is to the effect that, if sex hormones are present, they fail to participate in the processes of sex-differentiation in the embryo. Still a third view is that embryonic sex hormones are either different or have a different mode of action from the sex hormones which have been demonstrated to play such an important r61e in controlling sex characters in the chick after hatching. Such conclusions are not justified on the basis of what is known concerning sex-reversal

The Modification of Sex Development in the Chick Embryo by Male and Female Sex Hormones

Skin Transplants between Embryos of Different Breeds of Fowl.

vided the molecules have a density equal to that of most proteins, i.e., 1.33 gm./cc. This value of the molecular weight is about one-third of that secured from the diffusion constant alone as previously measured by the method of Anson and Northrop. ' The difference in the results from the two methods is not unexpected and has been found for other proteins. The molecular weight may, of course, be computed from the sedimentation constant alone, without use of the diffusion coefficient, provided it is assumed that the molecules are spherical. Applying Stokes's law, the radius of the molecule may be calculated, and if the density is assumed to be 1.33 as before, the molecular weight becomes 200,000. This represents a minimum value, since the spherical form is most favorable for rapid sedimentation. The fair agreement between the two values secured from the sedimentation constant with and without the diffusion constant indicates a shape for the visual purple molecule which is probably not greatly different from that of a slightly oval particle.

https://www.pnas.org/content/pnas/24/4/176.full.pdf

Biological Differences in the Action of Synthetic Male Hormones on the Differentiation of Sex in the Chick Embryo

https://www.pnas.org/content/pnas/24/10/446.full.pdf

B. H. Willier

Papers

Sex-Modification in the Chick Embryo Resulting from Injections of Male and Female Hormones.

The Modification of Sex Development in the Chick Embryo by Male and Female Sex Hormones

Skin Transplants between Embryos of Different Breeds of Fowl.

Biological Differences in the Action of Synthetic Male Hormones on the Differentiation of Sex in the Chick Embryo

Feather Characterization as Studied in Host-Graft Combinations Between Chick Embryos of Different Breeds.