Etienne Wolff

Old experiments and new trends in avian sex differentiation

SummaryThe influence of steroid hormones on sex differentiation was first demonstrated in birds in 1935. Steroid female hormones injected in vivo into male embryos determined a partial or total feminization of gonads and genital ducts. Male hormones determined only the sex reversal of the ducts. Some substances of the group of androgens, such as dehydroandrosterone, had a paradoxical effect; they feminized males and masculinized females. Similar effects were observed later by several authors in all groups of vertebrates. In placentary mammals, only genital ducts were transformed. Castration of avian embryos also demonstrated the role of embryonic sexual hormones on genital ducts. These results, first obtained in vivo, were confirmed by experiments in vitro. Since then numerous studies have been undertaken on the nature of the hormone responsible for the regression of müllerian ducts in embryos of birds and other groups of vertebrates. Some authors assumed that these substances are proteins; many offered new evidence for the role of steroid sexual hormones during sex differentiation. Thus the problem appeared more complicated than it was thought at first. In recent years, synthesis of steroid sexual hormones have been demonstrated in young embryos during or even before sex differentiation; and enzymes that catalyze the synthesis of these hormones, such as hydroxysteroiddehydrogenase, also have been discovered. Further research has been oriented toward the characterization of steroid hormones by techniques of immunochemistry and labeled isotopes confirming the results obtained by other techniques. Specific proteins are being isolated in the effectors; they work as receptors of steroid hormones. Nuclear receptors of estradiol have been discovered in the embryonic gonads and in the cloacal wall at the time of sexual differentiation. Thus a mechanism can be conceived in which proteins and steroid hormones play mutual roles in the process of sex differentiation.

Analyse biochimique des facteurs déterminant la croissance de tumeurs cancéreuses humaines en culture d'organes in vitro

Abstract : The article presents a general view of biochemical analysis of factors determining organotypic growth of human malignant tumours in vitro. Two human malignant tumours of intestinal origin have been maintained for several years, and these tumours proliferate actively in the form of massive organized nodules, comprised solely of cancer cells and devoid of stroma. They conserve their initial properties. These nodules live on chick embryo organs such as the mesonephros and the liver, with which they are associated on the culture medium. Their growth is such that at each 7-day transfer they can be divided into 2 or 3 fragments, thus their number is either maintained or rapidly increased subject to the need. These nodules are used for the study of the extracts or extract fractions which favour their proliferation in vitro. (Author)

Mise en évidence par l'irradiation aux rayons X d'un phénomène de compétition entre les ébauches du tibia et du péroné chez l'embryon de poulet

Leg buds of chick embryos at Hamburger-Hamilton stages of 18-21 were irradiated by total homogeneous radiation, selective radiation applied to the anlage of tibia or fibula, or total heterogeneous radiation. Total homogeneous radiation showed the respective potencies of the anlagen of tibia and fibula and revealed competition between them, as seen by normal differentiation of tibia and deficient development or absence of fibula. Selective irradiation of either anlage suppressed the competitive effect; the protected anlage developed normally. Selective irradiation of fibula anlage prevented its development but irradiation of tibia merely reduced tibial length. Total heterogeneous irradiation of leg bud restored the competition when the tibia received 3 times more radiation than fibula anlage, although the dosage received by fibula anlage was not sufficient to prevent fibula development. The results indicate that in radiationdamaged leg bud, surviving embryonic material is preferentially utilized for tibial development at the expense of fibular development. (H.H.D.)

La culture de cellules tumorales sur des explants d'organesin vitro

Setzt man in Organkulturenin vitro kleine Teilstücke eines S180-Maustumors mit embryonalen Organen des Huhnes zusammen, so wandern die tumoralen Zellen in die explantierten Organe über, bevölkern sie und vermehren sich aktiv. Gewisse Organe wie Vorniere, Mesenterien, Darmwand, Kapsel der Leber, Haut, erweisen sich als besonders geeignet für die Einwanderung und die Vermehrung der tumoralen Zellen.

LES FACTEURS DE LA CROISSANCE DE TUMEURS ASSOCIÉES À DES ORGANES EMBRYONNAIRES DE POULET

Publisher Summary This chapter discusses a study in which numerous surgically removed human tumors were cultured in vitro in association with expiants of 8-day chick mesonephros. They retained their original structure and characteristics. A hepatic metastatic growth of the gastric epithelial tumor designated Z200 was cultured by this technique. When associated with fragments of mesonephros, tumor cells grow as solid nodules, consisting of epithelial cords surrounding alveolae. There was much proliferation in the cells of the nodules, whose rate of growth is very rapid. Some tumor expiants were separated from the mesonephros by a dialyzing membrane. They grow rapidly at the expense of dialyzing substances elaborated by the mesonephros. Such expiants were subcultured for more than 75 days. They form rather viscous solid nodules with less compact cords than when in direct association with the mesonephros. They retain their organized structure and their initial rate of proliferation. Evidence is also presented to show that it is possible to culture, directly, fragments of surgically removed human cancer for long periods with expiants of chick mesonephros.

The History of His Life and Career

As an embryologist, I cannot journey back through time further than my birth, even though an embryologist should. Out of respect for truth, I must say that I recall nothing of my life as an embryo any more than I do the few months following my birth. My earliest memories go back to the age of two or three. They are not worth bringing up, except perhaps for one: One day my father had taken me to a bathing area along the Seine, and I saw him swimming so easily in the river, that trusting in him entirely, I very daringly jumped into the Seine, which was quite deep at that spot, at least for the little fellow that I was then. I was not so easily fished out. That was a proof of the absolute confidence that I had in my parents, and also perhaps of the spirit of discovery by which I was driven even then. I might also mention that one day in Bern, in Switzerland, I broke loose from my parents and ran after a yellow streetcar which exerted an irresistible pull on me. I was rescued just in time. Was that the first sign of a spirit of discovery? There is no hint in my youth of my vocation as a future embryologist and teratologist.