The box jellyfish Chiropsalmus quadrumanus (Chirodropida: Cubozoa: Cnidaria) is common in warm waters. Although it assumed that external fertilization a characteristic of Chirodropida, the life history C. not yet known since its reproductive behavior has never been described, nor polyp found nature. As result, absence documentation behavior, we sought to test hypothesis through histological ana...

In birds, the mechanism of sex determination is unknown: it is uncertain whether the female-specific W-chromosome encodes an ovary-determining gene analogous to the mammalian testisdetermining gene, or whether testis determination is dependent on a double dose of a Z-chromosome gene(s) that escapes inactivation. In addition, birds do not carry a homologue to the Sry gene and the identity of the...

Dioxins are persistent organic pollutants interfering with endocrine systems and causing reproductive and developmental disorders. The objective of our project was to determine the impact of an in utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on reproductive function of male and female offspring in the rat with a special emphasis on the immature period. We used a low dose of TCDD...

In birds, the mechanism of sex determination is unknown: it is uncertain whether the female-specific W-chromosome encodes an ovary-determining gene analogous to the mammalian testisdetermining gene, or whether testis determination is dependent on a double dose of a Z-chromosome gene(s) that escapes inactivation. In addition, birds do not carry a homologue to the Sry gene and the identity of the...

In birds, the mechanism of sex determination is unknown: it is uncertain whether the female-specific W-chromosome encodes an ovary-determining gene analogous to the mammalian testisdetermining gene, or whether testis determination is dependent on a double dose of a Z-chromosome gene(s) that escapes inactivation. In addition, birds do not carry a homologue to the Sry gene and the identity of the...

In birds, the mechanism of sex determination is unknown: it is uncertain whether the female-specific W-chromosome encodes an ovary-determining gene analogous to the mammalian testisdetermining gene, or whether testis determination is dependent on a double dose of a Z-chromosome gene(s) that escapes inactivation. In addition, birds do not carry a homologue to the Sry gene and the identity of the...

Recent studies point to a key role for the estrogen synthesizing enzyme P450 aromatase (P450 arom) in ovary determination in fish, birds and reptiles. It is unclear whether estrogen synthesis is important in sex determination of Xenopus gonad. To determine whether the aromatase gene is transcribed in the gonads of Xenopus tadpoles during the sex determination, we cloned a P450 arom cDNA and exa...

The gonads of 107 spontaneous, chromosomal mosaic, day-15 fetal hermaphrodites derived from BALB/cWt strain male mice are described and photographs of seven gonads representative of the major types are presented. There were 16 ovaries, 15 testes, and 183 ovotestes. The ovotestes contained on the average more testicular tissue than ovarian, and the ovarian tissue was more frequently located at t...

The history of ideas on how the sexes became divided spans at least three thousand years. The biblical account of the origin of Eve, and the opinions of the philosophers of classical Greece, have unexpected bearings on present-day ideas. The scientific study of sex determination can be said to have begun in the 17th century with the discovery of spermatozoa, but the origin and function of the "...

G O N A D A L inversion produced by sex hormones has been studied by many authors trying to understand sex differentiation and its hormonal control. The work of Dantchakoff (1935), Wolff & Ginglinger (1935) and Willier, Gallagher & Koch (1935), who studied sex inversion in genetically male chick gonads caused by the action of estrogens, as well as work done since then on birds and other vertebr...