During embryogenesis

Disruption of thyroid functions in vertebrates has been suggested to constitute a potential threat to many vital functions. For example, there is a possibility that disruption to the thyroid hormone levels during embryogenesis could result in disturbed behaviour patterns in the adult form, possibly interfering with migration in certain species and sonar functions in cetaceans. In anurans, thyroid hormones are essential for initiating metamorphosis. ... 

Testosterone, the principal male sex steroid hormone, is synthesized in five steps from cholesterol, as shown below. In the last step, five isozymes catalyze the 17/3-hydroxysteroid dehydrogenase reactions that interconvert 4-androstenedione and testosterone. Defects in the synthesis or action of testosterone can impair the development of the male phenotype during embryogenesis and cause the disorders of human sexuality termed male pseudohermaphroditism. Specifically, mutations in isozyme 3 of the 17/3-hydroxysteroid dehydrogenase in the fetal testis impair the for-... 

Fjeld E, Haugen TO, Vollestad LA. 1998. Permanent impairment in the feeding behavior of grayling (Thymallus thymallus) exposed to methyhnercury during embryogenesis. Sci Total Envhon 213 247-254. 

Evidence for the involvement of a Cdc2/Cyc B complex in the mitotic stages of germ cell development comes from studies in Drosophila. Cyc B transcripts are abundant and uniformly distributed in the early Drosophila embryo (Whitfield et al., 1989, 1990 Lehner and O Farrell, 1990b). Maternally derived Cyc B transcripts are also concentrated at the posterior pole of the oocyte. Later, during embryogenesis, Cyc B tran-... 

Whitfield, W. G. F., Gonzalez, C., Sanchez-Herrero, E., and Glover, D. M. (1989). Transcripts of one of two Drosophila cyclin genes become localized in pole cells during embryogenesis. Nature 338 337-340. 

Bray, S. J., and Kafatos, F. C. (1991). Developmental function of elf-1 an essential transcription factor during embryogenesis in Drosophila. Genes Dev. 9 1672-1683. 

Joyner, A. L., and Martin, G. R. (1987). En-1 and En-2, two mouse genes with sequence homology to the Drosophila engrailed gene expression during embryogenesis. Genes Dev. 1 29-38. 

Robert, B Sassoon, D., Jacq, B Gehring, W and Buckingham, M. (1989). Hox-7, a mouse homeobox gene with a novel pattern of expression during embryogenesis. EMBO J. 8 91-100. 

Hauptman, O., D.M. Albert, M.C. Plowman, S.M. Hopfer, F.W. Sunderman, Jr. 1993. Ocular malformations of Xenopus laevis exposed to nickel during embryogenesis. Ann. Clin. Lab. Sci. 23 397-406. 

Boutelet-Bochan H, Huang Y, Juchau MR. 1997. Expression of CYP2EI during embryogenesis and fetogenesis in human cephalic tissues implications for the fetal alcohol syndrome. Biochem Biophys Res Commun 238 443-447. 

Moiiguchi T, Kita M, Tomono Y, Endolnagaki T, Omura M (1999) One type of chalcone synthase gene expressed during embryogenesis regulates the flavonoid accumulation in citrus ceU cultures. Plant Cell Physiol 40(6) 651-655... 

The vomeronasal system, also known as the accessory olfactory system, consists of chemoreceptors, organized into the VNO, the vomeronasal nerve, its terminal, the accessory olfactory bulb, and more central pathways. First described by Jacobson in 1811, the VNO has been studied intensely. We now know how stimuli reach it and what behaviors it mediates. The VNO occurs in amphibians, reptiles, and mammals. Among mammals, it is best developed in marsupials and monotremes. In birds it only appears during embryogenesis. The VNO and its function are best known for squamate reptiles, particularly snakes, and rodents and ungulates among the mammals. 

V2. Van den Eijnde, S. M., Luijsterburg, A. J., Boshart, L. De Zeeuw, C. I., van Dierendonck, J. H., Reutelingsperger, C. R, and Vermeij-Keers, C., In situ detection of apoptosis during embryogenesis with annexin V From whole mount to ultrastructure. Cytometry 29, 313-320 (1997). 

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