Frog development

Metamorphosis differs in the many different amphibian species. In frog development, the eggs hatch and give rise to tadpoles, small aquatic larvae that have exter-... 

Strychnicine. This alkaloid, isolated from nux-vomica leaves grown in. lava, forms needles, m.p. 240° dec.), and is characterised by the following colour reaction. When sodium hydroxide solution is added drop by drop to a solution of a salt of the alkaloid in water, the precipitate formed dissolves on addition of more alkali, forming an orange-coloured liquid which develops a violet colour on addition of hydrochloric acid. Strychnicine is scarcely poisonous, but is said to produce tetanus in frogs. 

The first clue to a role for Wnt/(3-catenin-dependent signaling in vertebrate development came from overexpression studies in the classical embryonic system, the frog Xenopus loevis. When Wntl is ectopically expressed in cells that would normally contribute to the ventral embryo (i.e. the future belly), they instead adopt... 

Coady, K.K., Murphy, M.B., and Villeneuve, D.L. et al. (2004). Effects of atrazine on metamorphosis, growth, and gonadal development in the green frog (Rana clamitans). Journal of Toxicology and Environmental Health, Part A Current Issues 67, 941-957. 

Until the recent development of appropriate HPLC techniques capable of detecting pmol amounts (see Flentge et al. 1997) ACh could only be measured chemically by relatively lengthy and expensive procedures (e.g. gas chromotography), which were not always very sensitive, or by bioassays. Although the latter, using muscle preparations that responded to ACh, such as the dorsal muscle of the leech, the rectus abdominus of the frog or certain clam hearts, were reasonably sensitive they were tiresome and not easily mastered. Thus studies on the release and turnover of ACh have not been as easy as for the monoamines. 

Hansen A., Reiss J.O., Gentry C.L. and Burd G. (1998). Ultrastructure of the olfactory organ in the clawed frog, Xenopus laevis during larval development and metamorphosis. J Comp Neurol 398, 273-288. 

Taniguchi K., Toshima Y. and Saito T. (1996). Development of the olfactory epithelium and vomeronasal organ in the Japanese reddish frog. Rana japonica. J Vet Med Sci 58, 7-15. 

Jefferson salamander, Ambystoma jeffersonianum embryos (4-days postfertilization) exposed for 21 days to 130-800 pg Pb/L at pH 4.5 and 5.5 Green frog, Rana clamitans tadpoles At low pH, lead aids development and protects against arrested growth in a dose-dependent manner normal hatch and development at pH 5.5 and 800 pg Pb/L 47... 

Wood frog, Rana sylvatica 30-600 Tadpoles exposed through metamorphosis developed normally 18... 

Dial, N.A. and C.A. Bauer. 1984. Teratogenic and lethal effects of paraquat on developing frog embryos (Rana pipiens). Bull. Environ. Contam. Toxicol. 33 592-597. 

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