Xenopus laevis from frog

Hecker, M., J.P. Giesy, P.D. Jones, A.M. Jooste, J.A. Carr, K.R. Solomon, E.E. Smith, G. Van Der Rraak, R.J. Kendall, and L. Du Preez (2004). Plasma sex steroid concentrations and gonadal aromatase activities in African clawed frogs (Xenopus laevis) from South Africa. Environ. Toxicol. Chem., 23(8) 1996-2007. 

South African clawed frog, Xenopus laevis Fed worms from lead-contaminated soils ... 

Mature, oocyte positive, female Xenopus laevis are kept in (mesh) covered grey plastic tanks in tap water (depth 15-20 cm, 3-4 L per animal) at 16-19°C under constant light regime (12-h day/night cycle). The quality of the tap water should be tested at the beginning and care should be taken on the chlorine and heavy metal content. A simple way to eliminate excessive chlorine from the water is storage of the water for 24 h. Clay tubes in the tanks allow the frogs to cover themselves. The animals are fed a commercially available pellet diet twice a week, and occasionally they receive small pieces of bovine heart. The tanks have to be cleaned after each meal. 

As mature Xenopus laevis females carry 30,000 oocytes and a typical experiment consumes not more than 1,000 oocytes, it is not necessary to kill a frog for each experiment. Instead, pieces of the ovary are removed by laparotomy and the incision is sutured. The same animal can serve as a donor of fresh oocytes after a convalescence of 2-3 weeks, and 10-15 oocyte preparations can be made from each frog without affecting its health. Hence, not more than 20-30 animals, in most cases 10-15, are maintained at the same time. For details see also Protocol 1 in the Appendix. 

Oocytes from the South African clawed frog, Xenopus laevis, provide a reliable and powerful system for the transient heterologous expression of proteins. The use of this expression system has become very popular as oocytes have a high translational capacity and they are able to express multi-subunit proteins derived from exogenously introduced RNA or DNA. Furthermore, the expressed receptors frequently appear to be correctly assembled, post-translationally modified and oriented to the appropriate site. The relative scarcity of endogenous ion channels in the oocyte membrane makes it a versatile tool for the study of a range of heterologously expressed ion channel proteins. 

Numerous protocols describing the care and maintenance of Xenopus laevis frogs and the isolation of oocytes from their ovaries have been published (Cohnan, 1984 Goldin, 1992 Quick and Lester, 1994 Stiihmer and Parekh, 1995 Theodoulou and Miller, 1995). The following methods are based primarily on the procedures described by Yao and colleagues (2000). 

Xenopus laevis frogs can be purchased from the African Xenopus Facility, Knysna, Republic of South Africa, and are kept in a constant alternating 12-hour light (6 30 am to 6 30 pm)/dark cycle. 

The effect of various peptides and growth factors in small cell lung cancer cells has been reported by Bepler et al [121]. Four peptides isolated from completely different sources with structural similarities represent members of a new family of growth factors [121]. These peptides include 1) a 60 amino acid residue breast cancer- associated pS2 peptide isolated from human gastric juice and the culture media of the human breast cancer cell line MCF-7, 2) a 106 amino acid residue pancreatic spasmolytic polypeptide (PSP) isolated from porcine pancreas and 3) a 49 and 50 amino acid residue peptide predicted from a cyclic DNA isolated from the skin of frog, Xenopus laevis. 

Rowatt, A.J., J.J. DePowell and W.H. Powell. ARNT gene multiplicity in amphibians characterization of ARNT2 from the frog Xenopus laevis. J. Exp. Zool. Part B. Mol. Dev. Evol. 300 48-57, 2004. 

Several studies employing oocytes of the clawed frog, Xenopus laevis, for the in vitro translation of sodium channel encoding mRNAs (53-55) suggest that this experimental system may be particularly useful toward this end. The biophysical properties of sodium channels expressed in oocytes following injection of rat brain mRNA were similar to those of sodium channels in their native membrane environment, and were specifically inhibited by the sodium channel blockers tetrodotoxin and saxitoxin (i5.). Sodium channels encoded by mRNAs from rat skeletal muscle and eel electroplax have also been expressed in Xenopus oocytes (56-57). To date the expression of insect sodium channels in the Xenopus oocyte has not been reported, but the utility of this system for the translation and expression of insect acetylcholine receptor mRNA has recently been demonstrated (58). Successful application of this methodology to the expression of insect mRNAs encoding functional sodium channels offers a novel method to test some of the hypotheses for the molecular basis of the kdr mechanism. 

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