ABSTRACT
Ion Channel β Subunits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 14.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
Xenopus laevis, the South African clawed frog (Figure 14.1A), is named for its country of origin and distinctive long claws on the three inside toes of either hind foot, which it uses to tear apart larger food items.1 Although the primarily aquatic existence of X. laevis is characteristic of true frogs, it belongs to neither the Rana (true frogs) nor Bufo (toads) families and is classified in the family Pipidae. X. laevis has no ears or eyelids and, unlike Rana frogs, lacks a tongue suited for the trapping of prey. Though endogenous to southern African countries, X. laevis can now be found widely distributed in many parts of the world. X. laevis was used for human pregnancy tests in the 1940s, as chorionic gonadotrophin present in the urine of pregnant women was shown to induce the laying of eggs when injected into adult female frogs.
