Zn(2+)-induction of metallothionein in myotomal cell nuclei during somitogenesis of Xenopus laevis.

The localization of metallothionein in control and Zn-exposed embryos of Xenopus laevis was studied by whole-mount immunohistochemical staining. The embryos were grown according to the FETAX (Frog Embryo Teratogenesis Assay: Xenopus) protocol from N/F stage 8 to stage 47, with or without addition of ZnCl2 (300 microM) to the medium. At stages 27, 38, 42, 45 and 47, control and Zn-exposed embryos were fixed in buffered formalin, and whole mounts were stained by an immunoperoxidase technique, using monoclonal murine antibody to equine metallothionein.

Effects of teratogenic exposures to Zn2+, Cd2+, Ni2+, Co2+, and Cu2+ on metallothionein and metallothionein-mRNA contents of Xenopus embryos.

Xenopus laevis embryos were analyzed for metallothionein by silver-saturation assay and metallothionein-mRNA by reverse transcriptase/polymerase chain reaction following exposures to the following metal chlorides at levels that caused > 95% malformations and < 7% mortality: Zn2+ (300 microM); Cd2+ (18 microM); Ni2+ (56 microM); Co2+ (1,800 microM); and Cu2+ (5.6 microM). At the beginning of the exposure (stages 8), metallothionein-mRNA and metallothionein levels averaged 2.

Intraarticular carcinogenesis bioassays of CoCrMo and TiAlV alloys in rats.

Wear-debris powders of cobalt-chromium-molybdenum (CoCrMo) and titanium-aluminum-vanadium (TiAlV) alloys, which are widely used for orthopedic implants (eg, hip and knee prostheses), were tested for carcinogenic activity following intraarticular administration (20 mg/rat) to groups of 44 male Fischer-344 rats (Charles River Breeding Laboratories, North Wilmington, MA). Control groups received similar intraarticular injections of either a noncarcinogen (manganese powder, negative control rats) or a potent carcinogen (nickel subsulfide powder, positive control rats). The experimental groups of 8-12 rats were observed for 24 months after injection.

Lipovitellin 2 beta is the 31 kD Ni(2+)-binding protein (pNiXb) in Xenopus oocytes and embryos.

An Ni(2+)-binding protein (pNiXb, 31 kD) present in mature Xenopus laevis oocytes and in embryos from fertilization in N/F stage 42, was isolated and characterized. After oocytes or embryos were fractionated by PAGE, electroblotted onto nitrocellulose, and probed with 63Ni2+, pNiXb was detected by autoradiography. pNiXb, a yolk protein located in the embryonic gut, was purified from yolk platelets by ammonium sulfate precipitation, delipidation, gel filtration chromatography, and HPLC analysis.

Malformations persist after metamorphosis of Xenopus laevis tadpoles exposed to Ni2+, Co2+, or Cd2+ in FETAX assays.

This study was performed to determine whether malformations induced in Xenopus laevis embryos by exposures to divalent nickel, cobalt, or cadmium chlorides in FETAX assays persist after the tadpoles undergo metamorphosis to juvenile frogs. Embryos were exposed for four days to EC50 concentrations of Ni2+, Co2+, or Cd2+ under the standard conditions of FETAX assays; thereafter, the exposures were discontinued and the tadpoles were kept in aquaria through metamorphosis. Controls were treated similarly, without exposure to metals.