Impact of boron deficiency on Xenopus laevis: a summary of biological effects and potential biochemical roles.
The toxicity of boron has been understood for many years. However, limited data currently exist concerning the nutritional essentiality of B in chordates. Results from an ongoing research program evaluating the nutritional essentiality of B in the South African clawed frog, Xenopus laevis, found that X. laevis fed a low-B diet in a low-B culture media produced a substantially higher number of necrotic eggs and fertilized embryos than frogs fed a boron-sufficient diet. Markedly decreased embryo cell counts at mid-blastula transition and an increased frequency of abnormal gastrulation were also noted in embryos from adult frogs fed the B-deficient diet. By 96 h of development, none of the larvae collected from the B-deficient adults and maintained in low-boron culture media developed normally. Reproductive effects associated with B deficiency in female Xenopus included ovary atrophy, oocyte necrosis, and incomplete oocyte maturation. In males, a decrease in testis weight and sperm count was noted. These studies suggest that these adverse effects resulting from B deficiency could be found during gametogenesis, gamete maturation, embryonic development, and larval maturation. The studies also confirmed that B deficiency was capable of interrupting the X. laevis life cycle. Additional studies evaluating the role of B in the thyroid axis and the oocyte plasma membrane progesterone receptor provide the first line of direct evidence for a biochemical role of boron in X. laevis. Combined together, this research program provides firm evidence that B is nutritionally essential in X. laevis.
Fort
Douglas J
DJ
Fort Environmental Laboratories, Stillwater, OK 74074, USA.
Rogers
Robert L
RL
McLaughlin
Daniel W
DW
Sellers
Chris M
CM
Schlekat
Christian L
CL
D000818:Animals; D001895:Boron / Q000008:administration & dosage / Q000172:deficiency* / Q000494:pharmacology; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000196:embryology; D006128:Growth / Q000187:drug effects; D011980:Receptors, Progesterone / Q000378:metabolism; D012098:Reproduction / Q000187:drug effects; D013961:Thyroid Gland / Q000187:drug effects / Q000502:physiology; D014982:Xenopus laevis / Q000196:embryology / Q000254:growth & development* / Q000502:physiology*
D011980:Receptors, Progesterone; D001895:Boron