Expression analysis of some genes regulated by retinoic acid in controls and triadimefon-exposed embryos: is the amphibian Xenopus laevis a suitable model for gene-based comparative teratology?

Background: The use of nonmammal models in teratological studies is a matter of debate and seems to be justified if the embryotoxic mechanism involves conserved processes. Published data on mammals and Xenopus laevis suggest that azoles are teratogenic by altering the endogenous concentration of retinoic acid (RA). The expression of some genes (Shh, Ptch-1, Gsc, and Msx2) controlled by retinoic acid is downregulated in rat embryos exposed at the phylotypic stage to the triazole triadimefon (FON).

Early genetic control of craniofacial development is affected by the in vitro exposure of rat embryos to the fungicide triadimefon.

Background: Previous published experiments reported that in vitro exposure of postimplantation rat embryos to the triazole fungicide triadimefon (FON) resulted in specific abnormalities at the branchial apparatus and that the sensitive period is restricted to the first 24 hr of culture and is associated with the abnormal expression of TGF family genes (some of a large panel of genes regulated by retinoic acid (RA) and involved in branchial arch morphogenesis). The aim of this study is the determination of the sensitive window to FON-induced abnormalities during in vitro development and the evaluation of the expression of some genes controlled by RA and involved in early branchial arch morphogenesis (Gsc, Msx1, Msx2, Dlx1, Dlx2, Shh, Patched (the main Shh receptor)).

Methods: Rat embryos were exposed in vitro to the FON under condition known to be able to induce 100% of abnormal embryos (250  µM) at different stages and examined after 48 hr of culture.

Effects of TCDD on spermatogenesis related factor-2 (SRF-2): gene expression in Xenopus.

2,3,7,8-Tetra-chlorodibenzo-p-dioxin (TCDD) is one of the most toxic dioxins belonging to the wide family of Endocrine Disruptors (EDs), environmental chemicals that adversely interfere with endocrine processes and upset normal function of some target systems. It has been hypothesized that EDs enter cellular cytosol, bind to the Aryl Hydrocarbon Receptor (AhR) and form a heterodimer with the AhR nuclear translocator; this complex binds xenobiotic responsive elements that drive activation of the so-called "Ah gene battery". Spermatogenesis Related Factor-2 (SRF-2) is one of the most recently cloned genes involved in germ cell division and differentiation, whose expression seems to be affected by treatment with TCDD.

Developmental toxicity, uptake and distribution of sodium chromate assayed by frog embryo teratogenesis assay-Xenopus(FETAX).

The embryotoxicity and teratogenicity of Cr(VI) on the survival and morphology of the anuran Xenopus laevis have been assessed by frog embryo teratogenesis assay-Xenopus (FETAX). The lethal median (LC(50)) and teratogenic median (TC(50)) concentration values of Cr(VI) were 890 microM and 260 microM, respectively. The calculated teratogenic index (TI) value was 3.

Gene expression in nanotoxicology research: analysis by differential display in BALB3T3 fibroblasts exposed to cobalt particles and ions.

Broadly defined, nanoscale materials are substances in which at least one critical dimension is less than 100 nm. Nanoscale materials are employed in several industrial applications as well as in biology and medicine. Despite their wide use, very little research has been carried out on the potential toxicity of nanoparticles.

Molecular cloning and expression of alpha2,8-sialyltransferase (ST8Sia I, GD3 Synthase) in Xenopus.

GD3, a minor ganglioside in most normal tissues, is involved in important biological events and its expression could increase in pathological conditions. Organism integrity requires a tight balance between the anabolic and catabolic processes, thus it is important to control the intracellular expression of those "key" enzymes, which act at the "branching point" of ganglioside metabolism; one of these is the GD3-synthase (ST8Sia I). In this paper, we report the sequences of two ST8Sia I mRNAs found in Xenopus laevis and their genomic organization; the canonical form resulted constituted of 5 exons and 4 introns, while the "short" mRNA lacks of the exon 2.

Triadimefon causes branchial arch malformations in Xenopus laevis embryos.

Background, Aims And Scope: Triazole-derivatives are potent antifungal agents used as systemic agricultural fungicides and against fungal diseases in humans and domestic animals. They act by inhibiting the cytochrome P-450 conversion of lanosterol to ergosterol, thus resulting in faulty fungal cell wall synthesis. Some data have been published about the teratogenic activity of triazoles on rodent embryos: Hypoplasias, abnormal shape, agenesis of the branchial arches, for example, were reported as typical induced malformations.

Gene expression in Xenopus laevis embryos after Triadimefon exposure.

The triazole derivative Triadimefon (FON) is a systemic fungicide used to control powdery mildews, rusts, and other fungal pests. Some data have already been published about the teratogenic activity of this compound: craniofacial malformations were found in mouse, rat, and Xenopus laevis embryos exposed to FON. These alterations were correlated to defective branchial arch development possibly caused by abnormal neural crest cell (NCC) migration into the branchial mesenchyme.

Molecular markers for animal biotechnology: sea bass (Dicentrarchus labrax, L.) HMG-CoA reductase mRNA.

Modern technologies may improve fish production and quality and, at the same time, reduce environmental impact with benefits on the public perception of the industry. To be economically profitable, these modern technologies request an increase of rearing density that, however, could affect fish welfare. With the aim to search for molecular biomarkers to describe fish welfare, we have recently compared gene expression of sea bass farmed at different population densities by differential display obtaining six bands differentially expressed.

Platinum toxicity and gene expression in Xenopus embryos: analysis by FETAX and differential display.

Since the level of platinum in the environment is destined to increase, because of its use in vehicle catalytic converters, the toxicity of platinum needs further investigation. In this study, the frog embryo teratogenesis assay-Xenopus (FETAX) was used to compare the embryotoxicity and teratogenicity of two common platinum species, (NH4)2PtCl4 and (NH4)2PtCl6. The uptake rates of the two platinum species were studied, and also their effects on the expression of genes encoding metallothionein and heat-shock protein 70, which are known to be induced by several stress factors.

Selective pressure on the allantoicase gene during vertebrate evolution.

During vertebrate evolution, the uric acid degradation pathway has been modified and several enzymes have been lost. Consequently, the end product of purine catabolism varies from species to species. In the past few years, we have focused our attention on vertebrate allantoicase (an uricolytic pathway enzyme), whose activity is present in certain fish and amphibians only, but whose mRNA we detected also in mammals.

Arsenic toxicity and HSP70 expression in Xenopus laevis embryos.

The evaluation of the effect of trace metals on health can be difficult, because of their presence in the environment in various chemical forms. Exposure to arsenic compounds is an example of this complexity, as it can be present in the environment in inorganic and organic forms. The effects of arsenic in vertebrates are complicated by several variables, such as speciation of the element, the exposure route, and the susceptibility of the particular animal species.

Gene expression in Xenopus embryos after methylmercury exposure: a search for molecular biomarkers.

Mercury is a major issue in environmental health, as it can be biotransformed to methylmercury, accumulate into aquatic organisms, and enter the food chain. Therefore, we searched for molecular markers for methylmercury exposure comparing, by differential display, exposed Xenopus embryos to controls. We found two genes whose expression is completely inhibited by CH3HgCl, and we propose them as biomarkers of exposure.

Identification and molecular cloning of Xenopus laevis SP22, a protein associated with fertilization in mammals.

SP22 is a novel sperm protein that has been shown to be highly correlated with fertility in rats. SP22 homologues have been studied in mouse and man but a definitive role for the protein has not yet been established. Using a polyclonal IgG to recombinant rat SP22, we detected the presence of this protein in Xenopus laevis tissues.

Genomic organization and chromosome localization of the murine and human allantoicase gene.

Allantoicase is one of the enzymes involved in uricolysis. The enzymes of this catabolic pathway (i.e.

Property comparison of recombinant amphibian and mammalian allantoicases.

Allantoicase is an enzyme involved in uric acid degradation. Although it is commonly accepted that allantoicase is lost in mammals, birds and reptiles, we have recently identified its transcripts in mice and humans. The mouse mRNA seems capable of encoding a functional allantoicase, therefore we expressed the Xenopus and mouse allantoicases (MAlc and XAlc, respectively) in Escherichia coli and characterized the recombinant enzymes.

A comparative study of the toxicity of mercury dichloride and methylmercury, assayed by the Frog Embryo Teratogenesis Assay--Xenopus (FETAX).

The Frog Embryo Teratogenesis Assay-Xenopus (FETAX) is a powerful and flexible bioassay that makes use of the embryos of the anuran amphibian Xenopus laevis. The FETAX can detect xenobiotics that affect embryonic development, when mortality, teratogenicity and growth inhibition are used as endpoints. The FETAX was used to compare the embryotoxic and teratogenic potentials of two chemical species of mercury, inorganic mercury(II) chloride (HgCl2) and organic methylmercury chloride (MeHgCl).