Zebrafish embryo

Toxicity analyses were performed by the individual exposure of zebrafish embryos to the different PBDEs commercial mixtures degradation samples from 4 to 48 hours post-fertilization (hpf), including negative controls and controls of solvent in the test. Additionally, two independent experiments were performed on undiluted samples and a last experiment was performed on a dilution series of 50%, 5% and 0.5% of the original samples. The embryos were observed after 24 and 48 hpf, and categorized as dead or alive. 

Fig. 10 Percentage of mortality of zebrafish embryos after 48 h of exposure to PBDE commercial mixtures samples at different dilutions (100%, 50%, and 5%)...

Fig. 11 Percentage of mortality of zebrafish embryos after 48 hpf to PBDE samples (before and after 12 h and 7 days of treatment with fungus). All the samples were diluted at 5%...

Figure 10. Median zebra fish embryo hatching rates as a function of calculated Cu2+ concentrations. Reprinted with permission from [228] Fraser, J. K. et al. (2000). Formation of copper complexes in landfill leachate and their toxicity to zebrafish embryos , Environ. Toxic. Chem., 19, 1397-1402. Copyright SETAC, Pensacola, Florida, USA...

Table 3.2 LC50 values of fullerenes in zebrafish embryos (Beuerle, 2007)...

Fig. 3.9 Inhibition of normal apoptosis by 1-tris and 6 in zebrafish embryos, (a) 10 pM 1-tris caused decreased apoptosis in the hg at 2dpf (B) and op at 4 dpf (D). (b) 250pM decreased apoptosis in the hg, op and rt at 2 dpf (B) and nm at 5 dpf (D) (Reprinted from Beuerle, 2007. With friendly permission of Taylor Francis, http //www.informaworld.com)...

Figure 3.10 shows the protection of zebrafish embryo hair cells by various water-soluble fullerene derivatives. The data for both gentamicin- and cisplatinum-induced apoptotic cell death are summarized in Table 3.3. Comparing the data for... 

Ulrike, L., Gabriele, V., and Thomas, W., Zebrafish embryos express an orthologue of HERG and are sensitive toward a rank of QT-prolonging drugs inducing severe arrhythmia, Toxicol. Appl. Phamacol., 193, 370-382, 2003. 

Gering M and Patient R (2005). Hedgehog signaling is required for adult blood stem cell formation in zebrafish embryos. Developmental Cell 8 389-400. 

One of the pollutants known to interfere with cardiovascular development is 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD). TCDD is a persistent, bioaccumulative environmental contaminant, as well as a potent developmental toxicant and human carcinogen [30]. Piscine, avian, and mammalian cardiovascular systems are sensitive to TCDD toxicity, with effects including cardiac enlargement, edema, and several dysfunctions. In zebrafish embryos, these effects include areduction in cardiomyocyte number at 48 hpf, decreased heart size, altered vascular remodeling, pericardial edema, and decreased ventricular contraction culminating in ventricular standstill [31-34]. 

The dissociation between cardiotoxicity and carcinogenesis can be visuahzed in zebrafish embryos exposed to known dioxin like carcinogens, like benzo[a]p3rene, or to noncarcinogenic AhR ligands, as p-naphthoflavone (Fig. 5) [41, 43]. The conclusion that cardiotoxic effects in zebrafish (and presumably, other vertebrates ) embryos occur by exposition to AhR hgands so-far considered... 

Fig. 5 Typical deformations detected in 96 hpf zebrafish embryos exposed at the indicated concentrations of the carcinogenic polycyclic aromatic hydrocarbons Benzo[a]Pyrene (b) and Benazo [k]Fluoranthene (c), or to the reportedly nontoxic AhR-ligand (3-naphthofiavone (d). A nonexposed, normal specimen is shown in (a). Arrows indicate (a) pericardial edema, (b) malformation of the lower jaw, (c) malformation of the tail, (tf) color of the yolk, and (e) coagulation...

Fig. 7 Transcriptome effects of T3 administration on the developing zebrafish embryo, (a) Heatmap of microarray results from 652 probes showing significant differences between T3-treated and control samples. Fold induction values (in log scale) are represented by different shades of color (scale shown in the far-right bar.), (b) Distribution of overrepresented (red), underrepresented (blue), and unchanged/undetected (ivory) transcripts in T3-treated embryos belonging to the functional categories ossification, visual processes, and oxygen transport. The significance of the observed variations (p values) was calculated by the hypergeometric distribution with the Bonferroni correction...

Figure 7 shows the effect of ectopic administration of T3 to the developing zebrafish embryo. At nontoxic concentration (50 nM), only a moderate fraction (less than 5%) of the zebrafish transcriptome shows significant changes. Ossification, visual processes, and the hematopoietic system were the physiological processes most affected by the treatment, in a pattern consistent with an advancement of the development in these particular functions (Fig. 7b). Genes involved in these three processes are known targets for TDCs during metamorphosis in amphibians, teleost fishes, and lampreys [54—60], and constitute molecular counterparts of different endpoints used to test for TDC in amphibians [56, 58]. Therefore, they are excellent candidates for markers of thyroid disruptors in zebrafish at early developmental stages. Chapter 14 provides a more in-deep description of the developmental effects of thyroid disruption in zebrafish embryos.

The gastrointestinal system of zebrafish presents clear differences from the human system. The zebrafish does not possess a stomach, the intestine is continuous with the pharynx through a short esophagus, and no sphincters are present [61]. However, zebrafish have most of the cell types observed in the small intestine -absorptive, endocrine, goblet, and interstitial cells of Cajal, although Paneth cells are absent. Gut contractions are under the control of the enteric nervous systems, which respond to different pharmaceuticals in similar way as the mammalian counterpart. For example, zebrafish embryos can be used as predictor of emetic response to pharmaceuticals, one of the most commonly reported clinical adverse effects to be considered in the development of new dmgs [61]. 

Fig. 9 Effects of Ti02 NP in the developing zebrafish embryos, (a) Reduction of embryo length asterisks indicate significant (P < 0.05) deviations from the control value following ANOVA and Dunnet Post hoc tests, (b) Oxidative stress, as indicated by elevated activity of SA-(3-galactosidase in notocorda and gut (arrow), (c) Alteration of the otoliths to become optically denser than in control (arrow). The occurrence of denser otoliths was 10 and 95% out of 60 analyzed larvae in control and NM exposures. NP nanoparticle-treated animals...

The acute toxicity and oxidative effects of nano-scale Ti02 depend on the size of the nanoparticle (bulk Ti02 is positively nontoxic) and increase notably through illumination, as this leads to the formation of hydroxyl radicals [74], further indicating oxidative stress as a major candidate for the mechanism of action of NP toxicity. However, a recent microarray analysis of the transcriptome of zebrafish embryos treated with Ti02 NP showed no major increase of transcripts related to oxidative stress. Instead, significant effects were observed on expression of genes involved in circadian rhythm, kinase activity, vesicular transport, and immune response [75]. 

Morphological and biochemical analyses of zebrafish embryos exposed to Ti02 NP show some unexpected effects. Exposed animals exhibited a significant reduction in size (Fig. 9a) and markers of oxidative stress, as revealed by the increase in the SA-p-... 

Sylvain NJ, Brewster DL, Ali DW (2010) Zebrafish embryos exposed to alcohol undergo abnormal development of motor neurons and muscle fibers. Neurotoxicol Teratol 32 472-480... 

Chen YH, Huang YH, Wen CC, Wang YH, Chen WL, Chen LC, Tsay HJ (2008) Movement disorder and neuromuscular change in zebrafish embryos after exposure to caffeine. Neurotoxicol Teratol 30 440 47... 

Stehr CM, Linbo TL, Incardona JP, Scholz NL (2006) The developmental neurotoxicity of fipronil notochord degeneration and locomotor defects in zebrafish embryos and larvae. Toxicol Sci 92 270-278... 

Jovanovic B, Ji TM, Palic D (2011) Gene expression of zebrafish embryos exposed to titanium dioxide nanoparticles and hydroxylated fullerenes. Ecotoxicol Environ Saf 74 1518-1525... 

Strahle U, Schloz S, Geisler R, Greiner P, Hollert H, Rastegar S et al (2011) Zebrafish embryos as an alternative to animal experiments - a commentary on the definition of the onset of protected life stages in animal welfare regulations. Reprod Toxicol. doi 10.1016/j.reprotox.2011.06.121... 

Camacho F, Cilio M, Guo Y et al 2001 Human casein kinase Idelta phosphorylation of human circadian clock proteins period 1 and 2. FEES Lett 489 159-165 Delaunay F, Thisse C, Marchand O, Laudet V, Thisse B 2000 An inherited functional circadian clock in zebrafish embryos. Science 289 297-300 Dunlap J 1998 Circadian rhythms. An end in the beginning. Science 280 1548-1549 Ebisawa T, Uchiyama M, Kajimura N et al 2001 Association of structural polymorphisms in the human period3 gene with delayed sleep phase syndrome. EMBO Rep 2 342-346 Edery I, Zwiebel LJ, Dembinska ME, Rosbash M 1994 Temporal phosphorylation of the Drosophila period protein. Proc Natl Acad Sci USA 91 2260-2264 Ishida N, Kaneko M, AUada R 1999 Biological clocks. Proc Natl Acad Sci USA 96 8819-8820... 

Scholz S, Fischer S, Giindel U et al (2008) The zebrafish embryo model in environmental risk assessment—applications beyond acute toxicity testing. Environ Sci Pollut Res Int 15(5) 394 04... 

Finally, chemicals were evaluated for adverse effects in a zebrafish embryo development test (ZFE platform) (35). The ZFE platform evaluated embryos at 6 days post-fertilization (d.p.f) and assigned a terata score to each fish based on the incidence of observed malformations. Terata scores were provisionally categorized by... 

Zebrafish embryo assay results were compared to the ToxCast in vitro assay features from the predictive model of developmental toxicity (50). A majority of the features were significant between the zebrafish data and predictive models, despite the fact that the zebrafish assay did not correlate with global developmental toxicity defined by species-specific ToxRefDB data. The top 15 chemicals predicted to be developmental toxicants and bottom 15 chemicals predicted not to be developmental toxicants varied in their endpoint responses and logP values. Padilla et al. (35) noted that chemical-physical characteristics could limit the amount of chemical seen by the embryo due to poor solubility or poor uptake. This may be the reason that a majority of the bottom 15 chemicals with no zebrafish embryo activity had logP values less than 1.0. The bottom 15 chemicals with zebrafish embryo activity could almost exclusively be characterized by the negative predictors of the species-specific developmental toxicity models, which may be indicating that these predictors have differing roles between mammalian and zebrafish development. 

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