Use of Medaka in Toxicity Testing

Abstract

Small aquarium fishes are increasingly used as animal models, and one of these, Japanese Medaka (Oryzias latipes), is frequently utilized for toxicity testing. While these vertebrates have many similarities with their terrestrial counterparts, there are differences that must be considered if these organisms are to be used to their highest potential. Testing commonly may employ either the developing embryo or adults; both are easy to use and to work with. We present here three main protocols to illustrate the utility and breadth of toxicity testing possible using medaka fish. The first protocol assesses neurotoxicity in developing embryos. The second protocol describes the sexual genotyping of medaka to evaluate toxicant effects on sexual phenotype after treatment with endocrine disrupting chemicals. The third protocol assesses hepatotoxicity in adult fish after treatment with a model hepatotoxicant. The methods run the gamut from immunohistology through PCR to basic histological techniques.

Influence of sediment composition on PAH toxicity using zebrafish (Danio rerio) and Japanese medaka (Oryzias latipes) embryo-larval assays

“…Using a concentration set to 2.5 % peat, the degree of sensitivity of the medaka would be mainly due to its sensitivity to PAHs and to a longer exposure duration during the critical embryonic developmental period as well as due to the metabolic activity. Indeed, the embryonic phase in medaka at 26°C ranges from 10 to 11 days compared to 2 days in zebrafish (Kimmel et al 1995; Padilla et al 2009). In this context, our findings support the premise that medaka would constitute a better model for testing the toxicity of hydrophobic chemicals (such as PAHs) following a sediment contact test than zebrafish, although zebrafish assay has been demonstrated to be a valuable alternative when short-time exposures are targeted.…”

Expression profile of oestrogen receptors and oestrogen‐related receptors is organ specific and sex dependent: the Japanese medaka Oryzias latipes model

“…It is recognized that whole organ qPCR analysis is unable to demonstrate definite co‐expression of ERs and ERRs within the same cell, which is prerequisite to potential interaction. Recently, two histological devices: the embryo chip (Cheung et al ., ) and whole adult histoarray (Kong et al ., ; Park et al ., , ; Padilla et al ., ; Tompsett et al ., ), were developed to enable localization and quantification of multiple gene and protein expressions at the cellular level across multiple organs of the same fish simultaneously using in situ hybridization (ISH) and immunohistochemistry (IHC). Alternatively, qPCR analysis of cells removed from histologic sections using laser capture microdissection (LCM) can also be performed to localize gene expression at the tissue and cellular levels with sufficient resolution.…”

Early life co-exposures to a real-world PAH mixture and hypoxia result in later life and next generation consequences in medaka (Oryzias latipes)

“…Chorionated embryos were collected by siphoning tanks approximately 30 minutes after morning- and afternoon feedings. Embryos were cleaned and separated by rolling them on a moistened paper towel and then disinfected using a 15-minute immersion in 0.05% methylene blue (Sigma-Aldrich, St. Louis, MO, USA) followed by thorough rinsing in MilliQ water (Millipore, Billerica, MA, USA) (Padilla et al, 2009). Embryos were staged according to Iwamatsu (2004) and transferred to vials for testing.…”

“…Twenty fish (5 each from: control, 1% ERSE, H1, and H1+0.1% ERSE) with skeletal abnormalities were selected for bone staining with Alizarin Red S (Sigma-Aldrich) by modification of published methods (Baker et al, 2013; Padilla et al, 2009; Shanthanagouda et al, 2014). Briefly, fixed specimens were rinsed in 1X PBST overnight and internal organs removed through the ventral incison.…”