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Reliable human data on the effects of prenatal exposure to ionizing radiation are largely based on high-dose exposures. Exposure to low doses may produce effects that are not easily observable at birth, and may persist over the course of the offspring's postnatal life. This is important when considering fetal programing, a phenomenon characterized by changes in offspring phenotype due to a stress experienced in utero. In this review, we briefly summarize the known effects of both high- and low-dose exposure to ionizing radiation during pregnancy in humans. There is a major consensus that the atomic bomb survivors' data shows increased incidence of microcephaly and reductions in IQ of A-bomb survivors, whereas, with diagnostic radiography in utero there is no conclusive evidence of increased cancer risk. Due to the relatively limited data (particularly for low-dose exposures) in humans, animal models have emerged as an important tool to study prenatal effects of radiation. These animal models enable researchers to manipulate various experimental parameters and make it possible to analyze a wider variety of end points. In this review, we discuss the major findings from studies using mouse and rat models to examine prenatal ionizing radiation effects in postnatal development of the offspring. In addition, we broadly categorize trends across studies within three major stages of development: pre-implantation, organogenesis and fetal development. Overall, long-term effects of prenatal radiation exposure (including the possible role on the developmental programing of disease) are important factors to consider when assessing radiation risk, since these effects are of relevance even in the low-dose range.

A reference staging series of 18 morphological stages of laboratory reared lake whitefish Coregonus clupeaformis is provided. The developmental processes of blastulation, gastrulation, neurulation as well as development of the eye, circulatory system, chromatophores and mouth are included and accompanied by detailed descriptions and live imaging. Quantitative measurements of embryo size and mass were taken at each developmental stage. Eggs were 3·19 ± 0·16 mm (mean ± s.d.) in diameter at fertilization and embryos reached a total length (LT ) of 14·25 ± 0·41 mm at hatch. Separated yolk and embryo dry mass were 0·25 ± 0·08 mg and 1·39 ± 0·17 mg, respectively, at hatch. The effects of two common preservatives (formalin and ethanol) were examined throughout development and post hatch. Embryo LT significantly decreased following fixation at all points in development. A correction factor to estimate live LT from corresponding fixed LT was determined as live LT = (fixed LT )(1·025) . Eye diameter and yolk area measurements significantly increased in fixed compared with live embryos up to 85-90% development for both measurements. The described developmental stages can be generalized to teleost species, and is particularly relevant for the study of coregonid development due to additionally shared developmental characteristics. The results of this study and staging series are therefore applicable across various research streams encompassing numerous species that require accurate staging of embryos and descriptions of morphological development.

Chemicals used in the prevention of corrosion and biofouling may be released into the environment via industrial cooling water discharges. The authors assessed the impacts of 2 commonly used chemicals, morpholine and sodium hypochlorite, on development in lake whitefish (Coregonus clupeaformis). Embryos were exposed chronically, beginning at fertilization or at the eyed stage. Acute 96-h exposures were also examined at 4 development stages. Chronic morpholine resulted in median lethal concentrations (LC50s) of 219 ± 54 mg/L when exposure began at fertilization and 674 ± 12 mg/L when exposure began at the eyed stage, suggesting that embryos are more sensitive earlier in development. Chronic morpholine exposure advanced hatching by up to 30%, and the early hatching embryos were up to 10% smaller in body length. A decrease in yolk conversion efficiency was also observed in embryos exposed to chronic morpholine concentrations of 1000 mg/L. The majority of effects from morpholine exposure manifested near hatch, possibly reflecting changes in chorion permeability at the end of embryonic development. Sodium hypochlorite only impacted survival with chronic exposure from fertilization, where the total residual chlorine LC50 was 0.52 ± 0.11 mg/L. Acute exposures to both chemicals had minimal effects up to the highest tested concentrations. Overall, the results suggest that the risk during development from exposure to morpholine and sodium hypochlorite is low under normal operating conditions. Environ Toxicol Chem 2017;36:1955-1965. © 2016 SETAC.