Effect of gamma radiation on the growth, survival, hematology and histological parameters of rainbow trout (Oncorhynchus mykiss) larvae

Biological effects of ionizing radiation on aquatic biota - A critical review

Ionizing radiation from radionuclides impacts marine aquatic biota and the scope of investigation must be wider than just invertebrates. We intend to detail and illustrate numerous biological effects that occur in both aquatic vertebrates and invertebrates, at various dose rates from all three kinds of ionizing radiation. The characteristics of radiation sources and dosages that would most effectively generate the intended effects in the irradiated organism were assessed once the biological differentiation between vertebrates and invertebrates was determined through multiple lines of evidence. We contend that invertebrates are still more radiosensitive than vertebrates, due to their small genome size, rapid reproduction rates and lifestyle, which help them to compensate for the effects of radiation induced declines in fecundity, life span and individual health. We also identified various research gaps in this field and suggest future directions to be investigated to remedy the lack of data available in this area.

Effects of Low-Dose Gamma-Ray Radiation on Apoptosis and Development of Zebrafish Embryo Brain

To investigate the effects of low-dose γ irradiation on apoptosis and development of the brain in zebrafish embryos, cumulative 15 mGy doses of γ rays from a 137Cs source were used to irradiate zebrafish embryos at 2 h post-fertilization (hpf) for 120 h. Apoptosis of the brain, brain morphological development, cell submicroscopic structure and mRNA expression were analyzed, respectively. Results indicate that after 15 mGy exposure, the apoptosis of zebrafish brain increased, vacuoles appeared in brain tissue, some organelles were damaged and vacuoles appeared locally in brain cells. The mRNA expression level of axin2 was significantly upregulated, and those of frizzled, β-catenin, camk2, TCF/ LEF and bcl9 were significantly downregulated in brain tissue. These genes are involved in the Wnt signaling pathway. The findings of this work suggest that low-dose radiation may influence the apoptosis and development of the brain in the zebrafish embryo by inhibiting the Wnt signaling pathway.

Identification of Cofilin-1 and Destrin as Potential Early-warning Biomarkers for Gamma Radiation in Mouse Liver Tissues

Gamma radiation causes cell injury and leads to an increased risk of cancer, so it is of practical significance to identify biomarkers for gamma radiation. We used proteomic analysis to identify differentially expressed proteins in liver tissues of C57BL/6J mice treated with gamma radiation from Cs for 360 d. We confirmed obvious pathological changes in mouse liver tissues after irradiation. Compared with the control group, 74 proteins showed a fold change of ≥1.5 in the irradiated groups. We selected 24 proteins for bioinformatics analysis and peptide mass fingerprinting and found that 20 of the identified proteins were meaningful. These proteins were associated with tumorigenesis, tumor suppression, catalysis, cell apoptosis, cytoskeleton, metabolism, gene transcription, T-cell response, and other pathways. We confirmed that both cofilin-1 and destrin were up regulated in the irradiated groups by western blot and real-time polymerase chain reaction. Our findings indicate that cofilin-1 and destrin are sensitive to gamma radiation and may be potential biomarkers for gamma radiation. Whether these proteins are involved in radiation-induced tumorigenesis requires further investigation.

Up-regulation of calreticulin in mouse liver tissues after long-term irradiation with low-dose-rate gamma rays

The biological effects of low-dose or low-dose-rate ionizing radiation on normal tissues has attracted attention. Based on previous research, we observed the morphology of liver tissues of C57BL/6J mice that received <50, 50–500, and 500–1000 μGy/h of ¹³⁷Cs radiation for 180 d. We found that the pathological changes in liver tissues were more obvious as the irradiation dose rates increased. Additionally, differential protein expression in liver tissues was analyzed using a proteomics approach. Compared with the matched group in the 2D gel analysis of the irradiated groups, 69 proteins had ≥ 1.5-fold changes in expression. Twenty-three proteins were selected based on ≥2.5-fold change in expression, and 22 of them were meaningful for bioinformatics and protein fingerprinting analysis. These molecules were relevant to cytoskeleton processes, cell metabolism, biological defense, mitochondrial damage, detoxification and tumorigenesis. The results from real-time PCR and western blot (WB) analyses showed that calreticulin (CRT) was up-regulated in the irradiated groups, which indicates that CRT may be relevant to stress reactions when mouse livers are exposed to low-dose irradiation and that low-dose-rate ionizing radiation may pose a cancer risk. The CRT protein can be a potential candidate for low-dose or low-dose-rate ionizing radiation early-warning biomarkers. However, the underlying mechanism requires further investigation.

Toxic effects of 56Fe ion radiation on the zebrafish (Danio rerio) embryonic development

All living organisms and ecosystems are permanently exposed to ionizing radiation. Of all the types of ionizing radiation, heavy ions such as ⁵⁶Fe have the potential to cause the most severe biological effects. We therefore examined the effects and potential mechanisms of iron ion irradiation on the induction of developmental toxicity and apoptosis in zebrafish embryos. Zebrafish embryos at 4h post-fertilization (hpf) were divided into five groups: a control group; and four groups irradiated with 0.5, 1, 2, and 4Gy radiation, respectively. Mortality and teratogenesis were significantly increased, and spontaneous movement, heart rate, and swimming distance were decreased in the irradiated groups, accompanied by increased apoptosis. mRNA levels of genes involved in the apoptotic pathway, including p53, bax, bcl-2, and caspase-3, were significantly affected by radiation exposure. Moreover, protein expression levels of P53 and Bcl-2 changed in accordance with the corresponding mRNA expression levels. In addition, we detected the protein expression levels of γ-H2AX, which is a biomarker for radiation-induced DNA double-strand breaks, and found that γ-H2AX protein levels were significantly increased in the irradiated groups. Overall, the results of this study improve our understanding of the mechanisms of iron ion radiation-induced developmental toxicity and apoptosis, potentially involving the induction of DNA damage and mitochondrial dysfunction. The findings of this study may aid future impact assessment of environmental radioactivity in fish.