title: Marked depression of time interval between fertilization period and hatching period following exposure to low-dose X-rays in zebrafish.
abstract: In recent years there has been growing concern over the stimulating effects of very low-dose X-rays. Our laboratory had observed that zebrafish irradiated with low-dose X-rays tended to emerge earlier than sham controls. This observation led us to quantitatively examine the effects of low-dose X irradiation on a series of stages of development in the zebrafish. The embryos were fertilized simultaneously in vitro and incubated at an optimal temperature without crowding. Following exposure of the cleavage period (1.5 h after fertilization) to 0.025-Gy X-rays, the duration to hatching was slightly shorter than that of the sham controls. This tendency was increased when the X-ray exposure occurred during the blastula period (3.5 h). In these embryos, the duration to hatching decreased significantly by an average of 6 h sooner than for sham controls. No differences in duration to hatching were seen when irradiation was given during either the zygote period (45 min) or the segmentation period (12 h). On the contrary, upon exposure to 0.5-Gy X-rays during the blastula period, the duration to hatching increased significantly relative to that of sham controls. These results suggest that the radiation-induced early hatching effect is observed for low doses of X-rays.
authors.affiliation: Department of Radiological Sciences, International University of Health and Welfare, Kitakanemaru 2600-1, Ohtawara-shi, Tochigi-ken 324-8501, Japan. ymiyachi@iuhw.ac.jp
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Miyachi
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kanao
authors.forename: Takehito
authors.initials: T
authors.lastname: Okamoto
mesh_terms: D000818:Animals; D004307:Dose-Response Relationship, Radiation; D047108:Embryonic Development; D005260:Female; D005306:Fertilization; D008297:Male; D010063:Ovum / Q000254:growth & development* / Q000528:radiation effects; D013997:Time Factors; D014965:X-Rays / Q000009:adverse effects; D015027:Zebrafish / Q000196:embryology*