NRF iThemba LABS (Laboratory for Accelerated Based Sciences), Somerset West, South Africa and Department of Medical Imaging and Clinical Oncology, University of Stellenbosch , South Africa.
Int J Radiat Biol. 2014 Feb;90(2):149-58. doi: 10.3109/09553002.2014.860252.
To investigate both the formation of micronuclei (MN) and the induction and subsequent loss of phosphorylated histone H2AX foci (γH2AX foci) after in vitro exposure of human lymphocytes to either (60)Co γ-rays or p(66)+ Be(40) neutrons.
MN dose response (DR) curves were obtained by exposing isolated lymphocytes of 10 different donors to doses ranging from 0-4 Gy γ-rays or 0-2 Gy neutrons. Also, γH2AX foci DR curves were obtained following exposure to doses ranging from 0-0.5 Gy of either γ-rays or neutrons. Foci kinetics for lymphocytes for a single donor exposed to 0.5 Gy γ-rays or neutrons were studied up to 24 hours post-irradiation.
Micronuclei yields following neutron exposure were consistently higher compared to that from (60)Co γ-rays. All MN yields were over-dispersed compared to a Poisson distribution. Over-dispersion was higher after neutron irradiation for all doses > 0.1 Gy. Up to 4 hours post-irradiation lower yields of neutron-induced γH2AX foci were observed. Between 4 and 24 hours the numbers of foci from neutrons were consistently higher than that from γ-rays. The half-live of foci disappearance is only marginally longer for neutrons compared to that from γ-rays. Foci formations were more likely to be over-dispersed for neutron irradiations.
Although neutrons are more effective to induce MN, the absolute number of induced γH2AX foci are less at first compared to γ-rays. With time neutron-induced foci are more persistent. These findings are helpful for using γH2AX foci in biodosimetry and to understand the repair of neutron-induced cellular damage.
研究人淋巴细胞在离体条件下经（60）Co γ射线或 p（66）+ Be（40）中子照射后微核（MN）的形成以及磷酸化组蛋白 H2AX 焦点（γH2AX 焦点）的诱导和随后丢失。
用 10 位不同供体的分离淋巴细胞暴露于 0-4 Gy γ射线或 0-2 Gy 中子剂量，得到 MN 剂量反应（DR）曲线。另外，用 0-0.5 Gy γ射线或中子照射，得到 γH2AX 焦点 DR 曲线。对一位受 0.5 Gy γ射线或中子照射的供体淋巴细胞进行焦点动力学研究，直到照射后 24 小时。
与（60）Co γ射线相比，中子照射后的微核产率始终较高。所有 MN 产率均与泊松分布相比呈现过度分散。所有剂量>0.1 Gy 的中子照射后过度分散度更高。照射后 4 小时观察到的中子诱导γH2AX 焦点的产率较低。4-24 小时之间，来自中子的焦点数量始终高于来自γ射线的焦点数量。焦点消失的半衰期仅比γ射线略长。焦点形成更有可能在中子照射下过度分散。
尽管中子更有效地诱导 MN，但与γ射线相比，最初诱导的γH2AX 焦点的绝对数量较少。随着时间的推移，中子诱导的焦点更持久。这些发现有助于γH2AX 焦点在生物剂量学中的应用，并有助于理解中子诱导的细胞损伤的修复。
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