Objective To investigate the dose-response of micronuclei (MN) frequency in the lymphocytes irradiated with or without combination of α-particles and γ-rays. Methods Human lymphoblast cells HMy2.CIR were irradiated with 0 - 1 Gy of α-particles,0 - 5 Gy of γ-rays,and 0.025 -0.5 Gy of α-particles followed by different doses of γ-rays,respectively.The micronuclei (MN) in the irradiated cells were measured with the cytokinesis block technique,and the dose-responses of MN were established under different irradiation conditions.Results For γ-ray irradiation,the dose-response of MN was well-fit by the linear-quadratic model with an equation Y =c + αD + βD2.For α-particle irradiation,the MN induction increased linearly with the dose less than 0.250 Gy. But when the dose of α-particles increased continually,the dose-response curve bended and could be well fit with the BaD model Y =c + αD + σ[ 1 - exp( - δD) ] exp( - βD) where radiation-induced bystander effect (RIBE) was indicated.For the combined exposure,the dose-response of MN was similar to that of γ-irradiation when the dose of α-particles was lower than 0.1 Gy,but it was similar to that of α-irradiation when the dose of α-particles was higher.When the dose of α-particles was 0.2 and 0.5 Gy,MN induced by the mixed radiation were significantly higher than the sum of corresponding irradiation alone ( t =5.22 - 11.86,P ＜ 0.05 ).Conclusions The radiation damage of α-particles differs from that of γ-rays,where RIBE may be involved.The combination irradiation of α-particles and γ-rays has a synergistic effect on radiation damage of lymphoblast cells.

Objective To investigate the effects of long-term low-dose radiation (LDR) of γ-rays on the proliferation and radiosensitivity of human lymphoblast cells HMy2.CIR (HMy) and to elucidate the underlying mechanism.Methods HMy cells were divided into control group and long-term LDR group.For the long-term LDR treatment,HMy cells were fractionally exposed to a low dose of γ-rays,which could enhance cell proliferation,3 times per week for 4 weeks.After the long-term LDR exposure,part of the control and long-term LDR exposed cells were further irradiated with a challenging dose (2 Gy) of γ-rays.Then cell proliferation and radiosensitivity were assayed by CCK-8 kit,cell apoptosis,and γ-H2AX formation was measured by flow cytometry.Gene expressions of cyclinD1,PCNA,bcl-2 and bax were detected by RT-PCR.Results The long-term LDR significantly increased cell proliferation (t =9.607,P ＜ 0.01) accompanied with up-regulation of cell cycle regulation gene cyclinD1 (t =6.869,P ＜ 0.01),proliferation regulation gene PCNA (proliferating cell nuclear antigen) (t =9.229,P ＜ 0.01) and bcl-2 gene (t =2.662,P ＜ 0.05),but decreased the expression of pro-apoptotic gene bax (t =19.908,P ＜0.01) in HMy cells.Compared to untreated cells,the long-term LDR decreased cell radiosensitivity (t =8.896,P ＜ 0.01),including apoptosis induction (t =4.762,P ＜ 0.01) and γ-H2AX formation (t =10.264,P＜0.01).Conclusions The long-term LDR promoted cell proliferation by up-regulating cell cycle related genes,while it reduced the radiosensitivity of HMy cells with acquisition of apoptotic resistance.

Objective To analyze the percentage and functional changes of natural killer T (NKT) cells in peripheral blood and bone marrow of severe aplastic anemia (SAA) children before immunosuppressive therapy (IST) comparing to that of healthy children.Methods Ten children with severe aplastic anemia were included in the study and ten healthy children at the same age were selected as the control group. By lfow cytometry, the percentage of CD3+CD1d tetramer+ NKT cell in peripheral blood and bone marrow were detected from March 2014 to December 2014 in our hospital. Immune magnetic bead separation was used to isolate and purify iNKT cells .The puriifed iNKT cells were cultured in the OCH(50 ng/ml,100 ng/ml or 200 ng/ml)+rhIL-2+rhG-CSF culture systems. The ampliifcation of iNKT cells after cultured in different systems were calculated. Elispot method was used to analyze the spotting form cells (SFCs) of IFN-γ or IL-4 expressed by activated iNKT cells.Results The percentage of CD3+CD1d tetramer+ NKT cells in peripheral blood of SAA group(0.72±0.03)% was signiifcantly lower than that of the control group(0.92±0.02)%(P=0.000). The percentage of CD3+CD1d tetramer+ NKT cells in bone marrow of SAA group(0.82±0.02)% was signiifcantly lower than that of the control group(1.05±0.05)%(P=0.000).In vitro iNKT cell ampliif-cation ability of bone marrow in SAA group was signiifcantly lower than the control group, and in medium concentration(50±6) and high concentration OCH group(52±6), the ampliifcation ability was higher than that in low concentration OCH group(30±5) (P<0.05). The secretion of IFN-γ in the iNKT cells of SAA bone marrow was signiifcantly lower in medium concentration(33±3) and high concentration(35±3)OCH group than that of the low concentration(50±3)OCH group(P<0.01). The secretion of IL-4 in the iNKT cells of SAA bone marrow was signiifcantly higher in medium concentration(50±3)and high concentration(75±3) OCH group than that of the low concentration(33±3) OCH group(P<0.01).Conclusions The quantity and function of NKT cells from children with SAA are lower than that of the healthy children.In vitro, they had better ampliifcation ability and could improve IL-4/IFN-γ imbalance in medium concentration and high concentration OCH group than in low concentration OCH group.

10.3969/j.issn.1000-3606.2013.06.007