The blood (B), the tumor (T), and muscle (M) were excised from the mice and weighed and then counted in a well-type γ Counter (Xian Manufacture, China) for the evaluation of99mTc-annexin V biodistribution (energy peak at 140 keV and 10 s). The percentage of injected dose per gram of tissue (%ID/g) was calculated. The T/M and T/B ratio were calculated for correction of background radio-activity and decay of99mTc-HYNIC annexin V tracer. Histocytochemical study of apoptosis in tumor tissue Tumor apoptosis

was assessed by in situ end-labelling of DNA fragments (TdT-mediated Semaxanib dUTP-biotin nick end labelling, TUNEL) using a commercially available kit (Roche Applied Science). The fresh tumor tissue was fixed in 10% formaldehyde for 24 hours, dehydrated, paraffin-embedded and cut into 5- μm thick sections which were subsequently mounted on slides, rehydrated before stained with TUNEL for microscopic analysis. The mean Mizoribine in vivo number of apoptotic cells was counted in 10 randomly selected high-power fields. Statistical analyses Data were analyzed using the SPSS 13.0 software package. All variables were expressed as mean (M) and standard deviation (SD). All statistical comparisons of mean values were performed with the F test (one-way ANOVA). Linear correlation coefficients were calculated using a least squares linear regression analysis. A significance level of P < 0.05 was considered significant. Results Effect of different radiation doses on apoptosis

in EL4 cells The EL4 cells were irradiated in single-dose of 0, 2, 4 and 8 Gy groups, learn more respectively. After irradiation, the

cells were maintained in suspension culture for 24 hours, and then analyzed with FCM. As shown in Table 1, the EL4 cells had spontaneous apoptosis even when no radiation was given (0 Gy), and the number of apoptotic cells increased as radiation dose was escalated from 2 to 8 Gy. Table 1 The change of apoptotic rate in EL4 lymphoma cells evaluated by FCM after different doses of 4 MV X-ray radiation Dose(Gy) Apoptotic rate* (%) 0 3.13 ± 0.42 2 Bay 11-7085 6.80 ± 0.20 4 12.60 ± 0.56 8 16.17 ± 0.85 *Value is expressed as Mean ± SD. The apoptotic cell fractions (measured by FCM based on Annexin V-FITC and propidium iodide (PI) staining) of EL4 cells that received different single-irradiation doses (0 – 8 Gy) are shown in Figure 1. It shows that the number of necrotic (Q1) and apoptotic cells (Q2+Q4, Q4 represents the early phases of apoptosis) both significantly increased as the radiation increased from 0 to 8 Gy. Figure 1 Flow cytometry results for El4 lymphoma cells 24 hours after single-dose irradiation. Using Annexin V-FITC and PI stain, it showed that the ratio of apoptotic cells increased with the escalation of dose. The abscissa represents the number of AnnexinV positive cells; the ordinate represents the number of PI positive cells. Q1 represents the necrotic cell potion, Q2: apoptotic cells; Q3: normal cells; Q4: early phase apoptotic cells.