Objective:To conduct a comparative analysis of the oxygen depletion and oxygen effect of FLASH irradiation and conventional irradiation by direct measurement of oxygen content.Methods:The oxygen content in different tissues and organs of mice was measured using a phosphorescent probe. A subcutaneous xenograft tumor model in mice was established, to receive electron-beam irradiation at different doses and dose rates. The oxygen depletion of tumor and normal tissue was analyzed, and tumor control was evaluated. The oxygen depletion of conventional irradiation and FLASH irradiation was further analyzed using an in vitro model. The survival fraction (SF) of normal cells after conventional irradiation and FLASH irradiation was calculated using colony formation assay under different partial pressures of oxygen, and the data were fitted to the oxygen enhancement ratio (OER) curve. Results:The mean oxygen content of subcutaneous xenograft tumor in mice was 1.28%, suggesting hypoxia. The mean oxygen content of normal tissue ranged from 3.51% to 6.53%, suggesting physioxia. In animal experiments, oxygen depletion was not observed during conventional irradiation. High-dose-rate (20 Gy/s) and ultra-high-dose-rate (FLASH, 40 Gy/s) irradiation produced oxygen depletion. During FLASH irradiation, with the increase of oxygen content, the oxygen depletion was 0.1-0.2 mm Hg/Gy for tumor tissue and 0.19-0.21 mm Hg/Gy for skin tissue, which tended to stabilize. FLASH irradiation maintained equivalent tumor control compared to conventional irradiation. The tumoricidal effect was significantly enhanced with the increase of oxygen content in the tissue ( t=3.46, P<0.01). In in vitro experiments, the mean oxygen depletion rate was about 0.16 mm Hg/Gy for conventional irradiation and 0.16-0.18 mm Hg/Gy for FLASH irradiation, which did not change significantly with the increase of oxygen content. FLASH irradiation was associated with an oxygen effect. When the partial pressure of oxygen decreased from physioxia to hypoxia, the OER value significantly reduced. Conclusions:Normal tissues and organs are in physioxia, which exhibits a lower oxygen content than that in the air. FLASH irradiation can consume a proportion of oxygen, producing an oxygen effect. When oxygen content decreases, the oxygen depletion rate slows down after FLASH irradiation.

Objective:To conduct a comparative analysis of the oxygen depletion and oxygen effect of FLASH irradiation and conventional irradiation by direct measurement of oxygen content.Methods:The oxygen content in different tissues and organs of mice was measured using a phosphorescent probe. A subcutaneous xenograft tumor model in mice was established, to receive electron-beam irradiation at different doses and dose rates. The oxygen depletion of tumor and normal tissue was analyzed, and tumor control was evaluated. The oxygen depletion of conventional irradiation and FLASH irradiation was further analyzed using an in vitro model. The survival fraction (SF) of normal cells after conventional irradiation and FLASH irradiation was calculated using colony formation assay under different partial pressures of oxygen, and the data were fitted to the oxygen enhancement ratio (OER) curve. Results:The mean oxygen content of subcutaneous xenograft tumor in mice was 1.28%, suggesting hypoxia. The mean oxygen content of normal tissue ranged from 3.51% to 6.53%, suggesting physioxia. In animal experiments, oxygen depletion was not observed during conventional irradiation. High-dose-rate (20 Gy/s) and ultra-high-dose-rate (FLASH, 40 Gy/s) irradiation produced oxygen depletion. During FLASH irradiation, with the increase of oxygen content, the oxygen depletion was 0.1-0.2 mm Hg/Gy for tumor tissue and 0.19-0.21 mm Hg/Gy for skin tissue, which tended to stabilize. FLASH irradiation maintained equivalent tumor control compared to conventional irradiation. The tumoricidal effect was significantly enhanced with the increase of oxygen content in the tissue ( t=3.46, P<0.01). In in vitro experiments, the mean oxygen depletion rate was about 0.16 mm Hg/Gy for conventional irradiation and 0.16-0.18 mm Hg/Gy for FLASH irradiation, which did not change significantly with the increase of oxygen content. FLASH irradiation was associated with an oxygen effect. When the partial pressure of oxygen decreased from physioxia to hypoxia, the OER value significantly reduced. Conclusions:Normal tissues and organs are in physioxia, which exhibits a lower oxygen content than that in the air. FLASH irradiation can consume a proportion of oxygen, producing an oxygen effect. When oxygen content decreases, the oxygen depletion rate slows down after FLASH irradiation.

Objective:To compare the effects on DNA strand break induced by ultra-high dose rate (FLASH) electron beam and conventional irradiation, and investigate whether FLASH effect was correlated with a reduction of radiation response.Methods:Aqueous pBR322 plasmid was treated with FLASH (125 Gy/s) and conventional irradiation (0.05 Gy/s) under physioxia (4% O 2) and normoxia (21% O 2). Open circle DNA and linear DNA were detected by agarose gel electrophoresis, and the plasmid DNA damage was quantified with an established mathematical model to calculate the relative biological effect (RBE) of DNA damage. In some experiments, Samwirin A (SW) was applied to scavenge free radicals generated by ionizing radiation. Results:Under physioxia, the yields of DNA strand breakage induced by both FLASH and conventional irradiation had a dose-dependent manner. FLASH irradiation could significantly decrease radiation-induced linear DNA compared with conventional irradiation ( t=5.28, 5.79, 7.01, 7.66, P<0.05). However, when the aqueous plasmid was pretreated with SW, there was no difference of DNA strand breakage between FLASH and conventional irradiation ( P>0.05). Both of the yields of open circle DNA and linear DNA had no difference caused by FLASH and conventional radiotherapy at normoxia, but were significantly higher than those under physioxia. In addition, the yields of linear DNA and open circle DNA induced by FLASH irradiation per Gy were (2.78±0.03) and (1.85±0.17) times higher than those of conventional irradiation, respectively. Conclusions:FLASH irradiation attenuated radiation-induced DNA damage since a low production yield of free radical in comparison with conventional irradiation, and hence the FLASH effect was correlated with oxygen content.

OBJECTIVETo explore the molecular basis for three pedigrees affected with hypophosphatemia vitamin D resistant rickets (X-linked hypophosphatemia, XLH).

METHODSPeripheral blood samples from the three pedigrees were collected. Following DNA extraction, the 11 exons and flanking regions of the PHEX gene were subjected to PCR amplification and direct sequencing. Pathogenicity of identified mutations was evaluated through genotype-phenotype correlation.

RESULTSFor pedigrees 1 and 2, pathogenic mutations were respectively identified in exon 8 (c.871C>T, p.R291X) and exon 15 (c.1601C>T, p.P534L) of the PHEX gene. For pedigree 3, a novel mutation (c.1234delA, p.S412Vfs*12) was found in exon 11 of the PHEX gene, which caused shift the reading frame and premature termination of protein translation.

CONCLUSIONThe three mutations probably account for the XLH in the affected pedigrees. The discovery of novel mutations has enriched the spectrum of PHEX gene mutations.

Objective: To explore the influencing factors of slow blood flow phenomenon after emergency percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (AMI). Methods: Clinical and PCI angiographic data of 488 patients, who were diagnosed as AMI and received primary PCI in our hospital from Jan 2010 to Jun 2011, were retrospectively analyzed. Patients were divided into slow blood flow group (n=51, TIMI flow ≤ grade 2) and normal flow group (n=437, TIMI flow= grade 3). Their clinical characteristics between two groups were compared. Results: Compared with normal flow group, there were significant reductions in percentages of thrombus aspiration (75.3% vs. 60.8%) and application of platelet glycoprotein IIb/IIIa receptor antagonist (81.7% vs. 68.6%) during PCI, and significant rise in total length of implanted stents [(31.8±12.2) mm vs. (35.7±12.0) mm] in slow blood flow group, P<0.05 all. Multi-factor Logistic regression analysis indicated that percentages of thrombus aspiration during PCI and total length of stents were independent influencing factors for slow blood flow (P<0.05 both). Conclusion: Percentages of thrombus aspiration and total length of stents during PCI are independent influencing factors for slow blood flow.