Practical Optimization and Application of Time-delay Exposure System for Mobile Digital Radiography Equipment / 中国医疗器械杂志

This study introduced a time-delay exposure system independent of the mobile digital radiography equipment. The system consisted of lithium battery, delay control circuit, micro electric motor and related auxiliary facilities. When the starting time was reached through the delay circuit, the motor pushed out the rod to squeeze the exposure button and completed the exposure. The accessories used in this system were easy to purchase and cheap. At the same time, the technology was mature and had good compatibility. The exposure success rate was high and the exposure effect was satisfactory. This time-delay exposure system had good practicability and popularization value.

Melatonin inhibits UVB-induced melanin synthesis by regulating p53-mediated premature senescence in HaCaT cells / 中华放射医学与防护杂志

Objective:To explore the mechanism and regulatory effects of melatonin on UVB-induced melanin synthesis in human immortalized keratinocytes (HaCaT), so as to provide a theoretical basis for the skin protection of melatonin.Methods:HaCaT cells were pretreated with 10 -5 mol/L melatonin and then irradiated with 80 mJ/cm 2UVB. The melanin content was detected by NaOH assay, the proportion of premature senescence cells was detected by β-galactosidase staining kit, and the protein expression levels of both p53 and tyrosinase (TYR) were detected by Western blot at 72 h after UVB exposure. After 12 h pretreatment of ATM/ATR inhibitor, p53 inhibitor and melatonin, the proportion of premature senescence and the change of melanin content in HaCaT cells were detected at 72 h after 80 mJ/cm 2 UVB irradiation. Results:Melatonin inhibited UVB-induced increases of melanin content ( t=56.65, 13.39, P<0.05) and TYR expression ( t=16.46, P<0.05) in HaCaT cells. Melatonin alleviated UVB-induced premature senescence ( t=7.139, P<0.05) and inhibited UVB-induced increase of p53 expression ( t=19.08, P<0.05) in HaCaT cells. In addition, ATM/ATR inhibitor, p53 inhibitor and melatonin all inhibited UVB-induced increase of melanin content in HaCaT cells. Conclusions:Melatonin inhibits TYR-mediated melanin synthesis by regulating p53-related premature senescence in HaCaT cells after UVB irradiation.