Objective To explore the relationship between the types of female breast density and age and breast cancer .Methods By accepting the digital mammography X -ray examination for 5 006 women cases and according to the ACR BI -RADS standard in the fourth edition ,the breast density assessment was quantified . We analysed the relationship between the breast density and age and breast cancer .Results In 5 006 cases,the average female age was between 44.22 ±8.09 years old,median age was 43 years old.The components of the breast density were fat type , small amount type , large amount type and compact type each count were 256 (5.11%),726(14.51%),3 719(74.29%),305(6.09%)respectively.By dividing into different age -group to analyze the breast density,there was significant statistical differences of the breast density among age -groups(P<0.001).Among them the breast cancer were 184 cases.Age was between 51.26 ±10.15 years old.Breast cancer in each breast density were fat type 10.16%(26/256),small amount type 9.09%(66/726),large a-mount type 2.45%(91/3719)and compact type 0.33%(1/305).There were statistical differences among age -groups and breast densities and breast (P<0.001).Conclusion Age plays a very important effects on the fe-male breast density .The lower breast density is a high risk factor to breast cancer occurrence .

Objective To investigate the expressions of NBS1 mRNA and protein in the salivary gland of irradiated rats and explore the role of NBS1 in the repair of radiation injury of salivary gland epithelial cells.Methods Eighty rats were randomly divided into two groups for radiation and control (n =40 each).The rats were fractionally exposed to 3 Gy of 60Co γ-rays once in two days,leading to an accumulation dose of 3,6,9,12,15 Gy.The sham-irradiated controls were anesthetized in parallel but without irradiation.After 2-4 h of irradiation,the rats were sacrificed,IHC and RT-PCR were used to detect the expressions of NBS1 protein and mRNA in parotid and submandibular glands,and the ultra-structural changes in the glands were observed by a transmission electron microscopy.Results After irradiation,the salivary glands became atrophy and the parotid gland cells were damaged more serious than the submandibular gland cells.Compared with the controls,with the groups of dose,at 9,12,15 Gy in parotid gland (t =7.10,17.93,20.86,P ＜ 0.05),at 12,15 Gy in the submandibular gland (t =3.13,7.53,P ＜0.05),the expression of NBS1 mRNA was reduced.With the groups of dose at 9,12,15 Gy in paretid gland (t =4.29,17.91,91.29,P ＜ 0.05 ),the dose at 12,15 Gy in submandibular gland ( t =4.61,11.84,P＜0.05),the expression of NBS1 protein in serous cells,and the dose at 12,15 Gy in parotid gland ductal epithelial cell ( t =3.09,5.62,P ＜ 0.05) were reduced.But in the ductal epithelial cells as well as muoass cells in the submandibualr gland were steadily.Conclusions After irradiation,NBS1 at both protein and mRNA levels was dropped in the salivary gland of rats,which might contribute to the repair of radiation injury of salivary gland.

Abstract Oral diseases are the most important public health problems that have not received due attention, especially among college students. Based on the analysis of literatures on oral health status and behaviors of college students, the paper systematically summarizes the relevant research situation, points out the existing problems. Suggestions and countermeasures, such as attaching importance to the investigation and research on oral health of college students, improving the quality and level of scientific research on oral health of college students, exploring more effective comprehensive intervention measures for oral diseases and oral health education, should be implemented as projects are put forward, so as to provide basis for improving the oral health status of Chinese college students and promoting relevant research level.

Objective To investigate the effects of silencing the gene of single-stranded DNA-binding protein 1 (SSB1) on proliferation and DNA repair of rat submandibular gland (SMG) cells after irradiation, and explore the relationship between SSB1 and DNA damage repair. Methods Primary rat SMG cells were obtained by mechanical-enzyme digestion and identified by immunohistochemistry. The cells were divided into three groups, including blank control, negative control and shRNA transfection group. The shRNA was transfected into cells by recombinant adenovirus vector. Real-time quantitative PCR ( qRT-PCR) was used to detect the expression of SSB1 after silencing. The cell viability was detected by CCK-8 assay. Immunofluorescence analysis was performed to observe the dynamic formation of γ-H2AX foci. Results The SMG cells were positively stained for both Pan CK and α-Amylase. The efficiency of shRNA transfection was about 90%at 72 h post-transfection. Compared with the blank control group, the expression of SSB1 was significantly decreased in the cells transfected with shRNA (t=16. 24, P<0. 05). The cell viability of shRNA transfection group without irradiation was decreased indistinctively and became lower than the blank control group significantly until 120 h(t=3. 29, P<0. 05). After radiation with 5 Gy of γ-rays, the cell viability of shRNA transfection group was lower than that of the control groups significantly (F=10. 19-30. 13, P<0. 05). Silencing the expression of SSB1 could increase the number ofγ-H2AX foci in SMG cells at different time of radiation. Conclusions After silencing of the expression of SSB1, the SMG cells could be more radiosensitive, which indicats that SSB1 may play an important role in DNA damage repair after radiation.