Objective:To observe the epidemiological characteristics and transmission chain of COVID-19 in Harbin, and to provide epidemiological evidence for improving the COVID-19 preventive measures and optimizing prevention and control strategies.Methods:The epidemic situation of COVID-19 in Harbin in January 2021 was analyzed by using the Infectious Disease Report Information Management System and the Public Health Emergency Management Information System of the China Disease Prevention and Control Information System, the epidemic situation information publicly released by the Heilongjiang Provincial Health Commission, and the epidemiological report of Heilongjiang Province Certer for Disease Control and Prevention and Harbin Center for Disease Control and Prevention. The main transmission chains were sorted out through combination of epidemiological field investigation, serological testing, gene sequencing, big data and other means.Results:From January 12 to February 4, 2021, 295 cases of COVID-19 infection (including confirmed cases and asymptomatic infections) were reported in Harbin, which affected 6 districts of Harbin and were concentrated in 41 of the 274 townships in the city. The sex ratio of male to female was 1.00∶1.12 (139∶156); the age ranged from 1 to 86 years old, and the median age was 45 years old. The proportion of confirmed cases and asymptomatic infection was 1.00 ∶ 1.02 (146 ∶ 149), and there was a significant difference in the distribution of different ages between them ( P = 0.042). The cases were mainly found through the health screening of the centralized isolation personnel (178 cases, 60.3%). Other detection methods included active screening (87 cases, 29.5%), screening of the home isolation personnel (26 cases, 8.8%), and medical treatment in medical institutions (4 cases, 1.4%). The main transmission chain of the outbreak was the case associated with a food processing enterprise, with a total of 259 cases, accounting for 87.8% of the total cases. The gene sequencing results showed that the case sequence was homologous with that of Wangkui County, Suihua City, Heilongjiang Province. Conclusions:A food processing enterprise is involved in the main transmission chain, which indicates that the epidemic prevention and control measures needs to be further optimized. Specifically, the supervision and management of food processing enterprises, cold chain storage companies and other enterprises should be strengthened. High attention should be paid to the hidden dangers of COVID-19 in large and medium sized enterprises with hermetic space in Harbin.

Funding of research projects within the category of Endemiology (H2401) funded by National Natural Science Foundation of China (NSFC) from 2010-2019 was summarized in this paper. Granted projects were categorized and analyzed based on the funding type, support institute and disease classification. The characteristics and trends of granted projects supported by NSFC were analyzed and summarized in order to provide reference for researchers to apply for projects in the future.

According to the general goal of long term development of basic science from 2021 to 2035 and the "14th Five-Year Plan" in China, starting from the reasearch characteristics and the basic situation of endemiology, this study discusses the strategic position, development law, development trend, development status and layout, development goals and realization ways of endemiology, combined with the strategic needs of the discipline, the important interdisciplinary research areas of endemiology are put forward. The purpose of this study is to promote the rapid development of basic research on endemic diseases, to provide reference for the scientific and technological layout and policy formulation of the endemiology, to provide reference for the "14th Five-Year Plan" in China, and to provide guarantee for the people in the sick area to seek health.

Based on the general goal of the medium and long term development of basic science from 2021 to 2035 and the "14th Five-Year Plan" in China, combined with the national strategic needs, this paper discusses the five priority development areas of endemiology according to the development trends and characteristics of endemiology in the next 5 - 15 years. The five areas are study on the pathogenesis and prevention measures of endemic fluorosis; study on risk assessment, pathogenic mechanism and control strategy of environmental arsenic exposure; research on the basis and application transformation of the pathogenesis of iodine nutrition-related diseases; molecular mechanism and targeted intervention of cartilage injury in Kashin-Beck disease; precise prevention and treatment, preservation of biological samples and etiology study of Keshan disease. Combined with the scientific significance and national strategic needs of various field, the authors analyze its main study directions and core scientific issues.

Objective To study the effect of T-2 toxin on proliferation and cell cycle of rat chondrocytes,in order to provide a new idea in molecular mechanism of T-2 toxin-induced chondrocyte damage.Methods Primary chondrocytes of neonatal Wistar rats were isolated and stained by toluidine blue staining and type Ⅱ collagen immunofluorescence staining.The effects of different concentrations of T-2 toxin [0 (control),1,5,10,20,50,100 μg/L)] on proliferation of chondrocytes for 24 h were detected by cell counting kit-8 (CCK-8) method,and control,1 (low dose),5 (medium dose),and 10 μg/L (high dose) T-2 toxin were selected for subsequent experiment;cell cycle changes were detected by flow cytometry;Real-time PCR and Western blotting were used to detect the effects of T-2 toxin on mRNA and protein expressions of proliferating cell nuclear antigen (PCNA) and Cyclin D1 in chondrocytes.Results With increase of T-2 toxin concentration (control,1,5,10,20,50,100 μg/L),the cell survival rates [(100.00 ± 0.00)％,(93.12 ± 1.66)％,(77.12 ± 1.11)％,(59.44 ± 4.09)％,(46.64 ± 3.86)％,(38.15 ± 3.37)％,(33.79 ± 0.99)％] were decreased,and the differences were statistically significant (F =139.21,P ＜0.05).The percentages of quiescent phase/pre-DNA synthesis phase (G0/G1 phase) ceils in 1,5,10 μg/L T-2 toxin groups [(22.03 ± 0.42)％,(30.54 ± 2.61)％,(36.01 ± 1.51)％] were significantly higher than that in control group [(13.79 ± 1.65)％,P ＜ 0.05];the percentages of DNA synthesis phase (S phase) cells [(60.27 ± 3.53)％,(53.88 ±4.38)％,(49.55 ± 2.49)％] were significantly lower than that in control group [(76.72 ± 4.24)％,P ＜ 0.05].The differences of mRNA levels of PCNA and Cyclin D1 between groups were statistically significant (F =46.80,17.97,P ＜ 0.05),and 5,10 μg/L T-2 toxin groups (0.77 ± 0.13,0.79 ± 0.08,0.60 ± 0.07,0.56 ± 0.05) were lower than the control group (0.99 ± 0.02,1.01 ± 0.01,P ＜ 0.05).The expressions of PCNA protein in 5,10 μg/L T-2 toxin groups (0.69 ± 0.03,0.49 ± 0.03) were lower than that in control group (0.92 ± 0.05,P ＜ 0.05);the expressions of Cyclin D1 protein in 1,5,10 μg/L T-2 toxin groups (0.80 ± 0.06,0.60 ± 0.07,0.33 ± 0.13) were lower than that in control group (0.95 ± 0.07,P ＜ 0.05).Conclusion T-2 toxin can inhibit the proliferation of chondrocytes,which may be worked through influencing the expression of cell cycle protein,causing cell cycle arrest,thereby inhibiting DNA synthesis.

Objective To investigate the effect of fluoride exposure on expression of miRNA (miR)-200c and its target in human osteoblast Saos-2 cells.Methods Saos-2 cells were cultured in DMEM/F-12 medium and treated with fluoride (sodium fluoride,NaF).There were two groups including:control group (0 mg/L) and fluoride group (4 mg/L).Cells were harvested after 48 hours of culture with fluoride.The expression of miR-200c,the mRNA of alkaline phosphatase (ALP),osteocalcin (BGP),the target phosphatase and tensin homolog deleted on chromosome ten (PTEN) and dual-specific phosphatase 1 (DUSP1) of miR-200c was detected by qRT-PCR.The protein expression of PTEN and DUSP1 was detected by Western blotting.Results The expressions of ALP,BGP mRNA and miR-200c in Saos-2 cells in the fluoride group (23.60 ± 1.87,9.41 ± 0.94,8.61 ± 0.26) were higher than those in the control group (1.00 ± 0.11,1.00 ± 0.07,1.00 ± 0.12).The differences were statistically significant (t =-24.084,-18.388,-8.687,P ＜ 0.05).The mRNA expressions of PTEN and DUSP1 in the fluoride group (0.63 ± 0.02,0.38 ± 0.02) were lower than those in the control group (1.02 ± 0.24,1.02 ± 0.24).The differences were statistically significant (t =3.327,5.454,P ＜ 0.05).The protein expressions of PTEN and DUSP1 in Saos-2 cells in the fluoride group (1.19 ± 0.10,0.83 ± 0.07) were lower than those in the control group (1.81 ± 0.14,1.44 ± 0.25).The differences were statistically significant (t =6.250,4.171,P ＜ 0.05).Conclusion Exposure to fluorine may increase the expression of miR-200c in Saos-2 cells,and fluorine may act on PTEN and DUSP1 through miR-200c,downregulates the mRNA and protein expression levels of PTEN and DUSP1.

Objective:To investigate the preoperational nutritional condition for the children with congenital heart disease,and to analyze the relevant factors.Methods:According to the standards of WHO,the Z-scores was used to assess the nutritional condition for the children,and the generational information questionnaire,State-Trait Anxiety Inventory,Self-Rating Depression Scale and Parent Understanding Questionnaire were used to analyze the maternal factors.Results:Stunting,underweighting and wasting represented the poor nutritional conditions,which accounted for 28.6％,25.3％ and 25.3％,respectively.Maternal accurate perception and the psychological problems such as anxiety and depression were the main relevant factors.Conclusion:The poor nutritional condition for the congenital heart disease was serious.It is very important to improve the maternal accurate perception and to relieve the maternal psychological problems for changing the nutritional condition through appropriate health education and effective intervention.

Objective To investigate the relationship between abnormal methylation in promoter regions for OPN and VSMC phenotype switching in varicosity.Methods Immunohistochemistry and Western-blot were used to evaluate the expression of SMA and OPN in VSMC.Methylation-specific PCR was used to evaluate the methylation level of OPN in VSMC of vein samples.Ultrastructure change of VSMC was observed by transmission electron microscope (TEM).Results Compared to normal vein,OPN in VSMCs were significantly highly expressed,mainly in the neointimal region (P ＜ 0.01).SMA in neointima region was in low expression (P ＜ 0.01).The density of OPN in varicose group was significantly higher (P ＜0.01).DNA methylation level of OPN was lower in varicose veins.Conclusions Hypomethylation of the promoter regions for OPN may cause high expression of OPN leading to VSMC phenotype switching and development of varicosity.

Objective To observe the effects of different levels of sodium arsenite ( NaAsO2) on mRNA expression of pigment epithelium-derived factor (PEDF) and apoptosis-related factors in PC12 cells ( rat neuron properties pheochromocytoma). Methods PC12 cells were treated with different levels of NaAsO2 [0 (control group), 2, 5, 10 μmol/L] for 24 hours. The mRNA expression of PEDF and apoptosis-related factors (Bax, Bcl-2) were detected by real-time quantitative PCR. Results There were significant differences in the mRNA expressions of PEDF between the 4 groups (F=102.28, P<0.05), the mRNA expressions of PEDF in the group of 2, 5, 10μmol/L (0.70 ± 0.07, 0.33 ± 0.04, 0.23 ± 0.10) was lower than that of control group (1.15 ± 0.11, P< 0.05); there were no significant differences in the mRNA expressions of Bax between the 4 groups (0, 2, 5, 10 μmol/L groups: 0.95 ± 0.12, 0.80 ± 0.11, 0.88 ± 0.11, 1.01 ± 0.11, F= 2.01, P> 0.05); there were significant differences in the mRNA expressions of Bcl-2 between the 4 groups (F=19.87, P<0.05), the mRNA expressions of Bcl-2 in the group of 2, 5, 10 μmol/L (0.65 ± 0.03, 0.49 ± 0.04, 0.57 ± 0.09) were lower than that of control group (0.95 ± 0.11, all P<0.05);there were significant differences in the mRNA expressions of Bax/Bcl-2 between the 4 groups (F=8.352, P<0.05), the mRNA expressions of in the group of 5, 10μmol/L (1.80 ± 0.72, 1.82 ± 0.36) were higher than that of control group (1.02 ± 0.24, all P<0.05). Conclusion NaAsO2 may increase the expression of apoptosis-related factorsBax/Bcl-2 mRNA by decreasing the expression of PEDF mRNA in PC12 cells, leading to apoptosis in PC12 cells.

Objective To observe the changes of the totle nitric oxide synthase (NOS) activity in brain tissue,the metabolism of arsenic speciations in urine and the totle contents in blood,brain after rats drinking water containing different doses of arsenic.Methods Forty SD rats were divided into 4 groups according to random number table,10 rats in each group:control group,5 mg/L NaAsO2 group,10 mg/L NaAsO2 group and 50 mg/L NaAsO2 group.The animals were allowed free access to water and food.Body mass was weighted once a week.Expose to arsenic was continued for three months,then the animals were put to death and their blood,urine and brain tissues were collected.Determination of four kinds of speciations of arsenic (3 valence inorganic arsenic,iAs3+;5 valence inorganic arsenic,iAs5+;monomethylated arsenic,MMA;dimethylated arsenic,DMA) in urine was carried out by high performance liquid chromatography-hydride atomic fluorescence spectrometry.Total arsenic concentration in blood and brain tissue was detected by Atomic Fluorescence Spectrometry.The activity of total NOS in blood and brain tissue was detected using the spectrophotometer method.Results ①Weight:at the 5th-12th week after arsenic exposure,compared with the weight of control group [(420.93 ± 21.13),(441.52 ± 28.85),(462.45 ± 30.57),(470.16 ± 31.17),(484.92 ± 32.93),(483.79 ± 29.63),(482.02 ± 29.14),(483.89 ± 29.31) g],weight of rats in 50 mg/L NaAsO2 group [(391.66 ± 32.88),(410.17 ± 33.47),(426.96 ± 33.49),(427.15 ± 32.20),(441.78 ± 33.69),(438.27 ± 33.05),(440.98 ± 33.33),(441.46 ± 32.45) g] was significantly lighter (all P ＜ 0.05).② Urine arsenic:the medians of iAs3+ content (0.00,57.30,236.33,857.80 μg/L) were compared between control group,5,10 and 50 mg/L NaAsO2 groups,the differences were statistically significant (x2 =31.982,P ＜ 0.01);the medians of iAs5+ content (0.00,0.00,80.75,162.90 μg/L) were compared between control group,5,10 and 50 mg/L NaAsO2 groups,the differences were statistically significant (x2 =24.206,P ＜ 0.01);the medians of DMA content (12.83,1 711.13,l0 386.20,37 038.90 μg/L) were compared between control group,5,10 and 50 mg/L NaAsO2 groups,the differences were statistically significant (x2 =34.338,P ＜ 0.01).③Blood arsenic:total arsenic content in serum of rats [(5.04 ± 1.57),(25.40 ± 7.33),(32.28 ± 7.75),(56.11 ± 19.87) mg/L] was compared between control group,5,10 and 50 mg/L NaAsO2 groups,the differences were statistically significant (F =27.78,P ＜ 0.05).④Brain arsenic:total arsenic content in brain tissue of 5,10 and 50 mg/L NaAsO2 groups [(0.57 ± 0.20),(1.56 ± 0.52),(3.63 ± 0.48) μg/g] was respectively compared with that of control group [(0.11 ± 0.06) μg/g],the differences were statistically significant (all P ＜ 0.05).⑤NOS activity:compared with control group [(27.69 ± 5.56) kU/L],total NOS activity [(33.63 ± 2.26),(34.19 ± 2.55) kU/L] in serum of rats in 10 mg/L NaAsO2 group and 50 mg/L NaAsO2 group increased significantly (all P ＜ 0.05);compared with control group [(1.79 ± 0.79) U/(mg·prot)],total NOS activity [(2.63 ± 0.60)U/(mg ·prot)] in brain tissue of 50 mg/L NaAsO2 group increased significantly (P ＜ 0.05).Conclusions A high dose of arsenic exposure can increase totle contents of arsenic in blood,brain and the activity of total NOS in rat brain tissue.