Objective: To understand the allocation of health staff and clinics in primary and secondary schools in Guangdong Province, so as to provide a reference for school health construction. Methods: In December 2020, a total of 17 205 primary and secondary schools in 21 cities in Guangdong Province were investigated by combining document verification and on site surveys. The allocation of health staff and clinics in different cities and types of schools was analyzed using SPSS 25.0 software. Results: The proportion of schools in Guangdong Province that met the national standard for school health staff ratio was 37.7%. Among different types of schools, the lowest ratio was found in nine year schools (33.1%), while the highest was in twelve year schools (61.3%). Among the 17 205 schools in the province, 12.6% had clinics with an area of >40 m 2, and 6.9% with occupational licenses for medical institutions. The proportion of full time health staff was 39.1%. Among all school health staffs, the proportions of permanent staff, temporary staff, and appointed staff were 47.5%, 29.0% and 23.6%, respectively. The rate of school health staff with professional qualifications was 44.9%, while 48.3% had graduated from medical related majors, and 20.9% held a bachelor s degree or higher as their first degree. There were differences among various types of schools, with primary schools having the lowest health staff configuration and professional level (24.0% and 35.7%, respectively). Conclusions There are still issues of insufficient staff and low professional level in health staff and establishment of clinics in primary and secondary schools in Guangdong Province, and the allocation is uneven across different types of schools. The allocation of clinics in the province is still in urgent need of improvement.

Objective: To investigate the association between sedentary bouts and cardiovascular disease (CVD) risk factors, and to provide a reference for controlling and reducing the incidence of CVD in children. Methods: Cluster random sampling was used to select 356 students from five primary schools in Guangzhou. Sedentary behavior and physical activity were assessed using ActiGraph GT3X accelerometers, which were worn for 7 consecutive days. According to the sedentary bout duration of each participant, sedentary time was classified into categories of 1-<5, 5-<10, 10-<15, 15-<20 and ≥20 min bouts. Physical examinations were carried out to identify cardiometabolic risk factors. Multivariate linear regression was performed to analyze the relationship between sedentary bouts and CVD risk factors. Results: After adjusting for confounding factors, the time accumulated in sedentary bouts of 5-<10, 10-<15, 15-<20 min in duration were positively associated with higher cardiometabolic risk scores ( B =1.24， 2.01 ，2.40), negatively associated with lower HDL ( B =-0.13，-0.21，-0.27). The time accumulated in sedentary bouts of 1-<5, 5-<10 , 10-<15, 15-<20 min in duration were positively associated with BMI levels ( B =1.07，1.89，2.86，3.65), and waist circumference ( B =2.79，4.81，8.04，10.14)( P <0.05). Conclusion These results suggested that sedentary bouts of 5-<20 min were associated with an unfavorable cardiometabolic risk profile. Our finding suggests no more than 20 min accumulated sedentary time for children.

Objective: To examine the association of sedentary behaviors with visual acuity among primary school children, and to provide a reference basis for the prevention and control of poor vision. Methods: Using stratified random cluster sampling method, a total of 4 969 students in grade 1-4 were selected from 5 primary schools in Guangzhou in 2017, and then were followed up in 2019. A validated questionnaire was used to collect data on children s sedentary behaviors, including doing homework, watching TV, playing computer/video games, and taking the bus/car between home and school. Visual acuity was measured in the baseline and the follow up using a 5 m standard logarithmic visual acuity chart. Multiple linear regression and Logistic regression were conducted to analyze the relationship between sedentary behaviors and visual changes. Results: The two year cumulative incidence of poor vision was 48.74%. Homework time was inversely associated with visual acuity of left eye( β=-0.012, 95%CI =-0.023- -0.002 ). Homework time was positively correlated with poor vision( OR =1.16, 95% CI =1.05-1.27). However, total sedentary time, screen time and bus/car time were not statistically associated with changes in visual acuity( P >0.05). Conclusion Increased homework time was associated with poorer vision in primary school students. Interventions to reduce the academic burden should be taken.

Objective: To investigate the associations between early life factors and the incidence of overweight and obesity and to provide a reference for childhood overweight and obesity prevention. Methods: A total of 5 172 children aged 6-11 years from 5 primary schools in Guangzhou were enrolled using stratified random cluster sampling method. After two years follow up, 3 315 children were included in the final analysis. Questionnaire was used to collect children s early life factors. Height and weight were measured objectively at baseline and follow up. Results: The incidence of overweight and obesity was 8.7% in children. After adjustment for confounders, results from the Logistic regression analysis showed that maternal pre pregnancy underweight was negatively associated with the incidence of childhood overweight and obesity( OR=0.54, 95%CI =0.38-0.76)( P <0.05). While excessive gestational weight gain during pregnancy( OR=1.55, 95%CI =1.14-2.10) and caesarean section ( OR=1.30, 95%CI =1.00-1.68) were positively associated with the incidence of childhood overweight and obesity( P <0.05). Conclusion Both excess gestational weight gain and caesarean section would increase the risk of the overweight and obesity of their offspring, while maternal pre pregnancy underweight would reduce the risk of childhood overweight and obesity.

Objective: To investigate the associations of reallocating sedentary time to different activity behaviors with body composition, and to provide a reference for prevention and control of childhood obesity. Methods: By using cluster random sampling, 1 621 students from 5 urban primary school in Guangzhou were selected in 2017. Vigorous intensity physical activity (VPA), moderate intensity physical activity (MPA), walking, sedentary behavior, and sleeping were measured by self-reported questionnaire. Inbody 230 was used to assess body composition. Multiple linear regression models were applied to examine isotemporal substitution effect of activity behaviors. Results: In younger children group (aged 6-9 years), replacing 30 min/day sedentary with VPA was associated with a 0.9% lower fat-free mass index(FFMI)(β=0.11, P=0.00). In older children group (aged 10-12 years), replacing 30 min/day sedentary with VPA was associated with a 1.0% lower FFMI(β=0.13, P=0.04); replacing 30 min/day sedentary to walking was associated with both a 2.9% lower percentage of body fat(PBF)(β=-0.65, P<0.01) and a 4.0% lower fat mass index(FMI)(β=-0.18, P=0.00). Conclusion Replacing sedentary with other intensities of physical activity is crucial for improving fatness status among children aged 6 to 12 years, especially among children aged 10 to 12 years. This current study suggests that children should increase physical activity while reducing sedentary for reducing risk of childhood obesity.

Objective: To investigate the prevalence of metabolic syndrome (MS) and to explore the relationship of MS with screen time (ST) among children aged 6-13 years in Guangzhou, China. Methods: A total of 4 523 children aged 6-13 from 5 primary schools in Guangzhou were selected using stratified random cluster sampling method. Questionnaire was used to assess children’s basic demographic characteristics and ST. Children’s height, weight, waist circumference and blood pressure were measured objectively, and their blood glucose, triglyceride and high-density lipoprotein-cholesterol were tested. -Chi-square test was performed to compare the prevalence of MS in children among different ST levels. Logistic regression model was used to explore the association between ST and MS. Results: The prevalence of MS in children was 2.4%, and that among boys (3.0%) was higher than in girls (1.7%, P=0.01). children were classified into three groups according to duration of ST: low ST (less than 1 h), moderate ST (1-2 h), high ST (higher than 2 h, 9.0% of total participants). Prevalence of central obesity, triacylglycerol and MS in high ST group was significantly higher than children with low ST(P<0.05). Children with high level of ST showed higher risks of central obesity (OR=1.43, 95%CI=1.04-1.96) and MS (OR=1.94, 95%CI=1.11-3.40) compared with low-level ST group. Conclusion Higher level of screen time associates with an increased risk of MS in children, which suggest the importance of effective early intervention.

Objective To compare the reprogramming effects and biological characteristics of two types of human odontogen-ic induced pluripotent stem cells(iPSCs).Methods Human dental pulp stem cells(DPSCs)and stem cells from apical papilla (SCAP)were isolated and primarily cultured.The Sendai reprogramming system was utilized to induce DPSCs and SCAP into iP-SCs.The morphology,reprogramming efficiency,reprogramming and time were compared between human DPSCs-iPSCs and SCAP-iPSCs.The SeV and exogenous transcriptional gene expression were detected by RT-PCR.Results Human DPSCs and SCAP were reprogrammed as iPSCs with classical ES-like clonal morphology.The reprogramming efficiencies were(0.68 ± 0.02)% and(0.7 ± 0.01)% respectively,the difference was not statistically significant(P>0.05).The reprogramming time was(26.0 ± 2.1)d and (27.0 ± 1.4)d respectively,the difference was not statistically significant(P>0.05).The RT-PCR results showed that no expres-sion of exogenous virus or transcriptional gene sequence in both iPSCs.Conclusion Human DPSCs and SCAP can be reprogrammed as virus-free and transgene-free iPSCs,which are the ideal sources of iPSCs.

Objective To compare the growth characteristics,proliferation and osteo/odontogenic differentiation capability of stem cells from human dental pulp (dental pulp stem cells,DPSCs) and apical papilla (stem cells from apical papilla,SCAP) in vitro.Methods Human dental pulp and apical papilla tissues were separated from impacted third molars of young healthy donors at the age of root development and digested by collagenase type Ⅰ and dispase type Ⅱ to derive primitive DPSCs and SCAP.Cells were then induced for osteo/odontongenic differentiation by medium containing β-glycerophosphate,dexamethasone and KH2PO4.Flow cytometry was utilized to test the expression of specific markers of stem cells,including CD24,CD34,CD45,CD90,CD105,CD146,STRO-1 and OCT-4.AR-S was used to display the mineralization structure and RT-PCR was applied to analyze the expression of bone sialoprotein (BSP),osteocalcin (OCN) and dentine sialophosphoprotein (DSPP).Results Both DPSCs and SCAP were positive for CD90,CD105,CD146,STRO-1 and OCT-4,in percentages varying according to cell type,without expression of CD34 or CD45.Only SCAP expressed CD24 positively.Both cells formed organized mineralization structure after 2 weeks of induction in time-dependent manner,with more mineralization by SCAP and expressed differentiation markers,including BSP,OCN and DSPP.Conclusion Human DPSCs and SCAP possess the characteristics of MSCs and could be differentiated into odontonblast-like cells in vitro.Both cells are approachable stem cell sources for dental tissue engineering.

Objective To comparatively study the features of two reprogramming systems of induced pluripotent stem cells (iPSCs)from human dental origin.Methods Two kinds of reprogramming system,i.e.STEMCCA lentivirus /feed layer and Sen-dai virus /matrigel were used to induce human stem cells from apical papilla(SCAP)into iPSCs,respectively.The induction efficien-cies,workload of generating iPSCs,aneuploidy karyotype ratio,complexities of eliminating exogenous transcription factors and spe-cific markers expression were compared between these two systems.Results The STEMCCA reprogramming system required to prepare the feeder cell MEF.The reprogramming efficiency was 0.1%.Transcription gene-free iPSCs cells were obtained by the Cre-loxp enzyme digestion technique at the later stage.Sendai virus reprogramming system was feeder-free and the preparation of matrigel was quite simple with unified standard.The reprogramming efficiency was 0.7%,which was much higher than that of STEMCCA system(P <0.05).The exogenous virus and transgenes could be gradually eliminated after several passages of natural subclone.Conclusion The Sendai virus/matrigle reprogramming system is much more applicable for the induction of iPSCs from dental origin than the STEMCCA system.

Objective To comparatively study the characteristics of 3 kinds of culture substrates of human odontogenic induced pluripotent stem cells(iPSCs).Methods The human odontogenic iPSCs were cultured by 3 kinds of substrates:mouse embryonic fibroblasts(MEF),matrigel and recombinant human vitronectin(VTN-N).The iPSCs growth situation was compared among three groups.Results The preparation time of these 3 kinds of substrates was 14,3,1 hlespectively,and,the difference was statistically significant (P＜0.05).The iPSCs reprogramming time was (30± 1.6),(26 ± 2.1),(27 ± 1.4) d,lespectively,wht that in the MEF group significantly higer than in other two groups (P＜0.05).The reprogramming efficiencies were 0.3 ％ ± 0.03 ％,0.56 ％ ± 0.08 ％,0.7 ％ ± 0.02 ％ respectively (P＜ 0.05).Three kinds of substrate could better support iPSCs growth and make them to maintain un-differentiation status.Conclusion with no heterologous animal components,and the adrantaga of simple pleparation,oonfrollable standard and shorter gramming time is easy to prepare,the standard is controllable and the reprogramming time is shorter,which is an ideal substrate for supporting iPSCs growth.