OBJECTIVEThis study aims to identify the crack tip stress intensity factor of the propagation process, crack propagation path, and the changes in the shape of the crack tip by the finite element method.

METHODSThe finite element model of dentino-enamel junction was established with ANSYS software, and the length of the initial crack in the single edge was set to 0.1 mm. The lower end of the sample was fixed. The tensile load of 1 MPa with frequency of 5 Hz was applied to the upper end. The stress intensity factor, deflection angle, and changes in the shape of the crack tip in the crack propagation were calculated by ANSYS.

RESULTSThe stress intensity factor suddenly and continuously decreased in dentino-enamel junction as the crack extended. A large skewed angle appeared, and the stress on crack tip was reduced.

CONCLUSIONThe dentino-enamel junction on human teeth may resist crack propagation through stress reduction.

Objective To study the expression of P16、Ki-67 gene protein in esophageal squamous cell carcinoma,and its relation with lymph node metastasis、 prognostis.Methods The SP immunohistochemical method was used to detect the expression of P16 、Ki-67 gene protein in 56 cases with esophageal squamous cell carcinoma,and its normal paraneoplastic rectal mucous tissues.Results The positive expression rate of P16 in normal paraneoplastic rectal mucous tissues was 89.29%(50/56),and 42.86%(24/56) in esophageal squamous cell carcinoma,there was significant difference between the two groups(all P＜0.05);the positive expression rate of Ki-67 in normal paraneoplastic rectal mucous tissues was 8.93%(5/56),and 33.93%(19/56) in esophageal squamous cell carcinoma,there was also significant difference between the two groups(all P＜0.05).In well differentiated groups of esophageal carcinoma the positive expression rate of P16 was significantly higher than that in moderately differentiated group、poorly differentiated group(P＜0.05);in bad progressed group of esophageal carcinoma the positive expression rate of Ki-67 was higher than that in good progressed group(P＞0.05);The positive expression rate of P16、Ki-67 in lymph node metastasis was significantly higher than that in without lymph node metastasis(P＞0.05).In the exist period after operation over three years groups,the positive expression rate of P16 57.69%(15/26) was significantly higher than that in the groups of the exist period after operation non-over three years 30.00%(9/30)(χ2 =4.36,P＜0.05),in the exist period after operation non-over three years groups the positive expression rate of Ki-67 46.67%(14/30) was higher than that in the exist period after operation over three years group 19.23%(5/26)(χ2 =4.68,P＜0.05).Conclusion P16、Ki-67 were objective markers to estimate the behaviors of esophageal squamous cell carcinoma and to evaluate the development and predict the mettastasis of tumors of patiens.

BACKGROUND:Industrialization of new-born bovine serum and abundant resource of bovine lendon enable industrialization of medical collagen sponge.OBJECTIVE:To prepare collagen sponge with new-born bovine tendons by inoculating Veto cells,primary embryo skin cell of Tianzhu White Yak and lamb testicle cell of Minxian black fur sheep of the tissue scaffold of collagen sponge.and observe the biocompatibility of collagen sponge with three different cells.DESIGN,TIME AND SETTING:Repetitive measurement was performed at the Key Laboratory of State Nationalities Afrairs Committee,College of Life Sciences and Engineering,Northwest University for Nationalities from February to May 2006.MATERIALS:Tendons of new-born bovine within 24 hours were digested by glacial acetic acid and pepsinum firstly and then salting-out,dialysis and vacum freeze drying were performed to prepare collagen sponge.f2 passage of embryo skin cells of Tianzhu Whit Yak and f2 passage of lamb testicle cells of Minxian black fur sheep were prepared by out laboratory;Vero cells were provided by Union Medical University.METHODS:In a 6-hole plate,the Vero cell,embryo skin cells of Tianzhu White Yak and lamb testicle cells of Minxian Black Fur Sheep were inoculated into the collagen sponge pretreated by ultraviolet and sterilized by ozone.and incubated in 5%CO2 at 37℃.In addition,cells only inoculated ia a culture plate served as control. MAIN OUTCOME MEASURES:Inverted phase contrast microscope was used to observe cell growth condition in the collagen sponge and 6-hole plate at 5,12,24 and 72 hours.In addition,Coomassie brilliant blue as well as HE staining were conducted at 11 days after culture to identify the culture.RESULTS:Five hours after inoculation,cell adherence and expansion was observed at the bottom of culture plate.and some of the cells showed division.On the surface of collagen sponge.a round cell arrangement was observed.After inoculation of 48-72 hours,monolayer was found at the bottom of the plate.On the 11th day of culture.Coomassie brilliant blue and HE staining of three kinds of cells showed there were lager amount of cells well grew in the holes of collagen sponge,and the collagen sponge turned to be eminent,transparent and tenacious.CONCLUSION:The collagen sponge made from new-born bovine tendons exhibit good biocompatibility with three kinds of cells from different animals and tissues,and can be served as culture seaffoId of skin cells,tenal ceils.and testicle cells.

Objective: To investigate the learning cognition and demand of medical college undergraduates for statistics course and its teaching effect, so as to better carry out the teaching work of statistics course and provide better teaching experience. Methods: A total of 319 undergraduates from 11 medical universities and colleges who had finished statistics course were involved to conduct a questionnaire survey by using the online questionnaire survey method. Results: The senior undergraduates (grade 3, grade 4, grade 5) participated in statistic course accounted for a large proportion of 94.60%; 61.90% subjects thought the course was difficult. For undergraduate public health majors and non-public health majors, more than 90% considered that it was necessary to set up the corresponding statistics courses; about 4.00% did not like the corresponding statistics courses; 75.87%, 69.52% and 50.16% thought that "teaching method", "teaching content" and "class schedule" were the main reason influencing the statistics course, respectively; and 61.9% thought that case teaching was the best way to master the course. The results also showed that all subjects had a common comprehending of statistical theory and a poor comprehending of software operation skills. About 90% of the research subjects had requirement for theoretical knowledge or software operation. Conclusion Colleges and universities should make theoretical courses more targeted, increase the proportion of case teaching, strengthen the teaching of software operation skills and appropriately set up corresponding training courses, to solve the problem that it is difficult to achieve satisfactory teaching effect.

Objective To observe the value of apparent diffusion coefficient(ADC)for evaluating short-term efficacy of TACE for treating colorectal cancer liver metastases(CRLM).Methods Data of 60 liver metastases in 28 CRLM patients who underwent TACE were retrospectively analyzed.Based on MRI after the first TACE,according to the response evaluation criteria of solid tumors,the liver metastases were divided into response group(n=38)and non-response group(n=22).ADC parameters obtained with diffusion weighted imaging(DWI)before and after TACE,including ADC before TACE(ADCpre),after the first TACE(ADCpost1)and after the second TACE(ADCpost2)were compared between groups,while ADC change value(ΔADC)and the percentage of ΔADC were calculated.The maximum diameter of the target foci were measured,and the correlation between ΔADCpost1 and the change of the maximum diameter of target foci were analyzed.Receiver operating characteristic curve was drawn,the area under the curve(AUC)was calculated to observe the efficacy of ΔADCpost1 for evaluating short-term efficacy of TACE for CRLM.Results No significant difference of ADCpre was found between groups(P=0.484).After the first TACE,ADCpost1,ΔADCpost1 and percentage of ΔADCpost1 in response group were all higher than those in non-response group(all P＜0.05).After the second TACE,no significant difference of ADCpost2,ΔADCpost2 nor percentage of ΔADCpost2 was found between groups(all P＞0.05).The maximum diameter change of the target foci after the first TACE was(-0.48±0.93)cm,which was negatively correlated with ΔADCpost1(rs=-0.347,P=0.007).AUC of ΔADCpost1 for evaluating short-term efficacy of TACE for CRLM was 0.717.Conclusion ADC had good efficacy for evaluating short-term efficacy of TACE for treating CRLM.

Objective:To assess the clinical effectiveness and safety of Omalizumab for treating pediatric allergic asthma in real world in China.Methods:The clinical data of children aged 6 to 11 years with allergic asthma who received Omalizumab treatment in 17 hospitals in China between July 6, 2018 and September 30, 2020 were retrospectively analyzed.Such information as the demographic characteristics, allergic history, family history, total immunoglobulin E (IgE) levels, specific IgE levels, skin prick test, exhaled nitric oxide (FeNO) levels, eosinophil (EOS) counts, and comorbidities at baseline were collected.Descriptive analysis of the Omalizumab treatment mode was made, and the difference in the first dose, injection frequency and course of treatment between the Omalizumab treatment mode and the mode recommended in the instruction was investigated.Global Evaluation of Treatment Effectiveness (GETE) analysis was made after Omalizumab treatment.The moderate-to-severe asthma exacerbation rate, inhaled corticosteroid (ICS) dose, lung functions were compared before and after Omalizumab treatment.Changes in the Childhood Asthma Control Test (C-ACT) and Pediatric Asthma Quality of Life Questionnaire (PAQLQ) results from baseline to 4, 8, 12, 16, 24, and 52 weeks after Omalizumab treatment were studied.The commodity improvement was assessed.The adverse event (AE) and serious adverse event (SAE) were analyzed for the evaluation of Omalizumab treatment safety.The difference in the annual rate of moderate-to-severe asthma exacerbation and ICS reduction was investigated by using t test.The significance level was set to 0.05.Other parameters were all subject to descriptive analysis.A total of 200 allergic asthma patients were enrolled, including 75.5% ( n=151) males and 24.5% ( n=49) females.The patients aged (8.20±1.81) years. Results:The median total IgE level of the 200 patients was 513.5 (24.4-11 600.0) IU/mL.Their median treatment time with Omalizumab was 112 (1-666) days.Their first dose of Omalizumab was 300 (150-600) mg.Of the 200 cases, 114 cases (57.0%) followed the first Omalizumab dosage recommended in the instruction.After 4-6 months of Omalizumab treatment, 88.5% of the patients enrolled ( n=117) responded to Omalizumab.After 4 weeks of treatment with Omalizumab, asthma was well-controlled, with an increased C-ACT score [from (22.70±3.70) points to (18.90±3.74) points at baseline]. Four-six months after Omalizumab administration, the annual rate of moderate-to-severe asthma exacerbation had a reduction of (2.00±5.68) per patient year( t=4.702 5, P<0.001), the median ICS daily dose was lowered [0 (0-240) μg vs. 160 (50-4 000) μg at baseline] ( P<0.001), the PAQLQ score was improved [(154.90±8.57) points vs. (122.80±27.15) points at baseline], and the forced expiratory volume in one second % predicted (FEV 1%pred) was increased [(92.80±10.50)% vs. (89.70±18.17)% at baseline]. In patients with available evaluations for comorbidities, including allergic rhinitis, atopic dermatitis or eczema, urticaria, allergic conjunctivitis and sinusitis, 92.8%-100.0% showed improved symptoms.A total of 124 AE were reported in 58 (29.0%) of the 200 patients, and the annual incidence was 0(0-15.1) per patient year.In 53 patients who suffered AE, 44 patients (83.0%) and 9 patients (17.0%) reported mild and moderate AE, respectively.No severe AE were observed in patients.The annual incidence of SAE was 0(0-1.9) per patient year.Most common drug-related AE were abdominal pain (2 patients, 1.0%) and fever (2 patients, 1.0%). No patient withdrew Omalizumab due to AE. Conclusions:Omalizumab shows good effectiveness and safety for the treatment of asthma in children.It can reduce the moderate-to-severe asthma exacerbation rate, reduce the ICS dose, improve asthma control levels, and improve lung functions and quality of life of patients.

Members of the proto-oncogene superfamily are indispensable molecular switches that play critical roles in cell proliferation, differentiation, and cell survival. Recent studies have attempted to prevent the interaction of RAS/GTP with RAS guanine nucleotide exchange factors (GEFs), impair RAS-effector interactions, and suppress RAS localization to prevent oncogenic signalling. The present study aimed to investigate the effect of the natural triterpenoic acid inhibitor glycyrrhetinic acid, which is isolated from the roots of plant species, on RAS stability. We found that glycyrrhetinic acid may bind to the P-loop of RAS and alter its stability. Based on our biochemical tests and structural analysis results, glycyrrhetinic acid induced a conformational change in RAS. Meanwhile, glycyrrhetinic acid abolishes the function of RAS by interfering with the effector protein RAF kinase activation and RAS/MAPK signalling.

Objective: To investigate the expression change, biological role and action mechanism of long non-coding RNA (lncRNA) LINC00978 in non-small cell lung cancer (NSCLC). Methods: The expression levels of LINC00978 in tumor tissues and serum samples of NSCLC patients were detected by the qRT-PCR. The effects of knockdown and overexpression of LINC00978 on the biological function of A549 cells were determined by the CCK-8, colony formation, Transwell migration and invasion assays. The action mechanisms of LINC00978 in NSCLC were investigated by the flow cytometry, qRT-PCR and western blot, respectively. Results: The expression levels of LINC00978 in the tissues ( t =2.465, P ＜0.05) and serum samples ( t =8.781, P ＜0.01) of NSCLC patients increased. The knockdown of LINC00978 inhibited the proliferation, migration and invasion of A549 cells ( P ＜0.01) and induced cell cycle arrest at G1 phase and apoptosis of A549 cells ( P ＜0.01). The knockdown of LINC00978 downregulated the expression of Cyclin D1 and Bcl-2 , and upregulated the expression of Bax ( P ＜0.05). In addition, the knockdown of LINC00978 inhibited the expression of N-cadherin, Vimentin, Snail, Slug and Twist, and promoted the expression of E-cadherin ( P ＜0.05). The overexpression of LINC00978 had the opposite effect. Conclusion LINC00978 is highly expressed in NSCLC and can promote the occurrence and progression of NSCLC, which may serve as a potential target for the diagnosis and therapy of NSCLC.