Objective Streptococcus sanguis is a possible candidate bacterium for the caries replacement therapy, which has no advantages in the acidic environment.The aim of the study was to construct acid-resistant strains of Streptococcus sanguis, determine its acid tolerance, and explore the mechanism of its antagonism against Sterptococcus mutans.Methods By gradually reducing the pH value of the medium, we constructed acid-resistant strains of Streptococcus sanguis, observed their growth and measured their acid tolerance according to their survival rate against lethal pH.We evaluated the competitive relationship between Streptococcus sanguis and Streptococcus mutans by plate experiment and detected the changes of related acid resistance genes by real-time quantitative PCR.Results The growth of Streptococcus sanguis and its acid-resistant strains were limited by the pH value, and that of Streptococcus sanguis was better in either acidic or normal environment.The lethal pH value of Streptococcus sanguis was 3.6, that of its acid-resistant strains was 2.3, and the survival rate of the acid-resistant strains was 66.59% in the pH 3.6 environment.In comparison, the lethal pH value of Streptococcus mutans was 2.5, that of its acid-resistant strains was 2.1, and the survival rate of the acid-resistant strains was 2.55% in the pH 2.5 environment.In the presence of chloramphenicol, the acid-resistant strains could not survive in the original lethal pH.In the sub-lethal pH environment, the expressions of the acid resistance-related genes Groel and Dnak in the acid-resistant strains were significantly up-regulated as compared with those in the original Streptococcus sanguis (P<0.05).Conclusion Streptococcus sanguis has an acid adaptability and can enhance acid resistance in the sub-lethal pH environment.Acid-resistant Streptococcus sanguis in the replacement therapy may provide some new ideas for the treatment of dental caries.

Objective To study the profiles and function of small RNA (sRNA)gene during chondrogenesis in rats so as to clarify the mechanisms of chondrocytes proliferation and differentiation.Methods All the sRNAs were identified from the female SD rats femoral head cartilages at three time points:at birth,ablactation and maturation,and three sRNA libraries were constructed.The Solexa sequencing and the bioinformatics analysis were employed to be blasted with the genomes of SD rats.Results The perfect match reads in the three libraries were screened out,which were correspondent to the 21 7 921 (41.23%),1 96 650 (38.74%)and 245 436 (41.54%)unique sRNA sequence,respectively.The percentages of 20-24 nt sRNA were 71.94% (d0),72.85% (d21),and 86.39%(d42).Half of clean sequences were 22 nt sRNA.The distribution characteristics of the reads were in line with the high-quality sRNA.More than 62% clean reads were from mature miRNA while the ratios in the three libraries were only 0.69%,0.78% and 0.63%.About 60% of the unique sRNA could not be matched with miRBase20.0 or Rfam9.1.Conclusion The distribution model of miRNA in the three libraries indicates that the miRNAs with different functions or from different sources are involved in the regulation of chondrocytes proliferation and differentiation in bone development and formation.

Objective:To investigate the difference of accuracy between magnetic induction Freehand-3D ultrasound and two-dimensional ultrasound in measuring the volume of thyroid model.Methods:Forty thyroid models were established using porcine liver, and the Archimedes procedure was set as gold standard in the measurement of the volume of each model. The accuracy of measurement of the porcine thyroid model volume between two-dimensional ultrasound and magnetic induction Freehand-3D ultrasound were compared.Results:There were no significant differences in the accuracy of measurements of thyroid model volume among two-dimensional ultrasound, magnetic induction Freehand-3D ultrasound and Archimedes procedure (all P>0.05). Compared with the Archimedes procedure, magnetic induction Freehand-3D ultrasonic method showed higher correlation coefficient of the measurement of thyroid model volume ( r=0.998). Bland-Altman analysis showed the lower measure error with a relative error of 3.42% and range of -9.57% to 12.07%. And the limits of agreement were (-1.253, 0.999) in the magnetic induction Freehand-3D ultrasonic measurement. Conclusions:Compared with two-dimensional ultrasound, the magnetic induction Freehand-3D ultrasound show higher accuracy in the measurement of the volume of the thyroid model.

The burden of cardiovascular disease in China is severe and keep increasing nowadays, while effective dietary management strategies play an important role in its primary prevention and treatment. Flaxseed is rich in lots of bioactive components like α-linolenic acid, lignan, linseed bioactive protein fragments and fi-ber, which can effectively improve a variety of heart risk factors like atherosclerosis, obesity and abnormal blood glucose, and thus has become a hot spot in researches of dietary strategies for cardiovascular diseases. As a po-tential heart-friendly food, cardiovascular-protective effects of flaxseed are particularly prominent in blood pres-sure control and lipid regulation. This article reviewed recent clinical controlled trials studying effects of flaxseed on both blood pressure and lipid profiles in different populations, and its potential hypotensive as well as lipid-lowering mechanisms, in order to lay a solid foundation for further studies.

AIM:To study the effects of noninvasive delayed limb ischemia preconditioning ( NDLIP) on ani-mal cardiac function , myocardial morphology and myocardial apoptosis after myocardial infarction ( MI ) .METHODS:Healthy SD male rats [n=45, weighing (250 ±10) g] were randomly divided into 3 groups:MI group:the animal model of MI was established by surgical ligation of left anterior descending artery ( LAD) after 2 weeks;NDLIP group:after the success of the MI animal model , NDLIP was carried out every other day until the 4th, 6th and 8th weeks;sham group:as the negative control group , the animals were taken heart LAD threading but no ligation .All rats were fed conventionally .At the end of the 4th, 6th and 8th weeks, all rats were made ventricular intubation , and then the hemodynamic parameters were recorded .The blood samples were withdrawn from the abdominal aorta and the serum was separated via centrifugation . The serum contents of Bcl-2 and Bax were measured by ELISA .Left ventricular anterior wall was homogenized .The mito-chondrial respiratory chain complexes Ⅰ,Ⅱ,Ⅲand Ⅳin the myocardial tissues were detected by ELISA .RESULTS:At the end of the 4th, 6th and 8th weeks, compared with MI group, left ventricular systolic pressure in NDLIP group was significantly increased , while left ventricular end-diastolic pressure in NDLIP group was significantly decreased ( both P<0.05).Mitochondrial respiratory chain complexesⅠ, Ⅱ, Ⅲ and Ⅳ in NDLIP group were significantly increased (P<0.05).The serum level of Bcl-2 in NDLIP group was significantly increased and Bax level was reduced remarkably (both P<0.01) .CONCLUSION:NDLIP improves the hemodynamic indexes , promotes the mitochondrial respiratory function and inhibits cell apoptosis , thus improving the prognosis of MI .

Aim To study the preventative effects of noninvasive delayed limb ischemic preconditioning ( NDLIP) on sudden cardiac death in rats with myocar-dial infarction. Methods Thirty healthy SD male rats weighting ( 250 ± 10 ) g were randomly divided into 3 groups:① myocardial infarction ( MI ) group: animal model of MI was established by making surgical ligation of animal LAD. ② MI plus NDLIP group: after the success of the animal model of MI, NDLIP was carried out every other day until 4th week. ③Sham group:as the negative control group, animals were taken heart LAD threading but no ligation. All rats were fed con-ventionally. At the end of 4 weeks, three groups of rats were administered with metaraminol ( 0. 2 mg · min-1 ) . ECG, drug cumulant of sudden death and death onset time were recorded. After sudden death, blood samples were withdrawn from abdominal aorta and serum was separated via centrifugation. ELISA method was used to measure serum caspase-3 , HSP70 and SOD concentration. Results While metaraminol led animal cardiac sudden death, the rats heart rate ( HR) kept declining with the increase of dosage of metaraminol during the administration period. Rat HR of MI+NDLIP group [ ( 479 ± 8 ) vs ( 416 ± 19 ) beat ·min-1 , ( 446 ± 32 ) vs ( 370 ± 20 ) beat · min-1 , (376 ± 53) vs (305 ± 29) beat·min-1, (307 ± 63) vs (244 ± 33) beat·min-1, (283 ± 45) vs (121 ± 35 ) beat · min-1 , P <0. 01 ] was markedly higher than that of MI group at 0 , 5 , 10 , 30 , 50 min before death. Compared with MI group, drugs cumulant to sudden death and death onset time of MI + NDLIP group [ ( 14. 58 ± 3. 03 ) vs ( 10. 76 ± 2. 73 ) mg, (72. 9 ± 15. 2 ) vs ( 53. 8 ± 13. 6 ) min, P <0. 01 ] were significantly increased. Compared with MI group, serum caspase-3 content of MI+NDLIP group was sig-nificantly reduced [ ( 2. 01 ± 0. 52 ) vs ( 2. 34 ± 0. 38 )μg·L-1 , P<0. 01 ]; HSP70 levels were remarkably increased [ ( 3. 01 ± 0. 58 ) vs ( 2. 70 ± 0. 43 ) μg · L-1 , P <0. 05 ]; SOD levels were significantly im-proved [(1. 99 ± 0. 65) vs (1. 70 ± 0. 58) mg·L-1, P<0. 01 ] . Conclusion NDLIP can prevent sudden cardiac death after myocardial infarction in rats, which may be mediated by reducing the myocardial cell apop-tosis, increasing protective protein expression and en-hancing antioxidant capacity.

Gastric cancer, a common malignant tumor in digestive system with high morbidity as well as mortality rate, is insidious at the onset and lack of effective treatments so far. A growing number of studies have shown that exosome-derived miRNAs play an important role in the occurrence and development of gastric cancer. Autocrine exosome miRNAs from gastric cancer cells regulated tumor growth, recurrence, metastasis and drug resistance, etc. Moreover, exosomal miRNAs in the tumor microenvironment can be delivered into cancer cells to facilitate intercellular communication, thus affecting the progress of gastric cancer. Due to exosomes, which were released into circulation from tumor cells, contain abundant, specific and stable miRNAs, exosome-derived miRNAs have a great potential to be used as novel diagnosis biomarkers and treatment targets of gastric cancer.(Chin J Lab Med, 2018, 41: 499-502)

Objective: To evaluate the impact of food advertising on childhood obesity by reviewing relevant literatures, and to provide evidence support for childhood obesity prevention and control strategies in China. Methods: A systematic review method was used to search relevant literatures published to November 30，2020 from 8 databases including CNKI, VIP, Wanfang Data, PubMed, Medline, SpringerLink, Web of Science, Science Direct. The high quality systematic reviews published since 2016 were included directly, and those published before 2016 were rereviewed after combined with other literatures. Results: A total of 13 articles were included for evaluation, including systematic reviews, cohort studies, randomized controlled trials and cross sectional studies. Children s exposure to food advertisements could increase energy intake. Television food advertising could influence children s food choices and increase the consumption of unhealthy foods such as sweets and sugary drinks. Children s exposure to unhealthy food advertisements could increase the risk of obesity. Conclusion Regulating the food advertisement can help reduce the risk of childhood obesity.

Objective: To evaluate the impact of sugar sweetened beverages (SSBs) tax on childhood obesity by literatures reveiew, and to provide evidence support for childhood obesity prevention and control strategies in China. Methods: A systematic review method was used to search relevant literatures published to November 30，2020 from 8 databases including CNKI, VIP, Wanfang Data, PubMed, Medline, SpringerLink, Web of Science, and Science Direct. The high quality system reviews published since 2016 were included directly, and those published before 2016 were rereviewed before combined with other literatures. Results: Twelve studies including 5 systematic reviews (or Meta analysis), 1 cohort study and 6 cross sectional studies were included. Comprehensive analysis showed that the prevention effect on childhood obesity was small or even ineffective if the tax on SSBs lower than 5%, a certain protective effect on childhood obesity could be shown if the tax on SSBs increased to 20%. From the perspective of cost benefit analysis, the implementation of SSBs tax showed certain net benefits. Conclusion SSBs tax can help reduce the risk of childhood obesity.

Objective: To evaluate the impact of community built environment and the distribution of fast food restaurants on childhood obesity, and to provide evidence support for childhood obesity prevention and control strategies in China. Methods: A systematic review method was used to search relevant literatures published to November 30，2020 from 8 databases including CNKI, VIP, Wanfang Data, PubMed, SpringerLink, Web of Science, Science Direct. The high quality system reviews published since 2016 were included directly, and those published before 2016 were reviewed before combined with other literatures. Results: A total of 20 articles were included for evaluation, including systematic reviews, cohort studies, randomized controlled trials and cross sectional studies. High walkability near the living area could increase children s physical activity levels and reduce the risk of obesity. The fast food sales environment increased the risk of obesity; while large supermarkets or health food sales environment could reduce the risk of obesity. Conclusion Improving walking suitability in residential areas and reducing the density of unhealthy fast food sales could help decrease the risk of childhood obesity.