MicroRNAs(miRNAs) is a class of small endogenous noncoding RNAs with 22 nucleotides.They can negatively regulate gene expression by inhibiting target mRNAs′translation or degrading mRNAs .Up to now, it has been proved that miRNAs play an important role in cellular proliferation , apoptosis , cell differentiation , and embryonic development .In this article , mechanism and function of miRNAs , principal methodologies in the research of miRNAs and the latest development of miRNAs in early embryonic de -velopment are discussed .

The present paper is to research the expression level of the mRNA of scavenger receptor class B type 1-receptor of high-density lipoprotein in endothelial cells after being treated by different shear stress. The second to fourth generations of the cultured human umbilical vein endothelial cells (HUVECs) were used in the experiment. The cells were divided into two groups. The first group was the control group which was not dealt with shear stress; the second group was the experimental group which concluded low shear stress group (4.2 dyne/cm2), moderate shear stress group (8.4 dyne/cm2) and high shear stress group (15 dyne/cm2). The load time was 1h, 2h, 4h and 8h, respectively. Harvesting the cells and extracting total RNA after being treated by different shear stresses, the expression level of the SR-B1 mRNA was detected by semi-quantitative RT-PCR technic. It was found that the expression of SR-B1 mRNA became weaker and weaker compared to the control group when it was stimulated continuously by the low shear stress, the lowest expression of SR-B1 mRNA appeared at 8h. In the moderate shear stress group, the expression of SR-B1 mRNA increased obviously. Compared to the control group, there was significant difference after being treated with 2h. In the high shear stress group, the expression of SR-B1 mRNA increased immediately when it was stimulated by the shear stress. And the expression of SR-B1 mRNA arrived peak value at 4h. Compared to the control group, there was significant difference after being treated for 1h. It was concluded that the harmful mechanism of the low shear stress is that it can increase the incidence of the atherosclerosis by reducing the reverse cholesterol transport and endothelial protection through decreasing the expression of the SR-B1. Otherwise, the high shear stress prevent the genesis of atherosclerosis by the contrary mechanism.
Atherosclerosis ; etiology ; Cells, Cultured ; Human Umbilical Vein Endothelial Cells ; cytology ; metabolism ; Humans ; RNA, Messenger ; genetics ; metabolism ; Scavenger Receptors, Class B ; genetics ; metabolism ; Stress, Mechanical

Objective:To analyze the predictive value of echocardiography combined with diaphragmatic ultrasound on the outcome of removing machine for patients who underwent cardiac valve replacement for mechanical ventilation.Methods:Retrospectively,a total of 57 patients who adopt mechanical ventilation after underwent cardiac valve replacement in the First People's Hospital of Yibin from January 2022 to March 2023 were selected as the study subjects.According to the results of removing machine,the patients were divided into failed group(11 cases)and successful group(46 cases).All patients underwent echocardiography combined with diaphragmatic ultrasound examination.The indicators of echocardiography,included left ventricular ejection fractions(LVEF),right ventricular fractional area change(RVFAC)and systolic myocardial velocity(Sa),between different groups were compared.The early diastolic mitral annular tissue velocity(e')was recorded to calculate the ratio of early diastolic transmitral flow velocity(E)to e'(E/e'),and the indicators of echocardiography and diaphragmatic ultrasound.Logistic regression analysis was performed to analyze the factors affecting the failure of removing machine.Receiver operating characteristic(ROC)curve was drawn to evaluate the predictive values of echocardiography and diaphragmatic ultrasound indicators for the failure of removing machine in mechanical ventilation.Results:The differences of the differences of LVEF,RVFAC and Sa between failed group and successful group were no significant(P>0.05).The E/e'value of the successful group was 10.06±1.30,which was significantly lower than 12.69±2.96 of the failed group,and the difference was statistically significant(t=2.084,P＜0.05).The diaphragm thickening fraction(DTF)and diaphragm excursion(DE)values of the successful group were respectively 41.34±10.74 and 13.04±1.18,which were significantly higher than 19.67±5.37 and 11.27±0.94 of the failed group,respectively,and the differences between the two groups were statistically significant(t=2.148,2.776,P＜0.05).The results of logistic regression analysis showed that low expression of DTF and DE,as well as high expression of E/e',were all influence factors for the failure of removing machine for patients adopted mechanical ventilation after underwent cardiac valve replacement.The ROC results showed that the best cut-off value of the prediction model was 0.0893,and the area under curve(AUC)values were 0.713(95%CI:0.646～0.758),0.710(95%CI:0.651～0.779),0.752(95%CI:0.657～0.805)and 0.886(95%CI:0.782～0.991).Conclusion:The combination of echocardiography and diaphragm ultrasound has better prediction for the outcome of removing machine,which high higher clinical application value.