ABSTRACT
Objective@#For computer-aided Chinese medical diagnosis and aiming at the problem of insufficient segmentation, a novel multi-level method based on the multi-scale fusion residual neural network (MF2ResU-Net) model is proposed.@*Methods@#To obtain refined features of retinal blood vessels, three cascade connected U-Net networks are employed. To deal with the problem of difference between the parts of encoder and decoder, in MF2ResU-Net, shortcut connections are used to combine the encoder and decoder layers in the blocks. To refine the feature of segmentation, atrous spatial pyramid pooling (ASPP) is embedded to achieve multi-scale features for the final segmentation networks.@*Results@#The MF2ResU-Net was superior to the existing methods on the criteria of sensitivity (Sen), specificity (Spe), accuracy (ACC), and area under curve (AUC), the values of which are 0.8013 and 0.8102, 0.9842 and 0.9809, 0.9700 and 0.9776, and 0.9797 and 0.9837, respectively for DRIVE and CHASE DB1. The results of experiments demonstrated the effectiveness and robustness of the model in the segmentation of complex curvature and small blood vessels.@*Conclusion@#Based on residual connections and multi-feature fusion, the proposed method can obtain accurate segmentation of retinal blood vessels by refining the segmentation features, which can provide another diagnosis method for computer-aided Chinese medical diagnosis.
ABSTRACT
Although heterologous biosynthesis of polyketide erythromycin has been successfully achieved in Escherichia coli, the titer remains at a very low level (-10 mg/L). In this study, based on genome-scale metabolic model of E. coli, in silico method flux distribution comparison analysis was used to discover novel potential targets for heterologous 6-dEB biosynthesis. Synthetic small regulatory RNAs (sRNAs) was used to experimentally test 12 down-regulated targets. The results showed that repression of each of these target genes e.g. lsrC and ackA led to significantly improve heterologous 6-dEB biosynthesis. Using co-repression of lsrC and ackA, 6-dEB titer was improved by 59.9% in shake-flask with a maximum yield of 22.8 mg/L. This study indicates that combined flux distribution comparison analysis and synthetic small regulatory RNAs is an effective strategy to improve 6-dEB production in E. coli.
Subject(s)
Down-Regulation , Erythromycin , Escherichia coli , Genetics , Metabolism , Industrial Microbiology , Methods , RNAABSTRACT
AIM: To observe the effects of Salvia miltiorrhiza Bunge.f.alba. (Sal) on the mitochondrial ultra-structure, oxidative stress and apoptosis induced by ischemia injury in a rat model of focal cerebral ischemia and reperfusion.METHODS: The middle cerebral artery occlusion/reperfusion (MCAO/R) rat model was established by a modified Longa occlusion method. Adult male SD rats were randomly divided into control group, simple ischemia reperfusion group, Sal with ischemia reperfusion group and butylphthalide with ischemia reperfusion group. To study the protective effects of Sal and its mechanism, the intervention of Sal was given and the ultra-structure of mitochondria, functions of mitochondria under oxidative stress and the incidence of apoptosis of brain cells were determined.RESULTS: Many electron dense toxic granulation and vacuolus in mitochondria were observed in the rat brain of focal cerebral ischemia and reperfusion. Under the condition of ischemia and reperfusion, the mitochondria membrane was disaggregative, and the tubular cristae of mitochondrion disappeared. MDA content was obviously increased and the activity of glutathione peroxidase decreased significantly. The apoptosis of brain cells were observed in a great quantity. The changes of ultra-structure of mitochondria and the activity of GSH-Pxase were significantly improved by the treatment of Sal. Furthermore, treatment with Sal delayed the decrease of GSH-Pxase activity, and inhibited the increase in MDA content in brain tissue after ischemia and reperfusion. The incidence of apoptosis of brain cells was also decreased.CONCLUSION: Sal protects the brain tissue from ischemia injury.