As a normal physiological substance,D-galactose can induce a process similar to natural brain aging in vivo and in vitro when administered excessively,and thus it is widely used to induce brain aging models in China and abroad.The model of brain failure induced by D-galactose has the advantages of a short modeling time,low cost,and significant effect.However,the induction mechanisms are complex and diverse,and the relationships between the mechanisms are unclear,which limit the practical applications of the model.This article reviews the in vivo metabolism of D-galactose and the various mechanisms involved in the induction of brain aging,as well as the links between the mechanisms,to provide a reference for the application and development of this model and the in-depth study of brain aging.

Objective To develop a catalytic hairpin assembly(CHA)-based fluorescent assay for the detection of the target RNA of severe acute respiratory syndrome coronavirus-2(SARS-CoV-2),so as to realize the rapid nucleic acid testing of SARS-CoV-2.Methods A 24-nt segment of the SARS-CoV-2 nucleocapsid protein gene(N gene,NC_045512.2)was chosen as the target RNA and the hairpin motif 1(H1)and hairpin motif 2(H2)were designed based on the principle of CHA reaction.The H1 motif was labelled with a fluorophore group as well as a quencher group.When the target RNA was added to the hairpin motifs,CHA reaction was triggered at room temperature(25℃),which led to the amplification of fluorescence signal,thereby enabling the rapid detection of the target RNA.After the optimization of the hairpin motifs and the experimental conditions,the sensitivity and the specificity of the testing method were measured to evaluate its performance.Results We successfully constructed a CHA-based fluorescent assay specifically for the target RNA of SARS-CoV-2.With this method,testing could be completed at room temperature within 30 min.This testing method exhibited excellent specificity and could be used to accurately distinguish the perfectly-matched target RNA from the target RNA with single-base mutations.In addition,the testing method demonstrated good sensitivity,with a detection limit of 50 pmol/L.Conclusion The proposed assay enables the simple and rapid detection of the SARS-CoV-2 target RNA with excellent sensitivity and specificity,showing great promise for further optimization and subsequent clinical application for the rapid detection of SARS-CoV-2 nucleic acid.

Objective To evaluate the short-term outcomes of thoracic endovascular aortic repair (TEVAR) with outer branched and inner branched endografts in the treatment of Stanford type B aortic dissection (TBAD), and to analyze the effects of endografts on blood flow status of aortic dissection by computational fluid dynamics (CFD). Methods The clinical data of TBAD patients treated with outer branched endograft technology in outer branched endograft group and inner branched endograft technology in inner branched endograft group in Department of Vascular Surgery Tianjin Medical University General Hospital from May 2018 to December 2021 were collected, and the short-term results of two groups were analyzed retrospectively. Based on CT angiography images of patients in two groups, one typical case in each group was selected to construct personalized 3D model and CFD numerical simulation was performed. The parameters including flow field velocity distribution, wall pressure and wall shear stress (WSS) before and after surgery were compared and analyzed. Results A total of 55 cases with TBAD were enrolled, consisting of 49 cased in outer branched endograft group and 6 cases in inner branched endograft group. There was no statistical difference in baseline data between two groups, and surgical success rate were both 100%. Reconstruction of left subclavical artery(LSA) simple was 41(83.7%) cases in outer branched endograft group and all 6 cases in inner branched endograft group. In outer branched endograft group there were 5 cases with reconstruction of left common carotid artery (LCCA) combined with bridging carotic clavical artery, 2 cases with reconstruction of LCCA combined with LSA embolism, and 1 case with reconstruction of LCCA combined with LSA window. Four cases were lost during follow-up in outer branched endograft group. There were no significant differences in the aorta-related mortality rate (P=1.000), branch patency rate (P=1.000) and avoidance of secondary intervention of target vessels between the two groups during the perioperative period and follow-up period (P=0.298). After endograft implantation of two groups the flow field disturbance in dissection lesions improved significantly, aortic blood flow pattern restored normal, and local abnormally increased WSS decreased. However, the interference of inner branch on aortic arch and blood flow of branch was more obvious than that of outer branch. Conclusions Both outer branched endograft and inner branched endograft TEVAR for reconstruction of LSA had good short-term results in the treatment of TBAD. Compared with inner branched endograft, outer branched endograft has a higher anatomical fit and can restore the normal blood flow to a greater extent for aortic arch.

BACKGROUND:Mesenchymal stem cel s can differentiate into nerve cel s by chemical induction or co-culture method, but whether mesenchymal stem cel s co-cultured with Schwann cel s differentiate into neuronal-like cel s or Schwann-like cel s is stil controversial.
OBJECTIVE:To explore the inductive role of Schwann cel s derived from rats in the differentiation of human umbilical cord mesenchymal stem cel s.
METHODS:Cocultures of human umbilical cord mesenchymal stem cel s (1×109/L) and Schwann cel s (1×109/L) from neonatal rats were performed using transwel culture dishes. After 2 weeks of cocultures, morphology of the cultured human umbilical cord mesenchymal stem cel s was observed, and the phenotypic changes of cel s were also detected with immumocytochemistry techniques.
RESULTS AND CONCLUSION:After 2 weeks of cocultures, some differentiated cel s showed neuron-like morphology, and expressed nestin, NF-200 andβ-III-tubulin, but did not express Schwann cel special marker S100 and oligodendrocytes special marker MAB1580. These findings indicate that human umbilical cord mesenchymal stem cel s can transdifferentiate into neuronal-like cel s by cocultures with rat’s Schwann cel s.

Objective To investigate the effects of labeling Schwann cells with different concentrations of SPIO, and to investigate the feasibility of in vitro MR imaging. Methods The C57BL/6 mices'Schwann cells were isolated, purified, and then 0.5 × 106, 1.0 × 106, 5.0 × 106 cells were labeled with 25.0 μg/ml, 50.0 μg/ml SPIO. Prussian blue stain and transmission electron microscope (TEM) were performed for showing intracellular iron. The signal intensity of cells were evaluated by 3.0 MRI with different sequences in vitro. Results Different cell population (0.5 × 106, 1.0 × 106,5.0 × 106) were cultured with different concentration SPIO about 24 hours. Dyeing degree of labeling cells stained by Prussion blue gradually deepened from 25.0 μg/ml to 50.0 μg/ml. Transmission electron microscope indicated that iron particles accumulated inendosomes/lysosomes. The MR signal intensity of labeling cells were inversely correlated with the concentration of SPIO groups in T2WI and GRE/30° imaging in vitro. Conclusion Schwann cells could be labeled effectively with SPIO, and MRI could be used to monitor these labeled cells in vitro.