The telomere structure in the cell nucleus is crucial for maintaining the stability and functions of chromosomes.Telomerase is a ribonucleoprotein reverse transcriptase,which catalyzes the elongation of telomeres using its own RNA as a template,thereby counteracting the shortening of telomeres caused by chromosome replication and cell division.Due to its overexpression in over 85％of malignant tumor cells,telomerase has emerged as a highly promising biomarker and a novel target for cancer therapy.In recent years,given the importance of precise quantification of telomerase activity in guiding medical diagnosis and treatment strategies,researchers have developed various high-performance telomerase detection techniques.Among these,electrochemical biosensing technique has cause much attention due to its high sensitivity,operational convenience,rapid response,and ease of miniaturization.This paper focused on the latest advances in electrochemical sensing technique for detection of telomerase activity,aiming to provide inspiration for designing novel telomerase activity detection strategies by elucidating three unique properties of telomerase primer extension products.

Objective To explore the mechanism of myocardial toxicity caused by N-methyl-3,4-methyle-nedioxyamphetamine(MDMA),the changes of intracellular calcium oscillation mode and calcium han-dling proteins during acute exposure to different concentrations of MDMA were detected,and the in-volvement of nuclear factor κB(NF-κB)and its effect on calcium handling proteins were investigated.Methods Primary rat cardiomyocytes were cultured to establish MDMA acute exposure model,and a control group was set up.The MDMA poisoning model was divided into three concentration groups of 10,100 and 1 000 μmol/L.After 1 h of exposure,the morphological changes of cardiomyocytes were ob-served,the cytotoxicity and changes in calcium signals were measured,and the changes in calcium handling proteins RyR2,SERCA2a,PLN,NCX1 and Cav1.2 were detected.The changes of NF-κB activity and the expression of nucleoprotein p-p65(Ser311)and PKCζ after MDMA exposure,and the intervention of NF-κB inhibitors pyrrolidine dithiocarbamate ammonium(PDTC)and protein kinase C(PKC)inhibitor chelerythrine(CHE)were detected by electrophoretic mobility shift assay(EMSA)and Western blotting.The effects of PDTC intervention on calcium signals,and the expressions of RyR2,SERCA2a,PLN,NCX1 and Cav1.2 after acute MDMA exposure were also observed.Results No obvious changes were observed in the morphology of cardiomyocytes after acute exposure to MDMA,whereas the oscillation waveform of intracytoplasmic calcium ion showed irregular changes with increased oscillation amplitude,intense fluctuations,irregular frequency,and increased fluctuation range of relative optical density values.The expression of RyR2,SERCA2a and NCX1 increased,while the expression of Cav1.2 and PLN de-creased.Acute MDMA exposure could increase NF-κB activity,while PDTC and CHE intervention could inhibit NF-κB activity.In MDMA exposed group,the expression of PKCζ and nucleoprotein p-p65(Ser311)both increased and could be inhibited by CHE.After the intervention of PDTC to block NF-κB,the amplitude of calcium oscillation was lower than that of the MDMA exposed group,and the expres-sion of RyR2,SERCA2a and NCX1 decreased.There was no significant change in PLN,while the ex-pression of Cav1.2 increased.Conclusion MDMA can lead to an increase of calcium ion concentration in cardiomyocytes.Calcium ions are involved in myocardial toxicity of MDMA.The mechanism is re-lated to changes in calcium handling proteins,mainly associated with the increased expression of RyR2.MDMA can up-regulate the intracellular activity of NF-κB through the PKCζ-NF-κB pathway and affect calcium handling proteins,which aggravate intracellular calcium overload during acute MDMA exposure.

In industrial production,the expression level of drug proteins in Chinese hamster ovary cells(CHO)is influenced by many factors:the regulatory elements on transcription and translation,the ge-nomic integration sites,and the expression system.Transcription,as the first step of gene expression,largely affects protein expression,and the promoter plays a crucial role in the initiation of transcription.Most of the promoters were screened through transient transfection or random integration,but the presence of unclear copy number or random integration sites makes it difficult to accurately evaluate the promoter activity.To some extent,site-specific integration can reduce the impact of positional effects on exogenous genes and may potentially increase the expression level of exogenous genes.In the early stage of our re-search,multiple sites that can stably express exogenous proteins were identified and verified in the CHO cell genome.In this study,one of these sites(2c6)was selected for the evaluation of promoter activity.The CRISPR/Cas9 gene editing technique was used to site-specifically integrate the reporter gene(EG-FP)regulated by the simian virus early promoter(SV40),mouse elongation factor-1α(mEF-1α),chicken β-actin(cACTB)promoter,and human phosphoglycerate kinase promoter(hPGK)into the 2c6 site,respectively.The mean fluorescence intensity of the cells was analyzed by flow cytometry,and the mRNA level of EGFP was detected by qPCR to comprehensively evaluate the activity of the promoter.The results showed that the activities of the mEF-1α and mACTB promoters were better than those of SV40 and hPGK.The results of the secondary flow cytometry sorting showed that site-specific integration can more accurately evaluate the activity of the promoter in the CHO cell expression system.

Aim To express and purify rhα-Gal A with a 6 X His tag via using a serum-free expression system in high-density suspension culture of Chinese hamster ovary cells ( CHO-S) , and to verify the scavenging effect of rhα-Gal A on globular trisaccharide ceramide (Gb3 or GL3) . Methods The construction of recombinant protein expression vector, pcDNA4-GLA, was achieved by fusing the human α-galactosidase cDNA, gla, with 6 X His tag and artificial DNA synthesis. The expression plasmid was transfected into the suspended CHO-S to express rhα-Gal A and then purified. Following this procedure, we determined rhα-Gal A's expression, the enzymatic activity, and the glycosylation of the recombinant enzyme. Co-incubation with cultured cells was performed to examine whether rhα-Gal A could be taken up into the cells and effectively remove Gb3 substrates. Results rhα-Gal A was successfully expressed and purified after transiently transfecting pcDNA4-GLA into the suspended CHO-S, and the yield was up to (100 ±20. 6) mg • L

Aim To observe the effect of betulinic acid (BA) on the migration and invasion of human gastric cancer MKN-45 cells induced by transforming growth factor-pi (TGF-β1), and to explore the effect of BA on epithelial-mesenchymal transition (EMT) and the potential mechanism. Methods The MKN-45 cells were cultivated in vitro, and the effects of different concentrations of BA on the proliferation of MKN-45 cells at 24, 48 and 72 h were detected using CCK-8 method. The effects of BA (5, 10, 20 jjunol • L) and TGF-01 inhibitor LY2109761 (10 ^mol • L"

Mice ; Animals ; Alzheimer Disease/complications* ; Entorhinal Cortex/metabolism* ; Brain-Derived Neurotrophic Factor/metabolism* ; Memory Disorders/etiology* ; Thalamus/metabolism* ; Disease Models, Animal

AIM: To evaluate the application of optical coherence tomography angiography(OCTA)in diabetic patients without retinopathy(NDR)by Meta-analysis.METHODS: CNKI, WanFang Data, VIP, CBM, PubMed, and Embase databases were searched for relevant studies. The retrieval time was from the establishment of the database to October 2021. Two investigators independently screened the literature, extracted data and evaluated the quality of the included studies using the NOS scale. Meta-analysis and publication bias evaluation was performed using RevMan 5.3 and STATA, and sensitivity analysis was performed for results with large heterogeneity to ensure the accuracy of the results.RESULTS: A total of 44 studies, including 2 053 patients(2 600 eyes)with NDR and 1 775 healthy control patients(2 117 eyes), were included. The Meta-analysis was performed on 17 indexes including the area and perimeters of the foveal avascular zone(FAZ), the vascular density(VD)of FAZ-300um(FD300), acircularity index(AI), VD of macular area, ganglion cell complex(GCC)thickness and retinal nerve fiber layer(RNFL)thickness. Meta-analysis results showed that the area and perimeter of FAZ in superficial capillary plexus(SCP)and deep capillary plexus(DCP)in the NDR group were higher than those of healthy control patients, and FD300, VD of macular area and RNFL thickness were all lower than those in the control group(all P<0.05); The AI values in the NDR group were slightly higher than those in the normal control group, and the GCC thickness and VD of peri-optic papillary were lower than those in the control group, but there was no differences between the groups(P>0.05).CONCLUSIONS: Compared to the healthy control group, NDR patients had increased FAZ area and perimetry, decreased VD of macular area and RNFL thickness and early retinal microvascular damage and neurodegenerative lesions. OCTA could be used as an auxiliary tool for early diagnosis of DR.

Objective: To analyze the course of disease and epidemiological parameters of COVID-19 and provide evidence for making prevention and control strategies. Methods: To display the distribution of course of disease of the infectors who had close contacts with COVID-19 cases from January 1 to March 15, 2020 in Guangdong Provincial, the models of Lognormal, Weibull and gamma distribution were applied. A descriptive analysis was conducted on the basic characteristics and epidemiological parameters of course of disease. Results: In total, 515 of 11 580 close contacts were infected, with an attack rate about 4.4%, including 449 confirmed cases and 66 asymptomatic cases. Lognormal distribution was fitting best for latent period, incubation period, pre-symptomatic infection period of confirmed cases and infection period of asymptomatic cases; Gamma distribution was fitting best for infectious period and clinical symptom period of confirmed cases; Weibull distribution was fitting best for latent period of asymptomatic cases. The latent period, incubation period, pre-symptomatic infection period, infectious period and clinical symptoms period of confirmed cases were 4.50 (95%CI:3.86-5.13) days, 5.12 (95%CI:4.63-5.62) days, 0.87 (95%CI:0.67-1.07) days, 11.89 (95%CI:9.81-13.98) days and 22.00 (95%CI:21.24-22.77) days, respectively. The latent period and infectious period of asymptomatic cases were 8.88 (95%CI:6.89-10.86) days and 6.18 (95%CI:1.89-10.47) days, respectively. Conclusion: The estimated course of COVID-19 and related epidemiological parameters are similar to the existing data.
COVID-19 ; Cohort Studies ; Contact Tracing ; Humans ; Incidence ; Prospective Studies

ObjectiveTo observe the effect of Linggui Zhugantang （LG） on the blood-brain barrier （BBB） model of Alzheimer's disease （AD） in vitro and to explore the mechanism of LG in repairing the BBB injury in AD. MethodA total of 50 male SPF rats were randomized into five groups： high-dose （4.8 g·kg^-1）， medium-dose （2.4 g·kg^-1）， and low-dose （1.2 g·kg^-1） LG groups， western medicine （0.5 g·kg^-1 donepezil hydrochloride） group， and normal group （normal saline of equivalent volume）. They received （ig） corresponding drugs twice a day for 7 d. Drug-containing serum was respectively collected from the abdominal aorta 1 h after the last administration. The BBB injury of AD in vitro was induced with the cell co-culture method， and 6 groups were designed： normal group， model group， high-， medium-， and low-dose LG groups， and western medicine group. The model group was added with 100 μL amyloid β_1-42 （Aβ_1-42， final concentration： 5 μmol·L^-1）， and high-dose， medium-dose， and low-dose LG groups and the western medicine group were added with corresponding 10% drug-containing serum in addition to the 100 μL Aβ_1-42 （final concentration： 5 μmol·L^-1）. Cell survival rate was detected by methyl thiazolyl tetrazolium （MTT） assay， expression of BBB-related skeleton proteins （claudin-5， ZO-1， occludin）， matrix metalloproteinase-2 （MMP-2）， and matrix metalloproteinase-9 （MMP-9） by Western blot， and content of inflammatory factors interleukin-1β （IL-1β）， interleukin-6 （IL-6）， and tumor necrosis factor-α （TNF-α） by enzyme-linked immunosorbent assay （ELISA）. BBB Aβ transporter low-density lipoprotein receptor-related protein 1 （LRP-1） and advanced glycation end product receptor （RAGE） at different time points in high-dose， medium-dose， and low-dose LG groups were determined by Real-time PCR and Western blot. ResultCell survival rate of the model group was lower than that of the normal group （P<0.05） and the survival rates of the western medicine group and high-dose LG group was higher than that in the model group （P<0.05）. The skeleton proteins were down-regulated and MMP-2 and MMP-9 were up-regulated in the model group compared with those in the normal group （P<0.05）. The expression of skeleton proteins was higher （P<0.05） and that of MMP-2 and MMP-9 was lower （P<0.05） in the western medicine group and high-dose LG group than in the model group. Compared with the model group， only the medium-dose LG group showed the up-regulation （P<0.05） of claudin-5 （P<0.05） and the decrease （P<0.05） of MMP-2. IL-1β， IL-6， and TNF-α in the model group were up-regulated （P<0.05） compared with those in the normal group， and those inflammatory factors in the western medicine group and high-dose and medium-dose LG groups were lower （P<0.05） than those in the model group. LRP-1 expression was up-regulated and RAGE expression was down-regulated at 3 h compared with those at 0 h （P<0.05）， while the expression of the two became stable at 6， 12， 24， 36 h. At 3 h， LRP-1 expression was down-regulated and RAGE expression was up-regulated in model group compared with those in the normal group at 3 h （P<0.05）. Moreover， the LRP-1 content was higher and RAGE content was lower in the western medicine group and high-dose LG group than in the model group. ConclusionLG can repair the BBB injury in vitro by inhibiting the expression of inflammatory factors and MMP-2， MMP-9， promoting the expression of skeletal proteins， and regulating the balance of transporters.

Objective To investigate and control the outbreak of infection caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) in a gastroenterology intensive care unit (ICU), so as to provide reference for the prevention and control of clinical multidrug-resistant organisms (MDROs).Methods Epidemiological investigation was conducted on 3 patients with CRKP infection in a gastroenterology ICU on January 21-31, 2018, specimens were collected with environmental biology monitoring method, CRKP in environment was searched, homology between patients and environmental isolates were analyzed by pulsed-field gel electrophoresis (PFGE).Results Three patients were all isolated CRKP from sputum and blood specimens, all were male, with adjacent beds in the same ward, and treated by the same doctor.The number of isolated CRKP and infection rate in January 2018 were higher than those in other months, infection rate was significantly different (χ2=13.67, P＜0.01).A total of 102 environmental specimens were collected, including air and surface of objects, only 1 of which (nurse's uniform) was isolated 1 strain of KP.PFGE typing of KP isolated from patients and environment showed that there were two genotypes A and B, KP isolated from uniform of a nurse, hydrops abdominis and blood specimen of patient at bed 07, blood specimen of patient at bed 08, as well as sputum and blood specimen of patient at bed 09 were all type A, KP isolated from sputum specimen of patient at bed 07 was type B, KP isolated from hydrops abdominis in patient at bed 09 was not be typed.After comprehensive intervention, CRKP was not no longer isolated from 3 patients, and there was no new case in the ward.Conclusion Imperfect implementation of prevention and control measures for MDROs by health care workers may be an important cause for the spread of CRKP.