Physical activity and transitioning to retirement: evidence from the China health and retirement longitudinal study.

BACKGROUND: The impact of retirement on physical activity among older individuals remains ambiguous. This study aims to investigate the influence of retirement on physical activity and delineate the trajectories of physical activity changes during the retirement transition among elderly Chinese residents. Additionally, we endeavor to examine the factors that contribute to each trajectory. METHODS: This longitudinal cohort study used data from four surveys of the China Health and Retirement Longitudinal Study and included a sample of 428 individuals who underwent formal retirement and provided information on physical activity. We employed generalized estimating equation to explore the impact of the retirement transition on physical activity among Chinese older adults. Latent class growth analysis was used to identify distinct trajectories of physical activity, and binary logistic regression was performed to identify pre-retirement factors influencing changes in physical activity. RESULTS: Our findings indicate that retirement can lead to a decline in physical activity among older Chinese residents (OR = 0.85, 95%CI 0.75 ~ 0.97). We identified three distinct trajectories of physical activity during the retirement transition: Trajectory 1 - "sustained low level of physical activity" (7.94%); Trajectory 2 - "middle level of physical activity with gradual decline" (69.16%); Trajectory 3 - "sustained high level of physical activity with significant fluctuations" (22.90%). Furthermore, we discovered that individuals in the "middle level of physical activity and gradual decline" trajectory were more likely to have an annual income exceeding 40,000 yuan (OR = 9.69, 95%CI 1.12 ~ 83.63), reside in urban areas (OR = 2.27, 95%CI 1.14 ~ 4.52), and have a fondness for playing Mahjong (OR = 2.42, 95%CI 1.18 ~ 5.00) compared to those in the "sustained high level of physical activity with significant fluctuations" trajectory. Additionally, having an annual income exceeding 40,000 yuan (OR = 19.67, 95%CI 1.30 ~ 298.61) predicted membership in the "sustained low level of physical activity" trajectory when compared to the "sustained high level of physical activity with significant fluctuations" trajectory. CONCLUSION: Retirement represents a substantial milestone in the life course and is associated with notable alterations in physical activity patterns. Among older Chinese residents, the trajectories of physical activity during the retirement transition exhibit diverse paths and are influenced by pre-retirement factors, including annual income, residential location, and hobbies. The findings of this study have important implications for the formulation of policies aimed at promoting healthy aging among individuals approaching retirement age.

Active-Site Conformational Fluctuations Promote the Enzymatic Activity of NDM-1.

ß-Lactam antibiotics are the mainstay for the treatment of bacterial infections. However, elevated resistance to these antibiotics mediated by metallo-ß-lactamases (MBLs) has become a global concern. New Delhi metallo-ß-lactamase-1 (NDM-1), a newly added member of the MBL family that can hydrolyze almost all ß-lactam antibiotics, has rapidly spread all over the world and poses serious clinical threats. Broad-spectrum and mechanism-based inhibitors against all MBLs are highly desired, but the differential mechanisms of MBLs toward different antibiotics pose a great challenge. To facilitate the design of mechanism-based inhibitors, we investigated the active-site conformational changes of NDM-1 through the determination of a series of 15 high-resolution crystal structures in native form and in complex with products and by using biochemical and biophysical studies, site-directed mutagenesis, and molecular dynamics computation. The structural studies reveal the consistency of the active-site conformations in NDM-1/product complexes and the fluctuation in native NDM-1 structures. The enzymatic measurements indicate a correlation between enzymatic activity and the active-site fluctuation, with more fluctuation favoring higher activity. This correlation is further validated by structural and enzymatic studies of the Q123G mutant. Our combinational studies suggest that active-site conformational fluctuation promotes the enzymatic activity of NDM-1, which may guide further mechanism studies and inhibitor design.

Antibacterial and antioxidant activity of exopolysaccharide mediated silver nanoparticle synthesized by Lactobacillus brevis isolated from Chinese koumiss.

Recently, silver nanoparticles gain significant attention due to their applications in various fields. The aim of present study was to develop the eco-friendly, cost effective, and simple method to biosynthesized the silver nanoparticle using sliver nitrate as precursor. In this study, we investigated the physical characterization and biotechnological applications of biosynthesized silver nanoparticle using exopolysaccharide of probiotic Lactobacillus brevis MSR104 isolated from Chinese koumiss. Biosynthesized silver nanoparticles were characterized using the fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and elemental analyzer. The achieved results indicate that silver nanoparticles varied in sized with an average size of 45 nm. The X-ray diffraction analysis results showed that the silver nanoparticles have a crystalline nature. The results of antimicrobial assay indicated that the silver nanoparticles exhibited outstanding antimicrobial activity in dose dependent manner against both Gram's negative as well as Gram's positive. The antioxidant results indicate that the silver nanoparticles showed excellent scavenging rate against DPPH free radicals (81.4 ±â€¯1.2%) and nitric oxide free radicals (75.06 ±â€¯0.4%). Furthermore, the results of MTT assay revealed that the AgNPs significantly reduced the percentage of live HT-29 cells at higher concentration. This study concluded that the newly synthesized silver nanoparticles have antibacterial, antioxidant, and anticancer applications in agricultural and food industries.

Biotransformation of Isoeugenol into Vanillin Using Immobilized Recombinant Cells Containing Isoeugenol Monooxygenase Active Aggregates.

For efficiently enhancing the activity of isoeugenol monooxygenase, a whole cell overproducing active aggregate IEM720-18A was successfully fabricated via the fusion of amphiphilic short peptide 18A (EWLKAFYEKVLEKLKELF) and isoeugenol monooxygenase and then efficiently expressed in E. coli BL21 (DE3). Such resulting bacteria, E. coli BL21 (DE3) harboring pET30a-IEM720-18A was applied in the biotransformation of isoeugenol to vanillin with the optimization of cultivation conditions. Our results revealed that the vanillin concentration reached to the highest level (14.5 mmol/L) under the optimized reaction conditions including 1.5-g cells containing active aggregate of IEM720-18A, 10% (v/v) dimethyl sulfoxide (DMSO), 100 mmol/L isoeugenol, 50 mmol/L glycine-sodium hydroxide buffer (pH 10.5) in 10 mL reaction volume, and 200 rpm at 25 °C for 36 h. Moreover, the active aggregate IEM720-18A was immobilized with 100 mmol/L glutaraldehyde at 4 °C to improve the operational stability. The highest activity could be achieved when the reactions were carried out at 25 °C and the relative activity of the immobilized enzyme maintained over 60% after seven recycles. Our study provides a new approach to the biotransformation of isoeugenol into vanillin.