Studying the Temporal Dynamics of the Gut Microbiota Using Metabolic Stable Isotope Labeling and Metaproteomics.

The gut microbiome and its metabolic processes are dynamic systems. Surprisingly, our understanding of gut microbiome dynamics is limited. Here, we report a metaproteomic workflow that involves protein stable isotope probing (protein-SIP) and identification/quantification of partially labeled peptides. We also developed a package, which we call MetaProfiler, that corrects for false identifications and performs phylogenetic and time series analysis for the study of microbiome dynamics. From the stool sample of five mice that were fed with 15N hydrolysate from Ralstonia eutropha, we identified 12 326 nonredundant unlabeled peptides, of which 8256 of their heavy counterparts were quantified. These peptides revealed incorporation profiles over time that were different between and within taxa, as well as between and within clusters of orthologous groups (COGs). Our study helps unravel the complex dynamics of protein synthesis and bacterial dynamics in the mouse microbiome. MetaProfiler and the bioinformatic pipeline are available at https://github.com/northomics/MetaProfiler.git.

The Simon task and aging: does acute moderate exercise influence cognitive control?

PURPOSE: This study aimed to investigate the influence of an acute bout of moderate exercise and examine the potential lasting improvements over time in young and old adults within the same experimental paradigm over a 2-h testing period. The study was designed to assess the efficiency of selective control and the propensity to make fast impulsive reactions through the analyses of the percentage of correct responses (CAF) and the magnitude of the interference effect (delta curve) as a function of the latency of the response. METHODS: Twelve young (23 ± 2 yr) and 12 old (63 ± 2 yr) volunteers performed the Simon task while cycling (30 min of cycling at 65% of age-predicted HRmax) and after exercise cessation (post 5 min, post 35 min, and post 65 min). RESULTS: Results showed that exercise did not alter cognitive control. The benefit on reaction time performance was evident for both age groups and persisted after cessation for 15-20 min. Distributional analyses showed that younger people have a higher propensity to commit impulsive errors during exercise, which was not evident in older adults. Older adults adopted more cautious strategies, especially when the risk to commit an error was elevated. Despite the larger mean interference effect compared to younger adults, the pattern of the delta curves attests to the existence of an efficient cognitive control in older people. CONCLUSIONS: This study illustrates the effectiveness of distributional analyses and supports the idea that exercise-induced facilitation on cognitive performance can be realized across the lifespan. Future investigations should explore whether accumulated bouts of acute exercise could display an aggregate cognitive benefit, which may significantly affect independent functioning in older adults.

The fractal structure of equine articular cartilage.

The naturally occurring structure of articular cartilage has proven to be an effective means for the facilitation of motion and load support in equine and other animal joints. Cartilage has been found to be a complex and dynamic medium, which has led to an incomplete understanding of the nature and operating mechanisms acting within a joint. Although cartilage has biphasic and triphasic properties, it is believed that the performance of equine articular joints is influenced by the surface roughness of the joint cartilage (Ateshian et al., '98; Chan et al., 2011; Yao and Unsworth, '93). Various joint types with different motions and regimes of lubrication have altered demands on the articular surface that may affect cartilage surface properties. In research performed on freshly harvested samples, equine articular cartilage has been shown to possess a multiscale structure and a fractal dimension. It is thought that by determining the fractal dimension (D) of articular cartilage, a better understanding of the friction, wear, and lubrication mechanisms for biomechanic surfaces can eventually be reached. This study looks at the fractal dimensions of three different articular cartilage surfaces in the equine carpus: the radiocarpal, midcarpal, and carpometacarpal surfaces. The three surfaces provide an ideal comparison of fractal dimensions for a different range of motion, geometry, and loading. In each sample, identical treatment was performed during measurement by a stylus profilometer.

A surface roughness comparison of cartilage in different types of synovial joints.

The naturally occurring structure of articular cartilage has proven to be an effective means for the facilitation of motion and load support in equine and other animal joints. For this reason, cartilage has been extensively studied for many years. Although the roughness of cartilage has been determined from atomic force microscopy (AFM) and other methods in multiple studies, a comparison of roughness to joint function has not be completed. It is hypothesized that various joint types with different motions and regimes of lubrication have altered demands on the articular surface that may affect cartilage surface properties. Micro- and nanoscale stylus profilometry was performed on the carpal cartilage harvested from 16 equine forelimbs. Eighty cartilage surface samples taken from three different functioning joint types (radiocarpal, midcarpal, and carpometacarpal) were measured by a Veeco Dektak 150 Stylus Surface Profilometer. The average surface roughness measurements were statistically different for each joint. This indicates that the structure of cartilage is adapted to, or worn by, its operating environment. Knowledge of cartilage micro- and nanoscale roughness will assist the future development and design of treatments for intra- articular substances or surfaces to preserve joint integrity and reduce limitations or loss of joint performance.