MR Assessment of Acute Changes of Cerebral Perfusion, Metabolism, and Blood-Brain Barrier Permeability in Response to Aerobic Exercise.

BACKGROUND: It remains unclear how a single bout of exercise affects brain perfusion, oxygen metabolism, and blood-brain barrier (BBB) permeability. Addressing this unresolved issue is essential to understand the acute changes in cerebral physiology induced by aerobic exercise. PURPOSE: To dynamically monitor the acute changes in cerebral physiology subsequent to a single aerobic exercise training session using noninvasive MRI measurements. STUDY TYPE: Prospective. POPULATION: Twenty-three healthy participants (18-35 years, 10 females/13 males) were enrolled and divided into 10-minute exercising (N = 10) and 20-minute exercising (N = 13) groups. FIELD STRENGTH/SEQUENCE: 3.0 T/Phase Contrast (PC) MRI (gradient echo), T2-Relaxation-Under-Spin-Tagging (TRUST) MRI (gradient echo EPI), Water-Extraction-with-Phase-Contrast-Arterial-Spin-Tagging (WEPCAST) MRI (gradient echo EPI) and T1-weighted magnetization-prepared-rapid-acquisition-of-gradient-echo (MPRAGE) (gradient echo). ASSESSMENT: A baseline MR measurement plus four repeated MR measurements immediately after 10 or 20 minutes moderate running exercise. MR measurements included cerebral blood flow (CBF) as measured by PC MRI, venous oxygenation (Yv) and cerebral metabolic rate of oxygen (CMRO2) as assessed by TRUST MRI, water extraction fraction (E), and BBB permeability-surface-area product (PS) as determined by WEPCAST MRI. STATISTICAL TESTS: The time dependence of the physiological parameters was studied with a linear mixed-effect model. Additionally, pairwise t-tests comparison of the physiological parameters at each time point was conducted. A P-value of <0.05 was considered statistically significant. RESULTS: There was an initial drop (8.22 ± 2.60%) followed by a recovery in CBF after exercise, while Yv revealed a significant decrease (6.37 ± 0.92%), i.e., an increased oxygen extraction, and returned to baseline at later time points. CMRO2 showed a trend of increase (5.68 ± 3.04%) and a significant interaction between time and group. In addition, E increased significantly (3.86% ± 0.89) and returned to baseline level at later time points, while PS remained elevated (13.33 ± 4.79%). DATA CONCLUSION: A single bout of moderate aerobic exercise can induce acute alterations in cerebral perfusion, metabolism, and BBB permeability. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

Influence of motor capacity of the lower extremity and mobility performance on foot plantar pressures in community-dwelling older women.

Objectives: To investigate the associations of motor capacity of the lower extremity and mobility performance in daily physical activities with peak foot plantar pressures during walking among older women. Methods: Using the data collected among 58 community-dwelling older women (68.66 ± 3.85 years), Pearson correlation and multiple linear regression analyses were performed to analyze the associations of motor capacity of the lower extremity (the 30-s chair stand test, the timed one-leg stance with eyes closed, and the Fugl-Meyer assessment of lower extremity), mobility performance in daily physical activities (the average minutes of moderate to vigorous physical activity every day and the metabolic equivalents), and foot plantar pressures (peak force and peak pressure) with the age and body fat percentage as covariates. Results: (1) The motor capacity of the lower extremity has higher explanatory power for peak foot plantar pressures compared with the mobility performance in daily physical activities. (2) Higher body fat percentage was positively associated with peak force and pressure, while a lower score on the Fugl-Meyer assessment of lower extremity was negatively associated with both of them. (3) The metabolic equivalents were positively associated with the peak force, while the 30-s chair stand test was negatively associated with it. Conclusions: Mobility performance in daily physical activities can be significant predictors for peak foot plantar pressures among older women. The significant predictor variables include the Fugl-Meyer assessment of lower extremity, the 30-s chair stand test, and metabolic equivalents.

Covalent synthesis of organophilic chemically functionalized graphene sheets.

In this study, we report a scalable, fast, and easy method for preparation of organophilic chemically functionalized graphene (OCFG) sheets. The basic strategy involved the preparation of graphite oxide (GO) and the complete exfoliation of GO into graphene oxide sheets, followed by reacting with 1-bromobutane to obtain OCFG sheets. Thermogravimetric analysis, Raman spectroscopy, and Fourier transform infrared spectroscopy indicated the functionalization of GO. Transmission electron microscopy and atomic force microscopy were used to demonstrate the structure of produced graphene oxide and OCFG sheets. Ultraviolet-visible spectroscopy confirmed that OCFG sheets disperse well in organic solvents and the solutions obey Beer's law. The resulting organic dispersions are homogeneous, exhibit long-term stability, and are made up of graphene sheets a few hundred nanometers large. The ability to prepare graphene dispersions in organic media facilitates their combination with polymers to yield homogeneous composites.

Synthesis of hydrophilic and organophilic chemically modified graphene oxide sheets.

In this work, hydrophilic and organophilic chemically modified graphene oxide (CMGO) sheets were prepared through a two-step diimide-activated amidation. The hydrophilic and organophilic products were characterized by atomic force microscopy, transmission electron microscopy and ultraviolet-visible spectroscopy. The resulted dispersions are homogeneous and exhibit long-term stability, which will facilitate the combination of CMGO sheets with polymers to yield homogeneous composites.

Covalent attaching protein to graphene oxide via diimide-activated amidation.

In this paper, graphene oxide nanosheets (GOS) are functionalized by bovine serum albumin (BSA) via diimide-activated amidation under ambient conditions. The obtained GOS-BSA conjugate is highly water-soluble. Results of atomic force microscopy (AFM), Raman spectra and Fourier transform infrared spectroscopy analysis confirm that GOS-BSA conjugate contains both GOS and BSA protein. AFM image shows that GOS are fully exfoliated. Results of cyclic volatammograms show that the protein in the GOS-BSA conjugate retains its bioactivity. The present method may also provide a way to synthesize graphene-based composites with other biomolecules.

Layer-by-layer self-assembly of graphene nanoplatelets.

In this report, graphene nanoplatelets were self-assembled through the layer-by-layer (LBL) method. The graphene surface was modified with poly(acrylic acid) and poly(acryl amide) by covalent bonding, which introduced negative and positive charge on the surface of graphene, respectively. Through electrostatic interaction, the positively and negatively charged graphene nanoplatelets assembled together to form a multilayer structure. Thermogravimetric analysis, Raman spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy were used to demonstrate the modification of graphene nanoplatelets. Fourier transform infrared spectroscopy and SEM proved this method is feasible for preparing graphene-containing films. Ultraviolet-visible spectroscopy confirmed that the adsorption technique resulted in uniform film growth.

Layer-by-layer self-assembly of multiwalled carbon nanotube polyelectrolytes prepared by in situ radical polymerization.

Anionic and cationic multiwalled carbon nanotube polyelectrolytes, prepared by covalent modification of multiwalled carbon nanotubes (MWCNTs) with poly(acrylic acid) and poly(acrylamide), were used for the layer-by-layer (LBL) self-assembly of MWCNTs on different substrates with polyelectrolytes, such as poly(diallyldimethylammonium chloride) and sodium poly(styrenesulfonate). Thermogravimetric analysis, Raman spectroscopy, and scanning electron microscopy (SEM) were used to demonstrate the modification of MWCNTs. Investigations using Fourier transform infrared spectroscopy, atomic force microscopy, SEM, and ultraviolet-visible spectroscopy proved this method to be practicable for preparing LBL films.