Aging is associated with loss of muscle mass and strength, reduced satellite cell number, and lower regenerative potential. Testosterone increases muscle mass, strength, and satellite cell number in humans; however, the effects of testosterone on the regenerative potential of skeletal muscle are unclear. Here, we investigated the effect of testosterone on the skeletal muscle regeneration of young (2-month-old) and aged (24-month-old) male mice. We show that testosterone increases the number of proliferating satellite cells in regenerating "tibialis anterior" muscle of young and aged castrated mice 2 and 4 days postinjury. Testosterone supplementation increases the number and the cross-sectional area of regenerating fibers in both classes of age 4 days postinjury. Testosterone increases satellite cell activation and proliferation and the regeneration of both young and aged mouse muscle. These data suggest prospective application of androgens to improve the regenerating potential of the aged human skeletal muscle.
To quantify the atmospheric reactivity of diisopropyl ether (DIPE), we have conducted a study of the kinetics and mechanism of reaction 1: OH + DIPE -*> products. Kinetic measurements of reaction 1 were made using both relative (at 295 K) and absolute techniques (over the temperature range 240-440 K). Rate data from both techniques can be represented by the following: = (2.2^o-8) x 10'12 exp[(445 ± 145)/7] cm3 molecule"1 s"1. At 298 K, ki = 9.8 X 10"12 cm3 molecule"1 s"1. The products of the simulated atmospheric oxidation of DIPE were identified using FT-IR spectroscopy; isopropyl acetate and HCHO were the main products. The atmospheric oxidation of DIPE can be represented by i-C3H70-i-C3H7 + OH + 2NO -HCHO + ¿-C3H70C(0)CH3 + H02 + 2N02. Our kinetic and mechanistic data were incorporated into a 1-day simulation of atmospheric chemistry to quantify the relative incremental reactivity of DIPE. Results are compared with other oxygenated fuel additives.
The functional relationships of maximum ozone levels to non-methane organic gases (NMOG) and NO* concentrations (and emissions), which are relevant to urban ozone issues, have been investigated using data generated by a single-cell trajectory model as well as outdoor smog chamber data. A general relationship is shown to exist, at least approximately, for outdoor smog chamber simulations with initial precursors and for air masses which have initial input and continuous emissions of precursors and are diluted. When diurnally varying sunlight intensity and temperature are fixed, the relationship expresses maximum ozone concentrations as a product of the square root of effective NO* concentrations (initial input and continuous emissions) and a function of effective NMOG/ NO* ratios (R). The function of R can be approximated as a simple function involving an exponential function. The present model holds for the entire domain of effective precursor concentrations and for NMOG mixtures as well as single NMOG species. The present model (with a temperature-dependent function) represents outdoor smog chamber data reasonably well. The temperature dependence of maximum ozone levels is shown to be larger for outdoor smog chamber data than predicted by current photochemical models.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.