Adam P. W. Johnston

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BACKGROUND The regulation of muscle stem cells in humans in response to muscle injury remains largely undefined. Recently, interleukin-6 (IL-6) has been implicated in muscle stem cell (satellite cell)-mediated muscle hypertrophy in animals; however, the role of IL-6 in the satellite cell (SC) response following muscle-lengthening contractions in humans has(More)
Skeletal muscle aging is associated with a significant loss of muscle mass, strength, function, and quality of life. In addition, the healthcare cost of aging and age-related disease is growing, and will continue to grow as a larger proportion of our population reaches retirement age and beyond. The mitochondrial theory of aging has been identified as a(More)
Muscle and strength loss will occur during periods of physical inactivity and immobilization. Creatine supplementation may have a favorable effect on muscle mass and strength independently of exercise. The purpose of this study was to determine the effects of creatine supplementation on upper limb muscle mass and muscle performance after immobilization.(More)
The role of angiotensin II (Ang II) in skeletal muscle is poorly understood. We report that pharmacological inhibition of Ang II signaling or ablation of the AT1a receptor significantly impaired skeletal muscle growth following myotrauma, in vivo, likely due to impaired satellite cell activation and chemotaxis. In vitro experiments demonstrated that Ang II(More)
A paucity of information exists regarding the presence of local renin-angiotensin systems (RASs) in skeletal muscle and associated muscle stem cells. Skeletal muscle and muscle stem cells were isolated from C57BL/6 mice and examined for the presence of a local RAS using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR),(More)
Streptozotocin (STZ) is used extensively to induce pancreatic beta-cell death and ultimately diabetes mellitus in animal models. However, the direct effects of STZ on muscle are largely unknown. To delineate the effects of STZ from the effects of hypoinsulinemia/hyperglycemia, we injected young rats with 1) saline (control), 2) STZ (120 mg/kg) or 3) STZ and(More)
The role of angiotensin II (ANG II) in postnatal vasculogenesis and angiogenesis during skeletal muscle (SKM) regeneration is unknown. We examined the capacity of ANG II to stimulate capillary formation and growth during cardiotoxin-induced muscle regeneration in ACE inhibitor-treated ANG II type 1a receptor knockout (AT1a(-/-)) and C57Bl/6 control mice.(More)
Human genetic disorders and transgenic mouse models have shown that mitochondrial DNA (mtDNA) mutations and telomere dysfunction instigate the aging process. Epidemiologically, exercise is associated with greater life expectancy and reduced risk of chronic diseases. While the beneficial effects of exercise are well established, the molecular mechanisms(More)
The role of ANG II in skeletal muscle and satellite cell regulation is largely unknown. Cardiotoxin (CTX) was used to investigate whether muscle injury activates a local ANG II signaling system. Following injury, immunohistochelmistry (IHC) analysis revealed a robust increase in the intensity of angiotensinogen and angiotensin type 1 (AT(1)) receptor(More)
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