PRMT biology during skeletal muscle disuse. / Protein arginine methyltransferase 1 (PRMT1), PRMT4 (also known as co-activator-associated arginine methyltransferase 1; CARM1), and PRMT5 are critical components of a diverse set of intracellular functions. Despite the limited number of studies in skeletal muscle, evidence strongly suggests that these enzymes are important players in the regulation of phenotypic plasticity. However, their role in disuse-induced muscle remodelling is unknown. Thus, we sought to determine whether denervation-induced muscle disuse alters PRMT expression and activity in skeletal muscle within the context of early signaling events that precede muscle atrophy. Mice were subjected to 6, 12, 24, 72, or 168 hours of unilateral hindlimb denervation. The contralateral limb served as an internal control. Muscle mass decreased by ~30% following 168 hours of disuse. Prior to atrophy, the expression of muscle RING finger 1 and muscle atrophy F-box were significantly elevated. The expression and activities of PRMT1, CARM1, and PRMT5 displayed differential responses to muscle disuse. Peroxisome proliferator-activated receptor-γ coactivator-1α, AMP-activated protein kinase (AMPK), and p38 mitogen-activated protein kinase expression and activation were altered as early as 6 hours after denervation, suggesting that adaptations in these molecules are among the earliest signals that precede atrophy. AMPK activation also predicted changes in PRMT expression and function following disuse. Our study indicates that PRMTs are important for the mechanisms that precede, and initiate muscle remodelling in response to neurogenic disuse. / Thesis / Master of Science (MSc) / Skeletal muscle is a plastic tissue that is capable of adapting to various physiological demands. Previous work suggests that protein arginine methyltransferases (PRMTs) are important players in the regulation of skeletal muscle remodelling. However, their role in disuse-induced muscle plasticity is unknown. Therefore, the purpose of this study was to investigate the role of PRMTs within the context of early, upstream signaling pathways that mediate disuse-evoked muscle remodelling. We found differential responses of the PRMTs to muscle denervation, suggesting a unique sensitivity to, or regulation by, potential upstream signaling pathways. AMP-activated protein kinase (AMPK) was among the molecules that experienced a rapid change in activity following disuse. These alterations in AMPK predicted many of the modifications in PRMT biology during inactivity, suggesting that PRMTs factor into the molecular mechanisms that precede neurogenic muscle atrophy. This study expands our understanding of the role of PRMTs in regulating skeletal muscle plasticity.

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Cisplatin, a platinum-based drug extensively utilized in chemotherapy, is effective in treating a variety of cancer forms. Clinical studies have shown that cisplatin triggers muscle wasting and dysfunction, which significantly impacts the clinical prognosis of cancer patients. Additionally, recent research revealed that pyroptosis, a highly inflammatory cell-death, mediates muscle wasting. However, its role in cisplatin-induced skeletal muscle toxicity remains unclear. Therefore, we hypothesized that cisplatin induces myotoxicity and causes adverse skeletal muscle remodeling through pyroptosis. In this study, C57BL/6 mice (10±2 weeks old) were divided into two groups: Control(saline) and Cisplatin (cisplatin). Saline and Cisplatin were respectively administered via intraperitoneal injection (i.p.) at 2.3mg/kg body weight (BW) for 5 consecutive days (first cycle), followed by 5 days of rest, and then another 5 consecutive days (second cycle), making it a total of 10 injections and a cumulative dose of 23 mg/kg BW. At day 29 (D29), the muscle function was assessed by subjecting the mice to grip force tests and weight tests. Gastrocnemius muscle tissues from sacrificed mice were collected for histological analysis. Further analysis for protein expression of pyroptosis-associated markers (TLR4, NLRP3, Caspase-1, IL-1β, IL-18, and GSDMD) was performed using immunohistochemistry and western blotting. The stimulation of TLR4 leads to the formation of the NLRP3 inflammasome which initiates the activation of Caspase-1, Il-1β and IL-18, along with the executioner of pyroptosis, GSDMD. Our data revealed that cisplatin-treatment significantly (P

This thesis is focused on frailty in old age. The frailty syndrome is the newest geriatric syndrome and can be aptly called the ultimate geriatric syndrome due to the complexity of its causes and the wide range of adverse outcomes it may lead to in older persons. Several of the important correlates of frailty, namely falls, underweight and sarcopenia, are discussed in the context of their relationship with frailty. These entities are geriatric syndromes in their own rights, sharing many common risk factors and arriving at adverse health outcomes either directly or via the pathway of frailty. In the publications that arose from this work, the risk factors of falls, in particular the relationship between medications and chronic diseases in causing falls; risk factors and outcomes of sarcopenia, in particular its relation to diabetes mellitus and other chronic diseases; and how underweight poses survival risks in both community-living and institutionalized older people, are discussed. The final publication of this series of studies demonstrated the reversibility of the frailty syndrome, showing that not all who were in the pre-frailty stage will decline. Risk factors associated with improvement or decline in the pre-frail stage were identified in the local population, and a period of relative stability opened for possible interventions was observed. This thesis thus examines the complex interplay of these syndromes in old age. It is hoped that these publications will enable further research into the underlying mechanisms of frailty and to elucidate modifiable risk factors, hence enabling older people, in particular those in the pre-frail stage, to live healthier and longer lives. / Lee Shun Wah Jenny. / Thesis (M.D.)--Chinese University of Hong Kong, 2015. / Includes bibliographical references. / Title from PDF title page (viewed on 15, September, 2016).

Thesis (Ph. D.)--University of Missouri--Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 143-155). Also available on the Internet.

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This document is a critical synopsis of prior work by Michael Dwyer submitted in support of a PhD by published work. The selected work is focused on the application of quantitative magnet resonance imaging (MRI) analysis techniques to the study of multiple sclerosis (MS). MS is a debilitating disease with a multi-factorial pathology, progression, and clinical presentation. Its most salient feature is focal inflammatory lesions, but it also includes significant parenchymal atrophy and microstructural damage. As a powerful tool for in vivo investigation of tissue properties, MRI can provide important clinical and scientific information regarding these various aspects of the disease, but precise, accurate quantitative analysis techniques are needed to detect subtle changes and to cope with the vast amount of data produced in an MRI session. To address this, eight new techniques were developed by Michael Dwyer and his co-workers to better elucidate focal, atrophic, and occult/"invisible" pathology. These included: a method to better evaluate errors in lesion identification; a method to quantify differences in lesion distribution between scanner strengths; a method to measure optic nerve atrophy; a more precise method to quantify tissue-specific atrophy; a method sensitive to dynamic myelin changes; and a method to quantify iron in specific brain structures. Taken together, these new techniques are complementary and improve the ability of clinicians and researchers to reliably assess various key elements of MS pathology in vivo.

Thesis (MSc (Physiological Sciences))--Stellenbosch University, 2008. / Introduction: Skeletal muscle atrophy is a mitigating complication that is characterized by a reduction in muscle fibre cross-sectional area as well as protein content, reduced force, elevated fatigability and insulin resistance. It seems to be a highly ordered and regulated process and signs of this condition are often seen in inflammatory conditions such as cancer, AIDS, diabetes and chronic heart failure (CHF). It has long been understood that an imbalance between protein degradation (increase) and protein synthesis (decrease) both contribute to the overall loss of muscle protein. Although the triggers that cause atrophy are different, the loss of muscle mass in each case involves a common phenomenon that induces muscle proteolysis. It is becoming evident that interactions among known proteolytic systems (ubiquitin-proteosome) are actively involved in muscle proteolysis during atrophy. Factors such as TNF-α and ROS are elevated in a wide variety of chronic inflammatory diseases in which skeletal muscle proteolysis presents a lethal threat. There is an increasing body of evidence that implies TNF-α may play a critical role in skeletal muscle atrophy in a number of clinical settings but the mechanisms mediating its effects are not completely understood. It is also now apparent that the transcription factor NF-κB is a key intracellular signal transducer in muscle catabolic conditions. This study investigated the various proposed signalling pathways that are modulated by increasing levels of TNF-α in a skeletal muscle cell line, in order to synthesize our current understanding of the molecular regulation of muscle atrophy. Materials and Methods: L6 (rat skeletal muscle) cells were cultured under standard conditions where after reaching ± 60-65% confluency levels, differentiation was induced for a maximum of 8 days. During the last 2 days, myotubes were incubated with increasing concentrations of recombinant TNF-α (1, 3, 6 and 10 ng/ml) for a period of 40 minutes, 24 and 48 hours. The effects of TNF-α on proliferation and cell viability were measured by MTT assay and Trypan Blue exclusion technique. Morphological assessment of cell death was conducted using the Hoechst 33342 and Propidium Iodide staining method. Detection of apoptosis was assessed by DNA isolation and fragmentation assay. The HE stain was used for the measurement of cell size. In order to determine the source and amount of ROS production, MitoTracker Red CM-H2 X ROS was utilised. Ubiquitin expression was assessed by immunohistochemistry. PI3-K activity was calculated by using an ELISA assay and the expression of signalling proteins was analysed by Western Blotting using phospho-specific and total antibodies. Additionally, the antioxidant Oxiprovin was used to investigate the quantity of ROS production in TNF-α-induced muscle atrophy. Results and Discussion: Incubation of L6 myotubes with increasing concentrations of recombinant TNF-α revealed that the lower concentrations of TNF-α used were not toxic to the cells but data analysis of cell death showed that 10 ng/ml TNF-α induced apoptosis and necrosis. Long-term treatment with TNF-α resulted in an increase in the upregulation of TNF- α receptors, specifically TNF-R1. The transcription factors NF-κB and FKHR were rapidly activated thus resulting in the induction of the ubiquitin-proteosome pathway. Activation of this pathway produced significant increases in the expression of E3 ubiquitin ligases MuRF-1 and MAFbx. Muscle fibre diameter appeared to have decreased with increasing TNF-α concentrations in part due to the suppressed activity of the PI3-K/Akt pathway as well as significant reductions in differentiation markers. Western blot analysis also showed that certain MAPKs are activated in response to TNF-α. No profound changes were observed with ROS production. Finally, the use Oxiprovin significantly lowered cell viability and ROS production. These findings suggest that TNF-α may elicit strong catabolic effects on L6 myotubes in a dose and time dependent manner. Conclusion: These observations suggest that TNF-α might have beneficial effects in skeletal muscle in certain circumstances. This beneficial effect however is limited by several aspects which include the concentration of TNF-α, cell type, time of exposure, culture conditions, state of the cell (disturbed or normal) and the cells stage of differentiation. The effect of TNF-α can be positive or negative depending on the concentration and time points analysed. This action is mediated by various signal transduction pathways that are thought to cooperate with each other. More understanding of these pathways as well as their subsequent upstream and downstream constituents is obligatory to clarify the central mechanism/s that control physiological and pathophysiological effects of TNF-α in skeletal muscle.