Muscle atrophy

Atrophy Atrophy is a wasting or decrease in size of a bodily organ, tissue, or part owing to disease, injury, or lack of use. You may have heard this term used in reference to accident or paralysis victims "his muscles atrophied because of nonuse." Exposure to certain chemicals can cause internal organs to degrade, weaken and decrease in size, particularly with chronic (long-term) exposure. 

ALS is a disorder of the motor neurons and the cortical neurons that provide their input. The disorder is characterized by rapidly progressive weakness and muscle atrophy. Most affected patients die of respiratory compromise and pneumonia after 2 to 3 years. There is prominent loss of motor neurons in the spinal cord and brainstem although the oculomotor neurons are spared. Large pyramidal motor neurons in layer V of motor cortex, which are the origin of the descending corticospinal tracts, are also lost. 

Androgens act via the AR and play an important role in the development and differentiation of the male sexual organ. Furthermore, they are involved in several diseases, the most important being partial and complete androgen insensitivity syndrome (AIS formerly known as the testicular feminization syndrome), spinal and bulbar muscle atrophy (SBMA Kennedy s disease), and the neoplastic transformation of the prostate. The two natural occurring androgens are testosterone (T) and the... 

Biopsy findings show disseminated muscle fiber atrophy which is confined to type 2 fibers, in many instances with type 2B (glycolytic) fibers most affected (Figure 23). Muscle necrosis is not seen, though at ultrastructural level focal myofibrillar disruption and myofilament loss may be evident. The muscle atrophy seems to be due to decreased protein synthesis, and at high doses, to increased catabolism. The reason for the selective effect on phasic, glycolytic fibers is not clear since, although steroids interfere with carbohydrate metabolism and oxidative capacity, there seems to be no overall effect on ATP levels. Nevertheless it has been... 

Insulin is a powerful anabolic hormone but it is unlikely that insulin deficiency causes skeletal muscle atrophy by direct action on muscle fibers (as opposed to neurogenic atrophy) except in chronic untreated cases. There is however a close parallel between the catabolic states induced by glucocorticoid excess and by insulin deficiency. Moreover, impaired insulin action is implicated in other endocrine myopathies as a contributory cause of muscle wasting. Both acromegaly and thyrotoxicosis are associated with insulin resistance due to a postreceptor defect, and secondary hyperparathyroidism due to hypophosphatemia also gives rise to insulin insensitivity. 

Joint examination may reveal local tenderness, bony proliferation, soft tissue swelling, crepitus, muscle atrophy, limited motion with passive/active movement, and effusion. 

Motor neuron disease is characterized clinically by weakness, muscle atrophy and spasticity 732... 

Motor neuron disease is characterized clinically by weakness, muscle atrophy and spasticity. This illness, often termed Lou Gehrig s disease in the United States, is the most common adult-onset form of MND with a prevalence of approximately 2-3 per 100,000 people [1-3,10, 25, 28]. Each year in the United States, in excess of 5,000 people are diagnosed with ALS. In parts of the United Kingdom, 1 in =500 deaths are attributed to some form of MND. The principal clinical signs of ALS include progressive limb weakness, which may be symmetrical or asymmetrical atrophy of appendicular, bulbar and respiratory muscles and spasticity [1,2,26,28]. The paralysis/muscle atrophy and spasticity are the result of degeneration of motor neurons in the spinal cord/brain stem and motor cortex respectively. The onset of this illness is typically in the fifth or sixth decade of life affected individuals usually... 

Rosser, B.W.C. and J.C. George. 1986. Molt-induced muscle atrophy decreases the zinc content of the pectoralis of the giant Canada goose (Branta canadensis maxima). Experientia 42 549-550. 

As we grow older our muscle strength diminishes and the risk of developing sarcopenia increases. The meaning of the word sarcopenia is an abnormal decline in muscle strength and mass. Another word is muscle atrophy. Between early middle age and older age the mean decrease is 50% of muscle mass. Another way to calculate the loss of muscle mass is that over 50 years of age 1-2% of muscle tissue mass vanishes yearly. Between 50 and 70 years of age almost 15% of muscle strength per 10 years disappears. The resulting disability in older persons with sarcopenia has been calculated to cost approximately 900 dollars per person and year. The yearly total of healthcare expenditures for sarcopenia in the United States is estimated at 18-20 billions (Janssen et al. 2004). 

Drugs that increase sedation and give muscle relaxation can have a negative effect on muscle strength and the ability to maintain physical activity, for example, benzodiazepines and other tranquilizers. Corticosteroids have a well known side effect on muscle tissue that leads to muscle atrophy and increases with the dosage. 

In prolonged space flight, besides the obvious hazards of meteors, rocky debris, and radiation, astronauts will have to deal with muscle atrophy brought on by weighdessness therefore, when they return to Earth, they face a protracted period of weight training to rebuild their strength. 

Musculoskeletal Effects. Muscle wasting and atrophy have been reported in humans occupationally exposed to -hexane (Yamamura 1969). These effects occurred in individuals with severe neurotoxicity. Muscle atrophy is a common finding after intermediate-duration inhalation exposure to n-hcxanc in experimental animals. This atrophy is secondary to i -hexane-induccd neurotoxicity which results in... 

Bodine, S. C., et al., Identification of ubiquitin ligases required for skeletal muscle atrophy. Science, 2001, 294(5547), 1704-8. 

SBMA In addition to HD, NaBu has also been reported to be effective in treating spinal and bulbar muscular atrophy (SBMA) (Minamiyama et al, 2004), an inheritable motorneuron disease caused by an expanded polyglutamine-repeat within the androgen receptor. SBMA is associated with motorneuron loss in the spinal cord and brain stem as well as a sub-clinical loss of sensory neurons in the dorsal root ganglia resulting in skeletal muscle atrophy and weakness (Sobue et al, 1989 ... 

Amyotrophic lateral sclerosis (ALS) is a disease of the neurons that control muscle movement (motor neurons). Degeneration of neurons causes muscle atrophy eventually impairing the movement of people afflicted with the disease. 

In inhalation studies conducted by the National Toxicology Program, acute, subchronic, and chronic effects of ethyl bromide were examined in mice and rats. All mice and three of five female rats died before the end of a 4-hour exposure to 5000 ppm rats and mice exposed to 2 000 ppm 6 hours/day died before the end of 14-day studies. In 14-week studies, 1600 ppm was lethal to some animals and caused compound-related lesions including muscle atrophy and atrophy of the testis and uterus thought to be secondary to body weight loss rats also had minimal to moderate multifocal mineralization in the cerebellum and minimal-to-severe hemosiderosis of the spleen. 

In adults, symptoms Include constipation, loss of appetite, nausea, peripheral neuropathy, weakness, muscle atrophy, and fatigue. 

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