WORK PHYSIOLOGY IN HEALTH AND DISEASE.
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Excitatory amino acids which promote the survival of cerebellar granule cells in culture, also promote the expression of the survival of motor neuron (SMN) protein. Immunolocalization studies using SMN monoclonal antibody showed that SMN is decreased in cultures grown in low K+ or chemically defined medium with respect to cultures grown in high K+ medium and that an increase of SMN can be induced by treatment of low K+ cultures with glutamate or N-methyl-D-aspartate.
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Gastrointestinal motility is the function of gastrointestinal smooth muscle. It is controlled by both the intrinsic and extrinsic nerves of the gastrointestinal tract and, to a lesser degree, the gastrointestinal hormones. Therefore, any abnormality of the above factors, theoretically, can cause gastrointestinal dysmotility. In a clinical situation, commonly seen is gastrointestinal dysmotility caused by either smooth muscle or intrinsic and extrinsic nerves dysfunction. Diseases that cause smooth muscle dysfunction include familial visceral myopathies, nonfamilial visceral myopathies, collagen disease, muscular dystrophies, amyloidosis, thyroid disease, and so on. Diseases that cause enteric nerve dysfunction include familial visceral neuropathies, nonfamilial visceral neuropathies, diabetes mellitus, Chagas' disease, ganglioneuromatosis of the intestine, visceral neuropathy of carcinomatosis, Parkinson's disease, and so on. The patients with neuromuscular disease of the gastrointestinal tract have a wide range of clinical manifestations regardless of the underlying cause. At one end of the spectrum, the patients may be asymptomatic, and at the other end of the spectrum, the patients may have functional obstruction of the gastrointestinal tract. Plain abdominal x-rays, upper gastrointestinal (UGI) and small bowel x-rays, enteroclysis, barium enema, and manometric studies are useful for the work-up of these patients. Enteroclysis is especially helpful in ruling out mechanical obstruction of the small intestine in patients with chronic intestinal pseudo-obstruction. Treatment is mainly symptomatic and supportive. There is no effective drug to improve gastrointestinal motility. Surgery may be helpful in selected cases of severe gastrointestinal dysmotility.
One hundred and sixty-two patients with Duchenne muscular dystrophy (DMD) were followed over a 10-yr period to provide a profile of impairment and disability. The median height and weight of DMD boys were normally distributed before ages 9-10, but during the second decade height was markedly reduced, and weight was no longer normally distributed. Younger boys gained more weight than normals, whereas older individuals actually showed weight loss. Manual muscle test (MMT) measurements showed loss of strength in a fairly linear fashion from ages 5-13 yr, -0.25 MMT units per year. Upper extremity muscles were stronger than lower extremity muscles, proximal muscle groups were weaker than distal muscle groups, and extensor muscles were weaker than flexor muscles. There was no side dominance. There was a change in the rate of strength loss at 14-15 yr, and the decline slowed to only -0.06 MMT units per year. Although MMT and quantitative strength measurement profiles were similar, the latter were far more sensitive. In general, by the time strength declined to MMT grade 4, isometrically measured strength was 40-50% of normal control values. Joint contractures were rare before age 9, increased in frequency and severity with age, and were present in most individuals older than 13. Lower extremity contractures were strongly related to onset of wheelchair reliance, but there was no association between muscle imbalance around a joint. The prevalence of scoliosis increased between ages 11 and 16, with about 50% of the boys acquiring scoliosis between ages 12 and 15, corresponding to the onset of the adolescent growth spurt. Wheelchair reliance and scoliosis were both age-related. Percent predicted forced vital capacity declined at different yearly rates: ages 7-10, -0.3%; ages 10-20, -8.5%; after age 20, -6.2%. There was a direct relationship between percent predicted FVC and MMT scores. Decreased airway pressures, especially maximal expiratory pressure, appeared earlier than reductions in FVC but followed the same pattern. Thirty percent of the DMD boys had a history of respiratory complications, and the frequency increased with age. Spine deformity did not have a significant additive effect on the age-related decrement in pulmonary function. There was a high occurrence (79%) of abnormal electrocardiograms with age-related progression of some abnormalities, but only 30% of the patients had a history of cardiovascular complications. Functional level grades and timed motor performance measurements had a nonlinear relationship with strength and age.(ABSTRACT TRUNCATED AT 400 WORDS)
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It has been demonstrated that nuclear lamins are important proteins in maintaining cellular as well as nuclear integrity, and in maintaining chromatin organization in the nucleus. Moreover, there is growing evidence that lamins play a prominent role in transcriptional control. The family of laminopathies is a fast-growing group of diseases caused by abnormalities in the structure or processing of the lamin A/C (LMNA) gene. Mutations or incorrect processing cause more than a dozen different inherited diseases, ranging from striated muscular diseases, via fat- and peripheral nerve cell diseases, to progeria. This broad spectrum of diseases can only be explained if the responsible A-type lamin proteins perform multiple functions in normal cells. This review gives an overview of current knowledge on lamin structure and function and all known diseases associated with LMNA abnormalities. Based on the knowledge of the different functions of A-type lamins and associated proteins, explanations for the observed phenotypes are postulated. It is concluded that lamins seem to be key players in, among others, controlling the process of cellular ageing, since disturbance in lamin protein structure gives rise to several forms of premature ageing.