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Lookup NU author(s): Dr Michael Cullen
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There is increasing evidence that γ-sarcoglycan is absent and other sarcoglycans are reduced in patients with the limb-girdle muscular dystrophy type 2C (LGMD2C) form of severe childhood autosomal recessive muscular dystrophy. In the present investigation, we combined microspectrofluorimetry and electron microscopy techniques to investigate the physiological function and the ultrastructure of control and LGMD2C myotubes. Results obtained from Ca2+ measurements showed that the resting level of the cytosolic free calcium ([Ca2+](i)) in control myotubes was 73 ± 3.4 nmol/l (mean ± SE, n = 35) and in LGMD2C myotubes was 69 ± 4 nmol/l (n = 44). Carbachol (CCh, 10 μmol/l) induced a 335 ± 10 nmol/l (n = 8) rise in [Ca2+](i) in control myotubes and 531.9 ± 32 nmol/l (n = 23) in LGMD2C myotubes. Similarly, elevations of [Ca2+](i) by 35 mmol/l K+ were 324 ± 32 nmol/l (n = 8) in control myotubes and 442.8 ± 24 nmol/l (n = 22) in LGMD2C myotubes. Caffeine (10 mmol/l) activated similar [Ca2+](i) peaks in control and LGMD2C myotubes but induced a biphasic response in LGMD2C in four out of 12 myotubes and only a monophasic response in control myotubes. The ultrastructural results showed that the plasma membrane was abnormally indented and convoluted in both the LGMD2C biopsy and the LGMD2C cultured myotubes. It is suggested that the reduction in components of the dystrophin-glycoprotein complex results in the instability and an increase in the surface area of the plasma membrane, which may result in a higher population of Ca2+ channels in the LGMD2C myotubes.
Author(s): Hassoni AA, Cullen MJ
Publication type: Article
Publication status: Published
Journal: Neuropathology and Applied Neurobiology
Year: 1999
Volume: 25
Issue: 3
Pages: 244-253
Print publication date: 01/06/1999
ISSN (print): 0305-1846
ISSN (electronic): 1365-2990
Publisher: Wiley-Blackwell Publishing Ltd.
URL: http://dx.doi.org/10.1046/j.1365-2990.1999.00169.x
DOI: 10.1046/j.1365-2990.1999.00169.x
PubMed id: 10417666
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