title: Muscle function in a patient with Brody's disease.
abstract: Adductor pollicis muscle function of a 21-year-old man with genetically confirmed Brody's disease (sarcoplasmic reticulum [SR] -Ca2+ATPase deficiency) was investigated to study the possible effects of reduced SR-Ca2+ATPase activity on muscle relaxation and force production. Following maximal electrical activation of the ulnar nerve, tetanic muscle half-relaxation time was greater in the patient (246 +/- 10 ms) than control subjects (97 +/- 4 ms, n = 8). During repetitive activation, there was a similar decline in maximal shortening velocity in the patient and controls, indicating a comparable reduction in cross-bridge cycling rate. The finding that the slowing of relaxation was greater in the patient (329 ms versus 138 +/- 20 ms) suggests that there was a further reduction of SR-Ca2+ATPase activity in the patient's muscle during fatigue. Following a voluntary contraction, involuntary activity of the antagonist muscles facilitated force decline and masked the impaired relaxation in the patient. This antagonist-induced relaxation indicates that it might be difficult to establish impaired muscle relaxation with voluntary contractions.
authors.affiliation: Institute for Fundamental and Clinical Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands.
authors.forename: C J
authors.initials: CJ
authors.lastname: De Ruiter
authors.forename: R A
authors.initials: RA
authors.lastname: Wevers
authors.forename: B G
authors.initials: BG
authors.lastname: Van Engelen
authors.forename: P W
authors.initials: PW
authors.lastname: Verdijk
authors.forename: A
authors.initials: A
authors.lastname: De Haan
mesh_terms: D000328:Adult; D000252:Calcium-Transporting ATPases / Q000172:deficiency / Q000235:genetics*; D004576:Electromyography; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D009135:Muscular Diseases / Q000201:enzymology / Q000235:genetics*; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*
chemical_list: D000252:Calcium-Transporting ATPases