A study of platelet protein phosphorylation in Duchenne muscular dystrophy. Further evidence against the generalised membrane defect theory

Impaired primary hemostasis with normal platelet function in Duchenne muscular dystrophy during highly-invasive spinal surgery

A defective, normal or enhanced hemostasis has been reported in Duchenne muscular dystrophy (DMD). A retrospective analysis of intra-and postoperative (up to 36 h) estimated blood losses was performed in 156 patients undergoing spinal surgery for: DMD (n = 31), idiopathic scoliosis (IS) (n = 70), poliomyelitis (n = 10), cerebral palsy (CP) (n = 28), spinal muscular atrophy (SMA) (n = 17). Platelet aggregation and bleeding times were also investigated in DMD patients. Immunohistochemistry for dystrophin was performed in platelets, megakaryocytes and blood vessels of normal tissues. DMD patients showed significantly higher intraoperative estimated blood losses (DMD: 3495+/-890 ml; IS: 2269+/-804 ml; poliomyelitis: 2582+/-1252 ml; CP: 2071+/-683 ml; SMA: 2464+/-806 ml; P < 0.05), while postoperative blood losses were similar among different groups. Higher estimated blood losses in DMD were independent of the duration of surgery, body weight, gender, age, vertebral levels or preoperative Cobb angle. DMD children had significantly prolonged bleeding times, but retained normal platelet function. From control samples dystrophin was expressed in vascular smooth muscle cells, but not in platelets. DMD appears to be characterized by immediate bleeding during highly-invasive surgery and increased bleeding time without platelet abnormalities. Considering dystrophin expression in normal vascular smooth muscle cells, these results altogether suggest a selective defect of primary hemostasis in DMD, likely to be due to impaired vessel reactivity.

Familial myopathy associated with thrombocytopenia: a clinical and histomorphometric study

We describe an unusual vacuolar myopathy with tubular aggregates in a mother and son from a family presenting with a slowly progressive, predominantly limb girdle, weakness and distal upper limb weakness in association with reduced blood clotting ability. To our knowledge this is the first report of a familial clinical defect of both muscle and platelets in the same individuals. The possibility that the primary defect may be due to an abnormality of the tubular intramembranous systems in muscle cells and platelet precursors is discussed.

Vascular endothelial cell injury and platelet embolism in Duchenne muscular dystrophy at the preclinical stage

Blood vessels in muscle biopsy specimens from 4 Duchenne muscular dystrophy (DMD) patients (including 3 at the preclinical stage) were examined by electron microscopy and compared with those in non-diagnostic biopsy specimens from age-matched controls and cases of other childhood neuromuscular disorders. The most striking feature was the blister-like swelling of vascular endothelial cells in the biopsied muscle specimens from the 3 preclinical stage DMD patients, which was observed in 23-39% of the small blood vessels examined. Other noticeable features in the preclinical DMD patients were: (1) replication of the basement membrane, there being more than 3 layers in 30% of the capillaries; (2) many degenerating and regenerating capillaries; and (3) platelet adhesion and aggregation in small blood vessels including small arteries and veins. Morphometric analysis showed that the capillary and endothelial cell areas were much greater in the preclinical DMD patients than in the controls or the cases of the other neuromuscular disorders. These phenomena strongly suggest an as yet undetermined process in blood vessels in preclinical DMD.

Skeletal muscle phosphoproteins: muscle-specific basal and cAMP-dependent phosphoprotein profiles

To determine whether or not phosphorylation of skeletal muscle proteins is related to functional specialization of individual muscles, we examined the distribution of phosphoproteins in skeletal muscles with different functional properties. Protein phosphorylation was carried out using [gamma-32P]ATP and employing endogenous protein kinases present in skeletal muscle homogenates. Phosphoprotein bands were separated by polyacrylamide gel electrophoresis. We found distinct cAMP-stimulated and basal phosphoprotein patterns in each contraction type; indicating that the phosphoprotein profile is related to functional characteristics. Muscle-specific, cAMP-dependent phosphoproteins may permit coordinate short-term alterations in twitch characteristics of skeletal muscle fibers in response to circulating hormones or other mediators.