Biomedical subjects
Publications and source records attributed to A Rotman.
Primaquin specifically inhibits mitochondrial function in yeast. Mutants resistant to primaquin have been isolated. Genetic analysis revealed that the expression of resistance in one of them was under the control of both a nuclear gene and a cytoplasmic factor (possibly a mitochondrial gene).
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The interaction of the cytoskeleton with plasma membranes may be mediated by vinculin, alpha-actinin and other proteins; alpha-actinin can interact specifically with model membranes only if they contain diacylglycerol and palmitic acid. On stimulation of platelets by thrombin, which leads to a reorganization of the cytoskeleton, diacylglycerol is produced rapidly, simultaneously with the disappearance of phosphatidylinositol. One important function of the diacylglycerol produced in platelets may be the activation of the Ca2+-and phospholipid-dependent protein kinase C. We show here that, in the presence of diacylglycerol and palmitic acid, a supramolecular complex between alpha-actinin and actin is formed in vitro. In the electron microscope, this complex displays substructures similar to those of microfilament bundles in vivo. Furthermore, such alpha-actinin/lipid complexes can also be formed in situ during the stimulation of blood platelet aggregation. Thus, alpha-actinin may be one of the proteins directly involved in structures connecting the cytoskeleton to cell membranes.
Platelet aggregation studies were performed in 22 adolescent girls with idiopathic scoliosis. Impaired ADP-induced platelet aggregation was found in washed platelets of the 22 patients with idiopathic scoliosis when compared with the controls (76.5% of control values; p less than 0.01). Furthermore, platelets from patients with progressive curves showed a greater degree of abnormality than platelets from those with nonprogressive curves, e.g., 57.6 +/- 22% of control values (p less than 0.001). No significant differences in aggregation could be detected when platelets were aggregated with the ionophore A-23187 in either the absence or the presence of calcium. Platelet aggregation studies in patients with other spinal deformities did not differ from the healthy controls. Because platelets share similar contractile proteins as muscles, the present study suggests that a muscle disorder may play an important pathogenic role in idiopathic scoliosis.