C5b-9 dimer: isolation from complement lysed cells and ultrastructural identification with complement-dependent membrane lesions.

The membrane attack complex (MAC) of complement was extracted from the membranes of cells lysed by human complement and its properties were compared with those of the fluid phase complex SC5b-9. Upon sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunochemical analysis, the two isolated complexes had identical subunit compositions, except that the MAC lacked the S-protein. The sedimentation coefficient and molecular weight of the extracted and isolated MAC were, respectively, 33.5 S and 1.7 x 10(6) daltons, compared to 23 S and 1.0 x 10(6) dalton for SC5b-9. Because the molecular weight of the MAC is approximately two times greater than that of C5b-0 (800,000 daltons), the MAC is considered the dimer of C5b-9. Under specified conditions, the 33.5 S dimer could be converted to the 23 S monomer without dissociation of subunits. The MAC had the electron microscopic appearance and dimensions that are characteristic for the complement produced ultrastructural membrane lesions. SC5b-9 had a different ultrastructure that is dissimilar to the morphology of the lesions. The isolated MAC could be reincorporated into phospholipid bilayers and assumed on the surface of the resultant lipid vesicles the orientation and appearance of typical complement lesions.

Structural changes in the freeze-fractured sarcolemma of ischemic myocardium.

Ultrastructural alterations in the sarcolemma of ischemic myocardium were studied with the freeze-fracture technique. In normal myocardial sarcolemma, the P fracture face contained many intramembranous particles which were randomly distributed, while the E fracture face had few intramembranous particles; no structural abnormalities were seen within the lipid bilayer on either face. Myocardium ischemic for 45 minutes displayed no, or only slight, aggregation of intramembranous particles, but upon reperfusion for 5 to 20 minutes, the particles became significantly aggregated in the P face. Scattered nicks within the lipid bilayer were observed on both fracture faces. Intramembranous particles were similarly aggregated in myocardium ischemic for 2 hours; however, the number of nicks were greatly increased on the P and E fracture faces. These structural alterations, which were undetected in thin sections, are likely to be associated with altered function in the sarcolemma of ischemic myocardium.

Detection of terminal transferase in paraffin sections with the immunoperoxidase technique.

Terminal deoxynucleotidyl transferase (TdT) is an early T-cell differentiation marker in a number of species, including man. We have demonstrated TdT in the nuclei of cortical thymocytes in paraffin-embedded sections of calf, rat, and human thymus by indirect immunoperoxidase techniques. In addition, these techniques have been used to verify and extend enzyme assay results by detecting TdT in blast cells from 10 patients with convoluted T-cell lymphoma/leukemia, 1 patient with acute granulocytic leukemia, 1 patient with chronic granulocytic leukemia in blast crisis, and 1 patient with non-T non-B acute lymphocytic leukemia.