Gingival squamous cell carcinoma in a patient with chronic graft-versus-host disease.

This article describes a gingival squamous cell carcinoma that developed in a 21-year-old woman who received a bone marrow transplant at the age of 16 from her human leukocyte antigen-identical sister as treatment for severe aplastic anemia. Thirty days after transplantation, she presented with cutaneous erythema as a result of acute graft-versus-host disease, and this subsequently evolved into chronic graft-versus-host disease. A lichenoid white plaque of the gingiva developed shortly thereafter, and it began to increase in size rapidly 4 years posttransplantation. Biopsy indicated squamous cell carcinoma arising in this region, apparently associated with chronic graft-versus-host disease. Few reports have described a secondary solid malignancy involving the oral cavity of young adults after bone marrow transplantation.

Distribution of connectin (titin), nebulin and alpha-actinin at myotendinous junctions of chicken pectoralis muscles: an immunofluorescence and immunoelectron microscopic study.

The distribution of connectin (titin), nebulin and alpha-actinin in the areas of myotendinous junctions of chicken pectoralis muscles was examined by immunocytochemical methods. Staining with antibodies against connectin (4C9, SM1 and P1200) and nebulin formed 'doublets' flanking nonterminal Z-bands; near the end of muscle fibres 'singlets' were seen within the terminal sarcomere on the side adjacent to the terminal Z-bands. The apical regions of muscle processes, where no myosin filaments are present although actin filaments exist, were reactive with anti-nebulin but not with anti-connectin. Antibodies against pectoralis (skeletal muscle type) alpha-actinin stained non terminal Z-bands and that against gizzard (smooth muscle type) the sarcolemma. Terminal Z-bands were unreactive with both of these antibodies. These findings indicate that, although terminal and nonterminal Z-bands differ in their molecular composition, connectin and nebulin filaments appear to link myosin and actin filaments, respectively, to both Z-band types.

Distribution of connectin (titin) and transverse tubules at myotendinous junctions.

The ends of muscle fibers form many longitudinal projections which are further divided into numerous processes and attach to the collagen fibrils of tendons to form myotendinous junctions (MTJs). Immunocytochemical and electron microscopic observations on pectoralis muscles of the chicken revealed the presence of an elastic filamentous protein, connectin (titin), within the terminal sarcomere on the side adjacent to the terminal Z bands, and the absence of connectin and myosin and the presence of actin at the apical sarcoplasmic region of MTJ processes between the terminal Z band and the MTJ sarcolemma. Intermediate voltage electron microscopy showed that T tubules in the terminal sarcomere were absent at the level of the A-I junction on the MTJ side in the rat vastus intermedius, and at the level of the terminal Z band or under the MTJ subsarcolemmal densities in the chicken pectoralis.