Metabolic and endocrine disease and arthritis.

Many metabolic and endocrine disorders have effects on the musculoskeletal system, either due to primary changes in bone and collagen or resulting in secondary arthritic and bone changes. Disorders of ossification include heterotopic ossification, diffuse idiopathic skeletal hyperostosis (DISH), and the spondyloarthropathies. The early stages of heterotopic ossification have been analyzed using immunohistochemical techniques to trace the distribution of noncollagenous proteins. Several radiographic features of DISH and ankylosing spondylitis were discussed, including rib hyperostosis and syndesmophytes. Hypertrophic osteoarthropathy with associated arthritis was described in seven patients with hepatic failure and transplantation. Remarkable improvement in arthritis followed transplantation. The inverse relationship between osteoarthritis and osteoporosis continues to be studied, and it has been hypothesized that genetics play a major role in determining the rate of bone turnover, resulting in, for example, "bone formers." Both growth hormone excess and deficiency lead to changes in the incidence of osteoarthritis. Finally, one study documented the improved outcome in joint replacements in hemophiliac patients.

Synthesis of complement component C5 by human B and T lymphoblastoid cell lines.

Human B and T lymphoblastoid cell lines were shown to synthesize C5. C5 synthesis was quantitated with an enzyme-linked immunosorbent assay (ELISA) that utilized a pool of C5-specific monoclonal antibodies (mAbs). Some level of C5 synthesis was detected in all eight of the B and T cell lines examined. In three of the cell lines, C5 was detected in both culture supernatants and whole cell detergent lysates, whereas in the other five cell lines, C5 was detected only in the cell lysates. Lymphoblastoid cells with both distributions of C5 were shown to synthesize a messenger RNA that was similar in size to the C5 mRNA expressed by the HepG2 hepatoma cell line. Estimates of the concentration of the C5 transcript in poly(A)+ RNA from lymphoblastoid and HepG2 cells suggested that C5 mRNA levels in the lymphoblastoid cell lines were comparable and about one-tenth of the levels in HepG2 cells. Lymphoblastoid C5, isolated by immunoaffinity chromatography from the supernatants of 35S-labeled cultures, had the same subunit composition as plasma-derived C5, but had an alpha subunit of slightly smaller relative mass.