Our enzyme-linked immunosorbent assay (ELISA) for measuring human platelet-derived growth factor (PDGF) detects nanogram quantities (ranging from 0.007 to 16 ng/100 microL) in purified PDGF standards. This assay is sensitive enough for studying plasma and urine. The range in normal volunteers was 0.6 to 2.3 micrograms/L for platelet-poor plasma and 1.4 to 3.3 micrograms/L for urine. We determined PDGF levels in the circulation (outside platelets) in patients with myeloproliferative diseases. Platelet-poor plasma and urine PDGF were significantly elevated in patients with myelofibrosis (6.2 +/- 2.0 micrograms/L for plasma; 7.8 +/- 2.4 micrograms/L for urine) and essential thrombocythemia (5.5 +/- 1.5 micrograms/L for plasma; 11.4 +/- 2.2 micrograms/L for urine), but not in patients with chronic myelogenous leukemia (2.1 +/- 0.4 micrograms/L for plasma; 2.8 +/- 1.2 micrograms/L for urine). Polycythemia vera produced an intermediate pattern: although plasma PDGF was within the normal range (2.1 +/- 0.2 micrograms/L), urine levels were increased (3.7 +/- 0.6 micrograms/L). These results show that PDGF is increased in the circulation in some but not all myeloproliferative diseases, and suggest that this is due to abnormal in vivo release from either megakaryocytes in the bone marrow or circulating platelets.
A possible pathogenetic role of hepatitis C virus (HCV) infection in developing B-cell non-Hodgkin's lymphoma (NHL) has been hypothesized.' In this study, we evaluated the presence of monoclonal gammopathy (MG) in 198 outpatients with HCV-positive chronic liver disease (mean age 5 1.1 t-13.4 years; male/female: 118/80) compared to 54 outpatients with HBsAg-positive chronic liver disease (mean age 47.3 ? 12.8 years; male/female: 36/18). The groups were comparable concerning age, sex, and liver histology. MG was detected by immunoelectrophoresis (IFE; Beckman, Brea, CA). Serum cryoglobulins were also determined according to Brouet et al.' MG was found in 22/198 (1 1%) HCV-positive (6 multiple myeloma and 16 MC of undetermined significance) and in 0/54
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