Objective. To identify the morphology of a mineral-forming fraction of adult porcine hyaline articular cartilage digest and characterize the mineral it forms.Methods. Electron microscopy, Fourier transform infrared (FTIR) spectroscopy, x-ray microanalysis, compensated polarized light microscopy, and biochemical studies including 14C-labeled UDPG pyrophosphohydrolase radiometric assay.Results. plate cartilage matrix vesicles and formed mineral after only 24 hours in physiologic salt solution containing 1 mM ATP. The mineral contained inorganic pyrophosphate, 95% of which derived from ATP, and phosphate, 93% of which derived from inorganic phosphate in the medium. The FTIR spectrum of this mineral closely resembled the spectrum of standard calcium pyrophosphate dihydrate (CPPD) crystals. Compensated polarized light microscopy showed positively birefringent, rod-shaped crystals morphologically identical to CPPD. Ca:P ratios, defined by energy-dispersive microanalysis, were also consistent with CPPD.Conclusion. The articular cartilage vesicle fraction of porcine hyaline cartilage is capable of generating mineral that strongly resembles CPPD.Calcium pyrophosphate dihydrate (CPPD) and basic calcium phosphate crystals occur in articular cartilage and synovial fluid of patients with diverse arthropathies (1-3). Both crystal types may initiate or amplify articular tissue destruction ( 4 3 , but the source of these crystals has not been precisely identified. A sedimentable fraction of adult porcine articular cartilage digest which supports ATP-enhanced calcium deposition under physiologic ionic conditions has been demonstrated (6). We sought to characterize the morphology of this fraction by electron microscopy for comparison with a similar mineralizing fraction of epiphyseal growth plate matrix vesicles (7,8). We then characterized the mineral produced by this fraction, comparing it with crystals observed in human articular diseases. We report that a vesicle-containing fraction of articular cartilage digest produces both calcium phosphate and calcium pyrophosphate mineral in

The BC-1 cell line, derived from a body cavity-based, B-cell lymphoma, is dually infected with Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV). In these studies, the relationships between these two gammaherpesviruses and BC-1 cells were characterized and compared. Single-cell cloning experiments suggested that all BC-1 cells contain both genomes. In more than 98% of cells, both viruses were latent. The two viruses could be differentially induced into their lytic cycles by chemicals. EBV was activated into DNA replication and late-gene expression by the phorbol ester tetradecanoyl phorbol acetate (TPA). KSHV was induced into DNA replication and late-gene expression by n-butyrate. Amplification of both EBV and KSHV DNAs was inhibited by phosphonoacetic acid. Induction of the KSHV lytic cycle by n-butyrate was accompanied by the disappearance of host-cell ␤-actin mRNA. Induction of EBV by TPA was not accompanied by such an effect on host-cell gene expression. Induction of the KSHV lytic cycle by n-butyrate was associated with the expression of several novel polypeptides. Recognition of one of these, p40, served as the basis of development of an assay for antibodies to KSHV in the sera of infected patients. BC-1 cells released infectious EBV; however, there was no evidence for the release of encapsidated KSHV genomes by BC-1 cells, even though n-butyratetreated cells contained numerous intranuclear nucleocapsids. The differential inducibility of these two herpesviruses in the same cell line points to the importance of viral factors in the switch from latency to lytic cycle.

Calcium crystals in osteoarthritic (OA) joints promote enzymatic degradation of articular tissues. Matrix vesicles provide a nidus for calcium crystal formation in chick epiphyseal and mature porcine articular cartilage. In order to examine a potential role for matrix vesicles from OA cartilage in generating pathologic crystals, we sought to determine whether vesicles derived from human OA cartilage (OAMV) could mineralize; and we characterized the resultant mineral species. OAMV were isolated and examined for alkaline phosphatase (AP) and nucleoside triphosphate pyrophosphohydrolase (NTPPPH) activity. OAMV ATP-dependent and independent mineralization were measured in a radiometric biomineralization assay, and newly formed OAMV crystals were examined using Fourier transform infrared spectroscopy (FTIR) and compensated polarized light microscopy. The mean specific activity of OAMV AP was approximately 6 times higher and NTPPPH activity 11 times lower than that of previously characterized, mature, porcine, articular cartilage vesicles. OAMV progressively precipitated 45Ca over time both in the presence and absence of ATP. The FTIR spectra of mineral formed in ATP-dependent assays most closely resembled the standard spectrum for calcium pyrophosphate dihydrate (CPPD). The FTIR spectra of OAMV mineral formed in the absence of ATP closely resembled apatite. These data support the hypothesis that OAMV may form mineral phases of two key crystals found in degenerating cartilage and provide further evidence for the role of matrix vesicles in pathologic articular cartilage biomineralization.