Biochemical characterization of recombinant factor IX

Mature human factor IX is a 55,000-d glycoprotein with a modular domain structure and numerous posttranslational modifications. A recombinant form of human factor IX (rFIX) has been produced from a Chinese hamster ovary cell line that was engineered for high-level protein processing and expression. To ensure that the recombinant molecule contains the requisite structural and functional features of the plasma-derived form, rFIX was subjected to detailed biochemical and biophysical characterization. The laboratory studies showed that the posttranslational modifications and primary, secondary, and tertiary structures of rFIX were similar to those of plasma-derived factor IX (pdFIX). In addition, rFIX displayed a high degree of purity and a product release specification for specific activity that is > or = 200 IU/mg.

A safe procedure for transporting bone-marrow for purging in a central laboratory

A central facility for ex vivo removal of neuroblastoma cells from bone marrow, to be used for autologous reinfusion after myeloablative treatment, was established and a study was designed to compare the survival time and the rate of bone marrow engraftment between local marrows obtained and processed at the University of Florida (UF) and marrow transported for purging from out of state, participating Pediatric Oncology Group (FOG) centers. Marrow harvest from patients either at UF or at participating centers, was done under a similar protocol. Marrows from participating centers were transported by air, to UF and purged using the immunomagnetic technique. The purged marrows were returned in liquid nitrogen for reinfusion before myeloablative treatment. Marrows were purged between 1985 to 1992 from 169 POG patients, of whom 164 were evaluable for this study (UF 29 and 135 transported). Statistical analysis of survival time and engraftment rate found no significant differences in survival time (p=0.2463) and engraftment rate (0.3259) between marrows shipped from other institutions to marrows harvested and processed at UF.

Expression of N-myc, c-myc, and MDR-1 proteins in newly established neuroblastoma cell lines: a study by immunofluorescence staining and flow cytometry

A methodology for rapid isolation of neuroblastoma cells from marrow with metastatic neuroblastoma cells was developed using a cocktail of five antibodies and magnetic microspheres coated with secondary antibodies. Cells bound to microspheres were released by brief exposure to chymopapain, followed by repeated culture of released cells in serum-supplemented Dulbecco's modified Eagle's medium and selection for adherent cells. Using this methodology, over 35 primary cell lines were obtained free of contaminating normal cells. Detailed analyses of over 14 cell lines revealed gross differences in cell phenotype, size, morphology development of neurite processes, and doubling time (40 to 80 h). All cell lines expressed the M(r) 145,000 neurofilament, and a few expressed the M(r) 200,000 neurofilament, with very little or no expression of the M(r) 68,000 neurofilament. Eight % of all cells lines had near-diploid DNA content. High expression of the MDR-1 protein was detected in six of the 22 cell lines tested. Great heterogeneity was observed in the expression of N-myc oncoprotein, with ten of 13 patients overexpressing the protein. c-myc oncoprotein was also expressed in all cell lines; however, the level of expression was 4- to 10-fold lower than the N-myc oncoprotein. Localization studies of c-myc and N-myc oncoproteins on the level of light microscopy and electron microscopy revealed exclusive nuclear localization of c-myc, whereas N-myc was localized to the nucleus and to the cytoplasm.