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G Osikowicz

Publications and source records attributed to G Osikowicz.

10 recordsLinked to original sources
PubMed1996

Two-stage procedure for evaluating interassay carryover on random-access instruments.

A two-stage statistical procedure based on Dunnett's multiple comparison procedures with a control has been developed for detecting interassay carryover biases on the Abbott AxSYM(TM) System, a random- and continuous-access immunoanalyzer. With this procedure, every potential source of interassay carryover can be tested and estimated. In minimizing required sample sizes, the first stage is used primarily to detect and eliminate from further testing the assay reagent sources that do not cause carryover biases and the assay sources that cause very large carryover biases. Retested more extensively in the second testing stage are the cases where the data from the first testing stage are insufficient for judgment. An example data set from the Abbott AxSYM Free T4 assay is used to illustrate the methodology.

Autoanalysis↗
PubMed1993

Abbott AxSYM random and continuous access immunoassay system for improved workflow in the clinical laboratory.

We describe a new clinical laboratory instrument, the Abbott AxSYM, which provides random- and continuous-access testing for immunoassays, 20 onboard reagents, primary tube sampling, and a throughput of 80 to 120 tests per hour. The AxSYM incorporates three separate analytical technologies for processing immunoassays: microparticle enzyme immunoassay, fluorescence polarization immunoassay, and a novel technology known as ion-capture immunoassay. The system incorporates both common and technology-specific subsystems controlled by a real-time software scheduling processor. Tests can be processed in one- or two-step sandwich or competitive formats, with variable pipetting steps, incubation periods, optical read formats, and wash sequences. Menu capabilities include tests for hepatitis, retrovirus, tumor markers, fertility markers, thyroid functions, and therapeutic drugs. The time to first result is approximately 15-25 min for most routine assays and < or = 15 min for stat assays (i.e., creatine kinase MB isoenzyme, human chorionic gonadotropin beta subunit, and therapeutic drugs). AxSYM assay performance for 23 assays was comparable with that of the Abbott IMx and TDx analyzers; specimen correlation data had correlation coefficients ranging from 0.97 to 0.99 and slopes ranging from 0.99 to 1.10. Within-run imprecision (CV) was 1.5% to 11.4%, with most assays (19 of 23) demonstrating CVs < or = 8.0%.

Autoanalysis↗
PubMed1984

Isolation and characterization of a urokinase-type plasminogen activator (Mr = 54,000) from cultured human endothelial cells indistinguishable from urinary urokinase.

A urokinase-type plasminogen activator secreted by subcultured normal human umbilical vein endothelial cells was purified and compared to urinary urokinase (Mr = 54,000). The enzyme was isolated from serum-free conditioned medium in the presence of 0.1% (v/v) Triton X-100 by p-aminobenzamidine-agarose affinity chromatography, followed by Sephacryl S-200 gel filtration, followed by immunoadsorption chromatography on affinity purified specific anti-urokinase IgG-Sepharose CL-4B. This plasminogen activator form was obtained from the culture medium with a yield of about 47% and specific activity of about 93,000 IU/mg of protein, and represented approximately 18% of the total multiple molecular plasminogen activator activity forms present in endothelial cell conditioned medium. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme showed a single band of plasminogen activator activity with an estimated molecular weight of about 54,000 that was completely inhibited by diisopropyl fluorophosphate (DFP) as well as a single band of radioactivity with similar molecular weight for both the isolated L-[4,5-3H]leucine and [3H]DFP-labeled enzyme. The radiolabeled protein focused as a single major band with a pI value of pH 8.5. The endothelial cell activator and urokinase appeared to be identical in terms of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, location of the [3H]DFP-labeled active site in the Mr = 33,000 heavy chain and [3H]DFP-labeled active site tryptic peptide, and two-dimensional 125I-labeled tryptic peptide maps. In quenching experiments of the fibrinolytic activities using affinity purified specific anti-urokinase IgG the endothelial cell-derived activator and urokinase appeared to be immunochemically identical, but unrelated to tissue plasminogen activator. These results indicate that the Mr = 54,000 urokinase-type plasminogen activator from cultured normal human endothelial cells is similar to, or identical with, Mr = 54,000 urinary urokinase.

Cells, Cultured↗
PubMed1983

Effect of hypoxia on the conversion of angiotensin I to II in cultured porcine pulmonary endothelial cells.

Earlier studies by other investigators have shown that acute exposure of cultured endothelial cells to hypoxic atmospheres inhibits the activity of the angiotensin converting enzyme in situ, resulting in severe but reversible depression of the rate of degradation of bradykinin. We exposed primary cultures of endothelial cells from the pulmonary artery of the pig to a range of hypoxic gas mixtures and measured the activity of the angiotensin converting enzyme in situ using angiotensin I as substrate. Each cell flask was exposed in random sequence to both hypoxic gas mixtures (PO2 29-69 torr) and room air for 40 min in Dulbecco's medium containing angiotensin I at concentrations of 1000 (N = 7), 500 (N = 8) or 100 ng/ml (N = 4). Angiotensin I disappearance rates and angiotensin II generation rates were linear. Recovery of immunoreactive peptide as either angiotensin I or II following 40 min of incubation was 86 +/- 17% (S.D.). The rate of increase in angiotensin II concentration in surface medium in room air experiments was 91 +/- 51 (S.D.) ng x ml-1 x hr-1. During hypoxia it was 85 +/- 42 ng x ml-1 x hr-1. The difference in rates was not significant by paired t analysis. The results of this study are consistent with earlier observations by the authors which suggest that hypoxia-induced depression of angiotensin I conversion in vivo is due to hemodynamic phenomena. Further studies are needed to clarify the role of cellular mechanisms in hypoxia-induced depression of angiotensin metabolism.

Angiotensin I↗
PubMed1981

Effects of chronic oral consumption of nicotine on the rabbit aortic endothelium.

New Zealand white rabbits (10) were administered daily doses of nicotine (2.4 mg/kg/day) in their drinking water for 25 weeks. Nicotine-treated rabbits were compared with control rabbits (10) in terms of blood serum biochemistry and lipid profiles, blood cells counts, changes in aortic endothelial cell morphologic characteristic and distribution, and vessel wall permeability (Evans blue dye uptake). Fasting serum levels of glucose, triglycerides, total cholesterol, and LDL-cholesterol were elevated in nicotine-treated rabbits. No significant differences (nicotine vs control) were seen in leukocyte, erythrocyte and platelet counts, or hematocrit and hemoglobin. Control and nicotine-treated rabbit aortas showed similar focal areas of increased Evans blue dye uptake; staining was localized primarily to aortic arch areas. Endothelial cells (luminal surface) from non-Evans blue and Evans blue arch areas were examined by a combination of Häutchen preparation (silver-stained vessels) and scanning and transmission electron microscopy. Endothelial cells from nicotine-treated arch areas (Evans-blue-stained) showed extensive changes such as: increased cytoplasmic silver deposition, increased formation of microvilli, and numerous focal areas of "ruffled" endothelium (projections on cell surfaces). These data indicate that nicotine, administered orally to rabbits, has a demonstrable in vivo morphologic effect on endothelial cells in the aortic arch.

Animals↗