The beta-gal interferon assay: a new, precise and sensitive method.

Cells of a human glioblastoma line were stably transfected with a glial fibrillary acidic protein (GFAP) promoter sequence/lacZ reporter gene. Following this modification, they produced Escherichia coli beta-galactosidase constitutively in amounts that could be measured through their conversion of an added fluorophore into a product readily estimated by fluorimetry. Human interferons (IFN) selectively and in a dose-dependent manner reduce the formation of beta-galactosidase in this system. We have used it as the basis for a novel assay that is sensitive (4-40 pg/ml), precise, completed in 30 h, and applicable to both type I and type II human IFNs. Statistical analysis showed interassay relative standard deviations ranging from 5% to 11%, and most individual assays revealed potencies with limits of error within 85%-115%. Neither partially trypsin-digested IFN nor the other cytokines and mitogens we tested reacted in this system, except for tumor necrosis factor-alpha (TNF-alpha). The high selectivity was further shown by the loss of response to IFN in the presence of the appropriate specific anti-IFN or anti-IFN-gamma receptor antibodies.

An illustrated guide to RFLP troubleshooting.

A large number of reagents and steps are required for restriction fragment length polymorphism (RFLP) analysis, which at times make determining the cause of any observed anomaly difficult. Troubleshooting problems in RFLP analysis is difficult and often the exact cause of a problem cannot be determined. In this paper a collection of controlled experiments detail the consequences of a number of human or materials problems. Although the focus is on forensic applications, this troubleshooting guide will be helpful to anyone employing Southern analysis.

Control of an activated sludge process with nitrogen removal--a benchmark study.

In this paper, a simulation benchmark of a predenitrifying activated sludge process is used to evaluate a number of control strategies. A main procedure has been to use feedforward terms that are based on simplified physical models. Important mass balance relations may then be incorporated in the control law. The nitrate level in the last anoxic zone is controlled by the dosage of an external carbon source and the nitrate level in the last aerobic zone is controlled by the internal recirculation flow rate. The ammonia level is controlled by a DO set-point controller. In order to be able to have as high a sludge level as possible without sludge escape, the sludge blanket height in the settler is controlled by the excess sludge flow rate. Compared to the default set up of the benchmark, the controllers could reduce the effluent nitrate significantly whereas the effluent ammonia was only marginally decreased. The main problem is that the aeration capacity defined in the benchmark is too low.