A fast, convenient and rugged procedure for characterizing the selectivity of alkyl-silica columns.

Previous work has shown that the selectivity of reversed-phase columns for HPLC can be described by means of five column parameters: H (hydrophobicity), S* (steric resistance), A (hydrogen-bond acidity), B (hydrogen-bond basicity) and C (cation-exchange capacity). Values of H, S*, etc. can be determined by carrying out retention measurements for 18 test solutes under standardized conditions. The reproducibility of the latter procedure has been evaluated by comparison testing in four different laboratories and found acceptable. An alternative 10-solute test procedure which is more reproducible and convenient (but somewhat less accurate), requires only 2-3 h per column.

Electrical and reliability properties of PZT thin films for ULSI DRAM applications.

The electrical and reliability characteristics of ferroelectric capacitors fabricated using sol-gel derived 50/50 lead-zirconate-titanate (PZT) thin films have been examined for ULSI DRAM (dynamic random access memory) applications. Various electrode materials, film thicknesses (200 nm to 600 nm) and capacitor areas were used. A large stored-energy density (Q(c)) of 15 muC/cm(2) (at 125 kV/cm) was measured using different methods. The results indicate that PZT thin films exhibit material properties which might satisfy the requirements of ULSI DRAMs.

A rapid screening enzyme linked immunosorbent assay for autoantibodies to extractable nuclear antigens.

An enzyme linked immunosorbent assay (ELISA) has been developed to detect antinuclear antibodies to extractable nuclear antigens (ENA)--a rabbit thymus nuclear derivative. A second ELISA has also been developed (ENA RNA-ase ELISA) to analyse the relative contribution of the components of ENA (nucleoprotein and RNA antigens) to antibody binding as detected by the ELISA assays. Both ELISA assays provide a rapid screening method for antibodies to soluble, diffusable nuclear antigens that could otherwise go undetected by immunodiffusion or the indirect immunofluorescent method that uses unfixed frozen sections of rat liver. The considerable improvement that these ELISA assays offer in efficiency and both diagnostic and serological sensitivity over the traditional immunodiffusion method used for specificity characterisation of ENA autoantibodies is discussed.

An enzyme-linked immunosorbent assay for antistriational antibodies associated with myasthenia gravis and thymoma: comparison with indirect immunofluorescence.

Autoantibodies to the striations of skeletal muscle (AStrA) detected by immunofluorescence are useful in the diagnosis of a thymoma associated with myasthenia gravis (MG). With the intention of developing a better method, an enzyme-linked immunosorbent assay (ELISA) has been evaluated in 147 MG patients and 200 healthy controls. An additional 107 patients with various autoimmune diseases and autoantibodies were also tested. With a crude actomyosin preparation, the ELISA gave similar results to immunofluorescence, viz. positives in 42% of MG patients, but in all with a histologically proven thymoma. Less than 1% of the healthy controls were positive but false positives were found in patients with liver disease and anti-smooth muscle antibodies. After treatment of rheumatoid arthritis with D-penicillamine the titre of AStrA may rise. The ELISA was shown to be sensitive and reproducible, but immunofluorescence is a more practical method of distinguishing between the different categories of anti-muscle antibodies. ELISA should prove particularly useful for quantitation and sequential monitoring.

Myasthenia gravis and D-penicillamine.

There has been some uncertainty as to whether the apparent association between myasthenia gravis (MG) and D-penicillamine (D-P)-treated rheumatoid arthritis (RA) could be due to chance or whether the drug is responsible. In the absence of D-P, RA is found in association with MG, but this may simply reflect the high prevalence of RA. Although MG may be more common than expected after D-P treatment of RA, it probably occurs in only approximately 1% of such patients. In these circumstances, it is difficult to prove that D-P can induce MG, but compelling evidence in support for this possibility comes from the finding of differences between autoantibodies when spontaneous and D-P-associated MG are compared. These serologic differences could be explained in terms of an effect of D-P on antigen presentation and/or immunoregulation.

Immunobiology of D-penicillamine.

D-penicillamine holds the key to a better understanding of autoimmunization and the pathogenesis of autoimmune disease. Analysis of its mode of action is complicated by its multiplicity of effects. In respect to anti-acetylcholine receptors and myasthenia gravis, the major effect may be at the level of immunoregulation and/or immunogenicity. Anti-striated muscle antibody is much more common and is influenced by the HLA antigen of the patient. Thus, HLA-linked immune response genes may be involved.