Biomedical subjects

A Berge

Publications and source records attributed to A Berge.

13 recordsLinked to original sources

PubMed1995

Streptococcal cysteine proteinase releases biologically active fragments of streptococcal surface proteins.

Streptococcus pyogenes are important pathogenic bacteria which produce an extracellular cysteine proteinase contributing to their virulence and pathogenicity. S. pyogenes also express surface molecules, M proteins, that are major virulence determinants due to their antiphagocytic property. In the present work live S. pyogenes bacteria of the M1 serotype were incubated with purified cysteine proteinase. Several peptides were solubilized, and analysis of their protein-binding properties and amino acid sequences revealed two internal fibrinogen-binding fragments of M1 protein (17 and 21 kDa, respectively), and a 36-kDa IgG-binding NH2-terminal fragment of protein H, an IgGFc-binding surface molecule. M protein also plays a role in streptococcal adherence, and removal of this and other surface proteins could promote bacterial dissemination, whereas the generation of soluble complexes between immunoglobulins and immunoglobulin-binding streptococcal surface proteins could be an etiological factor in the development of glomerulonephritis and rheumatic fever. Thus, in these serious complications to S. pyogenes infections immune complexes are found in affected organs. The cysteine proteinase also solubilized a 116-kDa internal fragment of C5a peptidase, another streptococcal surface protein. Activation of the complement system generates C5a, a peptide stimulating leukocyte chemotaxis. C5a-mediated granulocyte migration was blocked by the 116-kDa fragment. This mechanism, by which phagocytes could be prevented from reaching the site of infection, may also contribute to the pathogenicity and virulence of S. pyogenes.

Adhesins, Bacterial↗

PubMed1993

Homogeneous immunofluorometric assays of alpha-fetoprotein with macroporous, monosized particles and flow cytometry.

We evaluated two homogeneous immunofluorometric assays (IFMAs) of alpha-fetoprotein (AFP) based on new macroporous acrylate particles combined with flow cytometry. The standard IFMA, requiring 1 h of incubation, provided a working range from 1.8 to > 900 kIU/L (CV < 10%) and a detection limit of 0.6 kIU/L. Use of overnight incubation and a lower particle concentration extended the working range by 1 decade in the lower end. Analytical recoveries for the standard IFMA varied between 97% and 108%. The slope and y-intercept of the regression line correlating measurements by the standard IFMA and a routine immunoradiometric assay were not significantly different from 1 and 0, respectively (P > 0.5), and the correlation coefficient was 0.996. High precision and warning of spuriously high measurements were obtained by including in each sample separate particle types for detecting instrument instability and measuring nonspecific binding only.

Acrylates↗

PubMed1988

Monosized, magnetic polymer particles: their use in separation of cells and subcellular components, and in the study of lymphocyte function in vitro.

By employing the principles of "activated swelling", monosized, superparamagnetic polymer particles have been prepared ranging in size from 1-100 microns. Both during and after the swelling process, the particles can be modified to meet a series of specific demands making them potentially very interesting for many separation and assay purposes. Using monoclonal antibodies to direct the magnetic beads to their targets, immunomagnetic separation has turned out to be one of the most specific, reliable and, above all, the fastest technique available today to isolate particulate material for further studies. So far, most efforts have been concentrated on methodology for fractionation of cells in suspension, such as removal of tumour cells from bone marrow or isolation of lymphoid cells from peripheral blood. These studies have both established the parameters necessary for optimal performance and at the same time laid the groundwork for future developments making immunomagnetic separation an exciting new tool in many research areas. High speed and specificity are the most conspicuous features of immunomagnetic cell separation. These properties have been exploited in the successful development of a new technique for tissue typing of cells directly from peripheral blood specimens. Both higher sensitivity and specificity have been obtained. The same principles can be used for fast and safe quantification of cell populations and subpopulations in blood and cell suspensions. The functions of, and interactions between, peripheral blood cell populations or subpopulations in the immune response have also been studied with high precision. The significance of direct cell contact on the one hand, and soluble factors on the other, can now be established in detail. Immunomagnetic beads have also been used to study the interaction between various T lymphocyte membrane molecules in the early phases of the activation process. Finally, the usefulness of specially developed particles for the fractionation of subcellular components is described.

Antibodies, Monoclonal↗

PubMed1985

In vivo activation of mouse macrophages with beta-1,3-D-glucan-derivatized plastic beads.

Macrophages obtained from animals treated with beta-1,3-D-glucan-derivatized plastic beads were greatly stimulated, as judged by morphology, esterase release, and cytostatic effect on L-929 tumour cells in vitro. The pretreatment of mice with such beads conferred an apparent absolute local resistance to an otherwise lethal pneumococcal infection but had no effect on the growth of intraperitoneal AA ascites sarcoma. Moreover, peritoneal cells from animals pretreated with glucan beads did not protect the animals in a Winn assay.

Animals↗

PubMed1984

Hydrophilic monodisperse particles as solid-phase material in immunoassays: comparison of shell-and-core particles with compact particles.

Hydrophilic monodisperse shell-and-core particles with a density of 1.07 were superior to heavier compact particles as a solid-phase material for immunoassays. The shell-and-core particles formed a semistable suspension for 24 h and were easily collected by centrifugation. The hydroxyl groups of the particles were activated with two sulfonyl chlorides. The most reactive one, tresyl chloride, gave rapid chemical coupling of antibodies, whereas tosyl chloride favored a rapid hydrophobic adsorption which was followed by slow chemical coupling. The solid-phase sheep antirabbit IgG made was used as a separation agent in several immunoassays and gave solid-phase primary antibodies by immunoadsorption of rabbit antibodies.

Animals↗

PubMed1983

Excess antibody immunoassay for rat glandular kallikrein. Monosized polymer particles as the preferred solid phase material.

The development of an excess antibody assay for rat glandular kallikrein is described. This assay permits immunological determination of kallikrein as well as a simultaneous specific measurement of kallikrein enzymatic activity. The assay is based on coupling of immunopurified anti-kallikrein immunoglobulin to a solid phase. In a first incubation step, kallikrein was bound to the immobilized antibody. Determination of kallikrein was subsequently done in a second incubation step; immunologically by addition of iodinated anti-kallikrein antibody, or enzymatically by a kallikrein substrate. Enzymatic quantification could also be followed by immunological measurements on the same sample. Comparison of Sepharose, cellulose, and acrylate based polymer particles proved the latter to be the best matrix in this assay. The main advantage of the polymer particles was the low non-specific binding of labelled antibody.

Animals↗

PubMed1976