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Biomedical subjects

T Porstmann

Publications and source records attributed to T Porstmann.

At least 73 records · Page 4Linked to original sources
PubMed1983

Determination of immunoglobulin class and subclass of monoclonal antibodies to human alpha-fetoprotein by solid phase radioimmunoassay.

A solid phase radioimmunoassay using the incubation sequence: mouse immunoglobulin (Ig) rabbit anti-mouse Ig, monoclonal antibody and 125I-labeled antigen was performed to determine the class and subclass of seven murine monoclonal antibodies against human alpha-fetoprotein. All antibodies belonged to the IgG class. The subclass type was IgG 2a for four antibodies, IgG 1 for two antibodies and IgG 2b for one antibody.

Antibodies, Monoclonal↗
PubMed1982

Comparison of direct and indirect two-site binding enzyme immunoassay.

Rabbit IgG, directed against HBsAg, was purified by positive and by negative affinity chromatography and applied in horseradish peroxidase labelled as well as in unlabelled form in the direct and indirect two-site binding enzyme immunoassay (EIA). Comparing direct and indirect assay the latter is more sensitive and less conjugate consuming. In contrast to the indirect assay in which antibodies, purified by positive affinity chromatography, do not alter detection limit, a 4- to 8-fold higher sensitivity was achieved in the direct EIA in contrast to antibodies, purified by negative affinity chromatography. In the indirect EIA unlabelled second and labelled third antibodies were incubated successively as well as simultaneously. The latter procedure shortened the assay time but needed antibodies purified by positive affinity chromatography and a 10-fold higher conjugate concentration. Greatest sensitivity was obtained in the indirect EIA by the use of labelled second and labelled third antibodies (20-30 ng/l HBsAg).

Chromatography, Affinity↗
PubMed1982

Quantitation of a pregnancy associated globulin in the rat by two-site binding enzyme immunoassay.

An indirect two-site binding enzyme immunoassay has been developed to quantify the pregnancy associated globulin (PAG) in rats. Anti-PAG from guinea pig is adsorbed to solid phase and binds serum-PAG, which then reacts with its remaining free determinants with anti-PAG from rabbit. Sheep anti-rabbit IgG, labeled with horse radish peroxidase (HRP), binds to the rabbit anti-PAG antibody and the enzymic activity of the solid phase is measured by incubation with the appropriate chromogenic substrate. The optical density is directly related to the quantity of PAG to be measured. Reproducible results are obtained in the range from 5 to 200 micrograms/l. The test detects 12 fmoles of PAG. Female rats show a 1000-fold higher serum level of PAG than male rats. Strain differences of the distribution of the PAG serum concentration were only found between male rats.

Animals↗
PubMed1981

Temperature dependent rise in activity of horseradish peroxidase caused by non-ionic detergents and its use in enzyme-immunoassay.

Non-ionic detergents such as polyoxyethylene-octylphenol or -sorbitolester were found to increase activity of horseradish peroxidase due to delay of inactivation in the course of substrate reaction. This rise in activity was investigated using different chromogens and was highest with o-dianisidine. An increasing stability of the enzyme to higher reaction temperatures was observed when detergents were added to the substrate solution, and the action of detergents also is enhanced with increasing reaction temperature and time. Different degrees of activation were found when comparing substrate conversion with and without detergents using free peroxidase (2.7-fold) and conjugated peroxidase bound to the solid phase by antigen antibody reaction (1.8-fold). In enzyme-immunoassay, detection limit and analytical sensitivity can be doubled.

Antigen-Antibody Reactions↗
PubMed1981

Comparison of chromogens for the determination of horseradish peroxidase as a marker in enzyme immunoassay.

o-Phenylenediamine, 2,2'-azino-di(3-ethylbenzthiazoline sulphonic acid-6) (ABTS), o-dianisidine and 4-aminoantipyrine were compared as chromogens for the determination of horseradish peroxidase. Highest sensitivity in the determination of horseradish peroxidase-IgG conjugates in dissolved form was obtained with o-phenylenediamine. When these conjugates were used in a two-site binding enzyme immunoassay for hepatitis B surface antigen (HBsAg), the steepest calibration curve and the lowest detection limit were obtained when ABTS was used to determine the immune complexes bound to the solid phase. Non-ionic detergents, such as polyoxyethylene-sorbitol ester, retarded horseradish peroxidase inactivation, resulting in a chromogen-dependent activity rise of horseradish peroxidase. An optimised determination of horseradish peroxidase is reported, in which the sensitivity of the solid phase enzyme immunoassay is doubled by the use of o-dianisidine.

Ampyrone↗
PubMed1981

Effect of IgG-horseradish peroxidase conjugates purified on Con A-Sepharose upon sensitivity of enzyme immunoassay.

Antibodies coupled to horseradish peroxidase (HRP) were purified by gel filtration and by combination of affinity chromatography and gel filtration. Binding kinetics to solid phase bound antigens were studied of the antibody-enzyme conjugates in the presence and in the absence of unlabelled IgG. The detection limit in enzyme immunoassay was found to be lowered by factor 16 after elimination of unlabelled IgG from the conjugate.

Animals↗
PubMed1980

Isolation of a pregnancy-associated globulin (PAG) from the rat and preparation of a specific antiserum (anti-PAG).

Isolation of a glycoprotein from serum of pregnant rats has been accomplished by ammonium sulphate precipitation, gel filtration, ion exchange and affinity chromatography. Low concentrations of the protein were detectable in the serum of some of the male rats tested, while somewhat higher concentrations were detected also in the serum of non-pregnant female rats. No relationship could be established between this protein and the well known pregnancy-specific proteins or the alpha 2-acute phase-macroglobulin of the rat, whereas evidence was obtained for a strong cross-reaction with a serum protein of pregnant mice.

Animals↗
PubMed1979

[Purification of horseradish peroxidase conjugated IGG by affinity chromatography. Comparison of glutaraldehyde and periodate conjugation].

By affinity chromatography of the coupling mixture on Concanavalin-A-Sepharose unlabeled IgG is completely removed. HRP conjugated IgG is then separated from free HRP by gelfiltration. Glutaraldehyde conjugation yielded 20 to 68% unlabeled IgG, depending on the duration of glutaraldehyde addition, and periodate conjugation yielded 10 to 28% unlabeled IgG. By this method fractions of conjugates with 3fold spec. act. were obtained by the glutaraldehydemethod and with 1.6fold spec. act. by periodate method as compared with gelfiltration. The periodate method guarantees a 3fold higher yield of HRP-labeled IgG compares with glutaraldehyde method. Both methods produce conjugates of the same spec. act. although the denaturation of HRP is much greater at periodate conjugation. When applying of affinity chromatography and gelfiltration. Crude HRP with 7% spec. act. of purified HRP resulted in conjugates having a spec. act. of 85% of those with purified HRP.

Animals↗