Biomedical subjects

J A Verschoor

Publications and source records attributed to J A Verschoor.

26 records · Page 2Linked to original sources

PubMed1988

Isotype restriction of murine antibodies towards the loop region of hen's egg white lysozyme.

Monoclonal antibodies specific for the loop determinant (residues 64-80) of hen's egg white lysozyme demonstrated an immunoglobulin class restriction. Only IgM response against the loop could be evoked in mice, irrespective of whether the immunogen was the intact native lysozyme as such, or the loop peptide covalently conjugated to a synthetic carrier, poly-DL-alanyl-poly-L-lysine (A-L). Despite the fact that in polyclonal antisera from mice immunized with lysozyme, the ELISA-titre of anti-loop reactivity was very low, 26% of the total anti-lysozyme response could be accounted for by the loop when expressed as the percentage of anti-lysozyme hybridoma colonies producing monoclonal antibodies reactive with the loop. The results can be interpreted either as determinant controlled isotype restriction, or alternatively, as an affinity restriction leading to the phenomenon that antibodies of isotypes other than IgM are formed, but are of too low avidity to be detected by the ELISA method.

Animals↗

PubMed1987

The influence of the sesquiterpene lactones from Geigeria on mast cell degranulation.

The sesquiterpene lactones isolated from Geigeria were found to be incapable of inducing rat peritoneal mast cell degranulation at levels of 0.3-1.6 mM. The sulphydryl reagent, N-ethylmaleimide, too was unable to trigger mast cell secretion. Instead, it was observed that these compounds inhibited the release of histamine induced by Compound 48/80. Pretreatment of the lactones and N-ethylmaleimide with the amino acid, L-cysteine, reduced their inhibition ability of histamine release to a considerable extent, but not completely. Geigerin(V), which lacks an alpha-methylene group and the chemically prepared cysteine-adduct of dihydrogriesenin(I), were also capable of inhibiting mast cell secretion by Compound 48/80, but to a lesser extent.

Alkylation↗

PubMed1987

The development of an ELISA-assay for semi-quantitative detection of dihydrogriesenin, a sesquiterpene lactone from Geigeria.

Certain species of Geigeria contain sesquiterpene lactones which cause vomiting disease in sheep. Dihydrogriesenin (DHG), a sesquiterpene lactone from G. asperta, contains an alpha-methylene function which can spontaneously react with thiol groups on proteins to form a covalent adduct. A specific antiserum against a DHG-protein adduct can be used to determine the fate of DHG in poisoned animals. The preparation of such an antiserum is reported in this paper. DHG was reacted with cysteine and subsequently coupled to serum albumin using the carbodiimide reaction. When rabbits were immunized with one such conjugate (DHG-bovine serum albumin), it was found that the carrier determinants were immunodominant. A DHG-specific anti-serum of sufficient (ELISA) titre could, however, be obtained by alternating serum albumin carriers for DHG in booster immunizations. The ELISA antigen-antibody reaction could be inhibited by prior reaction of the antisera with cysteinyl-DHG in solution.

Animals↗

PubMed1986

Isolation of Cowdria ruminantium by means of Percoll density gradient centrifugation and detection by an enzyme-linked immunosorbent assay.

The isolation of Cowdria ruminantium by means of Percoll density gradient centrifugation permits the recovery of partially purified viable populations of the organism possessing distinctly different densities. These conclusions are based upon results of analyses of density fractions by intravenous inoculation into sheep, protein determination, electron microscopy and enzyme-linked immunosorbent assay. Morphological differences were observed in the density fractions obtained from infected brain tissue and Amblyomma hebraeum nymphae.

Animals↗

PubMed1985

Enrichment of a fraction toxic to guinea-pigs from Pachystigma pygmaeum (Schltr.) Robyns.

Pachystigma pygmaeum is one of several species of rubiaceous plants which cause delayed heart failure among ruminants after their ingestion at relatively high doses. Using guinea-pigs for toxicity determinations, we were able to separate and enrich a toxic fraction from a fermentation extract of the plant material by countercurrent distribution. It contained virtually no potassium salts, passed through a 500 dalton selective membrane, exhibited lability under acid conditions and was toxic at 1 g/kg per os, with a delayed response of 3-4 days.

Animals↗

PubMed1985

Isolation of Cowdria ruminantium by cellular affinity chromatography and detection by an enzyme-linked immunosorbent assay.

The isolation of Cowdria ruminantium by means of wheat germ lectin affinity chromatography as described in this paper permits the recovery of partially purified viable organisms under mild conditions in short time. These conclusions are based upon results of analyses of column fractions by intravenous inoculation into sheep, protein determination, electronmicroscopy and enzyme-linked immunosorbent assay. The entire purification procedure could be completed in 4-5 hours using only either infected sheep tissue or nymphae as starting material.

Animals↗

PubMed1984

Preparation and properties of a crude extract toxic to guinea-pigs from Pachystigma pygmaeum, a plant causing heart failure in ruminants.

Pachystigma pygmaeum is a rubiaceous plant which causes heart failure after ingestion by ruminants. Isolation or characterization of a toxic entity has hitherto been unsuccessful. Extraction of the plant material with water or organic solvents gave poor yields of toxicity in guinea-pigs because of some unusual properties of the toxic entity. We present a method whereby liberation of a toxic entity from the plant material was achieved by fermentation with baker's yeast to give a crude extract with sufficient yield of toxicity for use in further isolation work.

Animals↗

PubMedDate not supplied

Monoclonal antibody characterization of two field strains of Haemophilus paragallinarum isolated from vaccinated layer hens.

An oil-based bacterin, containing strains 083 and 0222 of Haemophilus paragallinarum, is commonly used in South Africa to vaccinate laying flocks against infectious coryza. Two strains of H. paragallinarum, designated M85 and SB86, were isolated from infected but vaccinated commercial laying flocks in two incidental outbreaks of coryza in 1985 and 1986. A panel of five monoclonal antibodies was established which clearly distinguished the vaccine strains from the field isolates. One of these reacted with only vaccine strains A and B, another reacted with only field strains M85 and SB86, and the remaining three cross-reacted to various degrees with all four strains or isolates. Immunoassays were performed by enzyme-linked immunosorbent assay using whole bacteria as solid-phase antigen. These monoclonal antibodies may aid in serotyping new field isolates of H. paragallinarum and in improved standardization of vaccine strains.

Animals↗