PubMed Health⌕ Search

Biomedical subjects

A E Stevens

Publications and source records attributed to A E Stevens.

14 recordsLinked to original sources
PubMed1987

Serological studies on British isolates of the Sejroe serogroup of leptospira. II. An evaluation of the factor analysis method of identifying leptospires using strains belonging to the Sejroe serogroup.

Twelve British isolates of leptospira belonging to the Sejroe serogroup were examined using a series of six factor sera prepared by a number of different absorption methods. Ten of the isolates were identified as Leptospira interrogans serovar hardjo and two as L. interrogans serovar saxkoebing. These isolates had previously been identified using the cross agglutination absorption method.

Agglutination Tests↗
PubMed1987

Serological studies of British leptospiral isolates of the Sejroe serogroup. III. The distribution of leptospires of the Sejroe serogroup in the British Isles.

Some 94 strains of leptospires belonging to the Sejroe serogroup isolated in the British Isles were identified to the serovar level using specific factor sera. Seventy strains were identified as Leptospira interrogans serovar hardjo, 66 from cattle, 2 from pigs and 1 each from a sheep foetus and a human. Twenty-four strains were identified as L. interrogans serovar saxkoebing, most strains were isolated from either wood mice, bank or field voles but strains were also isolated from badgers, a fox and a dog.

Animals↗
PubMed1986

Serological studies on British leptospiral isolates of the Sejroe serogroup. I. The identification of British isolates of the Sejroe serogroup by the cross agglutinin absorption test.

Using the cross agglutinin absorption test 12 British leptospiral isolates of the Sejroe serogroup were identified to serovar level. Six strains isolated from cattle, two from pigs and one from a human were identified as Leptospira interrogans serovar hardjo. Two isolates from wildlife were identified as Leptospira interrogans serovar saxkoebing. One further strain isolated from wildlife closely resembled serovar saxkoebing, but specific identification was not possible. These are the first reported isolations of serovar saxkoebing in the United Kingdom. The problems associated with the cross agglutinin absorption test, and possible alternative typing procedures are discussed.

Agglutination Tests↗
PubMed1977

Preliminary characterization of cell-free K99 antigen isolated from Escherichia coli B41.

The K99 antigen of Escherichia coli B41 was isolated by isoelectric precipitation from heated bacterial suspensions. Chromatography and immunoabsorption experiments suggested that the mannose-resistant haemagglutinating activity of partially purified preparations of antigen was K99. The antigen was partially susceptible to bacterial proteases and was inactivated by periodate oxidation. Haemagglutination inhibition experiments with sugars and absorption of K99 with antisera to human blood groups A and B substances suggested that K99 contains a terminal alpha-linked N-acetylgalactosamine moiety, which is involved in the haemagglutination reaction, and an adjacent terminal alpha-linked galactose moiety, which plays no part in the reaction.

Acetylgalactosamine↗
PubMed1976

An evaluation of the methods available for analysing results from migration inhibitory factor (MIF) test.

In order to illustrate the potential dangers in using some of the methods available for calculating migration inhibitory factor (MIF) activity, selected results have been analysed in a number of different ways. The weights corresponding to the migration areas were used in a single ratio expression and then in a double ratio formula to calculate migration inhibition. Conclusions from these results were made using both the arbitrary 20% inhibition to indicate MIF activity and a statistically-derived minimum percentage inhibition needed to demonstrate a significant effect. The procedure was then repeated using the square root of the weight equivalents of the migration areas. A double ratio expression was preferable to the single ratio formula as the former considered the information from all the control cultures. The degree of inhibition needed to demonstrate MIF activity varied between tests and for accurate interpretation of the results it was necessary to use a statistically derived minimum value for inhibition in each experiment. Use of the square root of the weight equivalents of migration areas in the double ratio method gave conclusions analogous to those using the actual weights. Use of the square root transformation narrowed the difference between sample means and caused a corresponding reduction in within-sample variability.

Animals↗
PubMed1976

Aggregation and anticomplementary activity of an antigen used in the complement fixation test for Johne's disease.

Exhaustive lipid extraction of the Johne's bacilli before preparing the Maltaner-Wadsworth antigen removed both the anticomplementary activity of the preparation and its ability to fix complement. Gel filtration temporarily removed anticomplementary activity but tended to reduce the antigenic activity of the extract. Sonication significantly reduced the anticomplementary activity of the antigen without affecting its capacity to fix complement but the effects were only temporary. It is suggested that the antigen exists as micelles which gradually aggregate and re-arrange thereby exposing anticomplementary sites hitherto masked in the dispersed micelles.

Animals↗