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Biomedical subjects

A E Stevens

Publications and source records attributed to A E Stevens.

33 records · Page 2Linked to original sources
PubMed1980

Mastitis and abortion in dairy cattle associated with Leptospira of the serotype hardjo.

Following a sudden drop in milk yield in a large dairy herd, leptospiral mastitis due to serotype hardjo was diagnosed serologically and by isolation of the organism from the milk and urine of affected cows. Two milkers subsequently became ill and developed titres to the Hebdomadis serogroup. During the same period the neighbouring herd experienced poor milking performance and a series of abortions and serological evidence suggested recent hardjo infection. The common source of infection appeared to be infected down calving heifers.

Abortion, Veterinary↗
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↗