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Biomedical subjects

E J Kerr

Publications and source records attributed to E J Kerr.

9 recordsLinked to original sources
PubMed1977

A specific direct radioimmunoassay for oestriol-16alpha-glucuronide in pregnancy plasma.

A specific radioimmunoassay has been developed for measuring oestriol-16alpha glucuronide in pregnancy plasma using a highly specific antiserum. The specificity of this antiserum has been assessed by the 50% displacement method and by measuring oestriol-16alpha-glucuronide concentrations in pregnancy plasma samples, both with and without chromatography. The antiserum was found to have Ka of 1.3 X 10(10) M-1. The assay had a sensitivity of 5 pg (least quantity of oestriol-16alpha-glucuronide distinguishable from the zero point, p less than 0.05), an intra-assay variation of 6.07% and an inter-assay variation of 3.36%. The assay was used to measure plasma oestriol-16alpha-glucuronide concentrations throughout eight pregnancies, five of which were normal and three had some defined abnormality.

Cross Reactions↗
PubMed1976

Studies on antistreptolysin O activity generated in serum by microorganisms.

An antistreptolysin factor (ASF) was generated in normal human serum by the growth of Staph, aureus and Pseud, aeruginosa. Alpha toxin producing strains of the former were usually positive but activity was not restricted to such strains. Positive strains produce cholesterol esterase which was obtained from DEAE-cellulose column fractions of 18 h broth cultures. Antistreptolysin factor develops slowly in serum, being maximal between the 5th and 10th days and is associated with alterations and disappearance of beta lipoproteins on gel electrophoresis. Activity also appeared in beta lipoproteins precipitated from normal serum with dextran sulphate and redissolved in nutrient broth before inoculation with Staph, aureus. The slow appearance of antistreptolysin activity in serum appears to be due to an esterase inhibitor which is present in high concentrations in some sera. Activity is also modified by the production of a staphylococcal fraction capable of binding to the antistreptolysin factor and reducing its activity. It is suggested that antistreptolysin factor which can be demonstrated in small amounts in normal human serum represents a readily available non-specific defence mechanism capable of binding to certain bacterial products and possible to other foreign protein molecules.

Antistreptolysin↗
PubMed1976

Cholesterol esterase activity in body fluids.

Antistreptolysin O activity (greater than or equal to 200 Todd units/ml) was found in 20% of 25 ascitic fluids, 20% of 55 pleural fluids and 37-5% of 56 joint fluids. These levels are not due to antibody but to the cholesterol moiety of altered beta-lipoproteins. The activity is precipitable with 10% dextran sulphate. Incubation of mixtures of fluids with titres less than 200 and normal human serum generated eight-fold or greater rises in antistreptolysin titres. This results from the activity of cholesterol esterase in the fluid acting on the beta-lipoprotein of the serum and activity was noted in 90% of ascitic fluids, 59% of pleural fluids and 54% of joint fluids. However, mixtures showing no such rise probably also contain esterase, the failure to demonstrate antistreptolysin activity being due to equilibration of ester derived cholesterol with sub-fractions of high density and very low density lipoproteins.

Antistreptolysin↗
PubMed1975

Functional role of cholesterol in infection and autoimmunity.

Cholesterol binds to streptolysin O and related bacterial toxins. In normal serum, only a fraction of the cholesterol attached to lipoprotein is available for binding, probably as a cholesterol-peptide complex formed during catabolic breakdown of the lipoprotein. Cholesterol esterase produced by certain organisms--e.g., Staphylococcus pyogenes and Pseudomonas oeruginosa--augments this fraction both in vitro and in vivo. Endogenous esterase similarly increases the amount of cholesterol-peptide complex, a mechanism which may be activated as a feedback process following binding of toxin to the cholesterol component of the complex. These complexes will thus supply a readily available means of binding bacterial toxins before antibody formation begins; Cholesterol-peptide complexes, either alone or modified by binding to toxin, may function as autoantigens. It is postulated that immune complexes so formed may be involved in atherosclerosis either by directly damaging vessels walls or by cross-reaction of antibody with cell-membrane-bound lipoproteins which equilibrate with plasma-lipoproteins.

Antibodies, Bacterial↗
PubMed1975

Partial characterisation of an inhibitor of streptolysin O produced by bacterial growth in serum.

An inhibitor of streptolysin O is generated in human and animal sera by the growth of certain organisms. The ability to do this occurs most often in Pseudomonas aeruginosa and Staphylococcus aureus (in 90% and 86% of strains respectively), but in only 32% of Staph. epidermidis strains. The inhibitor is not formed in broth. The effect appears slowly on incubation, with maximum activity after 4-7 days. Evidence suggests that two enzymes are involved, an esterase which splits ester-bound cholesterol and a proteolytic enzyme which partially hydrolyses lipoprotein, resulting in cholesterol remaining attached to protein or polypeptide fractions but with some alteration of its spatial configuration such that it is now capable of attaching to streptolysin O. The inhibitory factor appears to prevent streptolysin becoming attached to cholesterol receptor sites on the erythrocyte membrane. Removal of the precursor from serum with magnesium carbonate suggests that low-density lipoproteins may be the precursor of the inhibitor.

Albumins↗