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Biomedical subjects

B Heymer

Publications and source records attributed to B Heymer.

At least 127 records · Page 7Linked to original sources
PubMed1974

Investigations on the specificity of the Limulus test for the detection of endotoxin.

Lysates obtained from amoebocytes of Limulus polyphemus, the horseshoe crab, showed gel formation after the addition of bacterial endotoxin. In contrast to living gram-negative bacteria, viable gram-positive microorganisms did not cause gelation of lysate. Nevertheless, peptidoglycan isolated from the cell walls of various gram-positive organisms did induce the reaction. However, the activity of peptidoglycan was 1,000 to 400,000 times less than that of Escherichia coli lipopolysaccharide. After exposure to lysozyme, peptidoglycan no longer gelled amoebocyte lysate, therefore apparently excluding endotoxin contamination. Gelation of amoebocyte lysate by endotoxin or peptidoglycan was inhibited by different concentrations of sodium polystyrolsulfonate. Whereas these studies confirm the specificity of the Limulus test for bacterial endotoxins, they also indicate that other substances of bacterial origin should be investigated for their ability to gel amoebocyte lysate.

Arachnida↗
PubMed1973

Inhibition of macrophage migration by nucleotide-containing streptococcal preparations.

Certain extracts of streptococcal cell walls are known to inhibit macrophage migration in vitro. In this study, we attempted to identify the streptococcal components responsible for this phenomenon. Trypsinized cell walls and cytoplasm from groups A and B streptococci were extracted with hot formamide followed by acetone precipitation. Subsequent gel filtration in aqueous solutions yielded a fraction devoid of C-carbohydrate and containing mostly oligonucleotides, apparently derived from streptococcal cytoplasm. This fraction significantly inhibited the migration of peritoneal exudate cells from rats sensitized to groups A and B streptococci. It was noteworthy that no inhibition of migration was observed with cells from nonsensitized animals or control rats injected with BCG or complete Freund adjuvant. Similarly, no inhibition was obtained with formamide extracts of calf thymus RNA. Although the inhibition does not show specificity for streptococcal groups, it seems to have immunological specificity since prior sensitization with streptococci is required for migration inhibition.

Animals↗