Self-labeling of human polymorphonuclear leucocyte myeloperoxidase with125iodine

In order to obtain a radioimmunoassay (RIA) technique for the measurement of human plasma myeloperoxidase (MPO), we purified the enzyme from polymorphonuclear granulocytes (neutrophils), and compared three methods of labeling it with¹²⁵Iodine: chloramine T, lactoperoxidase, and an original technique of self labeling based on the ability of the enzyme to oxidize and bind¹²⁵I in the presence of H₂O₂. The chloramine T technique produced a degraded protein, as well shown by a high non-specific binding of tracer to antibody. The lactoperoxidase technique did not succeed in labeling MPO with an adequate specific activity. In contrast, the self-labeling method gave a stable tracer with a specific activity of 23 Ci/gmg MPO (85 MBq), a satisfactory level of immunoreactivity, and a low-specific binding (3%). After labeling, purification of tracer was achieved by gel filtration chromatography in phosphate buffer (0.05 M; pH7) to which 0.1% poly-L-lysine was added. The labeled molecule remained stable for 40 days and could be used for RIA with a polyclonal antibody raised in rabbits.     

Genetic factors in neurotoxicology and neuropharmacology: A critical evaluation of the use of genetics as a research tool

Animals have evolved a detoxication system to enable them to survive in a hostile chemical environment in which foods contain many non-nutrient chemicals. Detoxication depends on enzymes which are often genetically polymorphic. As a result, inter-individual variation is common, and in humans several Mendelian loci have been identified. However, most variation in response is probably due to the action of several genes. Genetic variation in response to the neurotoxin MPTP and to chemically and physically-induced seizures is reviewed. In the former case, differences between pigmented and white mouse strains have been noted which are consistent with the hypothesis that humans are more sensitive than mice or rats because of the presence of melanin in human brains. However, variation in sensitivity probably also depends on other genes. In the case of audiogenic seizures, a single locus has been identified and mapped, but its relationship with seizures induced by other agents is not clear. Genetic variation in response to alcohol is also discussed. The failure of most toxicologists to consider genetic variation as a potentially confounding variable, and as a powerful research tool, is discussed critically in relation to non-repeatability of research on the neurotoxic effects of lead, and in relation to the genetic variation in MPTP, seizures, and alcohol response already noted. It seems clear that genetic methods provide a powerful research tool which is largely being ignored by toxicologists.     

Identification and possible biological relevance of spermatozoal transglutaminase

Summary Normal human spermatozoa were demonstrated by dot immunoblot analysis and immunohistochemistry to possess transglutaminase (TGase). The immunological identification of spermatozoal TGase is consistent with reports by others of its biochemical identification and suggested role in sperm motility,and provides, in view of the immunoregulatory properties of seminal plasma TGase, presumptive identification of a means whereby spermatozoa, under normal physiological conditions, may possibly be protected from immunological attack within the female reproductive tract.     

Gigantecin: A novel antimitotic and cytotoxic acetogenin,with nonadjacent tetrahydrofuran rings,fromGoniothalamus giganteus (Annonaceae)

Summary Gigantecin (I), a novel tetrahydroxy-di-tetrahydrofuran fatty acid -lactone (acetogenin), was isolated from an ethanolic extract of the stem bark ofGoniothalamus giganteus Hook. f., Thomas (Annonaceae), by means of activity-directed fractionation (brine shrimp lethality test). This new compound is extremely cytotoxic to human tumor cells, inhibits crown gall tumors on potato discs, and is active in an assay designed to detect antimitotic agents (9 ASK).