Subject(s)
Bacterial Toxins/toxicity , Cyanobacteria/pathogenicity , Eutrophication , Marine Toxins/toxicity , Microcystins/toxicity , Alkaloids , Animals , Bacterial Toxins/analysis , Bacterial Toxins/pharmacokinetics , Bacterial Toxins/standards , Cyanobacteria/genetics , Cyanobacteria/isolation & purification , Cyanobacteria Toxins , Ecotoxicology , Environmental Monitoring/methods , Environmental Monitoring/standards , Fresh Water/analysis , Fresh Water/microbiology , Humans , Marine Toxins/analysis , Marine Toxins/pharmacokinetics , Marine Toxins/standards , Microcystins/analysis , Microcystins/pharmacokinetics , Microcystins/standards , Pharmacokinetics , Polymerase Chain Reaction/methods , Public Health , Reference Standards , Research Design , Risk Assessment , Uracil/analogs & derivatives , Uracil/analysis , Uracil/toxicityABSTRACT
Cyanotoxins are a group of compounds produced by cyanobacteria that can have severe physiological effects on other organisms, including humans. The potential allelopathic effects of Microcystis aeruginosa, a toxic cyanobacterium, on the duckweed plant, Lemna gibba L., were examined using three experimental methods: (1) a series of toxicity bioassays, (2) evaluation of toxin production by M. aeruginosa in the direct and indirect presence of L. gibba, and (3) inhibition of oxygen evolution in photosynthesis. The results showed that, first, there were no clear dose-dependent effects of the microcystin-LR standard or the toxic M. aeruginosa culture filtrate on any of the end points measured in the toxicity bioassays (plant and frond number, dry weight, growth rate, chlorophyll content; one-way ANOVA, p > 0.05). In those cases in which an EC(50) value could be obtained, chlorophyll a was the most sensitive end point, as it had the lowest EC(50) value (14.47 microg/L microcystin-LR) of all the end points. Second, the presence of L. gibba did not result in higher microcystin-LR production in the toxic M. aeruginosa culture. And, last, oxygen evolution was not affected in isolated chloroplasts exposed directly to microcystin-LR. Therefore, microcystins from the toxic cyanobacterium Microcystis aeruginosa do not appear to have an allelopathic effect on the common aquatic macrophyte Lemna gibba.
Subject(s)
Araceae/growth & development , Cyanobacteria/pathogenicity , Enzyme Inhibitors/toxicity , Peptides, Cyclic/toxicity , Araceae/physiology , Biological Assay , Chlorophyll/analysis , Lethal Dose 50 , Marine Toxins , Microcystins , Population DynamicsABSTRACT
Earlier associations of polymorphism in classic HLA class II (DRB1 and DQB1) genes have been extended to include the accessory genes DMA and DMB as determinants of disseminated Mycobacterium avium complex (DMAC) infection among HIV-1-seropositive whites. From the Multicenter AIDS Cohort study, 176 DMAC cases were matched with 176 controls in a nested case-control study. PCR-based HLA genotyping techniques were used to resolve variants of DRB1 and DQB1 to their four-digit or five-digit alleles, and single-strand conformation polymorphism was used to resolve sequences in exon 3 at each DM locus. The DMA*0102 allele occurred less frequently among DMAC cases than among controls (OR = 0.46, p =.02). Combinations of DRB1 alleles with or without specific DMA and DMB variants showed significant differences in distributions between the cases and controls, but both of the previously associated class II alleles (DRB1*1501 and DRB1*0701) showed stronger positive associations with DMAC in the absence than in the presence of DMA*0102. Apparent joint effects of DRB1 and DM allelic combinations on occurrence and timing of DMAC suggest that class II disease relationships may be better predicted by biologically plausible interactive combinations than by polymorphisms in individual genes.
