Laboratory evaluation of the toxicity of Perfluorooctane Sulfonate (PFOS) on Selenastrum capricornutum, Chlorella vulgaris, Lemna gibba, Daphnia magna, and Daphnia pulicaria.

Perfluorooctane sulfonate (PFOS) is an anthropogenic compound found in trace amounts in many environmental compartments far from areas of production. This, along with the highly persistent nature of PFOS, presents a concern for possible effects in aquatic ecosystems. The objective of this study was to determine the toxicity of PFOS in representative freshwater organisms. Toxicity testing using standard laboratory protocols was performed on the green algae Selenastrum capricornutum and Chlorella vulgaris, the floating macrophyte Lemna gibba, and the invertebrates Daphnia magna and Daphnia pulicaria. No observable effect concentration (NOEC) values were generated from the most sensitive endpoints for all organisms. Autotroph inhibition of growth NOEC values were 5.3, 8.2, and 6.6 mg/L for S. capricornutum, C. vulgaris, and L. gibba, respectively. The 48-h immobility NOEC values for D. magna and D. pulicaria were 0.8 and 13.6 mg/L, respectively. In comparison to immobility, the 21-day lethality NOEC for D. magna was 5.3 mg/L. Based on effect (immobility) values, the most sensitive of all test organisms was D. magna. The most sensitive organism based on 50% inhibition of growth (IC(50)) was L. gibba, with an IC(50) value of 31.1 mg/L determined from wet weight. This is 4.3 times less than the LC(50) for D. pulicaria, which was 134 mg/L. Significant adverse effects (p < or = 0.05) were observed for all organisms in concentrations >134 mg/L. The results indicate that under laboratory conditions PFOS is acutely toxic to freshwater organisms at concentrations at or near 100 mg/L. Based on known environmental concentrations of PFOS, which occur in the low ng/L to low microg/L range, there is no apparent risk to freshwater systems. However, further work is required to investigate long-term effects in these and other freshwater organisms.

Rapid evolution of NK cell receptor systems demonstrated by comparison of chimpanzees and humans.

That NK cell receptors engage fast-evolving MHC class I ligands suggests that they, too, evolve rapidly. To test this hypothesis, the structure and class I specificity of chimpanzee KIR and CD94:NKG2 receptors were determined and compared to their human counterparts. The KIR families are divergent, with only three KIR conserved between chimpanzees and humans. By contrast, CD94:NKG2 receptors are conserved. Whereas receptors for polymorphic class I are divergent, those for nonpolymorphic class I are conserved. Although chimpanzee and human NK cells exhibit identical receptor specificities for MHC-C, they are mediated by nonorthologous KIR. These results demonstrate the rapid evolution of NK cell receptor systems and imply that "catching up" with class I is not the only force driving this evolution.

CK-1, a putative chemokine of rainbow trout (Oncorhynchus mykiss).

Chemokines are small inducible proteins that direct the migration of leukocytes. While chemokines are well characterised in mammals, they have yet to be identified in fish. We have isolated a cDNA clone from rainbow trout (Oncorhynchus mykiss) which encodes a protein (CK-1) having structural features typical of chemokines. Amino-acid residues that define the beta-chemokines of mammals are conserved in CK-1, including the paired cysteine motif, CC. Further similarities are shared with the C6 subfamily of beta-chemokines. In contrast, the organisation of the CK-1 gene is closer to that of mammalian alpha-chemokine genes than beta-chemokine genes. The CK-1 gene is present in all four salmonid species examined and the nucleotide sequences of the exons are highly conserved. CK-1 has characteristics in common with mammalian alpha and beta-chemokine genes, suggesting that this salmonid chemokine gene preserves traits once present in the ancestral chemokine gene from which modern mammalian chemokine genes evolved.