Haplotype dimorphism in a SNP collection from Drosophila melanogaster.

A moderate resolution single nucleotide polymorphism (SNP) map of the genome of Drosophila melanogaster that is designed for use in quantitative genetic mapping is described. Seventeen approximately 500 nucleotide gene sequences spaced at 10 to 20 centimorgan intervals were combined with 49 shorter sequence tag sites (STSs) at 5 to 10 centimorgan intervals to generate a map that should not leave any gaps greater than one half of a chromosome arm when any two wild type lines are compared. Of 20 markers with sufficient polymorphism to construct haplotype cladograms, 13 showed evidence for two divergent classes of haplotype. The possible mechanisms for and implications of the unexpected finding that two thirds of all short gene sequences in D. melanogaster may be dimorphic are discussed, including the suggestion that admixture between two separate lineages may have been a major event in the history of the species.

Absence of protein polymorphism in the Ras genes of Drosophila melanogaster.

Sequence analysis of 27 alleles of each of the three Ras-related genes in Drosophila melanogaster indicates that they all have low levels of polymorphism but may experience slightly different evolutionary pressures. No amino acid replacement substitutions were indicated in any of the sequences, or in the sibling species D. simulans and D. mauritiana. The Dras1 gene, which is the major ras homologue in Drosophila, has less within-species variation in D. melanogaster relative to the amount of divergence from the sibling species than does Dras2, although the contrast was not significant by the HKA test. Dras2 appears to be maintaining two classes of haplotype in D. melanogaster, one of which is closer to the alleles observed in the sibling species, suggesting that this is not likely to be a pseudogene despite the absence of a mutant phenotype. Although differences in level of expression may affect the function of the genes, it is concluded that genetic variation in the Ras signal transduction pathways cannot be attributed to catalytic variation in the Ras proteins.

Naturally occurring genetic variation affects Drosophila photoreceptor determination.

The signal transduction pathway controlling determination of the identity of the R7 photoreceptor in the Drosophila eye is shown to harbor high levels of naturally occurring genetic variation. The number of ectopic R7 cells induced by the dosage-sensitive SevS11.1 transgene that encodes a mildly activated form of the Sevenless tyrosine kinase receptor is highly sensitive to the wild-type genetic background. Phenotypes range from complete suppression to massive overproduction of photoreceptors that exceeds reported effects of known single gene modifiers, and are to some extent sex-dependent. Signaling from the dominant gain-of-function Drosophila Epidermal Growth Factor Receptor (DER-Ellipse) mutations is also sensitive to the genetic backgrounds, but there is no correlation with the effects on SevS11.1. This implies that different genes and/or alleles modify the two activated receptor genotypes. The evolutionary significance of the existence of high levels of genetic variation in the absence of normal phenotypic variation is discussed.

Effects of copper and zinc on proteoglycan metabolism in articular cartilage.

Co-Cultures of porcine articular cartilage and synovium or synovial conditioned medium were used as an in vitro model to mimic inflammatory events at the cartilage/synovial junction in degenerative joint disease. This model provides a useful tool to assess the anti-inflammatory and antiarthritic properties of pharmacological agents. In this study the effects of copper and zinc on (i) PG synthesis by cartilage and (ii) synovial-induced PG depletion have been investigated. Copper sulphate at a concentration of 0.01 mM did not stimulate PG synthesis significantly in cultured cartilage explants but completely abrogated the inhibitory effects of synovial tissue in co-culture experiments. This finding was supported by the histological demonstration of copper-dependent reversal of the PG depletion in cartilage exposed to synovial conditioned medium. Zinc sulphate at 0.01 mM had no effect on PG synthesis and was unable to protect cartilage against synovialinduced PG depletion. These results reveal possible mechanisms by which copper exerts its anti-inflammatory and anti-arthritic actions.

Copper and zinc body levels in inflammation: an overview of the data obtained from animal and human studies.

The development of acute and chronic inflammatory processes induces, in the laboratory animal, a net accumulation of both copper and zinc in many body compartments, the inflamed area included. In rheumatoid arthritis, as well as in animal models, only plasma zinc concentration seems to be significantly correlated with disease severity, while the increase in total plasma copper could be described as an "all or nothing" phenomenon. Moreover, in rheumatoid arthritis, it appears that the disease develops and progresses without being linked to either copper or zinc deficiency conditions. Thus, it seems reasonable to suggest that a rationale for the use of copper and/or zinc in the treatment of inflammatory disorders can only be drawn from the intrinsic pharmacological properties of such trace elements, rather than from the need for their repletion.

Copper and zinc status in rheumatoid arthritis: studies of plasma, erythrocytes, and urine, and their relationship to disease activity markers and pharmacological treatment.

We studied the status of copper and zinc in rheumatoid arthritis (RA). The aims of the work were to ascertain whether or not RA is associated with copper and/or zinc deficiency, to establish the relationship between these trace metals and the main biohumoral and clinical indices of the disease, and to examine the effect on copper and zinc of the drugs normally used by RA patients. Metal levels were measured by atomic absorption spectroscopy in the plasma, whole blood cells and 24 hr urine of 120 RA patients; 70 patients suffering from primary osteoarthritis were used as the control group. In the plasma of RA patients copper and ceruloplasmin levels were found to be significantly increased whereas zinc levels were significantly decreased. No major variations were observed in the blood cell and 24 hr urine copper and zinc levels. Plasma copper was significantly correlated with some of the biohumoral markers of RA, but did not correlate with any of the clinical indices of the disease. Plasma zinc was significantly correlated with numerous of the biohumoral as well as clinical markers of RA. With the exception of an increased urinary excretion of copper in D-penicillamine treated RA patients, drug therapy did not influence the copper status in RA. Conversely, plasma zinc was found to be lower in RA patients taking NSAIDs and/or steroids. These results suggest the following conclusions: i) RA patients do not seem to be deficient in either copper or zinc; ii) plasma copper appears to be a poor index of RA severity; iii) plasma zinc could have some practical value in defining the overall severity of the disease.

Reference values of tests for the assessment of mutagenic activity.

The determination of mutagenic activity in biological media aims at detecting the exposure to mutagenic chemicals, or to chemicals transformed by the organism into mutagenic metabolites. Mutagenic activity is detected by various short-term tests which rely upon the interaction of the chemical with the DNA of, bacteria, Drosophila or mammalian cells. The urinary fluctuation test has been particularly useful in determining mutagenic activity in the urine of subjects exposed to low concentrations of suspected genotoxic chemicals. The assay procedure itself is relatively simple, the data, however, should be carefully evaluated in relation to the attributes of the donor, bearing in mind the confounding variables related to life-style, diet, occupation and drug intake.