Characterization and evolution of a single-copy sequence from the human Y chromosome.

To study the evolution and organization of DNA from the human Y chromosome, we constructed a recombinant library of human Y DNA by using a somatic cell hybrid in which the only cytologically detectable human chromosome is the Y. One recombinant (4B2) contained a 3.3-kilobase EcoRI single-copy fragment which was localized to the proximal portion of the Y long arm. Sequences homologous to this human DNA are present in male gorilla, chimpanzee, and orangutan DNAs but not in female ape DNAs. Under stringent hybridization conditions, the homologous sequence is either a single-copy or a low-order repeat in humans and in the apes. With relaxed hybridization conditions, this human Y probe detected several homologous DNA fragments which are all derived from the Y in that they occur in male DNAs from humans and the apes but not in female DNAs. In contrast, this probe hybridized to highly repeated sequences in both male and female DNAs from old world monkeys. Thus, sequences homologous to this probe underwent a change in copy number and chromosomal distribution during primate evolution.     

Excess amino acid polymorphism in mitochondrial DNA: contrasts among genes from Drosophila, mice, and humans

Recent studies of mitochondrial DNA (mtDNA) variation in mammals and Drosophila have shown an excess of amino acid variation within species (replacement polymorphism) relative to the number of silent and replacement differences fixed between species. To examine further this pattern of nonneutral mtDNA evolution, we present sequence data for the ND3 and ND5 genes from 59 lines of Drosophila melanogaster and 29 lines of D. simulans. Of interest are the frequency spectra of silent and replacement polymorphisms, and potential variation among genes and taxa in the departures from neutral expectations. The Drosophila ND3 and ND5 data show no significant excess of replacement polymorphism using the McDonald-Kreitman test. These data are in contrast to significant departures from neutrality for the ND3 gene in mammals and other genes in Drosophila mtDNA (cytochrome b and ATPase 6). Pooled across genes, however, both Drosophila and human mtDNA show very significant excesses of amino acid polymorphism. Silent polymorphisms at ND5 show a significantly higher variance in frequency than replacement polymorphisms, and the latter show a significant skew toward low frequencies (Tajima's D = -1.954). These patterns are interpreted in light of the nearly neutral theory where mildly deleterious amino acid haplotypes are observed as ephemeral variants within species but do not contribute to divergence. The patterns of polymorphism and divergence at charge-altering amino acid sites are presented for the Drosophila ND5 gene to examine the evolution of functionally distinct mutations. Excess charge-altering polymorphism is observed at the carboxyl terminal and excess charge-altering divergence is detected at the amino terminal. While the mildly deleterious model fits as a net effect in the evolution of nonrecombining mitochondrial genomes, these data suggest that opposing evolutionary pressures may act on different regions of mitochondrial genes and genomes.      

Selenoprotein P associates with endothelial cells in rat tissues

 Selenoprotein P is an extracellular heparin-binding protein that has been implicated in protecting the liver against oxidant injury. Its location in liver, kidney, and brain was determined by conventional immunohistochemistry and confocal microscopy using a polyclonal antiserum. Selenoprotein P is associated with endothelial cells in the liver and is more abundant in central regions than in portal regions. It is also present in kidney glomeruli associated with capillary endothelial cells. Staining of selenoprotein P in the brain is also confined to vascular endothelial cells. The heparin-binding properties of selenoprotein P could be the basis for its binding to tissue. Its localization to the vicinity of endothelial cells is potentially relevant to its oxidant defense function. Accepted: 6 March 1997     

Characterization of a chemotactic and cytotoxic proteinase from human skin.

A proteinase (EC 3.4.-.-) active at physiological pH has been isolated from human skin utilizing gel filtration and affinity chromatography techniques. The proteinase has a molecular weight of approx. 28 000 and it is inhibited by alpha 2-macroglobulin, alpha 1-antitrypsin, C-1 inactivatory, soybean trypsin inhibitor and diisopropyl fluorophosphate. 2njection of 1 ng of purified proteinase into rabbit skin induces polymorphonuclear leukocyte infiltration of the cutis. Inhibition of enzyme activity with diisopropyl fluorophosphate inhibits the chemotactic effect. Addition of 0.2 microgram/ml of purified proteinase to fibroblast cultures kills the cells within minutes. This proteinase may play a significant role in modulating the inflammatory response after cellular injury.     

Dominance hierarchies and the evolution of "individual recognition"

Stable dominance hierarchies may form for a variety of reasons. Assessment of the probable outcome of future encounters is likely to be the best way of economizing energy and risk of injury. Where assessment involves taking into account physical or behavioural characteristics of opponents, an arms race will develop between genuinely high status individuals and cheats possessing high status cues. Successive addition of reference cues may result ending either in a complex series of assessment cues or in cues which are status-limited. No distinction can be drawn between assessment involving so-called individual recognition and that involving “simpler” cues.