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.     

Interactions ofCandida albicans with bacteria and salivary molecules in oral biofilms

The yeastCandida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells.C. albicans andCandida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind toStreptococcus gordonii NCTC 7869 while two otherCandida species (Candida krusei andCandida kefyr) do not. Adherence ofC. albicans was greatest when the yeast had been grown at 30° C to mid-exponential growth phase. For 21 strains ofC. albicans there was a positive correlation between the ability to adhere toS. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence ofC. albicans toS. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins ofC. albicans are co-expressed.     

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.     

Adherent cells in tumor immunity

The present studies explored the role of adherent cells in tumor immunity. Lymph node cells from mice bearing large tumors appeared to be maximally stimulated in vivo and incapable of further stimulation by cells of the same tumor in vitro. Removal of the adherent cell population resulted in a marked decrease in the spontaneous background activity of the remaining nonadherent cells and allowed these cells to undergo stimulation when cultured in the presence of mitomycin-blocked tumor cells. The role of the adherent cell in the maintenance of a state of continuous stimulation was further elucidated by experiments in which lymph node cell populations were reconstituted from the adherent and nonadherent subpopulations. It was also shown that adherent lymphoid cells from tumor-bearing mice, but not from normal mice, were capable of stimulating tumor-immune lymphocytes in a manner similar to intact mitomycin-blocked tumor cells.