A cost of cryptic female choice in the yellow dung fly

Female dung flies Scathophaga stercoraria (L.) store sperm from several males in three or four spermathecae. Selection on the number of spermathecae was successful and the morphological intermediate stages in the evolution from three to four spermathecae are illustrated. The genetic quality of a male from a female's perspective depends on an interaction between their genotypes and the microhabitat in which the offspring will grow. Females influence the paternity pattern of their offspring, and do this differently in different microhabitats. Females with four spermathecae are better able to influence paternity than are those with three spermathecae. However, there must be a cost to building and maintaining an extra spermatheca. We estimate, using the animal model on pedigree data, that this cost is approximately five eggs per clutch, i.e. around 8% of the mean clutch size. This is a substantial cost and such costs should not be ignored in discussions of the benefits to females of assessing the genetic qualities of their mating partners. We suggest that the number of spermathecae in the study population is stable because the relative benefits in quality of offspring through cryptic female choice is balanced by the costs in total numbers of offspring.     

Protein-sphingolipid interactions within cellular membranes

Each intracellular organelle critically depends on maintaining its specific lipid composition that in turn contributes to the biophysical properties of the membrane. With our knowledge increasing about the organization of membranes with defined microdomains of different lipid compositions, questions arise regarding the molecular mechanisms that underlie the targeting to/segregation from microdomains of a given protein. In addition to specific lipid-transmembrane segment interactions as a basis for partitioning, the presence in a given microdomain may alter the conformation of proteins and, thus, the activity and availability for regulatory modifications. However, for most proteins, the specific lipid environment of transmembrane segments as well as its relevance to protein function and overall membrane organization are largely unknown. To help fill this gap, we have synthesized a novel photoactive sphingolipid precursor that, together with a precursor for phosphoglycerolipids and with photo-cholesterol, was investigated in vivo with regard to specific protein transmembrane span-lipid interactions. As a proof of principle, we show specific labeling of the ceramide transporter with the sphingolipid probe and describe specific in vivo interactions of lipids with caveolin-1, phosphatidylinositol transfer protein beta, and the mature form of nicastrin. This novel photolabile sphingolipid probe allows the detection of protein-sphingolipid interactions within the membrane bilayer of living cells.     

From rio to johannesburg — a business perspective the 7th international business forum

Conclusions  When we take stock of developments in the decade since the 1992 United Nations Conference on Environment and Development in Rio de Janeiro, we see a diverse picture with hopeful and promising steps in the right direction, but also reasons to be concerned.     

Egg sex ratio and paternal traits: using within-individual comparisons

Empirical studies of sex ratios in birds have been limited dueto difficulties in determining offspring sex. Since molecularsexing techniques removed this constraint, the last 5 yearshas seen a great increase in studies of clutch sex ratio manipulationby female birds. Typically these studies investigate variationin clutch sex ratios across individuals in relation to environmentalcharacteristics or parental traits, and often they find no relationships. In this study we also found that clutch sex ratiosdid not vary in relation to a number of biological and environmentalfactors for 238 great tit Parus major nests. However, interestingsex ratio biases were revealed when variation in clutch sexratios was analyzed within individual females breeding in successiveyears. There was a significant positive relationship betweenthe change in sex ratio of a female's clutch from one yearto the next and the relative body condition of her partner.Females mating with males of higher body condition in yearx + 1 produced relatively male-biased sex ratios, and the oppositewas true for females mated with lower condition males. Within-individualanalysis also allowed investigations of sex ratio in relationto partner change. There was no change in sex ratios of femalespairing with the same male; however, females pairing with anew male produced clutches significantly more female biased. Comparisons of clutch sex ratios within individuals may be apowerful method for detecting sex ratio variation, and perhapsfemale birds may indeed manipulate egg sex but require personalcontextual experience for such decisions.     

Random screening of proteins for HLA-A*0201-binding nine-amino acid peptides is not sufficient for identifying CD8 T cell epitopes recognized in the context of HLA-A*0201

HLA-A2 is the most frequent HLA molecule in Caucasians with HLA-A*0201 representing the most frequent allele; it was also the first human HLA allele for which peptide binding prediction was developed. The Bioinformatics and Molecular Analysis Section of the National Institutes of Health (BIMAS) and the University of Tübingen (Syfpeithi) provide the most popular prediction algorithms of peptide/MHC interaction on the World Wide Web. To test these predictions, HLA-A*0201-binding nine-amino acid peptides were searched by both algorithms in 19 structural CMV proteins. According to Syfpeithi, the top 2% of predicted peptides should contain the naturally presented epitopes in 80% of predictions (www.syfpeithi.de). Because of the high number of predicted peptides, the analysis was limited to 10 randomly chosen proteins. The top 2% of peptides predicted by both algorithms were synthesized corresponding to 261 peptides in total. PBMC from 10 HLA-A*0201-positive and CMV-seropositive healthy blood donors were tested by ex vivo stimulation with all 261 peptides using crossover peptide pools. IFN-gamma production in T cells measured by CFC was used as readout. However, only one peptide was found to be stimulating in one single donor. As a result of this work, we report a potential new T cell target protein, one previously unknown CD8-T cell-stimulating peptide, and an extensive list of CMV-derived potentially strong HLA-A*0201-binding peptides that are not recognized by T cells of HLA-A*0201-positive CMV-seropositive donors. We conclude that MHC/peptide binding predictions are helpful for locating epitopes in known target proteins but not necessarily for screening epitopes in proteins not known to be T cell targets.