Psychology: red enhances human performance in contests

Red coloration is a sexually selected, testosterone-dependent signal of male quality in a variety of animals, and in some non-human species a male's dominance can be experimentally increased by attaching artificial red stimuli. Here we show that a similar effect can influence the outcome of physical contests in humans--across a range of sports, we find that wearing red is consistently associated with a higher probability of winning. These results indicate not only that sexual selection may have influenced the evolution of human response to colours, but also that the colour of sportswear needs to be taken into account to ensure a level playing field in sport.     

Influence of parental chromosomes on spatial specificity in androgenetic----parthenogenetic chimaeras in the mouse

The presence of both parental genomes is essential for development to term in the mouse embryo probably because of germline-specific modifications of homologous chromosomes. Neither androgenetic nor parthenogenetic embryos can by themselves develop to term; any post-implantation embryos they produce have opposite phenotypes, which reflects the presence of complementary information in parental chromosomes. The development of androgenetic----parthenogenetic chimaeras is of considerable interest because in this case both parental chromosomes are available even though they are in separate cells. We demonstrate here that in post-implantation chimaeric fetuses, the expression of parental information results in spatial specificity so that parthenogenetic cells are confined to the embryo but the trophoblast consists almost entirely of androgenetic cells. The yolk sac contains both cell types. However, there is incomplete functional complementation because the chimaeras do not reach term. Although failure to reach term may occur partly because of inadequate intermingling and interactions between embryonic cells, it is more likely that further control of mouse development depends on the presence of both sets of chromosomes within the same cells.     

Effect of dipyridamole and adenosine monophosphate on cell proliferation in the hemopoietic tissue of normal and gamma-irradiated mice

Combined treatment with dipyridamole and adenosine monophosphate enhances cell proliferation in the hemopoietic tissue of normal and gamma-irradiated mice. This effect can be explained by the elevation of extracellular adenosine, and the receptor-mediated activation of the cell adenylate cyclase system.     

The effect of a bradykinin antagonist on vasodilator responses with particular reference to the submandibular gland of the cat

Summary A bradykinin analogue, D-Arg[Hyp³, Thi^{5, 8}, D-Phe⁷]-Bk, antagonized the vasodilator effect of bradykinin injected close-arterially in the submandibular salivary gland of the cat, without affecting that due to acetylcholine or nerve stimulation. The same analogue also antagonized the hypotensive response to bradykinin injected intravenously in cats and rabbits. We conclude that functional hyperaemia in the submandibular gland of the cat is not due to the release of bradykinin by salivary kallikrein.     

Investigation of genetic linkage between myosin and actin genes using an interspecific mouse back-cross

The introduction of cloned probes to follow the segregation of DNA restriction fragment length polymorphisms (RFLPs) has led to a revival of mendelian genetics in attempts to map the human genome. In the mouse, however, it has often proved difficult to detect an RFLP with a DNA probe between different inbred strains of the laboratory mouse. To circumvent this problem, we have used two species, Mus musculus domesticus and Mus spretus which interact as sympatric species but can be interbred under laboratory conditions. Because of the relative evolutionary distance between these species, they exhibit polymorphism at many more loci than do different strains of the usual M. m. domesticus laboratory mouse. This is also observed at the DNA level when the sizes of restriction fragments encoding a specific gene are compared. We have used these RFLPs between M. m. domesticus and M. spretus to follow the segregation of genes encoding different isoforms of myosin alkali light chains in the backcross progeny between these species and to compare this with that of other contractile protein genes. No linkage between these genes was observed.     

Adaptation, speciation and hybrid zones

Many species are divided into a mosaic of genetically distinct populations, separated by narrow zones of hybridization. Studies of hybrid zones allow us to quantify the genetic differences responsible for speciation, to measure the diffusion of genes between diverging taxa, and to understand the spread of alternative adaptations.     

Evidence from three-dimensional seismic reflectivity images for enhanced melt supply beneath mid-ocean-ridge discontinuities

Quantifying the melt distribution and crustal structure across ridge-axis discontinuities is essential for understanding the relationship between magmatic, tectonic and petrologic segmentation of mid-ocean-ridge spreading centres. The geometry and continuity of magma bodies beneath features such as overlapping spreading centres can strongly influence the composition of erupted lavas and may give insight into the underlying pattern of mantle flow. Here we present three-dimensional images of seismic reflectivity beneath a mid-ocean ridge to investigate the nature of melt distribution across a ridge-axis discontinuity. Reflectivity slices through the 9 degrees 03' N overlapping spreading centre on East Pacific Rise suggest that it has a robust magma supply, with melt bodies underlying both limbs and ponding of melt beneath large areas of the overlap basin. The geometry of melt distribution beneath this offset is inconsistent with large-scale, crustal redistribution of melt away from centres of upwelling. The complex distribution of melt seems instead to be caused by a combination of vertical melt transport from the underlying mantle and subsequent focusing of melt beneath a magma freezing boundary in the mid-crust.     

Eomesodermin is required for mouse trophoblast development and mesoderm formation

The earliest cell fate decision in the mammalian embryo separates the extra-embryonic trophoblast lineage, which forms the fetal portion of the placenta, from the embryonic cell lineages. The body plan of the embryo proper is established only later at gastrulation, when the pluripotent epiblast gives rise to the germ layers ectoderm, mesoderm and endoderm. Here we show that the T-box gene Eomesodermin performs essential functions in both trophoblast development and gastrulation. Mouse embryos lacking Eomesodermin arrest at the blastocyst stage. Mutant trophoectoderm does not differentiate into trophoblast, indicating that Eomesodermin may be required for the development of trophoblast stem cells. In the embryo proper, Eomesodermin is essential for mesoderm formation. Although the specification of the anterior-posterior axis and the initial response to mesoderm-inducing signals is intact in mutant epiblasts, the prospective mesodermal cells are not recruited into the primitive streak. Our results indicate that Eomesodermin defines a conserved molecular pathway controlling the morphogenetic movements of germ layer formation and has acquired a new function in mammals in the differentiation of trophoblast.