The effects of ingesting plant hormones on schistosomiasis in mice: An experimental study

A number of studies have shown that primates monitor and select plant species in their diet as a function of their secondary compound composition. The possibility also exists that secondary compounds, when used in appropriate concentrations, may have a beneficial, medicinal aspect. In this regard, synthesis of a variety of data suggested a connection between selection of Balanites by Ethiopian baboons, and the distribution of schistosomiasis. To test the hypothesis that the secondary compounds in Balanites might be selected for ‘medicinal purposes’, we conducted an experiment on the effect of adding the active principle, diosgenin, to the food of schistosome-infected mice. The hypothesis was that this steroidal saponin might alter the host's hormonal milieu, making a less hospitable environment for the adult schistosomes. Sacrifice of the mice showed diosgenin-fed animals to have an augmented rather than decreased response to the disease. However, the data support the developing literature that shows that the host's hormonal environment has a major effect on the parasitic diseases they are subject to, and that the hormonal environment can be dramatically influenced by the secondary compounds in the diet.     

Elf5 is essential for early embryogenesis and mammary gland development during pregnancy and lactation

Elf5 is an epithelial-specific ETS factor. Embryos with a null mutation in the Elf5 gene died before embryonic day 7.5, indicating that Elf5 is essential during mouse embryogenesis. Elf5 is also required for proliferation and differentiation of mouse mammary alveolar epithelial cells during pregnancy and lactation. The loss of one functional allele led to complete developmental arrest of the mammary gland in pregnant Elf5 heterozygous mice. A quantitative mRNA expression study and Western blot analysis revealed that decreased expression of Elf5 correlated with the downregulation of milk proteins in Elf5(+/-) mammary glands. Mammary gland transplants into Rag(-/-) mice demonstrated that Elf5(+/-) mammary alveolar buds failed to develop in an Elf5(+/+) mammary fat pad during pregnancy, demonstrating an epithelial cell autonomous defect. Elf5 expression was reduced in Prolactin receptor (Prlr) heterozygous mammary glands, which phenocopy Elf5(+/-) glands, suggesting that Elf5 and Prlr are in the same pathway. Our data demonstrate that Elf5 is essential for developmental processes in the embryo and in the mammary gland during pregnancy.     

The evolution of Queensland spiny mountain crayfish of the genus Euastacus. I. Testing vicariance and dispersal with interspecific mitochondrial DNA

The upland mesic rainforests of eastern Australia have been described as a "mesothermal archipelago" where a chain of cool mountain "islands" arise from a warm "sea" of tropical and subtropical lowlands. An endemic freshwater crayfish belonging to the genus Euastacus is found on each of these mountain "islands." The Euastacus are particularly suitable for the study of evolution because each mountain harbors a unique species, there are many taxa present providing replication within the group and, most importantly, their distribution is linear, extending along a south-north axis. This group could have evolved by "simultaneous vicariance" where there was one vicariant separation event of a widespread ancestor, or by "south to north stepping stone dispersal" where there were long distance dispersal events from neighboring mountain islands, starting in the south and proceeding north in a dispersal-colonization wave. We used pairwise genetic distances between nearest geographic neighbors as a novel way to test the two hypotheses. If diversification was due to "south to north stepping stone dispersal," then pairwise genetic distances between nearest geographic neighbors should decrease progressively the farther north the taxon pairs are found, reflecting the decreasing periods of isolation. In this case there should be a negative correlation between the south to north rank order of nearest neighbors and pairwise genetic distances. A Spearman's correlation on 16S mtDNA pairwise genetic distances and geographic rank order was not significant, indicating there was no support for the south to north stepping stone dispersal hypothesis. If simultaneous vicariance was responsible for diversification then all nearest geographic neighbor taxon pairs should have similar genetic distances and, therefore, the variance in nearest neighbor distances should be zero, or close to it. To test if the observed variance was tending towards zero we developed a randomization test where nearest neighbor taxon pairs were assigned random genetic distances and the variances calculated. The observed variance lay in the < 0.05 range of the simulated variances, providing support for the simultaneous vicariance hypothesis. The data also suggest there was simultaneous vicariance of at least two ancestral Queensland lineages. The timing of this vicariant event was probably in the Pliocene, which is consistent with the divergence times reported for other Australian mesic rainforest restricted taxa.     

Multiple stressors on biotic interactions: how climate change and alien species interact to affect pollination

Global change may substantially affect biodiversity and ecosystem functioning but little is known about its effects on essential biotic interactions. Since different environmental drivers rarely act in isolation it is important to consider interactive effects. Here, we focus on how two key drivers of anthropogenic environmental change, climate change and the introduction of alien species, affect plant–pollinator interactions. Based on a literature survey we identify climatically sensitive aspects of species interactions, assess potential effects of climate change on these mechanisms, and derive hypotheses that may form the basis of future research. We find that both climate change and alien species will ultimately lead to the creation of novel communities. In these communities certain interactions may no longer occur while there will also be potential for the emergence of new relationships. Alien species can both partly compensate for the often negative effects of climate change but also amplify them in some cases. Since potential positive effects are often restricted to generalist interactions among species, climate change and alien species in combination can result in significant threats to more specialist interactions involving native species.     

Control of desmosome formation in aggregating embryonic chick cells

Corneal epithelial cells have been used to study cell surface changes during cell aggregation. Tissue was taken from developmental stages in which desmosomes were forming rapidly. When corneal cells are dispersed, adjacent desmosome plaques are separated and single plaques are left on the cell surface. As cells aggregate, changes in the frequency of single plaques or of full desmosomes (double plaques) per micrometer of cell surface cross section can be followed. Single plaques are lost from the surface by endocytosis. Quantitative studies show a loss of single plaques beginning in the first hour of culture and formation of double plaques at 2 to 3 hr. In cells treated with cytochalasin B or D, single plaques are not lost during the first 2 hr and double plaques form with a higher frequency. Formation of double plaques is suppressed by actinomycin D, cycloheximide, and dinitrophenol. Thus desmosome formation requires de novo protein synthesis. In addition, inhibition of cell surface turnover by drugs which modify the cytoskeleton will enhance the rate at which desmosomes form.     

A novel yeast expression system for the overproduction of quality-controlled membrane proteins

Saturation of the cell's protein folding capacity and accumulation of inactive incompletely folded protein often accompanying the overexpression of membrane proteins (MPs) presents an obstacle to their efficient purification in a functional form for structural studies. We present a novel strategy for optimization of functional MP expression in Saccharomyces cerevisiae. This approach exploits the unfolded protein response (UPR) pathway, a stress signaling mechanism that senses the accumulation of unfolded proteins in the endoplasmic reticulum. We demonstrate that a high level of UPR induction upon expression of a MP reflects impaired functional expression of that protein. Tuning the expression level of the protein so as to avoid or minimize UPR induction results in its increased functional expression. UPR status can therefore serve as a proxy variable for the extent of impaired expression of a MP that may even be applicable in the absence of knowledge of the protein's biological function.     

Diversification in insular plants: inferring the phylogenetic relationship in Aeonium (Crassulaceae) using ITS sequences of nuclear ribosomal DNA

The ITS regions of nuclear ribosomal DNA were sequenced in 37 species of the genus Aeonium . A phylogeny obtained through the use of parsimony agrees to some extent with the sectional division of the genus and confirms the position of two newly described species. It also suggests the potential importance of reticulate evolution in the genus. Based on the geographic distribution of this particular island group and the growth forms of its species, dispersal across similar ecological zones of different islands followed by adaptive radiation and isolation are suggested to be the prominent routes in speciation. As is typical of island genera, large polytomies at the distal nodes in the phylogeny indicate a recent rapid radiation.