Distribution and conservation of mobile elements in the genus Drosophila

Essentially nothing is known of the origin, mode of transmission, and evolution of mobile elements within the genus Drosophila. To better understand the evolutionary history of these mobile elements, we examined the distribution and conservation of homologues to the P, I, gypsy, copia, and F elements in 34 Drosophila species from three subgenera. Probes specific for each element were prepared from D. melanogaster and hybridized to genomic DNA. Filters were washed under conditions of increasing stringency to estimate the similarity between D. melanogaster sequences and their homologues in other species. The I element homologues show the most limited distribution of all elements tested, being restricted to the melanogaster species group. The P elements are found in many members of the subgenus Sophophora but, with the notable exception of D. nasuta, are not found in the other two subgenera. Copia-, gypsy-, and F-element homologues are widespread in the genus, but their similarity to the D. melanogaster probe differs markedly between species. The distribution of copia and P elements and the conservation of the gypsy and P elements is inconsistent with a model that postulates a single ancient origin for each type of element followed by mating-dependent transmission. The data can be explained by horizontal transmission of mobile elements between reproductively isolated species.      

Role of the reticulum in the stability and shape of the isolated human erythrocyte membrane

In order to examine the widely held hypothesis that the reticulum of proteins which covers the cytoplamsic surface of the human erythrocyte membrane controls cell stability and shape, we have assessed some of its properties. The reticulum, freed of the bilayer by extraction with Triton X-100, was found to be mechanically stable at physiological ionic strength but physically unstable at low ionic strength. The reticulum broke down after a characteristic lag period which decreased 500-fold between 0 degrees and 37 degrees C. The release of polypeptide band 4.1 from the reticulum preceded that of spectrin and actin, suggesting that band 4.1 might stabilize the ensemble but is not essential to its integrity. The time-course of breakdown was similar for ghosts, the reticulum inside of ghosts, and the isolated reticulum. However, at very low ionic strength, the reticulum was less stable within the ghost than when free; at higher ionic strength, the reverse was true. Over a wide range of conditions the membrane broke down to vesicles just as the reticulum disintegrated, presumably because the bilayer was mechanically stabilized by this network. The volume of both ghosts and naked reticula varied inversely and reversibly with ionic strength. The volume of the naked reticulum varied far more widely than the ghost, suggesting that its deformation was normally limited by the less extensible bilayer. The contour of the isolated reticulum was discoid and often dimpled or indented, as visualized in the fluorescence microscope after labeling of the ghosts with fluoroscein isothiocyanate. Reticula derived from ghosts which had lost the ability to crenate in isotonic saline were shriveled, even though the bilayer was smooth and expanded. Conversly, ghosts crenated by dinitrophenol yielded smooth, expanded reticula. We conclude that the reticulum is a durable, flexible, and elastic network which assumes and stabilizes the contour of the membrane but is not responsible for its crenation.     

Variation in the harvest index of tropical maize: evaluation of recent evidence from Mexico and Malawi

In temperate zones, the potential grain yield of wheat has increased during the twentieth century owing to progressive increases in the harvest index of new varieties, which are principally associated with reduction in plant stature. Crop biomass has not increased substantially. In contrast, the potential grain yield of maize in the USA has increased owing to progressive increases in biomass, principally associated with selection for grain yield at higher population density. Harvest index was already around 0.5 for recommended varieties in 1930, and has not increased significantly since. However, for both crops, the harvest index of a given variety has proved to be a highly‐heritable character, except under severe stress. Less is known about the physiology of tropical maize. This paper reviews evidence from Mexico and Malawi that tropical maize can respond to selection for reduced stature following the same pattern as temperate wheat, but, under other circumstances, the magnitude of harvest index is not highly heritable, varying inconsistently with season, management and environment. It is proposed that these differences arise out of the unique vulnerability of the grain‐setting process around flowering. The plasticity of harvest index under long, favourable conditions, however, remains to be explained, although it is probably also related to the events around grain setting. Nevertheless, to the subsistence farmer, higher harvest index may not be a high priority in crop improvement, because of the need for large quantities of high‐quality stover.     

Morphological Constraints of Shoot Demography of a Clonal Plant: Extra- and Intravaginal Tillers of Festuca rubra

Abstract Festuca rubra forms tillers in two different ways: extravaginally and intravaginally. Demography of these two tiller types was observed in seventeen selected tussocks of Festuca rubra s.s. over four growing seasons. Extravaginal tillers were bigger at birth and on the average produced twice as many daughter tillers per tiller. In general, the natality and mortality of extravaginal tillers were less regular than that of intravaginal tillers. Overall tillering rate per tiller was correlated with the density of the surrounding vegetation; mortality, natality and tiller life span were not. High density of the surrounding vegetation did not result in increased formation of extravaginal tillers. The proportion of the extravaginal tillers was not correlated with the density of the F. rubra tussocks. There is no evidence for foraging by extravaginal tillers, but they do act as founders of small clusters of tillers.     

A basal sphenodontian (Lepidosauria) from the Jurassic of Patagonia: new insights on the phylogeny and biogeography of Gondwanan rhynchocephalians

Herein we describe a new rhynchocephalian taxon from the Middle Jurassic of Patagonia, Argentina, representing the first Jurassic record of the group in South America. The new taxon, consisting of a complete dentary, is ascribed to Sphenodontia based on the presence of a deep and wide Meckelian groove, long posterior process, well‐developed coronoid process, and acrodont teeth showing dental regionalization including successional, alternate hatchling, and additional series. This allocation is reinforced by a phylogenetic analysis that places the new taxon in a basal position within a clade of sphenodontians that excludes Diphydontosaurus and Planocephalosaurus. Additionally, the new taxon clusters within a Gondwanan clade with the Indian Godavarisaurus from the Jurassic Kota Formation, sharing the presence of recurved and relatively large posterior successional teeth that are ribbed and bear a peculiar anterolingual groove. This sister‐group relationship is intriguing from a palaeobiogeographical viewpoint, as it suggests some degree of endemism during the initial stages of the breakup of Pangaea. We also discuss the ontogenetic stage of the new taxon and provide insights on the evolution of successional dentition in rhynchocephalians. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166 , 342–360.     

Synthesis and Characterization of Novel Quinazoline Type Inhibitors for Mutant and Wild-Type EGFR and RICK Kinases

The development of selective protein kinase inhibitors has become an important area of drug discovery for the treatment of different diseases. We report the synthesis and characterization of a series of novel quinazoline derivatives against three therapeutically important and pharmacologically related kinases: 1) epidermal growth factor receptor (EGFR; wild type and mutant) in the field of cancer, 2) receptor-interacting caspase-like apoptosis-regulatory kinase (RICK) in the field of inflammation, and 3) pUL97 of human cytomegalovirus (HCMV). For reference purpose we have synthesized the four clinically relevant quinazolines, including the lead compounds, which we previously identified for RICK and pUL97. A total of 52 quinazoline derivatives were synthesized and tested on the basis of these leads to specifically target the hydrophobic pocket of the ATP-binding site. Selected compounds were tested on wild-type and mutant forms of EGFR, RICK, and pUL97 kinases; their logP and logS values for assessing suitability as drugs were calculated and hit or lead compounds identified.     

Transcriptomic response to differentiation induction

Background  

Microarrays used for gene expression studies yield large amounts of data. The processing of such data typically leads to lists of differentially-regulated genes. A common terminal data analysis step is to map pathways of potentially interrelated genes.