Orchids,bilateral symmetry and insect perception

The basic characteristics of orchids, possessing the greatest number of complex floral images of any Angiosperm family, are reviewed. Bilateral symmetry (zygomorphy) is shown by use of information theory techniques to give much greater possibilities for the transmission of visually mediated information than radial symmetry. The difference in information content is further enhanced by motion. The analysis is offered as evidence that the evolution of diversity in complex images, if effected by the unique behavioral specificity of pollinators known as “flower constancy”, is most economically explained by hypothesizing recognition and storage of the total image (“gestalt”) in the agents of natural selection.     

Inverse problem approach to regularized regression models with application to predicting recovery after stroke

Regression modelling is a powerful statistical tool often used in biomedical and clinical research. It could be formulated as an inverse problem that measures the discrepancy between the target outcome and the data produced by representation of the modelled predictors. This approach could simultaneously perform variable selection and coefficient estimation. We focus particularly on a linear regression issue, , where is the parameter of interest and its components are the regression coefficients. The inverse problem finds an estimate for the parameter , which is mapped by the linear operator to the observed outcome data . This problem could be conveyed by finding a solution in the affine subspace . However, in the presence of collinearity, high-dimensional data and high conditioning number of the related covariance matrix, the solution may not be unique, so the introduction of prior information to reduce the subset and regularize the inverse problem is needed. Informed by Huber's robust statistics framework, we propose an optimal regularizer to the regression problem. We compare results of the proposed method and other penalized regression regularization methods: ridge, lasso, adaptive-lasso and elastic-net under different strong hypothesis such as high conditioning number of the covariance matrix and high error amplitude, on both simulated and real data from the South London Stroke Register. The proposed approach can be extended to mixed regression models. Our inverse problem framework coupled with robust statistics methodology offer new insights in statistical regression and learning. It could open a new research development for model fitting and learning.     

Musculature,nervous system and glands of metasomal abdominal segments of the male of Nomia melanderi Ckll. (Hymenoptera,Apoidea)

Each muscle of the third metasomal segment of the male of Nomia melanderi Ckll. is described in detail. The points of attachment of each muscle are compared with their homologs in other pregenital segments and with their homologs in the female. The function desgnated for each muscle describes its action alone or in conjunction with other muscle(s). New names are given to genital muscles by referring in the name to their points of attachment. Each intratergal muscle has homologous points of attachment in the pregenital segments of both sexes. The median tergo-dorsoplical muscle of the seventh segment and the oblique tergo-dorsoplical muscle of the eighth segment have changed their points of attachment. The intrasternal muscles are modified to suit the needs of courtship and mating, thus they are different from their homologs in the female. The spiracular muscles are well developed in all segments except the eighth, where the sterno-spiracular muscle is absent. The extrinsic genital muscles are derived from the intrasternal muscles of the eighth and ninth segments. The parameral and volsellar muscles are reduced in number. The aedeagal muscles, except the aedeago-phallic, have retained similar points of attachment to those found in primitive Hymenoptera. The topography of the metasomal nervous system is reported in detail by following each nerve and nervule to its termination. The study shows that (at least in Nomia) the criterion of nerve-concentration should not be used alone to indicate evolutionary levels. To accommodate the morphological changes in the terminal segments the Anterior and Posterior Lateral Nerves have migrated to new locations. The pattern of nerve topography (even at the nervule level) is homologous both in the different pregenital segments and between the sexes. The fact that homology does not exist between the external genitalia of the male and the modified ovipositor of the female supports the thesis that the male genital capsule is of phallic rather than prephallic origin. A pair of intersegmental membrane glands located between the seventh and eighth sterna is described. These glands may be the source of a pheromon responsible for gregariousness among “sleeping” males.     

Downregulation of neutral ceramidase by gemcitabine: Implications for cell cycle regulation

Gemcitabine (GMZ) is a chemotherapeutic agent with well established effects on cell growth arrest and apoptosis. In this study, we investigated the potential roles of bioactive sphingolipids in mediating the growth suppressing effects of GMZ on a polyoma middle T transformed murine endothelial cell line. After 12-hour GMZ (0.6 μM) treatment, cell growth was arrested at the G₀/G₁ phase as detected by flow cytometric cell cycle analysis and MTT cell viability analysis, and this was accompanied by dephosphorylation of the retinoblastoma protein (Rb). Furthermore, GMZ treatment resulted in increased levels of specifically the very long chain ceramides as determined by mass spectrometry. Mechanistically, GMZ did not appear to affect the activities of many enzymes of ceramide metabolism; however, GMZ caused a selective reduction in the protein levels of neutral ceramidase (NCDase), as indicated by Western blot analysis, with a concomitant decrease in NCDase activity. The significance of NCDase loss on cell cycle regulation was investigated by specific knockdown of the enzyme using small interfering RNA (siRNA). Interestingly, NCDase siRNA transfection was sufficient to induce a cell cycle arrest at G₀/G₁ and an increase in total ceramide levels, with significant elevation in very long chain ceramides (C_24:1 and C_24:0). NCDase siRNA also induced Rb dephosphorylation. These data provide evidence for a novel mechanism of action for GMZ and highlight downregulation of NCDase as a critical step in GMZ-mediated ceramide elevation and cell cycle arrest.     

A complex immune response to flagellin epitope variation in commensal communities

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