Fine-scale habitat heterogeneity favours the coexistence of supergene-controlled social forms in Formica selysi.

Social insects vary widely in social organization, yet the genetical and ecological factors influencing this variation remain poorly known. In particular, whether spatially varying selection influences the maintenance of social polymorphisms in ants has been rarely investigated. To fill this gap, we examined whether fine-scale habitat heterogeneity contributes to the co-existence of alternative forms of social organization within populations. Single-queen colonies (monogyne social form) are generally associated with better colonization abilities, whereas multiple-queen colonies (polygyne social form) are predicted to be better competitors and monopolize saturated habitats. We hypothesize that each social form colonizes and thrives in distinct local habitats, as a result of their alternative dispersal and colony founding strategies. Here, we test this hypothesis in the Alpine silver ant, in which a supergene controls polymorphic social organization. Monogyne and polygyne colonies predominate in distinct habitats of the same population. The analysis of 59 sampling plots distributed across six habitats revealed that single-queen colonies mostly occupy unconnected habitats that were most likely reached by flight. This includes young habitats isolated by water and old habitats isolated by vegetation. In contrast, multiple-queen colonies were abundant in young, continuous and saturated habitats. Hence, alternative social forms colonize and monopolize distinct niches at a very local scale. Alternative social forms colonized and monopolized different local habitats, in accordance with differences in colonization and competition abilities. The monogyne social form displays a colonizer phenotype, by efficiently occupying empty habitats, while the polygyne social form exhibits a competitor phenotype, thriving in saturated habitats. The combination of the two phenotypes, coupled with fine-scale habitat heterogeneity, may allow the coexistence of alternative social forms within populations. Overall, these results suggest that spatially varying selection may be one of the mechanisms contributing to the maintenance of genetic polymorphisms in social organization

Localization of sequences related to the human RAD6 DNA repair gene on mouse Chromosomes 11 and 13

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47025/1/335_2004_Article_BF00352425.pd

DIESE Final Report

The DIESE program (Determination of relevant Indicators for Environmental monitoring: A Strategy for Europe) brought together seven French and British research teams, a private company and the agencies responsible for the management of water bodies of the two countries (ONEMA and the Environmental Agency) in a joint effort to document the ecotoxicological effects related to the presence of chemicals in the environment. To contribute to a better understanding and management of the environment, the program has expanded its efforts to (1) use existing knowledge, or new information acquired during the research program, to identify important biological problems affecting wildlife, (2) increase our understanding of toxicological mechanisms involved and thus be able to identify the causes of the identified dysfunctions and (3) to hone our expertise and vigilance systems in order to better monitor changes in the environment and make appropriate diagnoses. The first part of the program identified clear biological effects, and using biological tests representative of the mechanisms of action of compounds, identified the responsible compounds present in the environment. In connection with the feminization observed in many fish species in European streams, a search for estrogenic and anti-androgenic compounds was conducted. A new test identifying estrogenic compounds has been developed in roach and the ER-Calux test for anti-androgenic effects has been implemented. The results showed that, in addition to biocides such as triclosan and chlorophène, many aromatic hydrocarbon compounds are likely to disturb the physiology of living organisms by interacting with the androgen receptor. Six of these were identified in sediment extracts: benzanthrone, fluoranthene, 1,2- benzodiphenylene sulfide, benzo[a]pyrene, benz[a] anthracene, and 9-phenylcarbazole. The second part of the program aimed at documenting and understanding the mechanisms of action of chemicals leading to physiological changes. This work represents a particular challenge when dealing with molluscs, as knowledge about their physiology and endocrinology is still fragmentary. Thus, new technologies including metabolomic and transcriptomic analyses have been implemented in order to obtain a comprehensive picture of the effects on molluscs. Metabolomic research demonstrated that estrogenic compounds are able to alter the metabolism of eicosanoids and amines, while transcriptomic strategies identified genes whose expression is altered in intersex clams. Because these genes mainly appear as “male” genes, the results suggest that these profound physiological changes result from demasculinisation of male clams. Proteomic studies have also been carried out to elucidate the mechanisms of action of pollutants on fish physiology. These studies generally included a set of molecular marker measurements in an integrative and ecological perspective. The results showed that not only male fish physiology is altered but also female reproductive status is impaired. Moreover, it appeared that other alterations of the fish endocrine system, such as androgenic effects, are at work and that the immune system is also subject to chemical pressure including effects from environmental estrogens. Notably, the immune system, like the endocrine system, seems to show periods of particular sensitivity during development. Measurements on growth and on the general metabolism emphasize the importance of environmental conditions in the physiology of aquatic organisms and in particular the inter-site variability due to temperature,hypoxic conditions, and fish development strategies. They thus provide a unique perspective that allow us to better understand the context and consequences of natural conditions on the population. In a third part of the program, the research conducted had the objective of developing and testing a biomarker strategy to support the environmental management methodologies. Two lanes of specific studies have been followed. The first was to implement, over all or part of the study area, robust biomarkers to establish maps that highlight the water bodies at risk and provide information on sources of compounds and associated disturbances. The second part of the work aimed at exploring methodologies to take advantage of biomarker measurements and to integrate them in a very simple and clear index. Partial or comprehensive maps of the Channel area were produced to report the presence of mutagenic or anti-androgenic compounds in the sediments, intersex fish and clams, and imposex. These maps may remain to be completed and work will be necessary to confront this information in order to learn relevant lessons for management of the environment, a goal that the DIESE program has contributed to by providing some necessary and original information

Simultaneous acquisition of perfusion image and dynamic MR angiography using time-encoded pseudo-continuous ASL

Neuro Imaging Researc

Genomic characterization of the human DNA excision repair gene ERCC-1.

In this report the genomic characterization of the human excision repair gene ERCC-1 is presented. The gene consists of 10 exons spread over approximately 15 kb. By means of a transfection assay the ERCC-1 promoter was confined to a region of + 170 bp upstream of the transcriptional start site. Classical promoter elements like CAAT, TATA and GC-boxes are absent from this region. Furthermore, ERCC-1 transcription is not UV-inducible. A possible explanation is provided for the previously reported alternative splicing of exon VIII. Analysis of ERCC-1 cDNA clones revealed the occurrence of differential polyadenylation which gives ERCC-1 transcripts of 3.4 and 3.8 kb in addition to the major 1.1 kb mRNA. Apparent evolutionary conservation of differential polyadenylation of ERCC-1 transcripts suggests a possible role for this mode of RNA processing in the ERCC-1 repair function

Molecular characterization of the human excision repair gene ERCC-1: cDNA cloning and aminoacid homology with the yeast DNA repair gene RAD10.

The human excision repair gene ERCC-7 was cloned after DNA mediated gene transfer to the CHO mutant 43-38, which is sensitive to ultraviolet light and mitomycin-C. We describe the cloning and sequence analysis of the ERCC-7 cDNA and partial characterization of the gene. ERCC.1 has a size of 15 kb and is located on human chromosome 19. The ERCC.1 precursor RNA is subject to alternative splicing of an internal 72 bp coding exon. Only the cDNA of the larger 1.1 kb transcript, encoding a protein of 297 amino acids, was able to confer resistance to ultraviolet light and mitomycin-C on 43-38 cells. Significant amino acid sequence homology was found between the ERCC.7 gene product and the yeast excision repair protein RADIO. The most homologous region displayed structural homology with DNA binding domains of various polypeptides

Myelin water imaging from multi-echo T-2 MR relaxometry data using a joint sparsity constraint

Demyelination is the key pathological process in multiple sclerosis (MS). The extent of demyelination can be quantified with magnetic resonance imaging by assessing the myelin water fraction (MWF). However, long computation times and high noise sensitivity hinder the translation of MWF imaging to clinical practice. In this work, we introduce a more efficient and noise robust method to determine the MWF using a joint sparsity constraint and a pre-computed B-1(+)-T-2 dictionary.A single component analysis with this dictionary is used in an initial step to obtain a B-1(+) map. The T-2 distribution is then determined from a reduced dictionary corresponding to the estimated B-1(+) map using a combination of a non-negativity and a joint sparsity constraint.The non-negativity constraint ensures that a feasible solution with non-negative contribution of each T-2 component is obtained. The joint sparsity constraint restricts the T-2 distribution to a small set of T-2 relaxation times shared between all voxels and reduces the noise sensitivity.The applied Sparsity Promoting Iterative Joint NNLS (SPIJN) algorithm can be implemented efficiently, reducing the computation time by a factor of 50 compared to the commonly used regularized non-negative least squares algorithm. The proposed method was validated in simulations and in 8 healthy subjects with a 3D multiecho gradient- and spin echo scan at 3 T. In simulations, the absolute error in the MWF decreased from 0.031 to 0.013 compared to the regularized NNLS algorithm for SNR = 250. The in vivo results were consistent with values reported in literature and improved MWF-quantification was obtained especially in the frontal white matter. The maximum standard deviation in mean MWF in different regions of interest between subjects was smaller for the proposed method (0.0193) compared to the regularized NNLS algorithm (0.0266). In conclusion, the proposed method for MWF estimation is less computationally expensive and less susceptible to noise compared to state of the art methods. These improvements might be an important step towards clinical translation of MWF measurements.Neuro Imaging Researc