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Determination System (determination + system)

Distribution by Scientific Domains
Life Sciences66%

Kinds of Determination System

  • sex determination system
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    Selected Abstracts

    High temperature causes masculinization of genetically female medaka by elevation of cortisol

    MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 8 2010
    Yuki Hayashi
    In poikilothermic vertebrates, sex determination is sometimes influenced by environmental factors such as temperature. However, little is known about the molecular mechanisms underlying environmental sex determination. The medaka (Oryzias latipes) is a teleost fish with an XX/XY sex determination system. Recently, it was reported that XX medaka can be sex-reversed into phenotypic males by high water temperature (HT; 32,34°C) treatment during the sex differentiation period. Here we report that cortisol caused female-to-male sex reversal and that metyrapone (an inhibitor of cortisol synthesis) inhibited HT-induced masculinization of XX medaka. HT treatment caused elevation of whole-body levels of cortisol, while metyrapone suppressed the elevation by HT treatment during sexual differentiation. Moreover, cortisol and 33°C treatments inhibited female-type proliferation of germ cells as well as expression of follicle-stimulating hormone receptor (fshr) mRNA in XX medaka during sexual differentiation. These results strongly suggest that HT induces masculinization of XX medaka by elevation of cortisol level, which, in turn, causes suppression of germ cell proliferation and of fshr mRNA expression. Mol. Reprod. Dev. 77: 679,686, 2010. © 2010 Wiley-Liss, Inc. [source]

    Reproductive parameters vary with social and ecological factors in the polygynous ant Formica exsecta

    OIKOS, Issue 4 2008
    Rolf Kümmerli
    Due to their haplo-diploid sex determination system and the resulting conflict over optimal sex allocation between queens and workers, social Hymenoptera have become important model species to study variation in sex allocation. While many studies indeed reported sex allocation to be affected by social factors such as colony kin structure or queen number, others, however, found that sex allocation was impacted by ecological factors such as food availability. In this paper, we present one of the rare studies that simultaneously investigated the effects of social and ecological factors on social insect nest reproductive parameters (sex and reproductive allocation, nest productivity) across several years. We found that the sex ratio was extremely male biased in a polygynous (multiple queens per nest) population of the ant Formica exsecta. Nest-level sex allocation followed the pattern predicted by the queen-replenishment hypothesis, which holds that gynes (new queens) should only be produced and recruited in nests with low queen number (i.e. reduced local resource competition) to ensure nest survival. Accordingly, queen number (social factor) was the main determinant on whether a nest produced gynes or males. However, ecological factors had a large impact on nest productivity and therefore on a nest's resource pool, which determines the degree of local resource competition among co-breeding queens and at what threshold in queen number nests should switch from male to gyne production. Additionally, our genetic data revealed that gynes are recruited back to their parental nests after mating. However, our genetic data are also consistent with some adult queens dispersing on foot from nests where they were produced to nests that never produced queens. As worker production is reduced in gyne-producing nests, queen migration might be offset by workers moving in the other direction, leading to a nest network characterized by reproductive division of labour. Altogether our study shows that both, social and ecological factors can influence long-term nest reproductive strategies in insect societies. [source]

    Robust unscented Kalman filtering for nonlinear uncertain systems

    ASIAN JOURNAL OF CONTROL, Issue 3 2010
    K. Xiong
    Abstract A derivative-free robust Kalman filter algorithm is proposed for nonlinear uncertain systems. The unscented transform (UT) is adopted instead of the linearization technique to obtain the solution of the H, filter Riccati equation. A robust unscented Kalman filter (RUKF) is derived to guarantee an optimized upper bound on the estimation error covariance despite the model uncertainties and the approximation error of the UT. The proposed algorithm is applied to a satellite attitude determination system. Simulation results show that the RUKF is more effective than the unscented Kalman filter (UKF) in cases where alignment errors are present. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]

    Sex determination in fish: Lessons from the sex-determining gene of the teleost medaka, Oryzias latipes

    DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 5-6 2003
    Masaru Matsuda
    Although sex determination systems in animals are diverse, sex-determining genes have been identified only in mammals and some invertebrates. Recently, DMY (DM domain gene on the Y chromosome) has been found in the sex-determining region on the Y chromosome of the teleost medaka fish, Oryzias latipes. Functional and expression analyses of DMY show it to be the leading candidate for the male-determining master gene of the medaka. Although some work is required to define DMY as the master sex-determining gene, medaka is expected to be a good experimental animal for investigating the precise mechanisms involved in primary sex determination in non-mammalian vertebrates. In this article, the process of identification of DMY and is summarized and the origins of DMY and sexual development of the medaka's gonads are reviewed. In addition, putative functions of DMY are discussed. [source]

    Subscriber data management in IMS networks

    BELL LABS TECHNICAL JOURNAL, Issue 4 2006
    Daniel F. Lieuwen
    Next-generation communication services will be driven by increasingly rich and distributed subscriber information. Current wireless networks have evolved such that subscriber information now resides in various elements (e.g., home location register [HLR], prepay, voice mail, short message, and location determination systems). Convergence with the Internet promises significantly more personal information, such as presence, calendars, address books, buddy lists, pictures, and video. The home subscriber server (HSS) in the IP Multimedia Subsystem (IMS) architecture provides centralized storage for subscriber data. However, some application servers will also have their own subscriber data. As the quantity and variety of applications grow, it will become increasingly useful to provide unified views of subscriber data both within a network and across networks. The Lucent DatagridŌ software provides a telecom-targeted data integration capability, so that applications can use a logical "single-point-of-access" for user profile information inside a service provider's network. © 2006 Lucent Technologies Inc. [source]

    Constraints on the evolution of asexual reproduction

    BIOESSAYS, Issue 11-12 2008
    Jan Engelstädter
    Sexual reproduction is almost ubiquitous among multicellular organisms even though it entails severe fitness costs. To resolve this apparent paradox, an extensive body of research has been devoted to identifying the selective advantages of recombination that counteract these costs. Yet, how easy is it to make the transition to asexual reproduction once sexual reproduction has been established for a long time? The present review approaches this question by considering factors that impede the evolution of parthenogenesis in animals. Most importantly, eggs need a diploid chromosome set in most species in order to develop normally. Next, eggs may need to be activated by sperm, and sperm may also contribute centrioles and other paternal factors to the zygote. Depending on how diploidy is achieved mechanistically, further problems may arise in offspring that stem from ,inbreeding depression' or inappropriate sex determination systems. Finally, genomic imprinting is another well-known barrier to the evolution of asexuality in mammals. Studies on species with occasional, deficient parthenogenesis indicate that the relative importance of these constraints may vary widely. The intimate evolutionary relations between haplodiploidy and parthenogenesis as well as implications for the clade selection hypothesis of the maintenance of sexual reproduction are also discussed. BioEssays 30:1138,1150, 2008. © 2008 Wiley Periodicals, Inc. [source]