1,859 research outputs found

    Is there a role for carbohydrate restriction in the treatment and prevention of cancer?

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    Over the last years, evidence has accumulated suggesting that by systematically reducing the amount of dietary carbohydrates (CHOs) one could suppress, or at least delay, the emergence of cancer, and that proliferation of already existing tumor cells could be slowed down. This hypothesis is supported by the association between modern chronic diseases like the metabolic syndrome and the risk of developing or dying from cancer. CHOs or glucose, to which more complex carbohydrates are ultimately digested, can have direct and indirect effects on tumor cell proliferation: first, contrary to normal cells, most malignant cells depend on steady glucose availability in the blood for their energy and biomass generating demands and are not able to metabolize significant amounts of fatty acids or ketone bodies due to mitochondrial dysfunction. Second, high insulin and insulin-like growth factor (IGF)-1 levels resulting from chronic ingestion of CHO-rich Western diet meals, can directly promote tumor cell proliferation via the insulin/IGF1 signaling pathway. Third, ketone bodies that are elevated when insulin and blood glucose levels are low, have been found to negatively affect proliferation of different malignant cells in vitro or not to be usable by tumor cells for metabolic demands, and a multitude of mouse models have shown anti-tumorigenic properties of very low CHO ketogenic diets. In addition, many cancer patients exhibit an altered glucose metabolism characterized by insulin resistance and may profit from an increased protein and fat intake

    Halo streams in the solar neighborhood

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    The phase-space structure of our Galaxy holds the key to understand and reconstruct its formation. The Lambda-CDM model predicts a richly structured phase-space distribution of dark matter and (halo) stars, consisting of streams of particles torn from their progenitors during the process of hierarchical merging. While such streams quickly loose their spatial coherence in the process of phase mixing, the individual stars keep their common origin imprinted into their kinematic and chemical properties, allowing the recovery of the Galaxy's individual "building blocks". The field of Galactic Archeology has witnessed a dramatic boost over the last decade, thanks to the increasing quality and size of available data sets. This is especially true for the solar neighborhood, a volume of 1-2 kpc around the sun, where large scale surveys like SDSS/SEGUE continue to reveal the full 6D phase-space information of thousands of halo stars. In this review, I summarize the discoveries of stellar halo streams made so far and give a theoretical overview over the search strategies imployed. This paper is intended as an introduction to researchers new to field, but also as a reference illustrating the achievements made so far. I conclude that disentangling the individual fragments from which the Milky Way was built requires more precise data that will ultimately be delivered by the Gaia mission.Comment: 26 pages, 6 figures, 1 table; accepted for publication in The Astronomy and Astrophysics Revie

    The visitor from an ancient galaxy: A planetary companion around an old, metal-poor red horizontal branch star

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    We report the detection of a planetary companion around HIP 13044, a metal-poor red horizontal branch star belonging to a stellar halo stream that results from the disruption of an ancient Milky Way satellite galaxy. The detection is based on radial velocity observations with FEROS at the 2.2-m MPG/ESO telescope. The periodic radial velocity variation of P=16.2 days can be distinguished from the periods of the stellar activity indicators. We computed a minimum planetary mass of 1.25 Jupiter masses and an orbital semimajor axis of 0.116 AU for the planet. This discovery is unique in three aspects: First, it is the first planet detection around a star with a metallicity much lower than few percent of the solar value; second, the planet host star resides in a stellar evolutionary stage that is still unexplored in the exoplanet surveys; third, the planetary system HIP 13044 most likely has an extragalactic origin in a disrupted former satellite of the Milky Way.Comment: 5 pages, 2 figures, 2 tables, submitted to the Proceedings of the 276th IAU Symposium "The Astrophysics of Planetary Systems

    Effects of publication bias on conservation planning

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    Conservation planning needs reliable information on spatial patterns of biodiversity. However, existing data sets are skewed: some habitats, taxa, and locations are under-represented. Here, we map geographic publication density at the sub-national scale of individual 'provinces'. We query the Web of Science catalogues SCI and SSCI for biodiversity-related publications including country and province names (for the period 1993-2016). We combine these data with other provincial-scale factors hypothesised to affect research (i.e. economic development, human presence, infrastructure and remoteness). We show that sites that appear to be understudied, compared with the biodiversity expected from their bioclimatic conditions, are likely to have been inaccessible to researchers for a diversity of reasons amongst which current or recent armed conflicts are notable. Finally, we create a priority list of provinces where geographic publication bias is of most concern, and discuss how our provincial-scale model can assist in adjusting for publication biases in conservation planning.Comment: 10 pages; 3 figures; 1 table;R code on https://github.com/raffael-hickisch; data at https://zenodo.org/record/998889; interactive at http://bit.ly/publication_density_ma

    Sexual Differentiation of Circadian Clock Function in the Adrenal Gland

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    Sex differences in glucocorticoid production are associated with increased responsiveness of the adrenal gland in females. However, the adrenal-intrinsic mechanisms that establish sexual dimorphic function remain ill defined. Glucocorticoid production is gated at the molecular level by the circadian clock, which may contribute to sexual dimorphic adrenal function. Here we examine sex differences in the adrenal gland using an optical reporter of circadian clock function. Adrenal glands were cultured from male and female Period2::Luciferase (PER2::LUC) mice to assess clock function in vitro in real time. We confirm that there is a pronounced sex difference in the intrinsic capacity to sustain PER2::LUC rhythms in vitro, with higher amplitude rhythms in adrenal glands collected from males than from females. Changes in adrenal PER2::LUC rhythms over the reproductive life span implicate T as an important factor in driving sex differences in adrenal clock function. By directly manipulating hormone levels in adult mice in vivo, we demonstrate that T increases the amplitude of PER2::LUC rhythms in adrenal glands of both male and female mice. In contrast, we find little evidence that ovarian hormones modify adrenal clock function. Lastly, we find that T in vitro can increase the amplitude of PER2::LUC rhythms in male adrenals but not female adrenals, which suggests the existence of sex differences in the mechanisms of T action in vivo. Collectively these results reveal that activational effects of T alter circadian timekeeping in the adrenal gland, which may have implications for sex differences in stress reactivity and stress-related disorders
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