Although marrow adipocytes and osteoblasts derive from a common bone marrow stromal cells (BMSCs), the mechanisms that underlie osteoporosis-associated bone loss and marrow adipogenesis during prolonged steroid treatment are unclear. We show in human BMSCs (hBMSCs) that glucocorticoid receptor (GR) signaling in response to high concentrations of glucocorticoid (GC) supports adipogenesis but inhibits osteogenesis by reducing c-Jun expression and hBMSC proliferation. Conversely, significantly lower concentrations of GC, which permit hBMSC proliferation, are necessary for normal bone mineralization. In contrast, platelet-derived growth factor (PDGF) signaling increases both JNK/c-Jun activity and hBMSC expansion, favoring osteogenic differentiation instead of adipogenesis. Indeed, PDGF antagonizes the proadipogenic qualities of GC/GR signaling. Thus our results reveal a novel c-Jun-centered regulatory network of signaling pathways in differentiating hBMSCs that controls the proliferation-dependent balance between osteogenesis and adipogenesis.
Paternal behavior and testosterone plasma levels in the Volcano Mouse Neotomodon alstoni (Rodentia: Muridae). Although initially it was thought that testosterone inhibited the display of paternal behavior in males of rodents, it has been shown that in some species high testosterone levels are needed for exhibition of paternal care. In captivity, males of volcano Mouse (Neotomodon alstoni) provide pups the same care provided by the mother, with the exception of suckling. Here we measured plasmatic testosterone concentrations 10 days after mating, five and 20 days postpartum, and 10 days after males were isolated from their families in order to determine possible changes in this hormone, associated to the presence and age of pups. Males of volcano Mouse exhibited paternal behavior when their testosterone levels were relatively high. Although levels of this hormone did not change with the presence or pups age, males that invested more time in huddling showed higher testosterone levels. It is possible that in the volcano Mouse testosterone modulates paternal behavior indirectly, as in the California mouse.
Se presenta un listado de 90 especies de musgos asociados a parches de bosques de Polylepis sericea Wedd., en el estado Mérida, Venezuela. La familia Leucobryaceae es la más diversa con 14 especies. Bryaceae, Bartramiaceae y Pottiaceae, le siguen en orden de importancia taxonómica. Los géneros más diversos son Campylopus (14 especies), Leptodontium (5), Breutelia (4), Bryum (4), Zygodon (4) y Racomitrium (3). La condición acrocárpica es la dominante, representada por 68 especies, siendo los tepes altos los más frecuentes (41,11%), seguidos por los tepes cortos (24,44%) y los tapetes extensivos (8,89%). El análisis fitogeográfico muestra una predominancia del elemento neotropical (36%) sobre el elemento ampliamente distribuido en el mundo (27%). En la Sierra Nevada de Mérida, son exclusivas 39 especies y 34 en la Sierra de La Culata. Solo el 19% de las especies es compartido por ambas sierras, indicando que existe un recambio de las especies en los parches de bosque inventarios lo que podría estar asociado con variables físicas y ambientales de cada localidad. Se adicionan las especies Drepanocladus sordidus (Amblystegiaceae), Myurella sibirica (Plagiotheciaceae) y Pleurochaete luteola (Pottiaceae) a la brioflora venezolana, así como nueve nuevos registros para la brioflora del estado Mérida.
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