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131.
Sun Wook Cho Flavia Q. Pirih Amy J. Koh Megan Michalski Matthew R. Eber Kathryn Ritchie Benjamin Sinder Seojin Oh Saja A. Al-Dujaili JoonHo Lee Ken Kozloff Theodora Danciu Thomas J. Wronski Laurie K. McCauley 《The Journal of biological chemistry》2013,288(10):6814-6825
Both PTH and IL-6 signaling play pivotal roles in hematopoiesis and skeletal biology, but their interdependence is unclear. The purpose of this study was to evaluate the effect of IL-6 and soluble IL-6 receptor (sIL-6R) on hematopoietic and skeletal actions of PTH. In the bone microenvironment, PTH stimulated sIL-6R protein levels in primary osteoblast cultures in vitro and bone marrow in vivo in both IL-6+/+ and IL-6−/− mice. PTH-mediated hematopoietic cell expansion was attenuated in IL-6−/− compared with IL-6+/+ bone marrow, whereas sIL-6R treatment amplified PTH actions in IL-6−/− earlier than IL-6+/+ marrow cultures. Blocking sIL-6R signaling with sgp130 (soluble glycoprotein 130 receptor) inhibited PTH-dependent hematopoietic cell expansion in IL-6−/− marrow. In the skeletal system, although intermittent PTH administration to IL-6+/+ and IL-6−/− mice resulted in similar anabolic actions, blocking sIL-6R significantly attenuated PTH anabolic actions. sIL-6R showed no direct effects on osteoblast proliferation or differentiation in vitro; however, it up-regulated myeloid cell expansion and production of the mesenchymal stem cell recruiting agent, TGF-β1 in the bone marrow microenvironment. Collectively, sIL-6R demonstrated orphan function and mediated PTH anabolic actions in bone in association with support of myeloid lineage cells in the hematopoietic system. 相似文献
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Romeo A. Saldaña‐Vázquez Alejandro A. Castro‐Luna Cesar A. Sandoval‐Ruiz Jesús R. Hernández‐Montero Kathryn E. Stoner 《Biotropica》2013,45(3):351-356
Studies comparing the abundance of frugivorous bats in shade‐coffee plantations and forest fragments report contradictory results, and have not taken into account the landscape context in which coffee plantations are immersed. Variables of population composition such as abundance, sex proportion, and reproductive condition, together with biological tags (i.e., bat fly prevalence), can provide information about spatiotemporal dynamics of habitats used by bats. In the central part of Veracruz, Mexico, we compared population variables and ectoparasite prevalence of the highland yellow‐shouldered bat (Sturnira ludovici) in two landscapes, one dominated by shade‐coffee plantations and another by forest fragments. Comparing these attributes between these two landscapes will increase our knowledge about the role of this agro‐ecosystem in the conservation of this species, which is an important seed disperser of cloud forest vegetation. Total abundance and proportion of females was greater in forest fragments than in coffee plantations, whereas the percentage of reproductive females and bat fly prevalence was similar between landscapes. Our results show that landscapes with forest fragments harbor the greatest abundance of S. ludovici, but shade‐coffee plantations also are utilized by S. ludovici and likely adjacent forest remnants provide enough food resources for this species and other frugivores. Moreover, this study provides more evidence documenting the importance of preserving the last cloud forest fragments in the central region of Veracruz, Mexico, and suggests that using shade‐coffee plantations to connect forest fragments may be an effective way of maintaining populations of S. ludovici and likely other volant frugivores. 相似文献
134.
Christine Herbst Nicole Wäschke E. Kathryn Barto Sabrina Arnold Daniel Geuß Ivonne Halboth Sabina Reschke Jakob Sänger Torsten Meiners Elisabeth Obermaier 《Entomologia Experimentalis et Applicata》2013,147(3):269-281
Increasing land use intensity and human influence are leading to a reduction in plant and animal species diversity. However, little is known about how these changes may affect higher trophic levels, apart from simply reducing species numbers. Here we investigated, over 3 years, the influence of different land practices on a tritrophic system in grassland habitats. The system consisted of the host plant Plantago lanceolata L. (Plantaginaceae), two monophagous weevils, Mecinus labilis Herbst and Mecinus pascuorum Gyllenhal (Coleoptera: Curculionidae), and their parasitoid Mesopolobus incultus Walker (Hymenoptera: Pteromalidae). At over 70 sites across three geographic regions in Germany, we measured plant species diversity and vegetation structure, as well as abundance of P. lanceolata, the two weevils, and the parasitoid. Land use intensity (fertilization) and type (mowing vs. grazing) negatively affected not only plant species richness but also the occurrence of the two specialized herbivores and their parasitoid. In contrast, land use had a mostly positive effect on host plant size, vegetation structure, and parasitization rate. This study reveals that intensification of land use influences higher trophic organisms even without affecting the availability of the host plant. The observed relationships between land use, vegetation complexity, and the tritrophic system are not restricted locally; rather they are measureable along a broad range of environmental conditions and years throughout Germany. Our findings may have important implications for the conservation of insect species of nutrient‐poor grasslands. 相似文献
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Hormones are critical for the development, maturation, and maintenance of physiological systems; therefore, understanding their involvement during maturation of the brain is important for the elucidation of mechanisms by which adults become behaviorally competent. Changes in exogenous and endogenous factors encountered during sexual maturation can have long lasting effects in mature adults. In this study, we investigated the role of the gonadotropic hormone, juvenile hormone (JH), in the modulation of adult behaviors in Drosophila. Here we utilized methoprene (a synthetic JH analog) and precocene (a JH synthesis inhibitor) to manipulate levels of JH in sexually immature male and female Drosophila with or without decreased synthesis of neuronal dopamine (DA). Locomotion and courtship behavior were assayed once the animals had grown to sexual maturity. The results demonstrate a sexually dimorphic role for JH in the modulation of these centrally controlled behaviors in mature animals that is dependent on the age of the animals assayed, and present DA as a candidate neuronal factor that differentially interacts with JH depending on the sex of the animal. The data also suggest that JH modulates these behaviors through an indirect mechanism. Since gonadotropic hormones and DA interact in mammals to affect brain development and later function, our results suggest that this mechanism for the development of adult behavioral competence may be evolutionarily conserved. 相似文献
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138.
Kerri N. Smith Sarah J. Halfyard Edward S. Yaskowiak Kathryn L. Shultz Wesley G. Beamer Ann M. Dorward 《Mammalian genome》2013,24(1-2):63-71
The spontaneous development of juvenile-onset, ovarian granulosa cell (GC) tumors in the SWR/Bm (SWR) inbred mouse strain is a model for juvenile-type GC tumors that appear in infants and young girls. GC tumor susceptibility is supported by multiple Granulosa cell tumor (Gct) loci, but the Gct1 locus on Chr 4 derived from SWR strain background is fundamental for GC tumor development and uniquely responsive to the androgenic precursor dehydroepiandrosterone (DHEA). To resolve the location of Gct1 independently from other susceptibility loci, Gct1 was isolated in a congenic strain that replaces the distal segment of Chr 4 in SWR mice with a 47 × 106-bp genomic segment from the Castaneus/Ei (CAST) strain. SWR females homozygous for the CAST donor segment were confirmed to be resistant to DHEA- and testosterone-induced GC tumorigenesis, indicating successful exchange of CAST alleles (Gct1 CA ) for SWR alleles (Gct1 SW ) at this tumor susceptibility locus. A series of nested, overlapping, congenic sublines was created to fine-map Gct1 based on GC tumor susceptibility under the influence of pubertal DHEA treatment. Twelve informative lines have resolved the Gct1 locus to a 1.31 × 106-bp interval on mouse Chr 4, a region orthologous to human Chr 1p36.22. 相似文献
139.
The spatial component of input signals often carries information crucial to a neuron’s function, but models mapping synaptic inputs to the transmembrane potential can be computationally expensive. Existing reduced models of the neuron either merge compartments, thereby sacrificing the spatial specificity of inputs, or apply model reduction techniques that sacrifice the underlying electrophysiology of the model. We use Krylov subspace projection methods to construct reduced models of passive and quasi-active neurons that preserve both the spatial specificity of inputs and the electrophysiological interpretation as an RC and RLC circuit, respectively. Each reduced model accurately computes the potential at the spike initiation zone (SIZ) given a much smaller dimension and simulation time, as we show numerically and theoretically. The structure is preserved through the similarity in the circuit representations, for which we provide circuit diagrams and mathematical expressions for the circuit elements. Furthermore, the transformation from the full to the reduced system is straightforward and depends on intrinsic properties of the dendrite. As each reduced model is accurate and has a clear electrophysiological interpretation, the reduced models can be used not only to simulate morphologically accurate neurons but also to examine computations performed in dendrites. 相似文献
140.