969 resultados para 1,25(OH)(2)D-3
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Welsch (Projektbearbeiter): Offener Brief an den Eltviller geistlichen Rat Philipp Schütz, in dem dieser unter Hinweis auf zahlreiche finanzielle Unregelmäßigkeiten zum Rücktritt aufgefordert wird. In Replik auf eine Verteidigungsrede Schützens vom Vorabend. Sein Ziel erreichte das Sicherheits-Comité übrigens nicht
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unverantwortlich verfasst von Fr. Stoltze
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Signatur des Originals: S 36/G04510
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AR
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AR
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It is generally believed that 1,25(OH)2D3, bound to its receptor (VDR) contributes to calcium homeostasis by regulating active calcium absorption in the proximal small intestine. However, studying patients with hereditary vitamin D-resistant rickets (HVDRR) provided investigators with a better understanding of VDR's role in calcium homeostasis. HVDRR patients have inactivating mutations in the VDR, and as a consequence they develop hypocalcemia, hyperparathyroidism and severe rickets. However, these phenotypes can be corrected if the patients are given IV infusions of calcium or dietary calcium. This raises the question of what is the physiological significance of VDR-regulated active calcium absorption if calcium homeostasis can be restored independently of the VDR. ^ In order to distinguish the contribution of VDR in the proximal small intestine to overall calcium homeostasis, I generated transgenic mice expressing the human VDR (hVDR) exclusively in the proximal small intestine of mVDR-/- mice by using an hVDR-expressing transgene driven by the duodenal-specific adenosine deaminase enhancer (hVDR+/mVDR-/-). hVDR+/mVDR-/- mice expressed transcriptionally active hVDR only in the proximal small intestine and responded to 1,25(OH)2D3 by up-regulating expression of TRPV6 and calbindin D9K, genes involved in calcium absorption. Furthermore, ligated duodenal loop assays determined that calcium absorption in hVDR+/mVDR-/- mice was as responsive to 1,25(OH)2D3 as in WT mice. Despite having a functional hVDR in the proximal small intestine, hVDR+/mVDR-/- mice were hypocalcemic, had hyperparathyroidism, and were rachitic when fed a normal rodent diet at weaning, as were the mVDR-/- mice. However, when fed a high calcium, phosphorus, and lactose diet (rescue diet), the hVDR+/mVDR-/- mice responded more effectively than the mVDR-/- mice by down-regulation of parathyroid hormone production and by a greater increase in bone mineralization. Furthermore, when three-month-old rachitic mice were fed a rescue diet for 3 weeks, serum calcium and bone mineral content were normalized in hVDR+/mVDR-/- mice, but not in mVDR-/- mice. ^ In conclusion, hVDR expression enabled young mice to better use the rescue diet than mVDR-/- mice. Expression of transgenic hVDR also protected the ability of older mice to respond to the rescue diet despite the absence of the VDR elsewhere in the intestinal tract. I propose that because hVDR+/mVDR-/- mice responded better than mVDR-/- mice to the rescue diet, it is likely that VDR expression in the proximal small intestine is necessary in nutritional (insufficient dietary calcium) and physiological (age) conditions when passive calcium absorption is inadequate. ^
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Glacier inventories provide the basis for further studies on mass balance and volume change, relevant for local hydrological issues as well as for global calculation of sea level rise. In this study, a new Austrian glacier inventory has been compiled, updating data from 1969 (GI 1) and 1998 (GI 2) based on high-resolution lidar digital elevation models (DEMs) and orthophotos dating from 2004 to 2012 (GI 3). To expand the time series of digital glacier inventories in the past, the glacier outlines of the Little Ice Age maximum state (LIA) have been digitalized based on the lidar DEM and orthophotos. The resulting glacier area for GI 3 of 415.11 ± 11.18 km**2 is 44% of the LIA area. The annual relative area losses are 0.3%/yr for the ~119-year period GI LIA to GI 1 with one period with major glacier advances in the 1920s. From GI 1 to GI 2 (29 years, one advance period of variable length in the 1980s) glacier area decreased by 0.6% yr?1 and from GI 2 to GI 3 (10 years, no advance period) by 1.2%/yr. Regional variability of the annual relative area loss is highest in the latest period, ranging from 0.3 to 6.19%/yr. The mean glacier size decreased from 0.69 km**2 (GI 1) to 0.46 km**2 (GI 3), with 47% of the glaciers being smaller than 0.1 km**2 in GI 3 (22%).
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Composition of ore minerals in MAR sulflde occurrences related to ultramaflc rocks was studied using methods of mineragraphy, electron microscopy, microprobe analysis, and X-ray analysis. Objects are located at various levels of maturity of sulflde mounds owing to differences in age, duration and degree of activity of the following hydrothermal systems: generally inactive Logatchev-1 field (up to 66.5 ka old), inactive Logatchev-2 field (3.9 ka), and generally active Rainbow field (up to 23 ka). Relative to MAR submarine ore occurrences in the basalt substrate, mineralization in the hydrothermal fields mentioned above is characterized by high contents of Au, Cd, Co, and Ni, along with presence of accessory minerals of Co and Ni. The studied mounds differ in quantitative ratios of major minerals and structural-textural features of ores that suggest their transformation. Ores in the Logatchev-1 field are characterized by the highest Cu content and development of a wide range of multistage contrast exsolution structures of isocubanite and bornite. In the Logatchev-2 field, sphalerite-chalcopyrite and gold-arsenic exsolution structures are present, but isocubanite exsolution structures are less diverse and contrast. The Rainbow field is marked by presence of homogenous isocubanite and the subordinate development of exsolution structures. The authors have identified four new phases in the Cu-Fe-S system. Phases X and Y (close to chalcopyrite and isocubanite, respectively) make up lamellae among isocubanite exsolution products in the Logatchev-1 and Logatchev-2 fields. Phase Y includes homogenous zones in zonal chimneys of the Rainbow field. Phases A and B formed in the orange bornite domain at low-temperature alteration of chalcopyrite in the Logatchev-1 field. Mineral assemblages of the Cu-S system are most abundant and diverse in the Logatchev-1 field, but their development is minimal in the Logatchev-2 field where mainly Cu-poor sulfides of the geerite-covellite series have been identified. Specific features of mineral assemblages mentioned above reflect the maturity grade of sulfide mounds and can serve as indicators of maturity.
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Large organic food falls to the deep sea - such as whale carcasses and wood logs - support the development of reduced, sulfidic niches in an otherwise oxygenated, oligotrophic deep-sea environment. These transient hot spot ecosystems may serve the dispersal of highly adapted chemosynthetic organisms such as thiotrophic bivalves and siboglinid worms. Here we investigated the biogeochemical and microbiological processes leading to the development of sulfidic niches. Wood colonization experiments were carried out for the duration of one year in the vicinity of a cold seep area in the Nile deep-sea fan (Eastern Mediterranean) at depths of 1690 m. Wood logs were deployed in 2006 during the BIONIL cruise (RV Meteor M70/2 with ROV Quest, Marum, Germany) and sampled in 2007 during the Medeco-2 cruise (RV Pourquoi Pas? with ROV Victor 6000, Ifremer, France). Wood-boring bivalves played a key role in the initial degradation of the wood, the dispersal of wood chips and fecal matter around the wood log, and the provision of colonization surfaces to other organisms. Total oxygen uptake measured with a ROV-operated benthic chamber module was higher at the wood (0.5 m away) in contrast to 10 m away at a reference site (25 mmol m-2 d-1 and 1 mmol m-2 d-1, respectively), indicating an increased activity of sedimentary communities around the wood falls. Bacterial cell numbers associated with wood increased substantially from freshly submerged wood to the wood chip/fecal matter layer next to the wood experiments, as determined with Acridine Orange Direct Counts (AODC) and DAPI-stained counts. Microsensor measurements of sulfide, oxygen and pH were conducted ex situ. Sulfide fluxes were higher at the wood experiments when compared to reference measurements (19 and 32 mmol m-2 d-1 vs. 0 and 16 mmol -2 d-1, respectively). Sulfate reduction (SR) rates at the wood experiments were determined in ex situ incubations (1.3 and 2.0 mmol m-2 d-1) and fell into the lower range of SR rates previously observed from other chemosynthetic habitats at cold seeps. There was no influence of wood deposition on phosphate, silicate and nitrate concentrations, but ammonium concentrations were elevated at the wood chip-sediment boundary layer. Concentrations of dissolved organic carbon were much higher at the wood experiments (wood chip-sediment boundary layer) in comparison to measurements at the reference sites, which may indicate that cellulose degradation was highest under anoxic conditions and hence enabled by anaerobic benthic bacteria, e.g. fermenters and sulfate reducers. Our observations demonstrate that, after one year, the presence of wood at the seafloor had led to the creation of sulfidic niches, comparable to what has been observed at whale falls, albeit at lower rates.
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We investigated optimal conditions for characterization of bioactivity of lytic compound(s) excreted by Alexandrium tamarense based on a cell-bioassay system. Allelochemical response of the cryptophyte Rhodomonas salina indicated the presence oflytic compound(s) in a reliable and reproducible way and allows for quantification of this lytic effect. The parameters tested were the incubation time of putatively lytic extracts or fractions with the target organism R. salina, different techniques for cell harvest from A. tamarense cultures and the optimal harvest time. A three hour incubation time was found to be optimal to yield a rapid response while accurately estimating effective concentration (ECso) values. Harvest of A. tamarense cultures by filtration resulted in loss of lytic activity in most cases and centrifugation was most efficient in terms of recovery of lytic activity. Maximum yield of extracellular lytic activity of A. tamarense cultures was achieved in the stationary phase. Such optimized bioassay guided fractionation techniques are a valuable asset in the isolation and eventual stmctural elucidation of the unknown lytic substances.
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The high levels of polychlorinated biphenyls (PCBs) and DDT in gray seal (Halichoerus grypus) and ringed seal (Phoca hispida botnica) in the Baltic Sea have been associated with pathological disruptions, including bone lesions and reproductive failures. The underlying environmental and toxicological mechanisms leading to these pathological changes are not yet fully understood. The present study investigated the relationship between the individual contaminant load and bone- and thyroid-related effects in adult gray seals (n = 30) and ringed seals (n = 46) in the highly contaminated Baltic Sea and in reference areas (Sable Island, Canada, and Svalbard, Norway). In the gray seals, multivariate and correlation analyses revealed a clear relationship between circulating 1,25-dihydroxyvitamin D3 (1,25(OH)2D), calcium, phosphate, and thyroid hormone (TH) levels and hepatic PCB and DDT load, which suggests contaminant-mediated disruption of the bone and thyroid homeostasis. Contaminants may depress 1,25(OH)2D levels or lead to hyperthyroidism, which may cause bone resorption. In the ringed seals, associations between circulating 1,25(OH)2D, THs, and hepatic contaminants were less prominent. These results suggest that bone lesions observed in the Baltic gray seals may be associated with contaminant-mediated vitamin D and thyroid disruption.