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- Lange, Stephan, et al.
(författare)
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miR-486 is modulated by stretch and increases ventricular growth
- 2019
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Ingår i: Jci Insight. - : American Society for Clinical Investigation. - 2379-3708. ; 4:19
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Tidskriftsartikel (refereegranskat)abstract
- Perturbations in biomechanical stimuli during cardiac development contribute to congenital cardiac defects such as hypoplastic left heart syndrome (HLHS). This study sought to identify stretch-responsive pathways involved in cardiac development. miRNA-Seq identified miR-486 as being increased in cardiomyocytes exposed to cyclic stretch in vitro. The right ventricles (RVs) of patients with HLHS experienced increased stretch and had a trend toward higher miR-486 levels. Sheep RVs dilated from excessive pulmonary blood flow had 60% more miR-486 compared with control RVs. The left ventricles of newborn mice treated with miR-486 mimic were 16.9%-24.6% larger and displayed a 2.48-fold increase in cardiomyocyte proliferation. miR-486 treatment decreased Fox01 and Smad signaling while increasing the protein levels of Stat1. Stat1 associated with Gata-4 and serum response factor (Srf), 2 key cardiac transcription factors with protein levels that increase in response to miR-486. This is the first report to our knowledge of a stretch-responsive miRNA that increases the growth of the ventricle in vivo.
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- Ribeiro Guevara, S., et al.
(författare)
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Sediment records of highly variable mercury inputs to mountain lakes in Patagonia during the past millennium
- 2010
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Ingår i: Atmospheric Chemistry And Physics. - 1680-7316 .- 1680-7324. ; 10:7, s. 3443-3453
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Tidskriftsartikel (refereegranskat)abstract
- High Hg levels in the pristine lacustrine ecosystems of the Nahuel Huapi National Park, a protected zone situated in the Andes of Northern Patagonia, Argentina, have initiated further investigations on Hg cycling and source identification. Here we report Hg records in sedimentary sequences to identify atmospheric sources during the past millennium. In addition to global transport and deposition, a potential atmospheric Hg source to be considered is the local emissions associated with volcanic activity, because the Park is situated in the Southern Volcanic Zone. Two sediment cores were extracted from Lake Toncek, a small, high-altitude system reflecting mainly direct inputs associated with atmospheric contributions, and Lake Moreno Oeste, a much larger and deeper lake having an extended watershed covered mostly by native forest. The sedimentary sequences were dated based on both Pb-210 and Cs-137 profiles. In addition, tephra layers were identified and geochemically characterized for chronological application and to investigate any association of volcanic eruptions with Hg records. Hg concentrations in sediments were measured along with 32 other elements, as well as organic matter, subfossil chironomids, and biogenic silica. Observed background Hg concentrations, determined from the sequence domains with lower values, ranged from 50 to 100 ng g(-1) dry weight (DW), whereas the surficial layers reached 200 to 500 ng g(-1) DW. In addition to this traditional pattern, however, two deep domains in both sequences showed dramatically increased Hg levels reaching 400 to 650 ng g(-1) DW; the upper dated to the 18th to 19th centuries, and the lower around the 13th century. These concentrations are not only elevated in the present profiles but also many-fold above the background values determined in other fresh water sediments, as were also the Hg fluxes, reaching 120 to 150 mu g m(-2) y(-1) in Lake Toncek. No correlation was observed between Hg concentrations and the contents of organic matter, subfossil chironomids, biogenic silica, or the other elements determined. However, distinctly increased Hg concentrations were observed immediately above some tephra layers, suggesting a link to volcanic events. Extended fires might be another potential atmospheric source because the earlier Hg peaks coincide with reported charcoal peaks, whereas the upper Hg peaks coincide with evidences of extended forest fires from tree-ring data and historical records.
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- Sjoblom, A., et al.
(författare)
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The influence of humic substances on the speciation and bioavailability of dissolved mercury and methylmercury, measured as uptake by Chaoborus larvae and loss by volatilization
- 2000
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Ingår i: Science of the Total Environment. - 0048-9697 .- 1879-1026. ; 261:1-3, s. 115-124
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Tidskriftsartikel (refereegranskat)abstract
- The influence of dissolved humic substances (HS) on the bioavailability of dissolved inorganic and methyl mercury (Hg) was quantified by measuring the direct uptake of 203Hg in Chaoborus larvae using laboratory microcosms containing artificial freshwater. The animals were exposed individually in triplicate aquaria at 10 different concentrations of HS covering the whole range found in natural freshwaters (0-110 mg C l-1). Mercury-203 concentrations were monitored repeatedly in the same individuals and in their ambient water during up to 10 days. Near-steady state Hg concentrations in Chaoborus were usually reached within 5 days. The bioconcentration factor (BCF, direct uptake only) for the larvae in the absence of HS was 0.55 ± 0.09 (S.E.) ml individual-1 for inorganic Hg and 5.3 ± 0.7 ml individual-1 for methyl Hg, thus showing a 10-fold difference. Normalizing to the organic carbon content of the larvae yields a BCF(OC) in the absence of HS of 2.8 ± 0.4 x 103 ml (gC)-1 for inorganic Hg and 2.7 ± 0.3 x 104 ml (gC)-1 for methyl Hg. The uptake of both inorganic and methyl Hg decreased markedly with increasing concentration of HS. For inorganic Hg, the decrease in uptake was most pronounced at HS concentrations below 0.2 mg C l-1. For methyl Hg, the relationship between uptake and log([HS]) was sigmoid, showing a reduction by >90% when increasing HS concentrations from 1 to 50 mg C l-1. Similar patterns were observed for losses of Hg from the water phase, mainly through volatilization. These results have implications for both the biouptake and the abiotic cycling of Hg in natural ecosystems and suggest that most dissolved inorganic Hg is bound to dissolved organic matter in most natural freshwaters, whereas dissolved methyl Hg is bound only in humic waters. Assuming that only free aqueous Hg is taken up by the organisms, the rather simple methodology employed here can be used for estimating distribution coefficients (K(OC)) for Hg between HS and water. In this study, the K(OC) values were 2.5 ± 0.7 (S.E.) x 107 ml (gC)-1 for inorganic Hg and 1.5 ± 0.6 x 105 ml (gC)-1 for methyl Hg. Values of similar magnitude were derived from observed losses of Hg from the water phase, supporting the assumption of an immobilization of both inorganic and methyl Hg by HS. The strong negative influence of dissolved HS on the bioavailability of both inorganic and methyl Hg in freshwater suggests that the high Hg levels often found in fish from humic lakes in the boreal forest zone cannot be explained alone by direct uptake of methyl Hg from the water phase into biota at low trophic levels. (C) 2000 Elsevier Science B.V.
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