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1.
Hum Mol Genet ; 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31691804

RESUMO

DHX15, a DEAH box containing RNA helicase, is a splicing factor required for the last step of splicing. Recent studies identified a recurrent mutational hotspot, R222G, in DHX15 in ~ 6% of acute myeloid leukemia (AML) patients that carry the fusion protein RUNX1-RUNX1T1 produced by t (8;21) (q22;q22). Studies using yeast mutants showed that substitution of G for the residue equivalent to R222 leads to loss of its helicase function, suggesting it is a loss of function mutation. To elucidate the role of DHX15 during development, we established the first vertebrate knockout model with CRISPR/Cas9 in zebrafish. Our data showed that dhx15 expression is enriched in the brain, eyes, pectoral fin primordia, liver and intestinal bulb during embryonic development. Dhx15 deficiency leads to pleiotropic morphological phenotypes in homozygous mutant embryos starting at 3 days post fertilization (dpf) that result in lethality by 7 dpf, revealing an essential role during embryonic development. RNA-seq analysis suggested important roles of Dhx15 in chromatin and nucleosome assembly and regulation of the Mdm2-p53 pathway. Interestingly, exons corresponding to the alternate transcriptional start sites for tp53 and mdm2 were preferentially expressed in the mutant embryos, leading to significant upregulation of their alternate isoforms, Δ113p53 (orthologous to Δ133p53 isoform in human) and mdm2-P2 (isoform using distal promoter P2), respectively. We speculate that these alterations in the Mdm2-p53 pathway contribute to the development of AML in patients with t (8,21) and somatically mutated DHX15.

2.
Environ Pollut ; : 113543, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31753634

RESUMO

Aquaculture can affect the polyunsaturated fatty acids (PUFA) and mercury (Hg) in fish by altering their diet. Here, planktivorous (silver carp and bighead carp), omnivorous and carnivorous fish with different dietary strategies were selected from two reservoirs, one with on-going aquaculture (WJD) and another without aquaculture (HF) in Southwest China. We compared the total mercury (THg), methylmercury (MeHg) contents and PUFA profiles of fish and their potential diets in these two reservoirs. THg and MeHg contents in omnivorous and carnivorous fish were lower from the WJD Reservoir, which is related to the lower THg and MeHg contents in the artificial fish food. THg and MeHg contents in silver carp from the WJD Reservoir were lower than those from the HF Reservoir, while they were similar in bighead carps from the two reservoirs. The Hg variation in planktivorous fish were inconsistent with that in plankton. THg contents in phyto- and zooplankton from the HF Reservoir were higher than those from the WJD Reservoir, yet their MeHg contents were similar. Artificial fish food which contained higher total PUFA eicosapentaenoic (EPA; 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), significantly increased the total PUFA and EPA + DHA contents in carnivorous fish, but had less effect on that in omnivorous fish from the WJD Reservoir. Eutrophication caused by aquaculture reduced total PUFA and EPA + DHA contents of plankton in WJD, yet did not reduce those in planktivorous fish. The impacts of aquaculture on Hg and PUFA accumulated in fish were varied among different fish species, and the mechanism needs further exploration.

3.
Dis Model Mech ; 2019 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-31727854

RESUMO

Mutations in the gene AK2 are responsible for Reticular Dysgenesis (RD), a rare and severe form of primary immunodeficiency in children. RD patients have a severely shortened life expectancy and without treatment die, generally from sepsis early after birth. The only available therapeutic option for RD is hematopoietic stem cell transplantation (HSCT). To gain insight into the pathophysiology of RD, we previously created zebrafish models for AK2 deficiencies. One of the clinical features of RD is hearing loss, but its pathophysiology and causes have not been determined. In adult mammals, sensory hair cells of the inner ear do not regenerate; however, their regeneration has been observed in several non-mammalian vertebrates, including zebrafish. Therefore, we used our RD zebrafish models to determine if AK2 deficiency affects sensory organ development and/or hair cell regeneration. Our studies indicated that AK2 is required for the correct development, survival and regeneration of sensory hair cells. Interestingly, AK2 deficiency induces the expression of several oxidative stress markers and it triggers an increased level of cell death in the hair cells. Finally, we show that glutathione treatment can partially rescue hair cell development in the sensory organs in our RD models, pointing to the potential use of antioxidants as a therapeutic treatment supplementing HSCT to prevent or ameliorate sensorineural hearing deficits in RD patients.

4.
Cell Syst ; 9(2): 187-206.e16, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31445892

RESUMO

Tumor cells encounter a myriad of physical cues upon arrest and extravasation in capillary beds. Here, we examined the role of physical factors in non-random organ colonization using a zebrafish xenograft model. We observed a two-step process by which mammalian mammary tumor cells showed non-random organ colonization. Initial homing was driven by vessel architecture, where greater numbers of cells became arrested in the topographically disordered blood vessels of the caudal vascular plexus (CVP) than in the linear vessels in the brain. Following arrest, bone-marrow- and brain-tropic clones exhibited organ-specific patterns of extravasation. Extravasation was mediated by ß1 integrin, where knockdown of ß1 integrin reduced extravasation in the CVP but did not affect extravasation of a brain-tropic clone in the brain. In contrast, silencing myosin 1B redirected early colonization from the brain to the CVP. Our results suggest that organ selectivity is driven by both vessel topography and cell-type-dependent extravasation.

5.
Sci Total Environ ; 669: 821-832, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30897439

RESUMO

Dietary uptake is a key step in conveying both toxic mercury (Hg; particularly as highly bioavailable methylmercury, MeHg) and essential dietary biochemicals, such as polyunsaturated fatty acids (PUFA), across trophic levels within aquatic food webs. Using stable isotopes and fatty acids we evaluated the role of food sources in size-fractioned plankton and littoral macroinvertebrates for the bioaccumulation of total Hg and MeHg in six oligotrophic and one mesotrophic Swedish lakes with differing concentrations of dissolved organic carbon (DOC). We found that the consumption of both algal and terrestrial diets (assessed by PUFA and long-chain saturated fatty acids, respectively) predicted >66% of the Hg concentration variability in meso- (100-500 µm) and macrozooplankton (>500 µm) in oligotrophic lakes. In the mesotrophic lake, total Hg bioaccumulation in higher trophic level biota, carnivorous macroinvertebrates was also significantly related to terrestrial diet sources (R2 = 0.65, p < 0.01). However, lake pH and DOC correlated to total Hg bioaccumulation and bioconcentration across all lakes, suggesting the consumption of different diet sources is mediated by the influence of lake characteristics. This field study reveals that using dietary biomarkers (stable isotopes and fatty acids) together with the physico-chemical lake parameters pH and nutrients together improve our ability to predict Hg bioaccumulation in aquatic food webs. Fatty acids used as dietary biomarkers provide correlative evidence of specific diet source retention in consumers and their effect on Hg bioaccumulation, while pH and nutrients are the underlying physico-chemical lake parameters controlling differences in Hg bioaccumulation between lakes.


Assuntos
Monitoramento Ambiental , Invertebrados/metabolismo , Mercúrio/metabolismo , Poluentes Químicos da Água/metabolismo , Zooplâncton/metabolismo , Animais , Carbono , Exposição Dietética/análise , Exposição Dietética/estatística & dados numéricos , Cadeia Alimentar , Lagos , Compostos de Metilmercúrio/metabolismo
6.
Sci Rep ; 9(1): 1759, 2019 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-30741975

RESUMO

The inflammatory response, modulated both by tissue resident macrophages and recruited monocytes from peripheral blood, plays a critical role in human diseases such as cancer and neurodegenerative disorders. Here, we sought a model to interrogate human immune behavior in vivo. We determined that primary human monocytes and macrophages survive in zebrafish for up to two weeks. Flow cytometry revealed that human monocytes cultured at the physiological temperature of the zebrafish survive and differentiate comparable to cohorts cultured at human physiological temperature. Moreover, key genes that encode for proteins that play a role in tissue remodeling were also expressed. Human cells migrated within multiple tissues at speeds comparable to zebrafish macrophages. Analysis of gene expression of in vivo educated human macrophages confirmed expression of activated macrophage phenotypes. Here, human cells adopted phenotypes relevant to cancer progression, suggesting that we can define the real time immune modulation of human tumor cells during the establishment of a metastatic lesion in zebrafish.

7.
Sci Rep ; 9(1): 518, 2019 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-30679728

RESUMO

The formation of the potent neurotoxic methylmercury (MeHg) is a microbially mediated process that has raised much concern because MeHg poses threats to wildlife and human health. Since boreal forest soils can be a source of MeHg in aquatic networks, it is crucial to understand the biogeochemical processes involved in the formation of this pollutant. High-throughput sequencing of 16S rRNA and the mercury methyltransferase, hgcA, combined with geochemical characterisation of soils, were used to determine the microbial populations contributing to MeHg formation in forest soils across Sweden. The hgcA sequences obtained were distributed among diverse clades, including Proteobacteria, Firmicutes, and Methanomicrobia, with Deltaproteobacteria, particularly Geobacteraceae, dominating the libraries across all soils examined. Our results also suggest that MeHg formation is also linked to the composition of non-mercury methylating bacterial communities, likely providing growth substrate (e.g. acetate) for the hgcA-carrying microorganisms responsible for the actual methylation process. While previous research focused on mercury methylating microbial communities of wetlands, this study provides some first insights into the diversity of mercury methylating microorganisms in boreal forest soils.

8.
Sci Total Environ ; 646: 357-367, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30055496

RESUMO

Methylmercury (MeHg) transfer from water into the base of the food web (bioconcentration) and subsequent biomagnification in the aquatic food web leads to most of the MeHg in fish. But how important is bioconcentration compared to biomagnification in predicting MeHg in fish? To answer this question we reviewed articles in which MeHg concentrations in water, plankton (seston and/or zooplankton), as well as fish (planktivorous and small omnivorous fish) were reported. This yielded 32 journal articles with data from 59 aquatic ecosystems at 22 sites around the world. Although there are many case studies of particular aquatic habitats and specific geographic areas that have examined MeHg bioconcentration and biomagnification, we performed a meta-analysis of such studies. Aqueous MeHg was not a significant predictor of MeHg in fish, but MeHg in seston i.e., the base of the aquatic food web, predicted 63% of the variability in fish MeHg. The MeHg bioconcentration factors (i.e., transfer of MeHg from water to seston; BCFw-s) varied from 3 to 7 orders of magnitude across sites and correlated significantly with MeHg in fish. The MeHg biomagnification factors from zooplankton to fish varied much less (logBMFz-f, 0.75 ±â€¯0.31), and did not significantly correlate with fish MeHg, suggesting that zooplanktivory is not as important as bioconcentration in the biomagnification of fish MeHg across the range of ecosystems represented in our meta-analysis. Partial least square (PLS) and linear regression analyses identified several environmental factors associated with increased BCF, including low dissolved organic carbon, low pH, and oligotrophy. Our study reveals the widespread importance of MeHg bioconcentration into the base of the aquatic food web for MeHg at higher trophic levels in aquatic food webs, as well as the major influences on the variability in this bioconcentration.


Assuntos
Monitoramento Ambiental , Cadeia Alimentar , Compostos de Metilmercúrio/metabolismo , Poluentes Químicos da Água/metabolismo , Animais , Peixes/metabolismo , Mercúrio , Zooplâncton/metabolismo
9.
PLoS Genet ; 14(12): e1007821, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30540754

RESUMO

Fanconi Anemia (FA) is a genomic instability syndrome resulting in aplastic anemia, developmental abnormalities, and predisposition to hematological and other solid organ malignancies. Mutations in genes that encode proteins of the FA pathway fail to orchestrate the repair of DNA damage caused by DNA interstrand crosslinks. Zebrafish harbor homologs for nearly all known FA genes. We used multiplexed CRISPR/Cas9-mediated mutagenesis to generate loss-of-function mutants for 17 FA genes: fanca, fancb, fancc, fancd1/brca2, fancd2, fance, fancf, fancg, fanci, fancj/brip1, fancl, fancm, fancn/palb2, fanco/rad51c, fancp/slx4, fancq/ercc4, fanct/ube2t, and two genes encoding FA-associated proteins: faap100 and faap24. We selected two indel mutations predicted to cause premature truncations for all but two of the genes, and a total of 36 mutant lines were generated for 19 genes. Generating two independent mutant lines for each gene was important to validate their phenotypic consequences. RT-PCR from homozygous mutant fish confirmed the presence of transcripts with indels in all genes. Interestingly, 4 of the indel mutations led to aberrant splicing, which may produce a different protein than predicted from the genomic sequence. Analysis of RNA is thus critical in proper evaluation of the consequences of the mutations introduced in zebrafish genome. We used fluorescent reporter assay, and western blots to confirm loss-of-function for several mutants. Additionally, we developed a DEB treatment assay by evaluating morphological changes in embryos and confirmed that homozygous mutants from all the FA genes that could be tested (11/17), displayed hypersensitivity and thus were indeed null alleles. Our multiplexing strategy helped us to evaluate 11 multiple gene knockout combinations without additional breeding. Homozygous zebrafish for all 19 single and 11 multi-gene knockouts were adult viable, indicating FA genes in zebrafish are generally not essential for early development. None of the mutant fish displayed gross developmental abnormalities except for fancp-/- fish, which were significantly smaller in length than their wildtype clutch mates. Complete female-to-male sex reversal was observed in knockouts for 12/17 FA genes, while partial sex reversal was seen for the other five gene knockouts. All adult females were fertile, and among the adult males, all were fertile except for the fancd1 mutants and one of the fancj mutants. We report here generation and characterization of zebrafish knockout mutants for 17 FA disease-causing genes, providing an integral resource for understanding the pathophysiology associated with the disrupted FA pathway.


Assuntos
Anemia de Fanconi/genética , Peixe-Zebra/genética , Animais , Sistemas CRISPR-Cas , Dano ao DNA , Anemia de Fanconi/fisiopatologia , Feminino , Fertilidade/genética , Fertilidade/fisiologia , Mutação da Fase de Leitura , Técnicas de Inativação de Genes , Humanos , Masculino , Fenótipo , Processamento de RNA/genética , Processos de Determinação Sexual/genética , Processos de Determinação Sexual/fisiologia , Desenvolvimento Sexual/genética , Desenvolvimento Sexual/fisiologia , Peixe-Zebra/crescimento & desenvolvimento , Peixe-Zebra/fisiologia , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/fisiologia
10.
IEEE Trans Biomed Circuits Syst ; 12(5): 1046-1055, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30010595

RESUMO

Direct sensing in liquids using CMOS-integrated optical and electrical sensors is attractive for lab-on-chip applications, where close physical proximity between sample and sensor can obviate optical lenses, enhance electrical sensitivity, and decrease noise due to parasitics. However, controlled delivery of fluid samples to the chip surface presents an ongoing challenge for lab-on-CMOS development, where traditional wire-bond packaging prevents integration of planar microfluidics. In this paper, we present a method for scalable heterogeneous integration of microfluidic channels and silicon-integrated circuit substrates using a commercial fan-out wafer-level packaging approach. The planar surface supports multiple approaches for fluidic integration; we present both a stacked laser-cut fluidic assembly and the fabrication of monolithic SU-8 microchannels over the IC surface. As a proof-of-principle, both electrical and fluidic routing are provided to a custom 0.18-m CMOS optical sensor IC, and optical transmission and fluorescence measurement experiments are demonstrated.

11.
Sci Total Environ ; 622-623: 1353-1362, 2018 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-29890601

RESUMO

A number of studies have evaluated the effects of forest harvest on mercury (Hg) concentrations and exports in surface waters, but few studies have tested the effect from forest harvest on the change in fish Hg concentrations over the course of several years after harvest. To address this question, mercury (Hg) concentrations in perch (Perca fluviatilis) muscle tissue from five lakes were analyzed for two years before (2010-2011) and three years after (2013-2015) forest harvest conducted in 2012. Fish Hg concentrations in the clear-cut catchments (n=1373 fish specimens) were related to temporal changes of fish Hg in reference lakes (n=1099 fish specimen) from 19 lakes in the Swedish National Environmental Monitoring Programme. Small (length<100mm) and large perch (length≥100mm) were analyzed separately, due to changing feeding habitats of fish over growing size. There was considerable year-to-year and lake-to-lake variation in fish Hg concentrations (-14%-121%) after forest harvest in the clearcut lakes, according to our first statistical model that count for fish Hg changes. While the effect ascribed to forest harvest varied between years, after three years (in 2015), a significant increase of 26% (p<0.0001) in Hg concentrations of large fish was identified in our second statistical model that pooled all 5 clearcut lakes. The large fish Hg concentrations in the 19 reference lakes also varied, and in 2015 had decreased by 7% (p=0.03) relative to the concentrations in 2010-2011. The majority of the annual changes in fish Hg concentrations in the clearcut lakes after harvest were in the lower range of earlier predictions for high-latitude lakes extrapolated primarily from the effects of forest harvest operations on Hg concentrations in water. Since the risk of forest harvest impacts on Hg extends to fish and not just surface water concentrations, there is even more reason to consider Hg effects in forestry planning, alongside other ecosystem effects.


Assuntos
Monitoramento Ambiental , Mercúrio/metabolismo , Percas/metabolismo , Poluentes Químicos da Água/metabolismo , Animais , Ecossistema , Lagos/química , Músculos/metabolismo , Suécia , Poluentes Químicos da Água/análise
12.
NPJ Regen Med ; 3: 11, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29872546

RESUMO

Regenerative medicine holds great promise for both degenerative diseases and traumatic tissue injury which represent significant challenges to the health care system. Hearing loss, which affects hundreds of millions of people worldwide, is caused primarily by a permanent loss of the mechanosensory receptors of the inner ear known as hair cells. This failure to regenerate hair cells after loss is limited to mammals, while all other non-mammalian vertebrates tested were able to completely regenerate these mechanosensory receptors after injury. To understand the mechanism of hair cell regeneration and its association with regeneration of other tissues, we performed a guided mutagenesis screen using zebrafish lateral line hair cells as a screening platform to identify genes that are essential for hair cell regeneration, and further investigated how genes essential for hair cell regeneration were involved in the regeneration of other tissues. We created genetic mutations either by retroviral insertion or CRISPR/Cas9 approaches, and developed a high-throughput screening pipeline for analyzing hair cell development and regeneration. We screened 254 gene mutations and identified 7 genes specifically affecting hair cell regeneration. These hair cell regeneration genes fell into distinct and somewhat surprising functional categories. By examining the regeneration of caudal fin and liver, we found these hair cell regeneration genes often also affected other types of tissue regeneration. Therefore, our results demonstrate guided screening is an effective approach to discover regeneration candidates, and hair cell regeneration is associated with other tissue regeneration.

13.
J Chem Phys ; 148(10): 102303, 2018 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-29544287

RESUMO

Free energy calculations are a crucial part of understanding chemical systems but are often computationally expensive for all but the simplest of systems. Various enhanced sampling techniques have been developed to improve the efficiency of these calculations in numerical simulations. However, the majority of these approaches have been applied using classical molecular dynamics. There are many situations where nuclear quantum effects impact the system of interest and a classical description fails to capture these details. In this work, path integral molecular dynamics has been used in conjunction with umbrella sampling, and it has been observed that correct results are only obtained when the umbrella sampling potential is applied to a single path integral bead post quantization. This method has been validated against a Lennard-Jones benchmark system before being applied to the more complicated water dimer system over a broad range of temperatures. Free energy profiles are obtained, and these are utilized in the calculation of the second virial coefficient as well as the change in free energy from the separated water monomers to the dimer. Comparisons to experimental and ground state calculation values from the literature are made for the second virial coefficient at higher temperature and the dissociation energy of the dimer in the ground state.

14.
Ann Rheum Dis ; 77(4): 612-619, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29358286

RESUMO

OBJECTIVES: To characterise the clinical features, immune manifestations and molecular mechanisms in a recently described autoinflammatory disease caused by mutations in TRNT1, a tRNA processing enzyme, and to explore the use of cytokine inhibitors in suppressing the inflammatory phenotype. METHODS: We studied nine patients with biallelic mutations in TRNT1 and the syndrome of congenital sideroblastic anaemia with immunodeficiency, fevers and developmental delay (SIFD). Genetic studies included whole exome sequencing (WES) and candidate gene screening. Patients' primary cells were used for deep RNA and tRNA sequencing, cytokine profiling, immunophenotyping, immunoblotting and electron microscopy (EM). RESULTS: We identified eight mutations in these nine patients, three of which have not been previously associated with SIFD. Three patients died in early childhood. Inflammatory cytokines, mainly interleukin (IL)-6, interferon gamma (IFN-γ) and IFN-induced cytokines were elevated in the serum, whereas tumour necrosis factor (TNF) and IL-1ß were present in tissue biopsies of patients with active inflammatory disease. Deep tRNA sequencing of patients' fibroblasts showed significant deficiency of mature cytosolic tRNAs. EM of bone marrow and skin biopsy samples revealed striking abnormalities across all cell types and a mix of necrotic and normal-appearing cells. By immunoprecipitation, we found evidence for dysregulation in protein clearance pathways. In 4/4 patients, treatment with a TNF inhibitor suppressed inflammation, reduced the need for blood transfusions and improved growth. CONCLUSIONS: Mutations of TRNT1 lead to a severe and often fatal syndrome, linking protein homeostasis and autoinflammation. Molecular diagnosis in early life will be crucial for initiating anti-TNF therapy, which might prevent some of the severe disease consequences.

15.
Sci Total Environ ; 613-614: 1069-1078, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-28950669

RESUMO

Earlier studies have shown that boreal forest logging can increase the concentration and export of methylmercury (MeHg) in stream runoff. Here we test whether forestry operations create soil environments of high MeHg net formation associated with distinct microbial communities. Furthermore, we test the hypothesis that Hg methylation hotspots are more prone to form after stump harvest than stem-only harvest, because of more severe soil compaction and soil disturbance. Concentrations of MeHg, percent MeHg of total Hg (THg), and bacterial community composition were determined at 200 soil sampling positions distributed across eight catchments. Each catchment was either stem-only harvested (n=3), stem- and stump-harvested (n=2) or left undisturbed (n=3). In support of our hypothesis, higher MeHg to THg ratios was observed in one of the stump-harvested catchments. While the effects of natural variation could not be ruled out, we noted that most of the highest % MeHg was observed in water-filled cavities created by stump removal or driving damage. This catchment also featured the highest bacterial diversity and highest relative abundance of bacterial families known to include Hg methylators. We propose that water-logged and disturbed soil environments associated with stump harvest can favor methylating microorganisms, which also enhance MeHg formation.

16.
Sci Total Environ ; 610-611: 623-634, 2018 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-28822930

RESUMO

A better understanding of the dominant source areas and transport pathways of pesticide losses to surface water is needed for targeting mitigation efforts in a more cost-effective way. To this end, we monitored pesticides in surface water in an agricultural catchment typical of one of the main crop production regions in Sweden. Three small sub-catchments (88-242ha) were selected for water sampling based on a high-resolution digital soil map developed from proximal sensing methods and soil sampling; one sub-catchment had a high proportion of clay soils, another was dominated by coarse sandy soils while the third comprised a mix of soil types. Samples were collected from the stream, from field drains discharging into the stream and from within-field surface runoff during spring and early summer in three consecutive years. These samples were analyzed by LC-MS/MS for 99 compounds, including most of the polar and semi-polar pesticides frequently used in Swedish agriculture. Information on pesticide applications (products, doses and timing) was obtained from annual interviews with the farmers. There were clear and consistent differences in pesticide occurrence in the stream between the three sub-catchments, with both the numbers of detected compounds and concentrations being the largest in the area with a high proportion of clay soils and with very few detections in the sandy sub-catchment. Macropore flow to drains was most likely the dominant loss pathway in the studied area. Many of the compounds that were detected in drainage and stream water samples had not been applied for several years. This suggests that despite the predominant role of fast flow pathways in determining losses to the stream, long-term storage along the transport pathways also occurs, presumably in subsoil horizons where degradation is slow.

17.
Sci Rep ; 7(1): 16022, 2017 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-29167528

RESUMO

Peatlands are a major source of methylmercury that contaminates downstream aquatic food webs. The large store of mercury (Hg) in peatlands could be a source of Hg for over a century even if deposition is dramatically reduced. However, the reliability of Hg mass balances can be questioned due to missing long-term land-atmosphere flux measurements. We used a novel micrometeorological system for continuous measurement of Hg peatland-atmosphere exchange to derive the first annual Hg budget for a peatland. The evasion of Hg (9.4 µg m-2 yr-1) over the course of a year was seven times greater than stream Hg export, and over two times greater than wet bulk deposition to the boreal peatland. Measurements of dissolved gaseous Hg in the peat pore water also indicate Hg evasion. The net efflux may result from recent declines in atmospheric Hg concentrations that have turned the peatland from a net sink into a source of atmospheric Hg. This net Hg loss suggests that open boreal peatlands and downstream ecosystems can recover more rapidly from past atmospheric Hg deposition than previously assumed. This has important implications for future levels of methylmercury in boreal freshwater fish and the estimation of historical Hg accumulation rates from peat profiles.

18.
Science ; 358(6365)2017 11 17.
Artigo em Inglês | MEDLINE | ID: mdl-29025994

RESUMO

Despite the wide range of skin pigmentation in humans, little is known about its genetic basis in global populations. Examining ethnically diverse African genomes, we identify variants in or near SLC24A5, MFSD12, DDB1, TMEM138, OCA2, and HERC2 that are significantly associated with skin pigmentation. Genetic evidence indicates that the light pigmentation variant at SLC24A5 was introduced into East Africa by gene flow from non-Africans. At all other loci, variants associated with dark pigmentation in Africans are identical by descent in South Asian and Australo-Melanesian populations. Functional analyses indicate that MFSD12 encodes a lysosomal protein that affects melanogenesis in zebrafish and mice, and that mutations in melanocyte-specific regulatory regions near DDB1/TMEM138 correlate with expression of ultraviolet response genes under selection in Eurasians.


Assuntos
Grupo com Ancestrais do Continente Africano/genética , Evolução Molecular , Fluxo Gênico , Loci Gênicos , Melaninas/genética , Pigmentação da Pele/genética , África Oriental , Animais , Antiporters/genética , Proteínas de Ligação a DNA/genética , Grupos Étnicos/genética , Genoma Humano , Estudo de Associação Genômica Ampla , Humanos , Melaninas/biossíntese , Melaninas/metabolismo , Melanócitos/metabolismo , Proteínas de Membrana/genética , Camundongos , Polimorfismo de Nucleotídeo Único , Exposição à Radiação , Supressão Genética , Raios Ultravioleta
19.
Sci Rep ; 7(1): 9158, 2017 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-28831088

RESUMO

It is well established that stream dissolved inorganic carbon (DIC) fluxes play a central role in the global C cycle, yet the sources of stream DIC remain to a large extent unresolved. Here, we explore large-scale patterns in δ13C-DIC from streams across Sweden to separate and further quantify the sources and sinks of stream DIC. We found that stream DIC is governed by a variety of sources and sinks including biogenic and geogenic sources, CO2 evasion, as well as in-stream processes. Although soil respiration was the main source of DIC across all streams, a geogenic DIC influence was identified in the northernmost region. All streams were affected by various degrees of atmospheric CO2 evasion, but residual variance in δ13C-DIC also indicated a significant influence of in-stream metabolism and anaerobic processes. Due to those multiple sources and sinks, we emphasize that simply quantifying aquatic DIC fluxes will not be sufficient to characterise their role in the global C cycle.

20.
Glob Chang Biol ; 23(12): 5523-5536, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28712133

RESUMO

The stability of northern peatland's carbon (C) store under changing climate is of major concern for the global C cycle. The aquatic export of C from boreal peatlands is recognized as both a critical pathway for the remobilization of peat C stocks as well as a major component of the net ecosystem C balance (NECB). Here, we present a full year characterization of radiocarbon content (14 C) of dissolved organic carbon (DOC), carbon dioxide (CO2 ), and methane (CH4 ) exported from a boreal peatland catchment coupled with 14 C characterization of the catchment's peat profile of the same C species. The age of aquatic C in runoff varied little throughout the year and appeared to be sustained by recently fixed C from the atmosphere (<60 years), despite stream DOC, CO2 , and CH4 primarily being sourced from deep peat horizons (2-4 m) near the mire's outlet. In fact, the 14 C content of DOC, CO2 , and CH4 across the entire peat profile was considerably enriched with postbomb C compared with the solid peat material. Overall, our results demonstrate little to no mobilization of ancient C stocks from this boreal peatland and a relatively large resilience of the source of aquatic C export to forecasted hydroclimatic changes.


Assuntos
Dióxido de Carbono/química , Carbono/química , Mudança Climática , Metano/química , Solo , Áreas Alagadas , Atmosfera , Ciclo do Carbono , Dióxido de Carbono/metabolismo , Monitoramento Ambiental , Gases , Metano/metabolismo
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