| 1. |
- Petkevicius, K., et al.
(författare)
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TLCD1 and TLCD2 regulate cellular phosphatidylethanolamine composition and promote the progression of non-alcoholic steatohepatitis
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- The regulation of cellular phosphatidylethanolamine (PE) acyl chain composition is poorly understood. Here, the authors show that TLCD1 and TLCD2 proteins mediate the formation of monounsaturated fatty acid-containing PE species and promote the progression of non-alcoholic steatohepatitis. The fatty acid composition of phosphatidylethanolamine (PE) determines cellular metabolism, oxidative stress, and inflammation. However, our understanding of how cells regulate PE composition is limited. Here, we identify a genetic locus on mouse chromosome 11, containing two poorly characterized genes Tlcd1 and Tlcd2, that strongly influences PE composition. We generated Tlcd1/2 double-knockout (DKO) mice and found that they have reduced levels of hepatic monounsaturated fatty acid (MUFA)-containing PE species. Mechanistically, TLCD1/2 proteins act cell intrinsically to promote the incorporation of MUFAs into PEs. Furthermore, TLCD1/2 interact with the mitochondria in an evolutionarily conserved manner and regulate mitochondrial PE composition. Lastly, we demonstrate the biological relevance of our findings in dietary models of metabolic disease, where Tlcd1/2 DKO mice display attenuated development of non-alcoholic steatohepatitis compared to controls. Overall, we identify TLCD1/2 proteins as key regulators of cellular PE composition, with our findings having broad implications in understanding and treating disease.
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| 2. |
- Chi Fru, Ernest, et al.
(författare)
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Biogenicity of an Early Quaternary iron formation, Milos Island, Greece
- 2015
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Ingår i: Geobiology. - : Wiley. - 1472-4677 .- 1472-4669. ; 13:3, s. 225-244
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Tidskriftsartikel (refereegranskat)abstract
- A ~2.0-million-year-old shallow-submarine sedimentary deposit on Milos Island, Greece, harbours an unmetamorphosed fossiliferous iron formation (IF) comparable to Precambrian banded iron formations (BIFs). This Milos IF holds the potential to provide clues to the origin of Precambrian BIFs, relative to biotic and abiotic processes. Here, we combine field stratigraphic observations, stable isotopes of C, S and Si, rock petrography and microfossil evidence from a ~5-m-thick outcrop to track potential biogeochemical processes that may have contributed to the formation of the BIF-type rocks and the abrupt transition to an overlying conglomerate-hosted IF (CIF). Bulk δ13C isotopic compositions lower than -25‰ provide evidence for biological contribution by the Calvin and reductive acetyl–CoA carbon fixation cycles to the origin of both the BIF-type and CIF strata. Low S levels of ~0.04 wt.% combined with δ34S estimates of up to ~18‰ point to a non-sulphidic depository. Positive δ30Si records of up to +0.53‰ in the finely laminated BIF-type rocks indicate chemical deposition on the seafloor during weak periods of arc magmatism. Negative δ30Si data are consistent with geological observations suggesting a sudden change to intense arc volcanism potentially terminated the deposition of the BIF-type layer. The typical Precambrian rhythmic rocks of alternating Fe- and Si-rich bands are associated with abundant and spatially distinct microbial fossil assemblages. Together with previously proposed anoxygenic photoferrotrophic iron cycling and low sedimentary N and C potentially connected to diagenetic denitrification, the Milos IF is a biogenic submarine volcano-sedimentary IF showing depositional conditions analogous to Archaean Algoma-type BIFs.
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| 3. |
- Cunningham, J.A., et al.
(författare)
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Distinguishing geology from biology in the Ediacaran Doushantuo biota relaxes constraints on the timing of the origin of bilaterians.
- 2012
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Ingår i: Proceedings of the Royal Society. B. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 279:1737, s. 2369-2376
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Tidskriftsartikel (refereegranskat)abstract
- The Ediacaran Doushantuo biota has yielded fossils that include the oldest widely accepted record of the animal evolutionary lineage, as well as specimens with alleged bilaterian affinity. However, these systematic interpretations are contingent on the presence of key biological structures that have been reinterpreted by some workers as artefacts of diagenetic mineralization. On the basis of chemistry and crystallographic fabric, we characterize and discriminate phases of mineralization that reflect: (i) replication of original biological structure, and (ii) void-filling diagenetic mineralization. The results indicate that all fossils from the Doushantuo assemblage preserve a complex me´lange of mineral phases, even where subcellular anatomy appears to be preserved. The findings allow these phases to be distinguished in more controversial fossils, facilitating a critical re-evaluation of the Doushantuo fossil assemblage and its implications as an archive of Ediacaran animal diversity. We find that putative subcellular structures exhibit fabrics consistent with preservation of original morphology. Cells in later developmental stages are not in original configuration and are therefore uninformative concerning gastrulation. Key structures used to identify Doushantuo bilaterians can be dismissed as late diagenetic artefacts. Therefore, when diagenetic mineralization is considered, there is no convincing evidence for bilaterians in the Doushantuo assemblage.
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| 4. |
- Little, Crispin T. S., et al.
(författare)
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A late Paleoproterozoic (1.74 Ga) deep-sea, low-temperature, iron-oxidizing microbial hydrothermal vent community from Arizona, USA
- 2021
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Ingår i: Geobiology. - : John Wiley & Sons. - 1472-4677 .- 1472-4669. ; 19:3, s. 228-249
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Tidskriftsartikel (refereegranskat)abstract
- Modern marine hydrothermal vents occur in a wide variety of tectonic settings and are characterized by seafloor emission of fluids rich in dissolved chemicals and rapid mineral precipitation. Some hydrothermal systems vent only low-temperature Fe-rich fluids, which precipitate deposits dominated by iron oxyhydroxides, in places together with Mn-oxyhydroxides and amorphous silica. While a proportion of this mineralization is abiogenic, most is the result of the metabolic activities of benthic, Fe-oxidizing bacteria (FeOB), principally belonging to the Zetaproteobacteria. These micro-organisms secrete micrometer-scale stalks, sheaths, and tubes with a variety of morphologies, composed largely of ferrihydrite that act as sacrificial structures, preventing encrustation of the cells that produce them. Cultivated marine FeOB generally require neutral pH and microaerobic conditions to grow. Here, we describe the morphology and mineralogy of filamentous microstructures from a late Paleoproterozoic (1.74 Ga) jasper (Fe-oxide- silica) deposit from the Jerome area of the Verde mining district in central Arizona, USA, that resemble the branching tubes formed by some modern marine FeOB. On the basis of this comparison, we interpret the Jerome area filaments as having formed by FeOB on the deep seafloor, at the interface of weakly oxygenated seawater and low-temperature Fe-rich hydrothermal fluids. We compare the Jerome area filaments with other purported examples of Precambrian FeOB and discuss the implications of their presence for existing redox models of Paleoproterozoic oceans during the “Boring Billion.”
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| 5. |
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| 6. |
- Ahlberg, Per, et al.
(författare)
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Phosphatised olenid trilobites and associated fauna from the Upper Cambrian of Vastergotland, Sweden
- 2005
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Ingår i: Acta Palaeontologica Polonica. - 0567-7920. ; 50:3, s. 429-440
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Tidskriftsartikel (refereegranskat)abstract
- Secondarily phosphatised olenid trilobites from organic-rich limestones (orsten) in the Furongian (Upper Cambrian) of Vastergotland, south-central Sweden, are described and illustrated. All trilobites originate from the Peltura scarabaeoides Zone and were collected on the western slope of Kinnekulle. Only the dorsal exoskeletons have become secondarily phosphatised, and the ventral appendages are not preserved. Yet the material is otherwise remarkably well preserved and reveals the morphology of the olenid trilobites in greater detail than hitherto known. Species belonging to the genera Ctenopyge, Sphaerophthalmus, Parabolina, and Peltura are identified, and several juvenile specimens are present in the material. The material is disarticulated and fragmentary, and it has only been possible to identify a few specimens to species level. In addition to chaetognaths and conodonts, the trilobites are associated with pelmatozoan columnals, a possible camaroid, and fossils of uncertain affinities. These fossils, along with a probable conulariid fragment from the Peltura minor Zone, are also described and discussed. The presence of a benthic fauna of pelmatozoans, and possible conulariids and camaroids, indicates that at least parts of the Peltura zones were deposited during dysoxic rather than anoxic periods. Moreover, the sea floor must have been firm enough to allow colonisation by sessile organisms.
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| 7. |
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| 9. |
- Bengtson, S, et al.
(författare)
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Unguided clinical and actuarial assessment of re-offending risk: a direct comparison with sex offenders in Denmark
- 2007
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Ingår i: Sexual abuse : a journal of research and treatment. - : SAGE Publications. - 1079-0632. ; 19:2, s. 135-153
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Tidskriftsartikel (refereegranskat)abstract
- Meta-analyses suggest that actuarial risk assessments outperform unguided clinical judgment for prediction of recidivism in criminal offenders. However, there is a lack of direct comparisons of the predictive accuracy of clinical judgment and actuarial risk scales for sexual offenders. We followed up 121 male sex offenders (≥18 years) subjected to pre-trial forensic psychiatric assessment in Denmark in 1978-1992 (mean post-detainment time=16.4 years) to compare the predictive validity of unstructured clinical judgment of recidivism risk with that of the well-established Static-99 (Hanson and Thornton, Law and Human Behavior 24:119-136, 2000) and an extension of the Static-99, the Static-2002 (Hanson and Thornton, Notes on the development of Static-2002 (Rep. No. 2003-01), Public Safety and Emergency Preparedness Canada, Ottawa, Canada, 2003). The predictive accuracy of unguided judgment did not exceed chance for any sexual, severe sexual or any violent (sexual or non-sexual) reconviction (AUCs of the ROC curve=0.52, 95%CI=0.41-0.63; 0.50, 95%CI=0.34-0.67; and 0.57, 95%CI= 0.40-0.73, respectively). In contrast, all three outcomes were predicted significantly better than chance by the Static-99 (AUC=0.62, 95%CI=0.52-0.72; 0.72, 95%CI= 0.59-0.84; and 0.71, 95%CI=0.56-0.86) and the Static-2002 (AUC=0.67, 95%CI= 0.57-0.77; 0.69, 95%CI=0.56-0.83; and 0.70, 95%CI=0.55-0.86). Static-99 out-performed clinical judgment for sexual recidivision (χ2=5.11, df=1, p<.05). The Static-2002 was significantly more accurate for the prediction of any sexual recidivism as compared to unguided clinical judgment but its advantage fell just short of statistical significance for severe sexual recidivism (χ2=3.56, df=1, p=0.06). When tested for recidivism within 2 years, none of the three prediction methods yielded results significantly better than chance for any outcome. This direct trial of the unguided clinical method argues against its continued use for risk assessment of sexual offenders.
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| 10. |
- Campbell, Jocelyn, et al.
(författare)
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Does exogenous carbon extend the realized niche of canopy lichens? Evidence from sub-boreal forests in British Columbia
- 2013
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Ingår i: Ecology. - : Wiley. - 0012-9658. ; 94:5, s. 1186-1195
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Tidskriftsartikel (refereegranskat)abstract
- Foliose lichens with cyanobacterial bionts (bipartite and tripartite) form a distinct assemblage of epiphytes strongly associated with humid microclimatic conditions in inland British Columbia. Previous research showed that these cyano- and cephalolichen communities are disproportionately abundant and species-rich on conifer saplings beneath Populus compared to beneath other tree species. More revealing, lichens with cyanobacterial bionts were observed beneath Populus even in stands that did not otherwise support them. We experimentally test the hypothesis that this association is due to the interception of glucose-rich nectar that is exuded from Populus extra-floral nectaries (EFN). Using CO2 flux measurements and phospholipid fatty acid (PLFA) analysis with experimental applications of C-13(6)-labeled glucose, we demonstrate that cyano-and cephalolichens have a strong respiratory response to glucose. Lichens treated with glucose had lower net photosynthesis and higher establishment rates than control thalli. Furthermore, lichens with cyanobacterial bionts rapidly incorporate exogenous C-13 into lichen fatty acid tissues. A large proportion of the C-13 taken up by the lichens was incorporated into fungal biomarkers, suggesting that the mycobiont absorbed and assimilated the majority of applied C-13(6) glucose. Our observations suggest that both cyanolichens and cephalolichens may utilize an exogenous source of glucose, made available by poplar EFNs. The exogenous C may enable these lichens to become established by providing a source of C for fungal respiration despite drought-induced inactivity of the cyanobacterial partner. As such, the mycobiont may adopt an alternative nutritional strategy, using available exogenous carbon to extend its realized niche.
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