| 1. |
- Roberts, Nick, et al.
(författare)
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Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb carbonate geochronology : strategies, progress, and limitations
- 2020
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Ingår i: Geochronology. - : Copernicus Publications. - 2628-3719. ; 2, s. 33-61
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Tidskriftsartikel (refereegranskat)abstract
- Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb geochronology of carbonate minerals, calcite in particular, is rapidly gaining popularity as an absolute dating method. The high spatial resolution of LA-ICP-MS U–Pb carbonate geochronology has benefits over traditional isotope dilution methods, particularly for diagenetic and hydrothermal calcite, because uranium and lead are heterogeneously distributed on the sub-millimetre scale. At the same time, this can provide limitations to the method, as locating zones of radiogenic lead can be time-consuming and “hit or miss”. Here, we present strategies for dating carbonates with in situ techniques, through imaging and petrographic techniques to data interpretation; our examples are drawn from the dating of fracture-filling calcite, but our discussion is relevant to all carbonate applications. We review several limitations to the method, including open-system behaviour, variable initial-lead compositions, and U–daughter disequilibrium. We also discuss two approaches to data collection: traditional spot analyses guided by petrographic and elemental imaging and image-based dating that utilises LA-ICP-MS elemental and isotopic map data.
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| 2. |
- Hsiao, An-Shan, et al.
(författare)
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Arabidopsis cytosolic acyl-CoA-binding proteins ACBP4, ACBP5 and ACBP6 have overlapping but distinct roles in seed development
- 2014
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Ingår i: Bioscience Reports. - 0144-8463 .- 1573-4935. ; 34:6, s. 865-877
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Tidskriftsartikel (refereegranskat)abstract
- Eukaryotic cytosolic ACBPs (acyl-CoA-binding proteins) bind acyl-CoA esters and maintain a cytosolic acyl-CoA pool, but the thermodynamics of their protein-lipid interactions and physiological relevance in plants are not well understood. Arabidopsis has three cytosolic ACBPs which have been identified as AtACBP4, AtACBP5 and AtACBP6, and microarray data indicated that all of them are expressed in seeds; AtACBP4 is expressed in early embryogenesis, whereas AtACBP5 is expressed later. ITC (isothermal titration calorimetry) in combination with transgenic Arabidopsis lines were used to investigate the roles of these three ACBPs from Arabidopsis thaliana. The dissociation constants, stoichiometry and enthalpy change of AtACBP interactions with various acyl-CoA esters were determined using ITC. Strong binding of recombinant (r) AtACBP6 with long-chain acyl-CoA (C16-to C18-CoA) esters was observed with dissociation constants in the nanomolar range. However, the affinity of rAtACBP4 and rAtACBP5 to these acyl-CoA esters was much weaker (dissociation constants in the micromolar range), suggesting that they interact with acyl-CoA esters differently from rAtACBP6. When transgenic Arabidopsis expressing AtACBP6pro::GUS was generated, strong GUS (beta-glucuronidase) expression in cotyledonary-staged embryos and seedlings prompted us to measure the acyl-CoA contents of the acbp6 mutant. This mutant accumulated higher levels of C18:1-CoA and C18:1- and C18:2-CoAs in cotyledonary-staged embryos and seedlings, respectively, in comparison with the wild type. The acbp4acbp5acbp6 mutant showed the lightest seed weight and highest sensitivity to abscisic acid during germination, suggesting their physiological functions in seeds.
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| 3. |
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| 4. |
- Talamonti, Emanuela, et al.
(författare)
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Impairment of DHA synthesis alters the expression of neuronal plasticity markers and the brain inflammatory status in mice
- 2020
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Ingår i: The FASEB Journal. - 0892-6638 .- 1530-6860. ; 34:2, s. 2024-2040
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Tidskriftsartikel (refereegranskat)abstract
- Docosahexaenoic acid (DHA) is a omega-3 fatty acid typically obtained from the diet or endogenously synthesized through the action of elongases (ELOVLs) and desaturases. DHA is a key central nervous system constituent and the precursor of several molecules that regulate the resolution of inflammation. In the present study, we questioned whether the impaired synthesis of DHA affected neural plasticity and inflammatory status in the adult brain. To address this question, we investigated neural and inflammatory markers from mice deficient for ELOVL2 (Elovl2(-/-)), the key enzyme in DHA synthesis. From our findings, Elovl2(-/-) mice showed an altered expression of markers involved in synaptic plasticity, learning, and memory formation such as Egr-1, Arc1, and BDNF specifically in the cerebral cortex, impacting behavioral functions only marginally. In parallel, we also found that DHA-deficient mice were characterized by an increased expression of pro-inflammatory molecules, namely TNF, IL-1 beta, iNOS, caspase-1 as well as the activation and morphologic changes of microglia in the absence of any brain injury or disease. Reintroducing DHA in the diet of Elovl2(-/-) mice reversed such alterations in brain plasticity and inflammation. Hence, impairment of systemic DHA synthesis can modify the brain inflammatory and neural plasticity status, supporting the view that DHA is an essential fatty acid with an important role in keeping inflammation within its physiologic boundary and in shaping neuronal functions in the central nervous system.
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| 5. |
- Valegård, Karin, et al.
(författare)
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Structural and functional analyses of Rubisco from arctic diatom species reveal unusual posttranslational modifications
- 2018
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 293:34, s. 13033-13043
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic performance of the major CO2-assimilating enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), restricts photosynthetic productivity. Natural diversity in the catalytic properties of Rubisco indicates possibilities for improvement. Oceanic phytoplankton contain some of the most efficient Rubisco enzymes, and diatoms in particular are responsible for a significant proportion of total marine primary production as well as being a major source of CO2 sequestration in polar cold waters. Until now, the biochemical properties and three-dimensional structures of Rubisco from diatoms were unknown. Here, diatoms from arctic waters were collected, cultivated, and analyzed for their CO2-fixing capability. We characterized the kinetic properties of five and determined the crystal structures of four Rubiscos selected for their high CO2-fixing efficiency. The DNA sequences of the rbcL, and rbcS genes of the selected diatoms were similar, reflecting their close phylogenetic relationship. The V-max and K-m for the oxygenase and carboxylase activities at 25 degrees C and the specificity factors (S-c/o) at 15, 25, and 35 degrees C were determined. The S-c/o values were high, approaching those of mono- and dicot plants, thus exhibiting good selectivity for CO(2 )relative to O-2. Structurally, diatom Rubiscos belong to form I C/D, containing small subunits characterized by a short beta A-beta B loop and a C-terminal extension that forms a beta-hairpin structure (beta E-beta F loop). Of note, the diatom Rubiscos featured a number of posttranslational modifications of the large subunit, including 4-hydroxyproline, beta-hydroxyleucine, hydroxylated and nitrosylated cysteine, mono- and dihydroxylated lysine, and trimethylated lysine. Our studies suggest adaptation toward achieving efficient CO2 fixation in arctic diatom Rubiscos.
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| 6. |
- Zadravec, Damir, et al.
(författare)
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Dominant negative effect on male fertility and sperm maturation by haploinsufficiency of ELOVL2 in mouse
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- ELOVL2 is a member of the mammalian microsomal enzyme family (ELOVL) involved in the elongation of very long-chain fatty acids (VLCFAs) including polyunsaturated fatty acids (PUFAs). Specifically, ELOVL2 is suggested to mediate the rate-limiting condensation reaction in the elongation of PUFAs of C20 and C22 carbons in length. These PUFAs are required for various physiological functions including, regulation of the composition and fluidity of cell membranes, signalling and gene expression. Moreover, certain PUFAs can be oxygenated forming eicosanoids which are implicated in a variety of signalling pathways. The expression of Elovl2 is highest in testis and liver, but significant amounts of transcripts can also be found in kidney, brain, lung and white adipose tissue. Here, we show that ablation of Elovl2 in mice results in a complete absence of VLCPUFAs with 24-30 carbon atoms of the n-6 family in the testis, and that these fatty acids are indispensable for normal spermatogenesis and fertility. Ablation of Elovl2 was associated with a complete arrest of spermatogenesis with seminiferous tubule displaying only spermatogonia and primary spermatocytes without further germinal cells. The Elovl2+/- mice exhibited abnormal sperm morphology with rounded, condensed head, instead of the normal elongated and hooked head seen in wild-type mice. Intercrosses of Elovl2+/- mice displayed both pre- and post-meiotic deficiency of spermatogenesis. These results indicate a novel mechanism involving ELOVL2-derived fatty acids in mammalian spermatogenesis.
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| 7. |
- Zadravec, Damir, et al.
(författare)
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ELOVL2 controls the level of n-6 28:5 and 30:5 fatty acids in testis : a prerequisite for male fertility and sperm maturation in mice
- 2011
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Ingår i: Journal of Lipid Research. - 0022-2275 .- 1539-7262. ; 52:2, s. 245-255
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Tidskriftsartikel (refereegranskat)abstract
- ELOVL2 is a member of the mammalian microsomal ELOVL fatty acid enzyme family, involved in the elongation of very long-chain fatty acids including PUFAs required for various cellular functions in mammals. Here, we used ELOVL2-ablated (Elovl2(-/-)) mice to show that the PUFAs with 24-30 carbon atoms of the ω-6 family in testis are indispensable for normal sperm formation and fertility in male mice. The lack of Elovl2 was associated with a complete arrest of spermatogenesis, with seminiferous tubules displaying only spermatogonia and primary spermatocytes without further germinal cells. Furthermore, based on acyl-CoA profiling, heterozygous Elovl2(+/-) male mice exhibited haploinsufficiency, with reduced levels of C28:5 and C30:5n-6 PUFAs, which gave rise to impaired formation and function of haploid spermatides. These new insights reveal a novel mechanism involving ELOVL2-derived PUFAs in mammals and previously unrecognized roles for C28 and C30 n-6 PUFAs in male fertility. In accordance with the function suggested for ELOVL2, the Elovl2(-/-) mice show distorted levels of serum C20 and C22 PUFAs from both the n-3 and the n-6 series. However, dietary supplementation with C22:6n-3 could not restore male fertility to Elovl2(+/-) mice, suggesting that the changes in n-6 fatty acid composition seen in the testis of the Elovl2(+/-) mice, cannot be compensated by increased C22:6n-3 content.
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