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Keret R, Schliephack PM, Stangler DF, Seifert T, Kahle HP, Drew DM, Hills PN. An open-source machine-learning approach for obtaining high-quality quantitative wood anatomy data from E. grandis and P. radiata xylem. Plant Sci 2024; 340:111970. [PMID: 38163623 DOI: 10.1016/j.plantsci.2023.111970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 12/26/2023] [Accepted: 12/27/2023] [Indexed: 01/03/2024]
Abstract
Quantitative wood anatomy is a subfield in dendrochronology that requires effective open-source image analysis tools. In this research, the bioimage analysis software QuPath (v0.4.4) is introduced as a candidate for accurately quantifying the cellular properties of the xylem in an automated manner. Additionally, the potential of QuPath to detect the transition of early- to latewood tracheids over the growing season was evaluated to assess a potential application in dendroecological studies. Various algorithms in QuPath were optimized to quantify different xylem cell types in Eucalyptus grandis and the transition of early- to latewood tracheids in Pinus radiata. These algorithms were coded into cell detection scripts for automatic quantification of stem microsections and compared to a manually curated method to assess the accuracy of the cell detections. The automatic cell detection approach, using QuPath, has been validated to be reproducible with an acceptable error when assessing fibers, vessels, early- and latewood tracheids. However, further optimization for parenchyma is still required. This proposed method developed in QuPath provides a scalable and accurate approach for quantifying anatomical features in stem microsections. With minor amendments to the detection and classification algorithms, this strategy is likely to be viable in other plant species.
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Affiliation(s)
- Rafael Keret
- Institute for Plant Biotechnology, Department of Genetics, Stellenbosch University, Private Bag X1, Matieland 7602, Stellenbosch, South Africa; Department of Forestry and Wood Sciences, Stellenbosch University, Bosman St, 7599, Stellenbosch central, South Africa
| | - Paul M Schliephack
- Chair of Forest Growth and Dendroecology, Institute of Forest Sciences, University of Freiburg, Tennenbacher Str. 4, Freiburg im Breisgau, Germany
| | - Dominik F Stangler
- Chair of Forest Growth and Dendroecology, Institute of Forest Sciences, University of Freiburg, Tennenbacher Str. 4, Freiburg im Breisgau, Germany
| | - Thomas Seifert
- Department of Forestry and Wood Sciences, Stellenbosch University, Bosman St, 7599, Stellenbosch central, South Africa; Chair of Forest Growth and Dendroecology, Institute of Forest Sciences, University of Freiburg, Tennenbacher Str. 4, Freiburg im Breisgau, Germany
| | - Hans-Peter Kahle
- Chair of Forest Growth and Dendroecology, Institute of Forest Sciences, University of Freiburg, Tennenbacher Str. 4, Freiburg im Breisgau, Germany
| | - David M Drew
- Department of Forestry and Wood Sciences, Stellenbosch University, Bosman St, 7599, Stellenbosch central, South Africa.
| | - Paul N Hills
- Institute for Plant Biotechnology, Department of Genetics, Stellenbosch University, Private Bag X1, Matieland 7602, Stellenbosch, South Africa
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2
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Kinzinger L, Mach J, Haberstroh S, Schindler Z, Frey J, Dubbert M, Seeger S, Seifert T, Weiler M, Orlowski N, Werner C. Interaction between beech and spruce trees in temperate forests affects water use, root water uptake pattern and canopy structure. Tree Physiol 2024; 44:tpad144. [PMID: 38070177 DOI: 10.1093/treephys/tpad144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 12/01/2023] [Indexed: 02/09/2024]
Abstract
Beneficial and negative effects of species interactions can strongly influence water fluxes in forest ecosystems. However, little is known about how trees dynamically adjust their water use when growing with interspecific neighbours. Therefore, we investigated the interaction effects between Fagus sylvatica (European beech) and Picea abies (Norway spruce) on water-use strategies and aboveground structural characteristics. We used continuous in situ isotope spectroscopy of xylem and soil water to investigate source water dynamics and root water uptake depths. Picea abies exhibited a reduced sun-exposed crown area in equally mixed compared with spruce-dominated sites, which was further correlated to a reduction in sap flow of -14.5 ± 8.2%. Contrarily, F. sylvatica trees showed +13.3 ± 33.3% higher water fluxes in equally mixed compared with beech-dominated forest sites. Although a significantly higher crown interference by neighbouring trees was observed, no correlation of water fluxes and crown structure was found. High time-resolved xylem δ2H values showed a large plasticity of tree water use (-74.1 to -28.5‰), reflecting the δ2H dynamics of soil and especially precipitation water sources. Fagus sylvatica in equally mixed sites shifted water uptake to deeper soil layers, while uptake of fresh precipitation was faster in beech-dominated sites. Our continuous in situ water stable isotope measurements traced root water uptake dynamics at unprecedented temporal resolution, indicating highly dynamic use of water sources in response to precipitation and to neighbouring species competition. Understanding this plasticity may be highly relevant in the context of increasing water scarcity and precipitation variability under climate change.
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Affiliation(s)
- Laura Kinzinger
- Chair of Ecosystem Physiology, Faculty of Environment and Natural Resources, University of Freiburg, Georges-Köhler-Allee, 79110 Freiburg, Germany
| | - Judith Mach
- Chair of Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Friedrichstraße 39, 79089 Freiburg, Germany
| | - Simon Haberstroh
- Chair of Ecosystem Physiology, Faculty of Environment and Natural Resources, University of Freiburg, Georges-Köhler-Allee, 79110 Freiburg, Germany
| | - Zoe Schindler
- Chair of Forest Growth and Dendroecology, Faculty of Environment and Natural Resources, University of Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany
| | - Julian Frey
- Chair of Forest Growth and Dendroecology, Faculty of Environment and Natural Resources, University of Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany
| | - Maren Dubbert
- IBG, PB 1 'Landschaftsprozesse', Leibniz Zentrum für Agrarlandschaftsforschung (ZALF) e. V, Eberswalder Straße 84, 15374 Müncheberg, Germany
| | - Stefan Seeger
- Chair of Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Friedrichstraße 39, 79089 Freiburg, Germany
- Soil Physics, Department of Crop Sciences, University of Göttingen, Grisebachstraße 6, 37077 Gottingen, Germany
| | - Thomas Seifert
- Chair of Forest Growth and Dendroecology, Faculty of Environment and Natural Resources, University of Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany
- Department of Forest and Wood Science, Stellenbosch University, Bosman Street, 7599 Stellenbosch, South Africa
| | - Markus Weiler
- Chair of Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Friedrichstraße 39, 79089 Freiburg, Germany
| | - Natalie Orlowski
- Chair of Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Friedrichstraße 39, 79089 Freiburg, Germany
- Chair of Site Ecology and Plant Nutrition, Institute of Soil Science and Site Ecology, TU Dresden, Pienner Strasse 19, Tharandt 01737, Germany
| | - Christiane Werner
- Chair of Ecosystem Physiology, Faculty of Environment and Natural Resources, University of Freiburg, Georges-Köhler-Allee, 79110 Freiburg, Germany
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3
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Mensah S, Dimobe K, Noulèkoun F, van der Plas F, Seifert T. Phylogenetic diversity and community wide-trait means offer different insights into mechanisms regulating aboveground carbon storage. Sci Total Environ 2024; 907:167905. [PMID: 37858820 DOI: 10.1016/j.scitotenv.2023.167905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 10/14/2023] [Accepted: 10/16/2023] [Indexed: 10/21/2023]
Abstract
Both attributes of functional traits and phylogenetic diversity influence ecosystem functions, but which of these factors is most important is still poorly understood in natural systems. Using data from West African forests and tree savannas, we analyse how (i) phylogenetic diversity complements attributes of functional traits in explaining aboveground carbon (AGC); (ii) phylogenetic diversity relates with attributes of functional traits along gradients of phylogenetic signal; and (iii) pathways between phylogenetic diversity and attributes of functional traits relate AGC to soil and climate. Phylogenetic diversity was measured as standardised effect size of Mean Pairwise Distance (sesMPD) and Mean Nearest Taxon Distance (sesMNTD). Functional dispersion (FDis) and community weighted mean (CWM) were calculated for four traits related to leaf economics spectrum and plant life-history. Functional traits-based models explained 11 % of AGC variability. With two out of the four traits being phylogenetically conserved, incorporating phylogenetic diversity in the models increased the explained variance in AGC by 15 %. The slope of phylogenetic diversity-trait relationship was more responsive to trait conservatism for FDis than CWM. AGC was positively influenced by sesMPD and CWM of plant maximum height. In turn, CWM of plant maximum height increased with higher soil nitrogen and climate moisture, whereas sesMPD was negatively related with climate moisture. Although FDis was positively associated with sesMPD, it was not as important as sesMPD and CWM of plant maximum height in influencing and relating AGC to soil nitrogen and climate moisture. Our results suggest that phylogenetic diversity is important for AGC but does not fully reflect the functional mechanisms pertaining to community-wide trait means. The study also demonstrates the role of environment in regulating AGC, which operates through differences in community fitness driven by tall plant stature, and evolutionary processes whereby closely related species are maintained in less arid environments.
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Affiliation(s)
- Sylvanus Mensah
- Chair of Forest Growth and Dendroecology, Albert-Ludwigs-Universität Freiburg, Freiburg im Breisgau, Germany; Laboratoire de Biomathématiques et d'Estimations Forestières, Faculté des Sciences Agronomiques, Université d'Abomey Calavi, Cotonou, Benin.
| | - Kangbéni Dimobe
- Département des Eaux, Forêts et Environnement, Institut des Sciences de l'Environnement et du Développement Rural, Université de Dédougou, BP 176 Dédougou, Burkina Faso
| | - Florent Noulèkoun
- Department of Environmental Science and Ecological Engineering, Korea University, 145 Anamro, Seongbukgu, Seoul 02841, Republic of Korea
| | - Fons van der Plas
- Plant Ecology and Nature Conservation Group, Wageningen University, the Netherlands
| | - Thomas Seifert
- Chair of Forest Growth and Dendroecology, Albert-Ludwigs-Universität Freiburg, Freiburg im Breisgau, Germany; Department of Forest and Wood Science, Stellenbosch University, 7602 Matieland, South Africa
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4
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Mensah S, Noulèkoun F, Dimobe K, Seifert T, Glèlè Kakaï R. Climate and soil effects on tree species diversity and aboveground carbon patterns in semi-arid tree savannas. Sci Rep 2023; 13:11509. [PMID: 37460693 DOI: 10.1038/s41598-023-38225-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 07/05/2023] [Indexed: 07/20/2023] Open
Abstract
Climatic and edaphic effects are increasingly being discussed in the context of biodiversity-ecosystem functioning. Here we use data from West African semi-arid tree savannas and contrasting climatic conditions (lower vs. higher mean annual precipitation-MAP and mean annual temperature-MAT) to (1) determine how climate modulates the effects of species richness on aboveground carbon (AGC); (2) explore how species richness and AGC relate with soil variables in these contrasting climatic conditions; and (3) assess how climate and soil influence directly, and/or indirectly AGC through species richness and stand structural attributes such as tree density and size variation. We find that greater species richness is generally associated with higher AGC, but more strongly in areas with higher MAP, which also have greater stem density. There is a climate-related influence of soils on AGC, which decreases from lower to higher MAP conditions. Variance partitioning analyses and structural equation modelling show that, across all sites, MAP, relative to soils, has smaller effect on AGC, mediated by stand structural attributes whereas soil texture and fertility explain 14% of variations in AGC and influence AGC directly and indirectly via species richness and stand structural attributes. Our results highlight coordinated effects of climate and soils on AGC, which operated primarily via the mediation role of species diversity and stand structures.
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Affiliation(s)
- Sylvanus Mensah
- Laboratoire de Biomathématiques et d'Estimations Forestières, Faculté des Sciences Agronomiques, Université d'Abomey Calavi, Cotonou, Benin.
- Chair of Forest Growth, Albert-Ludwigs-Universität Freiburg, Freiburg im Breisgau, Germany.
| | - Florent Noulèkoun
- Department of Environmental Science and Ecological Engineering, Korea University, 145 Anamro, Seongbukgu, Seoul, 02841, Korea
| | - Kangbéni Dimobe
- Institut des Sciences de l'Environnement et du Développement Rural, Université de Dédougou, BP 176, Dédougou, Burkina Faso
| | - Thomas Seifert
- Chair of Forest Growth, Albert-Ludwigs-Universität Freiburg, Freiburg im Breisgau, Germany
- Department of Forest and Wood Science, Stellenbosch University, Matieland, 7602, South Africa
| | - Romain Glèlè Kakaï
- Laboratoire de Biomathématiques et d'Estimations Forestières, Faculté des Sciences Agronomiques, Université d'Abomey Calavi, Cotonou, Benin
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5
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Fischer C, Schackert S, Seifert T, Schweizer C, Fuchs M. Experiments and Modeling on the Stain-Controlled Time- and Temperature-Dependent Cyclic Ratchetting Plasticity of the Nickel-Based Superalloy IN100. Materials (Basel) 2023; 16:1888. [PMID: 36903003 PMCID: PMC10004477 DOI: 10.3390/ma16051888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 02/20/2023] [Accepted: 02/22/2023] [Indexed: 06/18/2023]
Abstract
In this paper, the time- and temperature-dependent cyclic ratchetting plasticity of the nickel-based alloy IN100 is experimentally investigated in strain-controlled experiments in the temperature range from 300 °C to 1050 °C. To this end, uniaxial material tests are performed with complex loading histories designed to activate phenomena as strain rate dependency, stress relaxation as well as the Bauschinger effect, cyclic hardening and softening, ratchetting and recovery from hardening. Plasticity models with different levels of complexity are presented that consider these phenomena, and a strategy is derived to determine the multitude of temperature-dependent material properties of the models in a step-by-step procedure based on sub-sets of experimental data of isothermal experiments. The models and the material properties are validated based on the results of non-isothermal experiments. A good description of the time- and temperature-dependent cyclic ratchetting plasticity of IN100 is obtained for isothermal as well as non-isothermal loading with models including ratchetting terms in the kinematic hardening law and the material properties obtained with the proposed strategy.
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Affiliation(s)
- Carl Fischer
- Institute for Digital Engineering and Production (IDEeP), Offenburg University of Applied Sciences, Badstraße 24, 77652 Offenburg, Germany
- Fraunhofer Institute for Mechanics of Materials IWM, Wöhlerstraße 11, 79108 Freiburg, Germany
| | - Sophie Schackert
- Fraunhofer Institute for Mechanics of Materials IWM, Wöhlerstraße 11, 79108 Freiburg, Germany
| | - Thomas Seifert
- Institute for Digital Engineering and Production (IDEeP), Offenburg University of Applied Sciences, Badstraße 24, 77652 Offenburg, Germany
| | - Christoph Schweizer
- Fraunhofer Institute for Mechanics of Materials IWM, Wöhlerstraße 11, 79108 Freiburg, Germany
| | - Martin Fuchs
- Fraunhofer Institute for Mechanics of Materials IWM, Wöhlerstraße 11, 79108 Freiburg, Germany
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6
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Schlayer M, Warwas M, Seifert T. A Temperature-Dependent Viscoplasticity Model for the Hot Work Steel X38CrMoV5-3, Including Thermal and Cyclic Softening under Thermomechanical Fatigue Loading. Materials (Basel) 2023; 16:994. [PMID: 36770001 PMCID: PMC9918193 DOI: 10.3390/ma16030994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/11/2023] [Accepted: 01/13/2023] [Indexed: 06/18/2023]
Abstract
In this paper, a temperature-dependent viscoplasticity model is presented that describes thermal and cyclic softening of the hot work steel X38CrMoV5-3 under thermomechanical fatigue loading. The model describes the softening state of the material by evolution equations, the material properties of which can be determined on the basis of a defined experimental program. A kinetic model is employed to capture the effect of coarsening carbides and a new isotropic cyclic softening model is developed that takes history effects during thermomechanical loadings into account. The temperature-dependent material properties of the viscoplasticity model are determined on the basis of experimental data measured in isothermal and thermomechanical fatigue tests for the material X38CrMoV5-3 in the temperature range between 20 and 650 ∘C. The comparison of the model and an existing model for isotropic softening shows an improved description of the softening behavior under thermomechanical fatigue loading. A good overall description of the experimental data is possible with the presented viscoplasticity model, so that it is suited for the assessment of operating loads of hot forging tools.
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Affiliation(s)
- Markus Schlayer
- Institute for Digital Engineering and Production (IDEeP), Offenburg University of Applied Sciences, Badstraße 24, 77652 Offenburg, Germany
| | - Marc Warwas
- Fraunhofer Institute for Mechanics of Materials IWM, Wöhlerstraße 11, 79108 Freiburg, Germany
| | - Thomas Seifert
- Institute for Digital Engineering and Production (IDEeP), Offenburg University of Applied Sciences, Badstraße 24, 77652 Offenburg, Germany
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Miller TW, Stangler DF, Larysch E, Honer H, Puhlmann H, Schindler D, Jung C, Seifert T, Rigling A, Kahle HP. Later growth onsets or reduced growth rates: What characterises legacy effects at the tree-ring level in conifers after the severe 2018 drought? Sci Total Environ 2023; 854:158703. [PMID: 36099953 DOI: 10.1016/j.scitotenv.2022.158703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 09/06/2022] [Accepted: 09/08/2022] [Indexed: 06/15/2023]
Abstract
Severe drought events negatively affect tree growth and often cause legacy effects, expressed by smaller tree rings in the post-drought recovery years. While the pattern of reduced tree-ring widths is frequently described the processes underlying such legacy effects, i.e., whether it is due to shorter growth periods or lower growth rates, remains unclear and is investigated in this study. To elucidate these post-drought effects, we examined radial stem growth dynamics monitored with precision band-dendrometers on 144 Douglas fir, Norway spruce and silver fir sample trees distributed along four elevational gradients in the Black Forest (Southwest Germany) during the post-drought years 2019 and 2020. Growth onset of all investigated species occurred between 11 and 24 days significantly earlier in 2020 compared to 2019. Modelling growth onset based on chilling and forcing units and taking the study year into account explained 88-98 % of the variance in the growth onset data. The highly significant effect of the study year (p < 0.001) led to the conclusion, that other factors than the prevailing site conditions (chilling and forcing units) must have triggered the earlier growth onset in 2020. On the other hand, for Douglas fir growth rates were significantly higher in 2020 compared to 2019 (2.9 μm d-1) and marginally significantly higher for silver fir (1.3 μm d-1), underlining the explanatory power of growth rate on recovery processes in general and suggesting that Douglas fir copes better with droughts, as it recovered faster. Growth dynamics at the beginning of the year showed limited growth for earlier growth onsets, which, however, could not explain the difference between the investigated years. Our results provide evidence that legacy effects of drought events are expressed by a delayed growth onset and a reduced growth rate in the post-drought year and that Douglas fir has a superior recovery potential.
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Affiliation(s)
- Tobias Walter Miller
- Institute of Forest Sciences, Chair of Forest Growth and Dendroecology, University of Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany.
| | - Dominik Florian Stangler
- Institute of Forest Sciences, Chair of Forest Growth and Dendroecology, University of Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany
| | - Elena Larysch
- Institute of Forest Sciences, Chair of Forest Growth and Dendroecology, University of Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany
| | - Harald Honer
- Institute of Forest Sciences, Chair of Forest Growth and Dendroecology, University of Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany
| | - Heike Puhlmann
- Department of Soil and Environment, Forest Research Institute Baden-Württemberg, Freiburg, Germany
| | - Dirk Schindler
- Environmental Meteorology, University of Freiburg, Werthmann-str. 10, 79085 Freiburg, Germany
| | - Christopher Jung
- Environmental Meteorology, University of Freiburg, Werthmann-str. 10, 79085 Freiburg, Germany
| | - Thomas Seifert
- Institute of Forest Sciences, Chair of Forest Growth and Dendroecology, University of Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany; Department for Forest and Wood Science, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa
| | - Andreas Rigling
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland; SwissForestLab, Birmensdorf, Switzerland; Institute of Terrestrial Ecology, ETH Zürich, Zürich, Switzerland
| | - Hans-Peter Kahle
- Institute of Forest Sciences, Chair of Forest Growth and Dendroecology, University of Freiburg, Tennenbacher Str. 4, 79106 Freiburg, Germany
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8
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Larysch E, Stangler DF, Puhlmann H, Rathgeber CBK, Seifert T, Kahle HP. The 2018 hot drought pushed conifer wood formation to the limit of its plasticity: Consequences for woody biomass production and tree ring structure. Plant Biol (Stuttg) 2022; 24:1171-1185. [PMID: 35277910 DOI: 10.1111/plb.13399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 01/24/2022] [Indexed: 06/14/2023]
Abstract
Hot droughts are expected to increase in Europe and disturb forest ecosystem functioning. Wood formation of trees has the potential to adapt to those events by compensatory mechanisms between the rates and durations of tracheid differentiation to form the typical pattern of vital wood anatomical structures. We monitored xylogenesis and measured wood anatomy of mature silver fir (Abies alba Mill.) and Scots pine (Pinus sylvestris L.) trees along an elevational gradient in the Black Forest during the hot drought year of 2018. We assessed the kinetics of tracheid differentiation and the final tracheid dimensions and quantified the relationship between rates and durations of cell differentiation over the growing season. Cell differentiation kinetics were decoupled, and temperature and water availability signals were imprinted in the tree ring structure. The sudden decline in woody biomass production provided evidence for a disruption in carbon sequestration processes due to heat and drought stress. Growth processes of Scots pine (pioneer species) were mainly affected by the spring drought, whereas silver fir (climax species) growth processes were more disturbed by the summer drought. Our study provides novel insights on the plasticity of wood formation and carbon allocation in temperate conifer tree species in response to extreme climatic events.
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Affiliation(s)
- E Larysch
- Chair of Forest Growth and Dendroecology, Albert-Ludwigs-University, Freiburg, Germany
| | - D F Stangler
- Chair of Forest Growth and Dendroecology, Albert-Ludwigs-University, Freiburg, Germany
| | - H Puhlmann
- Department of Soil and Environment, Forest Research Institute Baden-Württemberg, Freiburg, Germany
| | - C B K Rathgeber
- INRAE, SILVA, Université de Lorraine, AgroParisTech, Nancy, France
- Swiss Federal Research Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
| | - T Seifert
- Chair of Forest Growth and Dendroecology, Albert-Ludwigs-University, Freiburg, Germany
- Department of Forest and Wood Science, Stellenbosch University, Matieland, South Africa
| | - H-P Kahle
- Chair of Forest Growth and Dendroecology, Albert-Ludwigs-University, Freiburg, Germany
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9
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Haberstroh S, Werner C, Grün M, Kreuzwieser J, Seifert T, Schindler D, Christen A. Central European 2018 hot drought shifts scots pine forest to its tipping point. Plant Biol (Stuttg) 2022; 24:1186-1197. [PMID: 35869655 DOI: 10.1111/plb.13455] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 07/12/2022] [Indexed: 06/15/2023]
Abstract
The occurrence of hot drought, i.e. low water availability and simultaneous high air temperature, represents a severe threat to ecosystems. Here, we investigated how the 2018 hot drought in Central Europe caused a tipping point in tree and ecosystem functioning in a Scots pine (Pinus sylvestris L.) forest in southwest Germany. Measurements of stress indicators, such as needle water potential, carbon assimilation and volatile organic compound (VOC) emissions, of dominant P. sylvestris trees were deployed to evaluate tree functioning during hot drought. Ecosystem impact and recovery were assessed as ecosystem carbon exchange, normalized difference vegetation index (NDVI) from satellite data and tree mortality data. During summer 2018, needle water potentials of trees dropped to minimum values of -7.5 ± 0.2 MPa, which implied severe hydraulic impairment of P. sylvestris. Likewise, carbon assimilation and VOC emissions strongly declined after mid-July. Decreasing NDVI values from August 2018 onwards were detected, along with severe defoliation in P. sylvestris, impairing ecosystem carbon flux recovery in 2019, shifting the forest into a year-round carbon source. A total of 47% of all monitored trees (n = 368) died by September 2020. NDVI recovered to pre-2018 levels in 2019, likely caused by emerging broadleaved understorey species. The 2018 hot drought had severe negative impacts on P. sylvestris. The co-occurrence of unfavourable site-specific conditions with recurrent severe droughts resulted in accelerated mortality. Thus, the 2018 hot drought pushed the P. sylvestris stand towards its tipping point, with a subsequent vegetation shift to a broadleaf-dominated forest.
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Affiliation(s)
- S Haberstroh
- Ecosystem Physiology, Faculty of Environment and Natural Resources, University Freiburg, Freiburg, Germany
| | - C Werner
- Ecosystem Physiology, Faculty of Environment and Natural Resources, University Freiburg, Freiburg, Germany
| | - M Grün
- Ecosystem Physiology, Faculty of Environment and Natural Resources, University Freiburg, Freiburg, Germany
| | - J Kreuzwieser
- Ecosystem Physiology, Faculty of Environment and Natural Resources, University Freiburg, Freiburg, Germany
| | - T Seifert
- Forest Growth and Dendroecology, Faculty of Environment and Natural Resources, University Freiburg, Freiburg, Germany
- Department of Forest and Wood Science, Stellenbosch University, Matieland, South Africa
| | - D Schindler
- Environmental Meteorology, Faculty of Environment and Natural Resources, University Freiburg, Freiburg, Germany
| | - A Christen
- Environmental Meteorology, Faculty of Environment and Natural Resources, University Freiburg, Freiburg, Germany
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10
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Stangler DF, Miller TW, Honer H, Larysch E, Puhlmann H, Seifert T, Kahle HP. Multivariate drought stress response of Norway spruce, silver fir and Douglas fir along elevational gradients in Southwestern Germany. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.907492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The conifer tree species Norway spruce (Picea abies), silver fir (Abies alba) and Douglas fir (Pseudotsuga menziesii) are important elements in tree species composition and forest management of Central European forests, but their potential to thrive under anticipated climatic changes is still debated controversially. This study contributes a multivariate analysis of resilience components based on increment cores sampled at breast height of Norway spruce, silver fir and Douglas fir trees growing along elevational gradients in Southwestern Germany. We aimed to gain novel insights into the species-specific and elevational response of tree growth and wood density variables during the extreme drought events of the years 2003 and 2018. Our results for Norway spruce corroborate projections of its ongoing decline during climate change as the reductions of wood density and biomass production indicated high drought sensitivity at all elevations. Moreover, resilience indices of mean tree-ring density, maximum latewood density, tree-ring width and biomass production were even lower after the drought of 2018 compared to the previous drought of 2003. Silver fir, a potential substitute tree species for Norway spruce, showed unexpected results with resistance and resilience indices being significantly lower in 2018 compared to 2003 indicating that silver fir might be more vulnerable to drought than previously expected, especially at low elevations. In contrast, the superior growth rates and higher levels of drought tolerance of Douglas fir were especially pronounced during the drought of 2018 and visible across the entire elevational gradient, even though high coning intensity was present for all investigated tree species as a possible confounding factor to exacerbate the drought stress effects in the study region.
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11
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Sharma N, Welker D, Aghlmandi S, Maintz M, Zeilhofer HF, Honigmann P, Seifert T, Thieringer FM. A Multi-Criteria Assessment Strategy for 3D Printed Porous Polyetheretherketone (PEEK) Patient-Specific Implants for Orbital Wall Reconstruction. J Clin Med 2021; 10:3563. [PMID: 34441859 PMCID: PMC8397160 DOI: 10.3390/jcm10163563] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 08/02/2021] [Accepted: 08/10/2021] [Indexed: 12/18/2022] Open
Abstract
Pure orbital blowout fractures occur within the confines of the internal orbital wall. Restoration of orbital form and volume is paramount to prevent functional and esthetic impairment. The anatomical peculiarity of the orbit has encouraged surgeons to develop implants with customized features to restore its architecture. This has resulted in worldwide clinical demand for patient-specific implants (PSIs) designed to fit precisely in the patient's unique anatomy. Material extrusion or Fused filament fabrication (FFF) three-dimensional (3D) printing technology has enabled the fabrication of implant-grade polymers such as Polyetheretherketone (PEEK), paving the way for a more sophisticated generation of biomaterials. This study evaluates the FFF 3D printed PEEK orbital mesh customized implants with a metric considering the relevant design, biomechanical, and morphological parameters. The performance of the implants is studied as a function of varying thicknesses and porous design constructs through a finite element (FE) based computational model and a decision matrix based statistical approach. The maximum stress values achieved in our results predict the high durability of the implants, and the maximum deformation values were under one-tenth of a millimeter (mm) domain in all the implant profile configurations. The circular patterned implant (0.9 mm) had the best performance score. The study demonstrates that compounding multi-design computational analysis with 3D printing can be beneficial for the optimal restoration of the orbital floor.
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Affiliation(s)
- Neha Sharma
- Clinic of Oral and Cranio-Maxillofacial Surgery, University Hospital Basel, CH-4031 Basel, Switzerland; (N.S.); (H.-F.Z.)
- Medical Additive Manufacturing Research Group (Swiss MAM), Department of Biomedical Engineering, University of Basel, CH-4123 Allschwil, Switzerland; (D.W.); (M.M.); (P.H.)
| | - Dennis Welker
- Medical Additive Manufacturing Research Group (Swiss MAM), Department of Biomedical Engineering, University of Basel, CH-4123 Allschwil, Switzerland; (D.W.); (M.M.); (P.H.)
| | - Soheila Aghlmandi
- Basel Institute for Clinical Epidemiology and Biostatistics, Department of Clinical Research, University Hospital Basel, CH-4031 Basel, Switzerland;
| | - Michaela Maintz
- Medical Additive Manufacturing Research Group (Swiss MAM), Department of Biomedical Engineering, University of Basel, CH-4123 Allschwil, Switzerland; (D.W.); (M.M.); (P.H.)
- Institute for Medical Engineering and Medical Informatics, University of Applied Sciences and Arts Northwestern Switzerland, CH-4132 Muttenz, Switzerland
| | - Hans-Florian Zeilhofer
- Clinic of Oral and Cranio-Maxillofacial Surgery, University Hospital Basel, CH-4031 Basel, Switzerland; (N.S.); (H.-F.Z.)
| | - Philipp Honigmann
- Medical Additive Manufacturing Research Group (Swiss MAM), Department of Biomedical Engineering, University of Basel, CH-4123 Allschwil, Switzerland; (D.W.); (M.M.); (P.H.)
- Hand Surgery, Cantonal Hospital Baselland, CH-4410 Liestal, Switzerland
- Department of Biomedical Engineering and Physics, Amsterdam UMC, University of Amsterdam, Amsterdam Movement Sciences, NL-1105 Amsterdam, The Netherlands
| | - Thomas Seifert
- Department of Mechanical and Process Engineering, University of Applied Sciences, DE-77652 Offenburg, Germany;
| | - Florian M. Thieringer
- Clinic of Oral and Cranio-Maxillofacial Surgery, University Hospital Basel, CH-4031 Basel, Switzerland; (N.S.); (H.-F.Z.)
- Medical Additive Manufacturing Research Group (Swiss MAM), Department of Biomedical Engineering, University of Basel, CH-4123 Allschwil, Switzerland; (D.W.); (M.M.); (P.H.)
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12
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Mensah S, Salako VK, Seifert T. Structural complexity and large‐sized trees explain shifting species richness and carbon relationship across vegetation types. Funct Ecol 2020. [DOI: 10.1111/1365-2435.13585] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sylvanus Mensah
- Laboratoire de Biomathématiques et d’Estimations Forestières Université d’Abomey Calavi Cotonou Benin
| | - Valère K. Salako
- Laboratoire de Biomathématiques et d’Estimations Forestières Université d’Abomey Calavi Cotonou Benin
- Service d’Évolution Biologique et Écologie Université Libre de Bruxelles Brussels Belgium
| | - Thomas Seifert
- Chair of Forest Growth Albert‐Ludwigs‐Universität Freiburg Freiburg im Breisgau Germany
- Department of Forest and Wood Science Stellenbosch University Stellenbosch South Africa
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13
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Heilat MQ, Seifert T. Mental motivation, intrinsic motivation and their relationship with emotional support sources among gifted and non-gifted Jordanian adolescents. Cogent Psychology 2019. [DOI: 10.1080/23311908.2019.1587131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Affiliation(s)
- M. Q. Heilat
- Department of Physiology and Special Education Al-Salt, Al-Balqa Applied University, Al-Salt, Jordan
| | - T. Seifert
- Faculty of Education, Memorial University, St. John’s, NL, Canada
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14
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Mensah S, du Toit B, Seifert T. Diversity–biomass relationship across forest layers: implications for niche complementarity and selection effects. Oecologia 2018; 187:783-795. [DOI: 10.1007/s00442-018-4144-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 04/11/2018] [Indexed: 11/29/2022]
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15
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Terry D, Cook N, Seifert T, Maxwell B, Zafonte R, Silverberg N, Berkner P, Iverson G. B-71Effect of Pre-Injury Migraine History on Return to School and Sports Following Sport-Related Concussion. Arch Clin Neuropsychol 2017. [DOI: 10.1093/arclin/acx076.156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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16
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Mensah S, Veldtman R, Seifert T. Potential supply of floral resources to managed honey bees in natural mistbelt forests. J Environ Manage 2017; 189:160-167. [PMID: 28038411 DOI: 10.1016/j.jenvman.2016.12.033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 12/11/2016] [Accepted: 12/12/2016] [Indexed: 06/06/2023]
Abstract
Honey bees play a vital role in the pollination of flowers in many agricultural systems, while providing honey through well managed beekeeping activities. Managed honey bees rely on the provision of pollen and nectar for their survival and productivity. Using data from field plot inventories in natural mistbelt forests, we (1) assessed the diversity and relative importance of honey bee plants, (2) explored the temporal availability of honey bee forage (nectar and pollen resources), and (3) elucidated how plant diversity (bee plant richness and overall plant richness) influenced the amount of forage available (production). A forage value index was defined on the basis of species-specific nectar and pollen values, and expected flowering period. Up to 50% of the overall woody plant richness were found to be honey bee plant species, with varying flowering period. As expected, bee plant richness increased with overall plant richness. Interestingly, bee plants' flowering period was spread widely over a year, although the highest potential of forage supply was observed during the last quarter. We also found that only few honey bee plant species contributed 90 percent of the available forage. Surprisingly, overall plant richness did not significantly influence the bee forage value. Rather, bee plant species richness showed significant and greater effect. The results of this study suggest that mistbelt forests can contribute to increase the spatial and temporal availability of diverse floral resources for managed honey bees. Conservation efforts must be specifically oriented towards honey bee plant species in mistbelt forests to preserve and enhance their potential to help maintain honey bee colonies. The implications for forest management, beekeeping activities and pollination-based agriculture were discussed.
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Affiliation(s)
- Sylvanus Mensah
- Department of Forest and Wood Science, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa; Laboratoire de Biomathématiques et d'Estimations Forestières, Université d'Abomey-Calavi, Cotonou 03 BP 2819, Bénin.
| | - Ruan Veldtman
- South African National Biodiversity Institute, Kirstenbosch Research Centre, Private Bag X7, 7735 Claremont, South Africa; Department of Conservation Ecology and Entomology, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa
| | - Thomas Seifert
- Department of Forest and Wood Science, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa
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17
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Bailey DM, Rasmussen P, Overgaard M, Evans KA, Bohm AM, Seifert T, Brassard P, Zaar M, Nielsen HB, Raven PB, Secher NH. Nitrite and
S
-Nitrosohemoglobin Exchange Across the Human Cerebral and Femoral Circulation. Circulation 2017; 135:166-176. [DOI: 10.1161/circulationaha.116.024226] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 11/02/2016] [Indexed: 12/22/2022]
Abstract
Background:
The mechanisms underlying red blood cell (RBC)–mediated hypoxic vasodilation remain controversial, with separate roles for nitrite (
) and
S
-nitrosohemoglobin (SNO-Hb) widely contested given their ability to transduce nitric oxide bioactivity within the microcirculation. To establish their relative contribution in vivo, we quantified arterial-venous concentration gradients across the human cerebral and femoral circulation at rest and during exercise, an ideal model system characterized by physiological extremes of O
2
tension and blood flow.
Methods:
Ten healthy participants (5 men, 5 women) aged 24±4 (mean±SD) years old were randomly assigned to a normoxic (21% O
2
) and hypoxic (10% O
2
) trial with measurements performed at rest and after 30 minutes of cycling at 70% of maximal power output in hypoxia and equivalent relative and absolute intensities in normoxia. Blood was sampled simultaneously from the brachial artery and internal jugular and femoral veins with plasma and RBC nitric oxide metabolites measured by tri-iodide reductive chemiluminescence. Blood flow was determined by transcranial Doppler ultrasound (cerebral blood flow) and constant infusion thermodilution (femoral blood flow) with net exchange calculated via the Fick principle.
Results:
Hypoxia was associated with a mild increase in both cerebral blood flow and femoral blood flow (
P
<0.05 versus normoxia) with further, more pronounced increases observed in femoral blood flow during exercise (
P
<0.05 versus rest) in proportion to the reduction in RBC oxygenation (
r
=0.680–0.769,
P
<0.001). Plasma
gradients reflecting consumption (arterial>venous;
P
<0.05) were accompanied by RBC iron nitrosylhemoglobin formation (venous>arterial;
P
<0.05) at rest in normoxia, during hypoxia (
P
<0.05 versus normoxia), and especially during exercise (
P
<0.05 versus rest), with the most pronounced gradients observed across the bioenergetically more active, hypoxemic, and acidotic femoral circulation (
P
<0.05 versus cerebral). In contrast, we failed to observe any gradients consistent with RBC SNO-Hb consumption and corresponding delivery of plasma
S
-nitrosothiols (
P
>0.05).
Conclusions:
These findings suggest that hypoxia and, to a far greater extent, exercise independently promote arterial-venous delivery gradients of intravascular nitric oxide, with deoxyhemoglobin-mediated
reduction identified as the dominant mechanism underlying hypoxic vasodilation.
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Affiliation(s)
- Damian M. Bailey
- From Faculty of Medicine, Reichwald Health Sciences Centre, University of British Columbia–Okanagan, Kelowna, BC, Canada (D.M.B.); Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK (K.A.E.); Department of Anesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (P.R., M.D., A.M.B., T.S., P.B., M.Z., H.B.N., N.H.S.); Université Laval, Québec, QC, Canada (P.B.); and Department of Integrative Physiology and Anatomy,
| | - Peter Rasmussen
- From Faculty of Medicine, Reichwald Health Sciences Centre, University of British Columbia–Okanagan, Kelowna, BC, Canada (D.M.B.); Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK (K.A.E.); Department of Anesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (P.R., M.D., A.M.B., T.S., P.B., M.Z., H.B.N., N.H.S.); Université Laval, Québec, QC, Canada (P.B.); and Department of Integrative Physiology and Anatomy,
| | - Morten Overgaard
- From Faculty of Medicine, Reichwald Health Sciences Centre, University of British Columbia–Okanagan, Kelowna, BC, Canada (D.M.B.); Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK (K.A.E.); Department of Anesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (P.R., M.D., A.M.B., T.S., P.B., M.Z., H.B.N., N.H.S.); Université Laval, Québec, QC, Canada (P.B.); and Department of Integrative Physiology and Anatomy,
| | - Kevin A. Evans
- From Faculty of Medicine, Reichwald Health Sciences Centre, University of British Columbia–Okanagan, Kelowna, BC, Canada (D.M.B.); Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK (K.A.E.); Department of Anesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (P.R., M.D., A.M.B., T.S., P.B., M.Z., H.B.N., N.H.S.); Université Laval, Québec, QC, Canada (P.B.); and Department of Integrative Physiology and Anatomy,
| | - Aske M. Bohm
- From Faculty of Medicine, Reichwald Health Sciences Centre, University of British Columbia–Okanagan, Kelowna, BC, Canada (D.M.B.); Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK (K.A.E.); Department of Anesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (P.R., M.D., A.M.B., T.S., P.B., M.Z., H.B.N., N.H.S.); Université Laval, Québec, QC, Canada (P.B.); and Department of Integrative Physiology and Anatomy,
| | - Thomas Seifert
- From Faculty of Medicine, Reichwald Health Sciences Centre, University of British Columbia–Okanagan, Kelowna, BC, Canada (D.M.B.); Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK (K.A.E.); Department of Anesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (P.R., M.D., A.M.B., T.S., P.B., M.Z., H.B.N., N.H.S.); Université Laval, Québec, QC, Canada (P.B.); and Department of Integrative Physiology and Anatomy,
| | - Patrice Brassard
- From Faculty of Medicine, Reichwald Health Sciences Centre, University of British Columbia–Okanagan, Kelowna, BC, Canada (D.M.B.); Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK (K.A.E.); Department of Anesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (P.R., M.D., A.M.B., T.S., P.B., M.Z., H.B.N., N.H.S.); Université Laval, Québec, QC, Canada (P.B.); and Department of Integrative Physiology and Anatomy,
| | - Morten Zaar
- From Faculty of Medicine, Reichwald Health Sciences Centre, University of British Columbia–Okanagan, Kelowna, BC, Canada (D.M.B.); Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK (K.A.E.); Department of Anesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (P.R., M.D., A.M.B., T.S., P.B., M.Z., H.B.N., N.H.S.); Université Laval, Québec, QC, Canada (P.B.); and Department of Integrative Physiology and Anatomy,
| | - Henning B. Nielsen
- From Faculty of Medicine, Reichwald Health Sciences Centre, University of British Columbia–Okanagan, Kelowna, BC, Canada (D.M.B.); Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK (K.A.E.); Department of Anesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (P.R., M.D., A.M.B., T.S., P.B., M.Z., H.B.N., N.H.S.); Université Laval, Québec, QC, Canada (P.B.); and Department of Integrative Physiology and Anatomy,
| | - Peter B. Raven
- From Faculty of Medicine, Reichwald Health Sciences Centre, University of British Columbia–Okanagan, Kelowna, BC, Canada (D.M.B.); Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK (K.A.E.); Department of Anesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (P.R., M.D., A.M.B., T.S., P.B., M.Z., H.B.N., N.H.S.); Université Laval, Québec, QC, Canada (P.B.); and Department of Integrative Physiology and Anatomy,
| | - Niels H. Secher
- From Faculty of Medicine, Reichwald Health Sciences Centre, University of British Columbia–Okanagan, Kelowna, BC, Canada (D.M.B.); Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK (K.A.E.); Department of Anesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark (P.R., M.D., A.M.B., T.S., P.B., M.Z., H.B.N., N.H.S.); Université Laval, Québec, QC, Canada (P.B.); and Department of Integrative Physiology and Anatomy,
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18
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Mensah S, Veldtman R, Assogbadjo AE, Glèlè Kakaï R, Seifert T. Tree species diversity promotes aboveground carbon storage through functional diversity and functional dominance. Ecol Evol 2016; 6:7546-7557. [PMID: 28725419 PMCID: PMC5513275 DOI: 10.1002/ece3.2525] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 09/01/2016] [Accepted: 09/04/2016] [Indexed: 11/06/2022] Open
Abstract
The relationship between biodiversity and ecosystem function has increasingly been debated as the cornerstone of the processes behind ecosystem services delivery. Experimental and natural field-based studies have come up with nonconsistent patterns of biodiversity-ecosystem function, supporting either niche complementarity or selection effects hypothesis. Here, we used aboveground carbon (AGC) storage as proxy for ecosystem function in a South African mistbelt forest, and analyzed its relationship with species diversity, through functional diversity and functional dominance. We hypothesized that (1) diversity influences AGC through functional diversity and functional dominance effects; and (2) effects of diversity on AGC would be greater for functional dominance than for functional diversity. Community weight mean (CWM) of functional traits (wood density, specific leaf area, and maximum plant height) were calculated to assess functional dominance (selection effects). As for functional diversity (complementarity effects), multitrait functional diversity indices were computed. The first hypothesis was tested using structural equation modeling. For the second hypothesis, effects of environmental variables such as slope and altitude were tested first, and separate linear mixed-effects models were fitted afterward for functional diversity, functional dominance, and both. Results showed that AGC varied significantly along the slope gradient, with lower values at steeper sites. Species diversity (richness) had positive relationship with AGC, even when slope effects were considered. As predicted, diversity effects on AGC were mediated through functional diversity and functional dominance, suggesting that both the niche complementarity and the selection effects are not exclusively affecting carbon storage. However, the effects were greater for functional diversity than for functional dominance. Furthermore, functional dominance effects were strongly transmitted by CWM of maximum plant height, reflecting the importance of forest vertical stratification for diversity-carbon relationship. We therefore argue for stronger complementary effects that would be induced also by complementary light-use efficiency of tree and species growing in the understory layer.
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Affiliation(s)
- Sylvanus Mensah
- Department of Forest and Wood ScienceStellenbosch UniversityMatielandSouth Africa
- Laboratoire de Biomathématiques et d'Estimations ForestièresUniversité d'Abomey‐CalaviCotonouBénin
| | - Ruan Veldtman
- South African National Biodiversity InstituteKirstenbosch Research CentreClaremontSouth Africa
- Department of Conservation Ecology and EntomologyStellenbosch UniversityMatielandSouth Africa
| | | | - Romain Glèlè Kakaï
- Laboratoire de Biomathématiques et d'Estimations ForestièresUniversité d'Abomey‐CalaviCotonouBénin
| | - Thomas Seifert
- Department of Forest and Wood ScienceStellenbosch UniversityMatielandSouth Africa
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19
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Magalhães TM, Seifert T. Tree component biomass expansion factors and root-to-shoot ratio of Lebombo ironwood: measurement uncertainty. Carbon Balance Manag 2015; 10:9. [PMID: 26316881 PMCID: PMC4544549 DOI: 10.1186/s13021-015-0019-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 03/27/2015] [Indexed: 06/02/2023]
Abstract
BACKGROUND National and regional aboveground biomass (AGB) estimates are generally computed based on standing stem volume estimates from forest inventories and default biomass expansion factors (BEFs). AGB estimates are converted to estimates of belowground biomass (BGB) using default root-to-shoot ratios (R/S). Thus, BEFs and R/S are not estimated in ordinary forest inventories, which results in uncertainty in estimates of AGB and BGB. Here, we measured BEF and R/S values (including uncertainty) for different components of Lebombo ironwood (Androstachys johnsonii Prain) trees and assessed their dependence on tree size. RESULTS The BEF values of tree components were unrelated or weakly related to tree size, and R/S was independent of tree size. BEF values varied from 0.02 for foliage to 1.31 Mg m-3 for whole tree; measurement uncertainty (SE) varied from 2.9% for stem BEF to 10.6% for whole-tree BEF. The belowground, aboveground, and whole-tree BEF-based biomass densities were 30 ± 2.3 (SE = 3.89%), 121 ± 7.84 (SE = 3.23%), and 151 ± 9.87 Mg ha-1(SE = 3.27%), respectively. R/S was 0.24 with an uncertainty of 3.4%. CONCLUSIONS Based on the finding of independence or weak dependence of BEF on tree size, we concluded that, for A. johnsonii, constant component BEF values can be accurately used within the interval of harvested tree sizes.
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Affiliation(s)
- Tarquinio Mateus Magalhães
- Departamento de Engenharia Florestal, Universidade Eduardo Mondlane, Campus Universitário Principal, Edifício no 1, Maputo, Mozambique
- Department of Forest and Wood Science, University of Stellenbosch, Private Bag X1 Matieland, 7602 Stellenbosch, South Africa
| | - Thomas Seifert
- Department of Forest and Wood Science, University of Stellenbosch, Private Bag X1 Matieland, 7602 Stellenbosch, South Africa
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20
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Iverson G, Silverberg N, Wojtowicz M, Gerrard P, Atkins J, Zafonte R, Berkner P, Seifert T. A-63Migraine History and Associated Comorbidities in High School Athletes: Implications for Sports Concussion Management Programs. Arch Clin Neuropsychol 2015. [DOI: 10.1093/arclin/acv047.63] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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21
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Kim YS, Seifert T, Brassard P, Rasmussen P, Vaag A, Nielsen HB, Secher NH, van Lieshout JJ. Impaired cerebral blood flow and oxygenation during exercise in type 2 diabetic patients. Physiol Rep 2015; 3:3/6/e12430. [PMID: 26109188 PMCID: PMC4510631 DOI: 10.14814/phy2.12430] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Endothelial vascular function and capacity to increase cardiac output during exercise are impaired in patients with type 2 diabetes (T2DM). We tested the hypothesis that the increase in cerebral blood flow (CBF) during exercise is also blunted and, therefore, that cerebral oxygenation becomes affected and perceived exertion increased in T2DM patients. We quantified cerebrovascular besides systemic hemodynamic responses to incremental ergometer cycling exercise in eight male T2DM and seven control subjects. CBF was assessed from the Fick equation and by transcranial Doppler-determined middle cerebral artery blood flow velocity. Cerebral oxygenation and metabolism were evaluated from the arterial-to-venous differences for oxygen, glucose, and lactate. Blood pressure was comparable during exercise between the two groups. However, the partial pressure of arterial carbon dioxide was lower at higher workloads in T2DM patients and their work capacity and increase in cardiac output were only ~80% of that established in the control subjects. CBF and cerebral oxygenation were reduced during exercise in T2DM patients (P < 0.05), and they expressed a higher rating of perceived exertion (P < 0.05). In contrast, CBF increased ~20% during exercise in the control group while the brain uptake of lactate and glucose was similar in the two groups. In conclusion, these results suggest that impaired CBF and oxygenation responses to exercise in T2DM patients may relate to limited ability to increase cardiac output and to reduced vasodilatory capacity and could contribute to their high perceived exertion.
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Affiliation(s)
- Yu-Sok Kim
- Department of Internal Medicine, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands Department of Anatomy, Embryology & Physiology, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands Laboratory for Clinical Cardiovascular Physiology, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands
| | - Thomas Seifert
- Department of Anesthesia, The Copenhagen Muscle Research Center University of Copenhagen, Copenhagen, Denmark
| | - Patrice Brassard
- Department of Anesthesia, The Copenhagen Muscle Research Center University of Copenhagen, Copenhagen, Denmark
| | - Peter Rasmussen
- Department of Anesthesia, The Copenhagen Muscle Research Center University of Copenhagen, Copenhagen, Denmark
| | - Allan Vaag
- Department of Endocrinology, Rigshospitalet University of Copenhagen, Copenhagen, Denmark
| | - Henning B Nielsen
- Department of Anesthesia, The Copenhagen Muscle Research Center University of Copenhagen, Copenhagen, Denmark
| | - Niels H Secher
- Department of Anesthesia, The Copenhagen Muscle Research Center University of Copenhagen, Copenhagen, Denmark
| | - Johannes J van Lieshout
- Department of Internal Medicine, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands Department of Anatomy, Embryology & Physiology, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands Laboratory for Clinical Cardiovascular Physiology, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, School of Life Sciences University of Nottingham Medical School Queen's Medical Centre, Nottingham, UK
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Avnstorp MB, Rasmussen P, Brassard P, Seifert T, Overgaard M, Krustrup P, Secher NH, Nordsborg NB. Cerebral water and ion balance remains stable when humans are exposed to acute hypoxic exercise. High Alt Med Biol 2015; 16:18-25. [PMID: 25761236 DOI: 10.1089/ham.2014.1075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Intense physical activity increases the prevalence of acute mountain sickness (AMS) that can occur within 10 h after ascent to altitudes above 1500 m and is likely related to development of cerebral edema. This study evaluated whether disturbed cerebral water and ion homeostasis can be detected when intense exercise is carried out in hypoxia and monitored the influence of muscle metabolism for changes in arterial variables. METHODS On two separate days, in random order, 30 min cycling exercise was performed in either hypoxia (10% O2) or normoxia at an intensity that was exhaustive in the hypoxic trial (∼120 W; n=9). RESULTS Exercise in hypoxia affected muscle metabolism, as evidenced by higher (p<0.05) leg lactate release at 7.5 min and a continuous decline in arterial pH (p<0.001) that was not observed in normoxia. Middle cerebral artery flow velocity increased (p<0.01) with exercise under both circumstances. No cerebral net exchange of Na(+) or K(+) was evident. Likewise, no significant net-exchange of water over the brain was demonstrated and the arterial and jugular venous hemoglobin concentrations were similar. CONCLUSION Challenging exercise in hypoxia for 30 min affected muscle metabolism and increased an index of cerebral blood flow, but cerebral net water and ion homeostasis remained stable. Thus, although AMS develops within hours and may be related to exercise-induced disturbance of cerebral ion and water balance, such changes are not detectable when subjects are exposed to acute 30 min maximal exercise in hypoxia.
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Affiliation(s)
- Magnus B Avnstorp
- 1 Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen , Copenhagen, Denmark
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23
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Mikkelsen KH, Seifert T, Secher NH, Grøndal T, van Hall G. Systemic, cerebral and skeletal muscle ketone body and energy metabolism during acute hyper-D-β-hydroxybutyratemia in post-absorptive healthy males. J Clin Endocrinol Metab 2015; 100:636-43. [PMID: 25415176 DOI: 10.1210/jc.2014-2608] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
CONTEXT Ketone bodies are substrates during fasting and when on a ketogenic diet not the least for the brain and implicated in the management of epileptic seizures and dementia. Moreover, D-β-hydroxybutyrate (HOB) is suggested to reduce blood glucose and fatty acid levels. OBJECTIVES The objectives of this study were to quantitate systemic, cerebral, and skeletal muscle HOB utilization and its effect on energy metabolism. DESIGN Single trial. SETTING Hospital. PARTICIPANT Healthy post-absorptive males (n = 6). INTERVENTIONS Subjects were studied under basal condition and three consecutive 1-hour periods with a 3-, 6-, and 12-fold increased HOB concentration via HOB infusion. MAIN OUTCOME MEASURES Systemic, cerebral, and skeletal muscle HOB kinetics, oxidation, glucose turnover, and lipolysis via arterial, jugular, and femoral venous differences in combination with stable isotopically labeled HOB, glucose, and glycerol, infusion. RESULTS An increase in HOB from the basal 160-450 μmol/L elicited 14 ± 2% reduction (P = .03) in glucose appearance and 37 ± 4% decrease (P = .03) in lipolytic rate while insulin and glucagon were unchanged. Endogenous HOB appearance was reduced in a dose-dependent manner with complete inhibition at the highest HOB concentration (1.7 mmol/L). Cerebral HOB uptake and subsequent oxidation was linearly related to the arterial HOB concentration. Resting skeletal muscle HOB uptake showed saturation kinetics. CONCLUSION A small increase in the HOB concentration decreases glucose production and lipolysis in post-absorptive healthy males. Moreover, cerebral HOB uptake and oxidation rates are linearly related to the arterial HOB concentration of importance for modifying brain energy utilization, potentially of relevance for patients with epileptic seizures and dementia.
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Affiliation(s)
- Kristian H Mikkelsen
- Clinical Metabolomics Core Facility (K.H.M., T.G., G.v.H.), Department of Anaesthesiology (T.S., N.H.S.), Rigshospitalet, and Department of Biomedical Sciences (G.v.H.), Faculty of Health and Medical Sciences, University of DK-2100 Copenhagen, Denmark
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24
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Olesen ND, van Lieshout JJ, Fisher JP, Seifert T, Nielsen HB, Secher NH. Case report: (Pre)syncopal symptoms associated with a negative internal jugular venous pressure. Front Physiol 2014; 5:317. [PMID: 25191276 PMCID: PMC4139713 DOI: 10.3389/fphys.2014.00317] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 08/03/2014] [Indexed: 11/13/2022] Open
Abstract
A siphon is suggested to support cerebral blood flow but appears not to be established because internal jugular venous (IJV) pressure is close to zero in upright humans. Thus, in eleven young healthy males, IJV pressure was 9 ± 1 mmHg (mean ± SE) when supine and fell to 3 ± 1 mmHg when seated, and middle cerebral artery mean blood velocity (MCA Vmean; P < 0.007) and the near-infrared spectroscopy-determined frontal lobe oxygenation (ScO2; P = 0.028) also decreased. Another subject, however, developed (pre)syncopal symptoms while seated and his IJV pressure decreased to −17 mmHg. Furthermore, his MCA Vmean decreased and yet within the time of observation ScO2 was not necessarily affected. These findings support the hypothesis that a negative IJV pressure that is a prerequisite for creation of a siphon provokes venous collapse inside the dura, and thereby limits rather than supports CBF.
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Affiliation(s)
- Niels D Olesen
- Department of Anesthesia, Rigshospitalet, University of Copenhagen Copenhagen, Denmark
| | - Johannes J van Lieshout
- Department of Internal Medicine, Academic Medical Centre, University of Amsterdam Amsterdam, Netherlands ; Laboratory for Clinical Cardiovascular Physiology, Centre for Heart Failure Research, Academic Medical Centre Amsterdam, Netherlands ; MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, School of Life Sciences, The Medical School, University of Nottingham, Queen's Medical Centre Nottingham, UK
| | - James P Fisher
- School of Sport, Exercise & Rehabilitation Sciences, College of Life and Environmental Sciences University of Birmingham, UK
| | - Thomas Seifert
- Department of Anesthesia, Rigshospitalet, University of Copenhagen Copenhagen, Denmark
| | - Henning B Nielsen
- Department of Anesthesia, Rigshospitalet, University of Copenhagen Copenhagen, Denmark
| | - Niels H Secher
- Department of Anesthesia, Rigshospitalet, University of Copenhagen Copenhagen, Denmark
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25
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Stoll C, Lorenz IP, Nöth H, Seifert T. Oxochlorierung von Übergangsmetall-Komplexen mit Thionylchlorid/Oxochlorination of Transition Metal Complexes with Thionyl Chloride. Zeitschrift für Naturforschung B 2014. [DOI: 10.1515/znb-1998-0204] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
The reaction of the transition metal complexes CpV(CO)4 and [CpMo(CO)3]2 with thionyl chloride affords the oxodichlorides CpM(O)Cl2 (M = V, Mo) by oxidative decarbonylation. The X-ray structure analysis of CpV (O)Cl2 shows the pseudo tetrahedral “piano-stool” configuration for the central vanadium atom.
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Affiliation(s)
- Carola Stoll
- Institut für Anorganische Chemie der Ludwig-Maximilians-Universität München, Meiserstr. 1, D-80333 München
| | - Ingo-Peter Lorenz
- Institut für Anorganische Chemie der Ludwig-Maximilians-Universität München, Meiserstr. 1, D-80333 München
| | - Heinrich Nöth
- Institut für Anorganische Chemie der Ludwig-Maximilians-Universität München, Meiserstr. 1, D-80333 München
| | - Thomas Seifert
- Institut für Anorganische Chemie der Ludwig-Maximilians-Universität München, Meiserstr. 1, D-80333 München
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Abstract
Substitution of the Cl atoms of CH2(AlCl2)2 by 2,2,6,6-tetramethylpiperidino or bis(trimethylsilyl)- amino groups leads to monomeric methylene bis(diaminoalanes). These show a wide Al-C-Al bond angle as determined by X-ray crystallography and asymmetrically bonded amino groups in the piperidino derivative.
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Affiliation(s)
- Klaus Knabel
- Department of Chemistry, University of Munich, Butenandtstr. 5Ð13, D-81377 München, Germany
| | - Heinrich Nöth
- Department of Chemistry, University of Munich, Butenandtstr. 5Ð13, D-81377 München, Germany
| | - Thomas Seifert
- Department of Chemistry, University of Munich, Butenandtstr. 5Ð13, D-81377 München, Germany
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27
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Wrackmeyer B, Weidinger J, Nöth H, Storch W, Seifert T, Vosteen M. Determination of Coupling Signs 1J(119Sn, 15N ) and 2J(119Sn, 117Sn) in Trimethylstannylamines. ACTA ACUST UNITED AC 2014. [DOI: 10.1515/znb-1998-1212] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The l5N-labelled trimethylstannylamines 1 - 3 [(Me3Sn)3N, (Me3Sn)2NPh, (Me3Sn)2NBCgHi4 (BCgHi4 = 9-borabicyclo[3.3.0]nonyn and the non-labelled 4, Me3Sn-N(BC8Hi4)2 , were prepared and studied by 1H, 1C, 15N and 119Sn NMR. The 15N ultrahigh resolution NMR spectra of 1 revealed otherwise unobserved parameters such as 2J(15N ,Sn ,13C ) and the isotope induced chemical shift 2Δ12/13C(15N). 119Sn NMR spectra of 1, recorded under similar conditions, also show new parameters such as 3J(119Sn,N,Sn,13C) which are not resolved in the non-labelled derivative. By using various types o f two-dimensional heteronuclear shift correlations, absolute coupling signs of 1J(119Sn,15N) (all < 0) in 1 - 3 were determined. By the same techniques it proved possible to confirm the negative sign o f :7(Sn,Sn) (-195.4 Hz) in 1. In contrast, the coupling constants 2J(Sn,Sn) for 2 (+71.7) and 3 (+62.0) possess a positive sign. This sign inversion, observed here for the first time for apparently similar compounds, demonstrates the enormous influence of substituents on the nature of the lone pair of electrons at the nitrogen atom. It also shows that these experiments for sign determinations of coupling constants are necessary in order to interpret these data correctly.
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Affiliation(s)
- Bernd Wrackmeyer
- Laboratorium für Anorganische Chemie, Universität Bayreuth, D-95440 Bayreuth
| | - Jürgen Weidinger
- Laboratorium für Anorganische Chemie, Universität Bayreuth, D-95440 Bayreuth
| | - Heinrich Nöth
- Institut für Anorganische Chemie der Universität München, Meiserstr. 1, D-80333 München
| | - Wolfgang Storch
- Institut für Anorganische Chemie der Universität München, Meiserstr. 1, D-80333 München
| | - Thomas Seifert
- Institut für Anorganische Chemie der Universität München, Meiserstr. 1, D-80333 München
| | - Martina Vosteen
- Institut für Anorganische Chemie der Universität München, Meiserstr. 1, D-80333 München
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Wiberg N, Lemer HW, Wagner S, Nöth H, Seifert T. Über das Octastannandiid R*6Sn8[Na(THF)2 ]2 und zur möglichen Existenz des Octastannans R*6Sn8 [1] / On an Octastannanediide R*6Sn8[Na(THF)2]2 and the Possible Existence of an Octastannane R*6Sn8 [1]. ACTA ACUST UNITED AC 2014. [DOI: 10.1515/znb-1999-0709] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The black, air and moisture sensitive octastannanediide R*
6Sn8[Na(THF)2]2 (4) (R* = SitBu3) is prepared by reaction of Sn[N(SiMe3)2]2 with R*Na in tBuOMe at -78°C. Red brown octastannane R*6Sn8 (5) is formed by thermolysis of the tristannacyclopropene R*4Sn3 in benzene at 100 °C. According to the result of the X-ray structural analysis, 4 contains a Sn8 cubane with six Sn atoms each connected with R* and two at the end of a space diagonal connected with Na(THF)2. A preliminary X-ray structure analysis shows 5 to adopt the same Sn8 cubane structure as 4 with two bare Sn atoms at the end of a space diagonal.
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Affiliation(s)
- Nils Wiberg
- Institut für Anorganische Chemie der Universität München, Butenandtstr. 5-13 (Haus D), D-81377 München
| | - Hans-Wolfram Lemer
- Institut für Anorganische Chemie der Universität München, Butenandtstr. 5-13 (Haus D), D-81377 München
| | - Susanne Wagner
- Institut für Anorganische Chemie der Universität München, Butenandtstr. 5-13 (Haus D), D-81377 München
| | - Heinrich Nöth
- Institut für Anorganische Chemie der Universität München, Butenandtstr. 5-13 (Haus D), D-81377 München
| | - Thomas Seifert
- Institut für Anorganische Chemie der Universität München, Butenandtstr. 5-13 (Haus D), D-81377 München
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Reichert S, Schlitt A, Beschow V, Lutze A, Lischewski S, Seifert T, Dudakliewa T, Gawe R, Werdan K, Hofmann B, Schaller HG, Schulz S. Use of floss/interdental brushes is associated with lower risk for new cardiovascular events among patients with coronary heart disease. J Periodontal Res 2014; 50:180-8. [DOI: 10.1111/jre.12191] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/26/2014] [Indexed: 12/19/2022]
Affiliation(s)
- S. Reichert
- Department of Operative Dentistry and Periodontology; Martin Luther University Halle-Wittenberg; Halle Germany
| | - A. Schlitt
- Department of Cardiology; Paracelsus-Harz-Clinic Bad Suderode; Quedlinburg Germany
| | - V. Beschow
- Department of Operative Dentistry and Periodontology; Martin Luther University Halle-Wittenberg; Halle Germany
| | - A. Lutze
- Department of Operative Dentistry and Periodontology; Martin Luther University Halle-Wittenberg; Halle Germany
- Department of Internal Medicine III; Heart Centre of the University Clinics Halle (Saale); Martin Luther University Halle-Wittenberg; Halle Germany
| | - S. Lischewski
- Department of Operative Dentistry and Periodontology; Martin Luther University Halle-Wittenberg; Halle Germany
| | - T. Seifert
- Department of Operative Dentistry and Periodontology; Martin Luther University Halle-Wittenberg; Halle Germany
- Department of Internal Medicine III; Heart Centre of the University Clinics Halle (Saale); Martin Luther University Halle-Wittenberg; Halle Germany
| | - T. Dudakliewa
- Department of Internal Medicine III; Heart Centre of the University Clinics Halle (Saale); Martin Luther University Halle-Wittenberg; Halle Germany
| | - R. Gawe
- Department of Internal Medicine III; Heart Centre of the University Clinics Halle (Saale); Martin Luther University Halle-Wittenberg; Halle Germany
| | - K. Werdan
- Department of Internal Medicine III; Heart Centre of the University Clinics Halle (Saale); Martin Luther University Halle-Wittenberg; Halle Germany
| | - B. Hofmann
- Department of Cardiothoracic Surgery; Heart Centre of the University Clinics Halle (Saale); Martin Luther University Halle-Wittenberg; Halle Germany
| | - H.-G. Schaller
- Department of Operative Dentistry and Periodontology; Martin Luther University Halle-Wittenberg; Halle Germany
| | - S. Schulz
- Department of Operative Dentistry and Periodontology; Martin Luther University Halle-Wittenberg; Halle Germany
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Rokamp KZ, Olesen ND, Larsson HBW, Hansen AE, Seifert T, Nielsen HB, Secher NH, Rostrup E. Glycopyrrolate does not influence the visual or motor-induced increase in regional cerebral perfusion. Front Physiol 2014; 5:45. [PMID: 24575051 PMCID: PMC3920105 DOI: 10.3389/fphys.2014.00045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Accepted: 01/24/2014] [Indexed: 02/06/2023] Open
Abstract
Acetylcholine may contribute to the increase in regional cerebral blood flow (rCBF) during cerebral activation since glycopyrrolate, a potent inhibitor of acetylcholine, abolishes the exercise-induced increase in middle cerebral artery mean flow velocity. We tested the hypothesis that cholinergic vasodilatation is important for the increase in rCBF during cerebral activation. The subjects were 11 young healthy males at an age of 24 ± 3 years (mean ± SD). We used arterial spin labeling and blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) to evaluate rCBF with and without intravenous glycopyrrolate during a handgrip motor task and visual stimulation. Glycopyrrolate increased heart rate from 56 ± 9 to 114 ± 14 beats/min (mean ± SD; p < 0.001), mean arterial pressure from 86 ± 8 to 92 ± 12 mmHg, and cardiac output from 5.6 ± 1.4 to 8.0 ± 1.7 l/min. Glycopyrrolate had, however, no effect on the arterial spin labeling or BOLD responses to the handgrip motor task or to visual stimulation. This study indicates that during a handgrip motor task and visual stimulation, the increase in rCBF is unaffected by blockade of acetylcholine receptors by glycopyrrolate. Further studies on the effect of glycopyrrolate on middle cerebral artery diameter are needed to evaluate the influence of glycopyrrolate on mean flow velocity during intense exercise.
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Affiliation(s)
- Kim Z Rokamp
- Department of Anaesthesia, Rigshospitalet Copenhagen, Denmark
| | - Niels D Olesen
- Department of Anaesthesia, Rigshospitalet Copenhagen, Denmark
| | - Henrik B W Larsson
- Functional Imaging Unit, Department of Diagnostics, Glostrup Hospital Glostrup, Denmark
| | - Adam E Hansen
- Functional Imaging Unit, Department of Diagnostics, Glostrup Hospital Glostrup, Denmark
| | - Thomas Seifert
- Department of Anaesthesia, Rigshospitalet Copenhagen, Denmark
| | | | - Niels H Secher
- Department of Anaesthesia, Rigshospitalet Copenhagen, Denmark
| | - Egill Rostrup
- Functional Imaging Unit, Department of Diagnostics, Glostrup Hospital Glostrup, Denmark
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Schlitt A, Lutze A, Wienke A, Seifert T, Dudaklieva T, Gawe R, Schulz S, Hofmann B, Schaller HG, Werdan K. High degree of severe periodontitis in patients with coronary heart disease from Eastern Germany, but no relation to cardiovascular outcome, the PARO-CHD study. Eur Heart J 2013. [DOI: 10.1093/eurheartj/eht308.p2484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Schlader ZJ, Seifert T, Wilson TE, Bundgaard-Nielsen M, Secher NH, Crandall CG. Acute volume expansion attenuates hyperthermia-induced reductions in cerebral perfusion during simulated hemorrhage. J Appl Physiol (1985) 2013; 114:1730-5. [PMID: 23580601 DOI: 10.1152/japplphysiol.00079.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hyperthermia reduces the capacity to withstand a simulated hemorrhagic challenge, but volume loading preserves this capacity. This study tested the hypotheses that acute volume expansion during hyperthermia increases cerebral perfusion and attenuates reductions in cerebral perfusion during a simulated hemorrhagic challenge induced by lower-body negative pressure (LBNP). Eight healthy young male subjects underwent a supine baseline period (pre-LBNP), followed by 15- and 30-mmHg LBNP while normothermic, hyperthermic (increased pulmonary artery blood temperature ~1.1°C), and following acute volume infusion while hyperthermic. Primary dependent variables were mean middle cerebral artery blood velocity (MCAvmean), serving as an index of cerebral perfusion; mean arterial pressure (MAP); and cardiac output (thermodilution). During baseline, hyperthermia reduced MCAvmean (P = 0.001) by 12 ± 9% relative to normothermia. Volume infusion while hyperthermic increased cardiac output by 2.8 ± 1.4 l/min (P < 0.001), but did not alter MCAvmean (P = 0.99) or MAP (P = 0.39) compared with hyperthermia alone. Relative to hyperthermia, at 30-mmHg LBNP acute volume infusion attenuated reductions (P < 0.001) in cardiac output (by 2.5 ± 0.9 l/min; P < 0.001), MAP (by 5 ± 6 mmHg; P = 0.004), and MCAvmean (by 12 ± 13%; P = 0.002). These data indicate that acute volume expansion does not reverse hyperthermia-induced reductions in cerebral perfusion pre-LBNP, but that it does attenuate reductions in cerebral perfusion during simulated hemorrhage in hyperthermic humans.
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Affiliation(s)
- Zachary J Schlader
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital of Dallas, Dallas, Texas 75231, USA
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33
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Fisher JP, Hartwich D, Seifert T, Olesen ND, McNulty CL, Nielsen HB, van Lieshout JJ, Secher NH. Cerebral perfusion, oxygenation and metabolism during exercise in young and elderly individuals. J Physiol 2012; 591:1859-70. [PMID: 23230234 DOI: 10.1113/jphysiol.2012.244905] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We evaluated cerebral perfusion, oxygenation and metabolism in 11 young (22 ± 1 years) and nine older (66 ± 2 years) individuals at rest and during cycling exercise at low (25% W(max)), moderate (50% Wmax), high (75% W(max)) and exhaustive (100% W(max)) workloads. Mean middle cerebral artery blood velocity (MCA V(mean)), mean arterial pressure (MAP), cardiac output (CO) and partial pressure of arterial carbon dioxide (P(aCO2)) were measured. Blood samples were obtained from the right internal jugular vein and brachial artery to determine concentration differences for oxygen (O2), glucose and lactate across the brain. The molar ratio between cerebral uptake of O2 versus carbohydrate (O2-carbohydrate index; O2/[glucose + 1/2 lactate]; OCI), the cerebral metabolic rate of O2 (CMRO2) and changes in mitochondrial O2 tension ( P(mitoO2)) were calculated. 100% W(max) was ~33% lower in the older group. Exercise increased MAP and CO in both groups (P < 0.05 vs. rest), but at each intensity MAP was higher and CO lower in the older group (P < 0.05). MCA V(mean), P(aCO2) and cerebral vascular conductance index (MCA V(mean)/MAP) were lower in the older group at each exercise intensity (P < 0.05). In contrast, young and older individuals exhibited similar increases in CMRO2 (by ~30 μmol (100 g(-1)) min(-1)), and decreases in OCI (by ~1.5) and (by ~10 mmHg) during exercise at 75% W(max). Thus, despite the older group having reduced cerebral perfusion and maximal exercise capacity, cerebral oxygenation and uptake of lactate and glucose are similar during exercise in young and older individuals.
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Affiliation(s)
- James P Fisher
- School of Sport and Exercise Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
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Pearson J, Ganio MS, Seifert T, Overgaard M, Secher NH, Crandall CG. Pulmonary artery and intestinal temperatures during heat stress and cooling. Med Sci Sports Exerc 2012; 44:857-62. [PMID: 22015711 DOI: 10.1249/mss.0b013e31823d7a2b] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE In humans, whole body heating and cooling are used to address physiological questions where core temperature is central to the investigated hypotheses. Core temperature can be measured in various locations throughout the human body. The measurement of intestinal temperature is increasingly used in laboratory settings as well as in athletics. However, it is unknown whether intestinal temperature accurately tracks pulmonary artery blood temperature, the gold standard, during thermal stimuli in resting humans, which is the investigated hypothesis. METHODS This study compared pulmonary artery blood temperature (via thermistor in a pulmonary artery catheter) with intestinal temperature (telemetry pill) during whole body heat stress (n = 8), followed by whole body cooling in healthy humans (mean ± SD; age = 24 ± 3 yr, height = 183 ± 8 cm, mass = 78.1 ± 8.2 kg). Heat stress and subsequent cooling were performed by perfusing warm followed by cold water through a tube-lined suit worn by each subject. RESULTS Before heat stress, blood temperature (36.69°C ± 0.25°C) was less than intestinal temperature (36.96°C ± 0.21°C, P = 0.004). The increase in blood temperature after 20 min of heat stress was greater than the intestinal temperature (0.70 ± 0.24 vs 0.47 ± 0.18, P = 0.001). However, the increase in temperatures at the end of heat stress was similar between sites (blood Δ = 1.32°C ± 0.20°C vs intestinal Δ = 1.21°C ± 0.36°C, P = 0.30). Subsequent cooling decreased blood temperature (Δ = -1.03°C ± 0.34°C) to a greater extent than intestinal temperature (Δ = -0.41°C ± 0.30°C, P = 0.04). CONCLUSIONS In response to the applied thermal provocations, early temperature changes in the intestine are less than the temperature changes in pulmonary artery blood.
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Affiliation(s)
- James Pearson
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital of Dallas, Dallas, TX, USA
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35
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Sato K, Fisher JP, Seifert T, Overgaard M, Secher NH, Ogoh S. Blood flow in internal carotid and vertebral arteries during orthostatic stress. Exp Physiol 2012; 97:1272-80. [DOI: 10.1113/expphysiol.2012.064774] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Overgaard M, Rasmussen P, Bohm AM, Seifert T, Brassard P, Zaar M, Homann P, Evans KA, Nielsen HB, Secher NH. Hypoxia and exercise provoke both lactate release and lactate oxidation by the human brain. FASEB J 2012; 26:3012-20. [PMID: 22441982 DOI: 10.1096/fj.11-191999] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Lactate is shuttled between organs, as demonstrated in the Cori cycle. Although the brain releases lactate at rest, during physical exercise there is a cerebral uptake of lactate. Here, we evaluated the cerebral lactate uptake and release in hypoxia, during exercise and when the two interventions were combined. We measured cerebral lactate turnover via a tracer dilution method ([1-(13)C]lactate), using arterial to right internal jugular venous differences in 9 healthy individuals (5 males and 4 females), at rest and during 30 min of submaximal exercise in normoxia and hypoxia (F(i)o(2) 10%, arterial oxygen saturation 72 ± 10%, mean ± sd). Whole-body lactate turnover increased 3.5-fold and 9-fold at two workloads in normoxia and 18-fold during exercise in hypoxia. Although middle cerebral artery mean flow velocity increased during exercise in hypoxia, calculated cerebral mitochondrial oxygen tension decreased by 13 mmHg (P<0.001). At the same time, cerebral lactate release increased from 0.15 ± 0.1 to 0.8 ± 0.6 mmol min(-1) (P<0.05), corresponding to ∼10% of cerebral energy consumption. Concurrently, cerebral lactate uptake was 1.0 ± 0.9 mmol min(-1) (P<0.05), of which 57 ± 9% was oxidized, demonstrating that lactate oxidation may account for up to ∼33% of the energy substrate used by the brain. These results support the existence of a cell-cell lactate shuttle that may involve neurons and astrocytes.
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Affiliation(s)
- Morten Overgaard
- Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
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Ganio MS, Overgaard M, Seifert T, Secher NH, Johansson PI, Meyer MAS, Crandall CG. Effect of heat stress on cardiac output and systemic vascular conductance during simulated hemorrhage to presyncope in young men. Am J Physiol Heart Circ Physiol 2012; 302:H1756-61. [PMID: 22367508 DOI: 10.1152/ajpheart.00941.2011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During moderate actual or simulated hemorrhage, as cardiac output decreases, reductions in systemic vascular conductance (SVC) maintain mean arterial pressure (MAP). Heat stress, however, compromises the control of MAP during simulated hemorrhage, and it remains unknown whether this response is due to a persistently high SVC and/or a low cardiac output. This study tested the hypothesis that an inadequate decrease in SVC is the primary contributing mechanism by which heat stress compromises blood pressure control during simulated hemorrhage. Simulated hemorrhage was imposed via lower body negative pressure (LBNP) to presyncope in 11 passively heat-stressed subjects (increase core temperature: 1.2 ± 0.2°C; means ± SD). Cardiac output was measured via thermodilution, and SVC was calculated while subjects were normothermic, heat stressed, and throughout subsequent LBNP. MAP was not changed by heat stress but was reduced to 45 ± 12 mmHg at the termination of LBNP. Heat stress increased cardiac output from 7.1 ± 1.1 to 11.7 ± 2.2 l/min (P < 0.001) and increased SVC from 0.094 ± 0.018 to 0.163 ± 0.032 l·min(-1)·mmHg(-1) (P < 0.001). Although cardiac output at the onset of syncopal symptoms was 37 ± 16% lower relative to pre-LBNP, presyncope cardiac output (7.3 ± 2.0 l/min) was not different than normothermic values (P = 0.46). SVC did not change throughout LBNP (P > 0.05) and at presyncope was 0.168 ± 0.044 l·min(-1)·mmHg(-1). These data indicate that in humans a cardiac output adequate to maintain MAP while normothermic is no longer adequate during a heat-stressed-simulated hemorrhage. The absence of a decrease in SVC at a time of profound reductions in MAP suggests that inadequate control of vascular conductance is a primary mechanism compromising blood pressure control during these conditions.
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Affiliation(s)
- Matthew S Ganio
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Teaxs 75231, USA
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Crandall CG, Wilson TE, Marving J, Bundgaard-Nielsen M, Seifert T, Klausen TL, Andersen F, Secher NH, Hesse B. Colloid volume loading does not mitigate decreases in central blood volume during simulated haemorrhage while heat stressed. J Physiol 2012; 590:1287-97. [PMID: 22219334 DOI: 10.1113/jphysiol.2011.223602] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Heat stress results in profound reductions in the capacity to withstand a simulated haemorrhagic challenge; however, this capacity is normalized if the individual is volume loaded prior to the challenge. The present study tested the hypothesis that volume loading during passive heat stress attenuates the reduction in regional blood volumes during a simulated haemorrhagic challenge imposed via lower-body negative pressure (LBNP). Seven subjects underwent 30 mmHg LBNP while normothermic, during passive heat stress (increased internal temperature ∼1◦C), and while continuing to be heated after intravenous colloid volume loading (11 ml kg⁻¹). Relative changes in torso and regional blood volumes were determined by gamma camera imaging with technetium-99m labelled erythrocytes. Heat stress reduced blood volume in all regions (ranging from 7 to 16%), while subsequent volume loading returned those values to normothermic levels. While normothermic,LBNP reduced blood volume in all regions (torso: 22 ± 8%; heart: 18 ± 6%; spleen: 15 ± 8%). During LBNP while heat stressed, the reductions in blood volume in each region were markedly greater when compared to LBNP while normothermic (torso: 73 ± 2%; heart: 72 ± 3%; spleen: 72 ± 5%, all P<0.001 relative to normothermia). Volume loading during heat stress did not alter the extent of the reduction in these blood volumes to LBNP relative to heat stress alone (torso: 73 ± 1%; heart: 72 ± 2%; spleen: 74 ± 3%, all P>0.05 relative to heat stress alone). These data suggest that blood volume loading during passive heat stress (via 11 ml kg⁻¹ of a colloid solution) normalizes regional blood volumes in the torso, but does not mitigate the reduction in central blood volume during a simulated haemorrhagic challenge combined with heat stress.
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Affiliation(s)
- C G Crandall
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, 7232 Greenville Ave, Dallas, TX 75231, USA.
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Priesack E, Gayler S, Rötzer T, Seifert T, Pretzsch H. Mechanistic Modelling of Soil–Plant–Atmosphere Systems. Growth and Defence in Plants 2012. [DOI: 10.1007/978-3-642-30645-7_15] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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Seifert T, Secher NH. Sympathetic influence on cerebral blood flow and metabolism during exercise in humans. Prog Neurobiol 2011; 95:406-26. [PMID: 21963551 DOI: 10.1016/j.pneurobio.2011.09.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 09/13/2011] [Accepted: 09/19/2011] [Indexed: 11/26/2022]
Abstract
This review focuses on the possibility that autonomic activity influences cerebral blood flow (CBF) and metabolism during exercise in humans. Apart from cerebral autoregulation, the arterial carbon dioxide tension, and neuronal activation, it may be that the autonomic nervous system influences CBF as evidenced by pharmacological manipulation of adrenergic and cholinergic receptors. Cholinergic blockade by glycopyrrolate blocks the exercise-induced increase in the transcranial Doppler determined mean flow velocity (MCA Vmean). Conversely, alpha-adrenergic activation increases that expression of cerebral perfusion and reduces the near-infrared determined cerebral oxygenation at rest, but not during exercise associated with an increased cerebral metabolic rate for oxygen (CMRO(2)), suggesting competition between CMRO(2) and sympathetic control of CBF. CMRO(2) does not change during even intense handgrip, but increases during cycling exercise. The increase in CMRO(2) is unaffected by beta-adrenergic blockade even though CBF is reduced suggesting that cerebral oxygenation becomes critical and a limited cerebral mitochondrial oxygen tension may induce fatigue. Also, sympathetic activity may drive cerebral non-oxidative carbohydrate uptake during exercise. Adrenaline appears to accelerate cerebral glycolysis through a beta2-adrenergic receptor mechanism since noradrenaline is without such an effect. In addition, the exercise-induced cerebral non-oxidative carbohydrate uptake is blocked by combined beta 1/2-adrenergic blockade, but not by beta1-adrenergic blockade. Furthermore, endurance training appears to lower the cerebral non-oxidative carbohydrate uptake and preserve cerebral oxygenation during submaximal exercise. This is possibly related to an attenuated catecholamine response. Finally, exercise promotes brain health as evidenced by increased release of brain-derived neurotrophic factor (BDNF) from the brain.
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Affiliation(s)
- Thomas Seifert
- Department of Anaesthesia and The Copenhagen Muscle Research Centre, Rigshospitalet 2041, University of Copenhagen, Blegdamsvej 9, DK-2100 Copenhagen Ø, Denmark.
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Ogoh S, Sato K, Fisher JP, Seifert T, Overgaard M, Secher NH. The effect of phenylephrine on arterial and venous cerebral blood flow in healthy subjects. Clin Physiol Funct Imaging 2011; 31:445-51. [DOI: 10.1111/j.1475-097x.2011.01040.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Wilson TE, Hesse B, Marving J, Bundgaard‐Nielsen M, Seifert T, Secher NH, Crandall CG. Colloid volume loading does not mitigate thorax, heart, and liver blood volume changes during combined heat and orthostatic stress. FASEB J 2011. [DOI: 10.1096/fasebj.25.1_supplement.1053.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Pearson J, Ganio MS, Seifert T, Overgaard M, Secher NH, Crandall CG. Comparison of Pulmonary Artery Blood and Intestinal Temperatures in Humans. FASEB J 2011. [DOI: 10.1096/fasebj.25.1_supplement.1053.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- James Pearson
- Department of Internal MedicineUniversity of Texas Southwestern Medical CenterDallasTX
- Presbytarian Hospital DallasInstitute for Exercise and Environmental MedicineDallasTX
| | - Matthew S Ganio
- Department of Internal MedicineUniversity of Texas Southwestern Medical CenterDallasTX
- Presbytarian Hospital DallasInstitute for Exercise and Environmental MedicineDallasTX
| | - Thomas Seifert
- Department of AnesthesiaRigshospitaletUniversity of CopenhagenCopenhagenDenmark
| | - Morten Overgaard
- Department of AnesthesiaRigshospitaletUniversity of CopenhagenCopenhagenDenmark
| | - Niels H Secher
- Department of AnesthesiaRigshospitaletUniversity of CopenhagenCopenhagenDenmark
| | - Craig G Crandall
- Department of Internal MedicineUniversity of Texas Southwestern Medical CenterDallasTX
- Presbytarian Hospital DallasInstitute for Exercise and Environmental MedicineDallasTX
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Ganio MS, Overgaard M, Seifert T, Secher NH, Crandall CG. Cardiac output at pre‐syncope in the heat‐stressed human. FASEB J 2011. [DOI: 10.1096/fasebj.25.1_supplement.1053.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Matthew S Ganio
- UT Southwestern Med CtrDallasTX
- Institute for Exercise and Environmental MedicineTexas Health Presbyterian HospitalDallasTX
| | - Morten Overgaard
- Department of AnesthesiaUniversity of CopenhagenCopenhagenDenmark
| | - Thomas Seifert
- Department of AnesthesiaUniversity of CopenhagenCopenhagenDenmark
| | - Niels H. Secher
- Department of AnesthesiaUniversity of CopenhagenCopenhagenDenmark
| | - Craig G Crandall
- UT Southwestern Med CtrDallasTX
- Institute for Exercise and Environmental MedicineTexas Health Presbyterian HospitalDallasTX
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Josefsen K, Nielsen SM, Campos A, Seifert T, Hasholt L, Nielsen JE, Nørremølle A, Skotte NH, Secher NH, Quistorff B. Reduced gluconeogenesis and lactate clearance in Huntington's disease. Neurobiol Dis 2010; 40:656-62. [DOI: 10.1016/j.nbd.2010.08.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Revised: 07/23/2010] [Accepted: 08/11/2010] [Indexed: 12/26/2022] Open
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Volianitis S, Rasmussen P, Seifert T, Nielsen HB, Secher NH. Plasma pH does not influence the cerebral metabolic ratio during maximal whole body exercise. J Physiol 2010; 589:423-9. [PMID: 21098003 DOI: 10.1113/jphysiol.2010.195636] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Exercise lowers the cerebral metabolic ratio of O2 to carbohydrate (glucose+1/2 lactate) and metabolic acidosis appears to promote cerebral lactate uptake. However, the influence of pH on cerebral lactate uptake and, in turn, on the cerebral metabolic ratio during exercise is not known. Sodium bicarbonate (Bicarb, 1 M; 350-500 ml) or an equal volume of normal saline (Sal) was infused intravenously at a constant rate during a '2000 m' maximal ergometer row in six male oarsmen (23±2 years; mean±S.D.). During the Sal trial, pH decreased from 7.41±0.01 at rest to 7.02±0.02 but only to 7.36±0.02 (P <0.05) during the Bicarb trial. Arterial lactate increased to 21.4±0.8 and 32.7±2.3 mM during the Sal and Bicarb trials, respectively (P <0.05). Also, the arterial-jugular venous lactate difference increased from-0.03±0.01 mM at rest to 3.2±0.9 mM (P <0.05) and 3.4±1.4 mM (P <0.05) following the Sal and Bicarb trials, respectively. Accordingly, the cerebral metabolic ratio decreased equally during the Sal and Bicarb trials: from 5.8±0.6 at rest to 1.7±0.1 and 1.8±0.2, respectively. The enlarged blood-buffering capacity after infusion of Bicarb eliminated metabolic acidosis during maximal exercise but that did not affect the cerebral lactate uptake and, therefore, the decrease in the cerebral metabolic ratio.
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Affiliation(s)
- S Volianitis
- Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
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Shibasaki M, Wilson TE, Bundgaard-Nielsen M, Seifert T, Secher NH, Crandall CG. Modelflow underestimates cardiac output in heat-stressed individuals. Am J Physiol Regul Integr Comp Physiol 2010; 300:R486-91. [PMID: 21084673 DOI: 10.1152/ajpregu.00505.2010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An estimation of cardiac output can be obtained from arterial pressure waveforms using the Modelflow method. However, whether the assumptions associated with Modelflow calculations are accurate during whole body heating is unknown. This project tested the hypothesis that cardiac output obtained via Modelflow accurately tracks thermodilution-derived cardiac outputs during whole body heat stress. Acute changes of cardiac output were accomplished via lower-body negative pressure (LBNP) during normothermic and heat-stressed conditions. In nine healthy normotensive subjects, arterial pressure was measured via brachial artery cannulation and the volume-clamp method of the Finometer. Cardiac output was estimated from both pressure waveforms using the Modeflow method. In normothermic conditions, cardiac outputs estimated via Modelflow (arterial cannulation: 6.1 ± 1.0 l/min; Finometer 6.3 ± 1.3 l/min) were similar with cardiac outputs measured by thermodilution (6.4 ± 0.8 l/min). The subsequent reduction in cardiac output during LBNP was also similar among these methods. Whole body heat stress elevated internal temperature from 36.6 ± 0.3 to 37.8 ± 0.4°C and increased cardiac output from 6.4 ± 0.8 to 10.9 ± 2.0 l/min when evaluated with thermodilution (P < 0.001). However, the increase in cardiac output estimated from the Modelflow method for both arterial cannulation (2.3 ± 1.1 l/min) and Finometer (1.5 ± 1.2 l/min) was attenuated compared with thermodilution (4.5 ± 1.4 l/min, both P < 0.01). Finally, the reduction in cardiac output during LBNP while heat stressed was significantly attenuated for both Modelflow methods (cannulation: -1.8 ± 1.2 l/min, Finometer: -1.5 ± 0.9 l/min) compared with thermodilution (-3.8 ± 1.19 l/min). These results demonstrate that the Modelflow method, regardless of Finometer or direct arterial waveforms, underestimates cardiac output during heat stress and during subsequent reductions in cardiac output via LBNP.
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Affiliation(s)
- Manabu Shibasaki
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Ave., Dallas, TX 75231, USA
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Seifert T, Fisher JP, Young CN, Hartwich D, Ogoh S, Raven PB, Fadel PJ, Secher NH. Experimental Physiology -Research Paper: Glycopyrrolate abolishes the exercise-induced increase in cerebral perfusion in humans. Exp Physiol 2010; 95:1016-25. [DOI: 10.1113/expphysiol.2010.054346] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Fisher JP, Seifert T, Hartwich D, Young CN, Secher NH, Fadel PJ. Reply from James P. Fisher, Thomas Seifert, Doreen Hartwich, Colin N. Young, Niels H. Secher and Paul J. Fadel. J Physiol 2010. [DOI: 10.1113/jphysiol.2010.193573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Bundgaard-Nielsen M, Wilson TE, Seifert T, Secher NH, Crandall CG. Effect of volume loading on the Frank-Starling relation during reductions in central blood volume in heat-stressed humans. J Physiol 2010; 588:3333-9. [PMID: 20603336 DOI: 10.1113/jphysiol.2010.191981] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
During reductions in central blood volume while heat stressed, a greater decrease in stroke volume (SV) for a similar decrease in ventricular filling pressure, compared to normothermia, suggests that the heart is operating on a steeper portion of a Frank-Starling curve. If so, volume loading of heat-stressed individuals would shift the operating point to a flatter portion of the heat stress Frank-Starling curve thereby attenuating the reduction in SV during subsequent decreases in central blood volume. To investigate this hypothesis, right heart catheterization was performed in eight males from whom pulmonary capillary wedge pressure (PCWP), central venous pressure and SV (via thermodilution) were obtained while central blood volume was reduced via lower-body negative pressure (LBNP) during normothermia, whole-body heating (increase in blood temperature 1 degrees C), and during whole-body heating after intravascular volume expansion. Volume expansion was accomplished by administration of a combination of a synthetic colloid (HES 130/0.4, Voluven) and saline. Before LBNP, SV was not affected by heating (122 +/- 30 ml; mean +/- s.d.) compared to normothermia (110 +/- 20 ml; P = 0.06). However, subsequent volume loading increased SV to 143 +/- 29 ml (P = 0.003). LBNP provoked a larger decrease in SV relative to the decrease in PCWP during heating (8.6 +/- 1.9 ml mmHg(1)) compared to normothermia (4.5 +/- 3.0 ml mmHg(1), P = 0.02). After volume loading while heat stressed, the reduction in the SV to PCWP ratio during LBNP was comparable to that observed during normothermia (4.8 +/- 2.3 ml mmHg(1); P = 0.78). These data support the hypothesis that a Frank-Starling mechanism contributes to compromised blood pressure control during simulated haemorrhage in heat-stressed individuals, and extend those findings by showing that volume infusion corrects this deficit by shifting the operating point to a flatter portion of the heat stress Frank-Starling curve.
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Affiliation(s)
- M Bundgaard-Nielsen
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Ave, Dallas, TX 75231, USA
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