| 1. |
- Aad, G, et al.
(författare)
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- 2015
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swepub:Mat__t
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| 5. |
- Moesgaard, S G, et al.
(författare)
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Sensory nerve inactivation by resiniferatoxin improves insulin sensitivity in male obese Zucker rats
- 2005
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Ingår i: American Journal of Physiology: Endocrinology and Metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 288:6, s. 1137-1145
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies have suggested that sensory nerves may influence insulin secretion and action. The present study investigated the effects of resiniferatoxin (RTX) inactivation of sensory nerves ( desensitization) on oral glucose tolerance, insulin secretion and whole body insulin sensitivity in the glucose intolerant, hyperinsulinemic, and insulin-resistant obese Zucker rat. After RTX treatment (0.05 mg/kg RTX sc given at ages 8, 10, and 12 wk), fasting plasma insulin was reduced ( P < 0.0005), and oral glucose tolerance was improved ( P < 0.005). Pancreas perfusion showed that baseline insulin secretion ( 7 mM glucose) was lower in RTX-treated rats ( P = 0.01). Insulin secretory responsiveness to 20 mM glucose was enhanced in the perfused pancreas of RTX-treated rats ( P < 0.005) but unaffected in stimulated, isolated pancreatic islets. At the peak of spontaneous insulin resistance in the obese Zucker rat, insulin sensitivity was substantially improved after RTX treatment, as evidenced by higher glucose infusion rates (GIR) required to maintain euglycemia during a hyperinsulinemic euglycemic ( 5 mU center dot kg(-1) center dot min(-1)) clamp (GIR(60 - 120min): 5.97 +/- 0.62 vs. 11.65 +/- 0.83 mg center dot kg(-1) center dot min(-1) in RTX-treated rats, P = 0.003). In conclusion, RTX treatment and, hence, sensory nerve desensitization of adult male obese Zucker rats improved oral glucose tolerance by enhancing insulin secretion, and, in particular, by improving insulin sensitivity.
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| 6. |
- Mitra, Aditee, et al.
(författare)
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Defining Planktonic Protist Functional Groups on Mechanisms for Energy and Nutrient Acquisition : Incorporation of Diverse Mixotrophic Strategies
- 2016
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Ingår i: Protist. - : Elsevier BV. - 1434-4610 .- 1618-0941. ; 167:2, s. 106-120
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Tidskriftsartikel (refereegranskat)abstract
- Arranging organisms into functional groups aids ecological research by grouping organisms (irrespective of phylogenetic origin) that interact with environmental factors in similar ways. Planktonic protists traditionally have been split between photoautotrophic "phytoplankton" and phagotrophic "microzooplankton". However, there is a growing recognition of the importance of mixotrophy in euphotic aquatic systems, where many protists often combine photoautotrophic and phagotrophic modes of nutrition. Such organisms do not align with the traditional dichotomy of phytoplankton and microzooplankton. To reflect this understanding, we propose a new functional grouping of planktonic protists in an ecophysiological context: (i) phagoheterotrophs lacking phototrophic capacity, (ii) photoautotrophs lacking phagotrophic capacity, (iii) constitutive mixotrophs (CMs) as phagotrophs with an inherent capacity for phototrophy, and (iv) non-constitutive mixotrophs (NCMs) that acquire their phototrophic capacity by ingesting specific (SNCM) or general non-specific (GNCM) prey. For the first time, we incorporate these functional groups within a foodweb structure and show, using model outputs, that there is scope for significant changes in trophic dynamics depending on the protist functional type description. Accordingly, to better reflect the role of mixotrophy, we recommend that as important tools for explanatory and predictive research, aquatic food-web and biogeochemical models need to redefine the protist groups within their frameworks. (C) 2016 The Authors. Published by Elsevier GmbH.
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| 7. |
- Schön, Max Emil, et al.
(författare)
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Single cell genomics reveals plastid-lacking Picozoa are close relatives of red algae
- 2021
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The endosymbiotic origin of plastids from cyanobacteria gave eukaryotes photosynthetic capabilities and launched the diversification of countless forms of algae. These primary plastids are found in members of the eukaryotic supergroup Archaeplastida. All known archaeplastids still retain some form of primary plastids, which are widely assumed to have a single origin. Here, we used single-cell genomics from natural samples combined with phylogenomics to infer the evolutionary origin of the phylum Picozoa, a globally distributed but seemingly rare group of marine microbial heterotrophic eukaryotes. Strikingly, the analysis of 43 single-cell genomes shows that Picozoa belong to Archaeplastida, specifically related to red algae and the phagotrophic rhodelphids. These picozoan genomes support the hypothesis that Picozoa lack a plastid, and further reveal no evidence of an early cryptic endosymbiosis with cyanobacteria. These findings change our understanding of plastid evolution as they either represent the first complete plastid loss in a free-living taxon, or indicate that red algae and rhodelphids obtained their plastids independently of other archaeplastids.
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| 8. |
- Berg, F., et al.
(författare)
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AFM-Based Quantification of Conformational Changes in DNA Caused by Reactive Oxygen Species
- 2015
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 119:1, s. 25-32
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Tidskriftsartikel (refereegranskat)abstract
- Radical induced modification of DNA plays an important role in many pathological pathways like cancer development, aging, etc. In this work, we quantify radical-induced DNA damage that causes transitions from double to single stranded DNA using atomic force microscopy (AFM). The plasmid pBR322 is attacked by free hydroxyl radicals that are produced by Fenton's reaction; the strength of the radical attack is controlled via the ratio of hydroxyl radical molecules to DNA base pairs. The extent of DNA modification is assessed by AFM tapping mode (TM) imaging of the plasmids (after adsorption onto PAH-functionalized mica) in air. As single stranded DNA chains (height similar to 2 angstrom) are much smaller than intact DNA strands (similar to 5 angstrom), their fraction can be quantified based on the height distribution, which allows a simplified data analysis in comparison to similar AFM-based approaches. It is found that the amount of damaged DNA strands increases with increasing strength of radical attack, and decreases if ROS scavengers like sodium acetate are added. Competition curves are calculated for the interaction of hydroxyl radicals with DNA and sodium acetate, which finally allows calculation of relative rate constants for the respective reactions.
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| 9. |
- Li, J. H., et al.
(författare)
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Characterization of Active Species in Cu-Beta Zeolite by Temperature-Programmed Reduction Mass Spectrometry (TPR-MS)
- 2013
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 56:1-8, s. 201-204
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Tidskriftsartikel (refereegranskat)abstract
- The number and type of copper species present in an under-exchanged Cu-Beta zeolite catalyst were characterized using temperature-programmed reduction mass spectrometry (TPR-MS). Both H-2 consumption and H2O evolution were tracked, yielding additional insights into the nature of Cu species. Prior to the TPR-MS tests, catalyst samples were subjected to various high- temperature aging treatments in the presence of O-2 in He, in order to assist with interrogating and resolving different types of sites. Absence of reducible species in the precursor material was confirmed by subjecting the H-form of the same zeolite to the TPR. Upon aging at temperatures below 700 A degrees C, the TPR pattern showed several distinct peaks of different intensities. Aging at 800 A degrees C led to shifting and broadening of these H-2 consumption peaks, as well as to some reduction of the integral amount of the reducible sites. The 900 A degrees C exposure resulted in a drastic change of the TPR pattern, with several new well-resolved H-2 consumption peaks, indicative of drastic changes in the catalyst structure. The integral amount of H-2 consumed quantitatively matched the amount of Cu species present in the catalyst, assuming the stoichiometry. The combination of experimental findings in this work lends support to a hypothesis that different TPR peaks are indicative of different types of sites rather than of step-wise reduction of copper species.
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| 10. |
- Mitra, Aditee, et al.
(författare)
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The role of mixotrophic protists in the biological carbon pump
- 2014
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 11, s. 995-1005
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Tidskriftsartikel (refereegranskat)abstract
- The traditional view of the planktonic foodweb describes consumption of inorganic nutrientsby photo-autotrophic phytoplankton, which in turn supports zooplankton and ultimately higher trophic levels. Pathways centred on bacteria provide mechanisms for nutrient recycling. This structure lies at the foundation of most models used to explore biogeochemical cycling, functioning of the biological pump, and the impact of climate change on these processes. We suggest an alternative paradigm, which sees the bulk of the base of this foodweb supported by protist plankton (phytoplankton and microzooplankton) communities that are mixotrophic – combining phototrophy and phagotrophy within a single cell. The photoautotrophic eukaryotic plankton and their heterotrophic microzooplankton grazers dominate only within immature environments (e.g., spring bloom in temperate systems). With their flexible nutrition, mixotrophic protists dominate in more mature systems (e.g., temperate summer, established eutrophic systems and oligotrophic systems); the more stable water columns suggested under climate change may also be expected to favour these mixotrophs. We explore how such a predominantlymixotrophic structure affects microbial trophic dynamics and the biological pump. The mixotroph dominated structure differs fundamentally in its flow of energy and nutrients, with a shortened and potentially more efficient chain from nutrient regeneration to primary production. Furthermore, mixotrophy enables a direct conduit for the support of primary production from bacterial production. We show how the exclusion of an explicit mixotrophic component in studies of the pelagic microbial communities leads to a failure to capture the true dynamics of the carbon flow. In order to prevent a misinterpretation of the full implications of climate change upon biogeochemical cyclingand the functioning of the biological pump, we recommend inclusion of multi-nutrient mixotroph models within ecosystem studies.
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