| 1. |
- Ankarberg, Emma, 1973-
(författare)
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Neurotoxic Effects of Nicotine During Neonatal Brain Development : Critical Period and Adult Susceptibility
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis examined neurotoxic effects of nicotine exposure during a defined critical period of neonatal brain development in mice.In our environment there are numerous hazardous contaminants that an individual can be exposed to during its entire lifetime. In many mammalian species the neonatal period is characterised by a rapid development of the brain. The present studies have identified a defined critical period during the neonatal brain development in mice, where exposure to low doses of nicotine causes permanent disturbances in the cholinergic nicotinic receptors and altered behaviour response to nicotine at adult age. This adult reaction to nicotine, a hypoactive response, was the opposite of that observed in control animals and animals exposed to nicotine before or after this period. Animals showing a hypoactive response to nicotine lacked nicotinic low affinity binding sites in the cerebral cortex. Furthermore, neonatal exposure to nicotine affected learning and memory in adult animals, an effect that was time-dependent. This thesis also showed that neonatal exposure to nicotine increased adult susceptibility to a repeated exposure of nicotine, manifested as an even more pronounced effect in spontaneous behaviour after challenging doses of nicotine. In these animals the nicotinic receptors in the cerebral cortex, assayed by a-bungarotoxin, was decreased. Neonatal exposure to nicotine was also shown to increase adult susceptibility to the organophosphate paraoxon, a known cholinergic agent, and to the brominated flame retardant 2,2´,4,4´,5-pentabromodiphenyl ether, a novel environmental agent, at adult age. This was seen at doses that did not affect behaviour in control animals, and was manifested as deranged spontaneous behaviour and reduced habituation, aberrations that also worsened with age. The results indicate that differences in adult susceptibility to environmental pollutants are not necessarily an inherited condition. Rather they may well be acquired by low dose exposure to toxic agents during early life.
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| 2. |
- Pace, Michael L., et al.
(författare)
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Whole-lake carbon-13 additions reveal terrestrial support of aquatic food webs
- 2004
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 427:6971, s. 240-243
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Tidskriftsartikel (refereegranskat)abstract
- Ecosystems are supported by organic carbon from two distinct sources. Endogenous carbon is produced by photosynthesis within an ecosystem by autotrophic organisms. Exogenous carbon is produced elsewhere and transported into ecosystems. Consumers may use exogenous carbon with consequent influences on population dynamics, predator-prey relationships and ecosystem processes(1). For example, exogenous inputs provide resources that may enhance consumer abundance beyond levels supported by within-system primary production(2). Exogenous fluxes of organic carbon to ecosystems are often large, but this material is recalcitrant and difficult to assimilate, in contrast to endogenously produced organic matter, which is used more easily(3,4). Here we show, by the experimental manipulation of dissolved inorganic C-13 in two lakes, that internal primary production is insufficient to support the food webs of these ecosystems. Additions of NaH (CO3)-C-13 enriched the C-13 content of dissolved inorganic carbon, particulate organic carbon, zooplankton and fish. Dynamics of C-13 indicate that 40-55% of particulate organic carbon and 22-50% of zooplankton carbon are derived from terrestrial sources, showing that there is significant subsidy of these ecosystems by organic carbon produced outside their boundaries.
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| 3. |
- Rehnström, Emma, et al.
(författare)
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Evidence of a Late Precambrian (637 Ma) deformational event in the Caledonides of northern Sweden
- 2002
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Ingår i: Journal of Geology. - 0022-1376. ; 110:5, s. 591-601
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Tidskriftsartikel (refereegranskat)abstract
- The Caledonian nappes in Scandinavia record two main phases of early Paleozoic metamorphism, but their pre-Caledonian tectonothermal history and paleogeographic position are largely unknown. Here we present a U-Pb age of 637+/-3 Ma for metamorphic titanite in the 1776+/-4 Ma (zircon age) Skarja granitic gneiss in northern Sweden. The titanite age is interpreted to represent a Neoproterozoic tectonometamorphic overprint. Geochronologic and paleogeographic considerations suggest that the gneiss was located at the outermost margin of pre-Caledonian (northwest) Baltica and was affected by Neoproterozoic tectonic activity related to terrane accretion, the Baikalian (or Timanian) orogeny, coincident with Cadomian terrane accretion along the Gondwanan margin of northern South America and northwest Africa.
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| 4. |
- Rehnström, Emma, et al.
(författare)
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Palaeoproterozoic U-Pb ages of autochthonous and allochthonous granites from the northern Swedish Caledonides - regional and palaeogeographic implications
- 2004
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Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 132:4, s. 363-378
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Tidskriftsartikel (refereegranskat)abstract
- In the Silurian, Baltica and Laurentia collided to form the Caledonian orogenic belt. During this process, nappes derived from the pre-collisional Baltic margin, from outboard terranes of Baltica, and from exotic terranes of probable Laurentian origin, respectively, were thrust upon the indenting Baltica. The Middle Allochthon is a tectonostratigraphic level inferred to represent the rifted Neoproterozoic margin of Baltica and is heterogeneously composed of telescoped fault-controlled sedimentary basins and subjacent basement plinths. In the Akkajaure area of northern Sweden, the Middle Allochthon consists mainly of granites (Akkajaure Nappe Complex). The Ritsem Granite, a part of the (para-) authochthonous basement below the nappe complexes, yields a U-Pb zircon and titanite age of 1871 +/- 11 Ma. Granite and felsic dykes in the lowermost thrust-sheet in the Middle Allochthon yield ages of 1800 +/- 2 Ma and 1795 +/- 4 Ma, respectively. The granite of the overlying thrust-sheet is 1781 +/- 2 Ma old and crosscutting dykes are 1779 +/- 7 Ma. These ages constrain the pre-Caledonian position of the nappe complex to the general region west of Lofoten, northwestern Norway, substantiating a link with the Transscandinavian Igneous Belt (TIB) of the Fennoscandian Shield. (C) 2004 Elsevier B.V. All rights reserved.
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| 5. |
- Sparr, Emma, et al.
(författare)
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Islet amyloid polypeptide-induced membrane leakage involves uptake of lipids by forming amyloid fibers
- 2004
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Ingår i: FEBS Letters. - : Wiley. - 1873-3468 .- 0014-5793. ; 577:1-2, s. 117-120
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Tidskriftsartikel (refereegranskat)abstract
- Fibril formation of islet amyloid polypeptide (IAPP) is associated with cell death of the insulin-producing pancreatic beta-cells in patients with Type 2 Diabetes Mellitus. A likely cause for the cytotoxicity of human TAPP is that it destroys the barrier properties of the cell membrane. Here, we show by fluorescence confocal microscopy on lipid vesicles that the process of hIAPP amyloid formation is accompanied by a loss of barrier function, whereby lipids are extracted from the membrane and taken up in the forming amyloid deposits. No membrane interaction was observed when preformed fibrils were used. It is proposed that lipid uptake from the cell membrane is responsible for amyloid-induced membrane damage and that this represents a general mechanism underlying the cytotoxicity of amyloid forming proteins. (C) 2004 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
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| 6. |
- Thapper, Anders, et al.
(författare)
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Reversible -coordination of triallylphosphine in a trinuclear ruthenium carbonyl cluster
- 2004
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Ingår i: Inorganic Chemistry Communications. - : Elsevier BV. - 1879-0259 .- 1387-7003. ; 7:3, s. 443-446
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Tidskriftsartikel (refereegranskat)abstract
- The triallylphosphine-substituted clusters [Ru3(CO)11{P(CH2CH=CH2)3}], [Ru3(CO)10{P(CH2CH=CH2)3}2] and [Ru3(CO)10{;-CH2=CHCH2P(CH2CH=CH2)2}] have been prepared; reaction of [Ru3(CO)10{;-CH2=CHCH2P(CH2CH=CH2)2}] with phosphines/phosphites leads to cleavage of the Ru–allyl -bond and formation of [Ru3(CO)11{P(CH2CH=CH2)3}(PR3)].
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