| 1. |
- Nilsson Sköld, Helen, 1970, et al.
(författare)
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Stem Cells in Asexual Reproduction of Marine Invertebrates
- 2009
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Ingår i: Stem Cells in Marine Organisms. - Netherlands : Springer. - 9789048127665 ; , s. 105-137
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- While sexual reproduction is conserved and almost ubiquitous, asexual reproduction in forms of parthenogenesis or agametic cloning from somatic tissue is less conserved. The phylogeny shows that agametic cloning is widespread but scattered with many different modes for asexual formation of a new animal. This suggests that independent forms of cloning have evolved later from sexual ancestors between and within different phyla. Here, we present an overview of agametic cloning in the marine animal kingdom and discuss molecular and evolutionary aspects of somatic stem cell usage for asexual cloning. The molecular tissue characterizations and the relative role of different stem cells involved in agametic cloning are only at its beginning with whole phyla largely uncovered. An emerging hypothesis is that the first somatic stem cells used in cloning were also able to form a germ-line and that the more limited lineage specific stem cells are derived. We discuss advantages and problems with agametic cloning from somatic tissue and propose that the levels of stem cell potential held in the tissue can have large consequences for the reproductive life cycle strategies and long-term fitness in clonal animals and strains. We finally describe suitable molecular experimental approaches for future research on this topic.
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| 2. |
- Thorndyke, Michael C., 1946, et al.
(författare)
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Marine ecological genomics: when genomics meets marine ecology
- 2007
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Ingår i: Marine Ecology Progress Series. - 0171-8630. ; 332, s. 257-273
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Tidskriftsartikel (refereegranskat)abstract
- Genomics, proteomics and metabolomics (the ’omic’ technologies) have revolutionized the way we work and are able to think about working, and have opened up hitherto unimagined opportunities in all research fields. In marine ecology, while ‘standard’ molecular and genetic approaches are well known, the newer technologies are taking longer to make an impact. In this review we explore the potential and promise offered by genomics, genome technologies, expressed sequence tag (EST) collections, microarrays, proteomics and bar coding for modern marine ecology. Methods are succinctly presented with both benefits and limitations discussed. Through examples from the literature, we show how these tools can be used to answer fundamental ecological questions, e.g. ‘what is the relationship between community structure and ecological function in ecosystems?’; ‘how can a species and the phylogenetic relationship between taxa be identified?’; ‘what are the factors responsible for the limits of the ecological niche?’; or ‘what explains the variations in life-history patterns among species?’ The impact of ecological ideas and concepts on genomic science is also discussed.
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| 3. |
- Aspengren, Sara, 1977, et al.
(författare)
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Different strategies for color change
- 2009
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Ingår i: Cellular and Molecular Life Sciences (CMLS). - : Springer Science and Business Media LLC. - 1420-682X .- 1420-9071. ; 66, s. 187-191
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Forskningsöversikt (refereegranskat)
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| 4. |
- Aspengren, Sara, 1977, et al.
(författare)
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New Insights into Melanosome Transport in Vertebrate Pigment Cells
- 2008
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Ingår i: INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY, Vol 272 (edited by Kwang W. Jeon). - : Elsevier. - 9780123747471 ; 272, s. 245-302
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Pigment cells of lower vertebrates provide an excellent model to study organelle transport as they specialize in the translocation of pigment granules in response to defined chemical cues. This review will focus on the well-studied melanophore/melanocyte systems in fish, amphibians, and mammals. We will describe the roles of melanin, melanophores, and melanocytes in animals, current views on how the three motor proteins dynein, kinesin, and myosin-V are involved in melanosome transport along microtubules and actin filaments, and how signal transduction pathways regulate the activities of the motors to achieve aggregation and dispersion of melanosomes. We will also describe how melanosomes are transferred to surrounding skin cells in amphibians and mammals. Comparative studies have revealed that the ability of physiological color change is lost during evolution while the importance of morphological color change, mainly via transfer of pigment to surrounding skin cells, increases. In humans, pigment mainly has a role in protection against ultraviolet radiation, but also perhaps in the immune system.
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| 5. |
- Holm, K., et al.
(författare)
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Induced cell proliferation in putative haematopoietic tissues of the sea star, Asterias rubens (L.)
- 2008
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 211:16, s. 2551-2558
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Tidskriftsartikel (refereegranskat)abstract
- The coelomic fluid of the echinoderm Asterias rubens possesses large populations of circulating coelomocytes. This study aimed to expand the knowledge about the haematopoietic sources of these cells. Injection of the immune-stimulating molecules lipopolysaccharide (LPS) and concanavalin A (ConA) resulted in an increase in coelomocytes. To investigate if these molecules induce cell proliferation in putative haematopoietic tissues (HPTs), short-term exposure of the substitute nucleotide 5-bromo-2'-deoxyuridine (BrdU) was conducted. Immunohistochemical analysis, using fluorescein-labelled antibodies to trace BrdU, showed pronounced cell division in the coelomic epithelium and axial organ. In the pyloric caeca, not considered as an HPT, proliferation was not detected. BrdU labelling of monolayers of cells obtained by collagenase treatment of coelomic epithelium, axial organ and Tiedemann body revealed induced cell proliferation in response to both LPS and ConA while proliferation of pyloric caeca and circulating coelomocytes remained sparse. By using confocal microscopy it was observed that both the morphology and functional behaviour of cells released from explants of coelomic epithelium showed high similarity to those of circulating phagocytes. It was concluded that the increased coelomocyte numbers observed in response to LPS and ConA were reflected in an induced cell proliferation in coelomic epithelium, axial organ and Tiedemann body, which reinforces the idea that these organs are HPTs and the sources of coelomocyte renewal.
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| 6. |
- Nilsson Sköld, Helen, 1970, et al.
(författare)
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Assembly pathway of the anastral Drosophila oocyte meiosis I spindle
- 2005
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Ingår i: Journal of Cell Science. - 0021-9533. ; 118:8, s. 1745-1755
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Tidskriftsartikel (refereegranskat)abstract
- Oocyte meiotic spindles of many species are anastral and lack centrosomes to nucleate microtubules. Assembly of anastral spindles occurs by a pathway that differs from that of most mitotic spindles. Here we analyze assembly of the Drosophila oocyte meiosis I spindle and the role of the Nonclaret disjunctional (Ncd) motor in spindle assembly using mild-type and mutant Ncd fused to GFP. Unexpectedly, we observe motor-associated asters at germinal vesicle breakdown that migrate towards the condensed chromosomes, where they nucleate microtubules at the chromosomes. Newly nucleated microtubules are randomly oriented, then become organized around the bivalent chromosomes. We show that the meiotic spindle forms by lateral associations of microtubule-coated chromosomes into a bipolar spindle. Lateral interactions between microtubule-associated bivalent chromosomes may be mediated by microtubule crosslinking by the Ncd motor, based on analysis of fixed oocytes. We report here that spindle assembly occurs in an ncd mutant defective for microtubule motility, but lateral interactions between microtubule-coated chromosomes are unstable, indicating that Ncd movement along microtubules is needed to stabilize interactions between chromosomes. A more severe ncd mutant that probably lacks ATPase activity prevents formation of lateral interactions between chromosomes and causes defective microtubule elongation. Anastral Drosophila oocyte meiosis I spindle assembly thus involves motor-associated asters to nucleate microtubules and Ncd motor activity to form and stabilize interactions between microtubule-associated chromosomes during the assembly process. This is the first complete account of assembly of an anastral spindle and the specific steps that require Ncd motor activity, revealing new and unexpected features of the process.
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| 7. |
- Nilsson Sköld, Helen, 1970
(författare)
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Fina fisken - forskaren och fisken snackar färg
- 2009
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Ingår i: havsutsikt. ; 2, s. 10-11
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Alla djur har olika färger och mönster. Det beror på den unika fördelningen och sammansättningen av olika färgpigment på kroppen. Pigmenten bildas i speciella celler för att sedan transporteras ut i hår och päls hos människa och andra däggdjur. I fisk och grodor används pigmenten istället för att växla färg.
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| 8. |
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| 9. |
- Rosenberg, Rutger, 1943, et al.
(författare)
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Biology of the basket star Gorgonocephalus caputmedusae (L.)
- 2005
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Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 148, s. 43-50
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Tidskriftsartikel (refereegranskat)abstract
- Ophiurid basket stars belonging to the family Gorgonocephalidae are distributed from the Arctic to the Antarctic and from the shallow subtidal to the deep sea, but their biology remains poorly known. In situ observations at the mouth of the Oslofjord by a remotely operated vehicle showed that Gorgonocephalus caputmedusae had a patchy distribution at 85 to 120 m water depth and frequently occurred in association with the gorgonian Paramuricea placomus and the coral Lophelia pertusa. Morphological and histological studies show that G. caputmedusae is well adapted to capture macroplanktonic prey. Histological examination of the arms revealed the presence of a thick layer of dermal mutable connective tissue which is probably an energyefficient way to maintain its feeding posture against the current. This layer is connected to the nerve cord suggesting that the passive mechanical properties (stiffness) is controlled by the nervous system. In the distal parts of the arms, each segment has a pair of sticky tube feet and a sophisticated system of spines and hooks, which are connected to muscles and collagenous tendons. In combination, these features were shown, in an experimental flume study, to be used for capturing the locally abundant krill species Meganyctiphanes norvegica. This is the first documentation of G. caputmedusae of this kind
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| 10. |
- Sciambi, C. J., et al.
(författare)
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A bidirectional kinesin motor in live Drosophila embryos
- 2005
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Ingår i: Traffic. - 1398-9219. ; 6:11, s. 1036-1046
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Tidskriftsartikel (refereegranskat)abstract
- Spindle assembly and elongation involve poleward and away-from-the-pole forces produced by microtubule dynamics and spindle-associated motors. Here, we show that a bidirectional Drosophila Kinesin-14 motor that moves either to the microtubule plus or minus end in vitro unexpectedly causes only minor spindle defects in vivo. However, spindles of mutant embryos are longer than wild type, consistent with increased plus-end motor activity. Strikingly, suppressing spindle dynamics by depriving embryos of oxygen causes the bidirectional motor to show increased accumulation at distal or plus ends of astral microtubules relative to wild type, an effect not observed for a mutant motor defective in motility. Increased motor accumulation at microtubule plus ends may be due to increased slow plus-end movement of the bidirectional motor under hypoxia, caused by perturbation of microtubule dynamics or inactivation of the only other known Drosophila minus-end spindle motor, cytoplasmic dynein. Negative-stain electron microscopy images are consistent with highly cooperative motor binding to microtubules, and gliding assays show dependence on motor density for motility. Mutant effects of the bidirectional motor on spindle function may be suppressed under normal conditions by motor: motor interactions and minus-end movement induced by spindle dynamics. These forces may also bias wild-type motor movement toward microtubule minus ends in live cells. Our findings link motor : motor interactions to function in vivo by showing that motor density, together with cellular dynamics, may influence motor function in live cells.
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