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- Dahl, Lina, 1981-
(författare)
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Stem cell function and organ development : analysis of Lhx2 function in hematopoietic stem cells and eye development
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When a multicellular organism suffers damages to tissues/organs it heals itself by either substituting the lost cellular matrix by scar formation or by regenerating the lost tissue. Regeneration likely occurs by a recapitulation of the developmental process that formed the organ. Many processes regulating organ development are based on epithelial-mesenchymal interactions and a strict control of organ specific stem/progenitor cells. Elucidation of the molecular basis of these processes is therefore vital in order to develop novel therapies in regenerative medicine. The LIM homebox gene Lhx2 is interesting in this context since Lhx2 has been shown to be important for the formation of several organs by regulating epithelial-mesenchymal interactions and progenitor cell function. Targeted inactivation of Lhx2 leads to a lethal anemia due to malformed liver and severe neural abnormalities such as hypoplasia of the forebrain and anophtalmia. Thus, elucidation of the mechanisms of the function of Lhx2 in different organ systems would give important insights into the molecular mechanisms regulating epithelial-mesenchymal interactions and stem/progenitor cell function. To elucidate the function of Lhx2 in the hematopoietic system Lhx2 was initially expressed in hematopoietic progenitor cells derived from ES cells differentiated in vitro using retroviral vectors. This approach led to the generation of hematopoietic stem cell (HSC)-like cell lines suggesting that Lhx2 could impact HSC function. However neither the specificity nor the efficiency of the Lhx2-induced phenotype could be determined using this approach. To be able to elucidate the function of Lhx2 in the hematopoietic system, an ES cell line with inducible Lhx2 expression was generated. Lhx2 expression induces self-renewal of a distinct hematopoietic progenitor cell from which HSC-like cell lines were established. Down-regulation of Lhx2 in these HSC-like cell lines leads to a rapid loss of stem cell character, providing a good model to study the molecular function of Lhx2 in hematopoietic stem/progenitor cells. A global gene expression analysis was performed comparing the Lhx2+ stem cell population to the Lhx2- differentiated progeny. This approach identified genes putatively linked to self-renewal/differentiation of HSCs. A considerable proportion of the genes showed an overlapping gene expression pattern with Lhx2 expression in tissue of non-hematopoietic origin suggesting that Lhx2 function in stem/progenitor cells partly overlap with Lhx2 function during organ development. In order to define other Lhx2-dependent progenitor cell populations and to generate a tool to analyze the function of Lhx2 in organ development a new transgenic mouse model was generated. By using a specific part of the Lhx2 promoter to drive expression of Cre recombinase in vivo (Lhx2-Cre mice) we have been able to define the first eye committed progenitor cells in the forebrain. By using the Lhx2-Cre mice it will be possible to distinguish the function of genes during eye development from their function in the patterning of the forebrain e.g. the eye field transcription factors. Conditional inactivation of Lhx2 in these eye specific progenitor cells causes an immediate developmental arrest. The transgene is also active in Lhx2-/- embryonic forebrain, but re-expression of Lhx2 in Lhx2-/- progenitor cells only promote formation of retinal pigment epithelium cells. Analysis of genes expressed by the Lhx2+ stem cell population allowed us to define novel genes putatively linked to Lhx2 function in eye development. Thus, we have defined the progenitor cells in the forebrain committed to eye development and the expansion and patterning of these progenitors are dependent on Lhx2. Although commitment to eye development is Lhx2-independent, Lhx2 might be important for the acquisition of the oligopotent fate of these progenitor cells.
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| 4. |
- Jaakkola, Maarit, et al.
(författare)
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Exploring the Normative Foundation of Journalism Education: Nordic Journalism Educators’ Conceptions of Future Journalism and Professional Qualifications
- 2022
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Ingår i: Journalism and Media. - : MDPI AG. - 2673-5172. ; 3:3, s. 436-452
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Tidskriftsartikel (refereegranskat)abstract
- This article deals with Nordic journalism educators’ conceptions of journalism by placing the concept of normativity at the center. The values, norms and ideas concerning journalism and journalistic practice have previously been studied by journalists and journalism students around the world and in the Nordics, while the Nordic journalism educators’ conceptions have remained more or less without attention. Nevertheless, journalism educators play a crucial role in defining what journalism is and what it is not, and thus largely affect future practitioners’ ideas of journalism. Using a questionnaire that has been employed in previous studies, journalism educators within the academic journalism training in Denmark, Finland, Iceland, Norway and Sweden (n = 115) were surveyed in terms of their conceptions. It was found that the journalism educators, of which 35 per cent had a doctoral degree, still largely subscribe to the ideas of the welfare state. In addition, the ideas of slow, investigative, constructive and solutions-based journalism have gained high popularity among the Nordic educators, which, we argue, dovetails well with the pedagogical aims of journalism education.
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| 5. |
- Jaakkola, Maarit
(författare)
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Finland: en lång tradition av mediefostran
- 2018
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Ingår i: Medie- och informationskunnighet i den digitala tidsåldern: en demokratifråga. - Göteborg : Nordicom. - 9789187957963 ; , s. 181-186
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Liu, Y. Q., et al.
(författare)
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An engineering model for transient analysis of grounding system under lightning strikes : Nonuniform transmission-line approach
- 2005
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Ingår i: IEEE Transactions on Power Delivery. - 0885-8977 .- 1937-4208. ; 20:2, s. 722-730
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Tidskriftsartikel (refereegranskat)abstract
- A nonuniform transmission line approach is adopted in this paper for modeling the transient behavior of different types of grounding systems under lightning strikes in time domain by solving Telegrapher's equations based on finite-difference time-domain (FDTD) technique. Electromagnetic couplings between different parts of the grounding wires are included using effective per-unit length parameters (l, c, and g), which are space and time dependent. The present model can predict both the effective length and the transient voltage of grounding electrodes accurately, while, an uniform transmission line approach with electrode length dependent per-unit length parameters [19]-[22] fails to predict the same. Unlike the circuit theory approach [1]-[4], the present model is capable of predicting accurately the surge propagation delay in the large grounding system. The simulation results for buried horizontal wires and grounding grids based on the present model are in good agreement with that of the circuit and electromagnetic field approaches [3], [9]. From an engineering point of view, the model presented in this paper is sufficiently accurate, time efficient, and easy to apply.
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| 9. |
- Suárez-Rojas, Chaitanya, et al.
(författare)
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Sustainability in whale-watching : a literature review and future research directions based on regenerative tourism
- 2023
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Ingår i: Tourism Management Perspectives. - : Elsevier. - 2211-9736 .- 2211-9744. ; 47
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Forskningsöversikt (refereegranskat)abstract
- There is scientific consensus that human activity through whale-watching is causing an increasing amount of damage to the natural environment, which poses critical challenges to the goal of sustainability. Based on a quantitative and qualitative assessment of the scientific literature, this study calls for urgent rethinking in regards to whale-watching sustainability. A new, integrative framework for research actions built upon the concept of regenerative tourism is provided so as to lead to a more balanced evaluation of environmentally and socially responsible whale-watching tourism. The assessment of the literature review leads to three main research areas that have driven the research field in whale-watching tourism: the ecological responses of cetaceans due to human disturbance, the determinants of whale-watching tourism demand, and the impact of tourism on sustainability from macro-cultural and political perspectives. The new integrative framework, which additionally considers innovation and external drivers as prominent research areas, proposes future guidelines for studying the interplay between some of the more specific research topics: social change, economic drivers, gender perspective, co-creation, social responsibility, technology, climate change and long-term cumulative effects, among other issues of concern.
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