| 92051. |
- Izsak, Julia
(författare)
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Human iPSC-derived neuronal networks. Development and application for compound evaluation
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Research on human brain development and function in health and disease has been hampered by limited access to primary human tissue and limited translatability of animal studies. This knowledge gap is encouraging the use of human induced pluripotent stem cell (hiPSC)-derived neural in vitro models. The current hope is that person-specific hiPSC-based in vitro models for human brain development and neuronal network function will increase the success in translating research results from bench to bedside. The aim of this thesis was to characterize and validate a person-specific human iPSC-based neural in vitro model to study the development, properties, and pharmacological modulation of human neuronal networks. In the first article we presented a procedure to generate 3D neural aggregates comprising astrocytes, oligodendrocytes and highly functional neurons that generated synchronous neuronal networks in less than three weeks. Further, by culturing hiPSC-derived 3D neural aggregates in human cerebrospinal fluid (hCSF), we demonstrated in article II that this adult brain-like milieu promotes morphological and functional maturation. Although hCSF is superior to currently used cell culture media, it has very limited availability for routine cell culturing purposes. This motivated the search for soluble factors that can mimic the observed maturational effects. In article III, we identified TGF-β1 as a physiologically relevant factor that can suppress proliferation and enhance neuronal and glial differentiation in a human 3D neural in vitro model. In article IV, we utilized this optimized model to provide insights in how therapeutically effective and overdose concentrations of lithium influence human single neuronal and network function. We showed that epileptiform discharges caused by overdose concentrations of lithium were suppressed by the antiepileptic drug Perampanel. The demonstrated functional impact of clinically relevant pharmacological compounds on human neuronal network function represents a proof-of-concept for the enhanced translational value of the human 3D neural aggregate in vitro model. The work presented in this thesis advances the field with a fast functional isogenic in vitro hiPSC-derived neuronal network model with improved physiological relevance and applicability for drug evaluation. Hopefully, our findings will bring the field of neuroscience closer to more translatable modeling and more successful clinical trials in the future.
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| 92052. |
- Izsak, Julia, et al.
(författare)
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Robust generation of person-specific, synchronously active neuronal networks using purely isogenic human iPSC-3D neural aggregate cultures
- 2019
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Ingår i: Frontiers in Neuroscience. - : Frontiers Media SA. - 1662-4548 .- 1662-453X. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Reproducibly generating human induced pluripotent stem cell-based functional neuronal circuits, solely obtained from single individuals, poses particular challenges to achieve personalized and patient specific functional neuronal in vitro models. A hallmark of functional neuronal assemblies, synchronous neuronal activity, can be non-invasively studied by microelectrode array (MEA) technology, reliably capturing physiological and pathophysiological aspects of human brain function. In our here presented manuscript, we demonstrate a procedure to generate 3D neural aggregates comprising astrocytes, oligodendroglial cells, and neurons obtained from the same human tissue sample. Moreover, we demonstrate the robust ability of those neurons to create a highly synchronously active neuronal network within 3 weeks in vitro, without additionally applied astrocytes. The fusion of MEA-technology with functional neuronal circuits solely obtained from one individual's cells represent isogenic person-specific human neuronal sensor chips that pave the way for specific personalized in vitro neuronal networks as well as neurological and neuropsychiatric disease modeling.
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| 92053. |
- Izsak, Julia, et al.
(författare)
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TGF-β1 Suppresses Proliferation and Induces Differentiation in Human iPSC Neural in vitro Models
- 2020
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Ingår i: Frontiers in Cell and Developmental Biology. - : Frontiers Media SA. - 2296-634X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Persistent neural stem cell (NSC) proliferation is, among others, a hallmark of immaturity in human induced pluripotent stem cell (hiPSC)-based neural models. TGF-β1 is known to regulate NSCs in vivo during embryonic development in rodents. Here we examined the role of TGF-β1 as a potential candidate to promote in vitro differentiation of hiPSCs-derived NSCs and maturation of neuronal progenies. We present that TGF-β1 is specifically present in early phases of human fetal brain development. We applied confocal imaging and electrophysiological assessment in hiPSC-NSC and 3D neural in vitro models and demonstrate that TGF-β1 is a signaling protein, which specifically suppresses proliferation, enhances neuronal and glial differentiation, without effecting neuronal maturation. Moreover, we demonstrate that TGF-β1 is equally efficient in enhancing neuronal differentiation of human NSCs as an artificial synthetic small molecule. The presented approach provides a proof-of-concept to replace artificial small molecules with more physiological signaling factors, which paves the way to improve the physiological relevance of human neural developmental in vitro models.
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| 92054. |
- Izugbara, Chimaroke, et al.
(författare)
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Ethnicity, livelihoods, masculinity, and health among Luo men in the slums of Nairobi, Kenya
- 2013
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Ingår i: Ethnicity and Health. - : Informa UK Limited. - 1355-7858 .- 1465-3419. ; 18:5, s. 483-498
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Tidskriftsartikel (refereegranskat)abstract
- Background. Previous research suggests that ethnic self-identity has little consequence for objective health outcomes compared to the structural dimensions of ethnicity. Methods. Using qualitative data, we investigated perceptions of ethnicity in relation to health among Luo men in the slums of Nairobi, Kenya. Results. While recognizing the complicated cultural origin of poor health, responding Luo men stressed on gender and everyday livelihood situations as being more critical for their health than Luo customs. Recognition of the structural causes of ill-health among the men overlapped with lay notions derived from particular expressions of Luo culture in urban slum contexts. To some extent, respondents regarded the performance of their sense of ethnic identity as protective, though they also admitted to the health-damaging repercussions of some of the ways they enacted aspects of Luo culture. Conclusion. Ethnic beliefs that link particular enactments of local customs with health outcomes may motivate the performance of cultural identity in ways that can produce critical health outcomes. Keywords: Kenya; Luo men; masculinity; poor health; slums; cultural beliefs; poverty
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| 92055. |
- Izugbara, Chimaroke
(författare)
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‘Life is Not Designed to be Easy for Men’: Masculinity and Poverty Among Urban Marginalized Kenyan Men
- 2015
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Ingår i: Gender Issues. - : Springer Science and Business Media LLC. - 1098-092X .- 1936-4717. ; 32:2, s. 121-137
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Tidskriftsartikel (refereegranskat)abstract
- Current analyses of poverty and economic marginality in relation to masculinity continue to ignore the direct perspectives of men whose lives form the crux of such investigations. I draw on interview and ethnographic data from two slums in Nairobi, Kenya’s capital city to address poor men’s constructions and performance of manliness in relation to poverty. Men acknowledged economic adversity as both a major constraint to their masculinity and a significant dynamic in their own evolution and development into ‘proper’ men. In striving for locally-valued masculine identities, particularly breadwinnerhood, Nairobi’s poor men advanced new values, narratives and strategies that both projected them as socially-respectable men and reconstituted their normatively ‘un-masculine’ actions as macho. Ironies suffuse masculinity in the slums of Nairobi, and are, in large part, driven by the critical and complex social dynamics and popular subjectivities, which poor men navigate while seeking to make valued masculinity both notionally and practically accessible for themselves. © 2015, Springer Science+Business Media New York.
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| 92056. |
- Izugbara, Chimaroke, et al.
(författare)
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Men, masculinity, and community development in Kenyan slums
- 2014
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Ingår i: Community Development. - : Routledge. - 1557-5330 .- 1944-7485. ; 45:1, s. 32-44
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Tidskriftsartikel (refereegranskat)abstract
- There is limited research on masculinity in relation to community development. Using ethnographic and interview data from two slums in Kenya and building on one of the more well-known definitions of community development, we explore men?s narratives of themselves in relation to community development. We highlight how men's cognizance of the structural and contextual constraints to the development of their communities intersected with both a feeling that they have helped to hamper community development and an adamant sense of their own criticality and centrality in ensuring it. While repudiating the idea that they have to change in order for their community to progress, men also generally hinged community development on their tenacious pursuit of traditional masculinity scripts. The rejection of mainstream masculinity norms as the basis for community progress will not resonate consistently among men. Social and community development work with men that fails to acknowledge them as gendered people may not succeed. © 2014 Community Development Society.
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| 92057. |
- Izugbara, Chimaroke, et al.
(författare)
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The Management of Unwanted Pregnancy Among Women in Nairobi, Kenya
- 2014
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Ingår i: International Journal of Sexual Health. - : Routledge. - 1931-7611 .- 1931-762X. ; 26:2, s. 100-112
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: This study probed both the meanings women ascribe to their unwanted pregnancies and the drivers of their choices in relation to the management of such pregnancies. Methods: Cross-sectional qualitative in-depth individual interviews were conducted with 80 women and girls in Nairobi, Kenya. Results: Gender, livelihoods, morality, marital status, and male partners exerted extensively complex and multidimensional influence on women's management of their unintentional pregnancies. For instance, although gender norms were frequently invoked to justify terminating unwanted pregnancies, they also regularly provided strong motivations for carrying such pregnancies to term. Conclusions: Urgently needed are programs and policies that support women to avoid unwanted pregnancies and help them respond safely and pragmatically to such pregnancies when they occur. © 2014 Copyright Taylor & Francis Group, LLC.
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| 92058. |
- Izumi, Hironari, et al.
(författare)
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Bacteria associated with ectomycorrhizas of slash pine (Pinus elliottii) in south-eastern Queensland, Australia
- 2008
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Ingår i: Fems Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 282:2, s. 196-204
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial communities associated with ectomycorrhizal and uncolonized roots of Pinus elliottii (slash pine) collected from a plantation in south-east Queensland, Australia, were investigated, using cultivation-dependent and -independent methods. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene PCR products obtained using a cultivation-independent approach revealed that bacterial communities associated with ectomycorrhizal root tips differed significantly from those associated with roots uncolonized by ectomycorrhizal fungi. DGGE analysis of cultivable bacterial communities revealed no significant difference between ectomycorrhizal and uncolonized roots. Neither analytical approach revealed significant differences between the bacterial communities associated with ectomycorrhizal roots colonized by a Suillus sp. or an Atheliaceae taxon. Cloned bacterial 16S rRNA genes revealed sequence types closely related with that of Burkholderia phenazinium, common in both ectomycorrhizal-colonized and -uncolonized roots, while sequence types most similar to the potentially phyopathogenic bacteria Burkholderia andropogonis and Pantoea ananatis were only detected in ectomycorrhizal roots. These results highlight the possibility of global movement of microorganisms, including putative pathogens, as a result of the introduction of exotic pine plantations.
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| 92059. |
- Izumi, H, et al.
(författare)
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Characterisation of endobacterial communities in ectomycorrhizas by DNA- and RNA-based molecular methods
- 2007
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Ingår i: Soil Biology and Biochemistry. ; 39:4, s. 891-899
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Tidskriftsartikel (refereegranskat)abstract
- The diversity of endobacteria associated with ectomycorrhizas of Suillus variegatus and Tomentellopsis submollis, in two Corsican pine (Pinus nigra) stands was analysed by cultivation-dependent and cultivation-independent molecular methods. Denaturing gradient gel electrophoresis (DGGE) analysis revealed the cultivable endobacterial communities associated with S. variegatus were similar within the same stand. The most abundant cultivable bacterial species belonged to the genera Pseudomonas and Burkholderia. Cultivation-independent molecular analysis indicated that the structure of the endobacterial communities in ectomycorrhizas was consistent across all samples regardless of ECM fungal species or the pine stand from which the samples were collected. However, comparison between rDNA- and rRNA-derived DGGE gels showed that metabolically active endobacterial species were not always detected in rDNA-based profiles. Clone libraries constructed from rRNA molecules indicated that Pseudomonas and Burkholderia spp. were metabolically active bacteria. As some of the most abundant cultivable bacteria, including Bacillus/Paenibacillus spp., were not detected in cultivation-independent DGGE profiles, a combination of cultivation-dependent and -independent approaches provided a more complete assessment of the diversity of endobacteria associated with ectomycorrhizas.
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| 92060. |
- Izumi, Hironari, et al.
(författare)
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Diversity and expression of nitrogenase genes (nifH) from ectomycorrhizas of Corsican pine (Pinus nigra).
- 2006
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Ingår i: Environmental microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 8:12, s. 2224-30
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Tidskriftsartikel (refereegranskat)abstract
- The diversity of bacterial nitrogenase genes (nifH) and their mRNA transcription in ectomycorrhizas of Corsican pine (Pinus nigra) were examined. DNA and RNA were extracted from surface-sterilized and non-sterilized Corsican pine roots colonized by the ectomycorrhizal (ECM) fungi, Suillus variegatus and Tomentellopsis submollis. DNA-derived nifH polymerase chain reaction (PCR) products were obtained from all samples, but only a few reverse transcription PCRs for nifH mRNA were successful, suggesting that nitrogenase genes were not always transcribed. Several different nifH sequences were detected and the bacteria actively transcribing nifH were different from those whose genes were detected through DNA-based PCR. Putative nitrogenase amino acid sequences revealed that more than half of the nifH products were derived from methylotrophic bacteria, such as Methylocella spp. The next most frequent sequence types were similar to those from Burkholderia.
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