| 1. |
- Burzynska, A Z, et al.
(författare)
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Age-related differences in white matter microstructure : region-specific patterns of diffusivity.
- 2010
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Ingår i: NeuroImage. - San Diego ; Orlando, Fla : Elsevier BV. - 1053-8119 .- 1095-9572. ; 49:3, s. 2104-2112
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Tidskriftsartikel (refereegranskat)abstract
- We collected MRI diffusion tensor imaging data from 80 younger (20-32 years) and 63 older (60-71 years) healthy adults. Tract-based spatial statistics (TBSS) analysis revealed that white matter integrity, as indicated by decreased fractional anisotropy (FA), was disrupted in numerous structures in older compared to younger adults. These regions displayed five distinct region-specific patterns of age-related differences in other diffusivity properties: (1) increases in both radial and mean diffusivity; (2) increases in radial diffusivity; (3) no differences in parameters other than FA; (4) a decrease in axial and an increase in radial diffusivity; and (5) a decrease in axial and mean diffusivity. These patterns suggest different biological underpinnings of age-related decline in FA, such as demyelination, Wallerian degeneration, gliosis, and severe fiber loss, and may represent stages in a cascade of age-related degeneration in white matter microstructure. This first simultaneous description of age-related differences in FA, mean, axial, and radial diffusivity requires histological and functional validation as well as analyses of intermediate age groups and longitudinal samples.
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| 2. |
- Burzynska, A Z, et al.
(författare)
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Microstructure of frontoparietal connections predicts cortical responsivity and working memory performance
- 2011
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Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 21:10, s. 2261-2271
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Tidskriftsartikel (refereegranskat)abstract
- We investigated how the microstructure of relevant white matter connections is associated with cortical responsivity and working memory (WM) performance by collecting diffusion tensor imaging and verbal WM functional magnetic resonance imaging data from 29 young adults. We measured cortical responsivity within the frontoparietal WM network as the difference in blood oxygenation level-dependent (BOLD) signal between 3-back and 1-back conditions. Fractional anisotropy served as an index of the integrity of the superior longitudinal fasciculi (SLF), which connect frontal and posterior regions. We found that SLF integrity is associated with better 3-back performance and greater task-related BOLD responsivity. In addition, BOLD responsivity in right premotor cortex reliably mediated the effects of SLF integrity on 3-back performance but did not uniquely predict 3-back performance after controlling for individual differences in SLF integrity. Our results suggest that task-related adjustments of local gray matter processing are conditioned by the properties of anatomical connections between relevant cortical regions. We suggest that the microarchitecture of white matter tracts influences the speed of signal transduction along axons. This in turn may affect signal summation at neural dendrites, action potential firing, and the resulting BOLD signal change and responsivity.
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| 3. |
- Shore, R. C., et al.
(författare)
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The Structure and Composition of Deciduous Enamel Affected by Local Hypoplastic Autosomal Dominant Amelogenesis Imperfecta Resulting from an ENAM Mutation
- 2010
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Ingår i: Cells Tissues Organs. - : S. Karger. - 1422-6405 .- 1422-6421. ; 191:4, s. 301-306
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Tidskriftsartikel (refereegranskat)abstract
- In a group of families in northern Sweden, a mutation in the ENAM gene (predicted to produce a highly truncated protein) results in the local hypoplastic form of autosomal dominant amelogenesis imperfecta. In this study, sections of deciduous teeth from members of 3 of these families were examined by scanning electron microscopy (SEM) and the enamel mineral was analysed by energy dispersive X-ray spectroscopy (EDX). The sections were also probed with antibodies raised to a conserved sequence of the enamelin protein. Selected intact teeth were first analysed by digital imaging and ascribed with an 'Enamel Defects Index' (EDI) score. SEM of tooth sections revealed disrupted prism morphology and the prisms had a glass-like appearance in some areas. These areas of dysplasia were sometimes irregular but formed regular arrays in others. Comparison of EDI scores with SEM indicated that in one tooth the surface had no measurable defects but significant defects were present in the underlying enamel microstructure. SEM immunohistochemistry with the antibody raised to a fragment of the enamelin protein produced positive, but light, labelling throughout normal enamel. In dysplastic areas, however, the labelling intensity appeared to be reduced. The results indicate that the presence of functional enamelin in the correct amounts is necessary for correct prism morphogenesis. In addition, a combination of EDI and structural analysis indicate that defects in enamel microstructure are not necessarily visible as defects on the surface of the tooth, suggesting the possibility, at least, that some instances of under-diagnosis may occur. Copyright (C) 2009 S. Karger AG, Basel
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| 4. |
- Wang, R., et al.
(författare)
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Do cardiovascular risk factors explain the link between white matter hyperintensities and brain volumes in old age? : A population-based study
- 2014
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Ingår i: European Journal of Neurology. - : Wiley. - 1351-5101 .- 1468-1331. ; 21:8, s. 1076-1082
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: White matter hyperintensities (WMHs) and brain atrophy frequently coexist in older people. However, it is unclear whether the association between these two brain lesions is dependent on the aging process, a vascular mechanism or genetic susceptibility. It was therefore investigated whether the association between load of WMHs and brain atrophy measures is related to age, vascular risk factors (VRFs) or the APOE-epsilon 4 allele. Methods: This population-based study included 492 participants (age >= 60 years, 59.6% women) free of dementia and stroke. Data on demographics, VRFs and APOE genotypes were collected through interviews, clinical examination and laboratory tests. WMHs on magnetic resonance images were assessed using manual visual rating and automatic volumetric segmentation. Hippocampal and ventricular volumes were manually delineated, whereas total gray matter (GM) volume was measured by automatic segmentation. Data were analyzed with multivariate linear regression models. Results: More global WMHs, assessed using either a visual rating scale or a volumetric approach, were significantly associated with lower GM volume and higher ventricular volume; the associations remained significant after adjusting for age, VRFs and the APOE-epsilon 4 allele. In contrast, the association between global WMHs and hippocampal volume was no longer significant after adjusting for age, whereas adjustment for VRFs and APOE-epsilon 4 had no influential effect. Conclusion: The association of global WMHs with lower GM volume and higher ventricular volume is independent of age, VRFs and APOE-epsilon 4 allele, suggesting that the process of cerebral microvascular disease and neurodegeneration are associated independently of the normal aging process, vascular mechanisms or genetic susceptibility.
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| 5. |
- Broman, T, et al.
(författare)
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Molecular Detection of Persistent Francisella tularensis Subspecies holarctica in Natural Waters
- 2011
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Ingår i: International Journal of Microbiology. - : Hindawi Publishing Corporation. - 1687-918X .- 1687-9198. ; 2011, s. Article ID 851946-
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Tidskriftsartikel (refereegranskat)abstract
- Tularemia, caused by the bacterium Francisella tularensis, where F. tularensis subspecies holarctica has long been the cause of endemic disease in parts of northern Sweden. Despite this, our understanding of the natural life-cycle of the organism is still limited. During three years, we collected surface water samples (n = 341) and sediment samples (n = 245) in two areas in Sweden with endemic tularemia. Real-time PCR screening demonstrated the presence of F. tularenis lpnA sequences in 108 (32%) and 48 (20%) of the samples, respectively. The 16S rRNA sequences from those samples all grouped to the species F. tularensis. Analysis of the FtM19InDel region of lpnA-positive samples from selected sampling points confirmed the presence of F. tularensis subspecies holarctica-specific sequences. These sequences were detected in water sampled during both outbreak and nonoutbreak years. Our results indicate that diverse F. tularensis-like organisms, including F. tularensis subsp. holarctica, persist in natural waters and sediments in the investigated areas with endemic tularemia.
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| 6. |
- Qiu, C., et al.
(författare)
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Medial temporal lobe is vulnerable to vascular risk factors in men : a population based study
- 2012
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Ingår i: European Journal of Neurology. - : Wiley. - 1351-5101 .- 1468-1331. ; 19:6, s. 876-883
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Vascular risk factors (VRFs) are known to cause cerebral microvascular disease, but evidence supporting an effect of VRFs on regional brain atrophy is mixed. We investigate whether an aggregation of VRFs is associated with volume of hippocampus and entorhinal cortex in elderly people living in the community. Methods: This cross-sectional study consists of 523 participants (age =60 years, 59.3% women) of the SNAC-K Study in central Stockholm, Sweden, who were free of clinical stroke and cognitive impairment. We collected data on VRFs through interviews, clinical examination and inpatient register system. Hippocampal and entorhinal cortex volume was manually measured on magnetic resonance images. Data were analysed with general linear regression models controlling for demographics and total intracranial volume. Results: In men, high total cholesterol and diabetes were significantly or marginally associated with smaller hippocampus and entorhinal cortex; when current smoking, binge alcohol drinking, high cholesterol and diabetes were aggregated, an increasing number of VRFs were significantly associated with decreasing volume of hippocampus and entorhinal cortex (P for linear trend <0.01). In women, none of individual VRFs or their aggregation was significantly associated with the volume of these brain regions, except former smoking that was significantly associated with a larger volume of these regions. Conclusions: Aggregation of VRFs is associated with reduced hippocampal and entorhinal cortex volume in apparently healthy elderly men, but not in women. This implies that in men, the medial temporal lobe is vulnerable to cardiovascular risk factors.
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