| 1. |
- Chibnik, L. B., et al.
(författare)
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Trends in the incidence of dementia: design and methods in the Alzheimer Cohorts Consortium
- 2017
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Ingår i: European Journal of Epidemiology. - : Springer Science and Business Media LLC. - 0393-2990 .- 1573-7284. ; 32:10, s. 931-938
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have reported a decline in incidence of dementia which may have large implications for the projected burden of disease, and provide important guidance to preventive efforts. However, reports are conflicting or inconclusive with regard to the impact of gender and education with underlying causes of a presumed declining trend remaining largely unidentified. The Alzheimer Cohorts Consortium aggregates data from nine international population-based cohorts to determine changes in the incidence of dementia since 1990. We will employ Poisson regression models to calculate incidence rates in each cohort and Cox proportional hazard regression to compare 5-year cumulative hazards across study-specific epochs. Finally, we will meta-analyse changes per decade across cohorts, and repeat all analysis stratified by sex, education and APOE genotype. In all cohorts combined, there are data on almost 69,000 people at risk of dementia with the range of follow-up years between 2 and 27. The average age at baseline is similar across cohorts ranging between 72 and 77. Uniting a wide range of disease-specific and methodological expertise in research teams, the first analyses within the Alzheimer Cohorts Consortium are underway to tackle outstanding challenges in the assessment of time-trends in dementia occurrence.
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| 2. |
- Landin-Olsson, Mona, et al.
(författare)
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Immunoreactive trypsin(Ogen) in the sera of children with recent-onset insulin-dependent diabetes and matched controls
- 1990
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Ingår i: Pancreas. - : Ovid Technologies (Wolters Kluwer Health). - 0885-3177. ; 5:3, s. 241-247
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate the exocrine pancreatic function at the time of diagnosis of insulin-dependent diabetes mellitus, we determined immunoreactive an-odal and cathodal trypsin(ogen) levels in sera from almost all children (n = 375) 0-14 years of age in Sweden in whom diabetes developed during 1 year, and in sex-, age-, and geographically matched control subjects (n = 312). The median level of anodal trypsin(ogen) was 5 (quartile range, 3-7) µg/L in children with newly diagnosed diabetes, compared with a median level of 7 (quartile range, 4-8) µg/L in control subjects (p < 0.0001). Similarly, the median level of cathodal trypsin(ogen) was 8 (quartile range, 4-10) µg/L in children with diabetes, compared with a median level of 11 (quartile range, 7-15) µg/L in control subjects (p < 0.0001). The median of the individual ratios between cathodal and anodal trypsin(ogen) was 1.4 in the diabetic patients and 1.7 in the control children (p < 0.001). In a multivariate test, however, only the decrease in cathodal trypsin(ogen) concentration was associated with diabetes. The levels of trypsin(ogen)s did not correlate with levels of islet cell antibodies, present in 81% of the diabetic children. Several mechanisms may explain our findings, for example, similar pathogenetic factors may affect both the endocrine and exocrine pancreas simultaneously, a failing local trophic stimulation by insulin on the exocrine cells may decrease the trypsinogen production, and there may be an increased elimination of trypsin(ogen) because of higher filtration through the kidneys in the hyperglycemic state.
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| 3. |
- 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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| 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. |
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| 6. |
- Hassing, L, et al.
(författare)
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Mortality-related differences and changes in episodic memory among the oldest old : evidence from a population-based sample of nonagenarians
- 2002
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Ingår i: Aging, Neuropsychology and Cognition. - : Taylor & Francis. - 1382-5585 .- 1744-4128. ; 9:1, s. 11-20
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Tidskriftsartikel (refereegranskat)abstract
- We examined cross-sectional differences and longitudinal changes in episodic memory performance related to impending death among a group of very old people, aged 90–101 years. Participants were assessed at 3 measurement points across a 6-year interval. Three groups were identified: those who survived the entire follow-up period (n =40), those who died before the first follow-up (n =44), and those who died after the first follow-up (n =14). Participants completed a battery of episodic memory tasks consisting of face recognition, word recognition, word recall, and object recall with selective reminding. Those who survived performed better than those who were going to die in object recall at baseline. A Cox regression analysis, controlling age, revealed that object recall performance was significantly related to subsequent mortality status. Longitudinal analyses demonstrated significant 3-year decline for both face recognition and object recall, but no evidence of differential decline as a function of mortality group. Thus, longitudinal changes in memory preceding death were not as pronounced as the corresponding cross-sectional differences in this very old sample. In general, the results suggest that mortality-related memory deficits are present in extreme old age, although these deficits are relatively small and task-specific.
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| 7. |
- Khan, Wasim, et al.
(författare)
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A Multi-Cohort Study of ApoE epsilon 4 and Amyloid-beta Effects on the Hippocampus in Alzheimer's Disease
- 2017
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Ingår i: Journal of Alzheimer's Disease. - 1387-2877 .- 1875-8908. ; 56:3, s. 1159-1174
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Tidskriftsartikel (refereegranskat)abstract
- The apolipoprotein E (APOE) gene has been consistently shown to modulate the risk of Alzheimer's disease (AD). Here, using an AD and normal aging dataset primarily consisting of three AD multi-center studies (n = 1,781), we compared the effect of APOE and amyloid-beta (A beta) on baseline hippocampal volumes in AD patients, mild cognitive impairment (MCI) subjects, and healthy controls. A large sample of healthy adolescents (n = 1,387) was also used to compare hippocampal volumes between APOE groups. Subjects had undergone a magnetic resonance imaging (MRI) scan and APOE genotyping. Hippocampal volumes were processed using FreeSurfer. In the AD and normal aging dataset, hippocampal comparisons were performed in each APOE group and in epsilon 4 carriers with positron emission tomography (PET) A beta who were dichotomized (A beta+/A beta-) using previous cut-offs. We found a linear reduction in hippocampal volumes with epsilon 4 carriers possessing the smallest volumes, epsilon 3 carriers possessing intermediate volumes, and epsilon 2 carriers possessing the largest volumes. Moreover, AD and MCI epsilon 4 carriers possessed the smallest hippocampal volumes and control epsilon 2 carriers possessed the largest hippocampal volumes. Subjects with both APOE epsilon 4 and A beta positivity had the lowest hippocampal volumes when compared to A beta-epsilon 4 carriers, suggesting a synergistic relationship between APOE epsilon 4 and A beta. However, we found no hippocampal volume differences between APOE groups in healthy 14-year-old adolescents. Our findings suggest that the strongest neuroanatomic effect of APOE epsilon 4 on the hippocampus is observed in AD and groups most at risk of developing the disease, whereas hippocampi of old and young healthy individuals remain unaffected.
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| 8. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 9. |
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| 10. |
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| 11. |
- Winblad, B, et al.
(författare)
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Mild cognitive impairment--beyond controversies, towards a consensus: report of the International Working Group on Mild Cognitive Impairment.
- 2004
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Ingår i: Journal of internal medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 256:3, s. 240-6
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Forskningsöversikt (refereegranskat)abstract
- The First Key Symposium was held in Stockholm, Sweden, 2-5 September 2003. The aim of the symposium was to integrate clinical and epidemiological perspectives on the topic of Mild Cognitive Impairment (MCI). A multidisciplinary, international group of experts discussed the current status and future directions of MCI, with regard to clinical presentation, cognitive and functional assessment, and the role of neuroimaging, biomarkers and genetics. Agreement on new perspectives, as well as recommendations for management and future research were discussed by the international working group. The specific recommendations for the general MCI criteria include the following: (i) the person is neither normal nor demented; (ii) there is evidence of cognitive deterioration shown by either objectively measured decline over time and/or subjective report of decline by self and/or informant in conjunction with objective cognitive deficits; and (iii) activities of daily living are preserved and complex instrumental functions are either intact or minimally impaired.
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| 12. |
- Almkvist, O, et al.
(författare)
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Mild cognitive impairment -- An early stage of Alzheimer´s disease?
- 1998
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Ingår i: Journal of Neural Transmission. ; 53, s. 21-29
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Tidskriftsartikel (refereegranskat)abstract
- The hypothesis that mild cognitive impairment (MCI) represents an early stage of Alzheimer´s disease (AD) was investigated by reviewing recent research from three sources: asymptomatic and symptomatic individuals carrying mutations that cause AD; hospital
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| 13. |
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| 14. |
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| 15. |
- Caracciolo, B, et al.
(författare)
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The symptom of low mood in the prodromal stage of mild cognitive impairment and dementia : a cohort study of a community dwelling elderly population
- 2011
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Ingår i: Journal of Neurology, Neurosurgery and Psychiatry. - : BMJ. - 0022-3050 .- 1468-330X. ; 82:7, s. 788-793
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Tidskriftsartikel (refereegranskat)abstract
- Objective To investigate the symptom of low mood as a predictor of mild cognitive impairment (MCI) and its progression to dementia, taking into account: (i) MCI severity, (ii) time of assessment and (iii) interaction with other factors.Methods 764 cognitively healthy elderly subjects living in the community, from the Kungsholmen Project. Participants were assessed by direct interview to detect low mood. Subjects were then followed for 6 years to identify those who developed MCI. People with incident MCI were followed for a further 3 years to assess progression to dementia.Results People with low mood at baseline had a 2.7-fold (95% CI 1.9 to 3.7) increased risk of developing MCI at follow-up. The association was stronger for amnestic MCI (aMCI: HR 5.8; 95% CI 3.1 to 10.9) compared with global cognitive impairment (other cognitive impairment no dementia, oCIND: HR 2.2; 95% CI 1.5 to 3.3). ApoE-ε4 interacted with low mood in a synergistic fashion, increasing the risk of aMCI, while no interaction with psychiatric, vascular, frailty related or psychosocial factors was observed. Low mood at baseline, as opposed to low mood co-occurring with MCI, was associated with a 5.3-fold (95% CI 1.2 to 23.3) increased risk of progression to dementia in aMCI. In contrast, no association was found in oCIND.Conclusion Low mood was more strongly associated with aMCI than with global cognitive impairment. Progression towards dementia was predicted only by low mood manifest in the prodromal stage of MCI. These findings indicate that low mood is particularly prominent in the very early stages of cognitive decline.
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| 16. |
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| 17. |
- Gerritsen, L., et al.
(författare)
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The influence of negative life events on hippocampal and amygdala volumes in old age : a life-course perspective
- 2014
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Ingår i: Psychological Medicine. - 0033-2917 .- 1469-8978. ; 45:6, s. 1219-1228
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Psychosocial stress has been related to changes in the nervous system, with both adaptive and maladaptive consequences. The aim of this study was to examine the relationship of negative events experienced throughout the entire lifespan and hippocampal and amygdala volumes in older adults.METHOD: In 466 non-demented old adults (age range 60-96 years, 58% female), hippocampal and amygdala volumes were segmented using Freesurfer. Negative life events and the age at which these events occurred were assessed by means of a structured questionnaire. Using generalized linear models, hippocampal and amygdala volumes were estimated with life events as independent variables. The statistical analyses were adjusted for age, gender, intracranial volume, lifestyle factors, cardiovascular risk factors, depressive symptoms, and cognitive functioning.RESULTS: Total number of negative life events and of late-life events, but not of early-life, early-adulthood, or middle-adulthood events, was related to larger amygdala volume. There were interactions of early-life events with age and gender. Participants who reported two or more early-life events had significantly smaller amygdala and hippocampal volumes with increasing age. Furthermore, smaller hippocampal volume was found in men who reported two or more early-life events, but not in women.CONCLUSIONS: These results suggest that the effect of negative life events on the brain depends on the time when the events occurred, with the strongest effects observed during the critical time periods of early and late life.
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| 18. |
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| 19. |
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| 20. |
- Kivipelto, M, et al.
(författare)
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Homocysteine and holo-transcobalamin and the risk of dementia and Alzheimers disease : a prospective study.
- 2009
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Ingår i: European journal of neurology : the official journal of the European Federation of Neurological Societies. - : Wiley. - 1468-1331 .- 1351-5101. ; 16:7, s. 808-813
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Elevated total homocysteine (tHcy) levels may be caused by vitamin B12 deficiency and are linked to Alzheimers disease (AD) in some studies, although the evidence is mixed. Another marker of vitamin B12 deficiency, holo-transcobalamin (holo-TC), has not been studied in a prospective setting. OBJECTIVE: To investigate the association between tHcy and holo-TC and the subsequent development of dementia and AD in a prospective study. METHODS: A sub-sample of 228 non-demented subjects was taken from the Kungsholmen Project, a population-based longitudinal study amongst persons 75+ years. tHcy and holo-TC were analysed at baseline. RESULTS: Increasing tHcy levels were related to an increased risk of dementia (n = 83) and AD (n = 61) after a mean follow-up time of 6.7 years. Persons with high tHcy (the fourth quartile) had more than twice as high a risk of developing AD than persons with low tHcy, even after adjusting for confounding or mediating factors. The third quartile of holo-TC was associated with a reduced risk of AD, after adjusting for Hcy and other confounders. CONCLUSIONS: These results suggest that Hcy is involved in the development of dementia and AD. The role of holo-TC was less clear and this marker needs to be studied further.
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| 21. |
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| 22. |
- Nilson, L, et al.
(författare)
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Trail making test in chronic toxic encephalopathy: Performance and discriminative potential
- 1999
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Ingår i: CLINICAL NEUROPSYCHOLOGIST. - : SWETS ZEITLINGER PUBLISHERS. - 0920-1637. ; 13:3, s. 314-327
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to examine the influence of chronic toxic encephalopathy (CTE) on Trail Making Test (TMT) performance, with special focus on the discriminative potential of this test. We assessed TMT performance in patients diagnosed with
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Tufveson, G, et al.
(författare)
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Organ transplantation in Göteborg with particular reference to kidney transplantation.
- 1993
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Ingår i: Clinical transplants. - 0890-9016. ; , s. 243-51
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Tidskriftsartikel (refereegranskat)abstract
- The limiting factor in organ transplantation is the availability of organs. Continuing work to improve the public's willingness to donate organs and inspire hospital staff to collaborate in organ procurement is essential. Identification of patients who will not benefit from transplantation can also increase the availability of organs. Grafts may also be saved by identification and appropriate treatment of recurrent renal disease. Xenotransplantation may eventually solve the problem, but major obstacles remain. Meanwhile, work in this field may help to clarify mechanisms of rejection. New immunosuppressive drugs may improve graft survival and reduce the incidence and progression of chronic rejection.
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| 27. |
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| 28. |
- Berger, AK, et al.
(författare)
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The occurrence of depressive symptoms in the preclinical phase of AD - A population-based study
- 1999
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Ingår i: NEUROLOGY. - : LIPPINCOTT WILLIAMS & WILKINS. - 0028-3878. ; 53:9, s. 1998-2002
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To examine preclinical depressive symptoms 3 years before the diagnosis of AD. Methods: The authors compared incident AD patients and nondemented individuals in terms of baseline mood- and motivation-related symptoms of depression, and assesse
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| 29. |
- 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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| 30. |
- 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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| 31. |
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| 32. |
- Bäckman, B, et al.
(författare)
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The absence of correlations between a clinical classification and ultrastructural findings in amelogenesis imperfecta.
- 1993
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Ingår i: Acta odontologica Scandinavica. - 0001-6357. ; 51:2, s. 79-89
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Tidskriftsartikel (refereegranskat)abstract
- This study was performed to examine whether a clinical classification of different phenotypes of amelogenesis imperfecta could be discernible at the ultrastructural level. Seventeen primary teeth from 16 children with hypomineralization, hypomaturation, or hypoplastic variants of the disease were collected for histologic studies of the enamel by means of polarized light microscopy, scanning electron microscopy (SEM), and secondary ion mass spectrometry (SIMS). Polarization microscopy showed that the enamel was hypomineralized; in six teeth a wavy configuration of the enamel prisms also appeared. Three histomorphologic main types could be discerned. In 10 of the teeth extensive hypomineralization of the bulk of the enamel was found. One tooth had an unusually thick enamel with only a thin normally mineralized surface layer. SIMS images showed less pronounced signals from Ca2+ and Na+ but with stronger signals from Cl- and CN-, representing the organic component of enamel. The SEM images showed an irregular prism pattern with marked interprismatic areas. Irrespective of the clinical appearance or the hereditary pattern the main findings were hypomineralized enamel with or without wavy bands. Neither of the analytical methods used in this paper distinguishes between the clinical phenotypes of amelogenesis imperfecta.
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| 33. |
- Bäckman, Jonas, et al.
(författare)
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Evaluation of filter parameters from direct observations of metal flow in aluminium castings
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The potential in mechanical properties for aluminium casting alloys are in many casting processes not fully utilised. One reason is the defect formation in the casting process. The defects could be oxide films, introduced during mould filling, and pore formation. This investigation has been focused on how the gravity mould filling could be controlled by using filter in the ingate system and the how the pressure drop over the filter can be evaluated.In gravity casting the metal flow velocity usually reaches several metres per second. Direct observations have shown that filters improve mould filling during casting. Additionally, filters cause a pressure loss, which decreases the speed of the metal and gives a smoother filling.In this paper, mould-filling experiments were recorded directly by a video camera through a transparent ceramic glass. Two different types of ceramic filters, reticulated foam filters and extruded filters with 10, 20 and 30 pores per inch and 100 and 300 cells per square inch respectively, were investigated. The influence of active filter area and filter size on the flow reduction has also been investigated. As the casting temperature influences the viscosity of the liquid metal, the pressure loss over the filter was evaluated at various temperatures.Using parameters for calculating flow loss caused by filter can help when designing ingate systems containing filters. The filter parameters can be used in two ways, either to control the speed of the metal or to design the active filter area in a way that the melt flux is not affected. Proper parameters are also important for computer simulations of mould filling. The parameters evaluated from these experiments have been used in computer simulation of mould filling and the results have been compared with experiments.
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| 34. |
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| 35. |
- Bäckman, Jonas, et al.
(författare)
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Influence of filter on the mould filling of aluminium melts in vacuum-sealded moulds
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The influence of filters on the mould filling behaviour has been investigated by direct observation experiments. The ingate system was moulded in a vertically parted vacuumsealed sand mould. How the filter in general, and how different filter locations, filter coarseness, active filter area and filter length influence the mould filling has been clarified. The direct observation method is a very powerful way to learn how different ingate system designs and filter conditions affect the mould filling. During mould filling the melt behaviour was recorded by a video camera through a glass wall, from which still images are presented. The general effect of filters is a better filling of the ingate system prior to the filter, and a reduction of the melt velocity, which in turn give smoother filling after the filter. Initially, the downsprue is completely filled at an early stage of the filling due to the back-pressure from the filter. The back-pressure is built up as a result of friction in the filter. An early filling of the downsprue prevents the melt from entraining oxide films or air inclusions. Secondly, the filling of the runner is improved by the use of a filter. The better filling of the runner is mainly an effect of the decreased velocity of the melt. The reduction of the melt velocity results in reduced surface turbulence and less splashing. Reduced surface turbulence and splashing of the melt prevents incorporation of oxide films and air in the melt, which has an overall beneficial effect on the quality of the castings. The location of the filter has been found to play an important role in the filling soundness.
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| 36. |
- Bäckman, Jonas, et al.
(författare)
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Influence of ingate system design on mechanical properties for a cast A1-10Si-0.38Mg alloy
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this work the influence of the ingate system design on the as-cast mechanical properties of an Al-10Si-0.38Mg alloy have been clarified. The Weibull distribution has been seen to describe the spread in mechanical properties very well. The Weibull modulus has therefore been used as a measure of the soundness of an ingate system. Different ingate systems were investigated, including: expanding systems, pressurised systems, systems with and without filter, systems with different designs of the connection between the downsprue and the runner, and systems with and without an additional pocket at the end of the runner. The modification index of the microstructure was also measured in order to investigate if the spread in data is more dependent on the modification index than on the ingate system design. The results showed that a high Weibull modulus is more dependent on the ingate system design than on the modification index of the microstructure. The ultimate tensile strength was not significantly affected by the ingate system design, while the fracture elongation seemed to be more dependent on the melt quality than on the ingate system design. The Weibull modulus indicates that expanding systems are better than pressurised systems, and that the use of a filter in the runner is very beneficial. An additional pocket at the end of the runner has no beneficial effect when using a filter. The connection between the downsprue and the runner should have a rounded bend and the change in cross-section between the downsprue and the runner should be chamfered and not sharp.
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| 37. |
- Bäckman, Jonas, et al.
(författare)
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Mould filling observations of aluminium melts in vacuum-sealed sand moulds
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In order to clarify how the ingate system design influences the mould filling behaviour of aluminium melts in vertically parted vacuum-sealed moulds, some direct observation experiments have been made. A detailed study of how the design of each component in the ingate system affects the mould filling behaviour has been made. The effect of different designs on downsprue-runner connections, runners and end-wall of the runners as well as the effect of wall friction was investigated. The mould filling process was studied through a glass wall and recorded by a video camera. Still images from the videotape are presented and evaluated. The direct observation method has been found to be a very powerful way to follow the melt behaviour during mould filling. To ensure a good filling of the downsprue the melt level in the pouring basin has to be above a certain level from the time when the stopper is removed and during the whole filling sequence. A perpendicular connection between the downsprue and the runner gives a larger flow loss than a rounded type. Due to the larger flow loss the perpendicular connection results in an earlier filling of the downsprue. A tapered runner results in almost simultaneous filling of the specimens compared to a runner with no tapering. On the other hand the tapered runner gives a more divergent melt front which increase the free melt surfaces in contact with air. An additional pocket at the end of the runner has a beneficial effect on the mould filling. A sharp angled pocket is better than a more rounded type. Decreasing the wall thickness increases the flow loss due to wall friction, and causes more significant heat losses.
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| 38. |
- Bäckman, Jonas, et al.
(författare)
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Potential for improved mechanical properties in cast aluminium alloys
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this work is to investigate the potential to improve the mechanical properties of some aluminium alloys, in order to obtain castings with optimum properties. Experiments have been made with pure aluminium, aluminium alloyed with 1% Si and 0,9% Mg and four aluminium cast alloys with 7-12% Si and various amounts of iron, magnesium, copper and manganese. To achieve the best possible solidification, gradient solidification technology of tensile specimen has been used, in order to explore the limits of the mechanical properties in relation to the microstructure. The experiments show that it is not possible to obtain good fracture toughness in alloys with a high iron content. The results also show that many of the aluminium alloys frequently used today are not processed in a way that allows optimal mechanical properties to be achieved. The alloys with a maximum of 0,4% Fe can give 10-23% fracture elongation, depending on other alloying elements such as Si, Mg and Cu. For these alloys it is worthwhile to improve the melt treatment and the casting process to obtain properties close to, or even better than can be achieved in other manufacturing processes. The experiments have given results for both columnar and equiaxed primary solidification structures.
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| 39. |
- Bäckman, Karin, et al.
(författare)
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Deep venous thrombosis : A new task for primary health care - A randomised economic study of outpatient and inpatient treatment
- 2004
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Ingår i: Scandinavian Journal of Primary Health Care. - : Informa UK Limited. - 0281-3432 .- 1502-7724. ; 22:1, s. 44-49
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Tidskriftsartikel (refereegranskat)abstract
- Objective - A health economic evaluation of two alternative treatment settings, inpatient care and outpatient care, for acute deep venous thrombosis. Design - A randomised multicentre trial in a defined population in regular clinical practice. Setting - Hospitals and related health care centres in the Jönköping county council in Sweden. Interventions - Patients were randomised to either an inpatient strategy (n = 66) or an outpatient strategy (n = 65) using low-molecular-weight heparin, dalteparin, administered subcutaneously once daily and adjusted for body weight. Subjects - Of 224 eligible patients, 131 entered the trial and 124 completed the economic part of the study. Main outcome measures - Direct medical and direct non-medical costs during a 3-month period. Results - Total direct costs were higher for those in the inpatient strategy group, i.e. Swedish Crowns (SEK) 16 400 per patient (Euro 1899) compared to SEK 12 100 per patient (Euro 1405) in the outpatient strategy group (p < 0.001). More patients in the outpatient group received assistance when they returned home. Few patients in either group reported sick leave. There was no difference in total number of days between the two groups. Conclusions - Total direct costs were significantly lower for the outpatient treatment strategy for deep venous thrombosis compared to the inpatient treatment strategy. No significant difference in health impact could be detected. Deep venous thrombosis can to a greater extent than previously be treated in primary care, safely, at a lower cost, and in accordance with patient preferences.
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| 40. |
- Bäckman, Lars, et al.
(författare)
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Brain regions associated with episodic retrieval in normal aging and Alzheimer's disease
- 1999
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Ingår i: NEUROLOGY. - : LIPPINCOTT WILLIAMS & WILKINS. - 0028-3878. ; 52:9, s. 1861-1870
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To examine patterns of brain activation during verbal episodic retrieval in normal elderly subjects and patients in an early phase of AD. Background: It is established that 1) a profound episodic memory impairment is a cardinal symptom of AD;
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| 41. |
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| 42. |
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| 43. |
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| 44. |
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| 45. |
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| 46. |
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| 48. |
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| 49. |
- Bäckström, Mattias, et al.
(författare)
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Mobilisation of heavy metals by deicing salts in a roadside environment
- 2004
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 38:3, s. 720-732
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Tidskriftsartikel (refereegranskat)abstract
- The seasonal variations of some selected heavy metals (Cd, Cu, Pb and Zn) and principal anions in soil solutions were monitored as a function of distance from the road at two field sites in Sweden. During the winter, the conductivity, concentrations of dissolved sodium and chloride increased dramatically due to the application of deicing agents (i.e. NaCl). Due to ion exchange, the pH decreased one unit in the soil solutions, whereas the concentrations of total organic carbon decreased due to coagulation and/or sorption to stationary solids. The heavy metal concentrations increased during the winter, but through different mechanisms. Cadmium concentrations in the aqueous phase increased as a response to ion exchange, possibly also enhanced by the formation of chloride complexes. Similarly, the concentrations of zinc increased, due to ion exchange, with calcium and protons. The mechanisms of mobilisation for copper and lead were not that clear probably due to association with coagulated or sorbed organic matter in combination with colloid dispersion.
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| 50. |
- Degl´Innocenti, A, et al.
(författare)
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Source memory in major depression
- 1999
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Ingår i: Journal of Affective Disorders. ; 54, s. 205-209
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Tidskriftsartikel (refereegranskat)abstract
- Background: Research demonstrating episodic memory deficits in clinical depression has dealt with item memory exclusively. The present research sought to determine whether memory for source is differentially affected by depression. Methods: Patients with
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