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- Abbott, R., et al.
(författare)
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Hybridization and speciation
- 2013
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 26:2, s. 229-246
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Forskningsöversikt (refereegranskat)abstract
- Hybridization has many and varied impacts on the process of speciation. Hybridization may slow or reverse differentiation by allowing gene flow and recombination. It may accelerate speciation via adaptive introgression or cause near-instantaneous speciation by allopolyploidization. It may have multiple effects at different stages and in different spatial contexts within a single speciation event. We offer a perspective on the context and evolutionary significance of hybridization during speciation, highlighting issues of current interest and debate. In secondary contact zones, it is uncertain if barriers to gene flow will be strengthened or broken down due to recombination and gene flow. Theory and empirical evidence suggest the latter is more likely, except within and around strongly selected genomic regions. Hybridization may contribute to speciation through the formation of new hybrid taxa, whereas introgression of a few loci may promote adaptive divergence and so facilitate speciation. Gene regulatory networks, epigenetic effects and the evolution of selfish genetic material in the genome suggest that the Dobzhansky-Muller model of hybrid incompatibilities requires a broader interpretation. Finally, although the incidence of reinforcement remains uncertain, this and other interactions in areas of sympatry may have knock-on effects on speciation both within and outside regions of hybridization.
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| 2. |
- Camara-Costa, H., et al.
(författare)
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Quality of survival and cognitive performance in children treated for medulloblastoma in the PNET 4 randomized controlled trial
- 2017
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Ingår i: Neuro-Oncology Practice. - : Oxford University Press (OUP). - 2054-2577 .- 2054-2585. ; 4:3, s. 161-170
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Tidskriftsartikel (refereegranskat)abstract
- Background. The relationship between direct assessments of cognitive performance and questionnaires assessing quality of survival (QoS) is reported to be weak-to-nonexistent. Conversely, the associations between questionnaires evaluating distinct domains of QoS tend to be strong. This pattern remains understudied. Methods. In the HIT-SIOP PNET4 randomized controlled trial, cognitive assessments, including Full Scale, Verbal and Performance IQ, Working Memory, and Processing Speed, were undertaken in 137 survivors of standard-risk medulloblastoma from 4 European countries. QoS questionnaires, including self-reports and/or parent reports of the Behavior Rating Inventory of Executive Function (BRIEF), the Health Utilities Index, the Strengths and Difficulties Questionnaire, and the Pediatric Quality of Life Inventory, were completed for 151 survivors. Correlations among direct cognitive assessments, QoS questionnaires, and clinical data were examined in participants with both assessments available (n = 86). Results. Correlations between direct measures of cognitive performance and QoS questionnaires were weak, except for moderate correlations between the BRIEF Metacognition Index (parent report) and working memory (r = .32) and between health status (self-report) and cognitive outcomes (r = .35-.44). Correlations among QoS questionnaires were moderate to strong both for parent and self-report (r = .39-.76). Principal Component Analysis demonstrated that questionnaires and cognitive assessments loaded on 2 separate factors. Conclusions. We hypothesize that the strong correlations among QoS questionnaires is partially attributable to the positive/negative polarity of all questions on the questionnaires, coupled with the relative absence of diseasespecific questions. These factors may be influenced by respondents' personality and emotional characteristics, unlike direct assessments of cognitive functioning, and should be taken into account in clinical trials.
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- Blomqvist, G, et al.
(författare)
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Effect of acute hyperketonemia on the cerebral uptake of ketone bodies in nondiabetic subjects and IDDM patients
- 2002
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Ingår i: American journal of physiology. Endocrinology and metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 283:1, s. E20-E28
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Tidskriftsartikel (refereegranskat)abstract
- Using R-β-[1-11C]hydroxybutyrate and positron emission tomography, we studied the effect of acute hyperketonemia (range 0.7–1.7 μmol/ml) on cerebral ketone body utilization in six nondiabetic subjects and six insulin-dependent diabetes mellitus (IDDM) patients with average metabolic control (HbA1c = 8.1 ± 1.7%). An infusion of unlabeled R-β-hydroxybutyrate was started 1 h before the bolus injection of R-β-[1-11C]hydroxybutyrate. The time course of the radioactivity in the brain was measured during 10 min. For both groups, the utilization rate of ketone bodies was found to increase nearly proportionally with the plasma concentration of ketone bodies (1.0 ± 0.3 μmol/ml for nondiabetic subjects and 1.3 ± 0.3 μmol/ml for IDDM patients). No transport of ketone bodies from the brain could be detected. This result, together with a recent study of the tissue concentration of R-β-hydroxybutyrate in the brain by magnetic resonance spectroscopy, indicate that, also at acute hyperketonemia, the rate-limiting step for ketone body utilization is the transport into the brain. No significant difference in transport and utilization of ketone bodies could be detected between the nondiabetic subjects and the IDDM patients.
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