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- Karlen, A, et al.
(författare)
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Nogo receptor 1 regulates formation of lasting memories
- 2009
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490. ; 106:48, s. 20476-20481
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Tidskriftsartikel (refereegranskat)abstract
- Formation of lasting memories is believed to rely on structural alterations at the synaptic level. We had found that increased neuronal activity down-regulates Nogo receptor-1 (NgR1) in brain regions linked to memory formation and storage, and postulated this to be required for formation of lasting memories. We now show that mice with inducible overexpression of NgR1 in forebrain neurons have normal long-term potentiation and normal 24-h memory, but severely impaired month-long memory in both passive avoidance and swim maze tests. Blocking transgene expression normalizes these memory impairments. Nogo, Lingo-1, Troy, endogenous NgR1, and BDNF mRNA expression levels were not altered by transgene expression, suggesting that the impaired ability to form lasting memories is directly coupled to inability to down-regulate NgR1. Regulation of NgR1 may therefore serve as a key regulator of memory consolidation. Understanding the molecular underpinnings of synaptic rearrangements that carry lasting memories may facilitate development of treatments for memory dysfunction.
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| 8. |
- Edman, K A Paul, et al.
(författare)
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Determinants of force rise time during isometric contraction of frog muscle fibres
- 2007
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Ingår i: Journal of Physiology. - : Wiley. - 1469-7793 .- 0022-3751. ; 580:3, s. 1007-1019
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Tidskriftsartikel (refereegranskat)abstract
- Force-velocity (F-V) relationships were determined for single frog muscle fibres during the rise of tetanic contraction. F-V curves obtained using isotonic shortening early in a tetanic contraction were different from those obtained at equivalent times with isovelocity shortening, apparently because changing activation early in the contraction leads, in isovelocity experiments, to changing force and changing series elastic extension. F-V curves obtained with isotonic and with isovelocity shortening are similar if the shortening velocity in the isovelocity trials is corrected for series elastic extension. There is a progressive shift in the scaling of force-velocity curves along the force axis during the course of the tetanic rise, reflecting increasing fibre activation. The time taken for F-V curves to reach the steady-state position was quite variable, ranging from about 50 ms after the onset of contraction (1-3 degrees C) to well over 100 ms in different fibres. The muscle force at a fixed, moderately high shortening velocity relative to the force at this velocity during the tetanic plateau was taken as a measure of muscle activation. The reference velocity used was 60% of the maximum shortening velocity (V-max) at the tetanic plateau. The estimated value of the fractional activation at 40 ms after the onset of contraction was used as a measure of the rate of activation. The rate of rise of isometric tension in different fibres was correlated with the rate of fibre activation and with V-max during the plateau of the tetanus. Together differences in rate of activation and in V-max accounted for 60-80% of the fibre-to-fibre variability in the rate of rise of isometric tension, depending on the measure of the force rise time used. There was not a significant correlation between the rate of fibre activation and Vmax. The steady-state F-V characteristics and the rate at which these characteristics are achieved early in contraction are seemingly independent. A simulation study based on F-V properties and series compliance in frog muscle fibres indicates that if muscle activation were instantaneous, the time taken for force to rise to 50% of the plateau value would be about 60% shorter than that actually measured from living fibres. Thus about 60% of the force rise time is a consequence of the time course of activation processes and about 40% represents time taken to stretch series compliance by activated contractile material.
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- Fochsen, G, et al.
(författare)
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Predictors of leaving nursing care: a longitudinal study among Swedish nursing personnel.
- 2006
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Ingår i: Occupational and environmental medicine. - : BMJ. - 1470-7926 .- 1351-0711. ; 63:3, s. 198-201
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Despite extensive research on turnover among nursing personnel very little is known about the impact of physical workload and health on leaving. The aim of this study was to find predictors for leaving nursing care with special reference to physical working conditions and musculoskeletal problems. METHODS: This study is based on longitudinal data from a survey of nursing personnel who were employed at various county hospitals in Sweden from 1992-95. A self administrated follow up questionnaire was used to identify their present position in the labour market. The response rate was 73% (n = 1095). RESULTS: The results showed that nursing personnel reporting musculoskeletal problems of the neck/shoulder or knees and those who had limited use of transfer devices were more likely to leave nursing care. CONCLUSIONS: The study highlights the importance of taking musculoskeletal problems and use of transfer devices into consideration in order to retain nursing personnel.
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