| 1. |
- Nordström, Anna, et al.
(författare)
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A 3-year longitudinal study of the effect of physical activity on the accrual of bone mineral density in healthy adolescent males.
- 2003
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Ingår i: Calcified Tissue International. - : Springer Science and Business Media LLC. - 0171-967X .- 1432-0827. ; 73:2, s. 108-114
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Tidskriftsartikel (refereegranskat)abstract
- It has previously been suggested that physical activity predominantly influences the accumulation of bone density before puberty. The purpose of the present study was to examine the effect of physical activity on the accumulation of bone mass in male athletes between 16 and 19 years of age. The cohort studied consisted of 12 badminton players (aged 16.1 +/- 0.5), 20 ice hockey players (aged 16.1 +/- 0.5), and 24 age-matched controls (aged 16.1 +/- 0.6). The bone mineral density (BMD, g/cm2) of the total body, spine, dominant and nondominant humerus, head and femoral neck was measured twice with a 3-year interval by dual energy X-ray absorptiometry (DXA). In addition, at the femoral neck, volumetric bone mineral density (vBMD, mg/cm3) was estimated. At baseline, the athletes as a whole group had significantly higher BMD at the total body (P = 0.03), dominant (P = 0.006) and nondominant humerus (P = 0.009) and femoral neck (P = 0.007) compared to the controls. At the 3-year followup, the athletes had significantly higher BMD at all sites (total body; P = 0.003, spine; P = 0.02, dominant humerus; P = 0.001, nondominant humerus; P = < 0.001, femoral neck; P = 0.001) except for the head (P = 0.91) compared with controls. The athletes also had higher vBMD at the femoral neck compared with the controls (P = 0.01). Furthermore, to be an athlete was found to be independently associated with a higher increase in nondominant humerus BMD (beta = 0.24; P < 0.05) and femoral neck BMD (beta = 0.30; P < 0.05) compared with the controls, during the study period. In summary, these results suggests that it is possible to achieve continuous gains in bone mass in sites exposed to osteogenic stimulation after puberty in males by engaging in weight-bearing physical activity.
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| 2. |
- Nordström, Anna, 1973-
(författare)
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Bone mass and physical activity
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Abstract Weak and osteoporotic bones in old age are an increasing cause of mortality and painful physical impairment of the elderly, especially in the western world. Bone mineral accrual during childhood and adolescence is thought to play a vital role in preventing osteoporosis. Identifying and optimizing the factors influencing peak bone mass is thus important for the prevention of osteoporosis and related fractures. A main aim of this thesis was to investigate the potential effects of various types of weight-bearing physical activity on bone accretion in young males just out of puberty. The results from our subgroups of athletes consisting of badminton, ice hockey, and soccer players suggest that weight-bearing physical activity gives rise to regional specific bone response that is determined by the degree of impact of the activity in areas subject to mechanical loading (papers I–IV). In summary, the bone is sensitive to loading after puberty in males, and important bone mass gains can be achieved by proper amount and type of exercise. Another aim of this thesis was to studythe effect of detraining on weight-bearing and non-weight-bearing bone in a cohort of adolescent males who participated in ice hockey and soccer training. Our results indicate that exercise-induced bone mineral density benefits decline, predominantly in weight-bearing bones, after retirement from an active sports career (papers II–IV). High bone density stemming from physical loading might be at least partly preserved even by reduced physical activity at nonweight-bearing sites after about three years of reduced activity (III, IV). A final aim was to follow prospectively the development of BMD during years of reduced activity in former male athletes, and evaluate whether exercise during adolescence could be associated with fewer fractures in old age. We found fewer fragility fractures in a cohort of 400 former athletes compared to in 800 age-matched controls. Thus, high bone density stemming from previous weight-bearing physical activity may reduce the risk of sustaining fragility fractures in the elderly. Key words: physical activity, peak bone mineral density, males.
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| 3. |
- Nordström, Anna, 1973-, et al.
(författare)
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Interleukin-6 promoter polymorphism is associated with bone quality assessed by calcaneus ultrasound and previous fractures in a cohort of 75-year-old women.
- 2004
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Ingår i: Osteoporosis international. - : Springer Science and Business Media LLC. - 0937-941X .- 1433-2965. ; 15:10, s. 820-6
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Tidskriftsartikel (refereegranskat)abstract
- Interleukin 6 (IL-6) is a multifunctional cytokine and a potent stimulator of bone resorption and has been implicated in the pathogenesis of osteoporosis in postmenopausal women. The aim of this study was to investigate if a functional IL-6 promoter polymorphism (-174) was related to bone mass and fractures in a cohort consisting of 964 postmenopausal Caucasian women aged 75 years. Bone mineral density (BMD; g/cm2) of the femoral neck, lumbar spine and total body was measured using dual energy X-ray absorptiometry (DXA). Quantitative ultrasound (QUS) was also measured in the calcaneus and quantified as speed of sound (SOS; m/s), broadband ultrasound attenuation (BUA; dB/MHz), and stiffness index (SI). IL-6 genotypes was determined by restriction fragment length polymorphism (RFLP) using the restriction enzyme NlaIII. The frequencies of the different IL-6 genotypes were 27.5% (GG), 47.9% (GC), 24.6% (CC). The IL-6 polymorphism (presence of G) was independently related to a lower stiffness (beta=-0.07; P=0.03) and BUA (beta=-0.08; P=0.02), but not to BMD at any site measured by DXA. In the cohort, 420 subjects (44%) reported at least one fracture during their lifetime, and 349 (36%) reported at least one fracture after the age of 50. Using binary logistic regression, the IL-6 polymorphism (presence of G) was significantly related to an increased risk of a previous fracture during life (odds ratio 1.46, 95% CI 1.08-1.97) and to an increased risk of a fracture occurring after 50 years of age (odds ratio 1.37, 95% CI 1.004-1.88). The risk was further increased for fractures grouped as osteoporotic fractures (odds ratio 1.67, 95% CI 1.14-2.45), including forearm fractures (odds ratio 1.59, 95% CI 1.05-2.40). In conclusion, presence of G allele in the IL-6 promoter polymorphism at position -174 is independently related to previous fractures in postmenopausal women. This association may be related primarily to an altered bone quality identified by QUS and not a lower bone mass. This is also the first demonstration of association of IL-6 gene polymorphism to calcaneal QUS.
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| 4. |
- Nordström, Anna, et al.
(författare)
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Rapid loss of bone mineral density of the femoral neck after cessation of ice hockey training: a 6-year longitudinal study in males.
- 2003
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Ingår i: Journal of Bone and Mineral Research. - : Wiley. - 0884-0431 .- 1523-4681. ; 18:11, s. 1964-1969
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the effect of training and reduced training on BMD in young ice hockey players during 6 years of follow-up. We found BMD gains in the femoral neck in the ice hockey group compared with controls. However, these gains were lost with reduced activity after cessation of career. INTRODUCTION: It has been suggested that increasing bone mass by intense physical activity during childhood and adolescence may decrease the risk of osteoporosis later in life. MATERIALS AND METHODS: In this longitudinal study, 43 ice hockey players (16.7 +/- 0.6 years) and 25 control subjects (16.8 +/- 0.3 years) were studied at baseline and after a mean period of 30 and 70 months. The groups did not differ in weight or height. Bone mineral density (BMD; g/cm2) was measured for total body, femoral neck, and spine using DXA. Volumetric BMD (vBMD; mg/cm3) of the femoral neck was estimated. RESULTS: The ice hockey players were found to have gained significantly more femoral neck BMD than controls (0.07 versus 0.03 g/cm2, p = 0.04) and to have gained femoral neck vBMD, whereas the controls did not (16 versus 0 mg/cm3, p = 0.049) between baseline and the first follow-up. At the first follow-up, the ice hockey players were found to have significantly higher BMD at the femoral neck and total body versus controls (p < 0.05). Between the first and second follow-ups, 21 ice hockey players stopped their active sports career. During this time period, these subjects lost significantly more femoral neck BMD (0.10 versus 0.02 g/cm2, p < 0.001) and femoral neck vBMD (38 versus 4 mg/cm3, p < 0.001) compared with the 22 ice hockey players who continued training. The former ice hockey players also lost significantly more neck vBMD (38 versus 14 mg/cm3, p = 0.009) compared with the controls during the same period. At the second follow-up, only the 22 ice hockey players who had continued their training were found to have significantly higher BMD at the femoral neck (p = 0.01), total body (p = 0.04), and spine (p = 0.02) compared with the controls. The former athletes were found to have intermediate BMD at all sites. CONCLUSION: In summary, we have demonstrated fast BMD loss at the femoral neck after decreased physical activity in young men. We conclude that ice hockey training during childhood and adolescence may not prevent the development of osteoporosis of the femoral neck later in life if the activity is not maintained.
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| 5. |
- Bergqvist, Lars, 1976-, et al.
(författare)
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Magnetic and electronic structure of (Ga1-xMnx)As
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:20, s. 205201-
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Tidskriftsartikel (refereegranskat)abstract
- We present theoretical calculations of the magnetic and electronic structure of Mn-doped GaAs (in the zinc-blende structure). The magnetic properties are shown to be very sensitive to structural defects, in particular, As antisite defects and Mn at interstitial positions. Only when considering such defects can the experimental magnetic moments be reproduced by first-principles theory. We present a simple model for understanding the connection between the magnetic ordering and the As antisites, and the way in which the defects help to stabilize a partial disordered local-moment state. The connection between the energetics of the Mn substitution and the As antisite concentration is also analyzed. In addition, we compare the calculated magnetic properties and electronic structures of Mn situated on substitutional sites (Mn replacing a Ga atom) and on interstitial sites, where in agreement with observations the interstitial site is found to be less favorable. Finally, combining our first-principles calculations of the spin-wave excitation energies with a classical Heisenberg Hamiltonian we have calculated interatomic exchange interactions, and using Monte Carlo simulations we present theoretical values of the critical temperature as a function of Mn concentration.
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| 6. |
- Diaz-Parejo, P, et al.
(författare)
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Cerebral energy metabolism during transient hyperglycemia in patients with severe brain trauma
- 2003
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Ingår i: Intensive Care Medicine. - : Springer Science and Business Media LLC. - 0342-4642 .- 1432-1238. ; 29:4, s. 544-550
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To study whether transient hyperglycemia adversely affects cerebral energy metabolism in patients with severe traumatic brain lesions. Design and setting: Prospective, nonrandomized study in the neurosurgical intensive care unit of a university hospital. Patients: 108 patients treated for severe traumatic brain lesions. Interventions: All patients were treated according to neurosurgical intensive care routine including monitoring of, intracranial pressure. One microdialysis catheter was inserted via a burr hole frontally to that used for the intraventricular catheter ("better" position). In patients with focal lesions one or more catheters were inserted into cerebral cortex surrounding an evacuated focal contusion or underlying an evacuated hematoma ("worse" position). Perfusion rate was 0.3 mul/min and samples were taken every. 30 or 60 min. The levels of glucose, pyruvate, lactate, glutamate, and glycerol were analyzed and displayed bedside. Measurements and results: There were 18 episodes of moderate (12-15 mmol/1) and 6 episodes of pronounced (>15 mmol/1) hyperglycemia. Moderate hyperglycemia did not change intracerebral levels of lactate, pyruvate, glutamate, glycerol, or lactate/pyruvate ratio. Lactate concentrations increased during pronounced hyperglycemia. Pronounced cerebral lactic acidosis and a moderate increase in interstitial glycerol concentration indicating cell membrane degradation was observed in a single patient with pronounced, long-lasting hyperglycemia. Conclusions: Cerebral energy metabolism was affected by transient hyperglycemia only at blood glucose concentration above 15 mmol/l as shown by a moderate increase in interstitial lactate level.
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| 7. |
- Holmström, Erik, et al.
(författare)
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On the sharpness of the interfaces in metallic multilayers
- 2004
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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. - 0027-8424 .- 1091-6490. ; 101:14, s. 4742-4745
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Tidskriftsartikel (refereegranskat)abstract
- We show that the three most relevant magnetic properties (magnetic moment, critical temperature, and interlayer exchange coupling) of metallic multilayers can be reproduced with good accuracy by first principles theory, provided that the picture of atomically sharp interfaces is abandoned and one allows instead for both interface alloying and interface roughness. The interface of a metallic multilayer (exemplified by the Fe/V system) is demonstrated to, at best, have interdiffusion essentially over two to three atomic layers on each side of the interface. Our conclusions are the result of combining experimental work with theoretical modeling, and we argue that this approach is the best avenue to obtain accurate information about the interface quality of metallic multilayers.
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| 8. |
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| 9. |
- Hörlin, Nils-Erik, et al.
(författare)
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A 3-D hierarchical Fe formulation of Biot's equations for elasto-acoustic modelling of porous media
- 2001
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 245:4, s. 633-652
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Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional hierarchical finite element formulation of Biot's equation for low frequency elasto-acoustic wave propagation in fluid saturated porous media based on a weak formulation with fluid displacement and solid displacement as dependent variables is presented. A global error measure for evaluation of the convergence is proposed. Numerical simulations of an air saturated polyurethane foam material show faster convergence for the hierarchical extensions than for linear and quadratic serendipity finite element mesh refinement extensions.
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| 10. |
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