| 1. |
- Jönsson, K. Ingemar, 1959-, et al.
(författare)
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Radiation tolerance in the eutardigrade Richtersius coronifer
- 2005
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Ingår i: International Journal of Radiation Biology. - : Taylor & Francis. - 0955-3002 .- 1362-3095. ; 81:9, s. 649-656
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Tardigrades have a reputation of being extremely tolerant to extreme environmental conditions including tolerance to ionizing radiation while in a desiccated, anhydrobiotic state. However, the evidence for radio-tolerance in tardigrades is based on only one previous report, and there is an obvious need for complementary studies. In this paper we report an investigation on radio-tolerance in desiccated and hydrated specimens of the eutardigrade Richtersius coronifer.MATERIALS AND METHODS: Groups of 30 - 50 tardigrades were exposed to gamma-radiation at doses between 1.0 - 9.0 (anhydrobiotic animals) or 0.5 - 5.0 (hydrated animals) kGy and the animals were followed until all were dead. Radiation tolerance of both desiccated and hydrated tardigrades was studied.RESULTS: Both desiccated and hydrated animals irradiated with 0.5 and 1 kGy did not deviate in survival from the control groups. Animals from all exposed groups underwent their moulting and egg production cycle, but at decreasing frequency for doses above 1 kGy. No eggs laid by irradiated animals hatched, while eggs laid by controls did so.CONCLUSION: Our study suggests that radiation tolerance in tardigrades is not due to biochemical protectants connected with the desiccated state. Rather, cryptobiotic tardigrades may rely on efficient mechanisms of DNA repair, the nature of which is currently unknown.
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| 2. |
- Kreuzer, M., et al.
(författare)
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Multidisciplinary European Low Dose Initiative (MELODI) : strategic research agenda for low dose radiation risk research
- 2018
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Ingår i: Radiation and Environmental Biophysics. - : Springer Science and Business Media LLC. - 0301-634X .- 1432-2099. ; 57:1, s. 5-15
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Forskningsöversikt (refereegranskat)abstract
- MELODI (Multidisciplinary European Low Dose Initiative) is a European radiation protection research platform with focus on research on health risks after exposure to low-dose ionising radiation. It was founded in 2010 and currently includes 44 members from 18 countries. A major activity of MELODI is the continuous development of a long-term European Strategic Research Agenda (SRA) on low-dose risk for radiation protection. The SRA is intended to identify priorities for national and European radiation protection research programs as a basis for the preparation of competitive calls at the European level. Among those key priorities is the improvement of health risk estimates for exposures close to the dose limits for workers and to reference levels for the population in emergency situations. Another activity of MELODI is to ensure the availability of European key infrastructures for research activities, and the long-term maintenance of competences in radiation research via an integrated European approach for training and education. The MELODI SRA identifies three key research topics in low dose or low dose-rate radiation risk research: (1) dose and dose rate dependence of cancer risk, (2) radiation-induced non-cancer effects and (3) individual radiation sensitivity. The research required to improve the evidence base for each of the three key topics relates to three research lines: (1) research to improve understanding of the mechanisms contributing to radiogenic diseases, (2) epidemiological research to improve health risk evaluation of radiation exposure and (3) research to address the effects and risks associated with internal exposures, differing radiation qualities and inhomogeneous exposures. The full SRA and associated documents can be downloaded from the MELODI website (http://www.melodi-online.eu/sra.html).
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| 3. |
- Beltrán-Pardo, Eliana, et al.
(författare)
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Effects of ionizing radiation on embryos of the tardigrade Milnesium cf. tardigradum at different stages of development
- 2013
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Ingår i: PLOS ONE. - 1932-6203. ; 8:9, s. e72098-
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Tidskriftsartikel (refereegranskat)abstract
- Tardigrades represent one of the most desiccation and radiation tolerant animals on Earth, and several studies havedocumented their tolerance in the adult stage. Studies on tolerance during embryological stages are rare, but differentialeffects of desiccation and freezing on different developmental stages have been reported, as well as dose-dependent effectof gamma irradiation on tardigrade embryos. Here, we report a study evaluating the tolerance of eggs from theeutardigrade Milnesium cf. tardigradum to three doses of gamma radiation (50, 200 and 500 Gy) at the early, middle, andlate stage of development. We found that embryos of the middle and late developmental stages were tolerant to all doses,while eggs in the early developmental stage were tolerant only to a dose of 50 Gy, and showed a declining survival withhigher dose. We also observed a delay in development of irradiated eggs, suggesting that periods of DNA repair might havetaken place after irradiation induced damage. The delay was independent of dose for eggs irradiated in the middle and latestage, possibly indicating a fixed developmental schedule for repair after induced damage. These results show that thetolerance to radiation in tardigrade eggs changes in the course of their development. The mechanisms behind this patternare unknown, but may relate to changes in mitotic activities over the embryogenesis and/or to activation of responsemechanisms to damaged DNA in the course of development.
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| 4. |
- Belyaev, I Y, et al.
(författare)
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915 MHz microwaves and 50 Hz magnetic field affect chromatin conformation and 53BP1 foci in human lymphocytes from hypersensitive and healthy persons
- 2005
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Ingår i: Bioelectromagnetics. - : Wiley. - 0197-8462 .- 1521-186X. ; 26:3, s. 173-184
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Tidskriftsartikel (refereegranskat)abstract
- We used exposure to microwaves from a global system for mobile communication (GSM) mobile phone (915 MHz, specific absorption rate (SAR) 37 mW/kg) and power frequency magnetic field (50 Hz, 15 mu T peak value) to investigate the response of lymphocytes from healthy subjects and from persons reporting hypersensitivity to electromagnetic field (EMF). The hypersensitive and healthy donors were matched by gender and age and the data were analyzed blind to treatment condition. The changes in chromatin conformation were measured with the method of anomalous viscosity time dependencies (AVTD). 53BP1 protein, which has been shown to colocalize in foci with DNA double strand breaks (DSBs), was analyzed by immunostaining in situ. Exposure at room temperature to either 915 MHz or 50 Hz resulted in significant condensation of chromatin, shown as AVTD changes, which was similar to the effect of heat shock at 41 degrees C. No significant differences in responses between normal and hypersensitive subjects were detected. Neither 915 MHz nor 50 Hz exposure induced 53BP1 foci. On the contrary, a distinct decrease in background level of 53BP1 signaling was observed upon these exposures as well as after heat shock treatments. This decrease correlated with the AVTD data and may indicate decrease in accessibility of 53BP1 to antibodies because of stress-induced chromatin condensation. Apoptosis was determined by morphological changes and by apoptotic fragmentation of DNA as analyzed by pulsed-field gel electrophoresis (PFGE). No apoptosis was induced by exposure to 50 Hz and 915 MHz microwaves. In conclusion, 50 Hz magnetic field and 915 MHz microwaves under specified conditions of exposure induced comparable responses in lymphocytes from healthy and hypersensitive donors that were similar but not identical to stress response induced by heat shock.
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| 5. |
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| 6. |
- Andreassi, Maria Grazia, et al.
(författare)
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A Longitudinal Study of Individual Radiation Responses in Pediatric Patients Treated with Proton and Photon Radiotherapy, and Interventional Cardiology : Rationale and Research Protocol of the HARMONIC Project
- 2023
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 24:9, s. 8416-
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Tidskriftsartikel (refereegranskat)abstract
- The Health Effects of Cardiac Fluoroscopy and Modern Radiotherapy (photon and proton) in Pediatrics (HARMONIC) is a five-year project funded by the European Commission that aimed to improve the understanding of the long-term ionizing radiation (IR) risks for pediatric patients. In this paper, we provide a detailed overview of the rationale, design, and methods for the biological aspect of the project with objectives to provide a mechanistic understanding of the molecular pathways involved in the IR response and to identify potential predictive biomarkers of individual response involved in long-term health risks. Biological samples will be collected at three time points: before the first exposure, at the end of the exposure, and one year after the exposure. The average whole-body dose, the dose to the target organ, and the dose to some important out-of-field organs will be estimated. State-of-the-art analytical methods will be used to assess the levels of a set of known biomarkers and also explore high-resolution approaches of proteomics and miRNA transcriptomes to provide an integrated assessment. By using bioinformatics and systems biology, biological pathways and novel pathways involved in the response to IR exposure will be deciphered.
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| 7. |
- Beltran-Pardo, Eliana, et al.
(författare)
-
Effects of ionizing radiation on embryos of the tardigrade Milnesium cf. tardigradum at different stages of development
- 2013
-
Ingår i: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 8:9
-
Tidskriftsartikel (refereegranskat)abstract
- Tardigrades represent one of the most desiccation and radiation tolerant animals on Earth, and several studies havedocumented their tolerance in the adult stage. Studies on tolerance during embryological stages are rare, but differentialeffects of desiccation and freezing on different developmental stages have been reported, as well as dose-dependent effectof gamma irradiation on tardigrade embryos. Here, we report a study evaluating the tolerance of eggs from theeutardigrade Milnesium cf. tardigradum to three doses of gamma radiation (50, 200 and 500 Gy) at the early, middle, andlate stage of development. We found that embryos of the middle and late developmental stages were tolerant to all doses,while eggs in the early developmental stage were tolerant only to a dose of 50 Gy, and showed a declining survival withhigher dose. We also observed a delay in development of irradiated eggs, suggesting that periods of DNA repair might havetaken place after irradiation induced damage. The delay was independent of dose for eggs irradiated in the middle and latestage, possibly indicating a fixed developmental schedule for repair after induced damage. These results show that thetolerance to radiation in tardigrade eggs changes in the course of their development. The mechanisms behind this patternare unknown, but may relate to changes in mitotic activities over the embryogenesis and/or to activation of responsemechanisms to damaged DNA in the course of development.
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| 8. |
- Belyaev, I Y, et al.
(författare)
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Effects of ethidium bromide on DNA loop organisation in human lymphocytes measured by anomalous viscosity time dependence and single cell gel electrophoresis
- 1999
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Ingår i: Biochimica et Biophysica Acta - General Subjects. - 0304-4165 .- 1872-8006. ; 1428:2-3, s. 348-356
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Tidskriftsartikel (refereegranskat)abstract
- The effects of ethidium bromide (EtBr) on human lymphocytes were studied by the method of anomalous viscosity time dependence (AVTD) and by the comet assay. EtBr at low concentrations increased the maximum viscosity and time of radial migration as measured with AVTD at neutral conditions of lysis. A pronounced relaxation of DNA loops was observed with the neutral comet assay. The maximal comet length corresponded to 2 Mb DNA loops. At high concentrations of EtBr, 2. mg/ml, significant reduction in AVTD below control level was seen that suggested hypercondensation of chromatin. The hypercondensation was directly observed with the neutral comet assay. EtBr did not induce DNA strand breaks as measured by the alkaline comet assay. The hypercondensed nuclei could be decondensed by irradiation with gamma-rays or exposure to light. The data provide evidence that EtBr at high concentrations resulted in hypercondensation of chromatin below control level. The comet assay confirmed that the increase in AVTD peaks deals with relaxation of loops and AVTD decrease is caused by chromatin condensation. The prediction of the AVTD theory for a correlation between time of radial migration and condensation of chromatin was verified. Further, the data show that the comet assay at neutral conditions of lysis is rather sensitive to DNA loop relaxation in the absence of DNA damage. Finally, donor specificity was found for the hypercondensation.
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| 9. |
- Czene, S, et al.
(författare)
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DNA fragmentation and morphological changes in apoptotic human lymphocytes
- 2002
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - 0006-291X .- 1090-2104. ; 294:4, s. 872-878
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Tidskriftsartikel (refereegranskat)abstract
- Cell suspensions enriched in cells at various stages of apoptosis were obtained by separation of irradiated human peripheral blood lymphocytes on density gradients at different post-irradiation times. The state of DNA fragmentation in the cells was determined by comet assay and pulsed field gel electrophoresis. The morphologically distinguishable features of apoptosis such as chromatin condensation and cell shrinkage correlated with discrete stages of DNA fragmentation. It was found that greater than or equal to50kbp fragmentation of DNA occurs already in cells of normal density whereas the subsequent DNA fragmentation onto fragments <50 kbp occurs in parallel with cell shrinkage and simultaneous increase in cell density. The observed stages of DNA fragmentation seem to be separated in time that could allow in case of abortive apoptosis formation of chromosomal aberrations.
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| 10. |
- Drobin, Kimi, et al.
(författare)
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Molecular Profiling for Predictors of Radiosensitivity in Patients with Breast or Head-and-Neck Cancer
- 2020
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Ingår i: Cancers. - : MDPI AG. - 2072-6694. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- Nearly half of all cancers are treated with radiotherapy alone or in combination with other treatments, where damage to normal tissues is a limiting factor for the treatment. Radiotherapy-induced adverse health effects, mostly of importance for cancer patients with long-term survival, may appear during or long time after finishing radiotherapy and depending on the patient's radiosensitivity. Currently, there is no assay available that can reliably predict the individual's response to radiotherapy. We profiled two study sets from breast (n = 29) and head-and-neck cancer patients (n = 74) that included radiosensitive patients and matched radioresistant controls. We studied 55 single nucleotide polymorphisms (SNPs) in 33 genes by DNA genotyping and 130 circulating proteins by affinity-based plasma proteomics. In both study sets, we discovered several plasma proteins with the predictive power to find radiosensitive patients (adjusted p < 0.05) and validated the two most predictive proteins (THPO and STIM1) by sandwich immunoassays. By integrating genotypic and proteomic data into an analysis model, it was found that the proteins CHIT1, PDGFB, PNKD, RP2, SERPINC1, SLC4A, STIM1, and THPO, as well as the VEGFA gene variant rs69947, predicted radiosensitivity of our breast cancer (AUC = 0.76) and head-and-neck cancer (AUC = 0.89) patients. In conclusion, circulating proteins and a SNP variant of VEGFA suggest that processes such as vascular growth capacity, immune response, DNA repair and oxidative stress/hypoxia may be involved in an individual's risk of experiencing radiation-induced toxicity.
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| 11. |
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Harms-Ringdahl, K, et al.
(författare)
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Pain assessment with different intensity scales in response to loading of joint structures.
- 1986
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Ingår i: Pain. - 0304-3959. ; 27:3, s. 401-11
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to compare intensity levels assessed on Borg's Category Scale for Ratings of Perceived Pain (BRPP) (1982) (a verbal scale using adjectives and adverbs combined with the numbers 0-10), with assessments on the Visual Analogue Scale (VAS) (a 10 cm horizontal line). Eight healthy subjects volunteered in an experimental study, where pain was provoked by load on passive soft tissue elbow joint structures. Each subject participated 4 times on different occasions in the same experimental set-up, which was divided into six 2 min periods; 3 periods with load induced by applied external weights causing load moments of 3.4 Nm, 4.5 Nm and 6.8 Nm plus that induced by the weight of the lower arm and hand (average 2.9 Nm), followed by 3 periods without external weights. Each series consisted of 12 assessments given during the last 10 sec period of each minute on either the BRPP or the VAS. No significant difference was found between the first and second time a scale was used by the same subject, and none between the assessments on the VAS and the BRPP. Intensity levels of pain increased with load and time and decreased after reduction of the load moments. It is concluded that both scales can be used to reliably assess intensity levels of perceived pain elicited by loading joint structures. Intensity levels, as assessed on both scales, are associated with applied external load and time for exposure.
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| 18. |
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| 19. |
- Jönsson, Ingemar, et al.
(författare)
-
Radiation tolerance in the eutardigrade Richtersius coronifer
- 2005
-
Ingår i: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 81:9, s. 649-656
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: Tardigrades have a reputation of being extremely tolerant to extreme environmental conditions including tolerance to ionizing radiation while in a desiccated, anhydrobiotic state. However, the evidence for radio-tolerance in tardigrades is based on only one previous report, and there is an obvious need for complementary studies. In this paper we report an investigation on radio-tolerance in desiccated and hydrated specimens of the eutardigrade Richtersius coronifer . Materials and methods: Groups of 30 – 50 tardigrades were exposed to γ-radiation at doses between 1.0 – 9.0 (anhydrobiotic animals) or 0.5 – 5.0 (hydrated animals) kGy and the animals were followed until all were dead. Radiation tolerance of both desiccated and hydrated tardigrades was studied. Results: Both desiccated and hydrated animals irradiated with 0.5 and 1 kGy did not deviate in survival from the control groups. Animals from all exposed groups underwent their moulting and egg production cycle, but at decreasing frequency for doses above 1 kGy. No eggs laid by irradiated animals hatched, while eggs laid by controls did so. Conclusion: Our study suggests that radiation tolerance in tardigrades is not due to biochemical protectants connected with the desiccated state. Rather, cryptobiotic tardigrades may rely on efficient mechanisms of DNA repair, the nature of which is currently unknown.
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| 20. |
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| 21. |
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| 22. |
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| 23. |
- Klässbo, M., et al.
(författare)
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Examination of passive ROM and capsular patterns in the hip
- 2003
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Ingår i: Physiotherapy Research International. - : Wiley. - 1358-2267 .- 1471-2865. ; 8:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Background and PurposeThe present study was conducted to examine passive hip range of motion (PROM) for patients with hip dysfunction, including pain, with or without hip osteoarthritis, to arrange and describe PROM patterns and to count the number of hips presenting Cyriax's and Kaltenborn's capsular patterns.MethodThe study is theory-testing, observational, cross-sectional and descriptive. One hundred and sixty-eight patients (mean age 61.7 years, range 36–90 years), 50 with no hip osteoarthritis, 77 with unilateral hip osteoarthritis and 41 with bilateral osteoarthritis, based on radiological reports, were consecutively recruited by physicians in primary health care and orthopaedic settings. One examiner tested PROM bilaterally, by use of a goniometer and a standardized protocol. PROM limitations were calculated by comparing norms from the symptom-free hips (n = 100) in the study, from Kaltenborn and, in patients with unilateral hip osteoarthritis (n = 77), from the non-osteoarthritis hip. The limitations were arranged by size in PROM patterns. The patterns and the numbers of hips with patterns corresponding to Cyriax's and Kaltenborn's capsular patterns were counted.ResultsBetween 68 and 138 PROM patterns were identified by use of different PROM norms for defining limitations. Few osteoarthritis hips showed Cyriax's capsular pattern and none Kaltenborn's capsular pattern.ConclusionsThe concept of capsular pattern for the hip should be re-examined. No support was found in the present study for its existence. It is impossible to anticipate radiological evidence of hip osteoarthritis from the multitude of PROM patterns. Every patient should be regarded as unique.
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| 24. |
- Klässbo, M., et al.
(författare)
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Promising outcome of a Hip School for patients with hip dysfunktion
- 2003
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Ingår i: Arthritis Care and Research. - : Wiley. - 0893-7524 .- 1529-0123 .- 0004-3591. ; 49:3, s. 321-327
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveTo evaluate, in an exploratory study, a hip school led by physical therapists for patients with hip dysfunction including pain.MethodsPhysicians in primary care and orthopedic units consecutively recruited patients by residential area to a treatment group (T group; n = 77) and a control group (C group; n = 68), mean age 61.8 years, 59 men, 86 women. Ninety-nine of the 145 subjects had radiologic hip osteoarthritis. Outcome measures were the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Nottingham Health Profile (NHP).ResultsAfter hip school (6 months) the T group showed greater reduction on the subscales of pain and activity limitations (WOMAC) than the C group. The subscales sleep disturbances, pain, and physical mobility (NHP) showed improvement for the T group compared with at start. The results for the T group persisted after an additional 6 months.ConclusionA hip school may reduce pain and activity limitations and improve health-related quality of life for patients with hip dysfunction including pain.
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| 25. |
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| 26. |
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| 27. |
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| 28. |
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| 29. |
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| 30. |
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| 31. |
- Mosallanezhad, Z., et al.
(författare)
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A structural equation model of the relation between socioeconomic status, physical activity level, independence and health status in older Iranian people
- 2017
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Ingår i: Archives of Gerontology and Geriatrics. - : Elsevier BV. - 0167-4943 .- 1872-6976. ; 70, s. 123-129
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Tidskriftsartikel (refereegranskat)abstract
- Background and aim: Health status is an independent predictor of mortality, morbidity and functioning in older people. The present study was designed to evaluate the link between socioeconomic status (SES), physical activity (PA), independence (I) and the health status (HS) of older people in Iran, using structural equation modelling. Methods: Using computerized randomly selection, a representative sample of 851 75-year-olds living in Tehran (2007-2008), Iran, was included. Participants answered questions regarding indicators of HS, SES and also PA and I through interviews. Both measurement and conceptual models of our hypotheses were tested using Mplus 5. Maximum-likelihood estimation with robust standard errors (MLR estimator), chisquare tests, the goodness of fit index (and degrees of freedom), as well as the Comparative Fit Index (CFI), and the Root Mean Square Error of Approximation (RSMEA) were used to evaluate the model fit. Results: The measurement model yielded a reasonable fit to the data, chi(2) = 110.93, df = 38; CFI = 0.97; RMSEA = 0.047, with 90% C.I. = 0.037-0.058. The model fit for the conceptual model was acceptable; chi(2) = 271.64, df = 39; CFI = 0.91; RMSEA = 0.084, with 90% C.I. = 0.074-0.093. SES itself was not a direct predictor of HS (beta = 0.13, p = 0.059) but it was a predictor of HS either through affecting PA (beta = 0.31, p < 0.001) or I (beta = 0.57, p < 0.001). Conclusion: Socioeconomic status appeared to influence health status, not directly but through mediating some behavioral and self-confidence aspects including physical activity and independence in ADL. (C) 2017 Elsevier B.V. All rights reserved.
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| 32. |
- Nilsson-Wikmar, L, et al.
(författare)
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Back pain in women post-partum is not a unitary concept
- 1999
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Ingår i: Physiotherapy research international : the journal for researchers and clinicians in physical therapy. - : Wiley. - 1358-2267. ; 4:3, s. 201-13
-
Tidskriftsartikel (refereegranskat)
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| 33. |
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| 34. |
- Norrman, Jenny, 1971, et al.
(författare)
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Tracing sources of ammonium in reducing groundwater in a well field in Hanoi (Vietnam) by means of stable nitrogen isotope (δ15N) values
- 2015
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 61, s. 248-258
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Tidskriftsartikel (refereegranskat)abstract
- In the Southern part of Hanoi, high ammonium (NH4+) concentrations in reducing groundwater have been an issue over the last 25years. Elevated NH4+ concentrations in groundwater, in general, are an indicator of influences from anthropogenic sources, but the buried peat layers in the Red River delta formation are also hypothesized to contribute to the high NH4+ levels (up to 100mg/l). We traced the sources of NH4+ at the Nam Du well field of the Hanoi water works by means of isotope ratios (15N/14N). The δ15N values were determined for total sedimentary N and exchangeable NH4+ of the peat material, and for NH4+ dissolved in deep and shallow groundwater, sewage, and surface water. Groundwater NH4+ of the upper (Holocene) and the lower (Pleistocene) aquifers had higher δ15N values than did total N and NH4+ of the sediments, and were somewhat higher than the δ15N values of NH4+ in sewage and surface water. We conclude that the present conditions of temperature and pH tend to promote deprotonation of NH4+ to ammonia (NH3), which eventually degasses from the groundwater table to the unsaturated pore space. This can cause an enrichment of 15N in the remaining NH4+, as the lighter 14N in NH3 is volatilized at a slightly faster rate. The intermediate δ15N values within the Pleistocene aquifer can be explained by the recharge thereto, which is a mixture of the high δ15N values of the Holocene aquifer and the low δ15N values of water infiltrating from the Red River into the Pleistocene aquifer. Some part of the increased groundwater NH4+ is likely to arise from anthropogenic activities, as supported by several indications: a large drawdown in the Pleistocene aquifer caused by Hanoi's extensive water abstraction and subsequent downward gradient from the upper Holocene aquifer; the presence of coliforms in groundwater; and a positive correlation between ammonium and DOC, Cl, Br and Ni, but a lack of correlation with As. However, the much higher concentrations of NH4+ in the groundwater compared to the potential surface sources, the positive correlation between NH4+ and DOC, the abundance of natural organic matter (OM), the amount of exchangeable NH4+ in the sediments, and the highly reducing conditions in the aquifers indicate that N-mineralization of organic N from the peat contribute substantially to the high NH4+ levels in groundwater of the Nam Du well field.
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