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- Fensholt, Rasmus, et al.
(author)
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Greenness in semi-arid areas across the globe 1981-2007 - an Earth Observing Satellite based analysis of trends and drivers
- 2012
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In: Remote Sensing of Environment. - : Elsevier BV. - 0034-4257. ; 121, s. 144-158
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Journal article (peer-reviewed)abstract
- Semi-arid areas, defined as those areas of the world where water is an important limitation for plant growth, have become the subject of increased interest due to the impacts of current global changes and sustainability of human lifestyles. While many ground-based reports of declining vegetation productivity have been published over the last decades, a number of recent publications have shown a nuanced and, for some regions, positive picture. With this background, the paper provides an analysis of trends in vegetation greenness of semi-arid areas using AVHRR GIMMS from 1981 to 2007. The vegetation index dataset is used as a proxy for vegetation productivity and trends are analyzed for characterization of changes in semi-arid vegetation greenness. Calculated vegetation trends are analyzed with gridded data on potential climatic constraints to plant growth to explore possible causes of the observed changes. An analysis of changes in the seasonal variation of vegetation greenness and climatic drivers is conducted for selected regions to further understand the causes of observed inter-annual vegetation changes in semi-arid areas across the globe. It is concluded that semi-arid areas, across the globe, on average experience an increase in greenness (0.015 NDVI units over the period of analysis). Further it is observed that increases in greenness are found both in semi-arid areas where precipitation is the dominating limiting factor for plant production (0.019 NDVI units) and in semi-arid areas where air temperature is the primarily growth constraint (0.013 NDVI units). Finally, in the analysis of changes in the intra-annual variation of greenness it is found that seemingly similar increases in greenness over the study period may have widely different explanations. This implies that current generalizations, claiming that land degradation is ongoing in semi-arid areas worldwide, are not supported by the satellite based analysis of vegetation greenness. (c) 2012 Elsevier Inc. All rights reserved.
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| 2. |
- Helldén, Anders, et al.
(author)
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Fluconazole-induced intoxication with phenytoin in a patient with ultra-high activity of CYP2C9
- 2010
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In: European Journal of Clinical Pharmacology. - : Springer Science and Business Media LLC. - 0031-6970 .- 1432-1041. ; 66:8, s. 791-5
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Journal article (peer-reviewed)abstract
- PURPOSE: The cytochrome P450 enzyme CYP2C9 metabolizes several important drugs, such as warfarin and oral antidiabetic drugs. The enzyme is polymorphic, and all known alleles, for example, CYP2C9*2 and*3, give decreased activity. Ultra-high activity of the enzyme has not yet been reported.METHODS: We present a patient with Behçet's disease who required treatment with high doses of phenytoin. When fluconazole, a potent inhibitor of CYP2C9, was added to the treatment regimen, the patient developed ataxia, tremor, fatigue, slurred speech and somnolence, indicating phenytoin intoxication. On suspicion of ultra-high activity of CYP2C9, a phenotyping test for CYP2C9 with losartan was performed.RESULTS: The patient was shown to have a higher activity of CYP2C9 than any of the 190 healthy Swedish Caucasians used as controls.CONCLUSIONS: Our finding of an ultrarapid metabolism of losartan and phenytoin may apply to other CYP2C9 substrates, where inhibition of CYP2C9 may cause severe adverse drug reactions.
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| 3. |
- Hellden, Anders, et al.
(author)
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Renal function estimations and dose recommendations for dabigatran, gabapentin and valaciclovir : a data simulation study focused on the elderly
- 2013
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In: BMJ Open. - London, UK : BMJ. - 2044-6055. ; 3:4, s. e002686-
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Journal article (peer-reviewed)abstract
- Objectives The thrombin inhibitor dabigatran is mainly excreted by the kidneys. We investigated whether the recommended method for estimation of renal function used in the clinical trials, the Cockcroft-Gault (CG(old)) equation and the estimated glomerular filtration rate (eGFR) modification of diet in renal disease equation 4 (MDRD4), differ in elderly participants, resulting in erroneously higher dose recommendations of dabigatran, which might explain the serious, even fatal, bleeding reported. The renally excreted drugs gabapentin and valaciclovir were also included for comparison. Design A retrospective data simulation study. Participants Participants 65years and older included in six different studies. Main outcome measure Estimated renal function by CG based on uncompensated (old Jaffe' method) creatinine (CG(old)) or by MDRD4 based on standardised compensated P-creatinine traceable to isotope-dilution mass spectrometry, and the resulting doses. Results 790 participants (432 females), mean age (SD) 77.6 +/- 5.7years. Mean estimated creatinine clearance (eCrCl) by the CG(old) equation was 44.2 +/- 14.8ml/min, versus eGFR 59.6 +/- 20.7ml/min/1.73m(2) with MDRD4 (p<0.001), absolute median difference 13.5, 95% CI 12.9 to 14.2. MDRD4 gave a significantly higher mean dose (valaciclovir +21%, dabigatran +25% and gabapentin +37%) of all drugs (p<0.001). With MDRD4 58% of the women would be recommended a full dose of dabigatran compared with 18% if CG(old) is used. Conclusions MDRD4 would result in higher recommended doses of the three studied drugs to elderly participants compared with CG, particularly in women, and thus increased the risk of dose and concentration-dependent adverse reactions. It is important to know which method of estimation of renal function the Summary of Products Characteristics was based on, and use only that one when prescribing renally excreted drugs with narrow safety window. Doses based on recently developed methods for estimation of renal function may be associated with considerable risk of overtreatment in the elderly.
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| 4. |
- Wu, Weicheng, et al.
(author)
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Assessing woody biomass in African tropical savannahs by multiscale remote sensing
- 2013
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In: International Journal of Remote Sensing. - : Informa UK Limited. - 1366-5901 .- 0143-1161. ; 34:13, s. 4525-4549
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Journal article (peer-reviewed)abstract
- Woody biomass production is a critical indicator in evaluation of land use management and the dynamics of the global carbon cycle (sequestration/emission) in terrestrial ecosystems. The objective of the present study was to develop, through a case study in Sudan, an operational multiscale remote-sensing-based methodology for large-scale estimation of woody biomass in tropical savannahs. Woody biomass estimation models obtained by different authors from destructive field measurements in different tropical savannah ecosystems were expressed as functions of tree canopy cover (CC). The field-measured CC data were used for developing regression equations with atmospherically corrected and reflectance-based vegetation indices derived from Landsat ETM+ (Enhanced Thematic Mapper Plus) imagery. Among a set of vegetation indices, the normalized difference vegetation index (NDVI) provided the best correlation with CC (R-2 = 0.91) and was hence selected for woodland woody biomass estimation. After validation of the CC-NDVI model and its applicability to Moderate Resolution Imaging Spectroradiometer (MODIS) data, time-series MODIS NDVI data (MOD13Q1) were used to partition the woody component from the herbaceous component for sparse woodlands, woodlands and forests defined by the Food and Agriculture Organization (FAO) of the United Nations Land Cover Map. Following the weighting of the estimation models based on the dominant woody species in each vegetation community, NDVI-based woody biomass models were applied according to their weighted ratios to the decomposed summer and autumn woody NDVI images in all vegetation communities in the whole of Sudan taking the year 2007, for example. The results were found to be in good agreement with those from other authors obtained by either field measurements or other remote sensing methods using MODIS and lidar data. It is concluded that the proposed approach is operational and can be applied for a reliable large-scale assessment of woody biomass at a ground resolution of 250m in tropical savannah woodlands of any month or season.
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