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Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived from measurements at solar maximum.) The bow shock is close to the planet, meaning that it is possible that some solar wind could be absorbed by the atmosphere and contribute to the evolution of the atmosphere. Here we report magnetic field measurements from the Venus Express spacecraft in the plasma environment surrounding Venus. The bow shock under low solar activity conditions seems to be in the position that would be expected from a complete deflection by a magnetized ionosphere. Therefore little solar wind enters the Venus ionosphere even at solar minimum.
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There is currently interest in the metabolism of the various compounds which make up the vitamin E family, especially with regards to the possible use of vitamin E metabolites as markers of oxidative stress and adequate vitamin E supply. A number of vitamin E metabolites have been described to date and we have recently developed a method to extract and quantitate a range of vitamin E metabolites in human urine. During the development of this method a new metabolite of alpha-tocopherol was identified, which we tentatively characterised as 5-(6-hydroxy-2,5,7,8-tetramethyl-chroman-2-yl)-2-methyl-pentanoic acid (alpha-CMBHC).(1) Here we describe the synthesis of alpha-CMBHC as a standard and confirm that it is a metabolite of alpha-tocopherol.
Assuntos
Vitamina E/urina , Cromatografia Gasosa , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Piridinas/síntese química , Pirimidinas/síntese químicaRESUMO
There is currently interest in measuring urinary metabolites of vitamin E. It has been suggested that alpha-to-copheronolactone (alphaTL), with an oxidized chroman ring, may be an indicator of in vivo oxidative stress and 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman (alpha-CEHC), with a shortened side chain but intact hydroxychroman ring, may provide a measure of adequate or excess vitamin E status. To date, methods in the literature have tended to concentrate on the estimation of single metabolites. We describe the establishment and validation of a relatively simple and reproducible method to extract and quantitate a range of vitamin E metabolites using 0.5 ml of human urine. The vitamin E metabolites were extracted from urine using solid phase extraction cartridges, deconjugated enzymatically, and analyzed using gas chromatography-mass spectrometry. Using this method we have identified alphaTL and the CEHC metabolites derived from alpha-, delta-, and gamma-tocopherol. In addition we have tentatively identified a novel group of vitamin E metabolites, which are related to the CEHCs but have three extra carbons in the side chain. The possibility of the artifactual oxidation of alpha-CEHC to alphaTL during the assay procedure is also discussed.
Assuntos
Vitamina E/urina , Animais , Cromanos/urina , Deutério , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Métodos , Estresse Oxidativo , Propionatos/urina , Ratos , Reprodutibilidade dos Testes , Vitamina E/análogos & derivados , Vitamina E/química , Vitamina E/metabolismoRESUMO
THE ADVANCED WOUND HEALING RESOURCE A COLOUR ATLAS OF BURN INJURIES.
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FORMULARY OF WOUND MANAGEMENT PRODUCTS (Fifth edition) THE WOUND PROGRAMME UNDERSTANDING WHY: MOIST WOUND HEALING PRESSURE SORES: VIDEO LECTURES.
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TOPICAL PREPARATIONS WOUND CARE SOCIETY PREVENTING PRESSURE SORES AFTER HIP FRACTURES LEG ULCER CLINIC DRESSING METHODS AFTER TOENAIL REMOVAL WOUND CARE IS NOT A GAME POINT OF STYLE JOURNAL BINDERS.
