Cesium as an alkali element exhibits a chemical reactivity similar to that of potassium, an essen... more Cesium as an alkali element exhibits a chemical reactivity similar to that of potassium, an essential element for plants. It has been suggested that Cs phytotoxicity might be due either to its competition with potassium to enter the plant, resulting in K starvation, or to its intracellular competition with K binding sites in cells. Such elemental interactions can be evidenced by chemical imaging, which determines the elemental distributions. In this study, the model plant Arabidopsis thaliana was exposed to 1 mM cesium in the presence (20 mM) or not of potassium. The quantitative imaging of Cs and endogenous elements (P, S, Cl, K, Ca, Mn, Fe, and Zn) was carried out using ion beam micro-chemical imaging with 5 μm spatial resolution. Chemical imaging was also evidenced by microfocused synchrotron-based X-ray fluorescence (μXRF) which presents a better lateral resolution (< 1 μm) but is not quantitative. Cesium distribution was similar to potassium which suggests that Cs can compete with K binding sites in cells. Cesium and potassium were mainly concentrated in the vascular system of stems and leaves. Cs was also found in lower concentration in leaves mesophyll/epidermis. This late representing the larger proportion in mass, mesophyll/epidermis can be considered as the major storage site for cesium in A. thaliana. Trichomes were not found to accumulate cesium. Interestingly, increased Mn, Fe, and Zn concentrations were observed in leaves at high chlorosis. Mn and Fe increased more in the mesophyll than in veins, whereas zinc increased more in veins than in the mesophyll suggesting a tissue specific interaction of Cs with these trace elements homeostasis. This study illustrates the sensitivity of ion beam microprobe and microfocused synchrotron-based X-ray fluorescence to investigate concentrations and distributions of major and trace elements in plants. It also shows the suitability of these analytical imaging techniques to complement biochemical investigations of metallic stress in plants.
Cobalt is known to be toxic at high concentration, to induce contact dermatosis, and occupational... more Cobalt is known to be toxic at high concentration, to induce contact dermatosis, and occupational radiation skin damage because of its use in nuclear industry. We investigated the intracellular distribution of cobalt in HaCaT human keratinocytes as a model of skin cells, and its interaction with endogenous trace elements. Direct micro-chemical imaging based on ion beam techniques was applied to determine the quantitative distribution of cobalt in HaCaT cells. In addition, synchrotron radiation X-ray fluorescence microanalysis in tomography mode was performed, for the first time on a single cell, to determine the 3D intracellular distribution of cobalt. Results obtained with these micro-chemical techniques were compared to a more classical method based on cellular fractionation followed by inductively coupled plasma atomic emission spectrometry (ICP-AES) measurements. Cobalt was found to accumulate in the cell nucleus and in perinuclear structures indicating the possible direct interaction with genomic DNA, and nuclear proteins. The perinuclear accumulation in the cytosol suggests that cobalt could be stored in the endoplasmic reticulum or the Golgi apparatus. The multi-elemental analysis revealed that cobalt exposure significantly decreased magnesium and zinc content, with a likely competition of cobalt for magnesium and zinc binding sites in proteins. Overall, these data suggest a multiform toxicity of cobalt related to interactions with genomic DNA and nuclear proteins, and to the alteration of zinc and magnesium homeostasis.
The scanning transmission ion microscope (STIM) has been used to determine the intracellular mass... more The scanning transmission ion microscope (STIM) has been used to determine the intracellular mass of human cultured cells. A 4He+ microbeam of 2.0 MeV energy was chosen to obtain enhanced ion-energy-loss sensitivity through the micron-thick freeze-dried cells. Local sample mass calculation, based on energy-loss conversion by use of appropriate matrix stopping powers, was performed by use of dedicated software. The method was validated with epoxy resin sections and polymer foil as analogues of biological samples in the range of (intra)cellular thickness, 150 to 3000 nm. STIM analysis resulted in less than 5% error in mass determination. 4He+ energy-loss micro-spectrometry was performed on freeze-dried human ovarian cancer cells, the mean areal mass obtained was 120 µg cm–2 (200 µg cm–2 in the nucleus and 250 µg cm–2 in nucleoli). This method is particularly useful for mass normalization of X-ray fluorescence yields resulting from particle-induced X-ray emission microanalysis (micro-PIXE). When performed successively these two ion-beam micro-analytical methods enable the mapping of true element concentrations within single cells.
a key to understand the mechanisms involved in the biology of chemical elements. When performed w... more a key to understand the mechanisms involved in the biology of chemical elements. When performed with a microbeam, X-ray absorption near-edge structure (micro-XANES) enables the direct speciation analysis of oxidation states in subcellular compartments avoiding cell fractionation and other preparation steps that might modify the chemical species. Here we report the principal characteristics in terms of spatial resolution, detection limit, reproducibility, and repeatability of a micro-XANES experimental setup based on Kirkpatrick-Baez X-ray focusing optics that maintains high flux of incoming radiation (>10 11 photons/s) at micrometric spatial resolution (1.5 × 4.0 µm 2 ). Applications and limitations of this setup are illustrated by examples of iron and arsenic absorption spectra obtained from the cytosol, nucleus, and mitochondrial network of cultured cells. A better repeatability and sensitivity with no oxidation state modification and minimal beam damage is achieved when cells are analyzed in a frozen hydrated state, as compared to freeze-dried cells. This original experimental setup can now be applied for the direct speciation analysis of most trace elements at the subcellular level. Miller, L. M.; Aschner, M.; Eliseev, R.; Depuis, D.; Gavin, C.
Background: More than 60,000,000 Bangladeshis are drinking water with unsafe concentrations of on... more Background: More than 60,000,000 Bangladeshis are drinking water with unsafe concentrations of one or more elements. oBjectives: Our aims in this study were to evaluate and improve the drinking water testing and treatment plans for western Bangladesh. Methods: We sampled groundwater from four neighborhoods in western Bangladesh to determine the distributions of arsenic, boron, barium, chromium, iron, manganese, molybdenum, nickel, lead, antimony, selenium, uranium, and zinc, and to determine pH. results: The percentages of tube wells that had concentrations exceeding World Health Organization (WHO) health-based drinking water guidelines were 78% for Mn, 48% for U, 33% for As, 1% for Pb, 1% for Ni, and 1% for Cr. Individual tube wells often had unsafe concentrations of both Mn and As or both Mn and U. They seldom had unsafe concentrations of both As and U. conclusions: These results suggest that the ongoing program of identifying safe drinking water supplies by testing every tube well for As only will not ensure safe concentrations of Mn, U, Pb, Ni, Cr, and possibly other elements. To maximize efficiency, drinking water testing in Bangladesh should be completed in three steps: 1) all tube wells must be sampled and tested for As; 2) if a sample meets the WHO guideline for As, then it should be retested for Mn and U; 3) if a sample meets the WHO guidelines for As, Mn, and U, then it should be retested for B, Ba, Cr, Mo, Ni, and Pb. All safe tube wells should be considered for use as public drinking water supplies. key words: arsenic, Bangladesh, chronic arsenic poisoning, drinking water, manganese, uranium.
All of Bangladesh's approximately 10 million drinking-water tube wells must be periodically teste... more All of Bangladesh's approximately 10 million drinking-water tube wells must be periodically tested for arsenic. The magnitude of this task and the limited resources of Bangladesh have led to the use of low-cost, semiquantitative field kits that measure As to a relatively high 50 µg/L national drinking water standard. However, there is an urgent need to supplement and ultimately replace these field kits with an inexpensive laboratory method that can measure As to the more protective 10 µg/L World Health Organization (WHO) health-based drinking water guideline. Unfortunately, Bangladesh has limited access to atomic absorption spectrometers or other expensive instruments that can measure As to the WHO guideline of 10 µg/L. In response to this need, an inexpensive and highly sensitive laboratory method for measuring As has been developed. This new method is the only accurate, precise, and safe way to quantify As < 10 µg/L without expensive or highly specialized laboratory equipment. In this method, As is removed from the sample by reduction to arsine gas, collected in an absorber by oxidation to arsenic acid, colorized by a sequential reaction to arsenomolybdate, and quantified by spectrophotometry. We compared this method with the silver diethyldithiocarbamate [AgSCSN(CH 2 CH 3 ) 2 ] and graphite furnace atomic absorption spectroscopy (GFAAS) methods for measuring As. Our method is more accurate, precise, and environmentally safe than the AgSCSN(CH 2 CH 3 ) 2 method, and it is more accurate and affordable than GFAAS. Finally, this study suggests that Bangladeshis will readily share drinking water with their neighbors to meet the more protective WHO guideline for As of 10 µg/L.
Background: More than 60,000,000 Bangladeshis are drinking water with unsafe concentrations of on... more Background: More than 60,000,000 Bangladeshis are drinking water with unsafe concentrations of one or more elements. oBjectives: Our aims in this study were to evaluate and improve the drinking water testing and treatment plans for western Bangladesh. Methods: We sampled groundwater from four neighborhoods in western Bangladesh to determine the distributions of arsenic, boron, barium, chromium, iron, manganese, molybdenum, nickel, lead, antimony, selenium, uranium, and zinc, and to determine pH. results: The percentages of tube wells that had concentrations exceeding World Health Organization (WHO) health-based drinking water guidelines were 78% for Mn, 48% for U, 33% for As, 1% for Pb, 1% for Ni, and 1% for Cr. Individual tube wells often had unsafe concentrations of both Mn and As or both Mn and U. They seldom had unsafe concentrations of both As and U. conclusions: These results suggest that the ongoing program of identifying safe drinking water supplies by testing every tube well for As only will not ensure safe concentrations of Mn, U, Pb, Ni, Cr, and possibly other elements. To maximize efficiency, drinking water testing in Bangladesh should be completed in three steps: 1) all tube wells must be sampled and tested for As; 2) if a sample meets the WHO guideline for As, then it should be retested for Mn and U; 3) if a sample meets the WHO guidelines for As, Mn, and U, then it should be retested for B, Ba, Cr, Mo, Ni, and Pb. All safe tube wells should be considered for use as public drinking water supplies. key words: arsenic, Bangladesh, chronic arsenic poisoning, drinking water, manganese, uranium.
Cesium as an alkali element exhibits a chemical reactivity similar to that of potassium, an essen... more Cesium as an alkali element exhibits a chemical reactivity similar to that of potassium, an essential element for plants. It has been suggested that Cs phytotoxicity might be due either to its competition with potassium to enter the plant, resulting in K starvation, or to its intracellular competition with K binding sites in cells. Such elemental interactions can be evidenced by chemical imaging, which determines the elemental distributions. In this study, the model plant Arabidopsis thaliana was exposed to 1 mM cesium in the presence (20 mM) or not of potassium. The quantitative imaging of Cs and endogenous elements (P, S, Cl, K, Ca, Mn, Fe, and Zn) was carried out using ion beam micro-chemical imaging with 5 μm spatial resolution. Chemical imaging was also evidenced by microfocused synchrotron-based X-ray fluorescence (μXRF) which presents a better lateral resolution (< 1 μm) but is not quantitative. Cesium distribution was similar to potassium which suggests that Cs can compete with K binding sites in cells. Cesium and potassium were mainly concentrated in the vascular system of stems and leaves. Cs was also found in lower concentration in leaves mesophyll/epidermis. This late representing the larger proportion in mass, mesophyll/epidermis can be considered as the major storage site for cesium in A. thaliana. Trichomes were not found to accumulate cesium. Interestingly, increased Mn, Fe, and Zn concentrations were observed in leaves at high chlorosis. Mn and Fe increased more in the mesophyll than in veins, whereas zinc increased more in veins than in the mesophyll suggesting a tissue specific interaction of Cs with these trace elements homeostasis. This study illustrates the sensitivity of ion beam microprobe and microfocused synchrotron-based X-ray fluorescence to investigate concentrations and distributions of major and trace elements in plants. It also shows the suitability of these analytical imaging techniques to complement biochemical investigations of metallic stress in plants.
Cobalt is known to be toxic at high concentration, to induce contact dermatosis, and occupational... more Cobalt is known to be toxic at high concentration, to induce contact dermatosis, and occupational radiation skin damage because of its use in nuclear industry. We investigated the intracellular distribution of cobalt in HaCaT human keratinocytes as a model of skin cells, and its interaction with endogenous trace elements. Direct micro-chemical imaging based on ion beam techniques was applied to determine the quantitative distribution of cobalt in HaCaT cells. In addition, synchrotron radiation X-ray fluorescence microanalysis in tomography mode was performed, for the first time on a single cell, to determine the 3D intracellular distribution of cobalt. Results obtained with these micro-chemical techniques were compared to a more classical method based on cellular fractionation followed by inductively coupled plasma atomic emission spectrometry (ICP-AES) measurements. Cobalt was found to accumulate in the cell nucleus and in perinuclear structures indicating the possible direct interaction with genomic DNA, and nuclear proteins. The perinuclear accumulation in the cytosol suggests that cobalt could be stored in the endoplasmic reticulum or the Golgi apparatus. The multi-elemental analysis revealed that cobalt exposure significantly decreased magnesium and zinc content, with a likely competition of cobalt for magnesium and zinc binding sites in proteins. Overall, these data suggest a multiform toxicity of cobalt related to interactions with genomic DNA and nuclear proteins, and to the alteration of zinc and magnesium homeostasis.
The scanning transmission ion microscope (STIM) has been used to determine the intracellular mass... more The scanning transmission ion microscope (STIM) has been used to determine the intracellular mass of human cultured cells. A 4He+ microbeam of 2.0 MeV energy was chosen to obtain enhanced ion-energy-loss sensitivity through the micron-thick freeze-dried cells. Local sample mass calculation, based on energy-loss conversion by use of appropriate matrix stopping powers, was performed by use of dedicated software. The method was validated with epoxy resin sections and polymer foil as analogues of biological samples in the range of (intra)cellular thickness, 150 to 3000 nm. STIM analysis resulted in less than 5% error in mass determination. 4He+ energy-loss micro-spectrometry was performed on freeze-dried human ovarian cancer cells, the mean areal mass obtained was 120 µg cm–2 (200 µg cm–2 in the nucleus and 250 µg cm–2 in nucleoli). This method is particularly useful for mass normalization of X-ray fluorescence yields resulting from particle-induced X-ray emission microanalysis (micro-PIXE). When performed successively these two ion-beam micro-analytical methods enable the mapping of true element concentrations within single cells.
a key to understand the mechanisms involved in the biology of chemical elements. When performed w... more a key to understand the mechanisms involved in the biology of chemical elements. When performed with a microbeam, X-ray absorption near-edge structure (micro-XANES) enables the direct speciation analysis of oxidation states in subcellular compartments avoiding cell fractionation and other preparation steps that might modify the chemical species. Here we report the principal characteristics in terms of spatial resolution, detection limit, reproducibility, and repeatability of a micro-XANES experimental setup based on Kirkpatrick-Baez X-ray focusing optics that maintains high flux of incoming radiation (>10 11 photons/s) at micrometric spatial resolution (1.5 × 4.0 µm 2 ). Applications and limitations of this setup are illustrated by examples of iron and arsenic absorption spectra obtained from the cytosol, nucleus, and mitochondrial network of cultured cells. A better repeatability and sensitivity with no oxidation state modification and minimal beam damage is achieved when cells are analyzed in a frozen hydrated state, as compared to freeze-dried cells. This original experimental setup can now be applied for the direct speciation analysis of most trace elements at the subcellular level. Miller, L. M.; Aschner, M.; Eliseev, R.; Depuis, D.; Gavin, C.
Background: More than 60,000,000 Bangladeshis are drinking water with unsafe concentrations of on... more Background: More than 60,000,000 Bangladeshis are drinking water with unsafe concentrations of one or more elements. oBjectives: Our aims in this study were to evaluate and improve the drinking water testing and treatment plans for western Bangladesh. Methods: We sampled groundwater from four neighborhoods in western Bangladesh to determine the distributions of arsenic, boron, barium, chromium, iron, manganese, molybdenum, nickel, lead, antimony, selenium, uranium, and zinc, and to determine pH. results: The percentages of tube wells that had concentrations exceeding World Health Organization (WHO) health-based drinking water guidelines were 78% for Mn, 48% for U, 33% for As, 1% for Pb, 1% for Ni, and 1% for Cr. Individual tube wells often had unsafe concentrations of both Mn and As or both Mn and U. They seldom had unsafe concentrations of both As and U. conclusions: These results suggest that the ongoing program of identifying safe drinking water supplies by testing every tube well for As only will not ensure safe concentrations of Mn, U, Pb, Ni, Cr, and possibly other elements. To maximize efficiency, drinking water testing in Bangladesh should be completed in three steps: 1) all tube wells must be sampled and tested for As; 2) if a sample meets the WHO guideline for As, then it should be retested for Mn and U; 3) if a sample meets the WHO guidelines for As, Mn, and U, then it should be retested for B, Ba, Cr, Mo, Ni, and Pb. All safe tube wells should be considered for use as public drinking water supplies. key words: arsenic, Bangladesh, chronic arsenic poisoning, drinking water, manganese, uranium.
All of Bangladesh's approximately 10 million drinking-water tube wells must be periodically teste... more All of Bangladesh's approximately 10 million drinking-water tube wells must be periodically tested for arsenic. The magnitude of this task and the limited resources of Bangladesh have led to the use of low-cost, semiquantitative field kits that measure As to a relatively high 50 µg/L national drinking water standard. However, there is an urgent need to supplement and ultimately replace these field kits with an inexpensive laboratory method that can measure As to the more protective 10 µg/L World Health Organization (WHO) health-based drinking water guideline. Unfortunately, Bangladesh has limited access to atomic absorption spectrometers or other expensive instruments that can measure As to the WHO guideline of 10 µg/L. In response to this need, an inexpensive and highly sensitive laboratory method for measuring As has been developed. This new method is the only accurate, precise, and safe way to quantify As < 10 µg/L without expensive or highly specialized laboratory equipment. In this method, As is removed from the sample by reduction to arsine gas, collected in an absorber by oxidation to arsenic acid, colorized by a sequential reaction to arsenomolybdate, and quantified by spectrophotometry. We compared this method with the silver diethyldithiocarbamate [AgSCSN(CH 2 CH 3 ) 2 ] and graphite furnace atomic absorption spectroscopy (GFAAS) methods for measuring As. Our method is more accurate, precise, and environmentally safe than the AgSCSN(CH 2 CH 3 ) 2 method, and it is more accurate and affordable than GFAAS. Finally, this study suggests that Bangladeshis will readily share drinking water with their neighbors to meet the more protective WHO guideline for As of 10 µg/L.
Background: More than 60,000,000 Bangladeshis are drinking water with unsafe concentrations of on... more Background: More than 60,000,000 Bangladeshis are drinking water with unsafe concentrations of one or more elements. oBjectives: Our aims in this study were to evaluate and improve the drinking water testing and treatment plans for western Bangladesh. Methods: We sampled groundwater from four neighborhoods in western Bangladesh to determine the distributions of arsenic, boron, barium, chromium, iron, manganese, molybdenum, nickel, lead, antimony, selenium, uranium, and zinc, and to determine pH. results: The percentages of tube wells that had concentrations exceeding World Health Organization (WHO) health-based drinking water guidelines were 78% for Mn, 48% for U, 33% for As, 1% for Pb, 1% for Ni, and 1% for Cr. Individual tube wells often had unsafe concentrations of both Mn and As or both Mn and U. They seldom had unsafe concentrations of both As and U. conclusions: These results suggest that the ongoing program of identifying safe drinking water supplies by testing every tube well for As only will not ensure safe concentrations of Mn, U, Pb, Ni, Cr, and possibly other elements. To maximize efficiency, drinking water testing in Bangladesh should be completed in three steps: 1) all tube wells must be sampled and tested for As; 2) if a sample meets the WHO guideline for As, then it should be retested for Mn and U; 3) if a sample meets the WHO guidelines for As, Mn, and U, then it should be retested for B, Ba, Cr, Mo, Ni, and Pb. All safe tube wells should be considered for use as public drinking water supplies. key words: arsenic, Bangladesh, chronic arsenic poisoning, drinking water, manganese, uranium.
Uploads
Papers by Richard Ortega