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X-ray Microanalysis (x-ray + microanalysi)
Selected AbstractsIn-situ TiC precipitation in molten Fe-C and their characterisationCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2008K. I. Parashivamurthy Abstract TiC particles were formed in liquid iron solution by the reaction between pure titanium and carbon available in molten iron. TiC particles have been precipitated in steels with four different carbon contents by in situ reactions during melting. The influence of titanium and carbon concentration on the precipitation of TiC was studied. The samples were studied by means of optical microscopy, scanning electron microscopy and X-ray microanalysis. The morphology of the obtained crystals was studied and correlated with carbon and titanium. It was found that TiC crystallises as primary crystals at 1600°C during solidification of the Fe-Ti-C melt. The obtained crystals were of cubic, rectangle and had maximum size of 18.7 µm. The size and shape of the carbides increases with increasing carbon and titanium in molten iron. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Grazing protozoa and magnetosome dissolution in magnetotactic bacteriaENVIRONMENTAL MICROBIOLOGY, Issue 11 2007Juliana L. Martins Summary Magnetotactic bacteria show an ability to navigate along magnetic field lines because of magnetic particles called magnetosomes. All magnetotactic bacteria are unicellular except for the multicellular prokaryote (recently named ,Candidatus Magnetoglobus multicellularis'), which is formed by an orderly assemblage of 17,40 prokaryotic cells that swim as a unit. A ciliate was used in grazing experiments with the M. multicellularis to study the fate of the magnetosomes after ingestion by the protozoa. Ciliates ingested M. multicellularis, which were located in acid vacuoles as demonstrated by confocal laser scanning microscopy. Transmission electron microscopy and X-ray microanalysis of thin-sectioned ciliates showed the presence of M. multicellularis and magnetosomes inside vacuoles in different degrees of degradation. The magnetosomes are dissolved within the acidic vacuoles of the ciliate. Depending on the rate of M. multicellularis consumption by the ciliates the iron from the magnetosomes may be recycled to the environment in a more soluble form. [source] Analysis of the behaviour of the structural concrete after the fire at the Windsor Building in MadridFIRE AND MATERIALS, Issue 2 2010E. Menéndez Abstract The analysis of the concrete subjected to high temperatures is usually undertaken by means of tests specifically designed and carried out in the laboratory, or by using theoretical approaches using standardized curves for theoretical fires. An analysis by different techniques has been carried out on structural concrete to real fire of Windsor Building in Madrid, which was severally damaged by a fire in 2005. These techniques are X-ray diffraction, differential thermal and thermogravimetric analysis and backscattered electron microscopy with dispersive X-ray microanalysis. Samples of the concrete were taken from different floors in the building and analyses were carried out at different depths starting from the surface exposed to the fire itself. The analysis allows the damaged area to be limited as well as situating the 500,C isotherm in the concrete element. In accordance with the results obtained, the damage is limited to just a few centimeters from the surface exposed to the fire itself, in spite of its prolonged exposure to the fire. This would justify that the concrete has demonstrated a suitable resistant behaviour. Likewise, it can be deduced from the results obtained that the fire, to which the concrete was subjected, can be qualified as severe. Also, these results can confirm that the calculation hypothesis in the project is correct in relation to the fire resistance exigencies of the concrete. Copyright © 2009 John Wiley & Sons, Ltd. [source] Enhanced Optical Properties and Opaline Self-Assembly of PPV Encapsulated in Mesoporous Silica SpheresADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Timothy L. Kelly Abstract A new poly(p -phenylenevinylene) (PPV) composite material has been developed by the incorporation of insoluble PPV polymer chains in the pores of monodisperse mesoporous silica spheres through an ion-exchange and in situ polymerization method. The polymer distribution within the resultant colloidal particles is characterized by electron microscopy, energy dispersive X-ray microanalysis, powder X-ray diffraction, and nitrogen adsorption. It was found that the polymer was selectively incorporated into the mesopores of the silica host and was well distributed throughout the body of the particles. This confinement of the polymer influences the optical properties of the composite; these were examined by UV,vis and fluorescence spectroscopy and time-correlated single-photon counting. The results show a material that exhibits an extremely high fluorescence quantum yield (approaching 85%), and an improved resistance to oxidative photobleaching compared to PPV. These enhanced optical properties are further complemented by the overall processability of the colloidal material. In marked contrast to the insolubility of PPV, the material can be processed as a stable colloidal dispersion, and the individual composite spheres can be self-assembled into opaline films using the vertical deposition method. The bandgap of the opal can be engineered to overlap with the emission band of the polymer, which has significant ramifications for lasing. [source] Application of the parametric bootstrap method to determine statistical errors in quantitative X-ray microanalysis of thin filmsJOURNAL OF MICROSCOPY, Issue 1 2007ALDO ARMIGLIATO Summary We applied the parametric bootstrap to the X-ray microanalysis of Si-Ge binary alloys, in order to assess the dependence of the Ge concentrations and the local film thickness, obtained by using previously described Monte Carlo methods, on the precision of the measured intensities. We show how it is possible by this method to determine the statistical errors associated with the quantitative analysis performed in sample regions of different composition and thickness, but by conducting only one measurement. We recommend the use of the bootstrap for a broad range of applications for quantitative microanalysis to estimate the precision of the final results and to compare the performances of different methods to each other. Finally, we exploited a test based on bootstrap confidence intervals to ascertain if, for given X-ray intensities, different values of the estimated composition in two points of the sample are indicative of an actual lack of homogeneity. [source] An ultrastructural study of cellular response to variation in porosity in phase-pure hydroxyapatiteJOURNAL OF MICROSCOPY, Issue 2 2004B. ANNAZ Summary Hydroxyapatite has been shown to be biocompatible and bioactive. Incorporation of porosity has been shown to enhance osteointegration; however, difficulty in controlling the extent and type of porosity has limited investigation into determining the role of both macro- and microporosity. The current investigation reports on the synthesis of four types of phase-pure hydroxyapatite with varying levels of porosity (HA1,HA4), and with defined levels of macro- and microporosities. Transmission electron microscopy was used to evaluate qualitatively the effect of these two parameters on cell,material interactions following a 30-day incubation period. Biological mineralization was observed within vesicles and the needle-like minerals were confirmed as hydroxyapatite using X-ray microanalysis. This demonstrated the suitability of primary human osteoblast-like cells as a tool to assess the extent of mineralization. Furthermore, internalization of hydroxyapatite particles was observed. Our findings show that the variation in macro- and microporosity does not affect the extent of cell,material interaction, with collagen synthesis evident in all samples. [source] Differentiation of snake epidermis, with emphasis on the shedding layerJOURNAL OF MORPHOLOGY, Issue 2 2005Lorenzo Alibardi Abstract Little is known about specific proteins involved in keratinization of the epidermis of snakes. The presence of histidine-rich molecules, sulfur, keratins, loricrin, transglutaminase, and isopeptide-bonds have been studied by ultrastructural autoradiography, X-ray microanalysis, and immunohistochemistry in the epidermis of snakes. Shedding takes place along a shedding complex, which is composed of two layers, the clear and the oberhautchen layers. The remaining epidermis comprises different layers, some of which contain beta-keratins and others alpha-keratins. Weak loricrin, transglutaminase, and sometimes also iso-peptide-bond immunoreactivities are seen in some cells, lacunar cells, of the alpha-layer. Tritiated histidine is mainly incorporated in the shedding complex, especially in dense beta-keratin filaments in cells of the oberhautchen layer and to a small amount in cells of the clear layer. This suggests the presence of histidine-rich, matrix proteins among beta-keratin bundles. The latter contain sulfur and are weakly immunolabeled for beta-keratin at the beginning of differentiation of oberhautchen cells. After merging with beta cells, the dense beta-keratin filaments of oberhautchen cells become immunopositive for beta-keratin. The uptake of histidine decreases in beta cells, where little dense matrix material is present, while pale beta-keratin filaments increase. During maturation, little histidine labeling remains in electron-dense areas of the beta layer and in those of oberhautchen spinulae. Some roundish dense granules of oberhautchen cells rich in sulfur are negative to antibodies for alpha-keratin, beta-keratin, and loricrin. The granules eventually merge with beta-keratin, and probably contribute to the formation of the resistant matrix of oberhautchen cells. In conclusion, beta-keratin, histidine-rich, and sulfur-rich proteins contribute to form snake microornamentations. J. Morphol. © 2005 Wiley-Liss, Inc. [source] Mineralized dermal layer of the Brazilian tree-frog Corythomantis greeningiJOURNAL OF MORPHOLOGY, Issue 1 2001E. Katchburian Abstract Some species of anuran amphibians possess a calcified dermal layer (the Eberth-Kastschenko layer) located between the "stratum spongiosum" and the "stratum compactum." This layer consists of calcium phosphate deposits, proteoglycans, and glycosaminoglycans. Although regarded as a protective layer against desiccation, a calcium reservoir, or possibly a remnant of a dermal skeleton present in anuran ancestors, very little is known about its origin, structure, and function. Thus, we studied the structure and composition of the mineralized dermal layer of Corythomantis greeningi, a peculiar hylid from the Brazilian semiarid region (caatinga), using conventional and cryosubstitution methods combined with transmission, scanning, and analytical electron microscopy. Results show that the dermal layer consists of dense, closely juxtaposed, globular structures. Although the electron opacity of the globules was variable, depending on the type of preparation, crystal-like inclusions were present in all of them, as confirmed by dark field microscopy. Electron probe X-ray microanalysis showed calcium, phosphorus, and oxygen, and electron diffraction revealed a crystalline structure comparable to that of a hydroxyapatite. J. Morphol. 248:56,63, 2001. © 2001 Wiley-Liss, Inc. [source] Preparation and Optical Property of Glass Ceramics Containing Ruby CrystalsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Jumpei Ueda We have developed the glass ceramics containing ruby crystals by heat treatment of a Cr3+ -doped SiO2,Al2O3,Y2O3 glass at 1550°C. The shape of precipitated crystals in the glass matrix was rod type whose average width and length were around 10 and 200 ,m, respectively. From an X-ray diffraction measurement and an electron probe X-ray microanalysis, it was confirmed that the rod crystals were ,-Al2O3. Intense emission bands of Cr3+ at 694 nm, called the R -lines, were observed in the glass ceramics heat treated above 1300°C. In addition, the intense red luminescence was observed only in the ,-Al2O3 rod crystals by a photoluminescence mapping image. [source] Synthesis of Mixed Conducting Ceramic Oxides SrFeCo0.5Oy Powder by Hybrid Microwave HeatingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2002Di Huo Mixed conducting ceramic oxide SrFeCo0.5Oy powders were prepared by a conventional solid-state reaction method and two types of hybrid microwave heating methods. XRD, SEM/EDS (energy-dispersive spectroscopy), and TEM/EDX (energy-dispersive X-ray microanalysis) were used to characterize the products. The conventional heated sample is a three-phase mixture composed of a predominant orthorhombic Sr4(Fe1,xCox)6O13±, phase, a cubic perovskite SrFe1,xCoxO3,, phase, and a CoO phase. Phase components of the direct hybrid heated samples are similar to those of the conventional heated sample, except that its predominant phase is a cubic perovskite SrFe1,xCoxO3,, phase other than the orthorhombic Sr4(Fe1,xCox)6O13±, phase. The indirect hybrid heated sample is mainly composed of a cubic perovskite Sr(Fe,Co)1.5Oy phase, with a trace amount of orthorhombic phase and spinel (Fe,Co) oxides. The cobalt content of the Sr(Fe,Co)1.5Oy phase is much higher than that of the SrFe1,xCoxO3,, phase. Particle size distribution of the conventional heated sample is very wide. The indirect hybrid heated sample has a relatively narrow particle size distribution, with an average particle size of 3,4 ,m, but the particles stick to form agglomerates. The morphology of the direct hybrid heated sample is similar to that of the conventional heated sample, except that submicrometer grade particles were rarely observed. [source] Zinc Vanadates in Vanadium Oxide-Doped Zinc Oxide VaristorsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2001Huey-Hoon Hng Convergent-beam electron diffraction has been used to determine the space groups of ,- and ,-Zn3(VO4)2 particles in vanadium oxide-doped zinc oxide varistors. The crystal structure of ,-Zn3(VO4)2 has been determined to be monoclinic with space group P21 and lattice parameters of a= 9.80 Å, b= 8.34 Å, c= 10.27 Å, and ,= 115.8°, whereas that of ,-Zn3(VO4)2 is monoclinic with space group Cm and a= 10.40 Å, b= 8.59 Å, c= 9.44 Å, and ,= 98.8°. Energy-dispersive X-ray microanalysis of these two phases shows significant deviations from their expected stoichiometry. It is apparent that the ,-phase is, in fact, the metastable Zn4V2O9 phase, whereas the ,-phase either is a new oxide that consists of zinc, vanadium, and manganese or, more likely, is a zinc vanadate phase with a Zn:V atomic ratio of 1:1 that has the ability to go into solid solution with manganese. [source] Preservation of mouse liver tissue during cold storage in experimental solutions assessed by x-ray microanalysisLIVER TRANSPLANTATION, Issue 3 2003Inna Kozlova The increasing use of organs for transplantation necessitates the development of optimal preservation techniques. The goal of this study was to investigate changes in elemental content in mouse liver cells during cold storage by x-ray microanalysis in parallel with morphologic studies. Tissue was stored at 4°C for 4 to 12 hours in normal Krebs-Ringer solution (high sodium/potassium ratio), modified Krebs-Ringer solution (low Na+/K+ ratio), Euro-Collins solution, University of Wisconsin (UW) solution, or seven modified versions of the UW solution. Incubation of liver in normal Krebs-Ringer solution caused a significant increase in sodium and decrease in potassium concentrations in contrast to incubation in other solutions. The concentration of sodium, potassium, and chlorine in the cells closely followed the concentration in the storage solution, indicating that the intracellular concentration of these ions during storage is entirely dependent on diffusion processes. The calcium concentration was independent of the storage solution used. Studies by light and transmission electron microscopy showed good preservation of hepatocytes after storage for 8 and 12 hours in UW solution and its variants, modified Krebs-Ringer solution and Euro-Collins solution, but showed moderate damage to mitochondria and swelling of the endoplasmic reticulum in normal Krebs-Ringer solution. In addition, damage to the sinusoidal endothelial cells was observed after 4 hours in normal Krebs-Ringer solution and after 8 to 12 hours in the other solutions. In conclusion, the only factor determining the intracellular concentration of diffusible ions after cold tissue storage is the ionic composition of the extracellular medium. X-ray microanalysis provides an objective method for assessing whether the intracellular ionic composition of tissue is maintained during storage. [source] Dust from comet Wild 2: Interpreting particle size, shape, structure, and composition from impact features on the Stardust aluminum foilsMETEORITICS & PLANETARY SCIENCE, Issue 1-2 2008A. T. Kearsley By comparison to laboratory shots of known particle dimensions and density, using the same velocity and incidence geometry as the Stardust Wild 2 encounter, we can derive size and mass of the cometary dust grains. Using scanning electron microscopy (SEM) of foil samples (both flown on the mission and impacted in the laboratory) we have recognized a range of impact feature shapes from which we interpret particle density and internal structure. We have documented composition of crater residues, including stoichiometric material in 3 of 7 larger craters, by energy dispersive X-ray microanalysis. Wild 2 dust grains include coarse (>10 ,m) mafic silicate grains, some dominated by a single mineral species of density around 3,4 g cm,3 (such as olivine). Other grains were porous, low-density aggregates from a few nanometers to 100 ,m, with an overall density that may be lower than 1 g cm,3, containing mixtures of silicates and sulfides and possibly both alkali-rich and mafic glass. The mineral assemblage is very similar to the most common species reported from aerogel tracks. In one large aggregate crater, the combined diverse residue composition is similar to CI chondrites. The foils are a unique collecting substrate, revealing that the most abundant Wild 2 dust grains were of sub-micrometer size and of complex internal structure. Impact residues in Stardust foil craters will be a valuable resource for future analyses of cometary dust. [source] Autopsy case of aluminum encephalopathyNEUROPATHOLOGY, Issue 3 2002Teruo Shirabe We report the case of a 59-year-old female aluminum encephalopathy patient who had chronic renal failure and took 3.0 g hydroxy-aluminum gel per day for the control of serum phosphorus level during a 15-year period. Nine months before her death she developed disorientation, memory disturbance, emotional incontinence, general convulsions and consciousness disturbance. Neuropathologically, the brain showed nerve cell atrophy and mild loss with stromal spongiosis, proliferation of astrocytes and microglia in the cerebral cortex, basal ganglia and thalamus. Some nerve cells were stained immunohistochemically by phosphorylated neurofilament, but apparent neurofibrillary tangles were not observed. Aluminum was detected in the nerve cells of the cerebral cortex by X-ray microanalysis. Despite the long-term intake of aluminum, there were no neuropathological findings of Alzheimer's disease. The findings in our case suggested that aluminum alone might not develop Alzheimer's disease. [source] Role of phi cells and the endodermis under salt stress in Brassica oleraceaNEW PHYTOLOGIST, Issue 2 2009N. Fernandez-Garcia Summary ,,Phi cell layers were discovered in the 19th century in a small number of species, including members of the Brassicaceae family. A mechanical role was first suggested for this structure; however, this has never been demonstrated. The main objective of the present work was to analyse the ultrastructure of phi cells, their influence on ion movement from the cortex to the stele, and their contribution to salt stress tolerance in Brassica oleracea. ,,Transmission electron microscopy and X-ray microanalysis studies were used to analyse the subcellular structure and distribution of ions in phi cells and the endodermis under salt stress. Ion movement was analysed using lanthanum as an apoplastic tracer. ,,The ultrastructural results confirm that phi cells are specialized cells showing cell wall ingrowths in the inner tangential cell walls. X-ray microanalysis confirmed a build-up of sodium. Phi thickenings were lignified and lanthanum moved periplasmically at this level. ,,To the best of our knowledge, this is the first study reporting the possible role of the phi cells as a barrier controlling the movement of ions from the cortex to the stele. Therefore, the phi cell layer and endodermis seem to be regulating ion transport in Brassica oleracea under salt stress. [source] Phosphoglyceride (PG) crystal deposition disease: A novel acquired disease in which PG crystals are deposited in injured soft tissue and bone with phospholipid metabolism disturbancePATHOLOGY INTERNATIONAL, Issue 12 2004Katsutoshi Miura The clinical history and crystal characteristics of three published cases and three new cases of phosphoglyceride (PG) crystal deposition disease of soft tissues and bones were compared. All patients (age range, 51,64 years) were generally healthy without a genetic background of congenital immunodeficiency or lipidosis. Foreign body granulomas grew slowly, predominantly at postoperative or repeat injection lesions. In two cases, crystals were deposited in multiple locations, and in one case, lipophage accumulations were found in the bone marrow. The crystals characteristically dissolved in acetic acid with oxygen gas formation, easily dissolved in alkalis and showed positive staining for PG by the gold hydroxamic acid method. All crystals examined by infrared microscopy, mass spectrometry and X-ray microanalysis showed similar results, supporting the theory that the crystals were PG. Phosphoglyceride deposition disease is a lipid metabolic disorder in which PG crystals are slowly deposited, predominantly in injured soft tissues, forming foreign body granulomas. The diagnosis can be based on histological characteristics. The prognosis is favorable, although some cases showed systemic depositions with repetitions. Lysosomal phosphoglyceride metabolism in macrophages might be affected. [source] Photodynamic Effects of Antioxidant Substituted Porphyrin Photosensitizers on Gram-positive and -negative Bacteria,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2003Helena Ashkenazi ABSTRACT Photodynamic treatment of the gram-negative bacteria Escherichia coli B and Acinetobacter baumannii and the gram-positive bacterium Staphylococcus aureus was performed using two newly devised and synthesized antioxidant carrier photosensitizers (antioxidant carrier sensitizers-2 [ACS-2] and antioxidant carrier sensitizers-3 [ACS-3]), which are butyl hydroxy toluene and propyl gallate substituted haematoporphyrins, respectively. It was found that ACS-2 is less reactive than other photosensitizers previously used for the same purpose, whereas ACS-3 is very effective against the multidrug-resistant bacterium A. baumannii, causing its complete eradication at a low fluence (,7.5 J/cm) of blue light (407,420 nm) and a low concentration (10 ,M). At a higher fluence (,37.5 J/cm) complete eradication of E. coli B can be obtained under the same conditions. Furthermore, X-ray microanalysis and ultrastructural changes indicate that ACS-3, especially in the case of photodynamic treatment of A. baumannii, interferes with membrane functions and causes the inactivation of the bacterium. ACS-3 may be suggested as a specific photosensitization agent for photoinactivation of gram-negative bacteria. [source] Cathodoluminescence spectral mapping of III-nitride structuresPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2004R. W. Martin Abstract The application of cathodoluminescence spectral mapping to the characterisation of a range III-nitride semiconductor structures is described. Details are presented of the instrumentation developed to carry out such measurements using an electron probe micro-analyser. The spatial resolution of the luminescence data is ,100 nm. The technique is enhanced by the ability to simultaneously perform X-ray microanalysis and electron imaging. Results are presented from epitaxially laterally overgrown GaN and InGaN/GaN structures using both single-layer SiO2 and multilayer SiO2/ZrO2 masks. Effects of strain and microcavity formation are resolved. Application of the technique to InGaN epilayers shows spatially-dependent shifts in the peak wavelength of the luminescence spectrum which correlate directly with microscopic variations in the indium content. Regions emitting at lower energy and with decreased intensity are shown to have higher InN contents, mirroring equivalent macroscopic observations. Finally the spectral mapping technique is used to analyse the luminescence from micron-scale selectively grown III-N pyramids, indicating possible formation of quantum dots at the sharp tips. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Silicification in sorghum (Sorghum bicolor) cultivars with different drought tolerancePHYSIOLOGIA PLANTARUM, Issue 1 2002Alexander Lux Sorghum belongs to a group of economically important, silicon accumulating plants. X-ray microanalysis coupled with environmental scanning electron microscopy (ESEM) of fresh root endodermal and leaf epidermal samples confirms histological and cultivar specificity of silicification. In sorghum roots, silicon is accumulated mostly in endodermal cells. Specialized silica aggregates are formed predominantly in a single row in the form of wall outgrowths on the inner tangential endodermal walls. The density of silica aggregates per square mm of inner tangential endodermal cell wall is around 2700 and there is no significant difference in the cultivars with different content of silicon in roots. In the leaf epidermis, silicon deposits were present in the outer walls of all cells, with the highest concentration in specialized idioblasts termed ,silica cells'. These cells are dumb-bell shaped in sorghum. In both the root endodermis and leaf epidermis, silicification was higher in a drought tolerant cultivar Gadambalia compared with drought sensitive cultivar Tabat. Silicon content per dry mass was higher in leaves than in roots in both cultivars. The values for cv. Gadambalia in roots and leaves are 3.5 and 4.1% Si, respectively, and for cv. Tabat 2.2 and 3.3%. However, based on X-ray microanalysis the amount of Si deposited in endodermal cell walls in drought tolerant cultivar (unlike the drought susceptible cultivar) is higher than that deposited in the leaf epidermis. The high root endodermal silicification might be related to a higher drought resistance. [source] Silicon deposition in the root reduces sodium uptake in rice (Oryza sativa L.) seedlings by reducing bypass flowPLANT CELL & ENVIRONMENT, Issue 10 2006H. J. GONG ABSTRACT Sodium chloride reduces the growth of rice seedlings, which accumulate excessive concentrations of sodium and chloride ions in their leaves. In this paper, we describe how silicon decreases transpirational bypass flow and ion concentrations in the xylem sap in rice (Oryza sativa L.) seedlings growing under NaCl stress. Salt (50 mM NaCl) reduced the growth of shoots and roots: adding silicate (3 mM) to the saline culture solution improved the growth of the shoots, but not roots. The improvement of shoot growth in the presence of silicate was correlated with reduced sodium concentration in the shoot. The net transport rate of Na from the root to shoot (expressed per unit of root mass) was also decreased by added silicate. There was, however, no effect of silicate on the net transport of potassium. Furthermore, in salt-stressed plants, silicate did not decrease the transpiration, and even increased it in seedlings pre-treated with silicate for 7 d prior to salt treatment, indicating that the reduction of sodium uptake by silicate was not simply through a reduction in volume flow from root to shoot. Experiments using trisodium-8-hydroxy-1,3,6-pyrenetrisulphonic acid (PTS), an apoplastic tracer, showed that silicate dramatically decreased transpirational bypass flow in rice (from about 4.2 to 0.8%), while the apparent sodium concentration in the xylem, which was estimated indirectly from the flux data, decreased from 6.2 to 2.8 mM. Direct measurements of the concentration of sodium in xylem sap sampled using Philaenus spumarius confirmed that the apparent reduction was not a consequence of sodium recycling. X-ray microanalysis showed that silicon was deposited in the outer part of the root and in the endodermis, being more obvious in the latter than in the former. The results suggest that silicon deposition in the exodermis and endodermis reduced sodium uptake in rice (Oryza sativa L.) seedlings under NaCl stress through a reduction in apoplastic transport across the root. [source] Root structure and cellular chloride, sodium and potassium distribution in salinized grapevinesPLANT CELL & ENVIRONMENT, Issue 6 2003R. STOREY ABSTRACT X-ray microanalysis was used to study the patterns of K+, Na+ and Cl, accumulation in salinized (25 mm NaCl) and non-salinized grapevine (Vitis) roots. The aim was to determine whether NaCl affects patterns of Cl, accumulation differentially in the roots of a Cl, -excluding genotype and a non-excluding genotype. Two regions of fibrous roots were analysed: (1) a region 2,3 mm basipetal to the root tip; and (2) a region of the root 10,12 mm basipetal to the root tip where the outermost layer is the hypodermis. The ion contents of the hypodermis, cortex, endodermis and pericycle vacuoles were analysed. Data were also collected from the cytoplasm of the endodermal and pericycle cells. The analyses showed that the ion profiles of the hypodermis and the endodermis were significantly different from those of the cortex and pericycle. The hypodermis and endodermis had higher K+ and lower Na+ and Cl, than surrounding cells. Some changes due to salinity such as increased K+ concentrations in the hypodermis were also noted. Chloride concentrations did not differ between the genotypes in the hypodermis, across the cortex or in the endodermis, but were higher in the pericycle of the excluder in comparison with the non-excluding genotype. However, K+/Na+ ratios of the cortex and endodermis were higher in the excluder. The pericycle cells exhibited the greatest ability to sequester Na+ and Cl, in vacuoles. Overall the data show cell-type-specific ion accumulation patterns and small but significant differences were found between genotypes. The possibility that these accumulation patterns arise from differences in uptake properties of cell types and/or result from the spatial distribution of the cell types along the competing symplastic and apoplastic ion transport pathways across the root is discussed. [source] Extracellular complexation of Cd in the Hartig net and cytosolic Zn sequestration in the fungal mantle of Picea abies , Hebeloma crustuliniforme ectomycorrhizasPLANT CELL & ENVIRONMENT, Issue 11 2000B. Frey ABSTRACT Compartmentation of heavy metals on or within mycorrhizal fungi may serve as a protective function for the roots of forest trees growing in soils containing elevated concentrations of metals such as Cd and Zn. In this paper we present the first quantitative measurements by X-ray microanalysis of heavy metals in high-pressure frozen and cryosectioned ectomycorrhizal fungal hyphae. We used this technique to analyse the main sites of Cd and Zn in fungal cells of mantle and Hartig net hyphae and in cortical root cells of symbiotic Picea abies , Hebeloma crustuliniforme associations to gain new insights into the mechanisms of detoxification of these two metals in Norway spruce seedlings. The mycorrhizal seedlings were exposed in growth pouches to either 1 mM Cd or 2 mM Zn for 5 weeks. The microanalytical data revealed that two distinct Cd- and Zn-binding mechanisms are involved in cellular compartmentation of Cd and Zn in the mycobiont. Whereas extracellular complexation of Cd occurred predominantly in the Hartig net hyphae, both extracellular complexation and cytosolic sequestration of Zn occurred in the fungal tissue. The vacuoles were presumed not to be a significant pool for Cd and Zn storage. Cadmium was almost exclusively localized in the cell walls of the Hartig net (up to 161 mmol kg,1 DW) compared with significantly lower concentrations in the cell walls of mantle hyphae (22 mmol kg,1 DW) and in the cell walls of cortical cells (15 mmol kg,1 DW). This suggests that the apoplast of the Hartig net is a primary accumulation site for Cd. Zinc accumulated mainly in the cell walls of the mantle hyphae (111 mmol kg,1 DW), the Hartig net hyphae (130 mmol kg,1 DW) and the cortical cells (152 mmol kg,1 DW). In addition, Zn occurred in high concentrations in the cytoplasm of the fungal mantle hyphae (up to 164 mmol kg,1 DW) suggesting that both the cell walls and the cytoplasm of fungal tissue are the main accumulation sites for Zn in P. abies resulting in decreased Zn transfer from the fungus to the root. [source] Ultrastructural Evidence for a Novel Accumulation of Ca in a Microbial Mat from a Slight Acidic Hot SpringACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2010Xiaotong PENG Abstract: Microbial mats are ecosystems that can control or induce the precipitation of calcium (Ca) carbonate on Earth through geological time. In the present study, we report on a novel accumulation of Ca, together with iron (Fe), in a microbial mat collected from a slight acidic hot spring (pH=5.9) in south China. Combining an array of approaches, including environmental scanning electron microscopy, X-ray microanalysis, transmission electron microscopy, and selected area electron diffraction, we provide ultrastructral evidence for amorphous acicular aggregates containing Ca and Fe associated with cyanobacteria precipitating in the microbial mats. Cyanobacterial photosynthesis and exopolymeric organic matrixes are considered to be responsible for the precipitation of Ca. These amorphous acicular aggregates might imply the early stage of calcification occurring in microbial mats. Ca and Fe coprecipitation indicates another potential important way of inorganic element precipitation in hot spring microbial mats. Our results provide insight into the possible mechanism of cyanobacterial calcification and microfossil preservation in slight acidic hot spring environments. [source] Preservation of mouse liver tissue during cold storage in experimental solutions assessed by x-ray microanalysisLIVER TRANSPLANTATION, Issue 3 2003Inna Kozlova The increasing use of organs for transplantation necessitates the development of optimal preservation techniques. The goal of this study was to investigate changes in elemental content in mouse liver cells during cold storage by x-ray microanalysis in parallel with morphologic studies. Tissue was stored at 4°C for 4 to 12 hours in normal Krebs-Ringer solution (high sodium/potassium ratio), modified Krebs-Ringer solution (low Na+/K+ ratio), Euro-Collins solution, University of Wisconsin (UW) solution, or seven modified versions of the UW solution. Incubation of liver in normal Krebs-Ringer solution caused a significant increase in sodium and decrease in potassium concentrations in contrast to incubation in other solutions. The concentration of sodium, potassium, and chlorine in the cells closely followed the concentration in the storage solution, indicating that the intracellular concentration of these ions during storage is entirely dependent on diffusion processes. The calcium concentration was independent of the storage solution used. Studies by light and transmission electron microscopy showed good preservation of hepatocytes after storage for 8 and 12 hours in UW solution and its variants, modified Krebs-Ringer solution and Euro-Collins solution, but showed moderate damage to mitochondria and swelling of the endoplasmic reticulum in normal Krebs-Ringer solution. In addition, damage to the sinusoidal endothelial cells was observed after 4 hours in normal Krebs-Ringer solution and after 8 to 12 hours in the other solutions. In conclusion, the only factor determining the intracellular concentration of diffusible ions after cold tissue storage is the ionic composition of the extracellular medium. X-ray microanalysis provides an objective method for assessing whether the intracellular ionic composition of tissue is maintained during storage. [source] | ||||||||||||||||||||||