The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Melvin J Glimcher - One of the best experts on this subject based on the ideXlab platform.
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the solid calcium phosphate Mineral Phases in embryonic chick bone characterized by high voltage electron diffraction
Journal of Bone and Mineral Research, 2009Co-Authors: William J Landis, Melvin J GlimcherAbstract:The solid Mineral Phases of calcium-phosphate (Ca-P) in the long bones from embryonic chicks between the ages of 9 and 13 days have been examined by high voltage (1.0 MV) electron microscopy and electron micro-diffraction. The study was undertaken to identify the chemical and crystallographic nature of the inorganic Mineral Phase(s) prepared under conditions which significantly reduce artifacts of specimen preparation and microscopic examination of the tissues. Electron microdiffraction patterns of solid Mineral Phase particles in the osteoid matrices of the subperiosteal region of tibiae were principally those of poorly crystalline hydroxyapatite. In rare instances (less than 1% of the estimated volume of the Mineral Phase present in the zone of early Mineralization), relatively large single crystals were observed within clusters of hydroxyapatite. From calculations of both interplanar spacings and measurements of angular displacement of diffraction reflections from single crystal microdiffraction patterns, two distinct Phases other than hydroxyapatite were identified: brushite and β-tricalcium phosphate. A third Phase, resembling an apatite, remains unidentified. The results suggest that very small amounts of nonapatitic Phases of Ca-P exist in chicken bone tissue. No temporal relationship could be established between the nonapatitic and apatitic Phases. There is at present no evidence from this study to support the concept that nonapatitic Phases are precursors of a final apatitic Phase in bone.
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Structural studies of the Mineral Phase of calcifying cartilage.
Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research, 2009Co-Authors: C. Rey, K. Beshah, Robert G. Griffin, Melvin J GlimcherAbstract:The calcified cartilage of the epiphyseal growth plate of young calves has been studied by x-ray diffraction, Fourier transform infrared spectroscopy, magic angle 31P nuclear magnetic resonance spectroscopy, and chemical composition. The powdered tissue was separated by density centrifugation as a function of Mineral content and thus qualitatively of the age of the calcium-phosphorus Mineral Phase. The individual density centrifugation fractions were examined separately. X-ray diffraction of the samples, especially of the lowest density fractions, revealed very poorly crystalline apatite. Fourier transform infrared spectroscopy and 31P nuclear magnetic resonance spectroscopy revealed the presence of significant amounts of nonapatitic phosphate ions. The concentration of such nonapatitic phosphates increases during the early stages of Mineralization but then decreases as the Mineral content steadily rises until full Mineralization is achieved. The total concentration of carbonate ions was found to be much lower in calcified cartilage than in bone from the same organ (scapula). The carbonate ions are located in both A sites (OH−) and B sites (PO43-), with a distribution similar to that found in bone Mineral. However, discrepancies between infrared resolution factors of phosphate and carbonate bands are consistent with a heterogeneous distribution of carbonate ions in poorly organized domains of the solid Phase of calcium phosphate. These initial studies permit one to characterize the calcium phosphate Mineral Phase as a very poorly crystalline, immature calcium phosphate apatite, rich in labile nonapatitic phosphate ions, with a low concentration of carbonate ions compared with bone Mineral of the same animal, indeed from the bone of the same organ (scapula).
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The solid, calcium‐phosphate Mineral Phases in embryonic chick bone characterized by high‐voltage electron diffraction
Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research, 2009Co-Authors: Dosuk D. Lee, William J Landis, Melvin J GlimcherAbstract:The solid Mineral Phases of calcium-phosphate (Ca-P) in the long bones from embryonic chicks between the ages of 9 and 13 days have been examined by high voltage (1.0 MV) electron microscopy and electron microdiffraction. The study was undertaken to identify the chemical and crystallographic nature of the inorganic Mineral Phase(s) prepared under conditions which significantly reduce artifacts of specimen preparation and microscopic examination of the tissues. Electron microdiffraction patterns of solid Mineral Phase particles in the osteoid matrices of the subperiosteal region of tibiae were principally those of poorly crystalline hydroxyapatite. In rare instances (less than 1% of the estimated volume of the Mineral Phase present in the zone of early Mineralization), relatively large single crystals were observed within clusters of hydroxyapatite. From calculations of both interplanar spacings and measurements of angular displacement of diffraction reflections from single crystal microdiffraction patterns, two distinct Phases other than hydroxyapatite were identified: brushite and beta-tricalcium phosphate. A third Phase, resembling an apatite, remains unidentified. The results suggest that very small amounts of nonapatitic Phases of Ca-P exist in chicken bone tissue. No temporal relationship could be established between the nonapatitic and apatitic Phases. There is at present no evidence from this study to support the concept that nonapatitic Phases are precursors of a final apatitic Phase in bone.
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bone nature of the calcium phosphate crystals and cellular structural and physical chemical mechanisms in their formation
Reviews in Mineralogy & Geochemistry, 2006Co-Authors: Melvin J GlimcherAbstract:Calcium phosphate is the dominant solid Mineral Phase within the skeletal and dental tissues of vertebrates. This chapter concentrates on the structure and composition of the solid calcium inorganic orthophosphate (Ca–Pi) Phase in bone and the mechanisms that are thought to induce the onset of this Mineralization process as an example of biological Mineralization in general. It is important to recognize that the Ca–Pi Mineral Phase is deposited in a living tissue and is a substance that is continuously being synthesized, resorbed and replaced by the action of living cells. Therefore, the composition, structure and other properties of the solid Ca–Pi Mineral Phase will change in space and time, depending on the general body metabolism and the local cellular functions in specific regions of bone. Similar considerations arise in studies of the Mineralized tissues of invertebrates, where the crystals consist of various lattice arrangements of CaCO3 (calcite, aragonite, vaterite) deposited in hierarchical arrangement with the constituents of the ordered organic matrices. Furthermore, the nature of the Ca–Pi Phase in bone is significantly different from synthetic, highly crystallized and geological hydroxylapatites, which is reflected in the physical, structural properties and physiological functions of the biological apatites. This chapter is an attempt to summarize at least some of the historical background leading to the more recent research over the past several decades. The focus here is on investigations at the molecular and nano-scales, now possible both theoretically and experimentally, which have been applied to determine the “nature” of the solid Ca–Pi Mineral Phase of bone and other calcified vertebrate tissues from the inception of Mineralization to the changes that occur during crystal maturation (“crystal aging”) and the “normal” aging of the animal. The topics addressed below include an introduction to the basic concepts, relevant terminology and cellular events involved in bone …
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The Nature of the Mineral Phase in Bone: Biological and Clinical Implications
Metabolic Bone Disease and Clinically Related Disorders, 1998Co-Authors: Melvin J GlimcherAbstract:The subjects that will be presented in this chapter are: (1) The nature of the Mineral Phase in bone; that is, the chemical composition and crystal structure of the solid calcium-phosphate (Ca-P) Mineral Phase in bone, and the changes that occur in the Mineral Phase per se with time and maturation; (2) the relationship of these maturational changes which occur with time to the biological, physiological, and mechanical functions of the crystals and to Ca and P Mineral metabolism; and (3) the ultrastructural location of the Mineral Phase and its relationship to the basic underlying physical chemical mechanism responsible for the initiation of calcification.
Hugh Coe - One of the best experts on this subject based on the ideXlab platform.
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Online differentiation of Mineral Phase in aerosol particles by ion formation mechanism using a LAAP-TOF single-particle mass spectrometer
Atmospheric Measurement Techniques, 2018Co-Authors: Nicholas Marsden, Michael Flynn, James Allan, Hugh CoeAbstract:Abstract. Mineralogy of silicate Mineral dust has a strong influence on climate and ecosystems due to variation in physiochemical properties that result from differences in composition and crystal structure (Mineral Phase). Traditional offline methods of analysing Mineral Phase are labour intensive and the temporal resolution of the data is much longer than many atmospheric processes. Single-particle mass spectrometry (SPMS) is an established technique for the online size-resolved measurement of particle composition by laser desorption ionisation (LDI) followed by time-of-flight mass spectrometry (TOF-MS). Although non-quantitative, the technique is able to identify the presence of silicate Minerals in airborne dust particles from markers of alkali metals and silicate molecular ions in the mass spectra. However, the differentiation of Mineral Phase in silicate particles by traditional mass spectral peak area measurements is not possible. This is because instrument function and matrix effects in the ionisation process result in variations in instrument response that are greater than the differences in composition between common Mineral Phases. In this study, we introduce a novel technique that enables the differentiation of Mineral Phase in silicate Mineral particles by ion formation mechanism measured from subtle changes in ion arrival times at the TOF-MS detector. Using a combination of peak area and peak centroid measurements, we show that the arrangement of the interstitial alkali metals in the crystal structure, an important property in silicate Mineralogy, influences the ion arrival times of elemental and molecular ion species in the negative ion mass spectra. A classification scheme is presented that allowed for the differentiation of illite–smectite, kaolinite and feldspar Minerals on a single-particle basis. Online analysis of Mineral dust aerosol generated from clay Mineral standards produced Mineral fractions that are in agreement with bulk measurements reported by traditional XRD (X-ray diffraction) analysis.
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On-line differentiation of Mineral Phase in aerosol particles by ion formation mechanism using a LAAP-ToF single particle mass spectrometer
2017Co-Authors: Nicholas A. Marsden, Michael J. Flynn, James D. Allan, Hugh CoeAbstract:Abstract. Mineralogy of silicate Mineral dust has a strong influence on climate and eco-systems due to variation in physicochemical properties that result from differences in composition and crystal structure (Mineral Phase). Traditional off-line methods of analysing Mineral Phase are labour intensive and the temporal resolution of the data is much longer than many atmospheric processes. Single particle mass spectrometry (SPMS) is an established technique for the on-line size resolved measurement of particle composition by laser desorption ionisation (LDI) followed by time-of-flight mass spectrometry (TOF-MS). Although non-quantitative, the technique is able to identify the presence of silicate Minerals in airborne dust particles from markers of alkali metals and silicate molecular ions in the mass spectra. However, the differentiation of Mineral Phase in silicate particles by traditional mass spectral peak area measurements is not possible. This is because instrument function and matrix effects in the ionisation process result in variations in instrument response that are greater than the differences in composition between common Mineral Phases. In this study, a novel technique is introduced that enables the differentiation of Mineral Phase in silicate Mineral particles by ion formation mechanism measured from subtle changes in ion arrival times at the TOF-MS detector. Using a combination of peak area and peak centroid measurements, we show that the arrangement of the interstitial alkali metals in the crystal structure, an important property in silicate Mineralogy, influences the ion arrival times of elemental and molecular ion species in the negative ion mass spectra. A classification scheme is presented that allows for the differentiation of illite/smectite, kaolinite and feldspar Minerals on a single particle basis. On-line analysis of Mineral dust aerosol generated from clay Mineral standards produced Mineral fractions that are in agreement with bulk measurements reported by traditional XRD analysis.
Lia Addadi - One of the best experts on this subject based on the ideXlab platform.
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structural characterization of the transient amorphous calcium carbonate precursor Phase in sea urchin embryos
Advanced Functional Materials, 2006Co-Authors: Yael Politi, Yael Levikalisman, Fred H Wilt, Lia Addadi, Steve Weiner, Irit SagiAbstract:Sea urchin embryos form their calcitic spicular skeletons via a transient precursor Phase composed of amorphous calcium carbonate (ACC). Transition of ACC to calcite in whole larvae and isolated spicules during development has been monitored using X-ray absorption spectroscopy (XAS). Remarkably, the changing nature of the Mineral Phase can clearly be monitored in the whole embryo samples. More detailed analyses of isolated spicules at different stages of development using both XAS and infrared spectroscopy demonstrate that the short-range order of the transient ACC Phase resembles calcite, even though infrared spectra show that the spicules are mostly composed of an amorphous Mineral Phase. The coordination sphere is at first distorted but soon adopts the octahedral symmetry typical of calcite. Long-range lattice rearrangement follows to form the calcite single crystal of the mature spicule. These studies demonstrate the feasibility of real-time monitoring of Mineralized-tissue development using XAS, including the structural characterization of transient amorphous Phases at the atomic level.
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cellular control over spicule formation in sea urchin embryos a structural approach
Journal of Structural Biology, 1999Co-Authors: Elia Beniash, Lia Addadi, Stephen WeinerAbstract:Abstract The spicules of the sea urchin embryo form in intracellular membrane-delineated compartments. Each spicule is composed of a single crystal of calcite and amorphous calcium carbonate. The latter transforms with time into calcite by overgrowth of the preexisting crystal. Relationships between the membrane surrounding the spiculogenic compartment and the spicule Mineral Phase were studied in the transmission electron microscope (TEM) using freeze-fracture. In all the replicas observed the spicules were tightly surrounded by the membrane. Furthermore, a variety of structures that are related to the material exchange process across the membrane were observed. The spiculogenic cells were separated from other cell types of the embryo, frozen, and freeze-dried on the TEM grids. The contents of electron-dense granules in the spiculogenic cells were shown by electron diffraction to be composed of amorphous calcium carbonate. These observations are consistent with the notion that the amorphous calcium carbonate-containing granules contain the precursor Mineral Phase for spicule formation and that the membrane surrounding the forming spicule is involved both in transport of material and in controlling spicule Mineralization.
Irit Sagi - One of the best experts on this subject based on the ideXlab platform.
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structural characterization of the transient amorphous calcium carbonate precursor Phase in sea urchin embryos
Advanced Functional Materials, 2006Co-Authors: Yael Politi, Yael Levikalisman, Fred H Wilt, Lia Addadi, Steve Weiner, Irit SagiAbstract:Sea urchin embryos form their calcitic spicular skeletons via a transient precursor Phase composed of amorphous calcium carbonate (ACC). Transition of ACC to calcite in whole larvae and isolated spicules during development has been monitored using X-ray absorption spectroscopy (XAS). Remarkably, the changing nature of the Mineral Phase can clearly be monitored in the whole embryo samples. More detailed analyses of isolated spicules at different stages of development using both XAS and infrared spectroscopy demonstrate that the short-range order of the transient ACC Phase resembles calcite, even though infrared spectra show that the spicules are mostly composed of an amorphous Mineral Phase. The coordination sphere is at first distorted but soon adopts the octahedral symmetry typical of calcite. Long-range lattice rearrangement follows to form the calcite single crystal of the mature spicule. These studies demonstrate the feasibility of real-time monitoring of Mineralized-tissue development using XAS, including the structural characterization of transient amorphous Phases at the atomic level.
Stephen Weiner - One of the best experts on this subject based on the ideXlab platform.
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cellular control over spicule formation in sea urchin embryos a structural approach
Journal of Structural Biology, 1999Co-Authors: Elia Beniash, Lia Addadi, Stephen WeinerAbstract:Abstract The spicules of the sea urchin embryo form in intracellular membrane-delineated compartments. Each spicule is composed of a single crystal of calcite and amorphous calcium carbonate. The latter transforms with time into calcite by overgrowth of the preexisting crystal. Relationships between the membrane surrounding the spiculogenic compartment and the spicule Mineral Phase were studied in the transmission electron microscope (TEM) using freeze-fracture. In all the replicas observed the spicules were tightly surrounded by the membrane. Furthermore, a variety of structures that are related to the material exchange process across the membrane were observed. The spiculogenic cells were separated from other cell types of the embryo, frozen, and freeze-dried on the TEM grids. The contents of electron-dense granules in the spiculogenic cells were shown by electron diffraction to be composed of amorphous calcium carbonate. These observations are consistent with the notion that the amorphous calcium carbonate-containing granules contain the precursor Mineral Phase for spicule formation and that the membrane surrounding the forming spicule is involved both in transport of material and in controlling spicule Mineralization.
