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The roles of annexins and alkaline phosphatase in mineralization process.

100%
Balcerzak M., Hamade E., Zhang L., Pikula S., Azzar G., Radisson J., Bandorowicz-Pikula J., Buchet R.
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2003
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vol. 50
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issue 4
1019-1038
EN
In this review the roles of specific proteins during the first step of mineralization and nucleation are discussed. Mineralization is initiated inside the extracellular organelles-matrix vesicles (MVs). MVs, containing relatively high concentrations of Ca2+ and inorganic phosphate (Pgi), create an optimal environment to induce the formation of hydroxyapatite (HA). Special attention is given to two families of proteins present in MVs, annexins (AnxAs) and tissue-nonspecific alkaline phosphatases (TNAPs). Both families participate in the formation of HA crystals. AnxAs are Ca2+- and lipid-binding proteins, which are involved in Ca2+ homeostasis in bone cells and in extracellular MVs. AnxAs form calcium ion channels within the membrane of MVs. Although the mechanisms of ion channel formation by AnxAs are not well understood, evidence is provided that acidic pH or GTP contribute to this process. Furthermore, low molecular mass ligands, as vitamin A derivatives, can modulate the activity of MVs by interacting with AnxAs and affecting their expression. AnxAs and other anionic proteins are also involved in the crystal nucleation. The second family of proteins, TNAPs, is associated with Pi homeostasis, and can hydrolyse a variety of phosphate compounds. ATP is released in the extracellular matrix, where it can be hydrolyzed by TNAPs, ATP hydrolases and nucleoside triphosphate (NTP) pyrophosphohydrolases. However, TNAP is probably not responsible for ATP-dependent Ca2+/phosphate complex formation. It can hydrolyse pyrophosphate (PPi), a known inhibitor of HA formation and a byproduct of NTP pyrophosphohydrolases. In this respect, antagonistic activities of TNAPs and NTP pyrophosphohydrolases can regulate the mineralization process.
2
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Fabrication and Characterization of Three Dimensional Electrospun Cortical Bone Scaffolds

100%
Andric T., Taylor B. L., Degen K. E., Whittington A. R., Freeman J. W.
Nanomaterials and the Environment
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2014
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vol. 2
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issue 1
EN
Bone is a composite tissue composed of an organic matrix, inorganic mineral matrix and water. Structurally, bone is organized into two distinct types: trabecular (or cancellous) and cortical (or compact) bone. Cortical bone is highly organized, dense and composed of tightly packed units or osteons whereas trabecular bone is highly porous and usually found within the confines of cortical bone. Osteons, the subunits of cortical bone, consist of concentric layers of mineralized collagen fibers. While many scaffold fabrication techniques have sought to replicate the structure and organization of trabecular bone, very little research focuses on mimicking the organization of native cortical bone. In this study we fabricated three-dimensional electrospun cortical scaffolds by heat sintering individual osteon-like scaffolds. The scaffolds contained a system of channels running parallel to the length of the scaffolds, as found naturally in the haversian systems of bone tissue. The purpose of the studies discussed in this paper was to develop a mechanically enhanced biomimetic electrospun cortical scaffold. To that end we investigated the appropriate mineralization and cross-linking methods for these structures and to evaluate the mechanical properties of scaffolds with varying fiber angles. Cross-linking the gelatin in the scaffolds prior to the mineralization of the scaffolds proved to help prevent channels of the osteons from collapsing during fabrication. Premineralization, before larger scaffold formation and mineralization, increased mineral deposition between the electrospun layers of the scaffolds. A combination of cross-linking and premineralization significantly increased the compressive moduli of the individual scaffolds. Furthermore, scaffolds with fibers orientation ranging between 15° and 45° yielded the highest compressive moduli and yield strength.
3
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Hydrochemistry and origin of principal major elements in the groundwater of the Béchar-Kénadsa basin in arid zone, South-West of Algeria

86%
Lachache S., Nabou M., Merzouguui T., Amroune A.
Journal of Water and Land Development
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2018
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issue 36
4
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Impaktyty struktury Kara, Ural Polarny

86%
Kosina R.
Acta Societatis Metheoriticae Polonorum
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2016
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vol. 7
45-58
EN
The Kara crater is located near the Kara Sea. Together with the Ust-Kara crater, both structures are considered a twin structure, which is rarely found on Earth. The Ust-Kara is an undersea crater, while the Kara was formed in sedimentary rocks, in wet tundra. This environment determines the distinct petrological characteristics of the Kara impactites. Large shatter cones are a characteristic feature of an impact crater. High- and low-temperature tagamites with variable amounts of melt or glass and with the fluidal texture of rocky clasts were described from the crater. The mineralization represented by pyrite and chalcopyrite occurs in the suevite breccias expressing variable amounts of glass fragments. A special feature of the Kara impactites is the presence of coal clasts and carbonate rocks as well as a secondary crystallization of calcite in the form of globules.
5
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The mechanism of phosphate bacteria in increasing the solubility of phosphorus in Indonesian Andisols

86%
Tamad, Maas A., Hanudin E., Widada J., Tamad, Maas A., Hanudin E., Widada J.
Journal of Water and Land Development
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2021
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issue 49
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