Tissues mineralized

Rosenthal, H.L., Eves, M.M. and Cochran, O.A. 1970 Common strontium of mineralized tissues from marine and sweet water animals. Comparative Biochemistry and Physiology 32 445 50. 

Inherent in all these methodologies, which measure either absolute Sr levels or strontium isotope ratios in mineralized tissue, is the assumption that diagenesis has not altered the signal since death. This has been a matter of some considerable debate (e.g., Nelson et al. 1986), but the consensus of current opinion amongst practitioners is that the repeated acid-washing procedures used remove any diagenetic mineral, because it has a higher... 

Bone and teeth in mammals and bony fishes all rely on calcium phosphates in the form of hydroxyapatite [Ca5(P04)30H]2, usually associated with around 5% carbonate (and referred to as carbonated apatite). The bones of the endoskeleton and the dentin and enamel of teeth have a high mineral content of carbonated apatite, and represent an extraordinary variety of structures with physical and mechanical properties exquisitely adapted to their particular function in the tissue where they are produced. We begin by discussing the formation of bone and then examine the biomineralization process leading to the hardest mineralized tissue known, the enamel of mammalian teeth. 

Skulan J, DePaolo DJ, Owens TL (1997) Biological control of calcium isotopic abundances in the global calcium cycle. Geochim Cosmochim Acta 61 2505-2510 Skulan J, DePaolo DJ (1999) Calcium isotope fractionation between soft and mineralized tissues as a monitor of calcium use in vertebrates. Proc Nat Acad Sci 96 13,709-13,713... 

Contradictory reports on different cross-link contents of mineralized and non-mineralized collagen from mineralized tissues have appeared (Banes et ah, 1983 Wu and Eyre, 1988). A role for cross-linking in inhibiting mineralization has been postulated (Yamauchi and Katz, 1993). 

Dumas J, Hurion N, Weill R and Keil B (1985) Collagenase in mineralized tissues of human teeth. FEBS Lett 187, 51-55. 

Mechanic GL, Gallop PM and Tanzer ML (1971) The nature of crosslinking in collagens from mineralized tissues. Biochem Biophys Res Comm 45, 644-653. 

Wrenn ME, Singh NP, Paschoa AS, et al. 1985. Concentrations of uranium and thorium isotopes in uranium millers and miners tissues. NTIS NUREG/CR-4382/GAR, 1-47. 

Fluoride is a cumulative toxin, which accumulates in mineralized tissues, notably in the lattice of bone and tooth crystals [8,39]. The biological effects in humans due to chronic fluoride ingestion depend not only on the total dosage and duration of exposure, but also on associated factors such as nutritional status, functional status of the renal tissue and interaction with other trace elements [41]. The effect of... 

A variety of diseases can affect bone and its structure. Paget s disease, for example, is a disorder arising from abnormal osteoclasts, characterized by exeessive bone resorption followed by replacement of the normal mineralized bone with structurally weak, poorly mineralized tissue. However, the most important bone disease is osteoporosis. This is a skeletal bone disease characterized hy microarchitectural deterioration of bony tissue and loss of bone mass, yielding increased susceptibility to bone fracture and bone fragility. In the United States, osteoporosis results in 1.5 million hone fractures annually, with 250,000 of these being hip fractures that sometimes ultimately culminate in patient death. There is a variety of therapies for the prevention and treatment of osteoporosis. 

In contrast to soft biologies, whose mechanical properties primarily depend upon the orientation of collagen fibers, the mechanical properties of mineralized tissues, or hard biologies, are more complicated. Factors such as density, mineral content, fat content, water content, and sample preservation and preparation play important roles in mechanical property determination. Specimen orientation also plays a key role, since most hard biologies such as bone are composite structures. For the most part, we will concentrate on the average properties of these materials and will relate these values to those of important, man-made replacement materials. 

Although about 80—90 percent of the total citric acid in humans are localized in hard tissues as enamel, dentine, cementum and bones, very little is known on the biological function of citric acid in biocalcification. HA crystals are reported to be dissolved by the action of citric acid. The acid dissolves the crystals in such a way that the destruction is a preferential attack along the c-axis. It is highly probable that the HA crystallites present in mineralized tissues also do have a dislocation in the centre of the material 165). Another assumption describes that citric acid is a constituent of the aqueous phase of enamel or that citrate is bound to the surface of apatite by adsorption166). 

Matrices of mineralized tissues may be subdivided 67) into (a) permanent ones which (4a) remain within the tissue, continuing to enclose the inorganic phase (e. g. mineralized keratins, bone, cementum, shells and dentine) and (b) temporary matrices which (4b) eventually leave the inorganic crystallites in a comparatively unprotected state, exposed to the influence of the external environment (e. g. dental enamel). 

Common features of mineralized tissues in the invertebrates are the following characteristics ... 

A third problem with the mitochondrial theory of biomineralization is that many mineralized tissues contain carbonate rather than phosphate. Since bicarbonate ions do not pass across mitochondrial membranes with any ease, it has now been shown that in phosphate-free buffers, calcium will enter mitochondria if dissolved carbon dioxide is available. It appears that some mitochondria possess carbonic an-hydrase activity on the inner membrane or in the mitochondrial matrix and are thus able to synthesize bicarbonate within the organelle. In such cases, inhibitors of carbonic anhydrase block the accumulation of calcium and carbonate ions622) since crystals of calcite have been identified in the mitochondria of earthworms calci-ferous glands623. These cells freqently showed spherical granules in the cytoplasm and lumen of the glands during phases of mineral secretion and it was suggested that they were aspects of cellular breakdown which occurred at these times. 

Shapiro, I. M. The phospholipids of mineralized tissues. I. Mammalian compact bone. Calc. Tiss. Res. 5, 21 (1970)... 

Leaver, A. G., Eastoe, J. E., Hartles, R. L. Citrate in mineralized tissues. II. The isolation from human dentine of a complex containing citric acid and a peptide. Arch, oral Biol. 2, 120 (1960)... 

Glimcher, M. J. Molecular biology of mineralized tissues with particular reference to bone. Rev. modern Phys. 31, 359 (1959)... 

Looking at the literature in the field of biomineralization, one notices, that the majority of articles is descriptive in nature. On the basis of electron micrographs or thin section studies, the intricate relationships between mineral phase and organic matrix are investigated. Other papers deal with the chemical composition of the mineralized tissue and the minerals. Only a few authors address themselves to the question of metal ion transport mechanisms in cellular systems and the solid state principles involved in mineral deposition on organic substrates. All three sets of information, however, are essential to understand calcification processes. It appears, therefore, that information on the functionality of metal ions in living systems and their role in mineral deposition are particularly desired in this area of research. 

The amount of organic matter in skeletal material can be as low as 0.01 percent in some mollusc shells, and as high as 20 to 30 percent in vertebrate bones or teeth in a few isolated instances concentrations may go up to 90 percent. The origin, nature and function of mineralized tissues in calcification is only tentatively known. 

In Table 3, the geometric means of amino acids in mineralized tissues of a series of representative classes of organisms are sumarized217,218,22S). In spite of the diversity in the amino acid composition of the shell organic matter, all matrices have one property in common, that is, they contain functions that operate as an effective calcifying agent. 

The nature of mineral phases present in bone, dentin, enamel and other phosphatic tissues, and their mode of formation have been subjects of lively discussions among health scientists and crystallographers. Bioscientists most commonly accept the viewpoint that the inorganic phase of bones or teeth is principally hydroxyapatite, Caio(P04)6(OH)2, and deviation in Ca/P ratio from common hydroxyapatite (Ca/P = 1.667) observed in mineralized tissues is explained by the presence of amorphous phosphates. In contrast, many crystallographers favor the idea of carbonate apatite, i.e. dahllite, as the major crystalline phase in biophosphates and they doubt the existence of amorphous phases. The topic has been reviewed14,15,22,28, 37,44,47,348-358) no common consent has yet been reached. In the following an attempt is made to at least coordinate the controversial findings. 

In conclusions, many schemes have been developed for metal ion — phosphate — organic matter interactions in biomineralization. A variety of organic compounds of the kind present in mineralized tissues were found to coordinate calcium ions at neutral or functional sites and in many instances metal ion coordination was accompanied by the binding of phosphate. Although a wealth of information exists on the organic-inorganic interplay, data could not be reduced to a point where a simple model on biological mineralization could be formulated. 

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