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At least 1,063 records · Page 59Linked to original sources
PubMed1985

Effect of pyrophosphate and two diphosphonates on 45Ca and 32Pi uptake and mineralization by matrix vesicle-enriched fractions and by hydroxyapatite.

Inorganic pyrophosphate (PPi) and two diphosphonates, ethane-1-hydroxy-1, 1-diphosphonate (EHDP) and dichloromethylene diphosphonate (Cl2MDP), were found to inhibit in vitro mineralization induced by matrix vesicle-enriched fractions from chicken epiphyseal cartilage. Inhibitor concentrations from 0.20 to 20 microM caused a dosage-dependent decrease in 45Ca and 32Pi uptake by the vesicle fraction. These inhibitors were also tested in a hydroxyapatite (HA)-seeded system to help distinguish between effects on the mineral vs nonmineral portions of the vesicle fraction. The order of inhibition of the HA-seeded system was EHDP greater than PPi greater than Cl2MDP, except for inhibitor concentrations of 0.20 microM where EHDP was the least inhibitory. This variation may be due to differences in the binding of the inhibitors to HA crystals. In general, inhibition of HA mineralization was greatest during later time periods, whereas vesicle ion uptake was affected more during early stages of incubation. The differential effects of the three inhibitors were most obvious at the 2.0 microM concentration. With PPi substantial inhibition of HA-seeded mineralization was observed even in late stages of the study; in contrast, with time the vesicle fraction overcame this inhibition. This suggests that alkaline phosphatase, an enzyme notably enriched in matrix vesicles, catalyzed the hydrolysis of PPi, reducing its concentration to a level where mineralization could proceed. Our findings show that matrix vesicle-induced mineralization differs significantly from apatite-induced mineralization. The data support the concept that vesicle alkaline phosphatase acts, at least in part, to remove physiological crystal growth inhibitors.

Alkaline Phosphatase↗
PubMed1993

Mineral-matrix interactions in bone and dentin.

The bone, dentin, and cementum of the mature individual are comprised from a dense collagenous fiber network into which the carbonate-apatite mineral phase is deposited. It is hypothesized that a set of collagen-interactive acidic phosphoproteins are secreted by the osteoblasts, odontoblasts, and cementoblasts into the preformed collagenous matrix. These proteins then interact specifically with the collagen and nucleate apatite formation on and within the fibrils. These phosphoproteins may also regulate the morphology, rate of growth, and stability of the mineral phase crystals. The acidic matrix phosphoproteins may thus be considered as the crucial regulators of mineralization and tissue stability. In the dentin system, these regulatory proteins are synthesized, posttranslationally modified, and secreted in vesicles different from the collagen secretory vesicles. Mineralization occurs as the regulatory proteins are deposited on the preformed fibrils. This model requires testing in the bone system. In dentin, in the absence of tissue turnover, the resident phosphoproteins are degraded in situ over time, perhaps changing the properties of the tissue. Regulation of synthesis, secretory pathways and retention of integrity within the matrix are thus important areas for further investigation.

Amino Acid Sequence↗
PubMed1975

Mineralization of dentin, bone and tendon in vitro.

Bovin dentin, bone and tendon slices, and rat bone, readily mineralize to variable degrees after demineralization by (EDTA) at pH 7.4, but they fail to mineralize after dimeralzation with acetic acid (HAc) at pH3.0. The demineralized dentin, but neither bone nor tendon, contained organically bound phosphate. The EDTA-demineralized dentin contained less phosphate than HAc-demineralized dentin. HAc-demineralized rat dentin contained high levels of phosphate. Since the EDTA- and HAc-demineralized rat dentin contained widely different levels of phosphate, yet both mineralized, it was concluded that phosphoprotein had little effect on nucleation. The reason why HAc-demineralized tissue other than rat dentin failed to nucleate and mineralize was not clarified.

Acetates↗
PubMed2002

Calcium bioavailability in relation to bone health.

A well established stable isotope technique exists for measuring calcium absorption from single foods and meals, but the long term effects of calcium on bone health cannot be assessed from acute bioavailability studies. Bone health depends primarily on the degree of mineralization, measured as bone mineral density (BMD), and phenotypic variations depend on genetic and environmental factors including calcium supply. Since almost all retained calcium is used for bone mineralization and remodeling, BMD can be used as a long-term (> six months) marker of dietary calcium bioavailability. However, BMD is a very insensitive marker of calcium bioavailability, so its use in dietary intervention studies is restricted to periods of significant bone growth or loss. Biochemical markers of bone metabolism may be used to predict the overall bioavailability of dietary calcium over a shorter time period (> four weeks), but they have a high coefficient of variation, so may not be appropriate for some dietary intervention studies. A group of European laboratories is currently developing an alternative approach using a long-lived radioisotope (41Ca) to label bone calcium and to directly measure the rate of calcium loss from urinary excretion data. The efficiency of calcium absorption is inversely related to intake; whole body balance of the mineral is dependent on rates of absorption and excretion and limited by calcium-binding substances in the gut. Dietary data and indirect measures of bone health indicate that bioavailability is important when habitual intakes are low, especially during periods of bone growth or loss. Further research is required to quantify the effects of major dietary modulators of calcium balance on bone health and to understand their relationship with genetic and physiological variables.

Biological Availability↗
PubMed1979

The relationship between tooth mineralization and early radiographic evidence of the ulnar sesamoid.

The relationship between early radiographic evidence of calcification of the adductor sesamoid of the first metacarpophalangeal joint and the state of maturity of certain teeth was investigated. Data were obtained from the records of one hundred and forty children of Caucasoid origin, comprising ninety-three girls and forty-seven boys. Calcification of the adductor sesamoid was closely related to the completion of root mineralization of the mandibular canine prior to apical closure. No significant sex differences were noted in the state of maturation of the tooth in relation to this particular stage of skeletal development. Correlations among the remaining teeth studied were low, the distribution of calcification stages being widely dispersed with significant sex differences evident. Based on the findings of this study, the completion of root formation of the mandibular canine prior to apical closure may be used as a maturity indicator for the commencement of the circumpubertal growth spurt with a similar degree of confidence as the calcification of the adductor sesamoid of the thumb. It should be noted, however, that racial variations might exist in the relationship between the state of maturity of this tooth and the commencement of mineralization of the sesamoid. Caution should thus be exercised in the application of these findings to other racial groups.

Calcification, Physiologic↗
PubMed2006

The effect of feeding calcium- and phosphorus-deficient diets to broiler chickens during the starting and growing-finishing phases on carcass quality.

There is considerable data on the effect of reducing inorganic Ca and P in broiler finisher diets on carcass quality. However, there is limited information on the effect of reducing dietary Ca and P during the different phases of growout. Two experiments were conducted from 0 to 35 d in floor pens. In both experiments, at least 4 replicates per treatment (50 chicks per replicate) were used. Corn-soybean meal and soybean oil-based diets deficient in Ca and P were fed. During the starter phase (ST), from 0 to 18 d, chicks were fed a 23% CP diet containing 0.60% Ca and 0.47% total P (tP). During the grower-finisher phase (GF), from 19 to 35 d, birds were fed a 19% CP diet containing 0.30% Ca and 0.37% tP. A combination of 1,000 phytase units/kg of Natuphos phytase and 5 microg/kg of 1alpha-hydroxycholecalciferol (P + 1alpha) was supplemented to some of the feed during the ST and GF. Diets containing adequate Ca and P were also fed during the ST (0.90% Ca and 0.68% tP) and GF (0.80% Ca and 0.67% tP). The level of tibia ash and the incidence of bone disease were measured at 18 and 35 d. At the end of the experiments, birds were processed and evaluated for muscle hemorrhages and broken bones. In both experiments, broilers fed diets that were not P + 1alpha supplemented demonstrated poor bone mineralization, considerable leg problems, and a high incidence of broken bones after processing. Broilers fed P + 1alpha throughout had more broken clavicles and femurs compared with birds fed the adequate diets. Day-18 tibia ash was significantly correlated to broken tibias and femurs during processing. Day-35 tibia ash was better correlated to bloody breast meat than to broken bones. It is concluded that carcass quality depends on the levels of Ca and P fed and the age of the bird. Tibia ash, traditionally used as an indication of bone strength, was better correlated to the incidence of bloody breasts.

Aging↗
PubMed1963

UNMINERALIZED FOSSIL BACTERIA.

Unmineralized bacterial cells, mostly Micrococcus sp., but including also Streptococcus sp. and Actinomyces sp., were found in enormous numbers in lake beds of the Newark Canyon Formation of Early Cretaceous age, Eureka County, Nevada. The micrococci are black, and have an average diameter about 0.5 micro. Similar black micrococci (0.4 to 0.7 micro) were found in profusion in the bottom mud of Green Lake, New York. About 80 percent of this mud consists of minute idiomorphic calcite crystals and about 20 percent of these contain enormous numbers of the black micrococci. It is suggested that the Early Cretaceous bacterial cells owe their preservation to occlusion in calcite crystals that grew in a black, bacterial mud in a meromictic lake in which part of the Newark Canyon Formation accumulated.

Actinomyces↗