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F C Driessens

Publications and source records attributed to F C Driessens.

137 records · Page 8Linked to original sources
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[Maturation of mammalian bone minerals. A new method for determining bone metabolism].

The present report begins by comparing data on bone mineralization communicated in the literature to date with the authors' own previously published concept of the "three-phase model". The age-dependent accumulation of minerals in the femurs of Wistar rats was also chemically-analytically investigated. The results suggest that the mineral first formed is octacalcium phosphate. It is followed by sodium- and magnesium-containing phases. Maturation of octacalcium phosphate only occurs after this; it is converted into a highly carbon-deficient hydroxyapatite. During this conversion the molar Ca/P ratio rises from 1.33 to 2. However, the final value of 2 is not fully attained: this is attributable to the "turnover" activity of bone-metabolic processes. The paper concludes with a discussion of how the newly developed chemical method of determining bone turnover can be used to determine its vitality.

Animals↗
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Evidence for intermediate metastable states during equilibration of bone and dental tissues.

Experimental data were collected on the solubility equilibrium of the mineral of bone, tooth enamel and calcium phosphate renal stones. Evaluation in the form of potential diagrams of Ca(OH)2 versus H3PO4 shows that Ca/P ratios of 1, 4/3, 10/7, 3/2 and 5/3, related to phases like brushite, octocalcium phosphate, whitlockite, defective apatite and hydroxyapatite respectively can be important. These facts allow the interpretation that many of these calcium phosphates are present simultaneously in biominerals or that they are formed during the equilibration.

Adult↗
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Probable phase composition of the mineral in bone.

Formulas proposed for the mineral of bone were reviewed. Literature data were collected where Ca, P, Na, Mg and CO3 are determined in the same samples. These data were analyzed for their conformity to the above mentioned formulas. According to this analysis Mg is contained in a phase having the Ca/P of magnesium whitlockite within the limites of error. Na is contained in a carbonated calcium phosphate phase which is analogy with synthetic systems must have the apatite structure. The Ca/P ratio of the remaining "rest phase" is 2. This is based on the composition of 101 bone mineral samples taken from fishes, reptiles, amphibians, birds and mammals. The CO3 content of the bone samples agrees with the formula Ca8 (PO4)4 (CO3) (OH)2 . X H2O for the "rest phase" within the limits of experimental error. Such a compound has, however, not been found in synthetic systems. Human bone contains about 15% magnesium whitlockite, 25% of the Na and CO3 containing apatite and the rest is the carbonated calcium phosphate with Ca/P = 2. It is presumed that this compound has a structure similar to that of octo calcium phosphate and that most of the citrate ions which always occur in bone mineral samples are incorporated in that phase.

Animals↗
PubMedDate not supplied

Degree of saturation of blood plasma in vertebrates with octocalcium phosphate.

In previous papers it has been shown that octocalcium phospate OCP occurs in bone mineral of vertebrates. Although this compound is not stable, there is a continuous new-formation of OCP due to bone turnover. Literature data of the calcium and phosphate concentrations in the blood plasma of vertebrates were collected and the degree of saturation with OCP was calculated. The results show that blood plasma of vertebrates is almost saturated with OCP. This fact indicates that OCP is the solubility controlling phase in the mineral of vertebrates. Further it verifies the expectation based on physicochemical theory that the interaction between body fluids and bone mineral is important in the calcium and phosphate homeostasis.

Animals↗