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Biomedical subjects

F Betts

Publications and source records attributed to F Betts.

28 records · Page 2Linked to original sources
PubMed1988

Effect of gallium on bone mineral properties.

Gallium nitrate is biologically active in blocking bone resorption in vitro as well as in vivo. Administration of gallium nitrate to growing rats results in a dose-dependent accumulation of low levels of gallium in bone that is associated with specific changes in the mineral properties of bone. To elucidate in greater detail the changes induced by gallium, the properties of whole and density-fractionated bone samples from control and gallium-treated rats were examined. These studies showed that short-term treatment with gallium nitrate caused an increase in bone calcium and phosphate content. Devitalized bone powder from the gallium-treated rats was less soluble in acetate buffer and less readily resorbed by monocytes. Density fractionation analyses demonstrated that the largest proportion (76% by weight) of powdered metaphyseal bone particles from rats had a density of less than 2.15 g/cc. Following short-term treatment (14 days) with gallium nitrate (45 mg/kg body weight), a significant increase in the relative proportion of more dense bone (greater than or equal to 2.15 g/cc) was observed (24% for the control vs. 39% for the gallium-treated rats, P less than 0.01). In the diaphyseal samples, the largest proportion (88% by weight) of the bone powder had a density of greater than or equal to 2.15 g/cc. After short-term treatment with gallium, a slight decrease in mean diaphyseal particle density was observed. Measurement of calcium accretion with 45Ca in the gallium-treated rats demonstrated increased specific activity in the metaphyseal bone samples, densities = 2.0, 2.1, 2.15, and 2.25 g/cc; the difference was significant only for the 2.25 g/cc fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Mineral parameters in early fracture repair.

In an effort to define and characterize the initial mineralization product of fracture-healing, we studied the mineral components within a model of endochondral osseous repair. Fracture calluses from the tibiae of rats and rabbits undergoing endochondral fracture-healing were analyzed, in toto and following density fractionation, by physicochemical and crystallographic techniques. Significant changes in mineral composition, crystal size, and density occurred in the early phases of fracture repair. In the rat, two weeks after fracture, the calcium-to-phosphorus ratio was higher than that of the mineral component, possibly due to calcium-binding to some of the macromolecules known to be present. The earliest mineral was poorly crystallized hydroxyapatite with a high carbonate content. Crystal perfection improved rapidly and approached that of normal diaphyseal bone within eight weeks after endochondral fracture in both the rabbit and the rat.

Animals↗
PubMed1983

Amorphous calcium phosphate in casein micelles of bovine milk.

The calcium phosphate remaining after hydrazine deproteination of casein micelles isolated from bulk skim milk exhibits under the electron microscope a very fine and uniform granularity being formed by small subunits with a true diameter of approximately 2.5 nm. This material, which is about 10 percent by weight citrate, termed calcium phosphate citrate (CPC) complex, also contains Mg and Zn at molar ratios of 0.03 and 0.003 respectively. Radial distribution function (RDF) and infrared analyses show that CPC is a Mg-containing amorphous calcium phosphate (ACP) similar to synthetic and cytoplasmic ACP. presence of CPC in casein micelles as an amorphous colloid bonded with phosphoproteins provides the means for storing in milk large amounts of Ca (16 mM) and Pi (10 mM) in a readily utilizable form but at a higher ion concentration than found in biological solutions.

Animals↗
PubMed1981

Formation and structure of Ca-deficient hydroxyapatite.

When amorphous calcium phosphate (ACP) was transformed to crystalline hydroxyapatite (HA) in a series of aqueous slurry concentrations ranging from low to high, the higher slurry concentrations produced more Ca-deficient HA as measured by Ca/P ratio and heat-produced pyrophosphate. We feel that the excess solution phosphate produced in the higher slurry transformations results in lower Ca/P ratio HA. It has been suggested that an ACP is the precursor to bone apatite. Regulation of the in vivo ACP slurry concentration could then control the stoichiometry and, therefore, the metabolic activity of bone apatite. X-ray radial distribution function (RDF) analyses showed that CO3(2-) substitution in HA creates far greater structural distortions than do Ca deficiencies. The latter, however, do produce small, but observable, structural distortions when compared to stoichiometric HA. It now seems clear that the RDF of bone apatite can be modeled by a synthetic, Ca-deficient, CO3(2-)-containing HA.

Calcium↗
PubMed1975

Effect of carbonate and biological macromolecules on formation and properties of hydroxyapatite.

Amorphous calcium phosphate (ACP) was transformed at 25 degrees to hydroxyapatite (HA) in horse and bovine serum; solutions of serum-protein fractions in tris-HC1 buffer (pH 7.4), and pH 7.4 buffers containing from 0.1 to 10 times physiological CO3(2-) concentration. The ACP-to-HA transformation was slower in whole serum and serum fractions than in control buffer solution. The observed adsorption of serum proteins on ACP and HA probably inhibits both the dissolution of the ACP particles and the growth of HA crystals. After 72 h all transformations were complete as determined by X-ray diffraction. The HA crystal dimensions decreased with increasing C03(2-) but the shape, as shown by X-ray linewidths, was relatively constant up to about 4% CO3(2-). At 15% CO3(2-) the crystals were more equiaxial and less needle-like in habit. The radial distribution function (RDF) of HA with 3.7% CO3(2-) is less well resolved than the RDF of HA with ambient CO3(2-) (1.1%). The peaks are less sharp and their amplitude falls more rapidly with increasing atomic separation than for low CO3(2-)-HA. These effects show that CO3(2-) decreases the regularity of the atomic arrangement when incorporated in HA. The rapid decrease, with increasing CO3(2-) content, of the IR splitting of the P-O bending mode of CO3(2-)-HA is attributed to reduced crystal size and possibly to a perturbation of the crystal field due to CO3(2-)-induced lattice distortion. Finally, for bone mineral, it is probable that the poor resolution of the X-ray and IR patterns is due, in large part, to small crystal size and internal disorder caused by CO3(2-).

Adsorption↗
PubMed1975

Atomic structure of intracellular amorphous calcium phosphate deposits.

The radial distribution function calculated from x-ray diffraction of mineralized cytoplasmic structures isolated from the hepatopancreas of the blue crab (Callinectes sapidus) is very similar to that previously found for synthetic amorphous calcium phosphate. Both types of mineral apparently have only short-range atomic order, represented as a neutral ion cluster of about 10 A in longest dimension, whose probable composition is expressed by the formula Ca9(PO4)6. The minor differences observed are attributed to the presence in the biological mineral of significant amounts of Mg-2+ and ATP. Synthetic amorphous calcium phosphate in contact with a solution containing an amount of ATP equivalent to that of the biological mineral failed to undergo conversion to the thermodynamically more stable hydroxyapatite. The amorphous calcium phosphate of the cytoplasmic mineral granules is similarly stable, and does not undergo conversion to hydroxyapatite, presumably owing to the presence of ATP and Mg-2+, known in inhibitors of the conversion process. The physiological implications of mineral deposits consisting of stabilized calcium phosphate ion clusters are discussed.

Animals↗