Rabbit Cortical Bone Research Articles

A soluble bone morphogenetic protein extracted from bone matrix with a mixed aqueous and nonaqueous solvent.

SummaryA soluble bone morphogenetic protein (BMP) along with other noncollage-nous proteins including only a relatively insignificant quantity of hydroxyproline-con-taining peptides were extracted from rabbit cortical bone by the action of an aqueous-nonaqueous solvent mixture. As it is bound by carbohydrate recognition and hydropho-bic interaction with Con A, BMP has an essential characteristic of a glycoprotein. When α-methyl mannoside and ethylene gly-col elutes of proteins bound to a Con-A column are implanted inside of double-walled diffusion chambers, deposits of cartilage and bone develop on the outside. While estimates of the quantity of BMP are less than 0.01% of the dry weight of bone matrix, it is possible to concentrate and purify a biologically active BMP by application of the principles of hy-drophobic protein chemistry.

Solubilized and insolubilized bone morphogenetic protein.

A bone morphogenetic protein (BMP) obtained in solution by digestion of demineralized rabbit cortical bone matrix with bacterial collagenase retains its biologically active conformation in a neutral salt/ethylene glycol mixture. BMP may be insolubilized by coprecipitation with calcium phosphate and resolubilized by chemical extraction with a neutral salt in the same solvent mixture. Upon concanavalin A-Sepharose chromatography, BMP is bound by hydrophobic interaction and carbohydrate recognition and is recovered by elution with either alpha-methyl mannoside or ethylene glycol solvent mixture. Implants of both eluates and the extracts of the coprecipitate in double-walled diffusion chambers induce transmembrane bone morphogenesis. BMP is not species specific; rabbit BMP induces new bone formation in the rat. The present observations indicate that BMP is a glycoprotein.

Studies on bone matrix glycoproteins. Incorporation of (1-14C)glucosamine and plasma (14C)glycoprotein into rabbit cortical bone.

The radioactively labelled constituents present in bone matrix were compared 12 days after injection of either [(14)C]glucosamine or plasma [(14)C]glycoprotein. Both precursors are utilized in the synthesis of organic matrix by bone tissue. Cortical bone from animals injected with [(14)C]glucosamine contains radioactivity derived from glucosamine and plasma glycoproteins and all glycoprotein fractions are labelled. Plasma [(14)C]glycoprotein labels the less acidic glycoproteins to a greater extent than the more acidic components. An antibody has been raised against the less-acidic-glycoprotein fraction of bone. The latter contains a glycoprotein of alpha-mobility that appears to be concentrated specifically in bone tissue and which is present also in plasma. This alpha-glycoprotein accounts for a large proportion of the components labelled and retained in bone matrix after [(14)C]glucosamine injection.

Some current concepts of bone physiology.

Citric Acid and Bone MetabolismAlthough the skeleton contains a high concentration of citrate (about 1 per cent in rabbit cortical bone) the origin of this citrate has been disputed. Armstrong and Singer66 support the idea that the major part of the skeletal mineral citrate occurs adventitiously owing to the constant presence in body fluids of citrate originating from nonskeletal tissues. On the other hand, since Dixon and Perkins67 described what appeared to be an enzyme mechanism for accumulating a high, local concentration of citric acid, it was suggested that the bone mineral citrate is derived from bone cells and . . .