Albert Hirschman

Composition of the mineral deposited during in vitro calcification in relation to the fluid phase

Abstract Despite the fact that in vitro calcification of rachitic epiphyseal cartilage has been extensively employed in studies of the mechanism of calcification, the chemical composition of the solid deposited was not hitherto investigated. The present investigation is a study of the mineral deposited during in vitro calcification of the matrix of hypertrophic rachitic epiphyseal cartilage from calcifying solutions of different compositions. The solids deposited and the solutions used were analysed for calcium, phosphate, and carbonate by methods described herein. The CO3:PO4 and Ca:PO4 ratios of the solid were linearly related to those of the fluid within the range of solution compositions used. The increase in the Ca:PO4 ratio of the solids as the Ca:PO4 and CO3:PO4 ratios of the solution were raised was due to increased deposition of CaCO3. Although the compositions of the solid varied, the residual Ca:PO4 ratio was 1.33 in all cases. The Ca:PO4 ratio of 1.33 corresponds to that of octocalcium phosphate or may represent a defect apatite. The low Ca:PO4 ratios found in in vitro calcification resembles the compositions usually found in young bone, and may represent the composition of newly deposited bone mineral in vivo.

Soluble Sulfatase in Growing Bone of Rats

Soluble sulfatase has been found in epiphyseal, articular, and rib cartilages and in metaphysis and bone marrow of the rat. The greatest activity in young rats is in the metaphysis. Young rats had higher levels of activity in epiphyseal and articular cartilage and in the metaphysis than did the older rats.

The Effect of Proteolytic Enzymes and Hyaluronidase in Vitro on the Calcification Mechanism of Epiphyseal Cartilage

Summary Incubation of slices of rachitic epiphyseal cartilage of rats in trypsin, chymotrypsin, pronase, and hyaluronidase resulted in a loss of calcifiability, as determined by subsequent incubation in calcifying solutions. It is concluded that breakdown of glycosaminoglycan-protein, per se, in cartilage is not a sufficient condition to make the tissue calcifiable.

Effects of irradiation in vitro on calcifying mechanism of epiphyseal cartilage.

Summary 1. X-irradiation of rachitic epiphyseal cartilage with 250,000 R resulted in small decrease in calcifiability, loss of β-metachromatic granules from some cells of the proliferative zone, and a slight general decrease in staining of the hypertrophic zone. X-irradiation with 500,000 R resulted in marked decrease in calcifiability, loss of most of the β-metachromatic granules from some cells of the proliferative zone, and loss of β-metachromatic granules from some cells of the hypertrophic zone. X-irradiation with 1,000,000 R resulted in almost complete loss of both calcifiability and stainability with toluidine blue. 2. Toluidine blue staining of fresh sections of epiphyseal cartilage was employed for demonstration of metachromatic substances. 3. Once the process of calcification had been initiated, the inactivating effect of irradiation on calcifiability was considerably reduced. 4. A change in mucopolysaccharide resulting in increase of free electronegative groups is a factor associated with calcifiability of epiphyseal cartilage.