The precipitation of collagen fibrils from solutions at 37°C and approximately physiological pH and ionic strength is retarded markedly in the presence of small amounts of proteoglycan monomer (PGS), proteoglycan aggregate (PGC), reduced and alkylated PGS, or cyanogen bromide-cleavage products of PGS. The polysaccharide-peptide fragments produced from PGS with papain, trypsin, cathepsin D, or the protein core obtained by the digestion of PGS with chondroitinase ABC are ineffective in this regard.

Proteoglycans from bovine nasal septa and from the Swarm rat chondrosarcoma were isolated as aggregates (PGC) and as monomers (PGS). Portions of the PGC preparations were degraded with cathepsin D or chondroitinase AC. Chondroitin sulfates were isolated by differential precipitation from alkaline digests of the PGS from bovine nasal septa. The effects of these preparations at concentrations up to 2 mg/ml on the precipitation of tricalcium phosphate in vitro at pH 7.8 in 16 hours at 25 degrees C were ascertained. To this end, the amounts of calcium and phosphate in the precipitates and in the supernates were determined. The PGC preparations were found to be very effective inhibitors; in the presence of 2 mg/ml, precipitate did not form. The PGS preparations were less effective than the PGC preparations; in the presence of 2 mg/ml, about 20% as much calcium phosphate precipitated as in their absence. The chondroitinase AC-degraded preparations at concentrations equivalent to 2 mg/ml of the PGC preparations were approximately as effective as the PGS preparations. On the other hand, the cathepsin D-degraded PGC preparations and the chondroitin sulfate chains were relatively poor inhibitors. Although the viscosity of the solutions may have influenced the rate at which the precipitates settled to the bottom of the tubes, the amounts of the tricalcium phosphate formed were related to the composition and concentration of the proteoglycan preparations.

Fluorescein labeled antibodies to protein- polysaccharides from rat and calf cartilage were used for the histochemical localization of protein- poly saccharide in epiphyseal cartilage. There was less protein- polysaccharide in the zone of provisional calcification than in the proliferating and maturing zones, and none was demonstrable in the metaphysis. During or just preceding cal cification, protein- polysaccharide or its protein component is lost or drastically altered.

No abstract

In a previous paper (1) it was reported that after intmperitoneal administration of sulfur-35 in the form of sodium sulfate to suckling rats, 7 days of age, the isotol~e was demonstrable in the knee joint cartilage during the following 164 hours. Up to the 24th hour the concentration of sulfur-35 was on the increase and thereafter up to the 164th hour its concentration decreased, but slowly. It was suggested in the same paper that most, if not all, of the sulfur-35 retained after 24 to 48 hours in the knee joint cartilage may have been retained therein as chondroitin sulfate. This suggestion was based on observations that the sulfur-35 concentration was not appreciably decreased in an aqueous solution of cartilage, which had been removed from suckling rats injected with labeled sodium sulfate by the addition to the solution of solid barium carbonate to saturation followed by heating for 6 hours on a steam-bath. Had the sulfur-35 been present as inorganic sulfate or in any form which was insoluble as the barium salt it is highly probable that it would have been removed from the solution by the centrifugation and filtration which followed the heating period with barium carbonate, whereas the barium salt of chondroitin sulfate would have remained in solution. This suggestion has been substantiated by work reported in a more recent paper (2) on the isolation of chondroitin sulfate with sulfur-35 incorporated therein after administration of this isotope as sodium sulfate.Our curiosity was aroused as to how the isotope, sulfur-35, when given as sodium sulfate was taken up and distributed in the epiphyseal cartilage of suckling rats. An attempt to answer this question by the radioautographic technique has been made. The results are here reported. MethodSuckling rats of the Whelan strain were used. In one series of experiments 2 mg. of S atagged sodium sulfate I-(8.24 X 10 s C.P.M.) in 0.I ml. distilled water was injected intraperi-I The snifur-35 used in this investigation was supplied by the Oak Ridge National Laboratory, on allocation from the United States Atomic Energy Commission.The activity was determined on the BaSO4 precipitated from an aliquot of the solution