Michael Roma

Biochemical studies of articular cartilage. I. Normal values.

The histochemical characterization of articular cartilage from front and hind limbs of puppies up to twenty-five weeks of age has been presented. The average mass patterns for one kilogram of fresh cartilage were as follows : Through sixteen weeks of age, the extracellular compartment consisted of 522 grams of extracellular water (H2O)E and 161 grams of extracellular solids (E)S or a total of 683 grams, leaving 317 grams for the weight of the chondrocytes (C), of which 263 grams are the chondrocyte water (H2O)C and 54 grams, the chondrocyte solids (C)s. For the older puppies, seventeen to twenty-five weeks of age, the extracellular-compartment mass was 720 grams of which 548 grams were (H2O)E and 172 grams, (E)S. The intracellular compartment or the weight of (C) was 280 grams of which 209 grams were (H2O)C and 71 grams, (C)S. Using these patterns for articular cartilage, the distribution and concentration of constituents in these tissues have been presented and discussed. Briefly, some of the most consequential points deduced from our data on fresh articular cartilage were: 1. The total water content of the tissue decreased in amount from 80 per cent to 75 per cent as the puppies aged. 2. The connective tissue increased in amount from a value of 104 grams per kilogram to 159 grams per kilogram as the puppies aged while the chondroitin sulfate mass decreased from thirty-eight grams per kilogram to twenty-three grams per kilogram. Even though the chondroitin sulphate decreased, the connective tissue increased enough to bring up the mass of the total extracellular solids from a value of 146 grams per kilogram to 181 grams per kilogram. 3. The percentage of water in the chondrocytes was an average of 83 per cent through the sixteen-week-old group; thereafter it was an average of 75 per cent in the older groups. 4. The average concentration of potassium in the chondrocytes was fifty-three milliequivalents per kilogram of chondrocytes or sixty-six milliequivalents per kilogram of chondrocyte water. The average concentration of magnesium was thirty-five milliequivalents per kilogram of chondrocytes and forty-three milliequivalents per kilogram of chondrocyte water.

Biochemical studies of articular cartilage. III. Values following the immobilization of an extremity.

By means of histochemical procedures the characterization of the compartments of articular cartilage, the distribution of water, electrolytes, connective tissue, and chondroitin sulphage in these compartments during immobilization atrophy have been described. The results obtained support the following conclusions concerning the cartilage during immobilization of an extremity: 1. The total water content increased as the result of an increase in the ultrafiltrate volume in the extracellular compartment. 2. The amounts of both the connective tissue and the chondroitin sulphate in fresh cartilage decreased but these percentage decreases were not so large as when 100 grams of cartilage solids were considered, suggesting that the low values of these two constituents were the result of dilution of the extracellular compartment with the increased ultrafiltrate volume. 3. The ΔNa values (total determined sodium minus the sodium in the extracellular phase) were low paralleling the low chondroitin sulphate values and thus giving further support to the conclusion that the low chondroitin sulphate values were the result of dilution. 4. In the intracellular compartment of the chondrocytes, the percentage of intracellular water did not change; nor was there any change in the concentration of potassium which is the cation present in the chondrocyte indicating that the functioning cytoplasm of the chondrocytes had not altered during immobilization atrophy. 5. Considering the two types of experimental atrophy in cartilage from denervation reported previously and disuse reported here, our chemical data and their interpretations have afforded a basis for some deductions on when atrophy is reversible, as in disuse, and when it is not reversible, as in atrophy following denervation.

Tissue studies during recovery from immobilization atrophy

Immobilization of one hind leg of puppies was produced at 12 weeks of age. After 6 weeks of immobilization, the immobilized muscles were restored to weight bearing. The opposite leg was the control leg. To study recovery from atrophy in these muscles, biochemical analyses and histochemical patterns of the muscles were used. Recovery periods varied from 55 to 300 days. In the 91-day remobilization group there were increased values in the interfiber constituents as well as decreases in the intrafiber constituents, but values were not as large as in immobilization only. After 300 days of remobilization the formerly atrophic muscles had regained the same concentration as in the control muscles, indicating recovery. The histochemical patterns of 1 kg of control muscle and remobilized muscle were traced. The ultrafiltrate volume in the groups up to 91 days of remobilization was increased in amounts over the control volumes, but the increases were not as large as in immobilization only. In 300-day group all volumes were the same as in the control, indicating recovery from atrophy, according to these criteria.