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1. Subcellular fractions of freshly isolated matrix-free embryonic chick tendon and sternal cartilage cells have been characterized by chemical analysis, electron microscopy and the location of specific marker enzymes. These data indicate the fractions to be of a high degree of purity comparable with those obtained from other tissues, e.g. liver and kidney. 2. When homogenates were assayed for protocollagen prolyl hydroxylase and protocollagen lysyl hydroxylase activities, addition of Triton X-100 (0.1%, w/v) was found to stimulate enzyme activities by up to 60% suggesting that the enzymes were probably membrane-bound. 3. Assay of subcellular fractions obtained by differential centrifugation for protocollagen prolyl hydroxylase activity indicated the specific activity to be highest in the microsomal fraction. Similar results were obtained for protocollagen lysyl hydroxylase activity. 4. Submicrosomal fractions obtained by discontinuous sucrose-gradient centrifugation were assayed for the two enzymes and protocollagen prolyl hydroxylase and protocollagen lysyl hydroxylase were found to be associated almost exclusively with the rough endoplasmic reticulum fraction in both tendon and cartilage cells.

Scorbutic guinea pigs were wounded and the influence of administering ascorbic acid 6 days later was studied with respect to cellular morphology, ribosomal distribution and protein synthesis. Electron-microscopic studies revealed that the dilated endoplasmic reticulum observed in the fibroblasts of scorbutic wound tissue had reverted to a normal configuration 24h after intraperitoneal injection of 100mg of ascorbate. Quantitative determination of the distribution of free and membrane-bound ribosomes indicated a significant increase in membrane-bound ribosomes in wound tissue from ascorbate-supplemented (recovery) animals. Sucrose-density-gradient centrifugation indicated a significant increase in the proportion of large membrane-bound polyribosomes in the range 300–350S and a concomitant decrease in 80S monoribosomes in the ribosome sedimentation profile of recovery tissue. Determination of the synthesis of non-diffusible [3H]hydroxyproline in scorbutic and recovery wounds showed a 3–4-fold stimulation in peptidyl-proline hydroxylation in recovery tissues. Studies carried out in which scorbutic and recovery tissues were incubated with [14C]leucine indicated that general protein synthesis, as measured by14C incorporated into non-diffusible material/μg of DNA, was unaltered by ascorbate supplementation. Similar studies of [3H]proline incorporation suggested that in recovery tissues there was a small but significant increase in [3H]proline incorporated/μg of DNA, which probably represents an increase in protocollagen synthesis. This observation correlates well with the increase seen in recovery tissues of large polyribosomes on which collagen precursor polypeptides are known to be synthesized. Preliminary characterization of the repair collagen synthesized by recovery animals showed it to be a typical Type I collagen having the chain composition (α1)2α2. The extent of glycosylation of the hydroxylysine of the newly synthesized collagen was greater than that reported for either normal guinea-pig dermal collagen or dermal scar collagen.