In a feasability study, a technique for constructing 3-dimensional sonographic images of the superficial digital flexor tendon (SDFT) was established in 6 clinically normal horses and applied to 7 horses with injured SDFT. Two-dimensional B-mode sonographic images were recorded on videotape as the sonographic transducer was manually moved along the palmar aspect of the metacarpal region. Selected videofields were digitized, and 3-dimensional images were constructed, using a computer work station and dedicated software program. The 3-dimensional images were of high quality and presented qualitative clinical information in unique fashion. Indication of the extent of SDFI injuries was excellent. Such 3-dimensional images would be especially useful in explaining to owners and trainers the importance of the injury to their horse and would have a role in monitoring tendon healing and in the assessment of various treatments.

Collagen type I was purified from equine skin and flexor tendon, and type II collagen was purified from equine articular cartilage. The proteoglycans in these tissues were extracted, using guanidine HCl; the collagens were solubilized, using pepsin digestion, then were selectively precipitated with Nacl. Gel electrophoresis indicated that the precipitates contained only type I or type II collagen. Amino acid analysis indicated that collagen constituted > 97% of the total protein in the precipitates. Hydroxylation of proline was 42.0 t 0.6% (mean SEM) in alpha 1(I) and alpha 2(I), and was 48.1 +/- 1.3% in alpha 1(II) chains. The hydroxylation of lysine was 23.2 +/- 0.7% in alpha 1(I) and 34.1 0.9% in alpha 2(I) chains from tendon, and 49.6 +/- 4.3% in alpha 1(II) chains from cartilage. The cyanogen bromide (CB)-peptide patterns of chromatographically purified equine alpha 2(I) and alpha 1(II) chains were similar to those published previously for rat, bovine, and human alpha 2 and alpha 1 chains. However, the CB-peptide pattern of the equine alpha 1(I) chain resembled the guinea pig alpha 1(I) chain, which has no methionine between CB7 and CB6. Purified equine alpha 1(I)CB7,6 contained no methionine, methionine sulfoxide, or homoserine lactone. Mass of 42.26 kd was determined by use of mass spectrometry, and N-terminal sequence analysis established that the first 12 amino acids of this CB7,6 were identical to the sequence of human alpha 1(I)CB7. Because of this species specific difference in structure of the alpha 1(I) chain, equine Cb-peptides should be used as standards in studies of variations in the proportions of type I and type II collagens in equine tissues expressing the phenotype of fibrous tissue and cartilage.