Muscular dystrophy in dogs: does the crossing of breeds influence disease phenotype?

Golden Retriever (GR) muscular dystrophy is an inherited degenerative muscle disease that provides an excellent model for Duchenne muscular dystrophy in humans. This study defined the histopathologic lesions, including the distribution of type I and II muscle fibers (FTI and FTII), in 12 dystrophic and 3 nondystrophic dogs between 7 and 15 months of age. The authors were interested in studying the influence on disease phenotype from crossing the base GR breed with Yellow Labrador Retrievers. The dystrophic dogs were divided according to breed: GRs and Golden Labrador Retrievers (GLRs). On hematoxylin and eosin staining, histopathologic lesions were more severe in GRs than GLRs. Six of eight GR muscles (75%) had a severe lesion grade (grade 3). In contrast, seven GLR muscles (87.5%) had mild lesions (grade 2), and only one had severe lesions (grade 3). Changes in fiber-type distribution were more pronounced in GRs versus GLRs. FTI:FTII ratio inversion was observed in three dystrophic GRs but only one GLR. The mean diameter of FTI and FTII was smaller in GRs and GLRs than in nondystrophic dogs (P < .01). The FTI of five GR muscles (62.5%) were larger than those of GLRs, whereas only one GLR muscle was larger (P < .05). The differential was less pronounced for FTII, with four GR muscles being larger and three GLR being larger. Observations indicate that crossing the base GR breed with Labrador Retrievers lessened the severity of the GR muscular dystrophy phenotype.

Effects of glycosaminoglycan polysulphate on the organisation of collagen fibres in experimentally induced tendonitis in horses.

An inflammatory process was induced by intratendinous injection of bacterial collagenase into the superficial digital flexor tendon (SDFT) of the left thoracic limb of 10 horses. One week later, the tendons in five of the horses (group 1) were treated with glycosaminoglycan polysulphate (GAGPS), and the tendons of the other five (group 2) were treated with saline solution. The horses were euthanased 150 days after the collagenase injections, and samples of the SDFTs were frozen at -14 degrees C, sectioned at 5 to 7 mum longitudinally and transversely, and stained by the picrosirius red method. Morphometric analysis was used to quantify the organised and disorganised bundles of collagen in the samples from groups 1 and 2. Significantly more organised bundles of collagen were observed in the tendons treated with GAGPS.