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DE COCK ET AL. TABLE 1.
DESMOSINE CONCENTRATION IN THE NECK AND DISTAL LIMBS AFFECTED AND NOT AFFECTED DRAFT HORSE BREEDS
FROM
Groupยง 1 2 3 4 5
Number of horses
Neck region desmosine
7 38 30 15 20
191 286 266 319 281
( ( ( ( (
Forelimb desmosine
94) 106) 80) 151) 99)
269 406 323 291 305
( ( ( ( (
51) 167) 125) 167) 81)
Desmosine
concentration in pmol/mg protein ( SD). 1 normal animals; group 2 mild lesions; group 3 moderate lesions; group 4 severe lesions in affected breeds; group 5 normal control nonaffected breed. ยงGroup
with moderate lesions (p 0.021). The differences observed for the group with severe lesions and the control group of a nonaffected breed were not statistically significant (p 0.35). When these clinical group-specific location effects were adjusted for age and gender, the results noted above remained the same with the single exception that the difference observed for the group with moderate lesions was no longer statistically significant (p 0.27). The interaction between location (neck vs. left forelimb) effects and clinical group effects also indicates that the difference in mean desmosine among the clinical groups is not the same for the forelimb and neck regions. Subsequent statistical analysis indicated there to be no statistically significant difference (p 0.15) among the five groups in mean desmosine concentration of the neck region both before and after adjusting for the effects of age and gender. In contrast, a highly significant difference (p 0.004) was observed among the five groups in mean desmosine concentration of the forelimb. Multiple pairwise comparisons of the means indicated that the mean desmosine concentration of group with mild lesions was significantly higher than the mean desmosine concentrations of group with severe lesions and the control group of a nonaffected breed; no other comparisons were statistically significant with a level of significance of 5% over all comparisons. The clinical group effect in the forelimb was no longer statistically significant (p 0.23) when adjusted for age and gender. When the desmosine concentration of the neck and limb was statistically compared for
the control group of a nonaffected breed (group 5) and the normal animals of affected breeds (group 1), a borderline nonsignificantly lower desmosine concentration was found in the skin from the normal affected breed (p 0.053). This difference became significant (p 0.045) when adjusted for age and gender.
CONCLUSIONS Lymph capillaries differ from blood capillaries in certain structural features. One of them is the presence of a small network of elastic fibers surrounding lymphatics.12 This network is believed to constitute an elastic device aiding propulsion of the lymph. Defective function or destruction of the elastic fibers prevents the transmission of tissue traction to the lymph capillary wall, reducing the reabsorption and propulsion of lymph and cells along the lymphatic. A consequence of this is edema and impaired immune response.7 In this study, differences in dermal elastin were noticed in the skin of draft horses affected with the condition known as chronic progressive lymphedema when compared to a nonaffected draft horse breed. Normal animals of the affected draft horse breeds had lower elastin concentrations in their skin when compared to a nonaffected draft horse breed. Interestingly, these changes were similar in the skin of the pastern and neck region, previously considered as clinically normal skin. This might suggest that the condition is a generalized skin disease rather than a dis-