Search Results

Abstract

Objective—To determine significant molecular and cellular factors responsible for differences in secondintention healing in thoracic and metacarpal wounds of horses.

Animals—6 adult mixed-breed horses.

Procedure—A full-thickness skin wound on the metacarpus and another such wound on the pectoral region were created, photographed, and measured, and tissue was harvested from these sites weekly for 4 weeks. Gene expression of type-I collagen, transforming growth factor (TGF)-β1, matrix metalloproteinase (MMP)-1, and tissue inhibitor of metalloproteinase (TIMP)-1 were determined by quantitative in situ hybridization. Myofibroblasts were detected by immunohistochemical labeling with α-smooth muscle actin (α-SMA). Collagen accumulation was detected by use of picrosirius red staining. Tissue morphology was examined by use of H&E staining.

Results—Unlike thoracic wounds, forelimb wounds enlarged during the first 2 weeks. Myofibroblasts, detected by week 1, remained abundant with superior organization in thoracic wounds. Type-I collagen mRNA accumulated progressively in both wounds. More type-I collagen and TGF-β1 mRNA were seen in forelimb wounds. Volume of MMP-1 mRNA decreased from day 0 in both wounds. By week 3, TIMP-1 mRNA concentration was greater in thoracic wounds.

Conclusions and Clinical Relevance—Greater collagen synthesis in metacarpal than thoracic wounds was documented by increased concentrations of myofibroblasts, type-I collagen mRNA, TGF-β1 mRNA, and decreased collagen degradation (ie, MMP-1). Imbalanced collagen synthesis and degradation likely correlate with development of exuberant granulation tissue, delaying healing in wounds of the distal portions of the limbs. Factors that inhibit collagen synthesis or stimulate collagenase may provide treatment options for horses with exuberant granulation tissue. (Am J Vet Res 2002;63:1564–1570)

Summary

Newborn pups from 4 large litters were allotted to 6 groups to determine effect of time and route of administration on absorption of an alternate source of immunoglobulin. Selective absorption of specific classes of immunoglobulins was also investigated. The alternate source of immunoglobulin consisted of pooled serum that was administered either po or sc. Control groups were either left with the dam (group C1) or fed milk replacer (group C2). Blood samples were collected from pups at birth and 24 hours. Immunoglobulin (IgA, IgG, IgM) concentrations were determined by use of radial immunodiffusion on samples of pooled serum, colostrum, and pups’ serum (birth and 24 hours).

Serum IgA concentration was less than the sensitivity of the procedure and was not included in the statistical analysis. Pups fed 8 ml of pooled serum at birth and 12 hours later (group T1) absorbed more (P< 0.05) IgG and IgM than did group-C2 pups, but less (P < 0.05) than did group-C1 pups. Pups fed 8 ml of pooled serum at 12 hours only had significant (P < 0.05) increase of IgG concentration, but no absorption of IgM (P > 0.05) at 24 hours, compared with control pups (group C2). Pups administered 8 ml of pooled serum SC at birth (group SC1) had similar (P > 0.05) absorption of IgG and higher (P < 0.05) absorption of IgM than did pups of group T1. Pups administered 16 ml of pooled serum sc at birth had the highest increase of IgG and IgM concentrations of all treatment groups, but immunoglobulin concentrations were lower (P < 0.05) than those for group-C1 pups. Absorption of IgG was favored, compared with IgM, when pooled serum was fed.

Results indicate clearly that intestinal absorption of immunoglobulins is minimal after 12 hours and thus, another route of administration should be used. Pups in groups SC1 and T1 had similar absorption of IgG, despite lower IgM absorption in pups of group T1. This lower IgM concentration in group-T1 pups may have been the result of selective intestinal absorption or the consequence of low number of pups per group. Subcutaneous administration of 16 ml of pooled serum was the most successful alternative to colostrum, with minimal pain to pups if serum was administered slowly. Serum IgG concentration in Cl pups was higher than expected and probably was attributable to the amount of colostrum available to the pups.

Abstract

Objective—To quantify changes in endothelium-derived factors and relate those changes to various aspects of digital hemodynamics during the prodromal stages of carbohydrate overload (CHO)-induced laminitis in horses.

Animals—20 adult horses without abnormalities of the digit.

Procedures—Digital and jugular venous blood samples were collected at 1-hour intervals (for assessment of endothelin-1 [ET-1] immunoreactivity and measurement of glucose, insulin, and nitric oxide [NO] concentrations) or 4-hour intervals (CBC and platelet-neutrophil aggregate assessment) for 8 hours or 16 hours after induction of CHO-associated laminitis in horses treated with an ET-1 antagonist. Effects of treatment, collection site, and time and the random effects of horse on each variable were analyzed by use of a repeated-measures model. Where treatment and collection site had no significant effect, data were combined.

Results—Compared with baseline values, CHO resulted in changes in several variables, including a significant increase from baseline in digital blood ET-like immunoreactivity at 11 hours; digital blood ET-like immunoreactivity was significantly greater than that in jugular venous blood at 8, 9, 11, and 12 hours. Digital and jugular venous blood concentrations of glucose increased from baseline significantly at 3, 4, and 5 hours; insulin concentration increased significantly at 5 hours; and the number of platelet-neutrophil aggregates increased significantly at 12 hours.

Conclusions and Clinical Relevance—In horses, concurrent increases in venous blood ET-1 immunoreactivity, insulin and glucose concentrations, and platelet-neutrophil aggregates support a role of endothelial dysfunction in the pathogenesis of CHO-induced laminitis.