Introduction and Hypothesis: Local intramuscular injections of botulinum toxin in humans and several animal species inhibit the release of acetylcholine in pre-synaptic motor end-plates resulting in prolonged reversible muscle relaxation. The hypothesis of this study was that intramuscular injections of Myoblock® (botulinum toxin type-B) in the external anal sphincter of horses would cause reduction of anal sphincter tone without causing systemic side effects.Materials and Methods: Peak and resting anal sphincter pressures were measured with a custom made rectal probe connected to a pressure transducer. Pressures were measured before treatment and after injections with Myoblock® or saline and until any changes in sphincter pressure returned to normal. The horses' physical changes, behavior, and anal pressure were recorded.Results: Injections of botulinum toxin type-B produced a reduction in anal sphincter tone and peak anal sphincter pressure a few days after injections. Return to baseline peak anal pressure was observed within 168 days. When compared to controls, there was a significant decrease in peak anal pressure after botulinum toxin injection. Injection in the anal sphincter with 2500 units of type-B toxin in one horse produced transient signs of depression, generalized weakness, and dysphagia. Clinical side effects were not observed in horses after injections with 500, 1000, or 1500 units of toxin.Discussion: The effect of intramuscular injection of botulinum toxin type-B in horses is similar to other species. However, horses, compared to other species, are very sensitive to the toxin and clinical signs of botulism may develop with doses that don't cause a systemic effect in other species. The results of this study suggest that a single treatment with botulinum toxin type-B in the external anal sphincter of mares has the potential to reduce incisional dehiscence after repair of perineal lacerations.
CHONDROGENIC POTENTIAL OF DIRECT PLASMID GENE DELIV-ERY IN THREE DIMENSIONAL CULTURE.Several morphogens have the ability to enhance cellular proliferation (ie, FGF-2) and expression of proteoglycan [PG] and type-2 collagen (ie, IGF-1 and BMP-2) in chondrocytes. Delivery of these genes can be therapeutic. Nonviral (vs viral) gene delivery offers advantages, but suffers from lower transfection. Our study (1) optimized direct DNA transfer in a 3-D cell system that can be implanted in vivo using plasmid DNA and (2) evaluated hFGF, hIGF1 and hBMP2 to promote chondrocyte proliferation and expression of matrix using a 3-D collagen suspension. Chondrocytes from the knee joint of calves were suspended in constructs of known cell density with the desired DNA and lipid [Lipofectamine2000] concentration in type-1 collagen gel and cultured for 14 days. Optimal cell density [0.5, 1, and 2 x 106 cells/well], pDNA/well [0, 0.9, 1.86, 4.65, 9.3, 18.6, 37.2, and 74.4 ug DNA], and lipid reagent [2:1, 3:1 and 6:1 DNA/Lipid ratio] for transfection were quantified with plucerifase [pg/ml] and %GFPϩ cells. Based on the results of t...
