Studies on Transmissible Gastroenteritis of Swine: II. Selected Characteristics of a Cytopathogenic Virus Common to Five Isolates from Transmissible Gastroenteritis

Five cell culture isolates from transmissible gastroenteritis (TGE) of swine have been studied. There is a cytopathogenic virus common to all of these isolates. Some of the characteristics of this virus, such as its size, approximately 100 mµ, its relative sensitivity to ether, lability at pH 2, pH 3, and pH 10, and its heat lability suggest that it may be a member of the myxovirus class.Concurrent research in this laboratory indicates that this cytopathogenic virus is not the only virus involved in the etiology of TGE, but it appears to be associated with many of the outbreaks of TGE which have been studied by this laboratory.     

Comparison of Chondrogenic Potential in Equine Mesenchymal Stromal Cells Derived from Adipose Tissue and Bone Marrow

Objective— To compare the chondrogenic potential of adult equine mesenchymal stem cells derived from bone marrow (MSCs) or adipose tissue (ASCs). Study Design— In vitro experimental study. Animals— Adult Thoroughbred horses (n=11). Methods— BM (5 horses; mean [±SD] age, 4±1.4 years) or adipose tissue (6 horses; mean age, 3.5±1.1 years) samples were obtained. Cryopreserved MSCs and ASCs were used for pellet cultures in stromal medium (C) or induced into chondrogenesis±transforming growth factor‐3 (TGFβ₃) and bone morphogenic factor‐6 (BMP‐6). Pellets harvested after 3, 7, 14, and 21 days were examined for cross‐sectional size and tissue composition (hematoxylin and eosin), glycosaminoglycan (GAG) staining (Alcian blue), collagen type II immunohistochemistry, and by transmission electron microscopy. Pellet GAG and total DNA content were measured using dimethylmethylene blue and Hoechst DNA assays. Results— Collagen type II synthesis was predominantly observed in MSC pellets from Day 7 onward. Unlike ASC cultures, MSC pellets had hyaline‐like matrix by Day 14. GAG deposition occurred earlier in MSC cultures compared with ASC cultures and growth factors enhanced both MSC GAG concentrations (P<.0001) and MSC pellet size (P<.004) after 2 weeks in culture. Conclusion— Equine MSCs have superior chondrogenic potential compared with ASCs and the equine ASC growth factor response suggests possible differences compared with other species. Clinical Relevance— Elucidation of equine ASC and MSC receptor profiles will enhance the use of these cells in regenerative cartilage repair.     

Acceleration of Second and Fourth Metatarsal Fracture Healing with Recombinant Human Bone Morphogenetic Protein‐2/Calcium Phosphate Cement in Horses

Objective— To compare the efficacy of recombinant human bone morphogenetic protein‐2 (rhBMP‐2)/calcium phosphate (CP) to autogenous cancellous bone graft (CBG) and to no treatment on bone healing, in surgically induced osteotomies and ostectomies of the accessory metatarsal bones in an equine model. Study Design— Experimental. Animals— Adult horses (n=9). Methods— Segmental ostectomies of the second metatarsal bone (MT2) and osteotomies of the fourth metatarsal bone (MT4) were performed bilaterally in 9 horses. There were a total of 35 defects (1 MT4 was previously fractured) created and supplemented randomly either with no treatment (untreated control), rhBMP‐2/CP cement, or matrix (CPC or CPM), or CBG. Radiography was performed every 2 weeks until study endpoint at 12 weeks. After euthanasia, bone healing was evaluated using radiography, mechanical testing, and histology. Data were analyzed with ANOVA followed by the Duncan's Multiple Range Test or nonparametric analyses. Results— At 12 weeks, radiographic scores for union were significantly greater for the rhBMP‐2 (P<.0001) and CBG (P=.004) groups compared with the untreated control group, for both MT2 ostectomies and MT4 osteotomies. The rhBMP‐2 treated MT2 had greater maximum torque to failure in torsion than CBG and control limbs at 12 weeks (P=.011). Histologic analysis demonstrated increased bone formation and more mature bone at the ostectomy site for MT2 in the rhBMP‐2 and CBG groups compared with the untreated control group. Conclusion— Injection of rhBMP‐2/CP into surgically induced ostectomies and osteotomies of the accessory metatarsal bones might accelerate early bone healing in the horse. Clinical Relevance— RhBMP‐2/CP may be as effective if not superior to CBG as an adjuvant treatment to accelerate healing of bone defects.     

Topical Dexamethasone and Dimethyl Sulfoxide Solutions Do Not Result in Detectable Blood Levels of Dexamethasone

Dexamethasone is a potent corticosteroid anti-inflammatory agent, and in most jurisdictions it is not legal to administer to any horse on the day of a race. This study was conducted to determine whether topical combination of dexamethasone and dimethyl sulfoxide (DMSO) solutions would result in detectable dexamethasone in the blood or urine in horses. Five different concentrations of dexamethasone/DMSO were used to replicate the combinations used on race horses. Serum cortisol concentrations were determined to detect an alteration in the hypothalamus-pituitary-adrenal axis. Dexamethasone/DMSO mixtures were applied topically to the distal limbs in five Standardbred mares. Blood and urine samples were collected at 0, 8, 24, and 32 hours. Samples were originally screened by a commercially available enzyme-linked immunosorbent assay (ELISA) test for dexamethasone. Any samples that were deemed suspect were then analyzed by liquid chromatography/mass spectrometry (LC/MS). Blood cortisol was assayed using a solid-phase chemiluminescence enzyme immunoassay. There was no detectable dexamethasone in either the urine or serum of any horse at any time point. The serum cortisol concentrations were within our laboratory's normal range at all time points. It appears doubtful that detectable blood and urine concentrations of dexamethasone are attributable to absorption from a topical application through intact skin.