OBJECTIVE:To determine effects of sodium hyaluronate (HA) on corticosteroid-induced cartilage matrix catabolism in equine articular cartilage explants.SAMPLE POPULATION:30 articular cartilage explants from fetlock joints of 5 adult horses without joint disease.PROCEDURE:Articular cartilage explants were treated with control medium or medium containing methylprednisolone acetate (MPA; 0.05, 0.5, or 5.0 mg/mL), HA (0.1, 1.0, or 1.5 mg/mL), or both. Proteoglycan (PG) synthesis was measured by incorporation of sulfur 35-labeled sodium sulphate into PGs, and PG degradation was measured by release of radiolabeled PGs into the medium. Total glycosaminoglycan (GAG) content in media and explants and total explant DNA were determined.RESULTS:Methylprednisolone acetate caused a decrease in PG synthesis, whereas HA had no effect. Only the combination of MPA at a concentration of 0.05 mg/mL and HA at a concentration of 1.0 mg/mL increased PG synthesis, compared with control explants. Methylprednisolone acetate increased degradation of newly synthesized PGs into the medium, compared with control explants, and HA alone had no effect. Hyaluronate had no effect on MPA-induced PG degradation and release into media. Neither MPA alone nor HA alone had an effect on total cartilage GAG content. Methylprednisolone acetate caused an increase in release of GAG into the medium at 48 and 72 hours after treatment. In combination, HA had no protective effect on MPA-induced GAG release into the medium. Total cartilage DNA content was not affected by treatments.CONCLUSIONS AND CLINICAL RELEVANCE:Our results indicate that HA addition has little effect on corticosteroid-induced cartilage matrix PG catabolism in articular cartilage explants.

OBJECTIVETo evaluate the effect of an osteoconductive resorbable calcium phosphate cement (CPC) on the holding power of bone screws in canine pelvises and to compare the effect with that for polymethylmethacrylate (PMMA).SAMPLE POPULATION35 pelvises obtained from canine cadavers.PROCEDUREEach pelvis was sectioned longitudinally. Within each pair of hemipelvises, one 4.0-mm cancellous screw was placed in the sacroiliac (SI) region and another in the iliac body. Similar regions on the contralateral-matched hemipelvis were assigned 1 of 3 augmentation techniques (CPC-augmented 4.0-mm cancellous screws, PMMA-augmented 4.0-mm cancellous screws, and CPC-augmented 3.5-mm cortical screws). Pullout force was compared between matched screws and between treatment groups prior to examination of cross sections for evaluation of cement filling and noncortical bone-to-cortical bone ratio.RESULTSCPC and PMMA augmentation significantly increased pullout force of 4.0-mm screws inserted in the SI region by 19.5% and 33.2%, respectively, and CPC augmentation significantly increased pullout force of 4.0-mm cancellous screws inserted in the iliac body by 21.2%. There was no difference in the mean percentage augmentation between treatment groups at either location. Cement filling was superior in noncortical bone, compared with filling for cortical bone. Noncortical bone-to-cortical bone ratio was significantly greater in the sacrum (6.1:1) than the ilium (1.3:1).CONCLUSIONS AND CLINICAL RELEVANCECPC and PMMA improve the ex vivo holding strength of 4.0-mm cancellous screws in the SI and iliac body regions and SI region, respectively. Cement augmentation may be more effective in areas with greater noncortical bone-to-cortical bone ratios.

OBJECTIVE:To study the effects of phenylbutazone, indomethacin, prostaglandin E2 (PGE2), glutamine, and butyrate on restitution of oxidant-injured right dorsal colon of horses in vitro.SAMPLE POPULATION:Right dorsal colon from 9 adult horses euthanatized for reasons other than gastrointestinal tract disease.PROCEDURES:Mucosal segments from the right dorsal colon were injured via exposure to HOCl and incubated in Ussing chambers in solutions containing phenylbutazone, indomethacin, indomethacin and PGE2, glutamine, and butyrate. Transepithelial resistance and mucosal permeability to mannitol were measured, and all mucosal segments were examined histologically.RESULTS:The HOCl-injured mucosa had lower resistance and higher permeability to mannitol, compared with control tissue. Histologic changes were also evident. Resistance of HOCl-injured mucosa recovered partially during the incubation period, and glutamine improved recovery. Phenylbutazone and indomethacin increased resistance, but these increases were not significant. Butyrate and PGE2 had no effects, compared with nontreated HOCl-injured tissues. Mucosal permeability to mannitol was lower in glutamine-treated tissue, compared with nontreated tissue. Histologic changes reflected the resistance and permeability changes.CONCLUSIONS AND CLINICAL RELEVANCE:According to our findings, phenylbutazone and indomethacin do not seem to interfere with restitution of oxidant-injured mucosa of equine colon in vitro, and glutamine could facilitate mucosal restitution.

OBJECTIVES:To evaluate the in vitro protective effects of acetylcysteine and response of resident mucosal eosinophils in oxidant-induced injury to tissues of right dorsal colon of horses.ANIMALS:9 adult horses.PROCEDURE:Gastrointestinal mucosa was damaged in vitro with 3 mM hypochlorous acid (HOCl), with and without prior exposure to 6mM acetylcysteine. Control tissues were not exposed to HOCl or acetylcysteine. Control and damaged tissues were incubated in Krebs-Ringer-bicarbonate solution and tissue resistance measured during 240 minutes. Tissue permeability to radiolabeled mannitol was also used to assess mucosal barrier integrity. Tissues were examined by light microscopy before and after HOCl exposure and during and after incubation.RESULTS:Exposure to HOCl caused tissue damage and decreased tissue resistance. Restitution did occur during the incubation period. Eosinophils were located near the muscularis mucosae in freshly harvested tissues and migrated towards the luminal surface in response to HOCl-induced injury. Compared with tissues treated with HOCl without acetylcysteine, pretreatment with acetylcysteine prevented HOCl-induced tissue damage, changes in resistance, and histologically detectable eosinophil migration. The permeability to mannitol increased to the same extent in tissues treated with HOCl alone or with acetylcysteine and HOCl.CONCLUSIONS AND CLINICAL RELEVANCE:Eosinophils migrated toward the mucosal surface in equine colon in response to oxidant-induced damage in vitro. This novel finding could be relevant to inflammation in equine colon and a pathophysiologic feature of many colonic diseases. Acetylcysteine protected the mucosa against oxidant-induced injury and may be useful as a treatment option for various gastrointestinal tract disorders in horses.

Objective-To document effects of cisplatin on regenerate bone formation during the distraction and consolidation phases of bone transport osteogenesis.Animals-10 skeletally mature hounds.Procedures-Bone transport osteogenesis was performed to reconstruct a 3-cm defect in the radius of each dog. Five dogs were randomly selected to receive cisplatin (70 mg/m(2), IV, q 21 d for 4 cycles), and 5 were administered saline (0.9% NaCl) solution. Bone mineral density was measured by use of dual-energy x-ray absorptiometry (DEXA) on days 24, 55, and 90 after surgery. Dogs were euthanatized 90 days after surgery. Histomorphometry was performed on nondecalcified sections of regenerate bone. Bone mineral density and histomorphometric indices of newly formed bone were compared between groups.Results-Densitometric differences in regenerate bone mineral density were not detected between groups at any time period. Cisplatin-treated dogs had decreased mineralized bone volume, decreased percentage of woven bone volume, decreased percentage of osteoblast-covered bone, increased porosity, and increased percentage of osteoblast-covered surfaces, compared with values for control dogs. Lamellar bone volume and osteoid volume did not differ significantly between groups.Conclusions and Clinical Relevance-Regenerate bone will form and remodel during administration of cisplatin. Results of histomorphometric analysis suggest that bone formation and resorption may be uncoupled in cisplatin-treated regenerate bone as a result of increased osteoclast activity or delayed secondary bone formation during remodeling. These histomorphometric differences were modest in magnitude and did not result in clinically observable complications or decreased bone mineral density as measured by use of DEXA.

The morphology of fracture healing depends on the mechanical environment afforded by external fixation and ranges between the extremes of direct bone healing and spontaneous hone healing. The mechanical environment at a fracture is affected by the stiffness of the fixator and the degree of load sharing of the fixator with the bone. As the stability of the fracture increases because of increased fixator rigidity, anatomic fracture reduction, or a combination of these factors, callus formation decreases. However, optimal rigidity may consist of early rigid immobilization followed by destabilization of the fixator to allow controlled loading of the fracture site. The biological Environment at the fracture also affects fracture healing with external fixation. Surgical techniques and implants, which compromise the surrounding soft tissue and interfere with the vasculature to the injured bone, will delay bone union. Fixation techniques for severely comminuted fractures using closed reduction and external skeletal fixation allow presentation of soft tissue. These biologically oriented techniques have been termed biological fracture fixation and feature realignment of the limb (i.e., joint surfaces) rather than anatomic reconstruction of the fracture; minimal to no sort tissue dissection; and optimal stability, resulting in moderate strain levels and allowing the progression of bone formation. Fractures treated in this manner seem to heal with endosteal bone formation and bone bridging between fragments rather than with periosteal callus.

Methylmethacrylate plastic mixtures for embedding hard tissues produce highly variable blocks. This study compared 12 mixtures of commercially available plastics to identify a universal embedding medium for a variety of sectioning techniques. Samples of canine humeral heads were embedded in each plastic mixture. Such characteristics as polymerization time, block appearance, and shrinkage were noted; and each block was evaluated during microtomy and ultramilling. The resulting tissue sections were examined for overall appearance and quality following staining. Based on the selected criteria, a mixture of Polysciences methylmethacrylate monomer and Kodak polymethylmethacrylate was superior for both microtomy-and ultramilling. 1n general, the staining results were excellent in sections from all plastic mixtures. Sections from Kodak monomer-based blocks had slightly better cellular and tissue morphology but the resultant blocks were suitable only for ultramilling. ( The J Histotechnol 18:45, 1995)

The Salter‐Harris classification system is widely used to describe the anatomical appearance of and predict the prognosis for physeal fractures in canine clinical patients. Salter and Harris classified experimentally induced physeal fractures on radiographic and histological appearance, however, the good prognosis afforded Salter‐Harris type I and II fractures in experimental animals has been questioned for the canine patient. Twelve naturally occurring physeal fractures from five traumatized dogs, who were euthanatized at the request of their owners, and one resected femoral head were examined histologically. Ten of the 13 physeal fractures disrupted the cells in the proliferative zone. The histological appearance of growth plate disruption in the injured animal correlates more closely with the clinical observations of growth retardation than the experimental observation of continued growth after fracture through the hypertrophic zone. The results of this study indicated that considerable damage to the physeal cartilage occurred during the traumatic incident in most of these clinical animal patients.

Toluidine blue stain has been widely used for staining undecalcified bone sections, but previous techniques required removal of embedding plastic or surface etching with both alcohol and acid solutions. In this study, solutions of toluidine blue at different pHs were used to stain unetched and acid-etched sections. A group of the test staining solutions were heated in an effort to enhance section staining. Acid-etching prior to staining was found to be necessary to achieve bone matrix staining, but methanol etching could be eliminated if staining solutions were heated to 55-60 degrees C. Sections stained with the heated solutions buffered to pH 7.0 or 8.0 had optimum morphology.

A histochemical stain for acid phosphatase served as a marker for lysosomal alterations in renal tubular cells associated with male rat hyaline droplet nephropathy. Morphometric analysis and quantitative histochemistry were used to compare the size and acid phosphatase stain reaction of lysosomes in tubular epithelial cells of treated and control animals. Decalin exposure increased the size and significantly ( p < 0.01) reduced the acid phosphatase stain intensity of individual lysosomes. However, there was no significant different ( p > 0.05) between the acid phosphatase stain intensity of treated and control animals when analyzed on a whole cell basis. The increase in size of the lysosomes without a proportional increase in whole cell acid phosphatase stain intensity indicates a dilution or a failure to accommodate in the acid phosphatase concentration (stain intensity/μm2) per lysosome. All acid phosphatase stain reaction product was contained within intact lysosomes, mitigating against the hypothesis of lysosomal enzyme leakage as the cause of cell death in decalin-induced alpha 2U globulin nephropathy.

A tape-transfer technique for reducing technical problems associated with the sectioning of large paraffin blocks is described. Ten different tapes were attached to the surface of tissue blocks containing decalcified bone, and sections were cut with a microtome. The tapes were evaluated for adhesion to the block face, ease of handling during sectioning, and removal before staining without disruption of the tissue. 3M Company tape numbers 3710–2 and 3750-G were found to be the most satisfactory. This tape-transfer technique yields excellent quality sections with greater ease, less distortion, and fewer artifacts than unsupported sections do. ( The J Histotechnol 13:207, 1990)

A series of intradiscal injections of chondroitinase ABC was performed in 31 young adult rabbits. Roentgenograms were taken immediately postinjection and were repeated at two, three, five, six, seven, or nine days after injection. All had roentgenographic evidence of disc space narrowing at all stages after the injection. Histologic evaluation of safranin-O fast green-stained sections indicated degradation of proteoglycans in the annulus fibrosus of chondroitinase ABC-injected discs. The cells of the chondroitinase ABC-injected discs, the end plates, and the growth-plate areas of adjacent vertebral bodies appeared unaffected.