Histochemical study of normal and collapsed tracheas in dogs

Tracheas from 15 toy breed dogs with normal tracheas and 6 dogs with collapsed tracheas were examined histologically and histochemically. Tracheal cartilage was analyzed for chondroitin sulfate by means of alcian blue (CEC method) and for calcium with alizarin red S. Cartilage arcs from dogs with collapsed tracheas had areas that were apparently hypocellular, and some had other areas that appeared like fibrocartilage or fibrous tissue. Histochemically, collapsed tracheal cartilage had less chondroitin sulfate and calcium than did normal tracheal cartilage. Cartilage arcs from the collapsed tracheas were not uniformly affected to the same degree, and parts of a given tracheal arc appeared normal, whereas other parts had an abnormal histologic appearance.     

Partial tracheal obstruction due to chondromas in ball pythons (Python regius).

Over a 9-mo period, three adult ball pythons (Python regius) (one male, two females) were evaluated for severe dyspnea. Partial obstructions of the tracheal lumen were identified radiographically and/or visualized with a 3.0-mm rigid laparoscope inserted into the tracheal lumen in all three snakes. Administration of systemic antibiotics and nebulization resulted in partial improvement of the dyspnea. In two snakes, the tracheal lesions were removed with a rigid laparoscope and a flexible biopsy instrument inserted into the tracheal lumen. The other snake died and was necropsied. Histologically, the lesions from two snakes were determined to be benign chondromas. The chondromas were composed of a variably disorganized chondroid matrix populated by quiescent, normal-appearing chondrocytes within lacunae, although the chondrocytes were increased in density compared with normal hyaline cartilage and contained rare mitotic figures. The tracheal masses in one snake grew by expansion, not invasion, and were focally continuous with a mineralized cartilage tracheal ring, suggesting a benign nature. This is the second report of tracheal chondroma in ball pythons. Tracheal chondromas are exceedingly rare in humans and domesticated animals, suggesting a possible predisposition of ball pythons for this neoplasm.     

Observations on the pathology of tracheal collapse in dogs

The pathology of tracheal collapse in dogs is described. Ten dogs were studied and in all cases there was macroscopic and histological evidence of flattening of the tracheal cartilage and peripheral lung disease. It was considered that the essential lesion was a removal of organic matrix from the cartilage. It was thought that this was probably congenital in origin but required the presence of concurrent lung disease as a triggering factor before clinical signs developed.     

Ultrastructure of canine articular cartilage: comparison of normal and degenerative (osteoarthritic) hip joints.

Normal canine hip cartilage was compared with cartilage from the degenerative lesions found in young dogs with canine hip dysplasia. The upper 0.5 mm of normal cartilage was characterized. Four distinct layers or zones were found: a layer of fine fibrous material covering the surface, a layer (surface layer) of small (32 nm diameter or less) collagen fibrils tightly packed in bundles and oriented parallel to the surface, a layer (upper layer) or less tightly packed collagen fibrils oriented mostly parallel to the surface with about 33% of the fibrils 64 nm or more, and a layer (intermediate layer) of randomly oriented fibrils with more than 50% of the fibrils 64 nm or larger. Fibril density was high in the surface layer and decreased with depth into the cartilage. In a moderately advanced lesion of degenerative cartilage, there was a layer of amorphous material over the surface. The tightly packed surface layer of small fibrils was absent. The surface itself was uneven and fissued. At depths from the surface comparable to the upper and the intermediate layers in normal cartilage, the proportion of large fibrils was less than in normal cartilage. The overall density of fibrils in degenerative cartilage increased with depth into the tissue. Cells flattened parallel to the surface, with relatively large nuclei, were found in the upper layer of normal cartilage. Cells in the intermediate layers were larger and round. The oblong cells of the upper layer of normal cartilage were not found in any layer of degenerative cartilage. Differences between cells in other layers of normal and degenerative cartilages were minimal. A model for the arrangement of chondrocytes and collagen fibrils for normal and degenerative cartilage was proposed. Ultrastructural changes in degenerative cartilage were prominent in the upper 0.5 mm of cartilage. These changes were changes in the number of collagen fibrils/mum-2 and a change from a characteristic pattern of collagen fibril diameters and orientation found in normal tissue.     

Age related changes and osteochondrosis in swine articular and epiphyseal cartilage: light ane electron microscopy.

Age related changes and osteochondrosis in swine were studied using light microscopy and electron microscopy in articular cartilage and light microscopy and epiphyseal cartilage of swine from three days to 30 weeks of age. Thickness, cellularity and vascularity of both the epiphyseal and articular cartilage, decreased as the swine aged. Osteochondrotic changes included formation of "plugs" of cartilage indicating localized failure of ossification and separation and space formation in epiphyseal cartilage. Eosinophilic streaks and space formation in epiphyseal cartilage was observed in relation to epiphyseal separation. Electron microscopy showed a continuous fibrillar layer on the surface of the cartilage corresponding to the lamina splendens of light microscopy. This layer increased in the thickness and showed accumulation of amorphous material between the fibrils with aging. In the matrix, the orientation and distribution of the collagen fibers changed with growth and thicker fibers with clear sub banding were more common in older age groups. Also, necrotic cells, glycogen containing bodies and cellular debris were noticed in the matrix of normal cartilage in old animals. Chondrocytes in the younger cartilage showed accumulation of organelles responsible for protein synthesis; while Golgi bodies, vesicles, lysosomes, well developed foot processes and other inclusions were noticed in older cartilage. Cartilage erosions had a clumped and disrupted lamina splendens on the surface and electron lucent patches in the ground substances of the matrix and chondrocyte cytoplasm.     

COMPUTED TOMOGRAPHY AND POSITIVE CONTRAST COMPUTED TOMOGRAPHIC ARTHROGRAPHY OF THE CANINE SHOULDER: NORMAL ANATOMY AND EFFECTS OF LIMB POSITION ON VISIBILITY OF SOFT TISSUE STRUCTURES

Soft tissue injuries of the shoulder are an important cause of forelimb lameness in dogs. The objectives of this canine cadaver study were to describe normal anatomy of shoulder soft tissue structures using computed tomography (CT) and computed tomographic arthrography (CTA) and to determine the effects of positioning on visualization of shoulder soft tissue structures. Thirteen forelimbs were removed from eight canine cadavers. Two forelimbs were used for contrast dose optimization. For the remaining 11 forelimbs, shoulder CT and CTA were performed using three defined joint angles (140°, 90°, and 70°). For three forelimbs, CT and CTA images were compared with frozen anatomic sections to describe normal anatomy. Ten forelimbs were used for analysis of positioning effects. Soft tissue structures evaluated were the joint capsule, cartilage, ligaments, tendons, and muscles. A visual assessment score was assigned to each structure using a consensus of two observers. The range and mode of scores were calculated and compared for each modality and limb position. The shoulder joint capsule and medial and lateral glenohumeral ligaments were completely visible with CTA. All tendons and muscles were visualized in all the examinations except for the teres minor muscle tendon and the coracobrachialis muscle, which were not visible on all scans. Positioning the limb in an extended position significantly improved visualization of most soft tissue shoulder structures. Shoulder cartilage was best seen with CTA and with neutral or flexed positioning of the shoulder. Findings indicated that both CT and CTA are feasible imaging techniques for visualization of soft tissue structures of the canine shoulder.     

Tracheal Anastomosis in the Dog Comparison of Two End-to-End Techniques

Two techniques for tracheal resection and anastomosis were performed and compared in 20 normal dogs. In one technique, cartilage rings were split circumferentially, and the split rings were apposed with simple interrupted sutures that penetrated the annular ligament. In the other technique, the annular ligaments were incised and apposed with simple interrupted sutures placed through the annular ligament and around the adjacent ring. Endoscopy and xeroradiography were used to evaluate the anastomotic sites at 1, 2, 4, and 8 weeks postoperatively. Infection, mucus accumulation, coughing, stridor, or anastomotic separations were not seen. Stenosis of the anastomotic site was observed in 80% of the dogs, due to the intraluminal protrusion of epithelialized fibrous connective tissue. The split cartilage technique was easy to perform and resulted in less dorsoventral stenosis than the annular ligament technique.     

Measurement of tracheal diameters using ultrasonography versus computed tomography in Beagle dogs

ObjectiveTo compare ultrasonography with computed tomography (CT) for assessment of tracheal diameter as a feasibility study for endotracheal tube selection.Study designProspective study.AnimalsA total of nine Beagle dogs with a median (interquartile range) weight of 7.4 (7.2–7.7) kg.MethodsTracheal diameter measurements were obtained at two locations: 1 cm proximal to caudal border of the cricoid cartilage (sublaryngeal; SL) and dorsal to above cranial border of the manubrium (thoracic inlet; TI). For CT, dogs were anesthetized with propofol and sevoflurane, in sternal recumbency, and measurements obtained after controlled ventilation–induced apnea and the endotracheal tube cuff was deflated. Transverse diameter, right and left 45° oblique diameters were measured. For ultrasonography, unsedated dogs were standing with slight neck extension, and images obtained in ventrodorsal, 45° right and left oblique ways after expiration. Diameters between the tracheal lumen mucosal borders were measured. The degree of agreement between the tracheal diameters measured at SL and TI locations with CT (TD_CT-SL and TD_CT-TI) and ultrasonography (TD_US-SL and TD_US-TI) was verified using the Bland-Altman method.ResultsThe agreement between the measurements obtained with CT and ultrasonography was revealed by Bland-Altman analyses, although ultrasonography tended to slightly underestimate the tracheal diameter.Conclusions and clinical relevanceUltrasonography can be applied for tracheal diameter measurement. Although further studies are required, an endotracheal tube selection method, using ultrasonography, could be proposed.     

Morphological study of tracheal shape in donkeys with and without tracheal obstruction

Reason for performing study: There is limited information on the gross tracheal morphology of donkeys with or without tracheal abnormalities. Objectives: To: 1) examine the morphology of tracheas of donkeys with and without clinical and/or post mortem evidence of tracheal obstruction; 2) record the cross‐sectional dimensions and shapes of tracheal rings at fixed sites; and 3) document prevalence, sites and characteristics of detected tracheal abnormalities. Methods: The tracheas of 75, predominantly aged (median age 30 years, range 7–48 years) donkeys that died or were subjected to euthanasia on humane grounds were examined. Five had severe dyspnoea due to tracheal obstruction (with intercurrent lung disease in 3), while 7 had post mortem evidence of severe tracheal airway obstruction. Every 5th tracheal ring was dissected free and the inner and outer vertical and transverse dimensions and cross sectional areas were measured. Each dissected ring was photographed and the shape of the trachea was classified as normal or, in one of 6 abnormal grades, according to the type and degree of structural abnormality present. Results: The tracheas had a mean of 43 (range 34–50) tracheal rings that tended to be more oval in shape in the distal cervical region. Only 31.2% of rings examined had a circular to oval shape. Dorso‐ventral flattening was present in 0.9% of tracheal rings, dorsal ligament separation in 24.4%, slight cartilage deformity in 26.0%, moderate cartilage deformity in 10.4%, marked cartilage deformity in 1.9% and miscellaneous other abnormalities in 4.9% of tracheal rings. The 12 donkeys with ante or post mortem evidence of tracheal obstruction had significantly increased tracheal abnormality grade in comparison to the remaining donkeys. Conclusions and potential relevance: Structural tracheal abnormalities are present in most old donkeys, but generally do not cause clinical problems in these sedentary animals unless intercurrent pulmonary disease is present.     

COMPUTED TOMOGRAPHIC ARTHROGRAPHY OF THE NORMAL CANINE ELBOW

Comprehensive evaluation of canine elbow joint dysfunction includes assessment of articular cartilage, which can noninvasively be performed with contrast arthrography. Aims of this prospective study were to compare positive contrast computed tomographic (CT) arthrography and histomorphometry measures of cartilage thickness in normal canine elbows, and to determine the optimal contrast medium concentration. Thirty‐two canine cadaver elbows were examined using multidetector CT, before and after intra‐articular administration of iohexol at one of three different concentrations. Articular cartilage thickness was measured on both the CT arthrography images and corresponding histologic specimens. Mean difference (bias) between the CT arthrography and histomorphologic measurements was 0.18 and 0.19 mm in the sagittal and dorsal planes, respectively. Mean bias and precision of CT arthrography measurements made in the sagittal or dorsal reformations were not significantly different from one another. Computed tomographic arthrography measurements from elbows with 75 mg I/ml were significantly larger and had greater bias compared to other contrast medium groups (150 and 37.5 mg I/ml). There was no significant difference in CT arthrography measurement precision between different contrast medium concentrations. Histomorphologic thickness of the articular cartilage overlying the cranial aspect of the ulna (mean 0.32 mm) was significantly thinner than cartilage of the radius (0.36 mm) or humerus (0.36 mm). Findings from this cadaver study indicated that CT arthrography delineates articular cartilage of the normal canine elbow; yields cartilage thickness measures slightly greater than histomorphometry measures; and provides high measurement precision regardless of image plane, contrast medium concentration, or anatomic zone.     

Changes in molecular expression of aggrecan and collagen types I, II, and X, insulin-like growth factor-I, and transforming growth factor-beta1 in articular cartilage obtained from horses with naturally acquired osteochondrosis.

OBJECTIVE: To determine molecular changes in the expression of insulin-like growth factor-I (IGF-I) and transforming growth factor-beta1 (TGF-beta1) in horses with osteochondrosis, and to characterize expression of matrix aggrecan and collagen types I, II, and X in articular cartilage of affected joints. SAMPLE POPULATION: Articular cartilage from affected stifle or shoulder joints of 11 horses with naturally acquired osteochondrosis and corresponding joints of 11 clinically normal horses. PROCEDURE: Harvested specimens were snap frozen in liquid nitrogen, and total RNA was isolated. Specimens were fixed in 4% paraformaldehyde for histologic examinations. Expression of matrix molecules was assessed by analysis of northern blots and in situ hybridization, using equine-specific cDNA probes and riboprobes, respectively. Expression of IGF-I and TGF-beta1 was assessed by use of noncompetitive quantitative polymerase chain reaction, in situ hybridization, and immunohistochemical analysis. RESULTS: Cartilage obtained from osteochondrosis lesions had significantly greater expression of IGF-I, compared with normal cartilage. Expression of TGF-beta1 and collagen type I were higher, but not significantly so, in affected tissues. Expression of aggrecan or collagen types II and X did not differ between affected and clinically normal cartilage. CONCLUSIONS AND CLINICAL RELEVANCE: Increased expression of growth factors and collagen type I was found in cartilage from osteochondrosis lesions. However, this probably reflects a healing response to injured tissue rather than a primary alteration. Therefore, methods aimed at altering concentrations of growth factors in cartilage of growing horses would be unlikely to alter the incidence or progress of the disease.     

Effects of intramuscular polysulfated glycosaminoglycan on chemical and physical defects in equine articular cartilage.

The effect of intramuscular polysulfated glycosaminoglycan (PSG) on repair of cartilage injury was evaluated in eight horses. In each horse, one middle carpal joint had both a partial-thickness and a full-thickness articular cartilage defect created. In the contralateral middle carpal joint, chemical articular cartilage injury was created by intra-articular injection of 50 mg sodium monoiodoacetate (MIA). Horses were divided into two groups for treatment. Group 1 horses (control) received an intramuscular injection of normal saline every four days for a total of seven injections starting seven days after cartilage injury. Group 2 horses received 500 mg of PSG intramuscularly every four days for seven treatments starting seven days after cartilage injury. Horses were maintained for 12 weeks. Horses were evaluated clinically, and their middle carpal joints were evaluated radiographically and arthroscopically at the end of the study. Joint tissues were also collected and examined microscopically. The only significant difference between groups was slightly greater matrix staining intensity for glycosaminoglycans in the radiate articular cartilage layer in MIA injected and PSG treated joints. Partial-thickness defects had not healed and the predominant repair tissue in full-thickness defects was fibrous tissue. It was concluded that using this joint injury model, 500 mg PSG administered intramuscularly had no effect on the healing of articular cartilage lesions, and minimal chondroprotective effect from chemically induced articular cartilage degeneration.     

COMPUTED TOMOGRAPHIC,RADIOGRAPHIC, AND ENDOSCOPIC TRACHEAL DIMENSIONS IN ENGLISH BULLDOGS WITH GRADE 1 CLINICAL SIGNS OF BRACHYCEPHALIC AIRWAY SYNDROME

Tracheal hypoplasia is commonly seen in English Bulldogs affected with brachycephalic airway syndrome. Previously published diagnostic criteria for tracheal hypoplasia in this breed have been a radiographic tracheal diameter:tracheal inlet ratio (TD:TI) < 0.12 or a tracheal diameter:third rib diameter ratio (TD:3R) < 2.0. Computed tomography has become increasingly used for airway evaluation, however published information is lacking regarding CT tracheal dimensions in English Bulldogs. Objectives of this prospective cross‐sectional study were to describe radiographic and CT tracheal dimensions in a sample of clinically normal English Bulldogs and compare these values with tracheoscopy scores. Computed tomography (n = 40), radiography (n = 38), and tracheoscopy (n = 40) studies were performed during a single general anesthesia session for each included dog. Tracheal measurements were recorded at three locations: cervical, thoracic inlet, and thorax. Tracheal diameters were narrowest at the thoracic inlet with all techniques. Computed tomographic measurements averaged 19% greater than radiographic measurements. All included dogs had radiographic tracheal measurements greater than the previously published criteria for tracheal hypoplasia. Mean CT TD:TI was 0.26 (± 0.03, 0.20–0.33), and mean CT TT:3R was 2.27 (± 0.24, 1.71–2.74). Radiographic TD:TI and CT TD:TI were significantly correlated (P = 0.00); however radiographic TT:3R and CT TT:3R were not significantly correlated (P = 0.25). Tracheoscopy identified hypoplastic changes in all dogs and tracheoscopy scores were not correlated with CT or radiography diameter measurements. In conclusion, findings indicated that some CT and radiographic tracheal diameter measurements were comparable in English Bulldogs however diameters for both imaging techniques were not comparable with tracheoscopy scores.     

Morphologic and biochemical study of sternal cartilage autografts for resurfacing induced osteochondral defects in horses.

Using biodegradable pins, sternal cartilage autografts were fixed into osteochondral defects of the distal radial carpal bone in ten 2 to 3-year-old horses. The defects measured 1 cm2 at the surface and were 4 mm deep. Control osteochondral defects of contralateral carpi were not grafted. After confinement for 7 weeks, horses were walked 1 hour daily on a walker for an additional 9 weeks. Horses were euthanatized at 16 weeks. Half of the repair tissue was processed for histologic and histochemical (H&E and safranin-O fast green) examinations. The other half was used for the following biochemical analyses: type-I and type-II collagen contents, total glycosaminoglycan content, and galactosamine-to-glucosamine ratio. On histologic examination, the repair tissue in the grafted defects consisted of hyaline-like cartilage. Repair tissue in the nongrafted defects consisted of fibrocartilaginous tissue, with fibrous tissue in surface layers. On biochemical analysis, repair tissue of grafted defects was composed predominantly of type-II collagen; repair tissue of non-grafted defects was composed of type-I collagen. Total glycosaminoglycan content of repair tissue of grafted defects was similar to that of normal articular cartilage. Total glycosaminoglycan content of nongrafted defects was 62% of that of normal articular cartilage (P less than 0.05). Repair tissue of all defects was characterized by galactosamine-to-glucosamine ratio significantly (P less than 0.05) higher than that of normal articular cartilage. These results at 16 weeks after grafting indicate that sternal cartilage may potentially constitute a suitable substitute for articular cartilage in large osteochondral defects of horses.     

Inherited chondrodysplasia in Texel sheep

CASE HISTORY: A skeletal disease characterised by dwarfism, limb deformity and sometimes sudden death occurred over a period of 5 years in lambs born on a commercial sheep farm in Southland. The disease showed variable expression and occurred in crossbred sheep. A genetic aetiology was supported by the birth of affected lambs over two seasons in a flock of putative carrier and affected sheep transported to Massey University.

CLINICAL FINDINGS: Affected lambs appeared normal at birth but showed evidence of dwarfism, wide-based stance and exercise intolerance as early as 1 week of age. Most died within the first 3 months of life, often after developing bilateral varus deformity of the forelimbs. Some severely-affected lambs died suddenly of respiratory embarrassment, probably due to tracheal collapse. Mildly-affected individuals had a short, blocky stature and some survived to breeding age.

PATHOLOGICAL FINDINGS: Gross and microscopic lesions of variable severity were present in the tracheal, articular, epiphyseal and physeal cartilages. In severe cases, articular cartilage in major joints was eroded from weight-bearing surfaces. The trachea was flaccid, abnormally kinked, and had thickened cartilaginous rings and a narrow lumen. Affected sheep that survived to breeding age eventually developed severe degenerative joint disease. Histologically, chondrocytes were disorganised, surrounded by concentric rings of abnormal fibrillar material, and the matrix often contained focal to coalescing areas of chondrolysis.

DIAGNOSIS: Inherited chondrodysplasia of Texel sheep.

CLINICAL RELEVANCE AND CONCLUSIONS: This chondrodysplasia differs from those previously described in sheep and is considered to be a newly-recognised, recessively-inherited genetic disease of the Texel breed. A defect in the synthesis of glycosaminoglycans in cartilage matrix is suspected. This disease of sheep may provide a suitable model for studying various forms of therapy for human chondrodysplasias.     

Inherited chondrodysplasia in Texel sheep

CASE HISTORY: A skeletal disease characterised by dwarfism, limb deformity and sometimes sudden death occurred over a period of 5 years in lambs born on a commercial sheep farm in Southland. The disease showed variable expression and occurred in crossbred sheep. A genetic aetiology was supported by the birth of affected lambs over two seasons in a flock of putative carrier and affected sheep transported to Massey University. CLINICAL FINDINGS: Affected lambs appeared normal at birth but showed evidence of dwarfism, wide-based stance and exercise intolerance as early as 1 week of age. Most died within the first 3 months of life, often after developing bilateral varus deformity of the forelimbs. Some severely-affected lambs died suddenly of respiratory embarrassment, probably due to tracheal collapse. Mildly-affected individuals had a short, blocky stature and some survived to breeding age. PATHOLOGICAL FINDINGS: Gross and microscopic lesions of variable severity were present in the tracheal, articular, epiphyseal and physeal cartilages. In severe cases, articular cartilage in major joints was eroded from weight-bearing surfaces. The trachea was flaccid, abnormally kinked, and had thickened cartilaginous rings and a narrow lumen. Affected sheep that survived to breeding age eventually developed severe degenerative joint disease. Histologically, chondrocytes were disorganised, surrounded by concentric rings of abnormal fibrillar material, and the matrix often contained focal to coalescing areas of chondrolysis. DIAGNOSIS: Inherited chondrodysplasia of Texel sheep. CLINICAL RELEVANCE AND CONCLUSIONS: This chondrodysplasia differs from those previously described in sheep and is considered to be a newly-recognised, recessively-inherited genetic disease of the Texel breed. A defect in the synthesis of glycosaminoglycans in cartilage matrix is suspected. This disease of sheep may provide a suitable model for studying various forms of therapy for human chondrodysplasias.     

Ultrastructural histochemical evaluation of growth plate cartilage matrix from healthy and osteochondritic swine

A contributing factor to the lack of understanding the cause of osteochondritic syndromes has been incomplete knowledge of the morphology of lesions in subclinical stages of the disease. In osteochondritic growth plate cartilage from growing swine, the morphology of the pericellular matrix surrounding hypertrophic zone chondrocytes is abnormal and is characteristic of a matrix in which the ordered interactions of matrix macromolecules with each other and with the plasma membrane have been altered. In the present study, ultrastructural histochemical techniques were used to analyze the nature of macromolecular interactions in the pericellular matrix in normal growth plate cartilage, and selective enzyme digestions of normal growth plate cartilage were used to simulate the morphology found in osteochondritic lesions. Results showed that a pericellular macromolecular material which was both ferrocyanide positive and trypsin sensitive was essential for stabilizing the cell membrane/pericellular interface in normal growth plates. The highly variable morphology of this same material in osteochondritic lesions was simulated by hyaluronidase digestion. Since similar pericellular matrix abnormalities have not been described in other diseases of growth plate cartilage, they may represent a matrix abnormality unique to the vascularization failure of osteochondritic syndromes. Our ability to simulate the ultrastructural morphology of subclinical osteochondritic lesions enhances the potential for understanding the macromolecular changes found in the pericellular matrix of osteochondritic cartilage. Based on these results, a new hypothesis is presented for the early sequence of events in the pathogenesis of osteochondrosis.     

Computed tomographic anatomy of the temporomandibular joint in the young horse

Reasons for performing study: The equine temporomandibular joint (TMJ) and its surrounding structures can be difficult to investigate in cases with a clinical problem related to the region. Little previous attention has been given either to a computed tomographic (CT) imaging protocol for the joint or an interpretation of the structures displayed in CT images of the normal joint. Objectives: To provide a CT atlas of the normal cross‐sectional anatomy of the equine TMJ using frozen and plastinated sections as anatomical reference. Methods: Eight TMJs from 4 immature pure‐bred Spanish horses were examined by helical CT. Scans were processed with a detailed algorithm to enhance bony and soft tissue. Transverse CT images were reformatted into sagittal and dorsal planes. Transverse, sagittal and dorsal cryosections were then obtained, photographed and plastinated. Relevant anatomic structures were identified in the CT images and corresponding anatomical sections. Results: In the CT images, a bone window provided excellent bone detail, however, the soft tissue components of the TMJ were not as well visualised using a soft tissue window. The articular cartilage was observed as a hyperattenuating stripe over the low attenuated subchondral bone and good delineation was obtained between cortex and medulla. The tympanic and petrous part of the temporal bone (middle and inner ear) and the temporohyoid joint were seen in close proximity to the TMJ. Conclusions: Helical CT provided excellent images of the TMJ bone components to characterise the CT anatomy of the normal joint. Potential relevance: Detailed information is provided that may be used as a reference by equine veterinarians for the CT investigation of the equine TMJ and serve to assist them in the diagnosis of disorders of the TMJ and related structures (middle and inner ear). The study was performed at an immature stage and further studies of mature individuals are required in order to confirm that the clinical interpretation is not affected by changes occurring with age.     

The Use of a Silicone T-tube to Treat Tracheal Stenosis in a Llama

A female llama was presented at 4 days of age with severe dyspnea resulting from bilateral choanal atresia. A tracheostomy was performed before surgical treatment of the airway obstruction. Although the choanal atresia was successfully corrected, tracheal stenosis secondary to mucosal necrosis, malacia of the cartilage rings, and proliferation of intraluminal granulation tissue at and distal to the tracheal stoma developed. The affected segment of the trachea was resected and an end-to-end anastomosis was performed, but the lumen again became obstructed by granulation tissue. A silicone "T-tube" was placed in the trachea to provide a patent airway and intraluminal support. The llama has done well for 12 months with this prosthesis, and the complications that are often seen with long-term use of traditional tracheostomy tubes have not developed.     

Polysulfated glycosaminoglycan accelerates net synthesis of collagen and glycosaminoglycans by arthritic equine cartilage tissues and chondrocytes

Low molecular weight polysulfated glycosaminoglycan (PSGAG) stimulated net collagen and glycosaminoglycan synthesis by normal and arthritic equine fetlock cartilage tissues in organ culture. Arthritic tissues were more sensitive to PSGAG stimulation. The rates of cartilage-specific type-II collagen and chondroitin sulfate-rich glycosaminoglycan synthesis by confluent chondrocyte cell cultures obtained from normal and arthritic equine cartilage tissues were increased by 25 and 50 mg of PSGAG/ml. Cells from arthritic cartilage were also more sensitive to the presence of PSGAG. In addition, concentrations of PSGAG (25 and 50 mg/ml) approximate to those in synovial fluid after intra-articular injection of 250 mg of PSGAG inhibited the rate of collagen and glycosaminoglycan degradation in cell culture. These findings suggest that PSGAG may have a role in the healing of mild cartilage degeneration by encouraging the production of replacement hyaline matrix materials, while delaying their subsequent degradation. In contrast, growth of cell cultures was inhibited by PSGAG, suggesting that these compounds may fail to stimulate chondrocyte replication, a prerequisite for tissue regeneration. Nonetheless, these observations provide direct evidence of a truly chondroprotective role for low molecular weight PSGAG in the treatment of equine degenerative joint disease.