Tunnel grafting for wound repair in horses: a novel technique in graft production and placement.

There are several skin grafting methods described in the human and animal literature. Currently, there are five types of free grafts used in horses: pinch and punch grafts, split and full-thickness sheet or mesh grafts and tunnel grafts. Published methods of tunnel grafting describe the use of alligator forceps. The alligator forceps create a poor tunnel and are excessively traumatic to the granulation bed. This technique utilised a 13G Jamshidi needle that was placed across the granulation bed and created a uniform tunnel. The Jamshidi needle was atraumatic to the granulation bed increasing the opportunity for graft survival. A twin bladed scalpel allowed for the quick creation of uniform width grafts. Removal of the overlying tunnel 'roof' took place 5-14 days later to allow graft expansion. This case series included five horses with distal limb wounds and one with a wither injury. Four horses required general anaesthesia for graft placement and three required general anaesthesia for the removal of the tunnel roof. The acceptance of the grafts varied from 70% to 100%. Graft expansion to cover the granulation tissue took 2-5 months. This case series demonstrates that this technique of graft production and placement is an easy method for achieving successful skin grafting. Compared to other graft types, tunnel grafts are more readily accepted. Cosmetic and functional results achieved are better than those with pinch and punch grafts. Tunnel grafting does not require expensive equipment or advanced training, and in some cases can be performed under standing sedation.

Unusual cutaneous features associated with a heterozygous gain-of-function mutation in IFIH1: overlap between Aicardi-Goutières and Singleton-Merten syndromes.

Cutaneous lesions described as chilblain lupus occur in the context of familial chilblain lupus or Aicardi-Goutières syndrome. To date, seven genes related to Aicardi-Goutières syndrome have been described. The most recently described encodes the cytosolic double-stranded RNA receptor IFIH1 (also known as MDA5), a key component of the antiviral type I interferon-mediated innate immune response. Enhanced type I interferon signalling secondary to gain-of-function mutations in IFIH1 can result in a range of neuroinflammatory phenotypes including classical Aicardi-Goutières syndrome. It is of note that none of the patients with a neurological phenotype so far described with mutations in this gene was reported to demonstrate cutaneous involvement. We present a family segregating a heterozygous pathogenic mutation in IFIH1 showing dermatological involvement as a prominent feature, variably associated with neurological disturbance and premature tooth loss. All three affected individuals exhibited increased expression of interferon-stimulated genes in whole blood, and the mutant protein resulted in enhanced interferon signalling in vitro, both in the basal state and following ligand stimulation. Our results further extend the phenotypic spectrum associated with mutations in IFIH1, indicating that the disease can be confined predominantly to the skin, while also highlighting phenotypic overlap with both Aicardi-Goutières syndrome and Singleton-Merten syndrome.

Arytenoid mucosal injury in young Thoroughbred horses--investigation of a proposed aetiology and clinical significance.

AIM: To determine whether trauma to the larynx caused by nasotracheal intubation induced mucosal ulceration of the arytenoid cartilages of adult horses, and to determine the incidence of such ulceration in yearling Thoroughbred horses and its effect on athletic performance. METHODS: Laryngeal trauma was induced in a group of 21 adult horses by introduction of a nasogastric tube into the trachea three times within 5 min. Injury to the arytenoid cartilages or vocal cords was subjectively assessed immediately after intubation, and thereafter at weekly intervals for 10 weeks. The outcome and athletic performance of 33 Thoroughbred yearling horses with idiopathic disease of the arytenoid cartilages, diagnosed at the yearling sales, were evaluated and compared to those of control horses of the same gender and age, from the same sale. RESULTS: Mucosal injury was noted immediately after intubation in every horse. Evidence of injury to the vocal or corniculate processes of the arytenoid cartilages or vocal cords was still apparent in 10/21 (48%) horses 1 week after intubation, five of which developed persistent lesions that remained present and unchanged from 28 days following intubation until the end of the 10-week observation period. All persistent lesions were nodules or focal swellings of the vocal cords or arytenoid cartilages, and there was no evidence of mucosal ulceration, infection or discharge. Mucosal ulceration of the vocal processes was the most common abnormality detected in the yearlings, affecting 16/33 (48%) that were diagnosed with idiopathic arytenoid disease at the yearling sales. Five of the 33 (15%) horses were diagnosed with arytenoid chondritis at the time of sale and were excluded from the performance outcome analysis. Of the 28 horses diagnosed with arytenoid abnormalities excluding chondritis, 19 (68%) raced with no history of respiratory-related problems, two (7%) were subsequently diagnosed with laryngeal hemiplegia, and seven (25%) were lost to follow-up. The case animals were 2.7 times more likely to race than control horses, but there was no difference between cases and controls in the likelihood of starting more than three times. CONCLUSIONS: This study showed that nasotracheal intubation in adult horses could result in immediate mucosal trauma, persistent swelling, and focal scarring of the arytenoid cartilages, but this did not mimic mucosal ulceration or chondritis of the arytenoid cartilages observed in yearling Thoroughbred horses. The population studied, however, may not accurately represent the population in which idiopathic disease occurs. In this study, arytenoid mucosal ulceration detected at sale did not commonly progress to arytenoid chondritis. However, a study of a larger population of horses with untreated, naturally occurring disease is required to confirm these findings. CLINICAL RELEVANCE: It is unlikely that trauma from nasogastric intubation caused arytenoid mucosal ulceration, therefore this procedure should not necessarily be discouraged. This study did not find evidence that horses diagnosed with arytenoid mucosal ulceration at yearling sales had a reduced performance history, therefore it is reasonable to continue to pass horses with uncomplicated arytenoid mucosal ulceration during post-sale endoscopic examination. However, monitoring of the lesions and treatment, if required, may be indicated in the post-sale period.

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 5. Kinematic effects.

AIM: To examine the effect of race training on kinematic parameters of the trot in a sample of 2-year-old Thoroughbred fillies. METHODS: Two-year-old Thoroughbred fillies that had been either trained for racing (n=7) or left untrained in small paddocks (n=7) were examined for lameness, and linear and temporal kinematic data were collected from video recordings of each horse trotted in-hand, 5, 9 and 13 weeks after the beginning of training. Horses were graded as: sound (Grade 0), suspected but not obviously lame (Grade 1), or definitely lame at the trot (Grade 2). RESULTS: Mean velocity at the trot did not vary with lameness grade. Compared with horses classified as sound (Grade 0), horses classified as suspected or definitely lame (Grades 1 and 2) had shorter (2.55 (SE 0.02) vs 2.41 (SE 0.02) and 2.44 (SE 0.03) m; p<0.001) and faster (671 (SE 3) vs 645 (SE 1) and 647 (SE 4) msec; p<0.001) strides. None of the linear or temporal parameters measured varied significantly between the successive observation periods. When data from sound horses were pooled, the training group trotted at a higher mean velocity (4.22 (SE 0.08) vs 3.22 (SE 0.06) m/sec; p<0.001) and with a longer stride length (2.79 (SE 0.05) vs 2.18 (SE 0.06) m; p<0.001) than the untrained group. The stride duration was longer (669 (SE 7) vs 662 (SE 9) msec; p=0.01), stance period was shorter (34.1 (SE 0.6) vs 39.3 (SE 0.7) %; p<0.001) and mid-stance was achieved earlier in the stride (12.1 (SE 0.6) vs 13.1 (SE 0.2) %; p=0.001) in the trained than the untrained group. A longer swing phase in the trained group was associated with an increase in retraction time (9.2 (SE 0.2) vs 7.6 (SE 0.3) %; p=0.001). CONCLUSIONS: These data indicate that early race training in young Thoroughbreds was associated with quantifiable changes in linear and temporal kinematic parameters of the trot, which were related to the race-training objective of improving the horse's ability to work at higher velocities. CLINICAL RELEVANCE: Race training resulted in changes in the gait of non-lame horses at the trot, which should be considered during veterinary lameness examinations.

The quantitative assessment of photodensity of the third carpal bone in the horse.

AIM: To determine whether variation in x-ray-beam angle significantly affected photodensity of the third carpal bone (C3) in the horse using the tangential radiographic view, and indirectly determine whether radioabsorptiometry (RA) could be used to assess differences in bone mineral density (BMD) of C3 between exercised and non-exercised horses. METHODS: The left distal carpal row was isolated post-mortem from 2-year-old Thoroughbred horses that had been either exercised (n=7) for up to 14 weeks using a standard training regimen for racehorses, or not exercised (n=7). The effect of variation in x-ray-beam angle on photodensity was determined on these isolated carpal bones in vitro. Image analysis was used to assess photodensity (compared to a known thickness of aluminium) of four regions of interest (ROI) in C3 and one ROI in the fourth carpal bone (C4) of 14 isolated distal rows of carpal bones of the horse. The isolated carpal bones were placed fl at on a x-ray cassette and radiographed at 90 degrees (i.e. with the x-ray beam perpendicular to the cassette). The x-ray-beam angle was varied in the dorsal sagittal plane by 5 degrees increments to a total of 15 degrees from 90 degrees and from a base angle of 60 degrees (the x-ray-beam angle at which the tangential view is taken in clinical cases). RESULTS: Variation in beam angle of <10 degrees from 90 degrees significantly affected photodensity, and photodensity was significantly affected when the angle was varied <5 degrees from 60 degrees . When taken at an x-ray-beam angle of 60 degrees , the abaxial aspect of the radial facet of C3 had a consistently higher photodensity than the rest of C3 and C4. The photodensity of the third and fourth carpal bones was higher in exercised horses than in non-exercised horses. CONCLUSION: As variation in x-ray-beam angle significantly affected photodensity, RA using the tangential view is not considered clinically applicable for assessing BMD of C3 and the accuracy of subjective assessment of BMD of C3 using the tangential view in horses is questionable.

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 1. Study design, and clinical, nutritional, radiological and histological observations.

AIMS: This is the first in a series of papers reporting studies in 2-year-old Thoroughbred racehorses that aimed to determine the response of musculoskeletal tissues to early training on grass and sand racetracks. In this paper, the experimental set-up of the whole study is described, and nutritional, workload, and clinical, radiographic and pathological outcomes are reported, including semi-quantitative assessment of macroscopic changes in articular cartilage. METHODS: The study group comprised 14 two-year-old Thoroughbred fillies reared entirely at pasture. Of these, seven were selected by a licensed racehorse trainer to undergo a 4-week period of initial training in which they were taught to accept saddle and rider, followed by a 13-week period of flatrace training at a racetrack (Weeks 1-13); the other seven fillies were confined to large grass enclosures and were not trained. Nutrient, including macro- and trace-element intakes were estimated. Distances cantered or galloped and average velocities were quantified for the trained horses. All horses were observed daily, weighed approximately weekly, and underwent a clinical lameness examination at Weeks 5, 9 and 13. Distal forelimbs were radiographed prior to Week 1, during Weeks 7-8, and again at the end of the study, when macroscopic changes in articular cartilage of the proximal surface of the proximal phalanx were also scored after staining with India ink. RESULTS: Dietary intakes met or exceeded recommended requirements for all nutrients except sodium, which was low in the trained horses. Bodyweight increased throughout the study in the untrained horses, and increased until Week 7 and then decreased slightly in the trained horses. Mean velocity data were used to define three stages of the training programme: Stage 1 comprised canter in Weeks 1-4; Stage 2 comprised canter in Weeks 5-8; and Stage 3 comprised canter in Weeks 9-13 and galloping twice weekly. Four of seven horses completed training. These covered a mean distance of 179.2 km at mean velocities (excluding gallops) of 7.63 m/sec (SD 0.58), 8.99 m/sec (SD 0.56), and 8.43 m/sec (SD 0.74) for Stages 1-3, respectively, and galloped 4.45 km at 14.4 (SD 0.1) m/sec. The three horses that did not complete training became lame in Weeks 9, 10 and 11, and covered 147.9 km at velocities of 7.38 m/sec (SD 0.44), 8.88 m/sec (SD 0.33) and 8.43 m/sec (SD 0.59) and galloped 2.1 km. Overall, slight or intermittent lameness in trained horses was noted on 76/655 (12%) of horse observation days. Swelling was evident on 284/655 (41%) of horse observation days in the metacarpophalangeal (MCPJ) and metatarsophalangeal (MTPJ) joints (92%), palmar metacarpal tendon region (7%) or carpus (1%). Swelling of the MCPJ or MTPJ was not associated with obvious lameness. Radiographic changes were minor and no gross lesions in bone or tendon tissue were evident except for one case of dorsal metacarpal disease. Post mortem, the cartilage of some MCPJ and MTPJ had obvious wear lines and high lesion scores, which were not consistently related to clinical evidence of pain, lameness or joint swelling. Mean lesion scores were not significantly different between the MCPJ and MTPJ, or between trained and untrained horses. CONCLUSIONS: Workload can be readily quantified in racehorses under semi-commercial training conditions. Obvious lesions in cartilage of the MCPJ or MTPJ were present in some trained and some untrained horses and not consistently associated with clinical evidence of lameness, joint swelling or change in other connective tissues. CLINICAL RELEVANCE: Workload data in racing horses are likely to be highly relevant for studying the pathogenesis of changes in bone, tendon and cartilage during training, for training management and for risk analysis in racehorse populations. Although obvious cartilage lesions produced little clinical effect, such lesions have previously been shown to be progressive and to prejudice athletic capability. Detection of such occult lesions in young horses will require more sophisticated detection methods.

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 3. In vivo ultrasonographic assessment of the cross-sectional area and echogenicity of the superficial digital flexor tendon.

AIM: To determine if the superficial digital flexor tendon (SDFT) of young Thoroughbred horses changed in size and echogenicity in association with early race training. METHODS: Cross-sectional area (CSA) and echogenicity were determined ultrasonographically at five levels of the SDFT of the forelimbs of 2-year-old fillies (n=14), corresponding to 4, 8, 12, 16 and 20 cm distal to the accessory carpal bone (DACB). Measurements were made before and after a 13-week period in which a trained group of seven horses was compared with another group of seven untrained horses. RESULTS: Level below the accessory carpal bone had a significant effect on CSA and Level 8 was smaller than all other levels except Level 12, while Level 12 was smaller than Levels 4 and 20 but not different from Levels 8 and 16. There was a significant interaction between level and time due to effects observed at Level 8. The CSA at Level 8 measured pre-training was different from that of Levels 4 and 20 in both pre- and post-training groups (p<0.05), but when measured post-training was not different from any other measurement. There was also a significant interaction between treatment group and time. There was no difference between CSA for the untrained and trained groups at the pre-training observation (p=0.9), but post-training the CSA (pooled over all levels) in trained horses was significantly larger than that of the untrained horses both post-training (p=0.019) and pre-training (p=0.034), and was not different from the pre-training CSA recorded in the trained group (p=0.29). Treatment group had no effect on echogenicity (p=0.43), while echogenicity was less at the end of the trial in both trained and untrained horses (p<0.001). CONCLUSIONS: Early training for racing was associated with an increase in mean CSA of the SDFT. Other factors such as age and maturity may play a role in limiting this increase.

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 4. Morphometric, microscopic and biomechanical properties of the digital tendons of the forelimb.

AIM: To determine the weight, volume, density and cross-sectional area (CSA) of the digital flexor tendons, common digital extensor tendon (CDET) and suspensory ligament (SL) of the forelimb of young Thoroughbred horses in early training, and to assess the response to a training programme of known parameters of superficial digital flexor tendon (SDFT) tissue at mid-metacarpal level. METHODS: The tendons of seven 2-year-old Thoroughbred horses in training were inspected, transected into segments of known length, and compared with those from seven untrained horses matched for age, sex and breed. The weight, volume, density and CSA of each segment, and the crimp angle, histological features, and biomechanical ultimate stress and stiffness of tendon samples from the mid-metacarpal region of the SDFT were determined. RESULTS: There was no macroscopic evidence of swelling or discolouration in any of the tendon segments or cut surfaces. The volumes of SDFT and CDET segments of horses in the trained group were significantly greater than those in the untrained group (p=0.036 and p=0.039, respectively). A greater increase in volume than weight resulted in a lower density in the SDFT but not CDET in trained compared with untrained horses (p=0.038). CSA of these two tendons was significantly greater in the trained group (p=0.002 and 0.036, respectively), the percentage increase being greater in the CDET than the SDFT. The number of tenocytes at four sites in the mid-metacarpal SDFT region was less in trained than untrained horses (p=0.025). There was no histological evidence of inflammation, and no difference in crimp angle between groups. There was no significant between-group difference in stiffness or ultimate stress of tendon strips. CONCLUSIONS: Volume and CSA of the SDFT and CDET were larger in trained than untrained horses. The SDFT was less dense in the trained group. Because no evidence of tendonitis was detected and training appeared to have no significant effect on crimp angle or biomechanical properties of tendon strips, the size and density changes were presumed to be adaptive and induced by the training. CLINICAL RELEVANCE: Although evident in this in vitro study, the detection of adaptive from initial pathological increase in size of the SDFT is likely to be difficult in vivo.

Pathophysiology and diagnosis of third carpal bone disease in horses: a review.

Third carpal bone (C3) disease is a significant cause of lameness in Standardbred and Thoroughbred horses. The bone density of C3 increases as a result of exercise, reducing the compliance of the bone and predisposing it to injury. Currently, the most widely used method of diagnosis is subjective radiography using the tangential view. Radiographically, increases in bone mineral density (BMD) appear as sclerosis but it is not known at what point increases in sclerosis indicate the onset of disease or increased risk of C3 fracture. A quantitative assessment of the BMD of C3 in horses would improve understanding of the changes that occur within this bone and guide athletic management, as it is thought that BMD changes precede articular cartilage damage. Methods of non-invasive bone-mineral analysis used for the detection of osteoporosis in humans include single photon absorptiometry (SPA), dual x-ray absorptiometry (DXA), computed tomography (CT), radioabsorptiometry (RA), quantitative ultrasonography (QU) and magnetic resonance imaging (MRI). To date, DXA and RA are the most commonly used methods of quantitative non-invasive bone-mineral analysis in horses. The cost of equipment and difficulties in performing DXA in live animals preclude the routine use of this technique for diagnostic purposes. RA may become clinically applicable to C3 analysis in horses, but small variations in x-ray beam angle when taking the tangential view significantly affect results, making this technique clinically inapplicable at this time. Currently, methods of quantitative non-invasive bone-mineral analysis of C3 in horses are not suited to clinical application.

Modes of local drug delivery to the musculoskeletal system.

A number of methods for the local delivery of drugs to musculoskeletal tissues in the horse are now available. Further research is required to document the disposition of drugs delivered by such methods and to correlate this information with efficacy. Perhaps the greatest potential area for the methods discussed is the treatment of synovial and bone infections. To be able to provide high and sustained therapeutic concentrations of antimicrobials to the site of infection should increase the chances of success in such cases. These methods of drug delivery need to be used in conjunction with other management procedures, however, including bacterial culture and sensitivity procedures, systemic antimicrobials, surgical drainage, removal of dead bone or surgical implants, establishment of fracture stability, use of autogenous bone grafts, systemic NSAIDs, and rest.

The effect of dexamethasone on some immunological parameters in cattle.

Immunosuppression as a consequence of acute and chronic stress can increase the susceptibility of cattle to a range of infectious diseases. In order to develop a panel of immune function assays for investigating the effects of potential stressors on immune competence in cattle, the effect of treatment with short- and long-acting preparations of the synthetic glucocorticoid dexamethasone was examined. Short-acting dexamethasone (dexamethasone sodium phosphate 0.08 mg/kg) followed 37 h later by long-acting dexamethasone (dexamethasone-21 isonicotinate 0.25 mg/kg) was injected intramuscularly and blood was collected to assess immune functions at intervals over the subsequent 11 days from 6 treated and 6 control Hereford steers. Dexamethasone induced leukocytosis (neutrophilia, eosinopenia, lymphopenia, monocytosis), an increased neutrophil:lymphocyte ratio, an elevated percentage of CD4+ lymphocytes, a decreased total CD8+ lymphocyte count, decreased total and percentage WC1+ lymphocytes, an elevated percentage of IL-2 receptor alpha (IL-2Ralpha)+ lymphocytes, and an elevated percentage of B lymphocytes. In vitro chemotaxis of peripheral blood neutrophils to human C5a and ovine IL-8 was increased by dexamethasone treatment. Lymphocyte proliferation in the presence of phytohaemagglutinin, and serum concentrations of IgM, but not IgA or IgG1, were suppressed by dexamethasone treatment, whereas mitogen-induced production of interferon-gamma (IFN-gamma), neutrophil expression of CD18, neutrophil myeloperoxidase activity and natural killer (NK) cell activity were not influenced by dexamethasone treatment. The results indicate the potential for haematology and immune function assays to reflect elevated activity of the hypothalamic-pituitary-adrenocortical axis in cattle. Immunological parameters may thus provide a useful adjunct to cortisol and behavioural observations for assessing the impact of stress on the welfare of cattle.

Acrylamide and 2,5-hexanedione induce collapse of neurofilaments in SH-SY5Y human neuroblastoma cells to form perikaryal inclusion bodies.

Neurofilament accumulations are characteristic of a number of neurological conditions including amyotrophic lateral sclerosis, giant axonal neuropathies and several chemically-induced neuropathies. Although the mechanism(s) leading to neurofilament accumulation are unknown, it is possible that similar processes occur both in disease and in chemically-induced neuropathies. Understanding the mechanism(s) of chemically-induced neurofilament accumulation, which is more amenable to experimental manipulation, may give insight into the neurological diseases they mimic. We have compared the effects of two chemically-dissimilar neurotoxins, 2,5-hexanedione and acrylamide, on neurofilaments in the human neuroblastoma cell line, SH-SY5Y. Both undifferentiated and differentiated SH-SY5Y cells were exposed to 2,5-hexanedione or acrylamide and changes in cytoskeletal organization examined by immunofluorescence and electron microscopy. Although distinct morphological differences have previously been characterized in the neuropathies induced by 2,5-hexanedione and acrylamide in vivo, we have found that both compounds had similar direct effects on neurofilaments in SH-SY5Y cells, inducing formation of perikaryal inclusion bodies. In addition, differentiated SH-SY5Y cells were more sensitive to both 2,5-hexanedione and acrylamide compared with undifferentiated cells. These similar effects of 2,5-hexanedione and acrylamide lend further support that a common mechanism(s) may lead to neurofilament accumulation in these neuropathies. SH-SY5Y cells provide a useful model to investigate further the biochemical basis of neurofilament accumulation.

Tendonitis of the branches of insertion of the superficial digital flexor tendon in horses.

OBJECTIVE: To describe clinical findings, ultrasonographic features and outcome of injury to the branches of insertion of the superficial digital flexor (SDF) tendon in horses. DESIGN: Retrospective study of 14 cases. PROCEDURE: Fourteen Thoroughbred horses with tendonitis affecting the branches of insertion of the SDF tendon were examined for lameness, location and amount of swelling, and the presence of other musculoskeletal abnormalities. The flexor tendons were assessed by ultrasonographic examination, and recommendations were made for management of the cases. Outcome was assessed by re-examination of some horses, direct communication with the owner or trainer, and examination of race records. RESULTS: The lateral SDF branch was affected in 10 horses; the medial branch in three, and both branches in one horse. Two horses had concurrent injuries to the SDF tendon in the metacarpal region of the contralateral limb. Ultrasonographic findings included swelling of the affected SDF branch, peritendinous fluid accumulation, disruption of normal fibre alignment on sagittal scan, and variable loss of echogenicity. As healing occurred, there was return of normal echogenicity, but normal fibre alignment did not return completely and apparent adhesions formed between the affected SDF branch and adjacent structures. Seven of 10 horses which returned to their previous use were able to compete without further tendon injury. Recurrence of injury occurred in one case, and another two horses developed tendonitis in the metacarpal region. One horse was retired from racing but was able to compete at dressage without recurrence of injury. Two horses were retired for breeding without returning to training, and one horse was sold and lost to follow up but did not race. CONCLUSION: The prognosis is fair for return to previous use following injury to the branches of insertion of the SDF tendon in athletic horses.

Endoscopic observations on laryngeal symmetry and movements in young racing horses.

An endoscopic survey of young race horses was performed to examine the prevalence and character of laryngeal movements during quiet respiration. The main aim was to determine whether those arytenoid movements which could possibly reflect the efficiency of left dorsal cricoarytenoid muscle function changed over a period of time. Of the 452 horses examined, 439 were Thoroughbreds and 23 were Standardbreds, 250 were less than 2 years of age (6-21 months), and 202 were 2 years old. One hundred and nine of these horses were examined again 16 months later. Arytenoid movements were given one of four grades. Grades 1 and 2 were considered normal and unlikely to be the result of abnormal left dorsal cricoarytenoid muscle function, whilst grades 3 and 4 were considered likely, or almost certainly, the result of abnormal left dorsal cricoarytenoid muscle function. The percutaneous prominence of the muscular process of left and right arytenoid cartilages, endoscopic arytenoid movement on left and right sides, age, sex and breed was recorded. Chi squared analysis was used to determine the association between age, breed, sex and the other recorded variables, and the presence or absence of abnormal laryngeal movements. At the first examination, 48% of the horses had grade 1, 37% grade 2, 15% grade 3 and 0.2% grade 4 left laryngeal movements. Of the horses examined I6 months later, 52% had grade 1, 33% grade 2, 14% grade 3 and 1% grade 4 left laryngeal movements. Fifteen percent of horses with grade 1 and 9% with grade 2 initially were found to be grade 3 at the subsequent examination. Conversely, 53% of horses with grade 3 initially were found to be grade 1 and 21% grade 2 at the subsequent examination. One horse that was grade 3 at the initial examination was grade 4 at the subsequent examination. Overall, 43% of horses were graded the same, 29% were given a better grade and 28% were given a worse grade. Age and sex were not associated with abnormal left laryngeal movements. The presence of abnormal arytenoid movements was significantly less in Standardbreds, but significantly higher in those horses that had a more prominent muscular process of the left arytenoid cartilage. The number of grade 2 and 3 laryngeal movements recorded on the left side was significantly higher than the right. It was concluded that asymmetrical laryngeal movements are common in young race horses; at this age laryngeal movements may interchange between what is considered normal and abnormal; the proportion of young horses with normal or minor variations in their left arytenoid movements that develop more obvious degrees of asynchrony is low (12%); and the proportion of horses considered to have endoscopic evidence of deficient left abductor muscle function that eventually develop laryngeal hemiplegia is also low (5%).

The effect of dexamethasone on immunological memory to tetanus toxoid in sheep.

One of two groups of sheep was immunosuppressed with the glucocorticoid, dexamethasone, at the time of the first but not of the second of two booster vaccinations with tetanus toxoid given at an interval of 28 days. Treatment with dexamethasone decisively reduced the anti-tetanus antibody response to the first booster vaccination and affected both IgM and IgG1 antibody. However, antibody titres increased after the second booster vaccination in the treated sheep and were similar in size to those in the untreated sheep which rose in stepwise fashion after each booster vaccination. The differences in response imply that processes involved in displaying an anamnestic response and recalling previously established memory are sensitive to glucocorticoids. Accordingly, they can be separated from the glucocorticoid-resistant processes that lead to the expansion of immunological memory following multiple exposures to an antigen.

Treatment of a comminuted frontal-plane fracture of the distal phalanx in a horse.

Successful treatment of a comminuted frontal plane fracture of the distal phalanx in a horse is described. The bone fractured through the solar canal, close to the insertion of the deep digital flexor tendon. A hoof case was used to reduce bending and tensile stresses on the solar surface by limiting expansion of the hoof wall during weightbearing. In addition, the heel was elevated, using 3 degrees wedge pads incorporated within the hoof cast, to reduce distraction at the fracture site caused by the pull of the deep digital flexor tendon. Two casts were used over a 4-month period. Complete radiographic healing of the fracture was evident 4 months after injury. At this time the horse was lame at the trot. The owner reported the horse to be sound 7 months after injury. Reexamination 12 months after injury revealed a clinically normal foot and no lameness.

Aneurysm of the cranial mesenteric artery in a cow.

Exploratory laparotomy of an adult dairy cow, examined because of acute signs of persistent abdominal pain, revealed a firm pulsatile mass with associated fremitus just distal to the origin of the cranial mesenteric artery. The cow died acutely 2.5 days after surgery. A dilated, thin-walled, sacculated aneurysm, which had ruptured, was located along the proximal portion of the cranial mesenteric artery. It was postulated that the aneurysm developed secondary to structural defects in the arterial wall, but caused no clinical signs until enlargement and local tissue stretching or circulatory disturbances caused intestinal ischemia, resulting in abdominal pain. Aneurysms of visceral arteries in cattle should be considered as another differential diagnosis for signs of abdominal pain after more common causes such as severe bloat, mesenteric root volvulus, intussusception, cecal dilatation/volvulus, and uterine torsion have been excluded.