BONE SARCOMA FOLLOWING ORTHOVOLTAGE RADIOTHERAPY IN TWO DOGS

In two dogs that received orthovoltage radiotherapy, osteosarcoma developed in irradiated bone 38 and 77 months after treatment. Irridiated bone in one dog was presumably normal prior to radiotherapy; irradiated bone in the other was infiltrated by an acanthomatous epulis. Both osteosarcomas were probably radiation induced. Radiation-induced bone sarcoma is an important, but uncommon, complication of radiaotherapy.     

Canine Axial Skeletal Osteosarcoma A Retrospective Study of 116 Cases (1986 to 1989)

Axial skeletal osteosarcomas were evaluated retrospectively in 116 dogs. Thirty-one tumors occurred in the mandible, 26 in the maxilla, 17 in the spine, 14 in the cranium, 12 in the ribs, 10 in the nasal cavity and paranasal sinuses, and 6 in the pelvis. Medium-sized and large dogs were most commonly affected. Females outnumbered males 2.1:1, but this varied with tumor location. The mean age was 8.7 years. Osteosarcomas of the rib occurred in significantly younger dogs (mean age, 5.4 years) than osteosarcomas at any other axial skeletal site. Pulmonary metastasis was diagnosed radiographically in 11.1% of the dogs. The median survival for dogs treated surgically was 22 weeks, the 1-year survival was 26.3%, and the 2-year survival was 18.4%. The tumor recurrence rate was 66.7%. Most dogs (79.6%) died or were euthanatized for problems associated with the primary tumor.     

The Influence of Castration on the Development of Prostatic Carcinoma in the Dog 43 Cases (1978–1985)

Prostatic carcinoma (PC) was diagnosed in 43 dogs at the Michigan State University Veterinary Clinical Center (MSU-VCC) between 1978 and 1985. Of the 43 dogs with histologically confirmed PC, 19 (44.19%) had been castrated at least three years prior to the development of any prostatic disease. Seven of the castrates had been neutered at less than 12 months of age. Fourteen dogs (32.55%) were presented as intact males at the time of diagnosis. The remaining ten dogs (23.62%) had been castrated as treatment for presumptive prostatic disease prior to referral to the MSU-VCC. Dates of castration were known in all cases. In this study, therefore, castration at any age showed no sparing effect on the risk of development of PC in the dog. The etiology of PC in the dog may not be exclusively related to testicular hormones. Work in humans suggests that the adrenal and pituitary glands play a significant role in the disease. Preliminary work in dogs supports that nontesticular androgens exert a significant influence on the canine prostate.     

CT FEATURES OF ALVEOLITIS AND SINUSITIS IN HORSES

Sinusitis is a common disorder in horses and may result from trauma, dental diseases, or space-occupying lesions. Radiography can only provide a limited amount of information. Computed tomography (CT) has been documented as an alternative imaging method. Eighteen horses (mostly Warmblood) with signs of chronic sinusitis were examined preoperatively with CT to assist in diagnosis of the underlying cause. There was a group of common CT features in horses with dental disease and sinusitis. The first molar was the most frequently affected maxillary cheek tooth. Hypoattenuation of the cementum, destruction of the enamel, and filling of the infundibular cavity with gas were the most frequent CT findings associated with caries. Gas bubbles within the bulging root area or fragmentation of the root in combination with swelling of the adjacent sinus lining were the most important CT features of dental decay. CT findings associated with sinusitis included excessive thickening of the respiratory epithelium in the rostral maxillary sinus; the caudal maxillary sinus was less often involved. The infraorbital canal, the nasomaxillary duct, and the frontomaxillary aperture were usually involved. The maxillary bone, however, especially the facial crest, was involved in nearly every horse, being characterized by endosteal sclerosis, thickening, periosteal reaction, and deformation leading to facial swelling in chronic infections. CT images allowed identification of involvement of individual teeth more clearly to reveal the diseased one for treatment. Three-dimensional imaging allowed improved understanding of the extent and severity of the pathologic change.     

Parainfluenza-3 virus-induced enhancement of histamine release from calf lung mast cells – effect of levamisole

Clinically healthy calves were divided into five groups. Group 1 served as control; Group 2 received levamisole (LEV), 3 mg/kg, s.c.; Group 3 was aerosolized with parainfluenza-3 virus (PI-3); Group 4 received LEV and PI-3 and Group 5 was inoculated with Pasteurella haemolytica. They were killed 6 days after virus exposure or 5-6 days after bacterial inoculation. Lung mast cells were prepared by enzymatic treatment. Mast cell histamine (HIST) release was assayed spectrofluorometrically. Total HIST (micrograms/g) in mast cells was as follows (means +/- SEM): control (5.30 +/- 0.26); LEV (5.27 +/- 0.31); PI-3 (6.37 +/- 0.65); LEV + PI-3 (6.21 +/- 0.51); P. haemolytica (7.06 +/- 0.85). Spontaneous HIST release was as follows (% total, means +/- SEM): control (10.38 +/- 1.09), LEV (11.95 +/- 2.13), PI-3v (73.57 +/- 11.97), PI-3v + LEV (19.50 +/- 3.03), and P. haemolytica (70.59 +/- 5.94). Calcium ionophore A23187 (5 X 10(-6) M)-induced release (% total, means +/- SEM) was: 51.53 +/- 3.05, 50.02 +/- 2.70, 83.91 +/- 4.09, 75.21 +/- 4.51 and 70.59 +/- 6.91 for control, LEV, PI-3, LEV + PI-3 and P. haemolytica groups, respectively. Both virus and bacteria increased HIST content of lung mast cells and enhanced ionophore-induced release. Levamisole significantly reduced spontaneous HIST release in virus-infected calves but had no effect on ionophore-induced release. Results suggest a significant role for HIST in pathogenesis of bovine microbial pneumonia and that LEV probably does not modulate non-immunologic release of HIST from bovine lungs.     

Partial Arytenoidectomy in the Horse with and without Mucosal Closure

Left-sided partial arytenoidectomy was performed in eight horses to evaluate healing. Four horses underwent conventional partial arytenoidectomy with suture apposition of the mucosa. In four horses, most of the arytenoid cartilage, including overlying mucosa, vocal fold, and laryngeal saccule, were excised en bloc without mucosal closure. The horses were monitored clinically by endoscopic examination. One horse from each group was euthanatized at weeks 2, 4, 8, and 16. Complete necropsies with gross and histologic examination of the arytenoidectomy sites were performed. Postoperative complications such as coughing, dysphagia, and aspiration pneumonia were not encountered and problems with wound healing were minimal in both groups. The defect created by partial arytenoidectomy without mucosal closure initially filled to the level of the luminal surface with granulation tissue, with a gradual transition to mature fibrous connective tissue. Grossly, the defect appeared to be healed and was completely epithelialized by week 16 without apparent narrowing of the laryngeal lumen. Partial arytenoidectomy sites with mucosal closure healed in a similar pattern by week 8. Partial dehiscence of the dorsal portion of the sutured mucosa occurred in three horses.     

Accuracy of Arthroscopic Identification of Equine Carpal Lesions

The equine carpal joint was used to evaluate arthroscopic diagnosis of lesions created in joints obtained from horses euthanized for reasons other than lameness. Full-thickness articular defects were made in 13 sites within the antebrachiocarpal joint and middle carpal joint approximating those found in diseased carpal joints. Arthroscopic evaluation of the lesions included location, depth, and size of the defects. The joints were subsequently examined grossly. Results showed that, when compared to gross evaluation, arthroscopy is capable of accurately identifying subtle changes in articular cartilage and bone. A statistically significant increase in error rate was found for lesions at the medial aspect of the proximal radial carpal bone. Other sites with limited arthroscopic access were the proximal ulnar carpal bone, the proximal fourth carpal bone, and the distal intermediate carpal bone. The accuracy of arthroscopic identification of lesions improved significantly during the study as experience with the technique was gained.     

Disturbances in ex vivo vascular smooth muscle responses following exposure to Pasteurella haemolytica vaccines

Weekley, L.B., Eyre, P. Disturbances in ex vivo vascular smooth muscle responses following exposure to Pasturella haemolytica vaccines. J. vet. Pharmacol. Therap. 16 , 446–453.
Rats were vaccinated with saline (control) or one of the two commercially available Pasteurella haemolytica vaccines Presponse or Precon-PH. Animals were killed 3 days later and thoracic aorta removed for evaluation of the ex vivo biophysical responses to carbachol (CCh). In some experiments, vascular endothelium was mechanically removed. Vaccination of rats impairs the endothelial-dependent relaxation to CCh. In vessels with endothelium removed, the contractile response to CCh is converted into a relaxation following vaccination. Treatment of endothelial-denuded vascular rings ex vivo with methylene blue, a guanylate cyclase inhibitor, reduced the vaccination effect. Treatment of vascular rings with the superoxide dismutase inhibitor diethyl-dithiocarbamate, impairs the relaxant reponse of de-endothelialized vessels to CCh in Presponse vaccinated rats while enhancing the relaxation response of vessels from Precon-PH vaccinated rats. De-endothelialized vessels from vaccinated rats, but not control rats, relaxed in the presence of 7V-monomethyl-L-arginine (L-NMMA), a competitive inhibitor of nitric oxide synthetase. Furthermore, in the presence of L-NMMA, the relaxant response to CCh is significantly enhanced by Precon-PH but not Presponse. The normal relaxant response to hydrogen peroxide is converted into a contraction following vaccination. Results suggest that exposure to commercially available P. haemolytica vaccines alters vascular smooth muscle reactivity to CCh and that several independent pathways may be altered.     

A Field Evaluation of Benzimidazole and Nonbenzimidazole Drugs in a Herd of Dairy Goats

A study was conducted to investigate the efficacy of six anthelmintics in a herd of dairy goats. Pretreatment larval cultures indicated that the goats were infected with Haemonchus contortus and Trichostrongylus colubriformis. Three separate treatment regimens were administered. In each trial, mature nonlactating goats were allocated into two treatment groups and a control group. Treatment groups received thiabendazole (TBZ) or levamisole (LEV), mebendazole (MBZ) or fenbendazole (FBZ), and morantel tartrate (MOR) or ivermectin (IVR). LEV, MOR, and IVR reduced fecal strongyle egg counts by 99% to 100% of pretreatment values. The benzimidazole (BZD) drugs changed pretreatment fecal egg counts by +2% to -32%. Results of posttreatment larval culture demonstrated the presence of H contortus larvae following the administration of BZD drugs.