Genetic and immunological complexity of major histocompatibility regions

There are genetic differences within the major histocompatibility complex of the mouse which lead to skin graft rejection but which cannot be detected serologically. When confronted with these differences on allogeneic cells, lymphocytes proliferate in vitro. In other cases, in vitro lymphocyte proliferation but no skin graft rejection is associated with loci that are linked to but genetically separable from the loci controlling the serologically defined antigens.     

Lightning injury in an outdoor swine herd.

Three pigs, weighing 63 kg-70 kg each, from a group of 8 pigs in an outdoor pen that was struck by lightning were necropsied. All 3 pigs presented with hind limb paralysis. The only lesions identified were multiple fractures of the last (seventh) lumbar vertebral body and first sacral vertebral segment, with dorsal displacement of the sacrum and transection of the distal spinal cord and spinal nerves. Hemorrhages extended from the fracture sites into muscles immediately surrounding the lumbosacral junction and retroperitoneally into the pelvic cavity. These hemorrhages were not clearly visible until the pelvic region was dissected. Lesions commonly found in human lightning-strike victims were not present in these pigs. Because vertebral fractures may be the only lesions and may be grossly subtle in heavily muscled pigs, careful pelvic and vertebral dissection is recommended in cases of suspected lightning strike and electrocution.     

EFFECTS OF LOW-LEVEL EXPOSURE TO IONIZING RADIATION: CURRENT CONCEPTS AND CONCERNS FOR VETERINARY WORKERS*

The issue of biological effects caused by low-level exposure to ionizing radiation (0.1Sv/yr or 10 rem) is a concern of veterinary radiologists, clinicians and radiotherapists. Cellular damge from ionizing radiation is mediated by injury to DNA, some of which can be repaired. The most important harmful effects attributed to low-level exposure are carcinogenesis and mutation. Ionizing radiation may also cause embryonic and fetal damage, life span shortening and cataractogenesis. The estimated excess risk of mortality for all human cancers is 0.8% (800 deaths per 100,000) per 0.10 Sv of acute exposure; at low dose-rates, risk is presumed to be less. Ionizing radiation increases the frequencey of spontaneous genic and chromosomal mutations in man and animals. Studies of atomic bomb survivors imply that at least 1 Sv would be needed to double the spontaneous mutation rate for acute exposure to low-LET radiation. However, the doubling dose for chronic, low-level exposure may be 4 Sv or more. The human embryo and fetus are sensitive to excessive doses of ionizing radiation, with mental retardation the main concern in the low dose range. Paradoxically, there is scientific evidence that in some instances, chronic low-level exposure to ionizing radiation causes a beneficial or hormonic effect. For veterinary workers, occupational exposures appear to be well below the maximum permissible dose limit and the risk or probability of harmful effects is low if stringent radiation safety practices are maintained.     

Association of increased tracheal mucus accumulation with poor willingness to perform in show-jumpers and dressage horses

The objective of this study was to examine the association of pharyngeal lymphoid hyperplasia (PLH), recurrent laryngeal neuropathy (RLN), mucus accumulation (MA) score and tracheobronchial secretion neutrophil percentage (TBS-N) with rider-assessed performance in sport horses. Airway endoscopy scores, tracheobronchial secretion cytology, rider-assessed general impression and willingness to perform were investigated in 171 top-level sport horses. Increased MA appears to be associated with poor willingness to perform in sport horses. Older horses had decreased PLH scores and increased TBS-N. Mucus accumulation scores > or =3 were associated with increased odds (mean 9.92; upper and lower 95% confidence intervals: 1.5-64.6) of poor rather than excellent willingness to perform. A TBS-N of 20-50% compared with <20% was associated with decreased odds (median 0.11; upper and lower 95% CI: 0.02-0.66) of poor rather than excellent willingness to perform. In addition, horses with an RLN grade > or =2 had significantly higher odds for giving a poorer general impression and willingness to perform. This finding, however, must be interpreted with caution, since only two horses had significant RLN (grade > or =3).     

Carboplatin and piroxicam therapy in 31 dogs with transitional cell carcinoma of the urinary bladder

Invasive transitional cell carcinoma (TCC) of the urinary bladder responds poorly to medical therapy. Combining platinum chemotherapy with a cyclooxygenase (cox) inhibitor has shown promise against canine TCC, where the disease closely mimics the human condition. A phase II clinical trial of carboplatin combined with the cox inhibitor, piroxicam, was performed in 31 dogs with naturally occurring, histopathologically confirmed, measurable TCC. Complete tumour staging was performed before and at 6‐week intervals during therapy. Tumour responses in 29 dogs included 11 partial remissions, 13 stable disease and five progressive disease. Two of the 31 dogs were withdrawn prior to the re‐staging of the tumour. Gastrointestinal toxicity was observed in 23 dogs. Hematologic toxicity was noted in 11 dogs. The median survival was 161 days from first carboplatin treatment to death. In conclusion, carboplatin/piroxicam induced remission in 40% of dogs providing evidence that a cox inhibitor enhances the antitumour activity of carboplatin. The frequent toxicity and limited survival, however, do not support the use of this specific protocol against TCC.     

ARTIFACTS AND TECHNICAL ERRORS PRESENTED AS PART OF THE 1996 ACVR ORAL CERTIFICATION EXAMINATION

Cases used for the examination consisted of various imaging artifacts and technical errors. The candidate was expected to name or identify the problem and discuss its cause and prevention. For the purpose of completeness, the scope and detail given here is in excess of that needed to pass the examination. Unless the problem was obvious, the examiner pointed out the problem to be discussed.