An examination of the potential role of spider digestive proteases as a causative factor in spider bite necrosis.

Tissue necrosis following spider bites is a widespread problem. In the continental United States, the brown recluse (Loxosceles reclusa), hobo spider (Tegenaria agrestis), garden spider (Argiope aurantia) and Chiracanthium species, among others, reportedly cause such lesions. The exact mechanism producing such lesions is controversial. There is evidence for both venom sphingomyelinase and spider digestive collagenases. We have examined the role of spider digestive proteases in spider bite necrosis. The digestive fluid of A. aurantia was assayed for its ability to cleave a variety of connective tissue proteins, including collagen. Having confirmed that the fluid has collagenases, the digestive fluid was injected into the skin of rabbits to observe whether it would cause necrotic lesions. It did not. The data do not support the suggestions that spider digestive collagenases have a primary role in spider bite necrosis.

Effect of a competitive inhibitor of platelet aggregation on experimentally induced laminitis in ponies.

OBJECTIVES: To determining whether inhibition of platelet aggregation prevents development of carbohydrate overload-induced alimentary laminitis. ANIMALS: 22 healthy adult ponies. PROCEDURES: Acute laminitis was induced by oral administration of corn starch/wood flour to 16 ponies, 8 of which were treated with a synthetic analogue of the platelet fibrinogen receptor antagonist peptide (RPR) RGDS (arginine-glycine-aspartic acid-serine) 110885; 6 ponies served as negative controls. Blood was collected before and at 4, 8, 12, 24, 28, and 32 hours after administration of carbohydrate overload, and PCV, total plasma protein concentration, platelet count, activated clotting time, whole blood recalcification time, spontaneous platelet aggregation, ex vivo platelet aggregation responses, in vivo platelet activation, and platelet-neutrophil aggregates were evaluated. RESULTS: Of 16 ponies given carbohydrate, 6 of 8 untreated ponies developed laminitis and 0 of 8 ponies treated with RPR 110885 developed laminitis. The RPR 110885 treatment attenuated the increase in platelet-neutrophil aggregates observed in untreated ponies. CONCLUSIONS: Platelets are involved in the pathogenesis of equine alimentary laminitis. CLINICAL RELEVANCE: Platelet aggregation inhibitors may be useful for prevention or treatment of laminitis, or both.

Hematologic values of the yucatan miniature pig.

Mean values and ranges for 16 hematological parameters for healthy, young, sexually-mature Yucatan miniature swine are presented. No significant differences were observed between sexes with regard to hemograms. Comparison of observed values with those published in the literature for standard domestic and other breeds of miniature swine reveals no major differences.

Evaluation of arginine-glycine-aspartate-containing peptides as inhibitors of equine platelet function.

OBJECTIVES: To determine whether synthetic peptides containing the arginine-glycine-aspartate (RGD) sequence inhibit equine platelet function. ANIMALS: For in vitro studies of blood, 3 healthy Thoroughbreds; for in vivo and ex vivo studies of administration of RGD-containing peptides, 4 young adult pony mares. PROCEDURE: Blood was incubated with and without addition of aspirin or RGD-containing peptides (RGDS, RPR 110885) and platelet aggregation responses and platelet adhesion to subendothelial collagen were determined. RPR 110885 was administered IV, and platelet function was evaluated. Platelet aggregation was determined by a turbidimetric method, and platelet adhesion was evaluated by the Baumgartner perfusion method. RPR 110885 was administered IV at dosages of 30 and 60 micrograms/kg of body weight, and bleeding time, platelet aggregation responses, and platelet count were determined at hourly intervals for 4 hours. RESULTS: Both RGDS and RPR 110885 inhibited platelet aggregation in vitro in dose-dependent manner and inhibited platelet adhesion to subendothelial collagen. The concentration of RGDS that inhibited platelet aggregation by 50% (IC50) was 100 to 142 microM for the various agonists tested, whereas the concentration of RPR 110885 that inhibited platelet aggregation by 50% was 0.03 to 0.05 microM. When administered to ponies at 30 or 60 g/kg, RPR 110885 almost completely inhibited ADP-induced platelet aggregation. CONCLUSIONS: RGDS and RPR 110885 inhibited equine platelet function; however, RPR 110885 was several thousand times more potent than RGDS. CLINICAL RELEVANCE: RGD-containing peptides may be useful for treatment of thrombotic diseases of horses.

Subchronic toxicity studies with the leukotriene D4 antagonist RG 12525.

Preclinical safety studies with the leukotriene D4 antagonist RG 12525 were conducted by the oral route in mice, rats, and monkeys. Oral administration of RG 12525 was repeated daily in studies up to 6 months in duration. RG 12525 was shown to have limited high-dose toxicity after repeated oral administration. The effects of RG 12525 were strongly dependent upon the species considered. High doses of RG 12525 caused significant increases in liver weight in mice, rats, and monkeys that were associated with diffuse hepatocellular hypertrophy in mice and rats but not in monkeys. No related clinical chemistry changes were observed in any of the species and hepatic activities of peroxisomal enzymes or cytochrome P450 were increased only slightly. Proliferation of brown adipose tissue (BAT) was observed in rats and mice but not in monkeys. The BAT reaction was more pronounced in the interscapular area but it was also observed in other subcutaneous locations as well as in mediastinal and bone marrow fat. In all locations, the RG 12525-induced BAT had some morphological similarities with cold-adapted BAT. Repeated administration of RG 12525 at high doses to female rats resulted in a lack of progression to the luteal phase of the estrous cycle that was reversible after discontinuation of treatment. Finally, RG 12525 was nephrotoxic in mice with males being more sensitive than females.

Serum biochemistry of healthy Yucatan miniature pigs.

Sera collected from 24 (12 boars and 12 gilts) healthy, fasted 28-43 week-old Yucatan miniature pigs were analyzed for 21 clinical chemistry parameters. The mean, standard deviation, median, and observed range for each parameter are presented as reference values for the normal blood chemistry for this breed. Comparison with published values reveals that the Yucatan miniature pig has a blood chemistry profile comparable to that of domestic pigs and other breeds of miniature swine.

Giant cell tumor of soft parts in six horses.

Giant cell tumor of soft parts was diagnosed in 6 horses 3 to 12 years old (mean, 6.8 +/- 3.5 years): 3 Quarter Horse geldings, 2 Standardbred mares, and 1 Standardbred stallion. The neoplasms developed as raised, solitary masses, approximately 1 to 4 cm in diameter, which were firmly attached to subcutaneous tissue of the neck (1 horse), shoulder (1 horse), thigh (2 horses), or stifle (2 horses). Excision was followed by local recurrence in 3 horses within 1 to 1 1/2 months. The neoplasms were firm and cut with resistance. On cut surface, they were white, with mottled red hemorrhagic areas.

Acute toxicosis of budgerigars (Melopsittacus undulatus) caused by pyrolysis products from heated polytetrafluoroethylene: clinical study.

Polytetrafluoroethylene (PTFE), a synthetic polymer widely used as a nonstick surface in cookware, releases toxic pyrolysis products when exposed to excessive heat. Thirty-two budgerigars (Melopsittacus undulatus) were exposed to pyrolysis products of either heated PTFE cookware or plain aluminum cookware in a specially designed exposure chamber for given periods. Clinical signs were recorded and necropsies were done on all birds at the termination of each exposure period. The PTFE products caused acute respiratory distress and rapid death in many of the exposed birds. At necropsy, lesions were seen only in the respiratory tract--extensive pulmonary hemorrhage and congestion.

Acute toxicosis of budgerigars (Melopsittacus undulatus) caused by pyrolysis products from heated polytetrafluoroethylene: microscopic study.

An ultrastructural study was performed on the respiratory system of budgerigars (including 6 controls) which were acutely affected by inhalation of toxic fumes from heated polytetrafluoroethylene (PTFE pyrolysis products) or had survived fro 24 hours after a sublethal exposure. The controls were exposed to fumes from heated plan aluminum (ie, not coated with PTFE). The microanatomy of lungs of the controls was described and compared with that of lungs of the birds exposed to PTFE pyrolysates. The PTFE pyrolysates caused extensive, severe necrotizing and hemorrhagic pneumonitis. These lesions were associated with amorphous elongate conglomerates of particles which were similar to those isolated on membrane filters from fumes generated from heated PTFE--this supporting the hypothesis that the toxic principle in PTFE pyrolysates is at least, in part, related to generated particulates.

Injuries of the cervical spine in football.

The neck is a vulnerable area in contact sports in general and in football in particular. The type of injuries encountered often vary with the age and development of the players. Five well-established mechanisms of injury have been identified. Most injuries appear to occur during the act of tackling when the well protected head sustains violent trauma which is transferred directly to the neck. The most dangerous single mechanism is that of flexion, but lateral deviation, extension and impaction also have been identified as mechanisms of injury. The pattern of injuries would suggest that several measures should be undertaken. First, coaches, officials and doctors associated with football teams need to be aware of the dangers of head-on tackling and the value of "heads-up" football to avoid flexion injuries. Deliberately butting players with the head or "spearing" is illegal but head-on tackling and blocking of the so-called "stick-blocking" type is specifically taught at the high school and college levels. In the immature neck this is a dangerous maneuver and should be discouraged. The development of strong neck musculature could reasonably be expected to prevent many neck injuries and isometric and resistance exercises to develop neck strength should be a part of all preseason conditioning. All players who have neck symptoms should be thoroughly evaluated both clinically and radiologically to rule out damage or predisposing structural weakness. This is particularly important in the atlanto-axial area in immature players. Finally, it is recommended that protective collars be worn by all players with a history of neck injury. The authors have gained the impression in surveying a large number of injuries that most serious neck injuries, particularly those involving fracture-dislocation are incurred in the act of open field tackling by defensive players making head-on tackles. Neck flexion is the usual mechanism. A light-weight sponge rubber collar is presently available. It is designed to be used to prevent extension and lateral flexion but it can be easily modified to extend anteriorly where it should aid in preventing the extreme flexion which is responsible for many serious injuries in the young players at the high school level.