Health effects following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards.

Permanent approval of shot composed of tungsten-iron and tungsten-polymer for waterfowl hunting by the U.S. Fish and Wildlife Service was pending the results of the present study that examined the health and reproductive effects of the two shot types on mallards (Anas platyrhynchos) over a 150-day period. We collected data pertaining to the effects of tungsten-iron and tungsten-polymer shot on mortality, body weight, organ weight, tissue pathology, and shot erosion. Thirty-two bird groups (sexes equal) of adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150-day trial (26 January 1998 to 25 June 1998). An additional 12 mallards (sexes equal) were dosed orally with eight #4 lead shot (positive control) on day 0 of the study. All lead-dosed ducks died by day 25, whereas no ducks died in the other treatment groups. Significant liver hemosiderosis was present in all control and tungsten-iron-dosed males, in five of eight control and three of eight tungsten-iron-dosed females, and in one tungsten-polymer-dosed male examined. The rate of shot erosion was highest for tungsten-polymer shot (99%), followed by tungsten-iron (72%), and steel (55%) shot. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards did not have deleterious health effects during the 150-day trial based on mortality, body weights, organ weights, and histology of the liver and kidneys.

Evaluation of a free vascularized medial tibial bone graft in dogs.

OBJECTIVE: To develop a free vascularized tibial bone graft based on the periosteal saphenous blood supply. STUDY DESIGN: Preliminary anatomic study of medial tibial blood supply. In vivo comparison of a vascularized and avascular tibial bone graft. ANIMALS: Nine canine cadavers; 14 healthy adult dogs that weighed 25 to 32 kg. METHODS: An anatomic study of the vascular supply of the medial aspect of the tibia was performed using the Spalteholz technique. A bone graft consisting of the medial aspect of the tibia was transferred to a mandibular defect as a vascularized graft in 7 dogs and as an avascular graft in 7 dogs. Bone scans were performed to evaluate graft perfusion. Radiographic evaluation of the mandibles and tibias was performed. The dogs were killed after 60 days, five mandibles from each group were examined histologically, and two from each group were evaluated using the Spalteholz technique. RESULTS: The saphenous vascular pedicle provides vascular perfusion to the medial tibial cortex. Bone scans and radiographic evaluations were consistent with viable bone in the vascularized grafts, and nonviable bone in the avascular grafts. Histological examination revealed live, healing bone in vascular grafts and necrotic bone in avascular grafts. Spalteholz evaluation revealed many small arborizing vessels in the vascular grafts and no organized vasculature in the avascular grafts. CONCLUSIONS: The vascularized medial tibial cortical bone graft survived and proceeded to bony union in the mandibular body defect more readily than the avascular graft in this experimental model. CLINICAL RELEVANCE: A vascularized medial tibial bone graft is a suitable free graft for use in reconstructing bone defects in dogs.

Prevention of irradiation-induced esophagitis by plasmid/liposome delivery of the human manganese superoxide dismutase transgene.

Esophagitis is a major toxicity of radiation therapy for nonsmall-cell lung cancer. Intraesophageal injection of manganese superoxide dismutase (MnSOD) plasmid/liposome complexes (1 mg of the pRK5-MnSOD plasmid containing the human MnSOD transgene in a 0.15 ml volume of lipofectin) before irradiation was carried out to attempt to prevent irradiation esophagitis. In control noninjected male C3H/HeNsd mice, esophagitis was induced by single fraction 3,500 cGy irradiation. Histopathology at 4 days revealed vacuole formation in squamous lining cells, separation of the squamous layer from the underlying muscle layer, ulceration at 7 days, and dehydration and death by 30 days. MnSOD plasmid/liposome complex-injected mice showed transcription of the human MnSOD transgene message in esophageal squamous lining cells by nested reverse transcriptase-polymerase chain reaction (RT-PCR) increased MnSOD biochemical activity 24 h after injection, decreased vacuole formation at day 4 (P < 0.001) after 3,500 cGy thoracic irradiation, and improved survival (P = 0.0009). In contrast, groups of mice receiving LacZ (bacterial beta-galactosidase gene) plasmid/liposome complexes or liposomes containing no DNA before 3,500 cGy irradiation showed an unaltered irradiation histopathology and decreased survival. Mice receiving intraesophageal MnSOD plasmid/liposomes followed 8 h later by human equivalent doses of Taxol (1.4 mg/kg) and carboplatin (2.5 mg/kg), then 15 h later 3,300 cGy irradiation, showed increased survival, compared with irradiated control or LacZ plasmid/liposome groups. Thus, overexpression of the human MnSOD transgene in the esophagus can prevent irradiation-induced esophagitis in the mouse model.

Acute effects of lead, steel, tungsten-iron, and tungsten-polymer shot administered to game-farm mallards.

Sixteen-bird groups (sexes equal) of adult mallards (Anas platyrhynchos) were orally dosed with eight #4 steel short, eight #4 lead shot, eight BB-size tungsten-iron shot, eight BB-size tungsten-polymer shot, or were sham-dosed and maintained for 30 days (16 January 1996 to 15 February 1996). Half of the lead-dosed ducks (five males, three females) died during the study, whereas no ducks died in the other dosage groups. For lead-dosed ducks, hematocrit and hemoglobin concentration were decreased on day 15 of the trial, but not on day 30. Delta aminolevulinic acid dehydratase activity in lead-dosed ducks was lower when compared to steel-dosed ducks only. Plasma activities of selected enzymes were elevated in lead-dosed ducks when compared to enzyme activities of ducks in the other groups. For lead-dosed ducks, relative heart, liver, and kidney weights increased in comparison to relative weights of those organs of ducks in other groups. Histology of tissues indicated that renal nephrosis accompanied by biliary stasis was present in the eight lead-dosed ducks that died. For the eight lead-dosed ducks that survived, six had mild to severe biliary stasis. Mild biliary stasis was noted in five tungsten-iron dosed ducks and three tungsten-polymer dosed ducks. Amounts of lead in the femur, liver, and kidneys were higher in lead-dosed ducks than in ducks of the other four groups. Small amounts of tungsten were detected in the femur and kidneys of two tungsten-polymer dosed ducks. Higher concentrations of tungsten were detected in the femur, liver, and kidneys of all tungsten-iron dosed ducks. The rate of shot erosion was highest (80%) for the tungsten-polymer shot, followed by tungsten-iron (55%), lead (50%), and steel shot (33%). Results indicated that tungsten-iron or tungsten-polymer shot (8 shot/duck) orally administered to mallards did not adversely affect them during a 30-day trial.

Clinical relevance of the microvasculature of the equine proximal sesamoid bone.

The blood supply to the proximal sesamoid bone of the equine forelimb was examined in 18 cadaver limbs from adult horses, using x-ray computed tomography and a tissue-clearing (Spalteholz) technique. Results of the study indicated that the proximal sesamoid bones were supplied by multiple branches of the medial and lateral palmar digital arteries, which entered the proximal half of the bones on their non-articular, abaxial surface. After entering the bone, the vessels traverse dorsally, axially, and distally, arborizing into several smaller branches that appear to supply the entire bone. The major branches of these vessels reside in bony canals, the orientation and distribution of which parallel the radiographic lucencies seen in horses with sesamoiditis and correspond to the configuration of apical fracture patterns.

Changes in renal function associated with treatment of hyperthyroidism in cats.

We measured glomerular filtration rate (GFR) estimated by plasma disappearance of 99mTc-labeled diethylenetriaminepentaacetic acid, serum concentrations of thyroxine (T4), creatinine, and urea nitrogen, and urine specific gravity in 13 cats with naturally acquired hyperthyroidism before and 30 days after treatment by bilateral thyroidectomy, and in a group of 11 control cats. Mean (+/- SD) serum T4 concentration decreased from a pretreatment value of 120.46 (+/- 39.21) nmol/L to a posttreatment value of 12.15 (+/- 6.26) nmol/L (P < 0.0001; reference range, 10 to 48 nmol/L). Treatment of hyperthyroidism resulted in a decrease in mean (+/- SD) glomerular filtration rate, from 2.51 (+/- 0.69) ml/kg of body weight/min to a posttreatment value of 1.40 (+/- 0.41) ml/kg/min (P < 0.0001). Mean serum creatinine concentration increased from 1.26 (+/- 0.34) mg/dl to 2.05 (+/- 0.60) mg/dl (P < 0.01). Mean serum urea nitrogen concentration increased from 26.62 (+/- 6.83) mg/dl to a mean postthyroidectomy concentration of 34.92 (+/- 8.95) mg/dl (P < 0.01). All changes were significant. Two cats developed overt renal azotemia after treatment of hyperthyroidism. Our results provide further evidence that treatment of hyperthyroidism can result in impaired renal function. In addition, our results suggest that, in some instances, thyrotoxicosis might mask underlying chronic renal insufficiency.

Principles and concepts of computed tomography.

The final CT image is actually made of a grid of tiny squares called pixels. The scale of grays assigned to each pixel represents the attenuation of x-rays by the structures in the tomographic slice. Manipulation of the gray scale allows optimal visualization of all the tissues within the slice. This control over the gray scale and the absence of structure superimposition are the advantages of CT over conventional x-ray techniques. The steps used to acquire the final CT image are collection of data from the patient (recording of transmitted x-ray intensities from many angles), computer processing of data (mathematical calculation of attenuation of each structure in the tomographic slice), image display (assigning of appropriate gray scale to CT image to evaluate all structures), and data storage (recording series of tomographic images on x-ray film and archiving image data for later review). Common image artifacts that must be identified and interpreted as such include aliasing, ring artifacts, beam hardening effect, metal, motion, partial volume averaging, and streaking from out-of-field objects.

Interpretation of computed tomographic images.

This article discusses the production of optimal CT images in small animal patients as well as principles of radiographic interpretation. Technical factors affecting image quality and aiding image interpretation are included. Specific considerations for scanning various anatomic areas are given, including indications and potential pitfalls. Principles of radiographic interpretation are discussed. Selected patient images are illustrated.

Repair of a proximal metatarsal Salter type-II fracture in a foal.

Bilateral radiographically persistent proximal third metatarsal physes and concurrent cuboidal bone immaturity were identified in a foal. Repair of a Salter type-II fracture of the left proximal third metatarsal physis was accomplished by use of lag screw fixation. A 6-day-old Arabian foal, intended for use as a show horse, was referred because of severe unilateral hind limb lameness and valgus deformity. A Salter type-II fracture of the proximal portion of the third metacarpal bone was identified radiographically and repaired by use of cancellous lag screws. The fractured limb was further supported with a modified Robert Jones bandage and fiberglass tube cast. Eight weeks after surgery, the colt was sound at a trot and had minimal valgus deformity. At this time, radiography revealed healing of the fracture and implants were removed. Six months after fracture repair, the outcome was considered successful on the basis of a desirable cosmetic result and no detectable lameness at a trot. The proximal third metatarsal physis is generally not radiographically visible in the neonate. This report describes the identification and successful repair of a fracture involving this persistent physis. Other sites of skeletal immaturity were also identified, and should be considered in the evaluation and management of unusual physeal fractures.

Radiographic evaluation of esophageal function in Chinese Shar Pei pups.

Liquid barium esophagography was done in 29 clinically normal Chinese Shar Pei pups and observed fluoroscopically, beginning when they were approximately 3 months old and repeated periodically until they were at least 18 months old, if possible. Of these dogs, 69% had relatively slow stimulation of secondary waves, 48% had generalized poor esophageal tone or motility, and 38% had esophageal redundancy. Sequential studies revealed apparent improvement with age for those dogs initially showing slow motility, provided that redundancy was not also present. Another group of 9 Chinese Shar Pei pups had histories of either regurgitation or vomiting. Five of these had hiatal hernia and 2 had megaesophagus.