Objective—To measure the effect of induced myopia on field trial performance in dogs.
Animals—7 Labrador Retrievers and 1 Chesapeake Bay Retriever trained in field trial competition.
Procedures—Dogs were commanded to retrieve targets at 137.2 m (150 yards). Each dog participated in 3 trials while their eyes were fitted with 0- (plano), +1.50-, or +3.00-diopter (D) contact lenses, applied in random order. Retrieval times were measured objectively, and dog performances were evaluated subjectively by masked judges.
Results—Retrieval times were significantly faster with plano lenses than with +1.50- or +3.00-D lenses, but there were no significant differences in times between +1.50- and +3.00-D lenses. Masked judges assigned the best performance scores to dogs with plano lenses and the lowest scores to dogs fitted with +3.00-D lenses.
Conclusions and Clinical Relevance—Even mild myopic defocusing had a significant negative impact on both the subjective and objective assessments of dogs' performances. Dogs with demanding visual tasks or signs of visual deterioration should be evaluated retinoscopically to determine the refractive state because they may have ametropia.
Objective—To determine the effects of body position on lung and air-sac volumes in anesthetized and spontaneously breathing red-tailed hawks (Buteo jamaicensis).
Animals—6 adult red-tailed hawks (sex unknown).
Procedures—A crossover study design was used for quantitative estimation of lung and air-sac volumes in anesthetized hawks in 3 body positions: dorsal, right lateral, and sternal recumbency. Lung volume, lung density, and air-sac volume were calculated from helical computed tomographic (CT) images by use of software designed for volumetric analysis of CT data. Effects of body position were compared by use of repeated-measures ANOVA and a paired Student t test.
Results—Results for all pairs of body positions were significantly different from each other. Mean ± SD lung density was lowest when hawks were in sternal recumbency (–677 ± 28 CT units), followed by right lateral (–647 ± 23 CT units) and dorsal (–630 ± 19 CT units) recumbency. Mean lung volume was largest in sternal recumbency (28.6 ± 1.5 mL), followed by right lateral (27.6 ± 1.7 mL) and dorsal (27.0 ± 1.5 mL) recumbency. Mean partial air-sac volume was largest in sternal recumbency (27.0 ± 19.3 mL), followed by right lateral (21.9 ± 16.1 mL) and dorsal (19.3 ± 16.9 mL) recumbency.
Conclusions and Clinical Relevance—In anesthetized red-tailed hawks, positioning in sternal recumbency resulted in the greatest lung and air-sac volumes and lowest lung density, compared with positioning in right lateral and dorsal recumbency. Additional studies are necessary to determine the physiologic effects of body position on the avian respiratory system.
Objective—To determine the prevalence of activating
internal tandem duplications (ITDs) in exons 11 and 12
of c-kit in mast cell tumors (MCTs) of dogs and to correlate
these mutations with prognosis.
Sample Population—157 formalin-fixed, paraffinembedded
MCTs from dogs in the pathology database
of the Veterinary Medical Teaching Hospital at
the University of California, Davis.
Procedure—Genomic DNA was isolated from tumor
specimens and a polymerase chain reaction procedure
was performed to determine whether there
were ITDs in exons 11 and 12.
Results—We identified ITDs in 1 of 12 (8%) grade-I,
42 of 119 (35%) grade-II, and 9 of 26 (35%) grade-III
tumors (overall prevalence, 52 of 157 [33%]). Logistic
regression analysis revealed that the odds of grade-II
and -III tumors possessing an ITD were approximately
5 times greater than that for grade-I tumors,
although these odds did not differ significantly.
Although MCTs possessing an ITD were twice as likely
to recur after excision and twice as likely to result
in metastasis as those without an ITD, these values
also did not differ significantly.
Conclusions and Clinical Relevance—These results
provide evidence that ITDs in c-kit occur frequently in
MCTs of dogs. The high prevalence of c-kit activating
mutations in MCTs of dogs combined with the relative
abundance of mast cell disease in dogs provide
an ideal naturally developing tumor in which to test
the safety and efficacy of novel small-molecule kinase
inhibitors such as imatinib mesylate. (Am J Vet Res
Objective—To develop a model for measuring rotary
stability of the canine elbow joint and to evaluate the
relative contribution of the anconeal process (AN), lateral
collateral ligament (LCL), and medial collateral ligament
Sample Population—18 forelimbs from 12 canine
Procedure—Forelimbs were allocated to 3 experimental
groups (6 forelimbs/group). Each intact forelimb
was placed in extension at an angle of 135° and
cycled 50 times from –16° (pronation) to +28° (supination)
in a continuous manner at 2.0 Hz. Cycling was
repeated following sectioning of the structure of interest
(group 1, AN; group 2, LCL; and group 3, MCL).
Torque at –12° (pronation) and +18° (supination) was
measured for each intact and experimentally sectioned
limb. A Student t test was performed to compare
torque values obtained from intact verses experimentally
sectioned limbs and for comparison with
established criteria for differentiation of primary
(≥ 33%), secondary (10 to 33%), and tertiary rotational
stabilizers (< 10%).
Results—In pronation, the AN was the only primary
stabilizer (65%). For supination, the LCL was a primary
stabilizer (48%), AN was a secondary stabilizer
(24%), and MCL was a tertiary stabilizer (7%).
Conclusions and Clinical Relevance—With the
elbow joint in extension at an angle of 135°, the AN is
a primary rotational stabilizer in pronation, and the
LCL is a primary stabilizer in supination. Disruption of
the AN or LCL may affect rotary range of motion or
compromise stability of the elbow joint in dogs.
(Am J Vet Res 2002;63:1520–1526)
Objective—To characterize the effect of maintenance
hemodialysis on plasma amino acid concentrations
and to quantitate free amino acid losses into the
dialysate during hemodialysis in healthy dogs.
Animals—8 healthy adult dogs.
Procedure—Five dogs received hemodialysis treatments
3 times per week for 4 weeks. Plasma amino
acid concentrations were evaluated once per week
for 4 weeks in each of the 5 dogs prior to hemodialysis
(time 0), 90 minutes during hemodialysis, and
immediately after hemodialysis (180 minutes). Total
free amino acid concentrations and plasma amino
acid concentrations (time 0, 90 minutes, and 180 minutes)
in the dialysate were evaluated in 3 dogs that
received 1 hemodialysis treatment.
Results—Significant time versus week interactions
with any plasma amino acid were not detected; however,
significant decreases in all plasma amino acid
concentrations measured were detected at the midpoint
of dialysis (46 ± 2%) and at the end of each dialysis
session (38 ± 2%). Mean (± SEM) total free
amino acid loss into the dialysate was 2.7 ± 0.2 g or
0.12 g/kg of body weight.
Conclusions and Clinical Relevance—Hemodialysis
is associated with significant alterations in plasma
amino acid concentrations and loss of free amino
acids into the dialysate. Loss of amino acids into the
dialysate, coupled with protein calorie malnutrition in
uremic patients, may contribute to depletion of amino
acid stores.(Am J Vet Res 2000;61:869–873)
Objective—To compare efficacy and safety of meso-
2,3-dimercaptosuccinic acid (DMSA) and Ca EDTA for
treatment of experimentally induced lead toxicosis in
cockatiels ( Nymphicus hollandicus).
Animals—137 (69 females, 68 males) healthy cockatiels
between 6 months and 8 years old.
Procedure—Lead toxicosis was induced by placing
lead shot in the gastrointestinal tract. Treatment with
Ca EDTA (40 mg/kg of body weight, IM, q 12 h), DMSA
(40 or 80 mg/kg, PO, q 12 h), and sodium sulfate salts
(SSS; 0.5 mg/kg, PO, q 48 h) was initiated 4 days after
induction of lead toxicosis. Blood lead concentrations
were determined, using atomic absorption spectrophotometry.
Number of birds surviving and blood
lead concentrations were compared among groups.
Results—In Phase II of the study, administration of
DMSA and Ca EDTA significantly decreased blood
lead concentrations when used alone or in combination
in birds with lead toxicosis. Addition of SSS did
not result in further decreases in lead concentrations.
Eight of 12 (66.7%) birds without lead toxicosis given
80 mg of DMSA/kg did not survive to the end of the
study . Lesions related to treatment with chelating
agents were not detected during necropsy.
Conclusions and Clinical Relevance—DMSA and
Ca EDTA are effective chelating agents in cockatiels.
Because DMSA is administered orally, it may be easier
than other chelating agents for bird owners to
administer at home. However, the narrow margin of
safety of DMSA indicates that this agent should be
used with caution. (Am J Vet Res 2000;61:935–940)
Objective—To determine effects of incremental radial
shortening and subsequent ulnar ostectomies on joint
surface contact patterns in a canine elbow joint model.
Sample Population—Paired forelimbs from 9 adult
Procedure—Joint casting was performed by placement
of colored polymethylmethacrylate in the elbow
joint cavity and loading in a materials testing system
at physiologic angle and load. Joint casting was performed
in unaltered specimens, after radial shortening,
and after subsequent distal ulnar ostectomy,
proximal ulnar ostectomy, and proximal ulnar ostectomy
with intramedullary pinning. Computer-aided
analysis of photographs of proximal radial and ulnar
articular surfaces without joint casts was performed
before and after each casting procedure.
Results—All increments of radial shortening changed
the size and location of radial and ulnar contact areas.
The radial contact area became smaller, the anconeal
contact area disappeared, the medial coronoid contact
area migrated craniolaterally, and the lateral projection
of the coronoid process became a contact area. A proximal
ulnar ostectomy stabilized with an intramedullary
pin restored normal contact area size and location and
restored continuity of the radial and coronoid contact
areas across the radioulnar articulation in 6 of 10 specimens.
A midshaft ulnar ostectomy, distal to the level of
the radioulnar ligament, had no effect on contact patterns.
A proximal ulnar ostectomy without stabilization
resulted in varus deformity during loading.
Conclusion and Clinical Relevance—Proximal radial
shortening, which creates articular step incongruity,
changes the location and size of the radioulnar contact
areas. Dynamically stabilized ulnar ostectomies
proximal to the radioulnar ligament restore contact
patterns in vitro . (Am J Vet Res 2001;62:1548–1556)
Objective—To compare in vitro mechanical properties
of toggle pins and toggle rods used as suture
anchors and of 3 suture materials (50-lb monofilament
polybutester, No. 5 braided polyester, and 5-mm
woven polyester) commonly used as prosthetic ligaments
in the repair of hip joint luxation in dogs.
Sample Population—Femoropelvic specimens from
the cadavers of 18 dogs.
Procedure—Suture anchors were compared by use
of pullout tests. Suture materials were compared by
use of monotonic and cyclic tensile tests; cyclic tensile
tests were performed with the suture placed over
the edge of an aluminum bar to simulate the edge of
the femoral bone tunnel. In vitro mechanical properties
of the ligament of the femoral head were determined
by use of monotonic tensile tests, using boneligament-bone cadaveric specimens. The in vitro
mechanical properties of the acetabulum-ligamentfemur
complex and of this complex following rupture
of the ligament and stabilization with a toggle rod and
5-mm woven polyester were determined by use of
compression tests that simulated weight-bearing.
Results—Mechanical properties of the toggle rod
were not significantly different from those of the toggle
pin. Woven polyester had the longest fatigue life
in cyclic testing. Hip joints stabilized with a toggle rod
and woven polyester had less than half the strength
in vitro of intact joints.
Conclusions and Clinical Relevance—Results suggested
that a toggle rod or toggle pin can be used for
stabilization of hip joint luxations in dogs. Of the
materials tested, braided polyester had the best in
vitro mechanical properties. (Am J Vet Res 2001;62:
Objective—To assess the use of a caudal external
thoracic artery axial pattern flap to treat sternal cutaneous
wounds in birds.
Animals—16 adult Japanese quail.
Procedure—A cutaneous defect in the region of the
mid-sternum was surgically created in all quail. In 6
quail (group I), an axial pattern flap was created from
the skin of the lateral aspect of the thorax and
advanced over the sternal defect. In 8 quail (group II),
a flap was similarly created and advanced but the flap
vasculature was ligated. All quail were euthanatized at
14 days after surgery and had necropsies performed.
Sections of the flap and the surrounding tissue were
examined histologically to assess flap viability.
Results—All axial pattern flaps in group-I quail had
100% survival. In group II, mean percentage area of
flap survival was 62.5%; mean area of necrosis and
dermal fibrosis of flaps were significantly greater than
that detected in group I. In flaps of group-II quail, neovascularization
in the deep dermis and profound
necrosis of the vascular plexus in the superficial dermis
Conclusions and Clinical Relevance—Results indicated
that the caudal external thoracic artery axial pattern
flap could be used successfully in the treatment
of surgically created sternal cutaneous defects in
quail with no signs of tissue necrosis or adverse
effects overall. Use of this technique to treat selfmutilation
syndromes or application after surgical
debulking of tumors or other masses might be beneficial
in many avian species. (Am J Vet Res
Procedure—Joint casting was performed by placement
of colored polymethylmethacrylate in the elbow
joint cavity followed by loading in a materials testing
system at physiologic angle and load. Joint casting
was performed in unaltered specimens, after 10°
medial opening wedge osteotomy, and after lateral
sliding osteotomy of the proximal portion of the
humerus. Computer-aided analysis of photographs of
proximal radial and ulnar articular surfaces after each
casting procedure was performed.
Results—The lateral sliding humeral osteotomy and
10° medial opening wedge osteotomy significantly
altered joint surface contact regions of the canine
elbow joint. Osteotomies resulted in a reduction in
the size of the radial, ulnar, and combined radioulnar
contact areas. Both osteotomies also resulted in craniolateral
migration of the radial contact area and craniomedial
recession of the ulnar contact area. Although
the reduction in ulnar contact area with these treatments
is consistent with our hypotheses, the reduction
in radial contact area was not anticipated.
Conclusions and Clinical Relevance—Humeral
osteotomies alter joint surface contact areas of the
canine elbow joint in vitro. Humeral osteotomies may
decrease contact areas on the diseased region of the
joint in dogs with elbow dysplasia; however, the overall
decrease in joint surface contact area suggests
that these procedures may induce focal increases in
pressure that may cause iatrogenic cartilage damage
when applied in vivo. (Am J Vet Res 2003;64:506–511)