OBJECTIVE To evaluate and compare morphological characteristics of the dens in atlantoaxial instability (AAI)-predisposed toy-breed dogs (TBDs) with and without AAI and non–AAI-predisposed healthy Beagles.
ANIMALS 80 AAI-affected and 40 nonaffected TBDs and 40 Beagles.
PROCEDURES Each dog underwent CT examination of the cervical vertebral column. On median 3-D multiplanar reconstruction images, the dens angle (DA) was measured as were the lengths of the dens and the body of the axis; the dens-to-axis length ratio (ratio of the dens length to the axis body length [DALR]) was calculated. Data were compared among dog groups.
RESULTS The DALR in nonaffected TBDs and Beagles did not differ significantly. The mean DALR for AAI-affected TBDs was significantly lower than that for nonaffected TBDs. The mean DA of AAI-affected TBDs was significantly greater than that of Beagles and nonaffected TBDs.
CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that a low DALR might be associated with a high probability of dens abnormalities in TBDs. Additionally, dens length in AAI-affected TBDs appeared to be smaller than that in non–AAI-affected TBDs, given the low DALR in AAI-affected TBDs. Further investigations to determine reference ranges of the DA and DALR and the potential usefulness of those variables as diagnostic markers for AAI in TBDs are warranted.
Objective—To determine whether small intestinal
ischemia and reperfusion affects intestinal intramucosal
pH (pHi), arterial and portal venous blood gas
values, and intestinal blood flow (IBF) and to investigate
relationships between regional intestinal tissue
oxygenation and systemic variables in dogs.
Animals—15 healthy adult Beagles.
Procedure—Occlusion of superior mesenteric artery
(SMA) for 0, 30, or 60 minutes, followed by reperfusion
for 180 minutes, was performed; IBF, pHi, arterial and
portal venous blood gas values, arterial pressure, and
heart rate were measured at various time points; and
intestinal mucosal injury was histologically graded.
Results—Occlusion of the SMA induced significant
decreases in pHi and IBF. After the release of the
occlusion, IBF returned rapidly to baseline values, but
improvement in pHi was slow. Arterial and portal
venous blood gas analyses were less sensitive than
tonometric measurements of pHi, and there was no
correlation between results of blood gas analyses and
tonometric measurements. Histologic score for intestinal
mucosal injury increased significantly, depending
on duration of ischemia, and there was a correlation
between tonometric results and the histologic score.
Conclusion and Clinical Relevance—Results suggest
that it is difficult to accurately evaluate local oxygenation
disorders by monitoring at the systemic
level, whereas clinically pHi is the only reliable indicator
of inadequate regional intestinal tissue oxygenation
in dogs. (Am J Vet Res 2002;63:804–810)
Objective—To evaluate the effects of mitotane administration on the function and morphology of pituitary corticotrophs in clinically normal dogs.
Animals—12 clinically normal adult Beagles.
Procedures—Dogs were randomly assigned to the control group or the mitotane treatment group. In mitotane treatment group dogs, mitotane was administered for 1 month. In both groups, ACTH stimulation testing and corticotrophin-releasing hormone (CRH) stimulation testing were performed. Magnetic resonance imaging (MRI) of the pituitary gland and brain was performed in mitotane treatment group dogs before and after administration of mitotane. After CRH stimulation testing and MRI, dogs were euthanatized and the pituitary gland and adrenal glands were excised for gross and histologic examination.
Results—ACTH concentrations in mitotane treatment group dogs were significantly higher than in the control group dogs following CRH stimulation. Magnetic resonance imaging revealed that pituitary glands were significantly larger in treatment group dogs after administration of mitotane, compared with before administration. On gross and histologic examinations, the adrenal cortex was markedly atrophied. Immunohistochemistry revealed hypertrophy of corticotrophs in pituitary glands of mitotane treatment group dogs.
Conclusions and Clinical Relevance—These findings indicate that inhibition of the adrenal cortex by continuous administration of mitotane leads to functional amplification and morphologic enhancement of corticotrophs in clinically normal dogs. In instances of corticotroph adenoma, hypertrophy of individual corticotrophs induced by mitotane may greatly facilitate enlargement of the pituitary gland and increases in ACTH secretion.
Objective—To determine the effects of intestinal ischemia and reperfusion on the expression of tumor necrosis factor (TNF)-α and interleukin (IL)-6 mRNAs in the jejunum, liver, and lungs of dogs.
Animals—8 healthy adult Beagles.
Procedures—In each dog, the cranial mesenteric artery was occluded for 0 (control group; n = 4) or 60 (I-R group; 4) minutes, followed by reperfusion for 480 minutes; serum TNF-α and IL-6 activities and expression levels of TNF-α and IL-6 mRNAs in jejunal, hepatic, and lung tissues were measured before and at the end of the ischemic period and at intervals during reperfusion. For each variable, values were compared between the control and I-R groups at each time point.
Results—Compared with the control group, serum IL-6 activity increased significantly after 180 minutes of reperfusion in the I-R group; also, jejunal TNF-α mRNA expression increased significantly after 60 (peak) and 180 minutes of reperfusion. In the I-R group, expressions of IL-6 mRNA in the liver and TNF-α and IL-6 mRNAs in the lungs increased significantly at 480 minutes of reperfusion, compared with the control group. Serum TNF-α activity, expression of IL-6 mRNA in the jejunum, and expression of TNF-α mRNA in the liver in the control and I-R groups did not differ.
Conclusions and Clinical Relevance—Results indicated that the liver, lungs, and jejunum contributed to the production of TNF-α and IL-6 after intestinal ischemia and reperfusion in dogs, suggesting that intestinal ischemia and reperfusion induce a systemic proinflammatory cytokine response in dogs.
Objective—To determine whether continuous infusion
of a low dose of lipopolysaccharide (LPS) to
induce a condition mimicking septic shock in dogs
would affect systemic and hepatosplanchnic circulation
Animals—12 healthy adult Beagles.
Procedure—Dogs received a low dose of LPS
(Escherichia coli O55:B5) by continuous IV infusion at
a rate of 1 µg/kg/h for 8 hours. Systemic hemodynamics;
systemic oxygenation; blood flow in the cranial
mesenteric artery, common hepatic artery, and
portal vein; intestinal and hepatic tissue blood flow;
mesenteric oxygenation; and intramucosal PCO2 were
examined before and at selected time points after
onset of the LPS infusion.
Results—After onset of the LPS infusion, cardiac
index increased and mean arterial pressure (MAP)
and systemic vascular resistance decreased, which is
characteristic of the hyperdynamic state in septic
patients. Hepatosplanchnic blood flow increased during
the hyperdynamic state. Intestinal PCO2 was
increased even when blood flows increased. During
the latter half of the experimental period, MAP was
maintained but hepatosplanchnic blood flows
decreased and intestinal PCO2 increased further.
Conclusions and Clinical Relevance—Analysis of
the results suggested that hepatosplanchnic blood
flow enters the hyperdynamic state during the early
stages of sepsis and that intestinal tissue oxygenation
is threatened even when hepatosplanchnic blood
flow is increased or maintained. Hence, improvement
of hepatosplanchnic circulation and intestinal tissue
oxygenation is important in dogs with clinical evidence
of a septic condition. (Am J Vet Res
Objective—To compare activities of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and matrix
metalloproteinase (MMP)-3 and contents of sulfated
glycosaminoglycan (S-GAG) in joint fluid obtained
from dogs with hip dysplasia (HD) and clinically normal
dogs, evaluate correlations among these markers
in joint fluid obtained from dogs with HD, and evaluate
correlations between each marker and clinical and
Animals—26 dogs with HD (clinical group) and 43
clinically normal Beagles (control group).
Procedure—Joint fluid was aseptically collected from
the hip joints of all dogs. For each dog in the clinical
group, age, duration of lameness, radiographic
osteoarthritis (OA) score, and Norberg angle in each
affected joint were recorded. Activities of IL-1β, IL-6,
TNF-α, and MMP-3 and S-GAG contents were measured.
Values were compared between groups by use
of Mann-Whitney U tests, and the Spearman rank correlation
test was used to evaluate correlations among
markers and between each marker and clinical or
Results—Values of all markers were significantly
higher for the clinical group, compared with values for
the control group. There was a moderate positive correlation
between lameness duration and IL-6 activity
and a strong negative correlation between the
Norberg angle and IL-1β activity.
Conclusions and Clinical Relevance—Analysis of
our results indicated that there was a significant
increase in markers of OA in dogs with HD. Activities
of IL-1β and IL-6 in joint fluid of dogs with HD may be
influenced by the severity of laxity in the hip joint and
lameness duration, respectively. (Am J Vet Res
OBJECTIVE To histologically evaluate and compare features of myofibers within the elongated soft palate (ESP) of brachycephalic and mesocephalic dogs with those in the soft palate of healthy dogs and to assess whether denervation or muscular dystrophy is associated with soft palate elongation.
SAMPLE Soft palate specimens from 24 dogs with ESPs (obtained during surgical intervention) and from 14 healthy Beagles (control group).
PROCEDURES All the soft palate specimens underwent histologic examination to assess myofiber atrophy, hypertrophy, hyalinization, and regeneration. The degrees of atrophy and hypertrophy were quantified on the basis of the coefficient of variation and the number of myofibers with hyalinization and regeneration. The specimens also underwent immunohistochemical analysis with anti-neurofilament or anti-dystrophin antibody to confirm the distribution of peripheral nerve branches innervating the palatine myofibers and myofiber dystrophin expression, respectively.
RESULTS Myofiber atrophy, hypertrophy, hyalinization, and regeneration were identified in almost all the ESP specimens. Degrees of atrophy and hypertrophy were significantly greater in the ESP specimens, compared with the control specimens. There were fewer palatine peripheral nerve branches in the ESP specimens than in the control specimens. Almost all the myofibers in the ESP and control specimens were dystrophin positive.
CONCLUSIONS AND CLINICAL RELEVANCE These results suggested that palatine myopathy in dogs may be caused, at least in part, by denervation of the palatine muscles and not by Duchenne- or Becker-type muscular dystrophy. These soft palate changes may contribute to upper airway collapse and the progression of brachycephalic airway obstructive syndrome.
Objective—To evaluate the role of the semitendinosus muscle in stabilization of the canine stifle joint.
Sample—Left stifle joints collected from cadavers of 8 healthy Beagles.
Procedures—Left hind limbs, including the pelvis, were collected. To mimic the tensile force of the quadriceps, gastrocnemius, and semitendinosus muscles, wires were placed under strain between the ends of each muscle. A sensor was used to measure the tensile force in each wire. Specimens were tested in the following sequence: cranial cruciate ligament (CrCL) intact, CrCL transected, released (tensile force of semitendinosus muscle was released in the CrCL-transected stifle joint), and readjusted (tensile force of semitendinosus muscle was reapplied in the CrCL-transected stifle joint). Specimens were loaded at 65.3% of body weight, and tensile force in the wires as well as the cranial tibial displacement were measured.
Results—Tensile force for the CrCL-transected condition increased significantly, compared with that for the CrCL-intact condition. Mean ± SD cranial tibial displacement for the CrCL-transected condition was 2.1 ± 1.3 mm, which increased to 7.2 ± 2.3 mm after release of the tensile force in the semitendinosus muscle.
Conclusions and Clinical Relevance—Results supported the contention that the semitendinosus muscle is an agonist of the CrCL in the stifle joint of dogs. Moreover, the quadriceps and gastrocnemius muscles may be antagonists of the CrCL. These findings suggested that the risk of CrCL rupture may be increased by diseases (such as cauda equina syndrome) associated with a decrease in activity of the semitendinosus muscle.
Objective—To determine whether small intestinal
ischemia and reperfusion induces bacterial translocation
and proinflammatory cytokine response in either
the systemic or portal circulation in dogs.
Animals—17 healthy adult Beagles.
Procedure—The superior mesenteric artery (SMA)
was occluded for 0 (group-3 dogs), 30 (group-1 dogs),
or 60 (group-2 dogs) minutes, followed by reperfusion
for 180 minutes; serum lactate and endotoxin concentrations
and tumor necrosis factor-α (TNF-α), interleukin-
1β (IL-1β), and IL-6 activities in the systemic and
portal circulation and intramucosal pH were measured
at various time points.
Results—In group-2 dogs, TNF-α activity was found
to be significantly increased in the portal circulation,
peaking at 60 minutes of reperfusion; TNF-α activity,
in the systemic circulation, gradually increased from
60 minutes of reperfusion to the end of the experiment;
however, the increase was not significant. In
group-1 and -2 dogs, IL-6 activities significantly and
gradually increased in the systemic and portal circulation
during the reperfusion phase, and the magnitude
of these increases was dependent on the duration of
the ischemic phase. There were no significant
changes in IL-1β activity or endotoxin concentration in
any dog group.
Conclusions and Clinical Relevance—Results of the
our study indicate that intestinal ischemia and reperfusion
leads to significant increases of the circulating
TNF-α and IL-6 activities, depending on the duration of
the ischemia phase, in the absence of detectable
endotoxin in the circulation. This finding suggests that
intestinal ischemia and reperfusion induces a systemic
proinflammatory cytokine response in dogs.
(Am J Vet Res 2002;63:1680–1686)
Objective—To identify characteristics of chondrodystrophoid and nonchondrodystrophoid small-breed dogs with cervical intervertebral disk herniation (IVDH).
Design—Retrospective case series.
Animals—187 small-breed (≤ 15 kg [33 lb]) dogs that underwent surgery because of cervical IVDH.
Procedures—Medical records were reviewed for information on breed, sex, age, weight, location of affected intervertebral disks, duration and severity of neurologic signs, and recovery time.
Results—55 of the 187 (29.4%) dogs were Beagles. The most frequently affected intervertebral disk was C2–3 (81/253 [32.0%]), and this was the more frequently affected intervertebral disk in dogs of several chondrodystrophoid breeds, including Beagles (29/66 [43.9%]), Dachshunds (13/37 [35.1%]), Shih Tzus (16/41 [39.0%]), and Pekingese (3/10 [30.0%]). However, caudal disks (C5–6 or C6–7) were more frequently affected in Yorkshire Terriers (13/24 [54.2%]) and Chihuahuas (9/13 [69%]). Shih Tzus and Yorkshire Terriers were significantly older at the time of surgery (mean ± SD age, 9.6 ± 2.3 years and 9.5 ± 2.5 years, respectively) than were Pomeranians (6.2 ± 2.3 years), and Yorkshire Terriers had a significantly higher number of affected disks (2.0 ± 0.9) than did Dachshunds (1.1 ± 0.3). Mean recovery time was significantly longer in Yorkshire Terriers (36.7 ± 13.0 days) than in Beagles (16.5 ± 17.1 days), Shih Tzus (17.8 ± 14.5 days), or Chihuahuas (12.2 ± 7. 2 days).
Conclusions and Clinical Relevance—Results suggested that there may be breed-specific differences in the characteristics of cervical IVDH in small-breed dogs.