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Objective—To determine the dimensions and volume of thyroid tissue in clinically normal cats by use of computed tomography.
Procedure—Helical computed tomography images (2-mm collimation) were acquired from the cranial aspect of the second cervical vertebra through the caudal aspect of the fourth cervical vertebra. Data were acquired before contrast medium administration (n = 7 cats) and immediately after contrast medium enhancement (1 cat). Length, width, and height measurements of each thyroid lobe were made by use of transverse, dorsal, and sagittal plane images. Thyroid lobe volume was estimated by use of 3 methods.
Results—All thyroid lobes were histologically normal. Mean dimensions for a thyroid lobe were 16.5 × 2.00 × 4.31 mm (length × width × height) using only data from transverse images. Mean thyroid lobar volume was 113.75 mm3 using the sum of areas method. Mean total volume of thyroid tissue was 215.25 mm3 using the sum of areas method.
Conclusions and Clinical Relevance—Results may be useful for computed tomography evaluation of abnormal thyroid glands in cats, which warrants investigation.
Objective—To quantitatively and qualitatively assess the radiographic appearance of the thorax of clinically normal alpaca crias.
Animals—21 clinically normal alpaca crias.
Procedures—Left-right lateral (LR), right-left lateral (RL), dorsoventral (DV), and ventrodorsal (VD) projections of the thorax were acquired. To account for differences in cria size, measurements of thoracic structures were compared with other anatomic landmarks.
Results—Mean ± SD vertebral heart scale was 9.36 ± 0.65 for LR projections, 9.36 ± 0.59 for RL projections, 8.21 ± 0.51 for DV projections, and 8.65 ± 0.57 for VD projections. Dimensions of the heart were compared with the length of the T3 through T5 vertebral bodies, third to fifth rib distance, and thoracic height and width, which provided additional methods of cardiac evaluation. For RL projections, mean ratio of the right cranial pulmonary artery diameter to the third rib width was 0.41 ± 0.10 and mean ratio of the right cranial pulmonary vein to the third rib width was 0.44 ± 0.10. Caudal lobar pulmonary vessels and the caudal vena cava were difficult to quantitatively assess on DV or VD projections. On lateral projections, the trachea was increased in diameter at the origin of the right cranial lobar bronchus. No qualitative differences were found between LR and RL radiographs. The lungs were generally better inflated on VD projections, with more separation of the heart and diaphragm.
Conclusions and Clinical Relevance—Establishment of radiographic values for alpaca crias should prove useful in assessment of thoracic disease in this species.
Objectives—To quantify direction and velocity of blood flow in hepatic veins in dogs under different hemodynamic conditions by use of pulsed-wave Doppler ultrasonography.
Animals—10 healthy dogs.
Procedure—Dogs were anesthetized, and venous flow velocities in the quadrate lobe were measured. Arterial blood pressure, right atrial pressure, pulmonary artery pressure, and cardiac output were measured simultaneously. The timing of each waveform during the cardiac cycle was used to identify velocity profiles. Peak waveform velocities were measured during conditions of light anesthesia with isoflurane (baseline; period 1), cardiovascular depression following administration of highdose isoflurane and esmolol IV (period 2), cardiovascular depression with crystalloid volume expansion (period 3), and high cardiac output induced with dobutamine (period 4). Hemodynamic measurements and maximum waveform velocities were compared among the 4 periods by use of an ANOVA and univariate and multivariate linear regression.
Results—During each study period, 4 distinct, lowvelocity waves were identified. Mean velocities recorded during period 1 were as follows: retrograde atrial contraction a-wave, 7.3 cm/s; antegrade systolic S-wave, 15.0 cm/s; retrograde venous return v-wave, 2.7 cm/s; and antegrade diastolic D-wave, 11.4 cm/s. Mean S:D ratio was 1.27. During periods 3 and 4, Swave velocity increased; D-wave velocity was highest during period 4.
Conclusions and Clinical Relevance—Consistent hepatic venous velocity profiles were observed in healthy dogs under different hemodynamic conditions. These findings provide baseline values that may be useful in evaluating clinical cases, but further study involving healthy, awake dogs and dogs with cardiac and hepatic diseases is required. (Am J Vet Res 2004;65:734–740)
Objective—To determine whether the reported drug-drug interaction between the flea medication spinosad and ivermectin is attributable to inhibition of P-glycoprotein by spinosad.
Animals—6 healthy adult dogs with the ABCB1 wildtype genotype.
Procedures—The study was conducted as a prospective, masked, randomized crossover design. Six dogs were allocated to 2 groups; each dog served as its own control animal. Dogs in one of the groups received spinosad at the manufacturer's recommended dose; the other group received no treatment. Forty-eight hours later, scintigraphic imaging of the head and abdomen were performed with the radiolabeled P-glycoprotein substrate methoxy-isobutyl-isonitrile (sestamibi) in both groups of dogs. After a washout period of 60 days, the dogs in each group received the alternate treatment, and scintigraphic imaging again was performed 48 hours later. Gallbladder-to-liver and brain-to-neck musculature ratios of technetium Tc 99m sestamibi were calculated for each dog and compared between treatments.
Results—No significant differences in gallbladder-to-liver or brain-to-neck musculature ratios were found between treatments.
Conclusions and Clinical Relevance—Results provided evidence that spinosad did not inhibit P-glycoprotein function 48 hours after spinosad was administered at the manufacturer's recommended dose. Further investigations will be necessary to elucidate the mechanism of the reported toxic interaction between spinosad and ivermectin.
Objective—To evaluate and correlate patterns of subchondral bone density and articular cartilage degeneration (derived by use of gross, histologic, and computed tomographic [CT] examinations) in equine third metacarpal condyles with and without osteoarthritis.
Sample Population—8 metacarpophalangeal (MCP) joints (n = 4 horses) without osteoarthritis and 6 osteoarthritis-affected MCP joints (4).
Procedures—Horses were euthanized. The third metacarpal condyles of the joints were examined grossly and via CT (3 slice images/condyle). For 6 condylar zones, mean bone density and pattern of density distribution were determined. Data for osteoarthritis-affected and control joints were compared. Histomorphometric point count analyses identified areas of bone density for comparison with CT density measurements.
Results—Osteoarthritis-affected condyles had heterogeneous subchondral bone with focal resorptive lesions and patterned sclerosis, whereas control condyles had symmetric bone density distribution. In osteoarthritis-affected condyles, bone density determined via gray scale image density analysis was greater (dorsal and medial pattern), compared with control condyles, and differed among zones because of resorption and sclerosis. With regard to bone density in osteoarthritis-affected condyles, histologic findings correlated with CT images, and bone lesions were significantly correlated with cartilage lesions.
Conclusions and Clinical Relevance—In horses, heterogeneous distribution and greater subchondral bone density were characteristic of osteoarthritis-affected condyles, compared with control condyles. Subchondral bone lesions correlated with overlying cartilage lesions in osteoarthritis-affected MCP joints. Identification of CT image characteristics appears to predict the presence of a cartilage lesion in MCP joints of horses with osteoarthritis.
Objective—To measure the effects of lowmolecular-weight inhibitors on the activity of bovine neutrophil matrix metalloproteinase 9 (MMP-9).
Sample Population—Bovine MMP-9 purified from bovine neutrophilconditioned medium.
Procedures—Neutrophils were degranulated by stimulation with phorbol ester. Enzyme purification was performed by use of gelatin affinity and gel-filtration chromatography. Activated enzyme was incubated with inhibitors prior to addition of substrate (gelatin fluorescein conjugate or fluorogenic peptide). Rates of enzymatic cleavage were determined by monitoring fluorescence as the reactions progressed. Values of IC50 (molar concentration of compound that inhibits specific activity by 50%) and KI (in vitro inhibition constant) were determined.
Results—Rates of enzymatic activity of monomeric and dimeric bovine MMP-9 measured by use of gelatin and peptide substrates were linear with respect to time and concentrations of enzyme and substrate. The MMP-9 was potently inhibited by hydroxamic acids (IC50 for gelatin, 29.2 to 55.7nM; IC50 for peptide, 4.8 to 24.6nM; KI, 0.2 to 0.5nM), whereas tetracyclines (IC50 for gelatin, 30.1 to 112.7MM; IC50 for peptide, 48.0 to 123.8MM; KI, 25.2 to 61.4µM) and chlorhexidine (IC50 for gelatin, 139.1MM; IC50 for peptide, 672.5MM to 1.7mM; KI, 495.0 to 663.0MM) had limited inhibition. Gelatinase-specific inhibitor SB-3CT had intermediate potency (IC50 for peptide, 185.0 to 290.0nM; KI, 66.5 to 86.0nM).
Conclusions and Clinical Relevance—Bovine MMP-9 was potently inhibited by hydroxamic acids and gelatinase inhibitor. These compounds may be useful as modulators of neutrophil-mediated protease activity in cattle.
Objective—To characterize and purify covalent complexes of matrix metalloproteinase-9 (MMP-9) and haptoglobin released by bovine granulocytes in vitro.
Sample Population—Blood samples obtained from healthy cows and cows with acute and chronic inflammation to obtain WBCs and sera.
Procedures—WBCs were isolated by differential centrifugation, hypotonic lysis of RBCs, and degranulated by stimulation with phorbol ester (20 ng/mL). Cell-conditioned medium was subjected to affinity and gel chromatography and purified proteins subjected to SDS- PAGE gelatin zymography, western blot analysis, Coomassie blue staining, and peptide mass spectrometry for protein identification. Sera of cows hospitalized for acute and chronic septic conditions and of clinically normal cows were analyzed with similar methods.
Results—Matrix metalloproteinase-9 was released from neutrophils in vitro and migrated to a molecular mass of approximately 220 kd (prodimer), approximately 105 kd (promonomer), and > 220 kd (high–molecular mass complexes). These high–molecular mass complexes were composed of α- and β-haptoglobin and MMP-9 (ratio13:13:1). Complexes of MMP-9 and haptoglobin had biochemical properties of both its protein constituents (ie, enzymatic activity toward gelatin and hemoglobin binding). Complexes of MMP-9 and haptoglobin were also detected in sera of cows with acute inflammation, but not in clinically normal cows or cows with chronic disease.
Conclusions and Clinical Relevance—A fraction of neutrophil MMP-9 is released in complex with haptoglobin. The complex is present in granules and retains biological activity of its components. Detection of the complex in serum may provide an indicator of acute inflammation.
Objective—To compare the iridocorneal angle (ICA) and angle opening distance (AOD) in dogs with cataractous and noncataractous lenses; evaluate cataractous eyes ultrasono-graphically for association of postoperative ocular hypertension (POH) with the ICA, AOD, and postoperative echogenic anterior chamber debris; and evaluate intraobserver reliability associated with ICA and AOD measurements.
Animals—56 dogs with 102 cataracts, and 23 clinically normal dogs.
Procedures—Ultrasound biomicroscopy was performed on 102 eyes of 56 dogs before and after cataract surgery and on 46 nondilated and dilated eyes of 23 clinically normal dogs. Cataract stage, ICA, AOD, and association with POH were assessed.
Results—Cataract stage and ICA or AOD were not significantly associated; however, ICA and AOD typically decreased with increasing cataract maturity. Before and after pupillary dilation, AODs were significantly smaller in cataractous eyes than in noncataractous eyes. Before surgery, ICA and AOD in eyes without pupillary dilation were significantly associated with POH. At > 13°, odds of developing POH increased by 11% for each degree increase in the ICA. Postoperative anterior chamber debris was not associated with POH. Coefficient of variation for repeated measurements was 10% for the ICA and 9.5% for the AOD, suggesting good intraobserver reliability.
Conclusions and Clinical Relevance—In this study, dogs with larger ICA and AOD measurements before surgery were at greater risk of developing POH. This information may be useful for future studies to determine whether preventative treatment for POH administered prior to surgery may be beneficial.
Objective—To compare quantitative densitometric computed tomography (CT), morphometric, and histologic data of normal lungs in dogs with similar parameters obtained after induction of an acute inflammatory response and determine whether CT densitometry correlated with histopathologic changes.
Animals—6 healthy adult dogs.
Procedure—After initial CT, 1 mL of 0.1M hydrochloric acid (HCl) and 3 mL of autologous blood were instilled into the right middle (RM) and caudal segment of the left cranial (LCCd) lung lobes, respectively. Immediately and 24 hours after instillation, CT was repeated. At 24 hours, dogs were euthanatized and lungs were fixed and sampled for morphometric and histologic evaluation. The CT data were compared with lung morphology and morphometry by use of unpaired t tests. Comparison with lungs from control dogs was performed using Spearman rank correlation coefficients.
Results—Mean Hounsfield units (HU) from control and baseline HU from experimental dogs were identical. Immediately after instillation of HCl or blood, there was increased attenuation in both lobes. Autologous blood initially induced severe changes that almost completely resolved at 24 hours; HCl induced severe changes at 24 hours. Significant increases in percentage of parenchymal airspace and alveolar diameter resulted in decreased surface area-to-volume ratio in lobes receiving HCl. Histologic scores were significantly higher in the RM lobe, compared with controls.
Conclusions and Clinical Relevance—Computed tomography attenuation correlated well with histomorphometry and histologic findings in this model. Lung lesions after autologous blood were transient and of limited severity. Lesions induced by HCl were severe; alterations in morphometric and histologic parameters were reflected in CT attenuation measurements. (Am J Vet Res 2004;65:1114–1123)