peer reviewed | The purpose of this study was to assess the impact of freezing and thawing on MR images of equine feet examined ex vivo. Nine equine cadaver digits were first imaged at room temperature (T0). Among the 9 digits, 3 (group 1) were imaged in a 3 Tesla MR system after one and after 2 freezing-thawing cycles. Digits of group 1 were thawed in a cold room at 4°C for 36h. Three other digits (group 2) were imaged after one freezing-thawing cycle. Digits of group 2 were thawed in a cold room at 4°C and then rescanned after 24h at room temperature. The last 3 digits (group 3) were scanned after one freezing-thawing cycle. Digits of group 3 were thawed at room temperature for 24h. Sequences used were Spin Echo (SE) T1, Turbo Spin Echo (TSE) T2 and proton density (PD), Short Tau Inversion Recovery (STIR), Double Echo Steady State (DESS), 3D Gradient Echo (GE) T1 and 2D GE T2*. Images obtained on the fresh limbs at room temperature were subjectively compared side by side to images obtained at the different freezing-thawing cycles. A quantitative analysis to assess signal change between examinations was realized by measuring signal to noise ratio (SNR). Visibility and margination of the anatomical structures of the foot and overall image quality were subjectively considered unchanged except for the hoof where the lamina was considered less visible distally after freezing and thawing in the GE T2* and in TSE T2 and PD sequences. Quantitative analysis demonstrated SNR changes in the bone marrow only in the distal phalanx in the SE T1 sequence when the feet were thawed at room temperature. When the feet were thawed in a cold room at 4°C, bone marrow SNR changes were present in the SE T1, GE T1 and TSE PD sequences. Signal changes were significant in the synovial recess when the thawing process was made at 4°C and not when the thawing process was at ambient temperature. The soft tissue structures and the hoof capsule showed significant changes with an increase of SNR, except in STIR, after freezing and thawing at 4°C and at room temperature. SNR changes in the soft tissues were mainly present in GE sequences.

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Liver function tests help to investigate actual liver function. In dogs, only a few tests are available. We evaluated the formation of monoethylglycinexylidide (MEGX) in clinically healthy dogs to assess the usefulness of this liver function test in dogs. Twenty-five healthy dogs were used in this study. The MEGX test was done according to human protocols. The results of our study showed that dogs synthesize MEGX after the administration of lidocaine. There was no age dependence of this test in dogs and no significant difference between measurements obtained at 15 and 30 min after administration of lidocaine. Female dogs had significantly (P < 0.05) higher concentrations of MEGX 15 min after administration. The reference interval for dogs after 15 min is 34 to 79 μg/L and after 30 min 39 to 89 μg/L. In conclusion, the MEGX test may be an additional liver function test in dogs.

Final observations on experimental transmission of chronic wasting disease (CWD) from elk (Cervus elaphus nelsoni) and white-tailed deer (Odocoileus virginianus) to fallow deer (Dama dama) are reported herein. During the 5-year study, 13 fawns were inoculated intracerebrally with CWD-infected brain material from white-tailed deer (n = 7; Group A) or elk (n = 6; Group B), and 3 other fawns were kept as uninoculated controls (Group C). As described previously, 3 CWD-inoculated deer were euthanized at 7.6 mo post-inoculation (MPI). None revealed presence of abnormal prion protein (PrPd) in their tissues. At 24 (Group A) and 26 (Group B) MPI, 2 deer were necropsied. Both animals had a small focal accumulation of PrPd in their midbrains. Between 29 and 37 MPI, 3 other deer (all from Group A) were euthanized. The 5 remaining deer became sick and were euthanized between 51 and 60 MPI (1 from Group A and 4 from Group B). Microscopic lesions of spongiform encephalopathy (SE) were observed in only these 5 animals; however, PrPd was detected in tissues of the central nervous system by immunohistochemistry, Western blot, and by commercial rapid test in all animals that survived beyond 24 MPI. This study demonstrates that intracerebrally inoculated fallow deer not only amplify CWD prions, but also develop lesions of spongiform encephalopathy.

The aim of this study was to evaluate the performance characteristics of an automated immunoassay for canine insulin-like growth factor 1 (IGF-1) measurement and to investigate the possible effects of some sources of variation, such as diurnal variations, feeding/fasting cycles, and glucocorticoid administration, in dogs. The immunoassay evaluated had an adequate analytical performance with intra- and inter-assay coefficients of variation (CVs) lower than 10%, linear regression equations with correlation coefficients of 0.9993 and 0.9988 after serial dilutions, and a limit of quantification of 7.1 ng/mL that was even lower than that reported by the manufacturer. The assay was significantly affected by hemolysis and lipemia producing a significant decrease in IGF-1 concentrations, but not by bilirubinemia. Serum IGF-1 concentrations did not show significant diurnal changes in fed or fasted dogs and were not affected by glucocorticoid administration.

Tissues unsuitable for standard immunohistochemical and histopathological examinations for chronic wasting disease (CWD) in cervids and for scrapie in sheep are frequently submitted for testing. This study investigated the effects of experimental autolysis on the detection of abnormal prion protein (PrPsc) in lymphoid and central nervous system (CNS) tissues from elk and sheep. The PrPsc was detected using a Western blotting (WB) test following PrPsc enrichment using sodium phosphotungstic acid (PTA) precipitation (PTA-WB). A commercial enzyme-linked immunosorbent assay (ELISA) was used as a reference test for quantitative measurement. This study showed that the amount of PrPsc in lymphoid and CNS tssues from elk and sheep decreased gradually as a result of autolysis, but PrPsc was still detectable after 5 and 15 d incubation at 37°C by PTA-WB for all lymphoid and CNS samples. The results of the ELISA supported those of PTA-WB, particularly for CNS tissues. In conclusion, autolysis at 37°C for 15 d would not significantly affect the detection of PrPsc in lymphoid and CNS tissues by WB and ELISA and, particularly, PTA-WB is a valuable and alternative confirmatory test to detect PrPsc in autolyzed lymphoid and CNS samples.

Objective—To investigate the density of the primary epidermal lamellae (PEL) around the solar circumference of the forefeet of near-term fetal feral and nonferal (ie, domesticated) horses. Sample—Left forefeet from near-term Australian feral (n = 14) and domesticated (4) horse fetuses. Procedures—Near-term feral horse fetuses were obtained from culled mares within 10 minutes of death; fetuses that had died in utero 2 weeks prior to anticipated birth date and were delivered from live Thoroughbred mares were also obtained. Following disarticulation at the carpus, the left forefoot of each fetus was frozen during dissection and data collection. In a standard section of each hoof, the stratum internum PEL density was calculated at the midline center (12 o'clock) and the medial and lateral break-over points (11 and 1 o'clock), toe quarters (10 and 2 o'clock), and quarters (4 and 6 o'clock). Values for matching lateral and medial zones were averaged and expressed as 1 density. Density differences at the 4 locations between the feral and domesticated horse feet were assessed by use of imaging software analysis. Results—In fetal domesticated horse feet, PEL density did not differ among the 4 locations. In fetal feral horse feet, PEL density differed significantly among locations, with a pattern of gradual reduction from the dorsal to the palmar aspect of the foot. The PEL density distribution differed significantly between fetal domesticated and feral horse feet. Conclusions and Clinical Relevance—Results indicated that PEL density distribution differs between fetal feral and domesticated horse feet, suggestive of an adaptation of feral horses to environment challenges.

Objective—To evaluate the impact of oxytetracycline exposure on horizontal transfer of an antimicrobial resistance plasmid. Sample—Populations of Salmonella enterica subsp enterica serovar Typhimurium and Escherichia coli. Procedures—Mixed populations of plasmid donor (Salmonella Typhimurium) and recipient (E coli) bacteria were assigned to 1 of 2 simulated oxytetracycline dosing regimens (high peak concentration-short elimination half-life [HC-SHL] or low peak concentration—long elimination half-life [LC-LHL]) or served as untreated control replicates. Donor, recipient, and transconjugant (E coli that acquired the plasmid) bacteria populations were quantified at 12, 24, and 36 hours after oxytetracycline administration by use of culture on selective bacterial growth media. Results—The ratio of transconjugant to donor bacteria was significantly reduced in the oxytetracycline-exposed replicates, compared with the ratio for the control replicates, at 12 hours. At 24 and 36 hours, results for the HC-SHL regimens were not significantly different from results for the respective control replicates, and results for the LC-LHL regimens also were not significantly different from results for the respective control replicates. The oxytetracycline concentration at these time points (12 hours in the HC-SHL regimen and all 3 time points in the LC-LHL regimen) were in excess of the minimum inhibitory concentration of the recipient bacteria. Conclusions and Clinical Relevance—Transfer of antimicrobial resistance plasmids may be suppressed in vitro by oxytetracycline exposure at concentrations greater than the minimum inhibitory concentration of the recipient bacteria.

Objective: To assess the effect of computed tomography (CT) scan protocols (radiation amounts) and fabrication methods on biomodel accuracy and variability. Sample: Cadaveric femur of a Basset Hound. Procedures: Retroreconstructions (n = 158) were performed of 16 original scans and were visually inspected to select 17 scans to be used for biomodel fabrication. Biomodels of the 17 scans were made in triplicate by use of 3 freeform fabrication processes (stereolithography, fused deposition modeling, and 3-D printing) for 153 models. The biomodels and original bone were measured by use of a coordinate measurement machine. Results: Differences among fabrication methods accounted for 2% to 29% of the total observed variation in inaccuracy and differences among method-specific radiation configurations accounted for 4% to 44%. Biomodels underestimated bone length and width and femoral head diameter and overestimated cortical thickness. There was no evidence of a linear association between thresholding adjustments and biomodel accuracy. Higher measured radiation dose led to a decrease in absolute relative error for biomodel diameter and for 4 of 8 cortical thickness measurements. Conclusions and Clinical Relevance: The outside dimensions of biomodels have a clinically acceptable accuracy. The cortical thickness of biomodels may overestimate cortical thickness. Variability among biomodels was caused by model fabrication reproducibility and, to a lesser extent, by the radiation settings of the CT scan and differences among fabrication methods.

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.