TRUNCATION ARTIFACT IN MAGNETIC RESONANCE IMAGES OF THE CANINE SPINAL CORD

The truncation artifact in magnetic resonance (MR) images is a line of abnormal signal intensity that occurs parallel to an interface between tissues of markedly different signal intensity. In order to demonstrate the truncation artifact in sagittal images of the canine spinal cord and the effect of changing spatial resolution, we conducted an experimental in vitro study. A section of fixed canine spinal cord was imaged using a 1.5T magnet. Spatial resolution was increased by increasing the acquisition matrix and reconstruction matrix, producing series of T2‐weighted (T2w) images with the following pixel sizes: A, 1.6 (vertical) × 2.2 mm² (horizontal); B, 1.2 × 1.7 mm²; C, 0.8 × 1.1 mm²; D, 0.4 × 0. 6 mm². Plots of mean pixel value across the cord showed variations in signal intensity compatible with truncation artifact, which appeared as a single, wide central hyperintense zone in low‐resolution images and as multiple narrower zones in high spatial resolution images. Even in images obtained using the highest spatial resolution available for the MR system, the edge of the spinal cord was not accurately defined and the central canal was not visible. The experiment was repeated using an unfixed spinal cord specimen with focal compression applied to mimic a pathologic lesion. Slight hyperintensity was observed within the spinal cord at the site of compression although the cord was normal histologically. Results of this study suggest that caution should be applied when interpreting hyperintensity affecting the spinal cord in T2w sagittal images of clinical patients because of the possibility that the abnormal signal could represent a truncation artifact.     

Effects of a high milk intake during the pre‐weaning period on nutrient metabolism and growth rate in Japanese Black cattle

This study aimed to determine the effects of feeding an increased volume of high‐fat milk during the early post‐natal life on metabolite concentrations in the blood, the expression of key genes regulating intermediary metabolism in the skeletal muscles, and the rate of growth of Japanese Black cattle. All calves were fed a high‐fat milk replacer (crude protein, 26%; crude fat, 25.5%; total dissolved nitrogen, 116%). Control calves (n = 4) were nursed with 500 g milk replacer until 3 months of age, whereas calves in the experimental group (n = 4) were nursed with 1800 g milk replacer until 3 months, and then the volume was gradually reduced until 5 months. Body weight was significantly higher in the experimental group than in the control group at 7 months. Plasma glucose concentrations were significantly lower in the experimental group. Expression of glucose‐transporter‐4 messenger RNA (mRNA) was lower, whereas that of glucose transporter 1, cluster of differentiation 36, and carnitine palmitoyltransferase‐1b mRNA was significantly higher in the Longissimus thoracis of the experimental group. Nutritional status during early post‐natal life appears to strongly influence the growth rate and glucose and lipid metabolism in Japanese Black cattle.     

Achromatopsia in three sibling Labrador Retrievers in the UK

Achromatopsia was identified in three Labrador Retriever littermates. The dogs demonstrated day blindness, negotiating obstacles under low‐light conditions, but apparently blind when outdoors. One of the dogs presented with immature bilateral diffuse posterior cortical cataracts and clinical signs of day blindness became apparent following cataract extraction surgery. Electroretinography demonstrated an absence of a cone photoreceptor response to a bright stimulus and a flicker response of 30 Hz in all three dogs. No fundic lesions have been apparent ophthalmoscopically in any of the dogs as the initial presentation of each case. No abnormalities were detected with DNA screening for known mutations of the CNGB3 gene in any of the dogs.     

Identification of infrared absorption spectral characteristics of synovial fluid of horses with osteochondrosis of the tarsocrural joint

OBJECTIVE: To determine the feasibility of the use of Fourier-transform infrared (FTIR) spectroscopy within the midinfrared range to differentiate synovial fluid samples of joints with osteochondrosis from those of control samples. ANIMALS: 33 horses with osteochondrosis of the tarsocrural joint and 31 horses free of tarsocrural joint disease. PROCEDURES: FTIR spectroscopy of synovial fluid was used. Sixty-four synovial fluid samples from the tarsocrural joint were collected. Of these, 33 samples were from horses with radiographic evidence of osteochondrosis of the tarsocrural joint and 31 from control joints. Disease-associated features within infrared spectra of synovial fluid were statistically selected for spectral classification, and the variables identified were used in a classification model. Linear discriminant analysis and leave-one-out cross-validation were used to develop a classifier to identify joints with osteochondrosis. RESULTS: 12 significant subregions were identified that met the selection criteria. The stepwise discriminant procedure resulted in the final selection of 6 optimal regions that most contributed to the discriminatory power of the classification algorithm. Infrared spectra derived from synovial fluid of joints with osteochondrosis were differentiated from the control samples with accuracy of 77% (81% specificity and 73% sensitivity). CONCLUSIONS AND CLINICAL RELEVANCE: The disease-associated characteristics of infrared spectra of synovial fluid from joints with osteochondrosis may be exploited via appropriate feature selection and classification algorithms to differentiate joints with osteochondrosis from those of control joints. Further study with larger sample size including age-, breed-, and sex-matched control horses would further validate the clinical value of infrared spectroscopy for the diagnosis of osteochondrosis in horses.     

In vitro effects of bethanechol on specimens of intestinal smooth muscle obtained from the duodenum and jejunum of healthy dairy cows

OBJECTIVE: To describe the in vitro effects of bethanechol on contractility of smooth muscle preparations from the small intestines of healthy cows and define the muscarinic receptor subtypes involved in mediating contraction. SAMPLE POPULATION: Tissue samples from the duodenum and jejunum collected immediately after slaughter of 40 healthy cows. PROCEDURES: Cumulative concentration-response curves were determined for the muscarinic receptor agonist bethanechol with or without prior incubation with subtype-specific receptor antagonists in an organ bath. Effects of bethanechol and antagonists and the influence of intestinal location on basal tone, maximal amplitude (A(max)), and area under the curve (AUC) were evaluated. RESULTS: Bethanechol induced a significant, concentration-dependent increase in all preparations and variables. The effect of bethanechol was more pronounced in jejunal than in duodenal samples and in circular than in longitudinal preparations. Significant inhibition of the effects of bethanechol was observed after prior incubation with muscarinic receptor subtype M(3) antagonists (more commonly for basal tone than for A(max) and AUC). The M(2) receptor antagonists partly inhibited the response to bethanechol, especially for basal tone. The M(3) receptor antagonists were generally more potent than the M(2) receptor antagonists. In a protection experiment, an M(3) receptor antagonist was less potent than when used in combination with an M(2) receptor antagonist. Receptor antagonists for M(1) and M(4) did not affect contractility variables. CONCLUSIONS AND CLINICAL RELEVANCE: Bethanechol acting on muscarinic receptor sub-types M(2) and M(3) may be of clinical use as a prokinetic drug for motility disorders of the duodenum and jejunum in dairy cows.