REPEATABILITY OF DOPPLER ULTRASONOGRAPHIC MEASUREMENT OF EQUINE DIGITAL BLOOD FLOW

The repeatability and sensitivity of Doppler ultrasonographic measurement of lateral digital arterial and venous blood flow has not been previously determined. Doppler ultrasonography was used to measure blood flow within the forelimb lateral digital vessels in one normal adult Thoroughbred horse on six occasions and in six normal adult Thoroughbred horses on three occasions, each occasion being at least 1 h apart, to determine the within- and between-horse variation. The values obtained from the right and left lateral digital vessels did not differ significantly. The within-horse coefficients of variation (CV) for arterial and venous measurements were all acceptable (< 11%); the between-horse CV were acceptable (< 7%) for all parameters except TaVa (average velocity of first peak of arterial waveform) and TaVb (average velocity of remainder of arterial waveform). The within-horse intraclass correlation coefficients (ICC) demonstrated excellent repeatability (> or = 0.71) for all parameters except venous diameter; the between-horse ICC demonstrated good to excellent repeatability (> or = 0.67) for all parameters except TaVb. Doppler ultrasonography can detect differences of 0.005 and 0.01 ml/ min in digital arterial and venous flow, respectively, using measurements from six horses on three occasions (80% power; P < 0.05). Thus, the technique is sufficiently repeatable and sensitive to be able to detect changes in flow during different physiological or pathological states or following pharmacologic intervention.     

Simultaneous application of the vascular endothelial growth factor (VEGF) receptor inhibitor PTK787/ZK 222584 and ionizing radiation does not further reduce the growth of canine oral melanoma xenografts in nude mice

PTK787/ZK 222584 is an inhibitor of the vascular endothelial growth factor (VEGF) receptor tyrosine kinases. In this study, the effectiveness of PTK787/ZK 222584 and radiation on canine oral melanoma xenografts was assessed. Xenografts were treated with radiotherapy (4x6Gy), or with PTK787/ZK 222584, or with a combination of both. Treatment efficacy was assessed using a tumour growth delay assay, serial power Doppler and pO(2) measurements during and after therapy. There was a significant growth delay for the group treated with radiation alone and for the combined treatment group. However, tumour growth delay was similar in both groups. Tumours were hypoxic before irradiation and no significant re-oxygenation occurred during therapy. In all tumours, vascularity and perfusion were significantly lower at the end of the study but no significant differences in perfusion, vascularity and oxygenation status were observed between and within treatment groups. The combination of PTK787/ZK 222584 and radiotherapy did not perform better than radiotherapy alone in this model.     

MAGNETIC RESONANCE IMAGING CHARACTERISTICS OF ASCENDING HEMORRHAGIC MYELOMALACIA IN A DOG

A 4-year-old neutered female terrier-cross was evaluated for an acute onset of paraplegia. Utilizing magnetic resonance (MR) imaging, the cause of the neurologic deficits was determined to be a lumbar intervertebral disc extrusion. The MR study additionally demonstrated parenchymal hyperintensity on T2-weighted images and similarly located diffuse hypointensity on gradient echo images, cranial and caudal to the compressive extradural lesion. Hemorrhagic myelomalacia was suspected based on these MR characteristics, which was subsequently confirmed surgically and histopathologically.     

IMPACT OF TISSUE INHOMOGENEITY ON DOSE DISTRIBUTION IN THE CANINE CARPAL AND TARSAL REGIONS FOR COBALT AND 6 MV PHOTONS

We quantified the effect of tissue inhomogeneity on dose distribution in a canine distal extremity resulting from treatment with cobalt photons and photons from a 6 MV accelerator. Monitor units for a typical distal extremity treatment were calculated by two methods, using equally weighted, parallel-opposed fields. The first method was a computed tomography (CT)-based, computerized treatment plan, calculated without inhomogeneity correction. The second method was a manual point dose calculation to the isocenter. A computerized planning system was then used to assess the dose distribution achieved by these two methods when tissue inhomogeneity was taken into account. For cobalt photons, the median percentage of the planning target volume (PTV) that received <95% of the prescribed dose was 4.5% for the CT-based treatment plan, and 26.2% for the manually calculated plan. For 6 MV photons, the median percentage of the PTV that received <95% of the prescribed dose was <1% for both planning methods. The PTV dose achieved without using inhomogeneity correction for cobalt photons results in potentially significant under dosing of portions of the PTV.     

MAGNETIC RESONANCE IMAGING OF THE CANINE BRAIN AT 7 T

The purpose of this study was to describe relevant canine brain structures as seen on T2-weighted images following magnetic resonance (MR) imaging at 7 T and to compare the results with imaging at 1.5 T. Imaging was performed on five healthy laboratory beagle dogs using 1.5 and 7 T clinical scanners. At 1.5 T, spin echo images were acquired, while gradient echo images were acquired at 3 T. Image quality and conspicuity of anatomic structures were evaluated qualitatively by direct comparison of the images obtained from the two different magnetic fields. The signal-to-nose ratio (SNR) and contrast-to-noise ratio (CNR) were calculated and compared between 1.5 and 7 T. The T2-weighted images at 7 T provided good spatial and contrast resolution for the identification of clinically relevant brain anatomy; these images provided better delineation and conspicuity of the brain stem and cerebellar structures, which were difficult to unequivocally identify at 1.5 T. However, frontal and parietal lobe and the trigeminal nerve were difficult to identify at 7 T due to susceptibility artifact. The SNR and CNR of the images at 7 T were significantly increased up to 318% and 715% compared with the 1.5 T images. If some disadvantages of 7 T imaging, such as susceptibility artifacts, technical difficulties, and high cost, can be improved, 7 T clinical MR imaging could provide a good experimental and diagnostic tool for the evaluation of canine brain disorders.     

Exercising the Pregnant Mare from Day 16 to Day 80 of Gestation

Our previous research has demonstrated moderate exercise can be detrimental to early pregnancy in the mare, but little work has examined exercise after pregnancy has been detected. We exercised mares (n = 8) 6 days a week for 45 min from Day 16 until Day 80 of gestation. Color Doppler ultrasonography was used to evaluate embryonic vesicle size, fetal length, and uterine blood flow. Blood was sampled every other day to analyze cortisol and progesterone concentrations. Results indicated that exercising pregnant mares (n = 4) led to greater (P < .01) cortisol concentrations 30 min after the exercise period. No overall treatment effect could be detected in progesterone concentrations; however, following Day 60 of gestation, progesterone concentrations were lower (P < .05) in exercised mares. Additionally, progesterone concentrations peaked earlier in exercised mares at Day 52 of gestation compared to peak levels at Day 68 of gestation for control mares. No significant effects were detected in embryonic vesicle size. Fetal length tended (P = .06) to be longer in the conceptus of exercised mares. Uterine blood flow did not differ between groups but increased as pregnancy progressed (P < .001) in both groups. All mares in this study went on to deliver healthy foals and suffered no difficulties during parturition. These results indicated that moderate exercise was not detrimental to mare pregnancy.     

MAGNETIC RESONANCE IMAGING OF A MEDULLARY DERMOID CYST WITH SECONDARY HYDROCEPHALUS IN A DOG

Magnetic resonance images were acquired of the brain of a 7-year-old male Golden Retriever with hydrocephalus secondary to a medullary lesion. Images were acquired prior to and 4 weeks following surgical treatment for the hydrocephalus, and the dog was euthanased following the second imaging session. The MR images demonstrated a medullary lesion with patchy but predominantly hyperintense signal with both T1- and T2-weighting, within which small areas of low signal were scattered. There was little edema associated with this lesion and no enhancement with gadolinium. Postmortem examination revealed the medullary mass to be a dermoid cyst. Several small nodular lesions were identified within the central nervous system on the magnetic resonance images whose origin was uncertain on postmortem examination.     

EFFECT OF HYDRATION ON SIGNAL INTENSITY OF GELATIN PHANTOMS USING LOW-FIELD MAGNETIC RESONANCE IMAGING: POSSIBLE APPLICATION IN OSTEOARTHRITIS

Five gelatin phantoms were constructed to study the effect of matrical hydration on magnetic resonance imaging (MRI) signal intensity using a low-field strength imager. Water content of the phantoms ranged from 75 to 95% weight/weight. Signal intensity values of each phantom were measured using five imaging sequences: proton density, T1-weighted, T2-weighted, inversion recovery with short inversion time, and inversion recovery with long inversion time. There was significant positive correlation (p < .05) of signal intensity with differences in hydration using the T2-weighted sequence and the inversion recovery sequence with short inversion time. Significant negative correlations (p < .05) were found with T1-weighted imaging and the inversion recovery sequence with long inversion time. In a second part of the study, in vivo focal variations in MRI signal intensity were evaluated in a canine cranial cruciate ligament deficient model of osteoarthritis. Signal intensity measurements were obtained from multiple areas of articular cartilage to identify an initial stage in osteoarthritis that is characterized in part by increased hydration of articular cartilage. At 6 weeks post-transection of the cranial cruciate ligament, an increase in signal intensity was detected in the articular cartilage of the weight-bearing portion of the lateral femoral condyle and the caudal portion of the medial tibial condyle with T1-weighted imaging. The increase in signal intensity may reflect increased proteoglycan synthesis by chondrocytes that also occurs early in the pathogenesis of osteoarthritis.     

从羊皮肤组织中提取总RNA方法的改进

在借鉴动物组织RNA提取方法的基础上,结合使用RNAlater保存液和Trizol试剂,改进了提取步骤和反应体系。利用改良的总RNA提取方法,从羊皮肤组织中快速、高效地提取了高质量总RNA,提取的总RNA可满足基于RNA分析技术的相关分子生物学试验需要。     

冷环境中解偶联蛋白对动物体温的调节作用

解偶联蛋白属线粒体内膜载体蛋白,存在动物体的棕色脂肪组织（brown adipose tissue,BAT）、白色脂肪组织（white adipose tissue,WAT）、骨胳肌以及各种器官中。这些组织器官是哺乳动物及禽类非颤抖产热（NST）及其它产热作用的主要点位,对动物的体温维持和能量平衡调节起重要作用。