Selection of a recombinant Marek's disease virus in vivo through expression of the Marek's EcoRI-Q (Meq)-encoded oncoprotein: characterization of an rMd5-based mutant expressing the Meq of strain RB-1B

Marek's disease (MD) is a highly contagious viral disease of chickens (Gallus gallus domesticus) caused by MD virus (MDV), characterized by paralysis, neurologic signs, and the rapid onset of T-cell lymphomas. MDV-induced T-cell transformation requires a basic leucine zipper protein called Marek's EcoRI-Q-encoded protein (Meq). We have identified mutations in the coding sequence of Meq that correlated with virus pathotype (virulent, very virulent, and very virulent plus). The aim of this study was to determine whether recombinant viruses could be isolated based on Meq expression through in vivo selection. Chicken embryo fibroblasts (CEFs) were cotransfected with an rMd5 strain-based Meq deletion virus (rMd5deltaMeq) and meq loci from strains representing different pathotypes of MDV. Transfected CEFs were inoculated into chickens in two independent studies. We were able to isolate a single recombinant virus, rMDV-1137, in a contact-exposed chicken. rMDV-1137 had recombined two copies of the meq gene of RB-1B and was found to have pathogenicity similar to both RB-1B and rMd5 parental strains. We found the RB-1B- and rMd5-induced lymphomas showed differences in composition and that rMDV-1137-induced lymphomas were intermediate in their composition. We were able to establish cell lines from both RB-1B- (MDCC-UD35, -UD37) and rMDV-1137 (MDCC-UD36, -UD38)-induced, but not rMd5-induced, lymphomas. To date, no rMd5- or parent Md5-transformed T-cell lines have been reported. Our results suggest that 1) a recombinant MDV can be selected on the basis of oncogenicity; 2) changes in Meq sequence seem to affect tumor composition and the ability to establish cell lines; and 3) in addition to meq, other genomic loci affect MDV pathogenicity and oncogenicity.     

Pharmacodynamics of carvedilol in conscious, healthy dogs

The purpose of the study reported here was to determine the magnitude and duration of beta-blocking efficacy, determine an effective dose and dosing interval, and document safety and tolerability of carvedilol given orally in clinically normal dogs. Pharmacodynamic data were evaluated in conscious, unrestrained, healthy hound dogs at baseline and after long-term oral administration of carvedilol (1.5 mg/kg of body weight PO q12h for >5 days). At baseline, heart rate (HR) and blood pressure (BP) data were collected continuously for 24 hours, and complete echocardiography was performed. This protocol was repeated after long-term oral carvedilol administration. Additionally, isoproterenol was administered to evaluate the magnitude and duration of the nonselective beta-blocking efficacy of carvedilol. An isoproterenol challenge was performed 0.75, 1.5, 2.25, 4, 6, 12, and 24 hours after carvedilol administration, with echocardiography being performed once at 2 hours. Plasma samples were obtained prior to each challenge time point for determination of plasma carvedilol concentration. Time series regression analysis indicated no difference between baseline and carvedilol-induced HR or BP trend lines in 6 of 8 dogs. In 2 of 8 dogs, HR, after long-term carvedilol administration, was reduced. Carvedilol attenuated isoproterenol-induced changes in HR by 54-76% through 12 hours and by 30% at 24 hours. The BP changes were attenuated by 80-100% through 12 hours. These data suggest that carvedilol (1.5 mg/kg PO q12h) in healthy, conscious dogs confers nonselective beta blockade for 12 hours, with minimal effects on resting HR, BP, and echocardiographic variables. Additionally, the magnitude of beta blockade correlated strongly to peak plasma carvedilol concentration, suggesting that therapeutic drug monitoring may be clinically useful.     

DIAGNOSTIC VALUE OF ULTRASONOGRAPHY IN DIFFERENTIATING ENTERITIS FROM INTESTINAL NEOPLASIA IN DOGS

One hundred and fifty dogs with histopathologically confirmed intestinal disease were evaluated retrospectively. Sixty-one dogs had enteritis and 89 dogs had intestinal neoplasia. Ultrasonographic findings including the thickness and distribution of the intestinal lesion, the integrity of intestinal wall layering, regional lymph node thickness, the location of the intestinal segment involved, and regional motility were evaluated. Dogs with intestinal tumor had wall thickness (1.5 cm) significantly greater than dogs with NSE lesions (0.6 cm; p < 0.001). Ninety-nine percent of dogs with intestinal tumor had loss of wall layering while 88% of dogs with NSE had normal or altered wall layering (p < 0.001). Dogs with NSE were significantly more likely to have diffuse lesion (72%) than dogs with intestinal tumor (2%; p < 0.001). Lymph node median thickness in 24/61 dogs with NSE was 1.00 cm. The median thickness of the lymph nodes in 56/89 dogs with intestinal tumors was 1.9 cm. A multivariate analysis showed that loss of wall layering alone was an excellent predictive factor in differentiating intestinal tumor from NSE. In our population, dogs with loss of intestinal wall layering were 50.9 times more likely to have a tumor than enteritis.     

ULTRASOUND EVALUATION OF SMALL BOWEL THICKNESS COMPARED TO WEIGHT IN NORMAL DOGS

The use of ultrasound to measure small bowel thickness is an important part of any ultrasound examination of the abdomen. Increased thickness of the intestinal wall is a hallmark for the detection of diseases ranging from inflammatory bowel disease to neoplasia. Our subjective impression has been that dogs with no clinical signs of gastrointestinal disease often have sonographic measurements greater than published norms. The purpose of this study was to prospectively reevaluate these norms. The clinical history on all dogs receiving an abdominal ultrasound examination was evaluated for signs of gastrointestinal disease. Those without clinical signs were entered into this study. The documentation of body weight, breed, jejunal thickness, and duodenal thickness was made in 231 dogs. Dogs were placed into five groups based on their weight. Sixty-nine breeds were represented with weight ranging from 2.1 to 64 kg. A statistically significant (P < or = 0.05) correlation between body weight and both jejunal and duodenal thickness was observed. We also found that the maximum thickness in both jejunum and duodenum in healthy dogs was larger than previously reported. These data indicate norms for the jejunum of < or = 4.1 mm for dogs up to 20 kg, < or = 4.4 mm for dogs between 20 and 39.9 kg, and < or = 4.7 mm for dogs over 40 kg. The data indicate norms for the duodenum < or = 5.1 mm for dogs up to 20 kg, < or = 5.3 kg for dogs between 20 and 29.9 kg, and < or = 6.0 mm for dogs over 30 kg.     

Captopril Provides Sustained Hemodynamic Benefits in Dogs with Experimentally Induced Mitral Regurgitation

Mitral regurgitation was created surgically in 10 dogs. After measurement of baseline hemodynamic parameters on day 2, treatment with captopril (2 mg/kg orally 3 times daily) was begun in five dogs. Five control dogs received no therapy during the study. The hemodynamic parameters were measured again at weeks 6 and 22. In the treated dogs, the forward ejection fraction (FEF) increased slightly and the total peripheral resistance index (TPRI) decreased. In the controls, the FEF decreased and the TPRI increased. Changes in FEF and TPRI were significantly different between the two groups. The change in FEF correlated significantly with the change in TPRI in both groups. Although the most dramatic changes were observed at week 6, the differences persisted throughout the study. Captopril administration resulted in sustained hemodynamic improvement and may, therefore, delay the onset of congestive heart failure in dogs with mitral regurgitation.     

STANDING MYELOGRAPHY IN SIX ADULT HORSES

Standing myelography was conducted in six neurologically normal adult horses. Myelograms were performed without general anesthesia or tranquilization. Four horses were premedicated orally with 2.2 milligrams/kilogram (mg/kg) of phenobarbital 16 hours and 4 hours prior to myelography to raise their seizure threshold. One-hundred milliters (ml) of cerebral spinal fluid (CSF) was withdrawn from the lumbosacral space prior to injection. Approximately 100 ml of technical grade metrizamide * was injected into the subarachnoid space via a lumbosacral tap. After injection the horse's head was lowered for approximately 10 minutes to facilitate cranial movement of the metrizamide. Lateral cervical radiographs were taken in a standing position. Filling of the subarachnoid space in the cranial cervical region was good to excellent in five horses. In one horse there was poor definition of the cranial cervical region. There was good to excellent filling of the subaranoid space in the caudal cervical region in all six horses. Reactions to metrizamide injection varied. The most severe reaction was generalized seizure.     

The incidence of bone lesions in the carpal and tarsal regions and the rate of physeal closure in weanling quarter horses

Sixty weanlings were maintained in dry lots without forced exercise and individually fed a diet consisting of 25% Bermudagrass hay and 75% balanced concentrate twice dally. Radiographs of the carpus, metacarpus and first phalanx, and other radiographs of the tarsal region, were taken initially at approximately 180 d of age and at approximately 236, 292 and 348 d of age. The radiographs were evaluated for the presence or absence of subchondral and/or cystic lesions in the carpal and tarsal regions and for closure of physes of the distal third metacarpus and proximal first phalanx. Physeal scores were: 1 = open; 2 -- partially closed; 3 = closed. Only 1.7% of the horses had subehondral lesions in the carpal region at 180 d, and none had those lesions at 236, 292 or 348 d. There was a 3.3% incidence of subchondral lesions of the tarsus at 180, 236 and 292 d, but only 1.7% at 348 d. Cystic lesions of the carpus were evident in 13.3% of the horses at 180 d, 16.7% at 236 d and 18.3% at 292 and 348 d. None of the hrses had cystic lesions oftbe tarsus at 180, 236 or 348 d, but 1.7% had them at 292 d. Physeal closure scores for the distal metacarpus averaged 1.5 and 2.6 at 180 and 236 d, respectively. At 292 and 348 d, all of the distal metacarpi were closed. Physeal closure scores for the proximal first phalanges were 1.5, 2.6 and 2.9 at 180,     

Depigmentation — copper supplement therapy a case report

A young Arabian horse showing depigmentation characteristics of “Arabian Fading Syndrome” was treated with 0.6 grams/day orally of a chelated copper supplement. After several months, repigmentation had begun and was proceeding at a satisfactory level. The copper supplementation was discontinued for several months during which time depigmentation began to reoccur. Copper supplementation again was given and brought about repigmentation.