Evaluation of delayed-image bone scintigraphy to assess bone formation after distraction osteogenesis in dogs

OBJECTIVE: To quantitatively assess distraction-induced bone formation in a crural lengthening model in dogs by use of delayed-image bone scintigraphy. ANIMALS: 12 mature Labrador Retrievers. PROCEDURE: Dogs were randomly allocated to 1 of 3 groups. A circular external skeletal fixation system was mounted on the right crus of each dog. Osteotomy of the distal portion of the tibia and fibula was performed in groups 1 and 2 and was followed by a lengthening procedure of 10 mm in the first group only. The third group served as sham-operated controls. Delayed-image bone scintigraphy with technetium-99m hydroxy methylene diphosphonate was performed 2, 4, and 6 weeks after surgery. Delayed-image-to-region-of-interest, delayed-image-to-crural, and delayed-image-to-femoral scintigraphic activity ratios were calculated. New bone formation was quantified by use of densitometric image analysis, and values for the scintigraphic ratios were compared. RESULTS: In the distraction and osteotomy groups, delayed-image-to-region-of-interest and delayed-image-to-crural ratios increased significantly. Although densitometric image analysis revealed increased bone formation after distraction, the region-of-interest ratios and crural ratios were similar in both groups. All dogs had increased delayed-image-to-femoral ratios. CONCLUSIONS AND CLINICAL RELEVANCE: Delayed-image bone scintigraphy ratios were not effective at differentiating between the amounts of distraction-induced bone and osteotomy-induced bone. Metabolic bone activity in the adjacent femur was increased as a consequence of circular external skeletal fixator placement. Delayed-image bone scintigraphy was not adequately sensitive to quantitatively monitor bone formation but may be useful as an early predictor of bone healing.     

Intraobserver and interobserver repeatability of ocular biometric measurements obtained by means of B-mode ultrasonography in dogs

OBJECTIVE: To assess intra- and interobserver repeatability of ocular biometric measurements obtained by means of high-resolution B-mode ultrasonography in dogs. Animals-6 Beagles without ocular abnormalities. PROCEDURES: B-mode ultrasonography was performed bilaterally with a 10.5-MHz broadband compact linear array transducer. All measurements were made on 2 different occasions by 2 observers. The Bland-Altman method was used to assess agreement between measurements obtained by the 2 observers and between the 2 sets of measurements obtained by each observer. RESULTS: Intra- and interobserver repeatability was highest for larger measurements, such as depth of the eye and depth of the anterior chamber. When repeatability was examined, bias was significantly different from 0 for only a few measurements, but the percentage difference between observations was as high as 180% for some measurements. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that most measurements of intraocular distances and structures obtained by means of high-resolution B-mode ultrasonography have acceptable intra- and interobserver repeatability. However, the percentage difference between observations can be high for smaller measurements.     

Force plate analysis before and after dorsal decompression for treatment of degenerative lumbosacral stenosis in dogs

OBJECTIVE: Using force plate analysis (FPA), determine ground reaction forces in dogs with degenerative lumbosacral stenosis (DLS) and evaluate the effects of lumbosacral decompressive surgery. STUDY DESIGN: Prospective clinical study. ANIMALS: Twelve dogs with DLS. METHODS: DLS was diagnosed by clinical signs, radiography, computed tomography, and/or magnetic resonance imaging. FPA was performed before surgery, and 3 days, 6 weeks, and 6 months after surgery. The mean peak braking (Fy+), peak propulsive (Fy-), and peak vertical (Fz+) forces of 8 consecutive strides were determined. The ratio between the total Fy- of the pelvic limbs and the total Fy- of the thoracic limbs (P/TFy-), reflecting the distribution of Fy-, was analyzed to evaluate any changes in locomotion pattern postoperatively. Ground reaction force data for DLS dogs were compared with data derived from 24 healthy dogs (control). RESULTS: In dogs with DLS, the propulsive forces (Fy-) of the pelvic limbs were significantly smaller than those of controls. P/TFy- was significantly smaller in dogs with DLS than in control dogs, and increased during the follow-up period, reaching normal values 6 months after surgery. CONCLUSIONS: Cauda equina compression in dogs with DLS decreases the propulsive force of the pelvic limbs and surgical treatment restores the propulsive force of the pelvic limbs in a 6-month period. CLINICAL RELEVANCE: In dogs with DLS, FPA is an effective method in evaluating the response to surgical treatment. Normal propulsive force in the pelvic limbs was restored during 6 months after decompressive surgery.     

Development of a murine ocular posterior segment explant culture for the study of intravitreous vector delivery

The objective of this study was to develop a murine retinal/choroidal/scleral explant culture system to facilitate the intravitreous delivery of vectors. Posterior segment explants from adult mice of 2 different age groups (4 wk and 15 wk) were cultured in serum-free medium for variable time periods. Tissue viability was assessed by gross morphology, cell survival quantification, activated caspase-3 expression, and immunohistochemistry. To model ocular gene therapy, explants were exposed to varying transducing units of a lentiviral vector expressing the gene for green fluorescent protein for 48 h. Explant retinal cells remained viable for approximately 1 wk, although the ganglion cell layer developed apoptosis between 4 and 7 d. Following vector infusion into the posterior segment cups, viral transduction was noted in multiple retinal layers in both age groups. An age of donor mouse influence was noted and older mice did not transduce as well as younger mice. This explant offers an easily managed posterior segment ocular culture with minimum disturbance of the tissue, and may be useful for investigating methods of enhancing retinal gene therapy under controlled conditions.     

Preliminary investigation of concurrent administration of phenylbutazone and romifidine in healthy horses

ObjectiveTo characterize the cardiorespiratory and electrocardiographic effects of the combined administration of phenylbutazone and romifidine.Study designProspective four-period, four-treatment, blinded, randomized, crossover trial.AnimalsFive, healthy, mixed breed horses.MethodsPrior to treatment administration, a catheter was introduced into the intra-thoracic cranial vena cava via the jugular vein and a subcutaneously located carotid artery was catheterised. All treatments were administered intravenously (IV) and consisted of saline placebo (PLC), phenylbutazone (PBZ, 4.4 mg kg^?1) romifidine (ROM, 80 μg kg^?1) and a combination of phenylbutazone (4.4 mg kg^?1) and romifidine (80 μg kg^?1). There was at least a 1 week washout period between treatments. Heart rate (HR), respiratory rate (f_R), systolic (SAP), diastolic (DAP) and mean (MAP) arterial pressures and central venous pressure (CVP) were recorded for baseline (prior to drug administration) and at 5 minute intervals thereafter for 30 minutes. Electrocardiographic abnormalities were recorded. Data were analyzed by anova.ResultsFor the cardiovascular variables there were no statistically significant (p > 0.05) differences between horses treated with ROM and PBZ_ROM. Statistically significant (p < 0.05) differences only occurred between treatments with romifidine (ROM and PBZ_ROM) and without romifidine (PLC and PBZ). Within treatments, for ROM, changes over time were statistically significant (p < 0.05) for HR, SAP, DAP, MAP and CVP. For PBZ_ROM, changes over time were statistically significant (p < 0.05) for CVP. Sino-atrial and atrio-ventricular blocks occurred in horses treated with ROM and PBZ_ROM.Conclusions and clinical relevanceThe combined IV administration of phenylbutazone and romifidine had no statistically significant effect on cardiorespiratory variables. These limited data suggest no evidence why both agents should not be included in a preoperative medication protocol for healthy horses but do not exclude the possibility of interactions occurring in a larger population.     

High pressure processing treatment prevents embryonation of eggs of Trichuris vulpis and Ascaris suum and induces delay in development of eggs

High hydrostatic pressure processing (HPP) is an effective non-thermal treatment used to inactivate pathogens from a variety of food and food products. It has been extensively examined using prokaryotic organisms and protozoan's but has had limited study on metazoans. Treatment using HPP has been shown to be effective in inactivating nematode larvae in food and preventing embryonation of Ascaris suum eggs. We conducted experiments using eggs of the canine whipworm Trichuris vulpis collected from naturally infected dogs and A. suum eggs from naturally infected pigs. We observed a delay in development of eggs of T. vulpis in a preliminary experiment and conducted 2 experiments to test the hypothesis that appropriate HPP levels can induce a delay in embryonation of nematode eggs. In experiment 1, nonembryonated T. vulpis eggs in tap water were packaged in sealable bags and exposed to 138-600 megapascals (MPa; 1 MPa=10 atm=147 psi) for 60s in a commercial HPP unit. In a second experiment, nonembryonated eggs of A. suum were exposed to 138-600 MPa and treated for 60s in the same commercial HPP unit. Embyronation of T. vulpis eggs was delayed by 4 and 5 days for eggs treated with 207 and 241 MPa but eventually eggs developed and the numbers of embryonated eggs was similar to controls on day 55. Embryonation of T. vulpis eggs treated with 345 or 350 MPa was delayed by 9 days and never reached more than 5% of eggs embryonated. On day 55 post treatment, 95% of control nontreated T. vulpis eggs were embryonated, 100-65% of eggs treated with 138-276 MPa were embryonated, a maximum of 5% of eggs treated with 345-350 MPa were embryonated, and 0% of eggs treated with ≥ 400 MPa were embryonated. T. vulpis eggs treated with ≥ 400 MPa did not undergo cell division. Embryrnation of A. suum eggs was delayed by 4, 10, and 16 days for eggs treated with 207, 241, and 250MPa, respectively, compared to nontreated control eggs. A. suum eggs treated with 207 MPa eventually embryonated to similar % embryonation values as controls and 138 MPa treated eggs but eggs treated with 241 or 250 MPa were always <5% embryonated. A. suum eggs treated with ≥ 300 MPa did not undergo cell division. On the final day of examination at day 56 after treatment, the % of embryonated eggs was 92% nontreated controls, 94% treated with 138 MPa, 84% treated with 207 MPa, 2% treated with 241 or 250 MPa, and 0% treated with 276, 200, 345, 400, or 414 MPa, respectively.     

Effects of diet restriction on life span and age-related changes in dogs

OBJECTIVE: To evaluate the effects of 25% diet restriction on life span of dogs and on markers of aging. DESIGN: Paired feeding study. ANIMALS: 48 Labrador Retrievers. PROCEDURES: Dogs were paired, and 1 dog in each pair was fed 25% less food than its pair-mate from 8 weeks of age until death. Serum biochemical analyses were performed, body condition was scored, and body composition was measured annually until 12 years of age. Age at onset of chronic disease and median (age when 50% of the dogs were deceased) and maximum (age when 90% of the dogs were deceased) life spans were evaluated. RESULTS: Compared with control dogs, food-restricted dogs weighed less and had lower body fat content and lower serum triglycerides, triiodothyronine, insulin, and glucose concentrations. Median life span was significantly longer for dogs in which food was restricted. The onset of clinical signs of chronic disease generally was delayed for food-restricted dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that 25% restriction in food intake increased median life span and delayed the onset of signs of chronic disease in these dogs.