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Abstract

CASE DESCRIPTION A 15-year-old neutered female mixed-breed dog (dog 1) and an 11-year-old neutered female Labrador Retriever (dog 2) were examined because of unilateral exophthalmus, third eyelid protrusion, and periorbital swelling that failed to respond to antimicrobial treatment.

CLINICAL FINDINGS Both dogs underwent ultrasonographic, CT, and MRI examination of the head. In both dogs, advanced imaging revealed a poorly defined, peripherally contrast-enhancing, mucous-filled cystic mass that radiated from the temporomandibular joint and infiltrated the periorbital tissues and retrobulbar space. Both dogs underwent surgical biopsy of the periorbital mass. A viscous, straw-colored fluid was aspirated from the retrobulbar region in both dogs. The initial histologic diagnosis for dog 1 was zygomatic sialadenitis and sialocele. However, the clinical signs recurred, and histologic examination of specimens obtained during a second surgical biopsy resulted in a diagnosis of myxoma. The histologic diagnosis was myxosarcoma for dog 2.

TREATMENT AND OUTCOME In both dogs, clinical signs recurred within 2 weeks after surgery and persisted for the duration of their lives. Dog 1 received no further treatment after the second surgery and was euthanized 34 months after initial examination because of multicentric lymphoma. Dog 2 was treated with various chemotherapy agents and was euthanized 11 months after initial examination because of a dramatic increase in periocular swelling and respiratory stertor.

CLINICAL RELEVANCE Temporomandibular myxomatous neoplasia can be confused with zygomatic sialocele on the basis of clinical signs but has characteristic MRI features. Representative biopsy specimens should be obtained from areas close to the temporomandibular joint to avoid misdiagnosis.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate the short-term effects of 4 therapeutic shoeing systems on lameness and voluntary limb-load distribution in horses with chronic laminitis.

Animals—10 horses with chronic laminitis.

Procedures—A clinical trial was conducted that used a concurrent control, crossover design to evaluate the relative effectiveness of a standard flat shoe, fullered egg-bar shoe, heart-bar shoe, and modified equine digital support system to alleviate chronic lameness in horses. Therapeutic success was assessed during a 7-day period by use of subjective (Obel grade and clinical score) and objective (forceplate data) evaluations.

Results—Comparison of pretreatment and intertreatment control data indicated that disease status of the horses did not change during the course of the study. None of the therapeutic shoeing treatments used resulted in a significant change in severity of lameness.

Conclusions and Clinical Relevance—Results were interpreted to imply that substantial clinical improvement should not be expected during the first 7 days after therapeutic shoeing for the specific shoes tested in this study. On the basis of our results, we hypothesize that when used as the lone indicator of therapeutic success, severity of lameness may not be a valid indicator. (Am J Vet Res 2002;63:1629–1633)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether solar load distribution pattern on a solid nondeformable ground surface is the product of contact erosion and is the mirror image of load distribution on a deformable surface in horses.

Animals—30 clinically normal horses.

Procedures—Solar load distribution was compared among 25 clinically normal horses during quasistatic loading on a solid nondeformable surface and on a highly deformable surface. Changes in solar load distribution patterns were evaluated in 5 previously pasture- maintained horses housed on a flat nondeformable surface. Changes in solar load distribution created by traditional trimming and shoeing were recorded.

Results—Unshod untrimmed horses had a 4-point (12/25, 48%) or a 3-point (13/25, 52%) wall load distribution pattern on a flat solid surface. Load distribution on a deformable ground surface was principally solar and located transversely across the central region of the foot. Ground surface contact areas on solid (24.2 ± 8.62 cm2) and deformable (69.4 ± 22.55 cm2) surfaces were significantly different. Maintaining unshod horses on a flat nondeformable surface resulted in a loss of the 3- and 4-point loading pattern and an increase in ground surface contact area (17.9 ± 2.77 to 39.9 ± 12.77 cm2). Trimming increased ground surface contact area (24.2 ± 8.60 to 45.7 ± 14.89 cm2).

Conclusion and Clinical Relevance—In horses, the solar surface is the primary weight-loading surface, and deformability of ground surface may have a role in foot expansion during loading. Increased surface area induced by loading on deformable surfaces, trimming, and shoeing protects the foot. (Am J Vet Res 2001;62:895–900)

Full access
in American Journal of Veterinary Research

Abstract

Case Description—A 10-year-old sexually intact female dog was examined because of a static, well-circumscribed subcutaneous mass and associated fistulous draining tract located along the right ventrolateral aspect of the thoracic body wall of 15 months' duration.

Clinical Findings—Results of computed tomography and fistulography confirmed the presence of the fistulous tract. Computed tomography also revealed a focal, hypodense region in the right ventral portion of the liver that was adjacent to but not clearly associated with the fistulous tract.

Treatment and Outcome—Surgical exploration of the tract revealed that it passed into the right hemithorax to the diaphragm; entered the right medial lobe of the liver; and terminated in a well-encapsulated, cystic liver lesion. The right medial liver lobe and all affected tissues were removed. Histologically, the liver lesion consisted of a fibrotic, dilated bile duct. The dilated bile duct and fistula were lined with biliary epithelium. On the basis of these findings, a diagnosis of spontaneous external biliary fistula was made. Five months after surgery, the dog was clinically normal.

Clinical Relevance—To the authors' knowledge, spontaneous external biliary fistula in a dog has not been reported in the veterinary medical literature. Despite the rarity of this condition, it should be considered in a dog with similar clinical findings. Clinical findings and results of appropriate diagnostic imaging procedures may provide valuable information in making this diagnosis and in planning surgical treatment.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objectives—To compare limb-load distribution between horses with and without acute or chronic laminitis.

Animals—10 horses with carbohydrate-induced acute laminitis, 20 horses with naturally occurring chronic laminitis, and 20 horses without foot abnormalities (controls).

Procedures—Limb-load distribution was determined, using a custom-designed system that allowed simultaneous quantification of the mean percentage of body weight voluntarily placed on each limb (ie, mean limb load) and the SD of the mean load over a 5- minute period (ie, load distribution profile [LDP]). Load distribution profile was used as an index of frequency of load redistribution.

Results—Mean loads on fore- and hind limbs in control horses were 58 and 42%, respectively, and loads were equally and normally distributed between left and right limbs. In addition, forelimb LDP was greater, compared with hind limbs, and was affected by head and neck movement. In comparison, limb-load distribution in horses with chronic laminitis was characterized by an increase in the preferential loading of a forelimb, a decrease in total forelimb load, and an increase in LDP that was correlated with severity of lameness. In horses with carbohydrate-induced acute laminitis, mean limb loads after onset of lameness were not different from those prior to lameness; however, LDP was significantly decreased after onset of lameness.

Conclusion and Clinical Relevance—Quantification of limb-load distribution may be an applicable screening method for detecting acute laminitis, grading severity of lameness, and monitoring rehabilitation of horses with chronic laminitis. (Am J Vet Res 2001; 62:1393–1398)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To investigate the effects of bevacizumab, a human monoclonal antibody against vascular endothelial growth factor, on the angiogenesis and growth of canine osteosarcoma cells xenografted in mice.

Animals—27 athymic nude mice.

Procedures—To each mouse, highly metastasizing parent osteosarcoma cells of canine origin were injected into the left gastrocnemius muscle. Each mouse was then randomly allocated to 1 of 3 treatment groups: high-dose bevacizumab (4 mg/kg, IP), low-dose bevacizumab (2 mg/kg, IP), or control (no treatment). Tumor growth (the number of days required for the tumor to grow from 8 to 13 mm), vasculature, histomorphology, necrosis, and pulmonary metastasis were evaluated.

Results—Mice in the high-dose bevacizumab group had significantly delayed tumor growth (mean ± SD, 13.4 ± 3.8 days; range, 9 to 21 days), compared with that for mice in the low-dose bevacizumab group (mean ± SD, 9.4 ± 1.5 days; range, 7 to 11 days) or control group (mean ± SD, 7. 2 ± 1.5 days; range, 4 to 9 days). Mice in the low-dose bevacizumab group also had significantly delayed tumor growth, compared with that for mice in the control group.

Conclusions and Clinical Relevance—Results indicated that bevacizumab inhibited growth of canine osteosarcoma cells xenografted in mice, which suggested that vascular endothelial growth factor inhibitors may be clinically useful for the treatment of osteosarcoma in dogs.

Impact for Human Medicine—Canine osteosarcoma is used as a research model for human osteosarcoma; therefore, bevacizumab may be clinically beneficial for the treatment of osteosarcoma in humans.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To develop an IM xenograft model of canine osteosarcoma in mice for the purpose of evaluating effects of radiation therapy on tumors.

Animals—27 athymic nude mice.

Procedures—Mice were randomly assigned to 1 of 3 groups of 9 mice each: no treatment (control group), radiation at 10 Gy, or radiation at 15 Gy. Each mouse received 5 × 105 highly metastasizing parent osteosarcoma cells injected into the left gastrocnemius muscle. Maximum tumor diameter was determined with a metric circles template to generate a tumor growth curve. Conscious mice were restrained in customized plastic jigs allowing local tumor irradiation. The behavior and development of the tumor xenograft were assessed via evaluations of the interval required for tumor-bearing limbs to reach diameters of 8 and 13 mm, extent of tumor vasculature, histomorphology of tumors, degree of tumor necrosis, and existence of pulmonary metastasis and clinical disease in affected mice.

Results—Tumor-bearing limbs grew to a diameter of 8 mm (0.2-g tumor mass) in a mean ± SEM interval of 7.0 ± 0.2 days in all mice. Interval to grow from 8 to 13 mm was significantly prolonged for both radiation therapy groups, compared with that of the control group. Histologic evaluation revealed the induced tumors were highly vascular and had characteristics consistent with those of osteosarcoma. Pulmonary metastasis was not detected, and there was no significant difference in percentage of tumor necrosis between groups.

Conclusions and Clinical Relevance—A reliable, repeatable, and easily produced IM xenograft model was developed for in vivo assessment of canine osteosarcoma.

Full access
in American Journal of Veterinary Research