Effects of long-term extracorporeal blood perfusion of the distal portion of isolated equine forelimbs on metabolic variables and morphology of laminar tissue.

OBJECTIVE: To establish an ex vivo model of blood perfusion in the distal portion of isolated equine forelimbs that closely represents the in vivo situation in the laminar tissue of the hoof. SAMPLE POPULATION: 18 forelimbs collected from 9 healthy adult horses following slaughter at a licensed abattoir. PROCEDURES: The distal portion of isolated equine forelimbs from 9 horses were perfused under physiologic conditions over a period of 6, 8, and 10 hours with autologous blood. To determine cell viability in perfused tissues, indicators for metabolism (lactate generation and glucose and oxygen consumption) as well as indicators for cell damage (potassium concentration and lactate dehydrogenase activity) were examined at 1-hour intervals from samples of the perfusate. Weight gain in the forelimb was used to determine the edema index. After perfusion, light and electron microscopic examinations of laminar tissue specimens were performed. RESULTS: During hemoperfusion of the isolated forelimbs, mean +/- SD glucose consumption was 197.4 +/- 65.1 mg/h, lactate generation was 1.84 +/- 0.79 mmol/h, and oxygen consumption was 6.4 x 10(-6) +/- 8.9 x 10(-5) mL.g(-1).min(-1). Neither an efflux of potassium into the perfusate nor a relevant increase of the lactate dehydrogenase activity was detected, indicating low amounts of cellular damage in the perfused tissues. Weight gain of forelimbs was 1.02 +/- 0.95%. Histologic and ultrastructural appearance of the laminar tissue revealed no signs of tissue damage. CONCLUSIONS AND CLINICAL RELEVANCE: Isolated equine limbs were perfused under physiologic conditions over a period of < or = 10 hours without structural damage to the laminar tissue.

Dorsolateral approach for arthrocentesis of the centrodistal joint in horses.

OBJECTIVE: To develop a dorsolateral approach to the centrodistal (distal intertarsal) joint in horses and compare its success rate with that of the traditional medial approach in that joint. SAMPLE POPULATION: 25 cadaveric equine hind limbs, ultrasonographic images, and radiographic views of the tarsal region of 5 and 59 healthy horses, respectively, and 22 horses with a clinical indication for centrodistal joint centesis. PROCEDURES: The dorsolateral approach was established anatomically (3 cadaveric limbs), ultrasonographically (5 horses), and radiographically (59 horses). Centrodistal joint arthrocentesis was performed in 22 cadaveric hind limbs and 22 horses; the number of needle repositionings required for procedure completion via the medial (in vitro) and the dorsolateral approach (in vitro and in vivo) was determined. RESULTS: For the dorsolateral approach to the centrodistal joint, the injection site was 2 to 3 mm lateral to the long digital extensor tendon and 6 to 8 mm proximal to a line drawn perpendicular to the axis of the third metatarsal bone through the proximal end of the fourth metatarsal bone. The needle was directed plantaromedially (angle of approx 70 degrees from the sagittal plane). The number of needle repositionings required to complete centrodistal joint centesis via the dorsolateral and medial approaches was not significantly different. CONCLUSION AND CLINICAL RELEVANCE: In a clinical setting, the dorsolateral approach to the centrodistal joint in horses appears to have some advantages over the traditional medial approach. The success rate of arthrocentesis was similar via either approach, and palpation of the anatomic landmarks was easy.

Method for preparing thin sections of untreated equine hoof horn for electron microscopic examination.

The preparation of hard tissues such as the equine hoof horn for electron microscopic examination is very difficult. In particular the penetration of fixatives and chemicals used during fixation and embedding is a problem. The objective of this study was to find and implement an alternative method enabling the preparation of high-quality thin sections of hoof horn and other hard tissue, which maintains the hard tissue ultrastructure and can be used for immuno-labeling. Compared to commonly used fixation and embedding techniques, the preparation of thin sections from untreated material method saves time and material and provides equivalent ultrastructural information. Furthermore, thin sections from untreated material are significantly larger and more homogeneous, more resistant to the electron ray, as well as more suitable for sectioning. The electron microscopical pictures obtained allow a comparison to previous test results achieved with fixed and embedded material. Using the preparation of thin sections from untreated material method, fixation and embedding artifacts are avoided, providing a clearer interpretation of the electron microscopical findings. Considerable advantages are achieved by using immunohistochemical techniques with untreated horn specimens because fixation invariably decreases antigenicity.