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  • Author or Editor: Theresia F. Licka x
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Abstract

Objective—To evaluate an adaptive-filter method for use in analysis of periodic electromyography (EMG) signals in which the transfer function of the filter is matched to characteristics of the signal.

Animals—15 adult horses without clinical signs of back pain.

Procedure—Electromyography signals of the left and right longissimus dorsi muscles, middle gluteal muscles, and triceps brachii muscle were recorded from horses walking on a treadmill, using bilaterally placed surface electrodes. A reflective marker was placed on the hoof of the left hind limb for simultaneous kinematic measurement of motion cycles. Absolute value of the measured EMG signal was convoluted by use of a filter signal equivalent to the length of 3 motion cycles. The signal-to-noise ratio (SNR) was calculated from the autocorrelation function and compared with the SNR of the unfiltered and the low-pass filtered signals.

Results—The signal-adapted filter significantly increased SNR (by 7.3 dB, compared with the lowpass filter, and by 11.1 dB, compared with the unfiltered EMG signal).

Conclusions and Clinical Relevance—The signal adapted filter eliminates signal parts that are not correlated to periodic motion. The method reported here improves the applicability of periodic EMG signals as a clinical tool. (Am J Vet Res 2001;62:1687–1689)

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in American Journal of Veterinary Research

Abstract

Objective—To evaluate back movement during walking in horses.

Animals—22 adult horses with no history or signs of back pain.

Procedure—3-dimensional movements of markers on the hooves, head, and back were measured with a motion analysis system while the horses were walking on a treadmill. The positions of markers on the hooves, head, and the skin above the spinous processes of T5, T10, T16, L3, and 2 sacral vertebrae were recorded. From a minimum of 6 walking motion cycles/horse, marker movement and the time of occurrence of minimum and maximum marker positions within the motion cycle were determined. Angles were calculated between the markers on the head, T16, and S4 or S5 and between the markers on T5, T16, and S4 or S5.

Results—Lateral back movement was maximal at L3, where it reached (mean ± SD) 3.5 ± 0.8% of the horses' height at the withers. Maximum dorsoventral back movement was found at the sacrum, where it reached 4.7 ± 1.3% of the height at the withers. In the horizontal plane, the angle between T5, T16, and S4 or S5 was altered by 11 ± 2.5° during the motion cycle. In the sagittal plane, the angle between the head, T16, and S4 or S5 was altered by 7 ± 3°.

Conclusions and Clinical Relevance—Results of this study may be used as basic kinematic reference data for evaluation of back movement in horses. (Am J Vet Res 2001;62:1173–1179)

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in American Journal of Veterinary Research

Abstract

Objective—To use electromyography (EMG) to measure physiologic activity of the longissimus dorsi muscles of horses during trotting on a treadmill.

Animals—15 adult horses (5 to 20 years old that weighed 450 to 700 kg) that did not have clinical signs of back pain.

Procedure—Data were recorded for each horse during trotting on a treadmill at speeds of 2.6 to 4.4 m/s. Surface electromyography was recorded bilaterally from the longissimus dorsi muscles at the levels of T12, T16, and L3.

Results—In each motion cycle, 2 EMG maxima were found at the end of the diagonal stance phases. The EMG activity peaked slightly later at L3 than at T12 and T16. Maximum EMG amplitudes were highest at T12 and decreased caudally, with mean ± SD values of 4.51 ± 1.20 mV at T12, 3.00 ± 0.83 mV at T16, and 1.78 ± 0.67 mV at L3. Mean minimum EMG activity was 1.30 ± 0.63 mV at T12, 0.83 ± 0.35 mV at T16, and 0.80 ± 0.39 mV at L3. The relative amplitudes (ie, [maximum – minimum]/maximum) were 67 ± 11% at T12, 66 ± 8% at T16, and 71 ± 8% at L3.

Conclusions and Clinical Relevance—Activity of the longissimus dorsi muscles is mainly responsible for stabilization of the vertebral column against dynamic forces. The difference between minimum and maximum activity may allow application of this method as a clinical tool. Data reported here can serve as reference values for comparison with values from clinically affected horses. (Am J Vet Res 2004;65:155–158)

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in American Journal of Veterinary Research

Abstract

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° 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.

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in American Journal of Veterinary Research

Abstract

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 × 10−6 ± 8.9 × 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 ≤ 10 hours without structural damage to the laminar tissue.

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in American Journal of Veterinary Research

Abstract

Objective—To examine the effect of endotoxins on metabolism and histopathologic changes of isolated perfused equine forelimbs.

Sample—Forelimbs (comprising the metacarpus and digit) were collected from cadavers of 12 healthy adult horses after slaughter at an abattoir (14 limbs; 1 forelimb of 10 horses and both forelimbs of 2 horses).

Procedures—Forelimbs were perfused for 10 hours with autologous blood, with and without the addition of endotoxin (80 ng of lipopolysaccharide [LPS]/L). Two limbs of the endotoxin exposure group and 2 nonperfused limbs were loaded to failure of the suspensory apparatus of the pedal bone to evaluate the effect of body weight. Metabolic and histologic variables were evaluated.

Results—Blood pressure increased during the first hour and did not differ between groups. Lactate dehydrogenase activity was similar in both groups and increased significantly during the 10-hour period; glucose consumption at 5 hours and lactate concentration at 8 hours were significantly higher in limbs exposed to endotoxin. The width of secondary epidermal lamellae was greater in LPS limbs. In the primary dermal lamellae of LPS limbs, there were significantly more vessels with an open lumen and aggregates of intravascular neutrophils.

Conclusions and Clinical Relevance—In the blood-perfused isolated forelimbs of equine cadavers, exposure to LPS led to significant changes in the laminar tissue as well as to metabolic changes. Therefore, endotoxin should be considered as a causative factor for laminitis and not merely as a risk factor.

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in American Journal of Veterinary Research

Abstract

Objective—To determine the effect of short-term hyperinsulinemia on the localization and expression of endothelin receptor (ETR)-A and ETR-B in lamellar tissue of the forelimbs of horses.

Samples—Distal portion of 15 cadaveric forelimbs from healthy adult horses (1 limb/horse) obtained immediately after slaughter at an abattoir.

Procedures—Each forelimb was assigned to 1 of 3 treatment groups (perfused with autologous blood for 10 hours [control perfusion; n = 5], perfused with an insulin [142 ± 81 μU/mL] perfusate for 10 hours [insulinemic perfusion; 5], or not perfused [unperfused control; 5]). Immunohistochemical evaluation of lamellar tissue was performed to assess localization of ETR-A and ETR-B. Expression of ETR-A and ETR-B was measured semiquantitatively on a scale of 0 to 3 (0 = none, 1 = mild, 2 = moderate, and 3 = high-intensity staining) and quantitatively by means of gray value analysis with imaging software.

Results—In all specimens, ETR-A and ETR-B were localized in endothelium, smooth muscle cells, axons, and keratinocytes. Quantitative expression of ETR-A in the midportion of the primary epidermal lamellae for the insulinemic perfusion group (149 ± 16) was lower than that for the control perfusion group (158 ± 15). Expression of ETR-B in the primary epidermal lamellae tips for the insulinemic perfusion group (140 ± 29) was higher than that for the control perfusion group (114 ± 8).

Conclusions and Clinical Relevance—Hyperinsulinemia caused significant changes in endothelin receptor expression, which suggested that ETR antagonists might be beneficial for treatment of laminitis in horses.

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in American Journal of Veterinary Research

Abstract

Objective—To assess differences in activities of back and pelvic limb muscles by use of surface electromyography (SEMG) in chronically lame and nonlame horses during walking and trotting.

Animals—12 nonlame horses and 12 horses with unilateral chronic mild to moderate pelvic limb lameness.

Procedures—On each horse, bipolar electrodes were attached to the skin over the midpoints of the right and left longissimus thoracis (Lot), semitendinosus (Set), biceps femoris (Bif), gluteus medius (Glm), and extensor digitorum longus (Edl) muscles. For each muscle, synchronous kinematic and SEMG recordings were made during walking and trotting on a treadmill; mean, maximum, and minimum muscle activities and maximum-to-mean and minimum-to-mean activity ratios were determined. For each lame or nonlame horse, data from both pelvic limbs were averaged; in lame horses, data from the nonlame and lame pelvic limbs were also examined separately (NL-L and L-L values, respectively). Comparisons were made among the 4 data sets and between gaits.

Results—During walking, the NL-L maximum-to-mean ratios for Bif and Glm muscles were significantly greater and in lame horses, L-L and NL-L minimum-to-mean ratios for Set, Bif, Glm, and Lot muscles were significantly less than those for nonlame horses. During trotting, minimum-to-mean ratios for Set, Glm, and Lot muscles in lame horses were significantly lower than those for nonlame horses. Activity of the Edl muscle was not affected by lameness.

Conclusions and Clinical Relevance—In lame horses, variation in muscle use was detectable via SEMG. In chronically lame horses, back and pelvic limb muscle activities were affected differently during walking and trotting.

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in American Journal of Veterinary Research

Abstract

Objective—To investigate effects of endotoxin on leukocyte activation and infiltration of the laminar tissue in isolated perfused equine limbs.

Sample—10 right forelimbs and 3 left forelimbs collected from 10 healthy adult horses after slaughter at a licensed abattoir.

Procedures—Isolated right forelimbs were randomly assigned to 2 groups (5 forelimbs/group): perfusion of the distal portion for 10 hours with 80 ng of endotoxin/L and perfusion under the same conditions without endotoxin. After perfusion, samples for immunohistochemical detection of leukocytes (by use of antibodies against calprotectin and myeloperoxidase) and transmission electron microscopy were collected from the laminar tissue of the dorsal aspect of the hooves. Additionally, control samples were collected from the 3 nonperfused left forelimbs.

Results—Samples of laminar tissue from the endotoxin perfusion group had significantly higher scores for calprotectin and myeloperoxidase staining than did control samples and samples perfused without endotoxin. Ultrastructural examination revealed endotoxin-induced damage of the epidermal basal cells with loss of cell contacts including hemidesmosomes and anchoring filaments and a resulting separation of parts of the basement membrane. Additionally, local breakdown of the basement membrane was detected at the location of leukocyte adherence.

Conclusions and Clinical Relevance—In isolated perfused equine limbs, endotoxin at a clinically relevant concentration induced a distinct inflammatory reaction with intravascular and extravascular accumulation of leukocytes in the laminar tissue, similar to that seen during the developmental phase of laminitis. Therefore, endotoxin should be considered as a causative factor for some types of laminitis.

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in American Journal of Veterinary Research

Abstract

OBJECTIVE To investigate the effect of lipopolysaccharide (LPS) on type VII collagen– cleaving matrix metalloproteinases (MMPs) in the lamellar tissue of extracorporeally perfused equine limbs.

SAMPLE 10 right forelimbs and 3 left forelimbs collected from 10 adult horses after slaughter at a licensed abattoir.

PROCEDURES Extracorporeal perfusion of the isolated equine limbs was performed for 10 hours under physiologic conditions (control-perfused limbs; n = 5) and with the addition of 80 ng of LPS/L of perfusate (LPS-perfused limbs; 5). Lamellar tissue specimens were then collected from the dorsal aspect of the hooves. Additionally, corresponding control specimens were collected from the 3 nonperfused left forelimbs. Immunohistochemical analysis was performed on paraffin-embedded tissue blocks with antibodies against total (latent and active) MMP-1, MMP-2, MMP-8, and MMP-9 as well as antibody against active MMP-9. Intensity of immunohistochemical staining was scored, and stain distribution in the lamellar tissue was noted.

RESULTS Staining intensity of total and active MMP-9 was significantly increased in LPS-perfused versus control-perfused limbs. No such difference was identified for MMP-1, MMP-2, and MMP-8.

CONCLUSIONS AND CLINICAL RELEVANCE Of the 4 MMPs that are capable of degrading type VII collagen, MMP-9 was the only one for which production increased in the lamellar tissue of isolated equine limbs perfused with versus without a clinically relevant concentration of LPS. These results suggested that MMP-9 may be involved in initiation of pathological changes in lamellar tissue in endotoxin-induced laminitis, whereas MMP-1, MMP-2, and MMP-8 may be less relevant.

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in American Journal of Veterinary Research