Search Results

You are looking at 1 - 10 of 12 items for

  • Author or Editor: Theresia F. Licka x
  • Refine by Access: All Content x
Clear All Modify Search

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)

Full access
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)

Full access
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)

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To identify and measure radiolucencies at the solear margin of the distal phalanx in radiographs of healthy and laminitic hooves.

SAMPLE

Clinical records and dorsoproximal-palmarodistal radiographs of equine forelimbs with radiological diagnoses of either laminitis (n = 40, L) or navicular syndrome (n = 40, NS).

METHODS

Outlines of the radiolucent structures at the solar margin were drawn in ImageJ, and a customized novel plugin “Arteries Analyzer/ImageJ” was used for measurements. The diverging radiolucencies outside the terminal arc of the distal phalanx were differentiated as arterial channels (open at the solear margin) and ellipses (closed at the solear margin). Comparisons between L and NS, between distal phalanges with and without ellipses, and of arterial channels and ellipses in areas were compared using Wilcoxon and the Mann-Whitney U tests, respectively. The reliability and repeatability of the method were tested using Friedman’s test.

RESULTS

Fewer arterial channels but more ellipses were identified in L than in NS. In phalanges with ellipses (n = 47), the number of ellipses and the number of arterial channels were negatively correlated (PCC −0.181, P = .224). The number of ellipses correlated positively with the severity of laminitis (PCC 0.495, P < .001; n = 80) and with the degree of rotation of the distal phalanx (PCC 0.392, P < .001; n = 80).

CLINICAL RELEVANCE

The software tool successfully measured arterial channels and ellipses outlined by the evaluators. Results indicate that healthy arteries develop into pathological ellipses in laminitic feet. This may be used to complement the interpretation of radiographs and support clinical decision-making.

Open access
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.

Full access
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.

Full access
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.

Full access
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.

Full access
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.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To identify signs of tissue-specific cortisol activity in samples of suspensory ligament (SL) and neck skin tissue from horses with and without pituitary pars intermedia dysfunction (PPID).

SAMPLE Suspensory ligament and neck skin tissue samples obtained from 26 euthanized horses with and without PPID.

PROCEDURES Tissue samples were collected from 12 horses with and 14 horses without PPID (controls). Two control horses had received treatment with dexamethasone; data from those horses were not used in statistical analyses. The other 12 control horses were classified as old horses (≥ 14 years old) and young horses (≤ 9 years old). Standard histologic staining, staining for proteoglycan accumulation, and immunostaining of SL and neck skin tissue sections for glucocorticoid receptors, insulin, 11β hydroxysteroid dehydrogenase type 1, and 11β hydroxysteroid dehydrogenase type 2 were performed. Findings for horses with PPID were compared with findings for young and old horses without PPID.

RESULTS Compared with findings for old and young control horses, there were significantly more cells stained for glucocorticoid receptors in SL samples and for 11 β hydroxysteroid dehydrogenase type 1 in SL and skin tissue samples from horses with PPID. Insulin could not be detected in any of the SL or skin tissue samples. Horses with PPID had evidence of SL degeneration with significantly increased proteoglycan accumulation. Neck skin tissue was found to be significantly thinner in PPID-affected horses than in young control horses.

CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that tissue-specific dysregulation of cortisol metabolism may contribute to the SL degeneration associated with PPID in horses.

Full access
in American Journal of Veterinary Research