Objective—To describe a single-portal cranial arthroscopic
approach to the stifle joint in horses and to
determine the clinical outcome in horses with
femorotibial joint disease in which this approach was
Animals—23 adult horses.
Procedure—Medical records were reviewed to
obtain information on clinical outcome in horses in
which the single-portal cranial arthroscopic approach
Results—Twenty-nine stifle joints of 23 horses were
examined arthroscopically, using the described
approach. Subchondral bone cysts were treated in 19
medial femoral condyles of 12 horses. Unilateral cruciate
ligament desmitis (4 horses), meniscal tearing
(3), or both (2) were identified in 9 horses. Evidence
of degenerative joint disease without cystic lesions or
soft tissue trauma was found in 2 horses. Information
on clinical outcome was obtained for 21 of 23 horses.
A successful outcome was obtained in 15 of 21 horses
and was defined as return to sound performance
at a degree equal to or better than that prior to injury
and lameness. Eight of 12 horses treated for medial
femoral condylar cysts had a successful outcome.
Four show horses treated for cruciate ligament
lesions alone successfully returned to showing activity.
None of the 3 horses with meniscal tearing were
able to perform successfully.
Conclusions and Clinical Relevance—The
femorotibial joint was evaluated through a single-portal
cranial arthroscopic approach, using the
femoropatellar joint as the point of access. This
approach was easy to perform, allowed controlled
access to the femorotibial joint, avoided accidental
damage to articular structures, and required fewer
access portals. (J Am Vet Med Assoc 2002;220:
Objective—To determine the effects of induction of
capacitative Ca2+ entry on tone in equine laminar arteries
Sample Population—Laminar arteries and veins
from 6 adult mixed-breed horses.
Procedure—Arteries and veins were isolated and
mounted on small vessel myographs for the measurement
of isometric tension. Capacitative Ca2+ entry was
induced by incubating the vessels with the specific
Ca2+-ATPase inhibitor thapsigargin (100nM) in a Ca2+-
free physiologic salt solution. Capacitative Ca2+
entry–associated contractile responses were determined
by the subsequent addition of 2mM Ca2+ to the
solution bathing the vessels; in some experiments,
either the voltage-gated Ca2+ blocker diltiazem (10µM)
or the putative capacitative Ca2+ entry inhibitor trifluoromethylphenylimidazole
(300µM) was added to the
bathing solution 15 minutes prior to a second 2mM
Ca2+ exposure. The Sr2+ permeability of the capacitative
Ca2+ entry pathway in laminar vessels was assessed by
exposing the vessels to 4mM Sr2+ after induction of
capacitative Ca2+ entry with thapsigargin.
Results—Induction of capacitative Ca2+ entry elicited
robust contractile responses in laminar veins but did not
increase tone in laminar arteries. In laminar veins, capacitative
Ca2+ entry–induced contractile responses were unaffected
by preincubation with diltiazem, attenuated by trifluoromethylphenylimidazole,
and were impermeable to Sr2+.
Conclusions and Clinical Relevance—Results indicated
that induction of capacitative Ca2+ entry elicits
vasoconstriction in equine laminar veins but not in
laminar arteries and should therefore be considered a
potential mechanism by which selective venoconstriction
occurs in horses during the development of
acute laminitis. (Am J Vet Res 2005;66:1877–1880)
Objective—To evaluate the safety and efficacy of thoracoscopically
guided pulmonary wedge resection in
Animals—10 horses (5 control horses and 5 horses
affected with recurrent airway obstruction [ie,
Procedure—Each horse underwent a thoracoscopically
guided pulmonary wedge resection. Before, during,
and after surgery, heart rate, respiratory rate,
arterial blood gases, and systemic and pulmonary
arterial pressures were measured. Physical examination,
CBC, and thoracic radiography and ultrasonography
were performed 24 hours before and 2 and 48
hours after surgery. Pulmonary specimens were
assessed by histologic examination. A second thoracoscopic
procedure 14 days later was used to evaluate
the resection site.
Results—The technique provided excellent specimens
for histologic evaluation of the lung. Heart and
respiratory rates decreased significantly after horses
were administered sedatives. A significant transient
decrease in PaO2 was detected immediately after pulmonary
wedge resection, but we did not detect significant
effects on arterial pH, Paco2, or mean arterial
and pulmonary arterial pressures. All horses except 1
were clinically normal after thoracoscopic surgery;
that horse developed hemothorax attributable to iatrogenic
injury to the diaphragm. The second thoracoscopy
revealed minimal inflammation, and there
were no adhesions.
Conclusion and Clinical Relevance—Thoracoscopically
guided pulmonary wedge resection provides
a minimally invasive method for use in obtaining specimens
of lung tissues from healthy horses and those
with lung disease. This technique may be useful for the
diagnosis of diseases of the lungs and thoracic cavity.
(Am J Vet Res 2002;63:1232–1240)
Objective—To provide insights into the role of prostaglandin F2α (PGF2α) in the developmental stages of laminitis induced in horses by ingestion of black walnut heartwood extract (BWHE).
Sample Population—10 adult mixed-breed horses.
Procedures—Horses were separated into 2 groups and were euthanatized at 12 hours after placebo (water) administration (control horses) or after BWHE administration and development of Obel grade 1 laminitis. Blood samples were obtained to determine plasma PGF2α concentrations hourly for the first 4 hours and subsequently every 2 hours after substance administration. Laminar arteries and veins were isolated, and responses to increasing concentrations of PGF2α were measured before and after preincubation of blood vessels with prostanoid and thromboxane receptor antagonists SQ 29,548, SC-19220, and AH 6809.
Results—Plasma PGF2α concentrations increased in horses given BWHE; the WBC count decreased concurrently. In control horses, PGF2α was a potent contractile agonist for laminar veins but not for laminar arteries. In horses given BWHE, PGF2α was similarly selective for laminar veins; however, the magnitude of PGF2α-induced venoconstriction was less than that in control horses. After preincubation with SQ 29,548, laminar veins from control horses responded to PGF2α with a small degree of dilation, whereas laminar veins from horses given BWHE did not.
Conclusions and Clinical Relevance—PGF2α may play a role in the inflammatory and vascular dysfunction associated with the prodromal stages of laminitis. Prostanoids such as PGF2α may be viable targets for the prevention of acute laminitis in horses.
Objective—To evaluate the incidence of colic and risk factors for colic in equids hospitalized for ocular disease.
Design—Retrospective observational study.
Animals—337 equids (317 horses, 19 ponies, and 1 donkey) hospitalized for ocular disease.
Procedures—Medical records of equids hospitalized for > 24 hours for treatment of ocular disease between January 1997 and December 2008 were reviewed. Information from only the first hospitalization was used for equids that were hospitalized for ocular disease on more than 1 occasion. Information gathered included the signalment, the type of ocular lesion and the treatment administered, and any colic signs recorded during hospitalization as well as the severity, presumptive diagnosis, and treatment of the colic. Statistical analysis was used to identify any risk factors for colic in equids hospitalized for ocular disease.
Results—72 of 337 (21.4%) equids hospitalized for ocular disease had signs of colic during hospitalization. Most equids (59.7% [43/72]) had mild signs of colic, and most (87.5% [63/72]) were treated medically. Ten of 72 (13.9%) equids with colic had a cecal impaction. Risk factors for colic in equids hospitalized for ocular disease were age (0 to 1 year and ≥ 21 years) and an increased duration of hospitalization (≥ 8 days).
Conclusions and Clinical Relevance—There was a high incidence of colic in equids hospitalized with ocular disease in this study. Findings from this study may help identify equids at risk for development of colic and thereby help direct implementation of prophylactic measures.
Objective—To determine the effects of the protein kinase C (PKC) inhibitor, Ro-31-8220, on agonist-induced constriction of laminar arteries and veins obtained from horses.
Sample Population—Laminar arteries and veins obtained from 8 adult mixed-breed horses.
Procedures—Laminar arteries and veins were isolated and mounted on small vessel myographs for the measurement of isometric tension. Concentration-response curves were then obtained for the vasoconstrictor agonists phenylephrine, 5-hydroxytryptamine, prostaglandin F2α, and endothelin-1. All responses were measured with or without the addition of Ro-31-8220 (3μM).
Results—Laminar veins were more sensitive to vasoconstrictor agonists than laminar arteries, and incubation of laminar veins with Ro-31-8220 resulted in significantly smaller agonist-induced contractile responses for all agonists tested. In contrast, Ro-31-8220 had no effect on agonist-induced contractile responses of laminar arteries.
Conclusions and Clinical Relevance—Results of the study were consistent with activation of PKC being confined to agonist-induced contraction of laminar veins isolated from the laminar dermis of horses. Consequently, the possible involvement of PKC in the venoconstriction observed during the development of laminitis is worthy of further investigation.
Objective—To determine the effects of inhibition of Rho-kinase or Src-family protein tyrosine kinases (srcPTK) on agonist-induced contractile responses in equine laminar arteries and veins.
Sample Population—Laminar arteries and veins obtained from 13 adult mixed-breed horses.
Procedures—Laminar vessels were mounted on myographs and exposed to phenylephrine (PE), 5-hydroxytryptamine (5-HT), prostaglandin F2α (PGF2α), and endothelin-1 (ET-1) with or without the Rho-kinase inhibitor Y-27632 (10μM), srcPTK inhibitor PP2 (10μM), or a negative control analogue for PP2 (PP3; 10μM).
Results—Responses to PE were reduced by use of Y-27632 in laminar vessels (approx inhibition, 55%). However, Y-27632 reduced responses to 5-HT to a greater degree in veins than in arteries (approx inhibition of 55% and 35%, respectively). The Y-27632 also reduced responses of laminar veins to ET-1 by approximately 40% but had no effect on maximum responses of laminar arteries to ET-1, although a rightward shift in the concentration response curve was evident. Addition of PP2 reduced responses to PE, 5-HT, and PGF2α in laminar veins by approximately 40%, 60%, and 65%, respectively, compared with responses after the addition of PP3; PP2 had no effect on responses to ET-1. In laminar arteries, PP2 reduced 5-HT–induced contractions by approximately 50% but did not affect responses to PE or ET-1.
Conclusions and Clinical Relevance—Results of the study were consistent with activation of Rho-kinase being important during agonist-induced constriction in laminar vessels, activation of srcPTK being an agonist-dependent event, and more prominent roles for Rhokinase and srcPTK in veins than in arteries.
Objective—To characterize the relative contributions of voltage-gated and capacitative Ca2+ entry to agonist-induced contractions of equine laminar arteries and veins.
Animals—16 adult mixed-breed horses.
Procedures—Laminar arteries and veins were isolated and mounted on small vessel myographs for the measurement of isometric tension. Concentration-response curves were obtained for the vasoconstrictor agonists phenylephrine, 5-hydroxytryptamine (5-HT), prostaglandin F2α (PGF2α), and endothelin-1 (ET-1) either in the absence of extracellular Ca2+ or in the presence of the voltage-gated Ca2+ channel inhibitor diltiazem or the putative inhibitor of capacitative Ca2+ entry, trifluoromethylphenylimidazole.
Results—In the absence of extracellular Ca2+, maximal responses of veins to 5-HT, phenylephrine, ET-1 and PGF2α were reduced by 80%, 50%, 50%, and 45%, respectively; responses of arteries to 5-HT, phenylephrine, and ET-1 were reduced by 95%, 90%, and 20%, respectively. Although diltiazem did not affect the maximal responses of veins to any agonist, responses of arteries to 5-HT, phenylephrine, and ET-1 were reduced by 40%, 50%, and 27%, respectively. Trifluoromethylphenylimidazole did not affect maximal responses of veins, but did reduce their contractile responses to low concentrations of ET-1 and PGF2α.
Conclusions and Clinical Relevance—Results suggested that the contribution of extracellular Ca2+ to laminar vessel contractile responses differs between arteries and veins and also between contractile agonists, voltage-gated Ca2+ entry is more predominant in laminar arteries than in veins, and capacitative Ca2+ entry has a minor role in agonist-induced contractile responses of laminar veins.
Objective—To compare measurements of myeloperoxidase (MPO) in plasma, laminar tissues, and skin obtained from control horses and horses given black walnut heartwood extract (BWHE).
Animals—22 healthy 5- to 15-year-old horses.
Procedures—Horses were randomly assigned to 4 groups as follows: a control group given water (n = 5) and 3 experimental groups given BWHE (17) via nasogastric intubation. Experimental groups consisted of 5, 6, and 6 horses that received BWHE and were euthanatized at 1.5, 3, and 12 hours after intubation, respectively. Control horses were euthanatized at 12 hours after intubation. Plasma samples were obtained hourly for all horses. Laminar tissue and skin from the middle region of the neck were harvested at the time of euthanasia. Plasma and tissue MPO concentrations were determined via an ELISA; tissue MPO activity was measured by use of specific immunologic extraction followed by enzymatic detection.
Results—Tissues and plasma of horses receiving BWHE contained significantly higher concentrations of MPO beginning at hour 3. Laminar tissue and skin from horses in experimental groups contained significantly higher MPO activity than tissues from control horses. Concentrations and activities of MPO in skin and laminar tissues were similar over time.
Conclusions and Clinical Relevance—In horses, BWHE administration causes increases in MPO concentration and activity in laminar tissue and skin and the time of increased MPO concentration correlates with emigration of WBCs from the vasculature. These findings support the hypothesis that activation of peripheral WBCs is an early step in the pathogenesis of acute laminitis.