Browsing by Author "Turner, Tracy A"

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    Adrenergic, cholinergic and nonadrenergic-noncholinergic intrinsic innervation of the jejunum in horses
    (American Veterinary Medical Association, 1999) Malone, Erin D; Kannan, Mathur S; Brown, David R; Turner, Tracy A; Trent, Ava M
    OBJECTIVE: To determine the major neurotransmitters that regulate contractile activity in the jejunum of horses. SAMPLE POPULATION: Jejunal specimens from 65 horses without gastrointestinal tract lesions. PROCEDURE: Jejunal smooth muscle strips, oriented in the plane of the circular or longitudinal muscular layer, were suspended isometrically in muscle baths. Neurotransmitter release was induced by electrical field stimulation (EFS) delivered at 30 and 70 V intensities and at various frequencies on muscle strips maintained at low or high muscle tone. To detect residual nonadrenergic-noncholinergic neurotransmission, the response of muscle to EFS in the presence of adrenergic and cholinergic blockade was compared with the response in the presence of tetrodotoxin. RESULTS: Atropine (ATR) decreased the contractile response of muscle strips to EFS under most conditions. However, ATR increased the contractile response of high-tone circular muscle. Adrenergic blockade generally increased the muscle responses to 30 V EFS and in high-tone longitudinal muscle but decreased contractile responses in high-tone circular muscle. Tetrodotoxin significantly altered the responses to EFS, compared with adrenergic and cholinergic receptor blockade. CONCLUSIONS: Acetylcholine and norepinephrine appear to be important neurotransmitters regulating smooth muscle contractility in the equine jejunum. They induce contraction and relaxation, respectively, in most muscle preparations, although they may cause opposite effects under certain conditions. In addition, nonadrenergic-noncholinergic excitatory and inhibitory influences were detected. CLINICAL RELEVANCE: Acetylcholine or norepinephrine release within the myenteric plexus of horses may alter gastrointestinal motility.
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    Severe Carpometacarpal Osteoarthritis in Older Arabian Horses
    (Veterinary Surgery, 2003) Malone, Erin; Les, Cliff A; Turner, Tracy A
    Objective—To report a severe form of carpometacarpal osteoarthritis (CMC-OA) affecting primarily older Arabian horses. Study Design—Retrospective study. Animals—Thirty-one horses with CMC-OA. Methods—Carpal radiographs (405 sets) from 3 hospitals were evaluated to identify horses with marked osteoproliferative reaction across the medial aspect of the CMC joint. Owners were contacted to obtain detailed histories and status updates. Necropsy specimens of the CMC joint were evaluated at 2 hospitals to determine the prevalence of 2 variations in the articulation between the proximalsecond and third metacarpal bones. Results—Thirty-one horses were identified as having marked osteoproliferative reaction at the CMC joint. Twenty-three (74%) were Arabian horses. Of the Arabian horses, the average age at admission was 14.4 years. Eight (34.8%) Arabian horses had a known history of trauma. Most were no longer rideable at presentation. Ten of the horses were subsequently euthanatized because of lameness. The dorsal and palmar articulations between the second and third metacarpal bones were examined in 177 horses. The palmar articulation was absent in 48% of Arabian horses and 12.5% of non-Arabian horses at 1 center, including 4 horses with CMC-OA. At the second center, the palmar articulation was present in 8 of 8 Arabian horses but was absent in 22 of 92 (24%) non-Arabian horses. Conclusions—An increased frequency of this crippling form of OA was observed in Arabian horses. It may reflect an increased prevalence, in some geographical regions, of an absent palmar articulation between the second and third metacarpal bones. Clinical Relevance—Carpal trauma in some Arabian horses may result in unexpectedly severe carpometacarpal osteoarthritis.