To determine whether therapeutic concentrations (> 0.5 to 1.0 μg/mL) of polymyxin B (PB) were achieved in the tarsocrural joint of horses when the drug was administered by IV regional limb perfusion (IV-RLP) via a saphenous vein at doses of 25, 50, and 300 mg and to describe any adverse systemic or local effects associated with such administration.
9 healthy adult horses.
In the first of 2 experiments, 6 horses each received 25 and 50 mg of PB by IV-RLP via a saphenous vein with at least 2 weeks between treatments. For each treatment, a tourniquet was placed at the midmetatarsus and another was placed midway between the stifle joint and tarsus. Both tourniquets were removed 30 minutes after the assigned dose was administered. Blood and tarsocrural joint fluid samples were collected for determination of PB concentration before and at predetermined times after drug administration. In experiment 2, 4 horses were administered 300 mg of PB by IV-RLP in 1 randomly selected pelvic limb in a manner identical to that used in experiment 1.
For all 3 doses, the mean synovial fluid PB concentration was > 10 times the therapeutic concentration and below the level of quantification at 30 and 1,440 minutes after drug administration, respectively. No adverse systemic or local effects were observed following PB administration.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested that IV-RLP of PB might be a viable alternative for treatment of horses with synovial infections caused by gram-negative bacteria.
Objective—To measure pH, volatile fatty acid (VFA)
concentrations, and lactate concentrations in stomach
contents and determine number and severity of
gastric lesions in horses fed bromegrass hay and alfalfa
Animals—Six 7-year-old horses.
Procedure—A gastric cannula was inserted in each
horse. Horses were fed each diet, using a randomized
crossover design. Stomach contents were collected
immediately after feeding and 1, 2, 3, 4, 5, 6, 7, 8, 10,
12, and 24 hours after feeding on day 14. The pH and
VFA and lactate concentrations were measured in gastric
juice. Number and severity of gastric lesions were
scored during endoscopic examinations.
Results—The alfalfa hay-grain diet caused significantly
higher pH in gastric juice during the first 5 hours
after feeding, compared with that for bromegrass hay.
Concentrations of acetic, propionic, and isovaleric acid
were significantly higher in gastric juice, and number
and severity of nonglandular squamous gastric lesions
were significantly lower in horses fed alfalfa hay-grain.
Valeric acid, butyric acid, and propionic acid concentrations
and pH were useful in predicting severity of
nonglandular squamous gastric lesions in horses fed
alfalfa hay-grain, whereas valeric acid concentrations
and butyric acid were useful in predicting severity of
those lesions in horses fed bromegrass hay.
Conclusions and Clinical Relevance—An alfalfa haygrain
diet induced significantly higher pH and VFA concentrations
in gastric juice than did bromegrass hay.
However, number and severity of nonglandular squamous
gastric lesions were significantly lower in horses
fed alfalfa hay-grain. An alfalfa hay-grain diet may buffer
stomach acid in horses. (Am J Vet Res 2000;61:
Objective—To determine the tissue-restricted expression pattern of tyrosinase mRNA in canine and equine melanocytic tumors and relative tyrosinase and major histocompatibility complex (MHC) I mRNA expression in variants of melanocytic tumors.
Sample—39 canine and 8 equine tumor samples and 10 canine and 6 equine normal tissue samples.
Procedures—RNA was isolated from formalin-fixed, paraffin-embedded tissues. Real-time PCR assays were designed to amplify canine and equine tyrosinase, S18 ribosomal RNA, and major histocompatibility complex I transcripts. Relative expression was determined by use of S18 as a reference and comparison with pigmented and nonpigmented normal tissues.
Results—High tyrosinase expression was found in all melanocytic tumors, compared with normal tissues, and expression had no correlation with presence or absence of tumor pigmentation. No significant difference in tyrosinase expression was found among histologic variants of melanocytic tumors. No correlation was found between MHC I and tyrosinase expression or tissue histologic classification.
Conclusions and Clinical Relevance—In the present study, the methods used were highly sensitive and specific for detection of tyrosinase expression in equine and canine tumors, and overexpression of this transcript in melanomas was detected. This suggested that a DNA vaccine developed for use in dogs with melanoma that targets tyrosinase may be considered for use in other affected species, such as horses.