The presence of minocycline in the tear film of normal horses following oral administration and its anticollagenase activity.

PURPOSE: Tetracyclines have activity against matrix metalloproteinases (MMP). Oral medications with effects on the ocular surface are of interest in patients where repeated topical dosing is limited. The aim of this study was to characterize the concentration of minocycline in the tears of normal horses after oral administration and to determine if this level directly inhibits MMP activity. METHODS: Five healthy adult ponies were administered oral minocycline (Wedgewood Pharmacy; Swedesboro, NJ) at 4 mg/kg every 12 h for 5 days. Tears were collected at T = 2, 26, 50, 56, 74, 80, and 98 h. Tear minocycline concentrations were analyzed using high performance liquid chromatography. The inhibition of recombinant human MMP-2 and MMP-9 by minocycline was investigated using fluorescence resonance energy transfer. RESULTS: Minocycline was present in the tears of each pony at every measurement but with interpony variability. A mean concentration of 11.8 µg/mL was present 2 h after administration of the first dose. Minocycline did not directly inhibit MMP-2 or MMP-9 function at a concentration achieved in the pony tear film. CONCLUSIONS: Minocycline was present in the tears of all ponies at each sampling point following oral administration. One pony of the five had consistently lower levels of minocycline secretion (P ≤ 0.05). The concentration secreted in the tears did not directly inhibit MMP-2 or MMP-9 when tested in vitro. The inconsistencies in the tear concentration and the inhibition activity suggest topical application may be necessary to attain direct inhibition of MMP with minocycline.

Measurement of intraocular pressure in healthy anesthetized horses during hoisting.

OBJECTIVE: To measure intraocular pressure (IOP) in horses during hoisting after induction of anesthesia. STUDY DESIGN: Prospective nonrandomized clinical study. ANIMALS: Eighteen healthy adult horses aged [mean±standard deviation (SD)] 10±4.2 years and weighing 491±110 kg anesthetized for elective procedures. METHODS: IOP was measured in the superior eye of each horse based on planned recumbency after induction of anesthesia. Measurements were taken directly after premedication with xylazine or detomidine with butorphanol, after induction with diazepam-ketamine, after intubation, when suspended by the hoist and on the operating table. During hoisting, the head was supported and the eye-heart height was measured to account for variations in head positioning among patients. IOPs were compared across time points using repeated-measures analysis of variance. Regression was used to compare IOP outcome with potential cofactors. RESULTS: Compared with measurements after premedication (17.5±2.5 mmHg) (mean±SD), hoisting significantly increased IOP (32.4±15.3 mmHg) (p<0.01). The highest recorded IOP in the hoist was 80.0 (range, 16.0-80.0) mmHg. The difference in IOP between premedication and hoisting was 15.0±16.2 (range, -1.0 to 68.0) mmHg. Body weight had a significant effect on absolute IOP and change in IOP in the hoist (p<0.01). CONCLUSIONS AND CLINICAL RELEVANCE: Hoist IOP was significantly higher than post-premedication IOP with heavier horses having higher hoist IOPs and greater increases in IOP. The clinician should take this relationship into account when anesthetizing and hoisting larger horses where an increase in IOP could be detrimental.

Clinical behavior of intraocular teratoid medulloepithelioma in two-related Quarter Horses.

The objective of this paper is to describe clinical behavior, histopathologic features, and immunohistochemical staining of two-related horses with intraocular teratoid medulloepithelioma. Two-related Quarter Horses with similar intraocular masses presented to the UF-CVM Comparative Ophthalmology Service for evaluation and treatment. The first horse, a 3-year-old gelding, had glaucoma and a cyst-like mass in the anterior chamber. Enucleation was performed. Histopathology revealed a teratoid medulloepithelioma. The tumor was considered to be completely excised. Fifteen months later, the gelding presented with swelling of the enucleated orbit and local lymph nodes with deformation of the skull. Cytology revealed neuroectodermal neoplastic cells. Necropsy confirmed tumor metastasis. Six weeks later, a 9-year-old mare, a full sibling to the gelding, presented for examination. An infiltrative mass of the iris and ciliary body was found that extended into the anterior, posterior, and vitreal chambers. Uveitis was present, but secondary glaucoma was not noted. Enucleation was performed and the histopathologic diagnosis was also teratoid medulloepithelioma. The mare has had no recurrence to date, 2 years following enucleation. Metastasis of intraocular teratoid medulloepithelioma is possible. Staging is recommended in cases where the diagnosis of teratoid medulloepithelioma is confirmed. Surveillance of full siblings is recommended until more information regarding etiology is known.

Serum and tissue concentrations of gallium after oral administration of gallium nitrate and gallium maltolate to neonatal calves.

OBJECTIVE: To determine serum and tissue concentrations of gallium (Ga) after oral administration of gallium nitrate (GaN) and gallium maltolate (GaM) to neonatal calves. ANIMALS: 8 healthy neonatal calves. PROCEDURES: Calves were assigned to 1 of 2 groups (4 calves/group). Gallium (50 mg/kg) was administered as GaN or GaM (equivalent to 13.15 mg of Ga/kg for GaN and 7.85 mg of Ga/kg for GaM) by oral gavage once daily for 5 days. Blood samples were collected 0, 0.25, 0.5, 1, 2, 4, 8, 12, and 24 hours after Ga administration on day 1; 4 and 24 hours after Ga administration on days 2, 3, and 4; and 4, 12, and 24 hours after Ga administration on day 5. On day 6, calves were euthanized and tissue samples were obtained. Serum and tissue Ga concentrations were measured by use of mass spectrometry. RESULTS: Data were adjusted for total Ga dose, and comparisons were made between the 2 groups. Calves receiving GaM had a significantly higher dose-adjusted area under the curve and dose-adjusted maximum serum Ga concentration than did calves receiving GaN. Despite receiving less Ga per dose, calves receiving GaM had tissue Ga concentrations similar to those for calves receiving GaN. CONCLUSIONS AND CLINICAL RELEVANCE: In this study, calves receiving GaM had significantly higher Ga absorption than did calves receiving GaN. These findings suggested that GaM might be useful as a prophylactic agent against Mycobacterium avium subsp paratuberculosis infection in neonatal calves.

Detection of endogenous cortisol in equine tears and blood at rest and after simulated stress.

OBJECTIVE: To determine whether cortisol is present in equine tears at rest and during simulated stress and compare tear cortisol to serum free and total cortisol. MATERIALS AND METHODS: Fourteen healthy adult horses were included. Paired tear total cortisol and serum total and free cortisol concentrations were measured with ELISA, chemiluminescent immunoassay, and ultrafiltration methodology, respectively, in 10 horses at rest once daily for five consecutive days. In an additional four horses, paired tear and serum samples were collected for cortisol measurement before and after adrenocorticotropic hormone (ACTH) stimulation (cosyntropin, 1 µg/kg IV). RESULTS: Cortisol was detectable in equine tears at rest. Following ACTH stimulation, tear cortisol increased significantly from baseline at 60-120 min (P ≤ 0.001). Serum total and free cortisol also increased significantly at 30-180 min after ACTH stimulation (P ≤ 0.001). Both serum and tear cortisol returned to baseline concentrations by 360 min. Changes in tear cortisol were similarly associated with changes in serum total and free cortisol, although high tear cortisol concentrations suggest a portion of tear cortisol may be protein-bound. DISCUSSION: Cortisol is present in equine tears and increases in concert with serum cortisol following ACTH stimulation. Further study is needed to determine whether endogenous cortisol in tears contributes to ocular pathology.