Effect of Pseudomonas aeruginosa elastase, alkaline protease, and exotoxin A on corneal proteinases and proteins.

PURPOSE: To determine the effects of exoproducts from the corneal pathogen Pseudomonas aeruginosa on corneal proteinases and proteins. METHODS: Whole rabbit corneas were cultured in the presence or absence of broths conditioned with Pseudomonas aeruginosa, elastase, alkaline protease, and exotoxin A. Protein synthesis was assayed by adding 35S-methionine during the last 6 hours of culture. Caseinolytic assays and zymography on sodium dodecyl sulfate polyacrylamide gels containing casein and gelatin were used in the presence and absence of inhibitors to quantify and identify corneal proteinases. RESULTS: The major proteinases released by the corneas were 92/89 kD (MMP9) and 65 kD (72 kD gelatinase, MMP2) gelatinases and a 97 kD caseinase. Minor proteinases observed included 184, 166, 156, 153, 126, 111, 102, 60, 57, and 43 kD gelatinases and 170, 136, 85, and 54 kD caseinases. P. aeruginosa elastase at 1 microgram/ml cleaved the 92 kD gelatinase to yield a 77 kD active form and cleaved the 65 kD gelatinase to yield a 57 kD active form. At 25 micrograms/ml elastase, the gelatinases were degraded. P. aeruginosa alkaline protease had no effect on the 92 or 65 kD gelatinases. Both elastase and alkaline protease degraded the 97 kD caseinase. Proteinases other than elastase and alkaline protease in P. aeruginosa103- and P. aeruginosa01-conditioned broths also activated and/or degraded corneal proteinases. Exotoxin A inhibited the synthesis of the 92 kD gelatinase and most other proteins. The 72 kD gelatinase and the 97 kD caseinase were released in the presence of exotoxin A. CONCLUSIONS: Pseudomonas aeruginosa exoproducts can contribute directly to keratitis caused by Pseudomonas organisms through toxic effects on corneal cells and degradation of corneal proteins and indirectly through the activation of corneal proteinases.

The effect of retinoic acid on thymidine incorporation and morphology of corneal stromal fibroblasts.

The effect of retinoic acid on DNA synthesis and cell morphology was studied using corneal stromal fibroblasts in culture. All-trans retinoic acid induces an increase in DNA synthesis after 24 hours of exposure. Autoradiographic studies of 3H-thymidine incorporation into corneal stromal cells exposed to 10(-6) M retinoic acid for 24 hours showed an increase in labeling which ranged from 19.2% to 67.6% over control cultures. Scintillation analysis of labeled cultures also showed an increase in incorporation of 3H-thymidine into cells treated with 10(-6) M retinoic acid, with increases ranging from 21.8% to 114.7% above control cultures. Exposure of cultured corneal stromal cells to 10(-6) M retinoic acid resulted in a dramatic change in cell morphology such that they changed from spindle-shaped to round, flattened cells which were epithelioid in appearance. These data demonstrate that biological activity of retinoic acid in stromal fibroblasts and imply a role for vitamin A in maintenance of stroma structure and function.

Blindness in a dog with IgA-forming myeloma.

A 9-year-old dog with a 2-month history of weight loss and a 1-week history of blindness had an IgA-forming myeloma. Seemingly, the blindness was a result of bilaterally detached retinas. The dog also had leukopenia, anemia, hypoalbuminemia, hyperglobulinemia, and proteinuria as well as lytic lesions in the cervical portion of the spine and high IgA concentrations in serum and urine. Evaluation of aspirates from the subretinal spaces revealed lymphocytes in a proteinaceous fluid. Histologically, retinal lesions consisted of vascular endothelial cell damage and intraretinal cysts and hemorrhages.

Brow suspension for treatment of ptosis and entropion in dogs with redundant facial skin folds.

Brow suspension surgery was performed on 7 dogs with redundant facial skin folds, associated ptosis, and entropion. The surgical technique involved subcutaneous placement of polyester mesh strips to suspend the upper eyelid from the dorsal frontalis muscle and the underlying periosteum of the skull. Visual impairment associated with ptosis was resolved in all dogs at the 2 week reevaluation period. Upper eyelid position was maintained in 4 of 7 dogs available for long-term follow-up. One dog developed persistent draining tracts in the region of the implant, and removal of part of the implanted mesh was eventually required. Upper eyelid height in this dog, however, was maintained following mesh removal, probably because of fibrosis around the implant. Brow suspension is an option for surgical management of upper eyelid ptosis and entropion in dogs with redundant skin folds and avoids the need for facial skin fold excision.

Hyphema associated with retinal disease in dogs: 17 cases (1986-1991).

We evaluated the medical records of 17 dogs with hyphema of presumed retinal origin to evaluate the clinical, laboratory, ultrasonographic, and histologic features as well as known complications. The mean age of the dogs was 11.5 years. Routine hematologic and biochemical evaluation failed to identify an underlying cause in any dog. Retinal detachments, however, were identified in 10 of 13 dogs evaluated by ultrasonography and 5 of 6 globes evaluated histologically. In 1 dog, hyphema was associated with retinal vascular disease, presumed to be caused by hypertension. The prognosis for vision in geriatric dogs with hyphema, secondary to retinal disease, was found to be grave, as 10 dogs developed secondary glaucoma. The outcome for all dogs was loss of vision.

Persistent corneal ulcers. What to do when ulcers won't heal.

Persistent corneal erosions may be primary or secondary to a variety of ocular diseases such as KCS, infection, or adnexal disease. Primary corneal diseases that may result in nonhealing erosions include corneal EBMD and endothelial dystrophy or degeneration. The challenge that the practitioner faces is to differentiate between them and to apply the appropriate treatment. A variety of medical and surgical therapies are at the disposal of the practitioner. These include debridement, contact lens placement, superficial keratectomy, punctate keratotomy, hyperosmotic solutions, and several new drug modalities such as epidermal growth factor, fibronectin, and aprotinin.