Inhibition of notch signalling ameliorates experimental inflammatory arthritis.

OBJECTIVE: To test the hypothesis that Notch signalling plays a role in the pathogenesis of rheumatoid arthritis (RA) and to determine whether pharmacological inhibition of Notch signalling with γ-secretase inhibitors can ameliorate the RA disease process in an animal model. METHODS: Collagen-induced arthritis was induced in C57BL/6 or Notch antisense transgenic mice by immunisation with chicken type II collagen (CII). C57BL/6 mice were administered with different doses of inhibitors of γ-secretase, an enzyme required for Notch activation, at disease onset or after onset of symptoms. Severity of arthritis was monitored by clinical and histological scores, and in vivo non-invasive near-infrared fluorescence (NIRF) images. Micro-CT was used to confirm joint destruction. The levels of CII antibodies and cytokines in serum were determined by ELISA and bead-based cytokine assay. The expression levels of cytokines were studied by quantitative PCR in rheumatoid synovial fibroblasts. RESULTS: The data show that Notch signalling stimulates synoviocytes and accelerates their production of proinflammatory cytokines and immune responses involving the upregulation of IgG1 and IgG2a. Pharmacological inhibition of γ-secretase and antisense-mediated knockdown of Notch attenuates the severity of inflammatory arthritis, including arthritis indices, paw thickness, tissue damage and neutrophil infiltration, and reduces the levels of active NF-κB, ICAM-1, proinflammatory cytokines and matrix metalloproteinase-3 activity in the mouse model of RA. CONCLUSIONS: These results suggest that Notch is involved in the pathogenesis of RA and that inhibition of Notch signalling is a novel approach for treating RA.

Secretases as therapeutic targets for Alzheimer's disease.

Accumulation of amyloid-ß (Aß) is widely accepted as the key instigator of Alzheimer's disease (AD). The proposed mechanism is that accumulation of Aß results in inflammatory responses, oxidative damages, neurofibrillary tangles and, subsequently, neuronal/synaptic dysfunction and neuronal loss. Given the critical role of Aß in the disease process, the proteases that produce this peptide are obvious targets. The goal would be to develop drugs that can inhibit the activity of these targets. Protease inhibitors have proved very effective for treating other disorders such as AIDS and hypertension. Mutations in APP (amyloid-ß precursor protein), which flanks the Aß sequence, cause early-onset familial AD, and evidence has pointed to the APP-to-Aß conversion as a possible therapeutic target. Therapies aimed at modifying Aß-related processes aim higher up the cascade and are therefore more likely to be able to alter the progression of the disease. However, it is not yet fully known whether the increases in Aß levels are merely a result of earlier events that were already causing the disease.

Notch1 Has an Important Role in ß-Cell Mass Determination and Development of Diabetes.

BACKGROUND: Notch signaling pathway plays an important role in regulating pancreatic endocrine and exocrine cell fate during pancreas development. Notch signaling is also expressed in adult pancreas. There are few studies on the effect of Notch on adult pancreas. Here, we investigated the role of Notch in islet mass and glucose homeostasis in adult pancreas using Notch1 antisense transgenic (NAS). METHODS: Western blot analysis was performed for the liver of 8-week-old male NAS mice. We also conducted an intraperitoneal glucose tolerance test (IPGTT) and intraperitoneal insulin tolerance test in 8-week-old male NAS mice and male C57BL/6 mice (control). Morphologic observation of pancreatic islet and ß-cell was conducted in two groups. Insulin secretion capacity in islets was measured by glucose-stimulated insulin secretion (GSIS) and perifusion. RESULTS: NAS mice showed higher glucose levels and lower insulin secretion in IPGTT than the control mice. There was no significant difference in insulin resistance. Total islet and ß-cell masses were decreased in NAS mice. The number of large islets (≥250 µm) decreased while that of small islets (<250 µm) increased. Reduced insulin secretion was observed in GSIS and perifusion. Neurogenin3, neurogenic differentiation, and MAF bZIP transcription factor A levels increased in NAS mice. CONCLUSION: Our study provides that Notch1 inhibition decreased insulin secretion and decreased islet and ß-cell masses. It is thought that Notch1 inhibition suppresses islet proliferation and induces differentiation of small islets. In conclusion, Notch signaling pathway may play an important role in ß-cell mass determination and diabetes.

Alzheimer's disease-causing presenilin-1 mutations have deleterious effects on mitochondrial function.

Mitochondrial dysfunction and oxidative stress are frequently observed in the early stages of Alzheimer's disease (AD). Studies have shown that presenilin-1 (PS1), the catalytic subunit of γ-secretase whose mutation is linked to familial AD (FAD), localizes to the mitochondrial membrane and regulates its homeostasis. Thus, we investigated how five PS1 mutations (A431E, E280A, H163R, M146V, and Δexon9) observed in FAD affect mitochondrial functions. Methods: We used H4 glioblastoma cell lines genetically engineered to inducibly express either the wild-type PS1 or one of the five PS1 mutants in order to examine mitochondrial morphology, dynamics, membrane potential, ATP production, mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs), oxidative stress, and bioenergetics. Furthermore, we used brains of PS1M146V knock-in mice, 3xTg-AD mice, and human AD patients in order to investigate the role of PS1 in regulating MAMs formation. Results: Each PS1 mutant exhibited slightly different mitochondrial dysfunction. Δexon9 mutant induced mitochondrial fragmentation while A431E, E280A, H163R, and M146V mutants increased MAMs formation. A431E, E280A, M146V, and Δexon9 mutants also induced mitochondrial ROS production. A431E mutant impaired both complex I and peroxidase activity while M146V mutant only impaired peroxidase activity. All PS1 mutants compromised mitochondrial membrane potential and cellular ATP levels were reduced by A431E, M146V, and Δexon9 mutants. Through comparative profiling of hippocampal gene expression in PS1M146V knock-in mice, we found that PS1M146V upregulates Atlastin 2 (ATL2) expression level, which increases ER-mitochondria contacts. Down-regulation of ATL2 after PS1 mutant induction rescued abnormally elevated ER-mitochondria interactions back to the normal level. Moreover, ATL2 expression levels were significantly elevated in the brains of 3xTg-AD mice and AD patients. Conclusions: Overall, our findings suggest that each of the five FAD-linked PS1 mutations has a deleterious effect on mitochondrial functions in a variety of ways. The adverse effects of PS1 mutations on mitochondria may contribute to MAMs formation and oxidative stress resulting in an accelerated age of disease onset in people harboring mutant PS1.

Alzheimer's disease and Notch signaling.

Cleavage of the amyloid precursor protein (APP) by gamma-secretase generates a neurotoxic amyloid beta-peptide (Abeta) that is thought to be associated with the neurodegeneration observed in Alzheimer's disease (AD) patients. Presenilin is the catalytic member of the gamma-secretase proteolytic complex and mutations in presenilins are the major cause of early-onset familial Alzheimer's disease. In addition to APP, gamma-secretase substrates include Notch1 homologues, Notch ligands Delta and Jagged, and additional type I membrane proteins, raising concerns about mechanism-based toxicities that might arise as a consequence of inhibiting gamma-secretase. Notch signaling is involved in tumorigenesis as well as in determining the fates of neural and nonneural cells during development and in adults. Alterations in proteolysis of the Notch by gamma-secretase could be involved in the pathogenesis of AD. Inconsistently, several recent observations have indicated that enhanced Notch signaling and expression could be instrumental in neurodegeneration in AD. Therefore, detailed and precise study of Notch signaling in AD is important for elucidating diverse mechanisms of pathogenesis and potentially for treating and preventing Alzheimer's disease.

Protective Effects of Vildagliptin against Pioglitazone-Induced Bone Loss in Type 2 Diabetic Rats.

Long-term use of thiazolidinediones (TZDs) is associated with bone loss and an increased risk of fracture in patients with type 2 diabetes (T2DM). Incretin-based drugs (glucagon-like peptide-1 (GLP-1) agonists and dipeptidylpeptidase-4 (DPP-4) inhibitors) have several benefits in many systems in addition to glycemic control. In a previous study, we reported that exendin-4 might increase bone mineral density (BMD) by decreasing the expression of SOST/sclerostin in osteocytes in a T2DM animal model. In this study, we investigated the effects of a DPP-4 inhibitor on TZD-induced bone loss in a T2DM animal model. We randomly divided 12-week-old male Zucker Diabetic Fatty (ZDF) rats into four groups; control, vildagliptin, pioglitazone, and vildagliptin and pioglitazone combination. Animals in each group received the respective treatments for 5 weeks. We performed an intraperitoneal glucose tolerance test (IPGTT) before and after treatment. BMD and the trabecular micro-architecture were measured by DEXA and micro CT, respectively, at the end of the treatment. The circulating levels of active GLP-1, bone turnover markers, and sclerostin were assayed. Vildagliptin treatment significantly increased BMD and trabecular bone volume. The combination therapy restored BMD, trabecular bone volume, and trabecular bone thickness that were decreased by pioglitazone. The levels of the bone formation marker, osteocalcin, decreased and that of the bone resorption marker, tartrate-resistant acid phosphatase (TRAP) 5b increased in the pioglitazone group. These biomarkers were ameliorated and the pioglitazone-induced increase in sclerostin level was lowered to control values by the addition of vildagliptin. In conclusion, our results indicate that orally administered vildagliptin demonstrated a protective effect on pioglitazone-induced bone loss in a type 2 diabetic rat model.

Notch1 deficiency decreases hepatic lipid accumulation by induction of fatty acid oxidation.

Notch signaling pathways modulate various cellular processes, including cell proliferation, differentiation, adhesion, and communication. Recent studies have demonstrated that Notch1 signaling also regulates hepatic glucose production and lipid synthesis. However, the effect of Notch1 signaling on hepatic lipid oxidation has not yet been directly investigated. To define the function of Notch1 signaling in hepatic lipid metabolism, wild type mice and Notch1 deficient antisense transgenic (NAS) mice were fed a high-fat diet. High-fat diet -fed NAS mice exhibited a marked reduction in hepatic triacylglycerol accumulation compared with wild type obese mice. The improved fatty liver was associated with an increased expression of hepatic genes involved in fatty acid oxidation. However, lipogenic genes were not differentially expressed in the NAS liver, suggesting lipolytic-specific regulatory effects by Notch1 signaling. Expression of fatty acid oxidative genes and the rate of fatty acid oxidation were also increased by inhibition of Notch1 signaling in HepG2 cells. In addition, similar regulatory effects on lipid accumulation were observed in adipocytes. Taken together, these data show that inhibition of Notch1 signaling can regulate the expression of fatty acid oxidation genes and may provide therapeutic strategies in obesity-induced hepatic steatosis.

Concanavalin A-induced posterior subcapsular cataract: a new model of cataractogenesis.

PURPOSE: To evaluate the effect of Concanavalin A (Con A) on cataract formation in New Zealand Albino rabbits. Uveitis is a chronic inflammatory condition of the eye involving the anterior and/or posterior segments. It may be acute or chronic and is associated with the development of posterior subscapular cataract over time. Con A is a nonspecific inflammatory agent and mitogen for T cells and some B cells. Used extensively in immunogenic studies Con A has been shown to induce uveitis after intravitreal injection in New Zealand Albino rabbits. METHODS: In two separate studies, Con A was injected intracamerally or intravitreally into one eye of 12 New Zealand Albino rabbits and an equal volume of balanced salt solution was injected into the opposite eye as a control. In a third study, the effect of topical steroids after intravitreal injection of Con A was evaluated. In all studies, anterior and posterior inflammation and the development of cataract was monitored by slit lamp biomicroscopy and photography. Cataract formation was also studied histopathologically. RESULTS: Initially, all eyes treated with Con A demonstrated moderate anterior chamber inflammation while eyes treated with balanced salt solution showed no inflammation. Three months after treatment, posterior subcapsular cataracts were present in all rabbit eyes treated with intravitreal Con A. In the third study, topical steroid treatment of Con A-induced inflammation significantly reduced anterior chamber inflammation but had no effect on vitreous humor and posterior subcapsular cataract formation. CONCLUSION: This experimental model was the first to demonstrate the development of posterior subcapsular cataracts after Con-A induced inflammation. The cataract was clinically and histologically similar to human posterior subscapular cataracts.

Lens regeneration in New Zealand albino rabbits after endocapsular cataract extraction.

PURPOSE: To evaluate the regenerative capacity of the adult rabbit lens after removal of a Concanavalin A-induced posterior subcapsular cataract. METHODS: Cataractogenesis was induced by intravitreal injection of Concanavalin A in adult New Zealand albino rabbits. At 7 mo postinjection, the cataracts were removed. Endocapsular lens extraction was performed by phacoemulsification and irrigation/aspiration with Balanced Salt Solution. RESULTS: Postoperatively, lens regeneration was first noted in the Balanced Salt Solution normal lens group at 3 weeks and the Concanavalin A cataract group at 6 weeks. By the 3-mo postoperative examination, lens regrowth, measured by digital image analysis, filled 74.5% of the capsule bag in the Balanced Salt Solution normal lens group and 46.6% in the Concanavalin A cataract group. In the latter group, less lens material was regenerated and at a slower rate than in eyes with extraction of a normal lens. CONCLUSION: This experimental model is the first to show that lens regeneration can occur after removal of cataracts secondary to inflammation.

A histologic study of lens regeneration in aphakic rabbits.

Lens regeneration occurs in New Zealand albino rabbits after endocapsular lens extraction, which leaves the anterior and posterior lens capsules relatively intact. Slit-lamp photography, histologic studies, and lens protein analysis confirmed the differentiation of lens fibers. In the current study, we performed a sequential analysis of the regenerating rabbit lens. After endocapsular phacoemulsification and irrigation/aspiration of the lens, rabbits were sacrificed at different time points for histologic evaluation. Similarities with embryologic development of the lens were evident, although in some sections, abnormal cellular proliferation occurred. By the 6th day after surgery, a monolayer of lens epithelial cells lined both the anterior and posterior capsules. At 1 month, the posterior epithelial cells had elongated, and nuclei had migrated anteriorly. At 2 months, lens cells were differentiating at the equatorial zone with gradual elongation, anterior migration of nuclei, and eventual loss of nuclei.

Lens regeneration in juvenile and adult rabbits measured by image analysis.

Secondary cataract growth commonly occurs after extracapsular cataract extraction. The proliferation of this regrowth occurs at rates related to many factors. In this study, the authors analyzed the amount of lens regeneration after endocapsular lens extraction that leaves the anterior and posterior capsules relatively intact. The analysis was performed in New Zealand albino rabbits with the aid of image analysis measurements in young and adult animals. The effect of low vacuum suction of the anterior capsule on the growth was determined. Lens regeneration was used as a measure of the growth potential of the leftover epithelial cells in the capsule bag. The results showed that lens regeneration was significantly faster in younger rabbits. However, low vacuum suction had no effect on the growth rate. Potential therapeutic agents for preventing secondary cataracts may be better analyzed with image analysis processing of lens regeneration, a precise and rapid measurement technique.

Ofloxacin vs tobramycin for the treatment of external ocular infection. Ofloxacin Study Group II.

A multicenter, double-masked, randomized clinical investigation was conducted comparing 0.3% ofloxacin and 0.3% tobramycin for topical treatment of external ocular infection. One drop (1.35 micrograms) of either test solution was instilled six times daily for 2 days and thereafter four times daily for the next 8 days. At the day 3 to 5 follow-up examination, the severity of signs and symptoms based on a clinical summary score of 10 key variables was reduced from baseline values significantly (P less than .05) more with ofloxacin (-6.4 +/- 4.37; mean +/- SD) than with tobramycin (-4.78 +/- 3.13); by day 11, the difference between the groups was no longer significant. At days 3 to 5 and day 11 examinations, clinical, microbiologic, and overall improvement rates were similar, with no significant differences seen between the groups. Ofloxacin was found as effective, safe, and comfortable as tobramycin in patients with external ocular infection and may provide earlier symptom relief.

Topical ofloxacin compared with gentamicin in the treatment of external ocular infection. Ofloxacin Study Group.

In a double-masked, randomised, controlled study the effectiveness and safety of 0.3% ofloxacin solution were compared with those of 0.3% gentamicin ophthalmic solution in treating external bacterial ocular infections. The clinical improvement rate for patients treated with ofloxacin was 98% (51/52) and 92% (48/52) for those treated with gentamicin. Microbiological improvement was achieved in 78% (40/51) of the ofloxacin patients, compared with 67% (35/52) of the gentamicin group. Ofloxacin treatment eradicated or controlled 85% (86/101) of the Gram positive and 89% (17/19) of the Gram negative organisms cultured, compared with 83% (103/124) and 78% (29/37), respectively, after gentamicin treatment. None of these differences were statistically significant. The incidence of adverse effects attributable to ofloxacin treatment (3.2%) was less than that reported for gentamicin (7.1%). Ofloxacin proved to be an effective, safe, and comfortable therapy for external bacterial ocular infection.

Restoring lens capsule integrity enhances lens regeneration in New Zealand albino rabbits and cats.

In studies conducted by numerous investigators for 150 years, lenses regenerated following endocapsular lens extraction in New Zealand albino rabbits have been irregular in shape, appearing primarily doughnut-shaped as a result of lack of lens growth at the site of the anterior capsulotomy and its adhesion to the posterior capsule. In the present study, we restored the lens capsule integrity by inserting a collagen patch at the time of surgery to seal the anterior capsulotomy and to improve the shape and structure of the regenerated lenses. We then filled the capsule bag with air to prevent adhesions between the anterior and posterior capsule and maintain capsule tautness and shape. Lens regeneration was first noted as early as one to two weeks. Regenerated lens filled approximately 50% of the capsule bag at two weeks and 100% by five weeks. Subsequent growth was in the anterior-posterior direction and measured by A-scan biometry. Lens thickness increased by 0.3 mm per month. The regenerated lenses were spherical with normal cortical structure and a nuclear opacity. In conclusion, restoration of lens capsular integrity with a collagen patch following endocapsular lens extraction enhanced the shape, structure, and growth rate of the regenerated lenses. In addition, lens regeneration was shown to occur in two cats.

Intralenticular implant study in pigmented rabbits: opacity lensmeter assessment.

PURPOSE: To quantitatively analyze the clarity of regenerated lens material after endocapsular lens extraction and restoration of the lens capsular bag with and without implantation of an intralenticular disc lens. SETTING: Shepherd Research Center, Allergan, Irvine, California, USA. METHOD: The clarity of regenerated lens material was evaluated by Interzeag Opacity Lensmeter 701 (OLM) recordings after endocapsular lens extraction in New Zealand/Dutch Belt pigmented rabbits with (n = 21) and without (n = 16) placement of a disc-shaped intralenticular implant in the capsular bag. Postoperative objective measurements were performed at 1, 2, and 3 weeks and 1, 2, 3, and 6 months. Comparisons were made between young and adult rabbits. RESULTS: Mean OLM results were similar in both groups at weeks 1, 2, 3, and 4. After 1 month, progressive central compaction of early irregular regenerated lens fibers was associated with increased OLM readings that were higher in the intralenticular implant group than in the control group. Regenerated lens opacification was greater in tissue posterior to the intralenticular lens than in that anterior to the disc lens. CONCLUSION: Insertion of an intralenticular disc lens into the lens capsule bag was associated with poor optical clarity primarily of the posterior regenerated lens tissue. The OLM was useful in assessing the degree of opacification of the regenerated lenses.

Focal laser photophacoablation of normal and cataractous lenses in rabbits: preliminary report.

We evaluated the effect of focal laser photophacoablation on (1) a normal lens and (2) previously induced traumatic anterior cortical and posterior subcapsular cataracts in New Zealand albino rabbits. A Q-switched neodymium:YAG (Nd:YAG) laser was used to deliver 6 to 97 50 microns laser spots of 2.0 mJ to 8.3 mJ of energy/pulse to the normal lens. A neodymium:YLF (Nd:YLF) laser was used to deliver 60 microJ to 140 microJ of energy/pulse with a 0.3 mm to 0.6 mm cube at 1053 nm to ablate selective parts of the normal and cataractous lens. The Nd:YAG laser photoablation of the normal lens produced persistent circular opacities lasting up to one year. The Nd:YLF laser photoablation of the normal lens produced an empty space in the area of treatment (visualized as increased translucency), followed by a return to normal lens architecture at two days. The area remained translucent by slitlamp biomicroscopy for up to six months. Partial photoablation of the induced cataracts with an Nd:YLF laser produced partial clearing of the opacity without any evidence of surrounding lenticular damage. Focal Nd:YLF laser photoablation of lenticular opacities appears to be a relatively safe and noninvasive procedure that can be used for focal lens ablation without lens capsule disruption. The potential use of this treatment for selective removal of focal lens opacities requires further study.

Assessing intraocular lens calcification in an animal model.

PURPOSE: To describe an animal model used to evaluate the propensity of various biomaterials to calcify intraocularly. SETTING: Research Department, Allergan Inc., Irvine, California, USA. METHODS: Intraocular lens (IOL) optic materials were implanted intramuscularly and/or subcutaneously in rabbits for up to 90 days. The materials included silicone, poly(methyl methacrylate) (PMMA), hydroxyethyl methacrylate hydrogel, and several hydrophobic acrylic materials. Scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) were used to detect calcification demonstrated by characteristic discrete nodules containing both calcium and phosphate. Histological methods were used to evaluate tissue reactivity. Disc lenses fabricated from the experimental material were also bilaterally implanted in rabbit eyes that were monitored by slitlamp biomicroscopy. The lenses were explanted at 1, 2, 5.5, 10, and 20 months for SEM/EDS analysis. RESULTS: No calcification was noted in the intramuscularly or subcutaneously implanted silicone, PMMA, and acrylic optic materials. Calcification was noted on the intramuscularly, subcutaneously, and intraocularly implanted experimental acrylic and the intramuscularly implanted hydrogel material; the calcification was more extensive on the hydrogel. Signs that suggested intraocular calcification were first noted on the experimental IOLs at 4 months, but calcification was not confirmed until 10 months. CONCLUSIONS: Material calcification occurred more quickly in an intramuscular or subcutaneous environment than in an intraocular environment. Intramuscular and subcutaneous implantation appears to be an excellent model for screening materials for calcification potential. However, calcification is both host environment and material dependent. Using intramuscular or subcutaneous implantation in animal models to predict intraocular calcification in humans must be done with caution.

Moisture droplet formation on the posterior surface of intraocular lenses during fluid/air exchange.

We investigated the conditions under which moisture droplets would form on intraocular lens (IOL) posterior surfaces during fluid/air exchange procedures in rabbits implanted with silicone or poly(methyl methacrylate) (PMMA) IOLs. Moisture droplets did not form when the posterior capsule was intact, regardless of IOL material or infusion fluid temperature. If a capsular tear was present, droplets formed with both IOL materials when balanced salt solution (BSS) at ambient temperature was used as the infusion fluid. This effect was significantly more pronounced with silicone IOLs, resulting in an immediate loss of visualization of the fundus. In these cases, visualization was quickly restored by applying a viscoelastic to the posterior IOL surface.

Unpreserved carboxymethylcellulose artificial tears evaluated in patients with keratoconjunctivitis sicca.

In order to evaluate the therapeutic value of an unpreserved carboxymethylcellulose-based artificial tear in treatment of keratoconjunctivitis sicca (KCS), 56 patients with severe keratoconjunctivitis sicca were enrolled, at a single study center, in a randomized, double-masked, 8-week comparison with a preserved hydroxypropylmethylcellulose (HMC)-based artificial tear. Patients treated with the carboxymethylcellulose (CMC)-based tear showed significant improvement in fluorescein staining, symptoms, and impression cytology grades. Patients treated with HMC-based tears showed minimal improvement in a few variables. Impression cytology specimens were analyzed by a modified technique that maps the distribution of the various grades present on the specimen. With this technique, improvement in the cytology grades was noted in the group of patients using CMC-based tears. The improvement correlated with observed decreases in symptoms of discomfort and with scores for superficial punctate staining. This study supports the observed therapeutic value of unpreserved CMC-based artificial tears and suggests the possible reversal of squamous metaplasia in patients with KCS. Further studies are required to separate the benefit of the CMC formulation from the benefits of preservative elimination.

Topical ofloxacin in the treatment of Pseudomonas keratitis in a rabbit model.

Ofloxacin, a new quinolone antibiotic with a broad spectrum of activity, is very effective against Pseudomonas aeruginosa in vitro. Its effectiveness was studied in a rabbit model of tobramycin-sensitive P. aeruginosa. Treatment groups received either vehicle, tobramycin 0.3%, or ofloxacin 0.3%. Twelve hours of treatment decreased the bacterial counts from a mean of 2.2 +/- 0.7 x 10(6) colony forming units (cfu) per cornea in the vehicle group to means of 513 +/- 670 and 435 +/- 524 cfu in the tobramycin and ofloxacin groups, respectively. This decrease in bacterial counts was statistically significant (p = 0.001 for tobramycin and ofloxacin each compared with control, p = 0.86 for tobramycin compared with ofloxacin). After seven days, all antibiotic-treated corneas were sterile and the epithelial defects healed at comparable rates. Aqueous humor drug levels were higher in infected eyes without an intact epithelium (p = 0.02); in eyes with intact epithelium, concentrations of ofloxacin were higher than were those of tobramycin (p = 0.002). In this animal model, ofloxacin proved to be an effective antibiotic with no evidence of toxicity.