Mitsushi Hikida

Characterization of water retentive properties of hyaluronan.

We examined the water retentive properties of hyaluronan because of its reported therapeutic effect in the treatment of dry eye. Hyaluronan dose dependently retarded water loss from a solution kept at constant temperature and humidity. Similarly, water loss was retarded when hyaluronan was placed atop an agar gel. These decreases in water loss were not related to changes in the molecular weight of hyaluronan. Unlike the in vitro models, the evaporation rate from the tears in normal subjects initially increased following the topical application of hyaluronan, and continued a higher rate than with the vehicle. These results suggest that hyaluronan enhances water retention on the corneal surface, and probably increases corneal wettability. Accordingly, hyaluronan eye drops may be useful in the treatment of dry eye.

Concentration and molecular weight dependency of rabbit corneal epithelial wound healing on hyaluronan

Hyaluronan (hyaluronic acid) is a high molecular weight viscoelastic polymer which has been postulated to enhance wound healing. We investigated the dose and molecular weight (9 x 10(4)-280 x 10(4) dependent effects of hyaluronan on the rate of migration of rabbit corneal epithelium in organ culture and on wound closure in vivo after debridement with n-heptanol. When corneal blocks were cultured with hyaluronan for 20 hours, distances of epithelial migration significantly increased over exposed stroma in proportion to hyaluronan concentration. However, there was no difference in the stimulatory action of hyaluronan on epithelial migration when corneal blocks were cultured at 1 mg/ml of hyaluronan irrespective of changes in the molecular weight range between 9 x 10(4) and 280 x 10(4). Glycosaminoglycans other than hyaluronan (chondroitin, chondroitin sulfate, keratan sulfate and heparan sulfate) failed to increase the epithelial migration. When hyaluronan eye drops were instilled after corneal epithelial removal with n-heptanol, hyaluronan stimulated wound closure in a dose-dependent manner, but its stimulatory efficacy was not dependent on molecular weight.

Combined effects of hyaluronan and fibronectin on corneal epithelial wound closure of rabbit in vivo

We investigated the combined effects of hyaluronan and fibronectin on corneal epithelial wound closure in vivo. When fibronectin eye drops (1 mg/ml) were administered for the first 4 hours after chemical cautery and hyaluronan eye drops (1 mg/ml) were administered for following 32 hours, the mean healing rate was significantly higher than in control eyes treated with phosphate buffered saline instead of fibronectin or with initial fibronectin alone. These results demonstrated that hyaluronan and fibronectin have a synergistic effect, with fibronectin pretreatment augmenting hyaluronan-stimulated corneal epithelial wound closure.

Effects of oxidized glutathione and reduced glutathione on the barrier function of the corneal endothelium.

The protective effects of oxidized glutathione (GSSG) and reduced glutathione (GSH) in the irrigating solution based on BSS plus composition (Santen, Osaka, Japan), which is without GSSG (glutathione-free control solution) were compared on rabbit corneal endothelial barrier function. Corneal barrier function was evaluated by determining the effects of GSSG and GSH on carboxyfluorescein permeability (Pac). In a solution containing 0.3 mM GSSG (BSS plus), the Pac was significantly inferior to that of its paired glutathione-free control solution. With 0.6 mM GSH, the Pac was not different from that of its paired glutathione-free control solution. The Pac of the endothelium with 0.3 mM GSSG was significantly inferior to that of paired corneas exposed isolated to 0.6 mM GSH. These results show that the barrier function of the rabbit corneal endothelium is better maintained by supplementing the perfusion solution with 0.3 mM GSSG rather than 0.6 mM GSH.

Characterization of Esterases Involved in the Hydrolysis of Dipivefrin Hydrochloride

We characterized the interaction of the prodrug dipivefrin hydrochloride (DPE) with esterase activity in the rabbit cornea. The esterases which were identified included: (1) cholinesterase, (2) acetylcholinesterase, (3) a mixture containing carboxylesterase, acetylesterase and arylesterase, and (4) a non-specific esterase. DPE suppressed all of their activities as well as that of the mixture containing carboxylesterase, acetylesterase and arylesterase, and a nonspecific esterase. However, its effect on cholinesterase was larger than on any of the other activities, suggesting that DPE is a better substrate for cholinesterase than for any of the other esterases. These measurements along with those of substrate-dependent inhibition of 14C-DPE hydrolysis indicated that the DPE-esterase interaction was competitive based on changes in the apparent Km values which were extracted from Lineweaver-Burk plots of esterase activity. The substrate for cholinesterase competed with DPE most strongly among substrates. These results seem to suggest that DPE is hydrolyzed by various corneal esterases, mainly cholinesterase.

Removal of Lens Epithelial Cells by Dispersion With Enzymatic Treatment Followed by Aspiration

We conducted a preliminary trial of a method of lens epithelial cell removal in cataract surgery that combined mechanical and pharmaceutical treatments. The cells were first loosened from their junctional complexes with Dispase, a preparation of a neutral protease used for separating cells in tissue culture. To avoid intraocular tissue damage, the enzyme preparation was dissolved in sodium hyaluronate and injected into the capsular bag, which was carefully preserved during endocapsular cataract surgery. The cells were then removed by irrigation and aspiration. The results of experiments in vitro and in rabbits and, judging from the histopathologic examination, with negligible damage to the zonules or corneal endothelium.

Removal of lens epithelial cells following loosening of the junctional complex

ABSTRACT We previously reported a new method to remove residual lens epithelial cellsdispersion aspiration. The cells were loosened from their junctional complexes with Dispase®, a proteolytic enzyme. To avoid intraocular tissue damage, the enzyme preparation was dissolved in sodium hyaluronate and injected into the capsular bag, which was carefully preserved during endocapsular cataract surgery. The cells were then removed by minimum irrigation/aspiration. In this study we incorporated ethylenediaminetetraacetic acid (EDTA), a calcium chelating agent for separating epithelial cells in tissue culture, into the procedure. The results of experiments in vitro and in rabbits suggest that this procedure also removed cells effectively with negligible damage to the zonules and corneal endothelium.

Effect of Ofloxacin Eye Drops and Eye Ointment on Corneal Re-Epithelialization

AbstractWe studied the influences of ofloxacin, either eye drops or ointment, on corneal re-epithelialization after denudation with n-heptanol in rabbits. Ofloxacin (0.3%) was administered topically, at effective clinical concentrations, for 2 days after denudation of the corneal epithelium. Its effects were compared with those of the antibacterial agents norfloxacin, gentamicin, erythromycin, and the combination of oxytetracycline and polymyxin B. Neither ofloxacin nor any of those agents affected the time required for re-epithelialization except gentamicin sulfate, which significantly delayed the corneal wound healing 10 hr after denudation. These results suggest that the topical administration of ofloxacin eye drops or ointment after surgery may not influence corneal epithelial wound healing as do other antibacterial eye drops or ointments except gentamicin sulfate.

One-Year Ocular Toxicity Study of Ofloxacin Ophthalmic Solution in Beagle Dogs

Ocular toxicity and systemic adverse effects of 0.3% ofloxacin ophthalmic solution (0.3%OFLX) which was administered 3 times daily for one year were studied in dogs.

Pigmentation of glucocorticoid-induced cataractous lenses of developing chick embryos on heating

Cataractous lenses produced by hydrocortisone or prednisolone treatment in developing chick embryos turned golden brown on heating at 100 degrees C for 60 min. Analysis of an 80% ethanol fraction from the lenses, which contained the pigment-forming substance(s), demonstrated that the heat-induced pigmentation was related to the appearance of opacity of the lens after glucocorticoid administration and suggested that the pigmentation occurred by the Maillard reaction between glucose and amino acids.