An improved technique for experimental penetrating keratoplasty in rabbits.

Penetrating keratoplasty is difficult to perform, especially for the beginning ophthalmologist or corneal surgeon. This investigation describes, step by step, a simplified technique of performing experimental keratoplasty on rabbit eyes. Use of this method resulted in 20 of 24 (83%) rabbit eyes maintaining technically successful clear grafts without anterior synechiae or angle-closure glaucoma for up to 3 months postoperatively.

Cryogenic induced ocular HSV-1 reactivation is enhanced by an inhibitor of the lipoxygenase pathway.

Reactivation of latent herpes simplex virus type 1 (HSV-1) has been shown to occur in response to localized inflammation. Prostaglandins and lipoxygenase products [eg. hydroxyeicosatetraenoic acids, (HETEs)] are associated with inflammation and, therefore, may play a role in HSV-1 infection and reactivation. In the rabbit cornea, alkali injury, cryogenic injury, and acute HSV-1 infection promote the synthesis of HETEs. Recently, a platelet activating factor antagonist, ginkgolide B (BN 52021) has been found to specifically inhibit the corneal synthesis of HETEs after alkali injury. If the induction of HETEs after injury is related to HSV reactivation and severity of infection, BN 52021 may alter HSV reactivation and the severity of infection by reducing the production of HETEs. To study the effect of BN 52021 on HSV-1 reactivation, cryogenic corneal lesions were produced in ten HSV-1 latently infected rabbits. Five rabbits were treated with topical and intravenous BN 52021 while the remaining five rabbits received topical artificial tears and intravenous saline. In the BN 52021 treated group, 90% (9/10) of the eyes and 53% (35/66) of the total ocular cultures were positive for HSV-1. In the control group, 60% (6/10) of the eyes, and 27% (18/66) of the ocular swabs were positive for HSV-1. The total number of positive cultures was significantly greater (p less than .05) in the BN 52021 treated rabbits. By increasing the number of positive HSV ocular cultures, BN 52021 appeared to act similarly to other inhibitors of arachidonic acid metabolism such as steroidal and nonsteroidal anti-inflammatory agents.

Expulsive choroidal hemorrhage in rabbits. A histopathologic study.

Expulsive hemorrhage is a catastrophic complication of intraocular surgery that can result in total loss of vision. Suprachoroidal effusion and hemorrhage may precede the development of expulsive hemorrhage; however, the relationship remains unclear. After sedation with intravenous pentobarbital sodium, 11 rabbits were given lactated Ringer's solution and heparin sodium intravenously. The right eyes were proptosed, and the central cornea, lens, and anterior vitreous were removed. After surgery, all 11 eyes (100%) developed choroidal effusion, choroidal hemorrhage, or expulsive hemorrhage. The rabbits were killed at various intervals after surgery so that the eyes could be enucleated and processed for light microscopy. Histologic examination revealed four sequential stages of expulsive hemorrhage as follows: (1) There was engorgement of the choriocapillaris. (2) Suprachoroidal effusion occurred mainly near the posterior pole. (3) As the effusion enlarged, stretching and tearing of choroidal vessels as well as tearing of the vessels and attachments at the base of the ciliary body occurred. (4) Massive extravasation of blood, primarily from the torn vessels at the ciliary body base, resulted in suprachoroidal hemorrhage and expulsion of blood through the surgical wound. This experimental model may provide new information relating to the cause and prevention of expulsive choroidal hemorrhage.

Oral acyclovir reduces the incidence of recurrent herpes simplex keratitis in rabbits after penetrating keratoplasty.

To determine if acyclovir sodium prevents postoperative herpes simplex virus type 1 (HSV-1) recurrences, 21 rabbits harboring latent HSV-1 underwent uniocular autograft penetrating keratoplasty. All operated-on eyes were treated with topical and subconjunctival dexamethasone sodium phosphate. Ten of the 21 rabbits also received oral acyclovir (intravenous acyclovir was given at the time of surgery). Postoperatively, 9 (82%) of 11 operated-on eyes in rabbits not treated with acyclovir had positive HSV-1 ocular cultures. In acyclovir-treated rabbits, however, none of the 10 operated-on eyes had positive ocular cultures. In addition, 9 (82%) of 11 of the operated-on eyes had geographic ulcers develop in the non-acyclovir-treated rabbits, compared with 1 (10%) of 10 in the acyclovir-treated rabbits. Finally, stromal keratitis appeared in 5 (56%) of 9 of the operated-on eyes in non-acyclovir-treated rabbits and 1 (12%) of 8 of the operated-on eyes in acyclovir-treated rabbits. The results of this study indicate that acyclovir significantly lowered the incidence of HSV-1 ocular shedding, geographic ulceration, and stromal keratitis in a rabbit autograft penetrating keratoplasty model.

Cathepsin D of mouse leukemia L1210 cells. Unusual intracellular localization and biochemical properties.

Mouse leukemia L1210 cells contain lysosomes, but cathepsin D, a typical lysosomal enzyme, has an unusual localization. After fractionation of homogenates of L1210 cells by isopycnic density gradient centrifugation, most of the activity for all of the acid hydrolases studied, except cathepsin D, is sedimentable and shows a similar density distribution around a peak having a modal density of 1.16. In contrast, much more of the total activity for cathepsin D is not sedimentable, while the sedimentable activity has a distribution around a peak at a higher density of 1.18. After chromatography on Sephadex G-100 of cell extracts, two molecular weight forms of cathepsin D are found. One has an apparent molecular weight of approx. 45,000, similar to rat liver cathepsin D, while the apparent molecular weight of the second form is approx. 95,000. Both forms are 4-5 times more active than rat liver cathepsin D. The high molecular weight L1210 cathepsin D converts to the low molecular weight form with no loss in activity after treatment with beta-mercaptoethanol. In all respects the unusual intracellular localization and molecular weight forms of cathepsin D in mouse leukemia L1210 cells are similar to the situation found for rat thoracic duct lymphocytes.