Sildenafil stimulates aqueous humor turnover in rabbits.

Sildenafil citrate increases ocular blood flow and accelerates the rate of anterior chamber refilling after paracentesis. The latter effect could have resulted from a reduction in outflow facility or from an increase in aqueous humor (AH) production. In this study, we used scanning ocular fluorophotometry to examine the effects of sildenafil on AH turnover, and thus, AH production in eyes of live normal rabbits.

Interaction between mechanical and osmotic forces in the isolated rabbit lens.

Based on our previous work showing that cow and rabbit lenses isolated with their accommodation anatomical components intact change volume during simulated accommodation in vitro, and that hyposmolality and hyperosmolality also produce volume changes, we tested the idea that exerting these forces simultaneously may add or counteract each other. Further, we attempted to find a point at which osmotic and mechanical forces may cancel each other. Using previously described methodology, we found that combined stretching and anisotonic conditions applied to a lens always produced less of a volume change than that observed on its paired lens from the fellow eye that was only subjected to anisotonic conditions.

Surface change of the mammalian lens during accommodation.

Classical theories suggest that the surface area of the crystalline lens changes during accommodation while the lens volume remains constant. Our recent work challenged this view by showing that the lens volume decreases as the lens flattens during unaccommodation. In this paper we investigate 1) the magnitude of changes in the surface of the in vitro isolated cow lens during simulated accommodation, as well as that of human lens models, determined from lateral photographs and the application of the first theorem of Pappus; and 2) the velocity of the equatorial diameter recovery of prestretched cow and rabbit lenses by using a custom-built software-controlled stretching apparatus synchronized to a digital camera.

Regulation of water permeability in rabbit conjunctival epithelium by anisotonic conditions.

Effects of unilateral exposure to anisotonic conditions on diffusional water permeability of the isolated rabbit conjunctiva were determined. A segment of the bulbar-palpebral conjunctiva was mounted between Ussing-type hemichambers under short-circuit conditions. Unidirectional water fluxes (J(dw)) were measured in either direction by adding (3)H(2)O to one hemichamber and sampling from the other.

Spontaneous fluid transport across isolated rabbit and bovine ciliary body preparations.

Purpose: To quantify spontaneous fluid transport across the isolated ciliary bodies of rabbit and bovine and to determine their osmotic permeabilities.

Methods: A complete annulus of ciliary body was mounted in a custom-designed chamber appropriate for detecting net fluid movement across the in vitro preparation.

Results: A net fluid flow in the blood-to-aqueous direction was measured.

Cl- secretory effects of EBIO in the rabbit conjunctival epithelium.

Experiments were conducted to determine whether the Cl- secretagogue, 1-ethyl-2-benzimidazolinone (EBIO), stimulates Cl- transport in the rabbit conjunctival epithelium. For this study, epithelia were isolated in an Ussing-type chamber under short-circuit conditions. The effects of EBIO on the short-circuit current (I(sc)) and transepithelial resistance (R(t)) were measured under physiological conditions, as well as in experiments with altered electrolyte concentrations.

Distribution of acetylcholine-sensitive currents around the rabbit crystalline lens.

The relative distribution of acetylcholine (ACh) receptors on the surface of the isolated ocular lens of the rabbit was determined from induced changes in translens short-circuit current (I(SC)) and the translenticular resistance (R(t)) at seven delineated, parallel zones from the anterior to the posterior pole. For this, one O-ring (from among several having different diameters) was used to separate two zones in a vertically arranged Ussing-type chamber. Different O-rings separated different zone pairs.

Regional distribution of the Na(+) and K(+) currents around the crystalline lens of rabbit.

Early studies described asymmetrical electrical properties across the ocular lens in the anterior-to-posterior direction. More recent results obtained with a vibrating probe indicated that currents around the lens surface are not uniform by showing an outwardly directed K(+) efflux at the lens equator and Na(+) influx at the poles. The latter studies have been used to support theoretical models for fluid recirculation within the avascular lens.