Long-term nitrite-oxidizing bacteria suppression in a continuous activated sludge system exposed to frequent changes in pH and oxygen set-points.

Research has proven the adaptation of nitrite-oxidizing bacteria to unfavorable environmental conditions, and this work presents a novel concept to prevent nitrite oxidation during partial nitrification in wastewater. The approach is based on the real-time updating of mathematical models of the process to search for optimal set-points of pH and oxygen concentration in a continuous activated sludge reactor with a high sludge age (20.3 days).

Model systems for the study of steroid-induced IOP elevation.

Steroid-induced IOP elevation affects a significant number of patients. It results from a decrease in outflow facility of the aqueous humor. To understand the pathophysiology of this condition a number of model systems have been created.

Tissue plasminogen activator reduces the elevated intraocular pressure induced by prednisolone in sheep.

We have previously shown that tissue plasminogen activator (tPA) injected in the vitreous of sheep, reduced or prevented the elevation of the intraocular pressure (IOP) normally produced by the instillation of 1% prednisolone. We now report the effect of tPA when injected into the anterior chamber (AC) in amounts of 0.01, 0.

Reduction of steroid-induced intraocular pressure elevation in sheep by tissue plasminogen activator.

Purpose: To investigate whether tissue plasminogen activator (tPA) can prevent and/or reverse steroid-induced IOP elevation in an ovine model.

Methods: Three animal groups were subjected to bilateral steroid-induced IOP elevation using thrice daily topical ocular prednisolone administration. In the first group (N = 8), one eye each of two sheep was injected intravitreally with 100 μg, 200 μg, 500 μg, or 1 mg human recombinant tPA, while contralateral eyes received vehicle.

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.

Fluid circulation determined in the isolated bovine lens.

Purpose: In 1997, a theoretical model was developed that predicted the existence of an internal, Na(+)-driven fluid circulation from the poles to the equator of the lens. In the present work, we demonstrate with a novel system that fluid movement can be measured across the polar and equatorial surface areas of isolated cow lenses. We have also determined the effects of ouabain and reduced bath [Na(+)].

Sildenafil accelerates anterior chamber refilling after paracentesis in sheep and rabbits.

Purpose: Sildenafil increases ocular blood flow. Thus, the authors investigated if it also increases anterior chamber (AC) refilling after paracentesis.

Methods: Corriedale sheep and albino rabbits were used as animal models.

Gene expression changes in steroid-induced IOP elevation in bovine trabecular meshwork.

Purpose: To determine whether gene expression changes occur in the trabecular meshwork (TM) of cow eyes with steroid-induced intraocular pressure (IOP) elevation.

Methods: Adult female Braford cows (n = 4) were subjected to uniocular prednisolone acetate treatment for 6 weeks. IOP was monitored with an applanation tonometer.

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.

An hypothesis on pressure transmission from anterior chamber to optic nerve.

Few studies have characterized how pressure in the anterior chamber (AC) of the eye is transmitted via the vitreous to the vitreous-ganglion cell interface. We are aware of only one study that simultaneously measured the pressures in the AC and vitreous humor; and of only one study that simultaneously measured the pressures in the AC and the suprachoroidal space (SCS). The pressure in the AC is defined as the intraocular pressure (IOP), which when elevated beyond statistically normal limits is a recognized risk factor for glaucoma, a malady best described as an optic neuropathy with degeneration and eventual death of the retinal ganglion cells (GC's) and highly characteristic changes in the optic nerve head (ONH).

Effect of sildenafil citrate on intraocular pressure and blood pressure in human volunteers.

Anecdotal reports have suggested that the vasodilator, sildenafil citrate, which evokes its effect via a select inhibition of PDE5, has the potential to increase intraocular pressure (IOP) in some individuals. An ocular hypertensive effect by sildenafil was also recently described in a sheep animal model. In contrast, clinical studies have not found a direct association between sildenafil ingestion (commonly consumed as Viagra) and changes in IOP.

Electroantennographic and behavioral responses of adults of raspberry weevil Aegorhinus superciliosus (Coleoptera: Curculionidae) to odors released from conspecific females.

The raspberry weevil, Aegorhinus superciliosus (Guérin) (Coleoptera: Curculionidae), is the most important pest in blueberry and raspberry fields in the south of Chile. In this study, we investigated the electroantennographic and behavioral responses of A. superciliosus to semiochemicals released from conspecific individual adults, with particular attention to male attraction to females.

Morphologic changes in the outflow pathways of bovine eyes treated with corticosteroids.

Purpose: To analyze morphologic changes in the trabecular meshwork (TM) of bovine eyes treated with topical prednisolone and exhibiting elevated intraocular pressure for 4 weeks.

Methods: The TM of four adult Braford cow eyes treated with 0.5% prednisolone eye drops three times daily for 7 weeks and their contralateral eyes treated with artificial tear preparation and that of two adult untreated Braford cows and untreated young calves eyes were analyzed with light and electron microscopy.

Suppression of corticosteroid-induced ocular hypertension in sheep by anecortave.

Objective: To confirm the ocular hypotensive effects of anecortave acetate on an ovine model for steroid-induced ocular hypertension. Eyes of normal sheep exhibit a robust steroid-induced ocular hypertensive response. Recent observations in an uncontrolled, interventional case series indicated that anecortave elicited hypotensive effects when administered as a sub-Tenon depot in the eyes of a small sample of patients with glaucoma.

Effects of sildenafil and tadalafil on intraocular pressure in sheep: implications for aqueous humor dynamics.

Purpose: To determine the effects of vasodilators on intraocular pressure (IOP) and the protein content of sheep aqueous humor (AH), because the vasodilators may increase fluid leakage from the fenestrated capillaries of the ciliary body to the extracellular tissue and directly to the anterior chamber (AC) via the iris, and some senior patients (older than 70) treated with sildenafil have exhibited elevated IOP.

Methods: Experiments were performed on domestic sheep residing on a ranch in Argentina. These docile and compliant animals readily swallowed tablets of sildenafil (50 and 100 mg) and tadalafil (20 mg).

Treatment of sheep steroid-induced ocular hypertension with a glucocorticoid-inducible MMP1 gene therapy virus.

Purpose: To investigate whether intracameral injection of the adenovirus vector AdhGRE.MMP1 would reduce or prevent elevated intraocular pressure (IOP) induced by corticosteroids in living animals.

Methods: Glucocorticoid-inducible adenovirus vectors carrying wild-type or mutant forms of human metalloproteinase 1 (MMP1 and mutMMP1) cDNAs were generated.

Changes in rabbit and cow lens shape and volume upon imposition of anisotonic conditions.

In vivo, mammalian lenses have the capacity to effect fully reversible changes in shape, and possibly volume, during the accommodation process. Isolated lenses also change shape by readily swelling or shrinking when placed in anisotonic media. However, the manner by which the lens changes its shape when its volume is changed osmotically is not firmly established.

Inhibitions of chloride transport and gap junction reduce fluid flow across the whole porcine ciliary epithelium.

Purpose: To study the effects of chloride transport and gap junction inhibitors on fluid formation across the porcine ciliary epithelium.

Methods: A complete annulus of porcine iris-ciliary body preparation was mounted onto a modified Ussing type chamber to measure the fluid flow (FF) rate. The potential difference (PD) across the preparation was monitored simultaneously.

Steroid-induced ocular hypertension in normal sheep.

Purpose: To determine whether the ovine eye develops elevation of intraocular pressure (IOP) in response to corticosteroid applied topically.

Methods: IOP was monitored by Perkins applanation tonometry in a group of 18 sheep receiving topically administered 0.5% prednisolone acetate in one eye (experimental), three times daily, for a period of 3 or four 4 weeks after the establishment of baseline IOP values.

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.

Fluid transport phenomena in ocular epithelia.

This article discusses three largely unrecognized aspects related to fluid movement in ocular tissues; namely, (a) the dynamic changes in water permeability observed in corneal and conjunctival epithelia under anisotonic conditions, (b) the indications that the fluid transport rate exhibited by the ciliary epithelium is insufficient to explain aqueous humor production, and (c) the evidence for fluid movement into and out of the lens during accommodation. We have studied each of these subjects in recent years and present an evaluation of our data within the context of the results of others who have also worked on electrolyte and fluid transport in ocular tissues. We propose that (1) the corneal and conjunctival epithelia, with apical aspects naturally exposed to variable tonicities, are capable of regulating their water permeabilities as part of the cell-volume regulatory process, (2) fluid may directly enter the anterior chamber of the eye across the anterior surface of the iris, thereby representing an additional entry pathway for aqueous humor production, and (3) changes in lens volume occur during accommodation, and such changes are best explained by a net influx and efflux of fluid.

IBMX-elicited inhibition of water permeability in the isolated rabbit conjunctival epithelium.

Agents expected to increase intracellular cAMP levels were tested on the diffusional water permeability (P(dw)) of isolated rabbit conjunctival epithelia given recent indications of the apical expression of AQP5, a water channel homologue regulated by cAMP in other cell systems. For these experiments, segments of conjunctivae were mounted between Ussing-type hemichambers under short-circuit conditions. Unidirectional water fluxes (J(dw)) were measured by adding (3)H(2)O to one hemichamber and sampling from the other, while the electrical parameters (I(sc) and R(t)) were recorded simultaneously.

Fluid transport across the isolated porcine ciliary epithelium.

Purpose: To quantify spontaneous fluid transport across the isolated porcine ciliary epithelium and determine its sensitivity to the electrolyte transport inhibitors ouabain and bumetanide, as well as bath Cl(-) and HCO(3)(-) levels.

Methods: A complete annulus of ciliary body was mounted in a custom-designed chamber appropriate for quantifying net fluid movement, as well as the transepithelial potential difference (PD) across the in vitro ciliary epithelium.

Results: A spontaneous and stable fluid flow (FF) in the blood-to-aqueous direction was measured over a 4-hour period.