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At least 1,081 records · Page 60Linked to original sources
PubMed1985

Action of prostaglandins on the dynamics of the aqueous humor.

Prostaglandins exercise different actions on the structures of the eye; among these is ocular hypertension. The mechanism by which ocular hypertension is provoked seems to be the breaking of the hematoaqueous barrier at the level of the iris and the ciliary processes. By fluorophotometry we studied the dynamics of the aqueous humor after topical administration of prostaglandin E-2 in rats. We observed an important reduction in flow that was interpreted as secondary to the increase in output resistance.

Animals↗
PubMed1985

The resistance of the trabecular meshwork to aqueous humor outflow.

A theoretical model is presented that is able to explain for the first time the pressure drop across the trabecular meshwork. The ramified flow paths in the subendothelial region of the trabecular meshwork can be interpreted as a filter bed. Data from transmission electron microscope (TEM) photographs are the starting point of the theoretical consideration. Taking shrinkage of the sections into account, the pressure gradient across the subendothelial region amounts to 0.05 mm Hg. As these canaliculi are coated by a film of glycosaminoglycans (GAGs), the pressure drop is presumably a function of the film thickness. Only film thicknesses of 0.35 micron led to pressure gradients in the experimentally verified magnitude. As the whole filter bed probably does not contribute to the filtration but only about 10%, the pressure drop specified is reached when the GAG coating is 0.25 micron. As these values seem to be fairly realistic, it can be concluded that the subendothelial region of the juxtacanalicular meshwork (about 2 micron thickness) can be regarded as the "locus generis" of aqueous humor outflow resistance.

Aqueous Humor↗
PubMed1998

[Keratoprosthesis by posterior fixation and mechanical biocompatibility: determination of intraocular pressure provoking aqueous humor leak and/or extrusion].

The effect of a sudden increase in intraocular pressure (IOP) on Eye Bank eyes implanted with a posterior fixation keratoprosthesis PCL5 type (Lacombe) is evaluated. The IOP was artificially increased at a rate close to that observed in direct eye trauma. The critical pressure values causing aqueous humor leak and/or keratoprosthesis extrusion were compared to those found to blow up unoperated eyes. No statistical difference was found between operated and control eyes (6 pairs of eyes). This KPro type showed its efficacy for keratoprosthesis fixation.

Aqueous Humor↗
PubMed1990

Aqueous humor contains transforming growth factor-beta and a small (less than 3500 daltons) inhibitor of thymocyte proliferation.

The anterior chamber of the eye is an immunologically privileged site in which allografts survive longer than at other body sites. In this regard, it is relevant that aqueous humor (AH) inhibits lymphocyte proliferation. In order to analyze AH for specific substances that inhibit thymocyte proliferation, samples of human AH, murine AH, and rhesus monkey AH were added to cultures of thymocytes stimulated by IL-1 or IL-2 in the presence of PHA. All samples of AH tested had potent inhibitory activity on thymocyte proliferation in this system. Inhibitory activity was lost by heating AH to 80 degrees C for 1 h. Dialysis of murine AH indicated that species smaller than 3500 Da were capable of mediating this activity; we have termed the factor(s) responsible for this "small inhibitory factor(s) of AH." Retentate, containing species larger than 3500 Da, retained inhibitory activity, but less than nondialyzed AH. Assays for PGE2 demonstrated that murine and human AH contained small quantities of PGE2. These quantities were insufficient to inhibit thymocyte proliferation in our assay system. Furthermore, AH from mice treatend with indomethacin had full inhibitory activity. Assays for transforming growth factor beta (TGF-beta) after acid activation demonstrated significant quantities of latent TGF-beta within human and murine AH which could be largely neutralized by antisera to TGF-beta. Active TGF-beta "activity" was also present without acid activation in samples of AH at a level approximately 20% that of latent TGF-beta. However, most of this "activity" could not be neutralized by antisera to TGF-beta. AH contains factors capable of limiting thymocyte proliferation.

Animals↗
PubMed1997

Endothelin-like immunoreactivity in aqueous humor of patients with primary open-angle glaucoma and cataract.

BACKGROUND: Experimental evidence suggests a role of endothelin-1 (ET) in the regulation of intraocular pressure (IOP). METHOD: Therefore, in patients undergoing cataract surgery, ET-like immunoreactivity (ETIR) was measured by radioimmunoassay in pooled samples of aqueous humor of eyes with primary open-angle glaucoma (POAG) and normotensive eyes with cataract only. RESULTS: ETIR was significantly (P < 0.05) higher in patients with cataract and POAG (20.5 +/- 1.8 pg/ml, n = 12; preoperative IOP 21.4 +/- 1.1 mmHg, n = 33) than in patients with cataract only (15.8 +/- 1.6 pg/ml, n = 15; preoperative IOP 16.0 +/- 0.6 mmHg, n = 77). CONCLUSION: This finding may indicate a role of ET in POAG or ocular antihypertensive treatment, and its relevance should be further investigated.

Administration, Topical↗
PubMed1991

[Proteolytic enzymes and antiproteases in eye tissue and blood serum. and the protein composition of aqueous humor in experimental corneal burns].

After deep termic and alkaline burns of rabbit's cornea the increasing of activity of neutral trypsinlike proteases, elastase and simultaneous increasing of antitryptic activity are observed in burned part of cornea, part of cornea which is surrounding the burn, and in ciliary body, iris and aqueous humor. One week after termic burn and two weeks after alkaline burn the means of these activities began decrease. The time, when ulceration and perforation of cornea are observed, is corresponded to the period of maximal activity of proteolytic enzymes in the eye tissues. At the peripherical blood there are significant changes of level of main inhibitors of proteolysis (reactants of acute phase of inflammation -alpha 1 antitrypsin and alpha 2 macroglobulin). There are qualitative and quantitative changes of proteins content of aqueous humour in the burned eyes, which have phase characteristics and depend upon the stage of inflammation process.

Animals↗
PubMedDate not supplied

Formation of the aqueous humor.

1. Glaucoma is a worldwide disease affecting approximately 1-2% of the population aged over 35 years in industrial countries and is a major cause of blindness. 2. Glaucoma is usually associated with an increased intraocular pressure reflecting an imbalance between the rate of production of fluid (the aqueous humor) by the ciliary epithelial cells and its drainage from the eye. Therefore, it is important to understand how this secretion is produced. This requires a knowledge of ciliary epithelial cell composition, which has, in the past, proved difficult to obtain in mammalian preparations. 3. We have recently used the technique of electron-probe X-ray microanalysis to determine this composition under a variety of in vitro conditions. 4. Our results have led to a new model for this secretion that emphasizes the potential secretory role of the Na+/K+/2Cl- cotransporter.

Animals↗
PubMedDate not supplied

Comparison of the effects of argon and neodymium:YAG laser iridotomy on cytokines in the rabbit aqueous humor.

PURPOSE: We compared the effects in rabbits of iridotomy using the argon or Nd:YAG laser on cytokines such as interleukin 1-beta (IL-1beta), interleukin 6 (IL-6), interleukin 8 (IL-8), and tumor necrosis factor-alpha (TNF-alpha). METHODS: Twenty pigmented rabbits (20 eyes) underwent argon and Nd:YAG iridotomy under general and topical anesthesia. Group 1 (10 right eyes) was treated with the argon laser and group 2 (10 right eyes) with the Nd:YAG laser, using an equal number of shots and the same laser parameters for each group. Left eyes in both groups were evaluated as controls. Aqueous humor specimens were collected from each eye preoperatively and 1 and 3 days postoperatively. RESULTS: Aqueous IL-6 and TNF-alpha levels rose more on day 1 in the Nd:YAG group than the argon group. IL-6 and TNF-alpha levels were significantly higher on days 1 and 3 than the pre-operative and control levels (p<0.05). TNF-alpha levels on day 1 were significantly lower in the Nd:YAG than the argon group. There were no significant differences between the two laser groups for IL-6 on days 1 and 3. IL-1beta and IL-8 did not change CONCLUSIONS: Our findings suggest that cytokines, particularly IL-6 and TNF-alpha, may be inflammatory mediators in the early inflammation following argon and Nd:YAG laser iridotomies. These results also indicate that cytokines contribute to the acute effects of Nd:YAG and argon laser applications on inflammation.

Animals↗
PubMed1995

Bilateral ocular toxocariasis demonstrated by aqueous humor enzyme-linked immunosorbent assay.

PURPOSE/METHODS: A 14-year-old girl with a history of contact with puppies and chronic bilateral panuveitis was examined. The fundus of the right eye showed an inferotemporal pars plana exudate. The fundus of the left eye showed an elevated posterior mass. RESULTS/CONCLUSION: Toxocara antibodies in the aqueous humor detected by enzyme-linked immunosorbent assay had a Goldmann-Witmer coefficient of 8.63 in the right eye and 8.94 in the left eye. Toxocariasis may be a cause of bilateral panuveitis.

Adolescent↗
PubMed2000

Triamterene measurements in the aqueous humor of rabbits.

The kinetics of topical triamterene penetration were estimated from the time-course measurements of triamterene (in Dyazide) concentrations in the anterior chamber of six rabbits (n=12, left and right eyes). The two-compartment model of Jones and Maurice (1) was fitted to the measurements. We found the apparent elimination rate constant oftriamterene A = 0.33 +/- 0.12 hr(-1), the apparent absorption rate constant of triamterene B = 2.68 +/- 0.55 hr(-1), the cornea-aqueous transfer coefficient in reference to the corneal volume of triamterene kc.ca = 0.28 +/- 0.05 hr(-1), the loss coefficient of triamterene from the anterior chamber ko = 0.43 +/- 0.16 hr(-1) and the amount of triamterene in the cornea at time zero Mo = 483 +/- 125 ng/ml. The mean of ko = 0.43 hr(-1) is significantly lower (p = 0.04% using ZTEST) than the lower limit of aqueous loss coefficient = 0.58 hr(-1) usually found in rabbits (2). We conclude that Dyazide lowers the aqueous flow rate in the positive direction, considering glaucoma treatment. Peak triamterene concentration in the anterior chamber was P = 120 +/- 32 ng/ml. Half-life for elimination from the aqueous humor was T1/2 = 1.84 +/- 0.65 hr (Mean +/- SD).

Absorption↗
PubMed1993

The Glenn A. Fry Award Lecture 1992: aqueous humor proteins: a key for unlocking glaucoma?

In this report I summarize recently reported studies which establish the existence of a previously undocumented diffusional pathway for plasma-derived proteins from the ciliary body stroma to the anterior chamber of the normal mammalian eye via the iris root. The data support the hypothesis that nearly all of the plasma-derived protein present in the aqueous humor of the anterior chamber arrives via this pathway, thus by-passing the posterior chamber. Additional studies suggest that some of the protein transported via the pathway is shunted directly into the trabecular meshwork and aqueous outflow pathways. Perfusion studies show how the perfused eyes were later immunohistochemically stained to reveal the distribution and qualitative amounts of serum albumin. These studies strongly suggest that the well-known "wash-out" effect, encountered in experimental studies of aqueous outflow, arises predominantly from wash-out of the protein depot that serves as the anterior diffusional pathway for proteins. Taken as a whole, these studies support the hypothesis that protein is a physiologically relevant and important element in the generation of normal aqueous outflow resistance, possibly more important than glycosaminoglycans (GAG's).

Animals↗
PubMed1991

[Heterochromia complicata Fuchs, crystalline iridopathy and increased immunoglobulin G in aqueous humor. A case report].

We report on a 35 year old patient suffering from heterochromia complicata Fuchs with a mature cataract. Multiple small whitish-yellowish crystal-lines on the iris at the 7 and 12 o'clock position were interpreted as Russell bodies and correlated with an elevated concentration of 7.2 mg/dl IgG in the aqueous humor analysis. IgA und IgM could not be detected (less than 1.1 mg/dl). Three months after an unremarkable extracapsular cataract extraction and posterior chamber lens implantation a positive Tyndall phenomenon and Russell bodies were found at just the same locations on the iris.

Adult↗