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At least 973 records · Page 54Linked to original sources
PubMed1987

Effects of stimulation of the ocular sympathetic nerves on IOP and aqueous humor flow.

Ocular sympathetic nerves were stimulated chronically in awake rabbits using electrodes unilaterally implanted on the cervical sympathetic trunk. IOP was measured by pneumatonometry and aqueous inflow was measured by fluorophotometry. In each animal, continuous trains of 1 msec pulses were delivered by means of a portable electrical stimulator. Experiments were spaced by 1 week recovery periods. Stimulation was varied over a range of amplitudes (5-15 V) and frequencies (3-12 Hz). Continuous sympathetic stimulation produced an immediate sharp decrease in IOP followed by a gradual rise to pre-stimulation values which were attained 60-90 min after onset. A rebound increase in IOP occurred when stimulation was terminated. The magnitude of the initial IOP drop, the delay in the return to pre-stimulation IOP, and the rebound rise in IOP subsequent to termination of electrical stimulation were proportional to the stimulation frequency. Maximal effects were observed at 12 Hz, and stimulation with 8-10 Hz for 180 min caused a sustained reduction in anterior chamber aqueous humor flow. Topical 2% phentolamine 1 hr before stimulation markedly reduced IOP and abolished the acute IOP changes observed in untreated stimulated animals. Topical 1% timolol did not affect either the initial IOP drop or the rebound; however, the IOP recovered during stimulation to values greater than pre-stimulation IOP. We conclude that in rabbits the beta-adrenergic effect of prolonged sympathetic nerve stimulation is to decrease aqueous flow. Chronic electrical stimulation in awake animals provides an experimental model for studying the role of the ocular sympathetic nerves.

Animals↗
PubMed1984

Characterization of endotoxin-induced C5-derived chemotactic activity in aqueous humor.

Although a cellular exudate characterizes acute anterior uveitis, few studies have sought to identify the chemoattractant(s) contributing to this phenomenon. As a model of acute ocular inflammation, the authors have injected rabbits intravenously with endotoxin (Salmonella typhimurium LPS, 2.5 micrograms/kg). In a Boyden chamber assay, aqueous humor drawn 3 hr after LPS (post-LPS aqueous) exhibited chemotactic activity for purified rabbit granulocytes (PMN). "Checkerboard" analysis indicated that chemotaxis, rather than protein-induced chemokinesis, primarily accounted for PMN migration. Aqueous from normal rabbits demonstrated no chemotactic activity. Chemotactic activity was maximal at 3 hr post-LPS (versus 1 or 5 hr). PMN migration exhibited a direct correlation with the concentration of aqueous tested (0.5-5%). Several observations indicated that this chemotactic activity is complement (C5)-derived. It is inhibited by antibodies to C5 but not affected by antibodies to C3. Similar to rabbit C5a, chemotactic activity in post-LPS aqueous was heat stable at 56 degrees C X 30 min, attracted both human and rabbit PMN at similar concentrations and induced release of beta glucuronidase from PMN. In addition, prior incubation of rabbit PMN with partially purified C5a (densensitization) specifically inhibited chemotactic responses to both C5a and post-LPS aqueous without inhibiting responses to another chemoattractant, n-formyl-methionyl-leucyl-phenylalanine. Finally, chemotactic activity from post-LPS aqueous could be recovered from a Sephadex G75 column and eluted similarly to chemotactic activity in zymosan activated rabbit serum or 13,700 D molecular weight marker. The presence of complement-derived chemotactic activity in this model should not be construed as evidence that this activity contributes to the pathogenesis of endotoxin-induced inflammation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Inhibition of pilocarpine-induced aqueous humor flare, hypotony, and miosis by topical administration of anti-inflammatory and anesthetic drugs to dogs.

OBJECTIVE: To investigate the mechanism by which pilocarpine causes increased aqueous humor (AH) flare, hypotony, and miosis in dogs. ANIMALS: 6 dogs with normal eyes. PROCEDURE: Both eyes of each dog were treated topically with a 2% solution of pilocarpine, and 1 eye of each dog was additionally treated with commercially available ophthamic solutions. Breakdown of the blood-aqueous barrier (BAB) was quantitated in each eye, using laser flaremetry to measure AH flare. Intraocular pressure and pupil size were also measured. RESULTS: Pilocarpine caused increased flare from BAB breakdown that was inhibited by the drugs tested. Inhibition (most to least) of BAB breakdown was flurbiprofen more than diclofenac, proparacaine, or suprofen, which were more than 0.125 or 1.0% prednisolone. Inhibition appeared dose-dependent and caused consensual inhibition in the contralateral eye. Intraocular pressure was decreased only in proparacaine-treated eyes and increased in eyes treated with nonsteroidal anti-inflammatory drugs (NSAID). Flurbiprofen and proparacaine were the most effective at blocking miosis. CONCLUSIONS: Pilocarpine produced a predictable, reproducible BAB breakdown in dogs. Miosis and increased AH flare were inhibited equally by proparacaine or NSAID, suggesting that these signs were caused by neuropeptide release into the AH from antidromic stimulation, which subsequently triggers prostaglandin production. Hypotony was inhibited only by anti-inflammatory drugs. CLINICAL RELEVANCE: Proparacaine in combination with pilocarpine would be the best choice for treating dogs with acute glaucoma. Topical administration of NSAID should not be used to treat dogs with acute glaucoma, because they increase intraocular pressure and negate the effects of pilocarpine.

Administration, Topical↗
PubMed1983

Penetration of metronidazole and tinidazole into the aqueous humor in man.

500 mg of metronidazole or tinidazole were given as a 20-min infusion each to 10 patients who were hospitalized for elective cataract extraction. Metronidazole and tinidazole concentrations in aqueous humor were 5.2 +/- (SE) 0.5 and 5.3 +/- 0.7 micrograms/ml, respectively, 20-70 min after the end of the infusion. Aqueous humor/serum concentration ratios were 0.38 and 0.47 on the average for metronidazole and tinidazole, respectively.

Aged↗
PubMed1977

Chemical composition of the aqueous humor of bovine eyes dependent on predetermined time upon removal.

The content of several carbohydrates [glucose (alpha and beta), inositol, fructose, galactose] and aminoacids in the aqueous of bovine lenses was measured in dependence on time after globe puncture, using the method of gas liquid chromatography (carbohydrates) and ion exchange chromatography (amino acids). The contents of the investigated compounds show distinct postmortal changes. Aqueous humor which had been obtained immediately after enucleation of the bovine eyes and kept at 37 degrees C for different periods of time (1-8 h) showed for the carbohydrates investigated a decrease in fructose concentration, whereas almost all amino acid concentrations were increased, with the exception of leucine, tyrosine, and arginine, which were decreased.

Age Factors↗
PubMed1991

Effect of bunazosin hydrochloride on intraocular pressure and aqueous humor dynamics in normotensive human eyes.

We investigated the effects of topical administration of bunazosin hydrochloride, a new selective alpha 1-adrenergic antagonist, on intraocular pressure and aqueous humor dynamics in normal human eyes. In the single-dose study, all concentrations of bunazosin (0.025%, 0.05%, 0.1%, and 0.2%) significantly lowered intraocular pressure in a concentration-dependent manner. Administration of multiple doses of 0.1% bunazosin revealed no occurrence of tachyphylaxis after 1 week. Single application of 0.1% bunazosin had no significant influence on aqueous flow rate, tonographic outflow facility, or episcleral venous pressure, suggesting that bunazosin reduces intraocular pressure by increasing uveoscleral outflow. Aqueous protein concentration was found to be unaltered by bunazosin, indicating that blood-aqueous barrier permeability to protein molecules remained unchanged. We conclude that bunazosin may be a possible new antiglaucoma agent with a mechanism of action different from those currently in use for treating ocular hypertension.

Administration, Topical↗
PubMedDate not supplied

Detection of connective tissue growth factor in human aqueous humor.

PURPOSE: Connective tissue growth factor (CTGF) has been shown to be substantially involved in various processes of fibrosis. We investigated if CTGF is present in aqueous humor (AH). METHODS: Samples from AH were collected from 10 volunteers during cataract surgery. Specific ELISA analysis was performed with goat IGG against human CTGF. RESULTS: CTGF was above the detection limit of the assay in 80% of the samples. The concentration of CTGF in the anterior chamber fluid was 1.24 +/- (SD) 0.26 ng/ml. CONCLUSION: CTGF is present in a majority of AH samples, possibly representing a constant component in this fluid. The origin and physiological importance of CTGF is yet unclear. The involvement of CTGF in processes of intraocular fibrosis and wound healing is possible.

Aged↗
PubMed1983

Effects of alpha 1 and alpha 2 activation of adrenergic receptors on aqueous humor dynamics.

Effects of phenylephrine (alpha 1-adrenergic agonist), prazosin (alpha 1-adrenergic antagonist), clonidine (alpha 2-adrenergic agonist), and yohimbine (alpha 2-adrenergic antagonist) on aqueous humor (AH) dynamics were studied with a cat eye model. Phenylephrine (130 microgram/ml) inhibited AH outflow (67% at 90 min. period) more than AH formation (26% at the same period) indicating the intraocular pressure (IOP) might be raised by the administration of phenylephrine. Prazosin (0.1 microgram/ml) produced effects opposite to those of phenylephrine (55% reduction of AH formation and 25% reduction of AH outflow at 3 hr. period) suggesting the alpha 1-adrenergic receptor is responsible for increases rather than decreases of IOP. Both clonidine (10 microgram/ml) and yohimbine (0.1-1.0 microgram/ml) inhibited AH formation (60% inhibition) more than AH outflow (no inhibition for clonidine and 40% inhibition for yohimbine) to lower IOP. The conventional theory of receptor antagonism does not seem to function at alpha 2-receptor sites.

Animals↗
PubMed1996

Oxymetazoline: potential mechanisms of inhibitory effects on aqueous humor dynamics.

Oxymetazoline, an alpha 2 agonist, was active in lowering intraocular pressure in normal and sympathetically denervated rabbit eyes. Ocular hypotension was accompanied by decreased aqueous humor inflow. Topical pretreatment with rauwolscine, an alpha 2 antagonist, reduced the oxymetazoline-induced hypotensive effect more in contralateral than in ipsilateral eyes indicating the possible involvement of central alpha 2 adrenoceptors. Efaroxan, a relatively selective imidazoline antagonist, and diclofenac, a cyclooxygenase inhibitor, failed to inhibit the oxymetazoline-induced ocular hypotensive response. Oxymetazoline induced mydriasis in treated eyes at all doses. In in vitro studies, oxymetazoline inhibited isoproterenol-stimulated cAMP production in rabbit iris-ciliary bodies and cultured rabbit nonpigmented ciliary epithelial cells. The inhibition of cAMP accumulation induced by oxymetazoline was antagonized by rauwolscine or by BRL-44408, a relatively selective alpha 2A-adrenoceptor antagonist. These data indicate that oxymetazoline lowered intraocular pressure by activating alpha 2A receptors (ciliary epithelium) and that the ocular hypotensive effect was not totally dependent on intact sympathetic nerves. Results suggest that mechanisms involving centrally mediated effects of oxymetazoline are probable and this possibility is currently under investigation.

Adrenergic alpha-Agonists↗
PubMed1980

Effect of prazosin on aqueous humor dynamics in rabbits.

Prazosin hydrochloride, a systemic antihypertensive agent, lowers intraocular pressure when applied topically to normal rabbit eyes. A 0.01% solution of topically administered prazosin did not alter out-flow facility, episcleral venous pressure, systemic blood pressure, or ocular blood flow. Tonography suggested a 27% decrease in the rate of aqueous humor formation two hours following topical administration. Posterior chamber aqueous ascorbate levels were increased following topical administration of prazosin, which also suggested a decreased entry rate of water into the eye. The effect of prazosin on IOP was prevented by systemic pretreatment with phentolamine mesylate, an alpha-adrenergic blocking agent, but not by propranolol hydrochloride or atropine sulfate. This was consistent with the known action of prazosin as a postsynaptic alpha-adrenergic blocking agent.

Administration, Topical↗
PubMed1985

[Aqueous humor outflow capacity after argon laser trabeculoplasty. Preliminary report].

In a prospective study of 44 eyes with open angle-glaucoma and 27 with pseudocapsular glaucoma, the aqueous humor outflow facility was controlled for up to 12 months following argon laser trabeculoplasty (ALT). The average increase in the facility of outflow, which was 70% in open-angle glaucoma, was 25% higher in pseudocapsular glaucoma. In successful ALT, this increase in outflow facility was established within the first 20 hours after coagulation and did not decrease during the following year. There were no major complications such as transitory elevations of intraocular pressure, hyphema, or severe uveitis; this fact is interpreted as a result of the authors' technique, in which only the light-pigmented trabecular meshwork is coagulated.

Aqueous Humor↗
PubMed1987

Ciprofloxacin concentrations in human aqueous humor following intravenous administration.

16 patients received an intravenous infusion of 200 mg ciprofloxacin 1, 2, 3 and 6 h, respectively, before cataract extraction. This dosage produced mean aqueous humor levels of 0.165 +/- 0.09 and 0.126 +/- 0.028 microgram/ml after 1 and 3 h, respectively. The mean serum levels were 1.760 +/- 0.873 and 0.854 +/- 0.283 microgram/ml after 1 and 3 h, respectively. These levels are above the minimum inhibitory concentration of ciprofloxacin for sensitive organisms.

Aqueous Humor↗
PubMed2003

The role of protein kinase C in modulation of aqueous humor outflow facility.

The elevated intraocular pressure that is commonly associated with glaucoma is believed to arise due to impairment of trabecular meshwork (TM) function. Although the TM and Schlemm's canal (SC) comprise the major route for aqueous humor outflow, little is known about the potential signaling mechanisms involved in the regulation of aqueous outflow. Based on knowledge regarding the role of protein kinase C (PKC) in vascular biology, we sought to understand the contribution of the PKC pathway towards outflow function by studying the modulation of contractile and morphological characteristics of TM and SC cells. We investigated the involvement of PKC in regulation of myosin light chain (MLC) phosphorylation, formation of actin stress fibers and integrin-ECM adhesions (focal adhesions) in human TM and SC cells and correlated these changes with aqueous outflow facility measured in an enucleated porcine whole eye perfusion model. Expression and distribution of PKC isoforms (alpha and epsilon ) in TM and SC cells and tissues was confirmed by Western blot and immunohistochemical analysis, respectively. Both, pharmacological activators (phorbol-12-myristate 13-acetate (PMA) and phorbol-12,13-dibutyrate (PDBu)) and inhibitors (staurosporine and GF109203X) of PKC were found to induce changes in cell shape (retraction and rounding up) and cytoskeletal organization in human TM and SC cells. While PMA and PDBu produced an increase in formation of actin stress fibers and focal adhesions and in MLC phosphorylation, PKC inhibitors were observed to induce contrasting effects in these cells. Intriguingly, both PDBU and GF109203X caused increases in aqueous outflow facility in the perfusion model. The PKC inhibitor (GF109203X) increased outflow by 46% while the PKC activator (PDBu) only increased outflow by 27%. These results suggest that PKC might play an important role in modulation of aqueous outflow facility by regulating MLC phosphorylation and thereby, the morphological and cytoskeletal characteristics of TM and SC cells.

Actins↗
PubMed1975

Analysis of ascorbate concentration in the aqueous humor by high-pressure liquid chromatography.

A high-pressure liquid chromatography instrument has been used to establish a method for the analyses of ascorbate concentration in aqueous humor. The method detects only the reduced form of ascorbate. The values obtained by this method are very similar to those of the colorimetric method. The ascorbate value in a group of random samples obtained from human glaucoma eyes varied between 3.5 to 31 mg. per cent, independent to blood ascorbate concentration.

Aqueous Humor↗