Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Trabecular Meshwork”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1996

Reduced trabecular meshwork height in juvenile primary open-angle glaucoma.

OBJECTIVE: To compare trabecular meshwork height in a series of patients with juvenile primary open-angle glaucoma (JPOAG) with that in normal control patients. METHODS: Ultrasound biomicroscopy and A-scan biometry were performed on 16 eyes with JPOAG and 24 normal eyes. A radial, perpendicular image in the horizontal temporal meridian detailing the line of Schwalbe, scleral spur, and angle anatomy was obtained for each eye by a single examiner. Trabecular meshwork height was defined as the distance from the scleral spur to the Schwalbe line. RESULTS: Mean patient age (P = .85, t test), refractive error (P = .68), sex distribution (P = .26, Fisher exact test) and axial length (P = .39) were similar between the groups. Mean +/- SE trabecular meshwork heights were 0.36 +/- 0.03 mm (range, 0.19-0.53 mm) for JPOAG and 0.58 +/- 0.02 mm (range, 0.40-0.80 mm) for controls (P < .001). Eyes with greater axial length tended to have larger trabecular meshworks in both groups (P = .012, multivariate regression). A trabecular meshwork height-axial length ratio of 0.021 or less was associated with a significantly increased risk for JPOAG being present (odds ratio, 57; 95% confidence interval, 6.0-541). CONCLUSIONS: The trabecular meshwork is smaller in eyes with JPOAG compared with that in normal eyes. This finding suggests a structural abnormality that may underlie the reduced outflow.

Adolescent↗
PubMed1997

[The effects of pressure on cultured bovine trabecular meshwork cells].

OBJECTIVE: To observe the effects of pressure on trabecular meshwork cells. METHODS: Bovine trabecular meshwork cells were cultured and submitted to different amounts of hydrostatic pressure. Cellular morphology and phagocytic function were observed under inverted phase-contrast microscope, light microscope and electron microscope. RESULTS: Compared with the control group, the cells under 2.0 kPa or 2.67 kPa for 48 hours had no remarkable difference in criteria observed. Those under 4.0 kPa for 24 hours showed slight changes in structure and a mild decrease in phagocytic function. The damage appeared more severe if the pressure was higher or lasted longer. CONCLUSION: Trabecular meshwork cells can only bear pressure below a certain level. They may be destroyed structurally or impaired functionally by pressure over this level.

Animals↗
PubMed1996

Effect of age on superoxide dismutase activity of human trabecular meshwork.

PURPOSE: It has been hypothesized that accelerated aging of the trabecular meshwork, perhaps because of oxidative damage, is involved in the pathogenesis of primary open angle glaucoma. The authors sought to evaluate the effect of donor age on the specific activity of superoxide dismutase and catalase in normal fresh human cadaver trabecular meshwork. METHODS: Total superoxide dismutase and catalase were assayed in tissue extracts generated from fresh human trabecular meshwork. Cadaver tissue was obtained from 19 donors (18 paired) of a wide age range (30 to 91 years). The assays were performed within 6 hours of enucleation and within 36 hours of donor death. Enzyme-specific activities were calculated using protein concentration of the extract as the denominator. RESULTS: Multiple regression analysis modeled with age and time from death until the beginning of the experiment was performed. The specific activity of superoxide dismutase declined with age (P = 0.00022; r2 = 0.67). There was no effect of age on catalase specific activity (P = 0.24; r2 = 0.16). The time from donor death until the beginning of the experiment was not a significant factor (P > 0.28). CONCLUSIONS: The specific activity of superoxide dismutase, but not catalase, demonstrates an age-dependent decline in normal cadaver human trabecular meshwork. The potential role of superoxide dismutase in primary open angle glaucoma, a disorder of the aging trabecular meshwork, warrants further investigation.

Adult↗
PubMed1993

Adenylyl cyclase in human and bovine trabecular meshwork.

PURPOSE: To determine the basic characteristics and responses of adenylyl cyclase in trabecular tissues. Because the second messenger cyclic adenosine monophosphate can lower intraocular pressure by increasing outflow facility, it is of interest to know which signalling pathways stimulating adenylyl cyclase are involved. METHODS: Adenylyl cyclase activity of bovine and human trabecular meshwork membrane fractions and of whole tissue homogenates (bovine) to forskolin, manganese, fluoroaluminate, isoproterenol, prostaglandins (PGE1, PGE2, PGF2 alpha), and vasoactive intestinal peptide, were evaluated. RESULTS: In bovine trabecular meshwork particulate fractions, adenylyl cyclase was stimulated 3.3- and 2.6-fold over basal by 60 and 2 microM forskolin, respectively, 2.2-fold by fluoroaluminate, and 1.5-fold by PGE1 and PGE2, whereas no or a very week response was obtained with PGF2 alpha, isoproterenol, and vasoactive intestinal peptide. PGE1-induced stimulation was dose-dependent and G-protein-dependent, which provides evidence for EP receptor-mediated activation. Whole tissue homogenates of bovine trabecular meshwork did not differ from the particulate fractions. In human trabecular meshwork membrane fractions adenylyl cyclase stimulation was more pronounced, 12.4- and 5.5-fold by 60 and 2 microM forskolin, respectively, 8.2-fold by fluoroaluminate, and 3-fold by PGE1 and PGE2. PGF2 alpha had no effect. Significant stimulation was obtained with isoproterenol (2.8-fold) and with vasoactive intestinal peptide (1.8-fold). CONCLUSIONS: Human and bovine trabecular meshwork can be stimulated at all known activation levels of adenylyl cyclase. The human adenylyl cyclase system, especially receptor-coupled activity, is more sensitive than that of bovines. Beta-adrenoreceptor stimulation, PGE2, and vasoactive intestinal peptide may have a local physiologic function by activating adenylyl cyclase in human trabecular meshwork.

Adenylyl Cyclases↗
PubMed2001

Effect of transforming growth factor-beta 2 on phagocytosis in cultured bovine trabecular meshwork cells.

The effect of transforming growth factor-beta 2 (TGF-beta 2) on phagocytosis in bovine trabecular meshwork cells in vitro was investigated. After the cultured bovine trabecular meshwork cells were treated with 0 ng/ml, 0.32 ng/ml, 1 ng/ml, 3.2 ng/ml TGF-beta 2 for 24 h, latex beads were added into the incubation medium, and the numbers of the latex beads in 20 adjacent cells were counted under a microscope 24 h later, after treatment with Wright's stain. Our results showed that the average numbers of the latex beads in the trabecular meshwork cells treated with TGF-beta 2 of different concentrations were 53.1 +/- 1.7 beads/cell, 56.4 +/- 2.9 beads/cell and 77.9 +/- 6.5 beads/cell respectively, in comparison with 45.5 +/- 3.3 beads/cell of the control group. TGF-beta 2 significantly increased the number of the latex beads phagocytosed by cultured bovine trabecular meshwork cells in a dose-dependent manner. TGF-beta 2 could promote the phagocytosis of bovine trabecular meshwork cells in vitro. It may be involved in the cellularity decrease of the trabecular meshwork in the patients of primary open angle glaucoma through promoting the phagocytosis of trabecular meshwork cells.

Animals↗
PubMed1999

Effects of glucocorticoids on the trabecular meshwork: towards a better understanding of glaucoma.

Glucocorticoid effects on the human trabecular meshwork can be used as a model system in which to study glaucomatous damage to the trabecular meshwork. One of the most important risk factors for glaucoma is an elevated intraocular pressure. The administration of glucocorticoids also can cause elevated intraocular pressure in some individuals. In addition, there is suggestive evidence linking glucocorticoids with the development of glaucoma. Glucocorticoids cause multiple effects on the human trabecular meshwork including changes in extracellular matrix metabolism, organisation of the cytoskeleton, and changes in gene expression and cell function. New discoveries on the molecular mechanisms of glucocorticoid receptor action provide new opportunities to study the possible role of this receptor in the development of glaucoma. For example, alternate spliced forms of the glucocorticoid receptor, glucocorticoid receptor response element half-sites, numerous modulatory factors, and direct effects of nuclear transcription factors have been recently described. Other recent information has shown that the new glaucoma gene (GLC1A/myocilin) is induced in the human trabecular meshwork by glucocorticoids. Although the exact function of myocilin is currently unknown, it offers the opportunity to dissect the molecular pathways regulating aqueous humor outflow. Future challenges include determining (1) which glucocorticoid effects in the human trabecular meshwork are responsible for elevated intraocular pressure; and (2) the significance of these findings to the development of glaucoma.

Animals↗
PubMed1980

Preliminary observations on human trabecular meshwork cells in vitro.

This report presents our preliminary observations on the trabecular meshwork from human eyes up to 5 days post-mortem in tissue culture. Satisfactory primary cultures were obtained from about 20% of the 423 explants which were investigated. The period prior to growth was from 4 days to 4 weeks and from the appearance of the initial outgrowth it took 25 to 30 days to reach maximum cellular spread within the culture chambers. The progress of the explant and the spreading of the trabecular meshwork cells was monitored by phase-contrast microscopy, time-lapse cinephotomicrography, light microscopy, transmission electron microscopy, scanning electron microscopy and autoradiography (using tritiated thymidine). On the basis of their ultrastructural appearance the cultured meshwork cells seems to be metabolically active. Their cytoplasm contained abundant rough endoplasmic reticulum, many mitochondria, a well developed Golgi apparatus and many coated and uncoated micropinosomes. However, even in short-term culture the trabecular meshwork cells had adapted to the artificial environment of our system and no longer resembled "normal" trabecular meshwork cells as seen in vivo. Since trabecular meshwork cells can quickly adapt their morphology in a culture environment and because the adult human meshwork contains a significant population of non-trabecular cells, the value of long term culture as a means of investigating the cellular activity of the normal and glaucomatous outflow system must be open to question.

Culture Techniques↗
PubMedDate not supplied

Morphological evaluation of the conjunctiva and the trabecular meshwork incubated with Proline-3H.

It is well known that the trabecular meshwork is a complex structure in the shape of collagen and like-elastic fibers dipped in amorfous matrix. Previous researches have been showed that in the glaucoma disease there is a sclerosis in the lamellae of the trabecular meshwork and an increase in extracellular material. In order to add informations to complex and highly organized trabecular meshwork and its role in the glaucoma disease, 12 surgical specimens of trabecular meshwork and conjunctival tissue from patients suffering from chronic simple glaucoma and undergone medical therapy have been examined. The fragments have been immediately incubated with Proline 3H for 45 minutes; after this period they have been fixed and included. The results have been showed the presence of the fibroblast cells engaged to pick up radioactive Proline. The collagen synthesis has been happened in the trabecular meshwork and in this study there is not demonstration of collagenic material coming from surrounding structures.

Conjunctiva↗
PubMed2003

The matricellular protein SPARC is expressed in human trabecular meshwork.

PURPOSE: This investigation was undertaken to determine whether the matricellular protein SPARC is expressed in the human trabecular meshwork (TM) and cultured human trabecular meshwork cells. METHODS: Human donor trabecular meshwork and cultured cells obtained from trabecular meshwork were used in this study. Total RNA was obtained from TM and cultured TM endothelial cells, and RT-PCR was done with primers specific for SPARC. Western blotting was performed on donor TMs using an anti-SPARC monoclonal antibody prepared against rHuSPARC. Confocal microscopy was used to determine the distribution of SPARC in human anterior segments, and immunofluorescence on cultured TM cells was performed with the anti-SPARC antibody. RESULTS: SPARC mRNA was expressed both in TM and in cultured TM cells. Immunoblotting for SPARC showed a doublet with a molecular mass approximately 43 kDa. The ratio of the doublet bands varied with each of the samples; some of the cultured cells and the tissue samples exhibited more of the upper band, and other cultured cells contained almost equal amounts of the two bands. The upper band was shown to be a glycosylated form of SPARC. Immunofluorescence showed that SPARC was expressed in the cultured TM, and confocal microscopy with the anti-SPARC antibody demonstrated the presence of this protein in the TM and in other tissues in the anterior segment. CONCLUSIONS: Our data conclusively show that SPARC mRNA and protein are present in non-glaucomatous TM tissue and in cultured TM cells. Because of its effect on matrix metalloproteinases, SPARC may play a role in the regulation of intraocular pressure.

Adolescent↗
PubMed1982

Fibronectin production by cultured human trabecular meshwork cells.

Postmortem explants of human trabecular meshwork from 23 eyebank eyes had a growth rate of 32% (71/160) cultures, with 8% (12) showing abundant cellular spread. One hundred percent confluency was achieved with eyes from donors of 11 to 40 years of age. One of the cultures grew profusely and we were able to study it through eight passages in culture. This culture had the morphologic characteristics described by Polansky et al. for cultured human trabecular meshwork cells. A sensitive radioimmunoassay for fibronectin in tissue culture supernatant showed an increase in fibronectin secretion over a 96 hr period, with a characteristic shift-down response occurring between 24 and 48 hr postmedia change. Three of four cultures showed the presence of laminin, a basement membrane protein, establishing that the cells are not fibroblasts.

Adolescent↗
PubMed2001

Activation of extracellular signal-regulated kinase in trabecular meshwork cells.

A number of different agents, such as growth factors, cytokines and phorbol esters have been shown to modulate trabecular meshwork cell function. These studies were designed to evaluate the role extracellular signal-regulated kinase (ERK) pathway plays in mediating the responses to platelet-derived growth factor-BB (PDGF-BB) and phorbol 12-myristate 13-acetate (PMA) in trabecular meshwork cells. The human trabecular meshwork cell line, HTM-3, and the bovine trabecular meshwork (BTM) cells were treated with either PDGF-BB or PMA and the activation of ERK 1/2 evaluated. The effects of the MAP kinase kinase (MEK) inhibitor U0126, and the PKC inhibitor chelerythrine on ERK 1/2 were also determined. In a separate group of experiments, cells were treated with PDGF-BB or PMA and the secretion of matrix metalloproteinase-2 (MMP-2) evaluated. The addition of PDGF-BB or PMA produced time- and dose-dependent activation of ERK 1/2. Pretreatment with U0126 or chelerythrine significantly reduced ERK 1/2 activation induced by PDGF-BB or PMA. The addition of PDGF-BB or PMA stimulated the secretion of MMP-2. This secretory response was inhibited by pretreatment with the MEK inhibitor U0126. In trabecular meshwork cells, PDGF-BB and PMA activate ERK 1/2 by a PKC-dependent mechanism. Activation of ERK 1/2 by these agents in trabecular meshwork cells leads to the secretion of MMP-2. These studies provide evidence that ERK pathway is an important mechanism for integrating various signals that regulate trabecular function.

Alkaloids↗
PubMed1992

Effect of histamine on signal transduction in cultured human trabecular meshwork cells.

Stimulation of cultured human trabecular meshwork cells by histamine caused time and dose related increases in inositol phosphates and intracellular free calcium. The increase in inositol trisphosphate (IP3) was immediate and calcium independent while that of inositol monophosphate (IP1) was gradual and calcium dependent. The rise in intracellular calcium was also rapid and occurred as a result of mobilization from intracellular stores and influx from external medium. Histamine also caused time and concentration related de novo synthesis of inositol phospholipids. Mepyramine but not cimetidine inhibited the action of histamine. These results indicate that histamine, via H1 receptor, evokes an early hydrolysis of inositol phospholipids and increase in intracellular free calcium, signals which may be involved with the function of the trabecular meshwork cells.

Adult↗
PubMed1987

Age-related changes in protein profiles of the normal human trabecular meshwork.

The protein profile of the trabecular meshwork from 44 normal human eyes of various ages, ranging from 5 months to 87 years, was investigated by using sodium dodecyl sulfate-polyacrylamide-gel (SDS-PAGE) electrophoresis and a highly sensitive silver-stain technique. Samples from each eye were analysed individually to avoid anomalies that may occur with tissue pooling. More than 20 protein bands were consistently visible at all ages and varied in molecular weight from 20,000 to 290,000 MW. The shifts which occurred in band prominence with increasing age included a consistent decrease in the intensity of bands at MWs 42,000 (tentatively identified as G-actin) and 58,000; a noticeable increase in the intensity of the bands at MWs 140,000 and 160,000 that correspond to alpha I and II components of type IV collagen; and a gradual disappearance of a faint band at MW 68,000 in eyes older than 31 years. Our study shows that molecular aging does occur in the trabecular meshwork. The data presented also provides a basis for comparison of the polypeptide alterations that may occur in primary open-angle glaucoma and in other disease processes.

Adolescent↗
PubMed2001

A study of toxicity of 5-fluorouracil on bovine trabecular meshwork cells in vitro.

In order to explore whether the conventional use of 5-fluorouracil (5-Fu) had any toxic effects on trabecular meshwork cells, bovine trabecular meshwork cells were cultured in vitro and exposed to 5-Fu at different concentrations. The cellular morphology, ultrastructure, mortality and phagocytosis were studied under light microscopy, transmission electron microscopy and methods of Wright's stain. It was found that the toxic effects of 5-Fu on the cells were in a dose-dependent mode. 1 x 10(-1) mg/ml of 5-Fu caused a large part of cells rounded up, while 1 x 10(-2) mg/ml of the drug only a rough appearance of the cell surface. Exposure to 1 x 10(-2) mg/ml of 5-Fu made mitochrone swollen and rough endoplasmic reticulum enlarged, with the cell mortality being 50.5%. The latex microspheres engulfed in cytoplasm in cells receiving 1 x 10(-1) and 1 x 10(-2) mg/ml of 5-Fu were significantly decreased as compared with those in the control group (P < 0.01). It was concluded that the safe concentration of 5-Fu on bovine trabecular meshwork cells was 1 x 10(-2) mg/ml and the conventional dosage of 5-Fu in clinical practice would not cause injury to trabecular meshwork cells.

Animals↗
PubMed2000

Morphological variability of the trabecular meshwork in glaucoma patients: implications for non-perforating glaucoma surgery.

BACKGROUND/AIMS: Morphological variability of the trabecular meshwork could be of considerable importance for the proper intraoperative outcome of non-perforating antiglaucomatous surgery, such as deep sclerectomy and viscocanalostomy. The aim of this study was therefore to assess qualitative and quantitative characteristics of the trabecular meshwork in glaucoma patients undergoing trabeculectomy. METHODS: Trabeculectomy specimens from 177 glaucoma patients were prepared for light microscopy; 100 specimens were found to be suitable for qualitative assessment and quantitative computerised image analysis; measurements were taken of the meridional diameter of Schlemm's canal as well as the thickness of the trabecular meshwork at different positions. RESULTS: The mean meridional diameter of Schlemm's canal was 290 microm with the smallest values in the young patients with infantile and secondary glaucomas. the thickness of the trabecular meshwork ranged between 50-70 microm in the anterior region and between 100-130 microm for the posterior portion. The thickness of the anterior meshwork significantly decreased with age. The pigmentation of excised trabecular meshwork was found to be weak or even lacking in 68 patients. In 20 glaucoma patients the uveal meshwork was covered by an endothelial layer. CONCLUSIONS: From the morphological point of view the risk of inadvertent perforation during deep sclerectomy in older, white glaucoma patients should be taken into account even by an experienced surgeon, because the anterior meshwork in these cases is very thin and trabecular pigmentation that can be used as a topographic landmark is often lacking. The functional success of non-perforating glaucoma surgery in many patients may be limited by endothelial covering of the trabecular meshwork.

Adolescent↗
PubMed1984

Glutathione peroxidase of calf trabecular meshwork.

Glutathione peroxidase was extracted from calf trabecular meshwork. The kinetics of this enzyme were examined, varying the substrates hydrogen peroxide (H2O2), tert- butylhydroperoxide ( tBHP ), and glutathione. The activity of the enzyme in nonpurified homogenates was 596 nmole H2O2 reduced/min/gm wet weight and 680 nmole tBHP reduced/min/gm wet weight (27-28 nmole peroxide reduced/min/mg protein). The apparent Michaelis--Menten constants for H2O2, tBHP , and GSH were 0.012, 0.102, and 2.89 mM, respectively. These data, together with published levels of glutathione in trabecular meshwork, suggest that the trabecular endothelial cell actively detoxifies H2O2.

Animals↗
PubMed1996

Effects of muscarinic agents on cultured human trabecular meshwork cells.

Intracellular calcium measurements were performed in cultured human trabecular meshwork cells preloaded with the cell permeant dye fura 2-AM. Fluctuations in calcium levels were then monitored with microscope-based ratio fluorometry. Carbachol increased intracellular calcium in a dose-dependent manner; as did oxotremorine-M, aceclidine, and pilocarpine. Carbachol's effect was blocked by the non-selective muscarinic antagonist atropine, as well as by muscarinic receptor subtype-selective antagonists such as pirenzepine (M1-selective), p-fHHSiD (M3-selective), and 4-DAMP (M1, M3 subtypes). Rank order of potencies for the antagonists' effects was atropine = 4-DAMP > p-fHHSiD > pirenzepine, a profile suggesting that the M3 receptor subtype is essential in the carbachol effect. Phospholipase C activity was estimated via measurement of total production of inositol phosphates in cultured human trabecular meshwork cells pre-exposed to 3H-myoinositol. In these cells, carbachol also stimulated phosphoinositide production in a dose-dependent manner, and an antagonist profile similar to that seen for calcium response was obtained when carbachol was used as the effector. The data indicate that muscarinic effects on cultured human trabecular meshwork calcium mobilization and phospholipase C activity are mediated by an M3-like receptor subtype. Therefore, the muscarinic M3 receptor may play a role in trabecular meshwork cell function(s).

Adolescent↗
PubMed2004

Apoptosis of human trabecular meshwork cells induced by transforming growth factor-beta2 in vitro.

Whether transforming growth factor-beta2 (TGF-beta2) induces apoptosis of human trabecular meshwork cells was investigated in vitro. Cultured 3-5 passage human trabecular meshwork cells were treated with 0 (control), 0.32, 1, 3.2 ng/ml TGF-beta2 for 48 h and divided into control group and experimental group. The apoptosis of human trabecular meshwork cells was examined by transmission electron microscopy, TUNEL technique and flow cytometry. The results showed characteristic morphologic changes of apoptotic cells were observed under transmission electron microscopy. DNA fragmentation of human trabecular meshwork cells was found by TUNEL technique. Quantitative analysis of flow cytometry showed that percentages of apoptotic human trabecular meshwork cells were (2.79 +/- 0.44)%, (4.43 +/- 1.17)% and (9.60 +/- 2.05)% respectively with different concentrations [1 ng/ml (P<0.05), 3.2 ng/ml (P<0.01)] of TGF-beta2 with the difference being significant between experimental group and control group [(1.41 +/- 0.34)%]. It was concluded that TGF-beta2 can induce apoptosis of human trabecular meshwork cells in vitro and may be involved in the decrease of trabecular meshwork cells in the patients with primary open angle glaucoma and aging of normal people.

Apoptosis↗