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 19 recordsLinked to original sources
PubMed1992

Ascorbic acid modulates collagen type I gene expression by cells from an eye tissue--trabecular meshwork.

The trabecular meshwork, a specialized tissue in the anterior chamber of the eye, plays a major role in the regulation of aqueous humor outflow. We studied the effects of ascorbic acid, a significant component in the aqueous humor, on gene expression of type I collagen in cultures of bovine trabecular meshwork cells. These cells were plated for 6 days, exposed to ascorbic acid in concentrations of 100, 250 and 500 micrograms/ml for 3 days and labeled with (3H)proline for the last 24 hrs. Cultures that did not receive ascorbic acid served as controls. Bacterial collagenase assays showed enhanced incorporation of (3H)proline into collagenous proteins in cultures treated with 100 and 250 micrograms/ml of ascorbic acid. Gel electrophoresis and fluorography revealed that ascorbic acid caused a 2.6- to 4.9-fold increase in production of alpha 1 (I) and alpha 2(I) collagen chains by trabecular meshwork cells. Such an increase was found, using a cDNA probe specific for pro alpha 1(I) chains, to be accompanied by an increase in steady-state mRNA levels. Similar findings were also yielded from in situ hybridization experiments. These results, coupled with previously demonstrated ascorbate-induced effects on glycosaminoglycan, fibronectin and laminin synthesis, suggest that ascorbic acid is a key mediator of the extracellular matrix production by trabecular meshwork cells. Fluctuations in its concentration may lead to alterations in the makeup and assembly of matrices underlying the cells.

Animals↗
PubMed1991

Extracellular materials in the endothelial meshwork of organcultured human trabecular meshwork. Morphologic and morphometric study.

Twenty-three normal cadaver eyes were used in this study. Eight trabecular meshwork explants were dissected at 45-degree intervals from a 77-year-old donor eye and cultured for 2 weeks for studying circumferential differences in the amount of extracellular materials in the endothelial meshwork. One trabecular meshwork explant was dissected from each of 22 individual eyes (age range: 64-89 years) and cultured for 2 weeks to study the effect of age on the amount of the extracellular materials. Then, 5 consecutive electron micrographs in the endothelial meshwork were obtained from the individual specimens and subjected to morphometric studies. In the endothelial meshwork, the results revealed: (1) no statistically significant circumferential differences in the amount of extracellular materials and (2) no statistically significant changes associated with aging in the amount of these materials.

Cell Count↗
PubMed1989

Prostaglandin production by cultured cynomolgus monkey trabecular meshwork cells.

Monkey trabecular meshwork (MTM) cells synthesize a variety of prostaglandins, including large amounts of prostaglandin E2 (PGE2) and smaller amounts of 6-keto-PGF1 alpha and PGF2 alpha. The predominance of PGE2 production by the MTM cells is similar to that observed in human trabecular meshwork cells. In contrast, the relative amounts of 6-keto-PGF1 alpha and PGF2 alpha were reversed compared with the human cells. The MTM cells produced increased amounts of PGE2 in response to treatment with bradykinin, platelet activating factor, and A-23187. Dexamethasone caused a dose-dependent inhibition of PGE2 production with 50% inhibition by 10(-8) M, although this response was variable.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Electrical and morphological evidence for heterogeneous populations of cultured bovine trabecular meshwork cells.

Although trabecular meshwork cells are presumed to play an important role in determining ocular aqueous outflow resistance, little is known about their membrane transport characteristics. As in vivo access by microelectrodes is difficult, we used cell culture techniques to facilitate membrane voltage recording from cultured bovine trabecular meshwork cells. Phase-contrast microscopy revealed the presence of epithelial-like and spindle-shaped cell types. The mean membrane voltage for epithelial cells was -49.7 +/- 0.8 mV (S.E.M., n = 143) and for spindle cells was -70.9 +/- 1.9 mV (S.E.M., n = 48). These cells possess an electrogenic Na+/K(+)-ATPase and a K+ conductance. K transference numbers (tk) for [K+] from 5 to 80 mM were 0.50 for epithelial cells and 0.71 for spindle cells. The epithelial cells lack the electrogenic Na+/HCO3-symport, thereby enabling their differentiation from corneal endothelial cells and confirming previous reports of differences between these cell types. A proportion of spindle cells demonstrated spontaneous and induced fluctuations of membrane voltage. One millimolar Ba2+ (n = 9) induced an immediate depolarization of membrane voltage, with the onset of 'overshooting' action potentials, which were dependent on extracellular Ca2+ and Na+ but were not blocked by tetrodotoxin, 10(-6) M. Spindle cells showed parallel alignment of intracellular smooth muscle specific alpha-isoactin filaments, whereas epithelial cells showed specks of non-fibrous staining. Electron microscopy revealed that epithelial cells had the characteristics of metabolically active cells, with few intermediate filaments (10-12 nm) and microfilaments (6-7 nm) and short cytoplasmic processes. Spindle cells had long cytoplasmic processes and abundant intermediate- and microfilaments. These data provide further evidence for multiple bovine trabecular cell types. The smooth muscle-like spindle cell may represent the previously proposed contractile element of the angle and its action could conceivably alter ocular outflow resistance.

Actins↗
PubMed1991

Murine trabecular meshwork cells in tissue culture.

Trabecular meshwork cells from an inbred strain of mice (A/J) were established in tissue culture. Within 1 hour of enucleation, tissue containing the cornea and the chamber angle was excised and placed in tissue culture. Two to five days later, three cell types grew from the explants. Two of these cell types, corneal endothelium and fibroblasts, grew together, with the fibroblasts preferentially spreading on top of the endothelial cells. The trabecular meshwork cells extended from the explant as a distinct morphological type. The corneal endothelium and its associated fibroblasts were then removed from the culture flask with a sterile cotton swab, leaving a monolayer of pure trabecular meshwork cells. These cells required 3-4 weeks to reach confluency and could be passaged five times. They were actively phagocytic in culture and exhibited immunoreactivity to antibodies against two extracellular matrix components, laminin and collagen type IV. Mouse trabecular meshwork cells also expressed receptors for acetylated low-density lipoprotein, a property shared by trabecular meshwork cells derived from other species. The availability of trabecular meshwork cells from an inbred strain of mice will facilitate future in vivo functional studies of these cells in a syngeneic system, as well as investigations of potential immunoregulatory properties of the trabecular meshwork.

Animals↗
PubMed1986

Innervation of trabecular meshwork.

The innervation of the trabecular meshwork of the anterior chamber angle in monkey eyes was studied by transmission and scanning electron microscopy. According to the transmission electron microscopic examination, the nerve terminals in the trabecular meshwork mostly contained dense core vesicles after treatment with 5-hydroxydopamine and thus were identified as the adrenergic nerve terminals. Regarding the mode of ending of the nerve terminals in the trabecular meshwork, it was divided into three types from the positional relationship of the nerve terminals with the endothelial cells in the trabecular meshwork. Type I nerve terminals are naked and they form synaptic contact with endothelial cells of the trabecular sheets of the uveal and corneoscleral meshwork. Type II nerve terminals are located in the trabecular sheets of the uveal and corneoscleral meshwork and in the endothelial meshwork, and partly surrounded by the Schwann cell processes. This type of nerve terminals end as free terminals without a constant relation to endothelial cells of the trabecular meshwork. Type III nerve terminals usually not surrounded by the Schwann cell processes are observed on the free surface of the endothelium of the trabecular sheets facing the aqueous humor. The incidence of these three types of nerve terminals was the highest in type II followed by type III. Type I nerve terminals were very rare. When the morphological characteristics of the trabecular meshwork are considered, the transmitter released from type II and type III nerve terminals enter the aqueous humor and perhaps affects the aqueous outflow area to control the intraocular pressure, as judged from the flow of aqueous humor.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Expression of HLA class I and II antigens on cells of the human trabecular meshwork.

Human corneoscleral tissue containing trabecular meshwork and cultured human trabecular cells were examined for HLA-ABC (class I) and HLA-DR (class II) antigens of the major histocompatibility complex using an indirect immunofluorescence assay. Class I antigens were detected in the trabecular meshwork on frozen sections and on cultured trabecular cells. Class II antigens were constitutively expressed on some, but not all, cells within the trabecular meshwork. Many more cells could be induced to express class II antigens by pre-incubation in human gamma interferon. Cultured trabecular cells did not express class II antigens constitutively, but expression could be induced by gamma interferon. This study suggests that, in addition to Langerhans' cells at the limbus, other cell types within the anterior segment express major histocompatibility complex-encoded class II antigens either constitutively or inducibly. These cells may be important for the initiation and regulation of ocular immunity.

Adult↗
PubMed1986

Establishment of calf trabecular meshwork cell cultures.

Trabecular meshwork cell cultures have been grown from excised calf aqueous outflow pathway tissue using two different methods. In one method, tissue explants were placed directly in culture dishes and primary cultures were established by those cells migrating from the tissue. In the second method, a cell suspension was generated by incubating trabecular tissue strips with 0.1% pronase, and the washed cells were used to seed primary cultures. The cell cultures generated by each method appeared to progress through morphological and biochemical changes characteristic of the cell type, although at different respective rates. Comparisons of the cell morphologies, biosynthetic activities, and growth characteristics of the respective subcultures suggested that similar cell populations were obtained by each method. These studies further suggested that sufficient quantities of calf trabecular cells could be grown in culture to permit biochemical and pharmacological studies of trabecular-cell metabolism.

Animals↗
PubMed1979

Glaucoma associated with precipitates on the trabecular meshwork.

Precipitates on the trabecular meshwork may be the only sign of ocular inflammation. Fourteen patients who had glaucoma associated with precipitates on the trabecular meshwork and minimal or no other signs of ocular inflammation did not respond to usual antiglaucoma therapy. Treatment with topical steroids eliminated the precipitates and lowered the intraocular pressure. Careful gonioscopy is the key to accurate diagnosis.

Acetazolamide↗
PubMed1991

[The development of human trabecular meshwork].

The fetal development of the trabecular meshwork of the human eye was quantitatively studied by light and electron microscopy. From the 20th fetal week onward, the progressive thickening of the trabecular meshwork was achieved mainly by the widening of intertrabecular spaces, whereas the thickness and the number of trabeculae were almost constant. Significant alterations in the number of trabecular meshwork cells did not occur with development. However, a decrease in trabecular meshwork cellularity occurred by the widening of intertrabecular spaces. As development proceeded, there was an increase in the proportion of the width of the posterior trabecular meshwork, which is the main site of aqueous drainage, in accordance with the increase of aqueous production.

Cell Count↗
PubMed1988

Human trabecular meshwork organ culture.

Human trabecular meshwork obtained from postmortem eyes was maintained in organ culture condition up to 12 weeks. The explants were dissected into specimens of three different sizes. Types 1 and 2 specimens were larger than 4 mm square and 1 mm thick, and type 3 specimens were about 1 mm3. Each specimen was placed in a depression made in the center of an agar block and the block was placed in a plastic culture dish. The space between the agar block and the culture dish was filled with liquid medium consisting of MEM Eagle supplemented with 10% fetal bovine serum, 10% chick embryo extract and 200 U/ml penicillin G. Afterwards, the explant was incubated in 5% CO2 with 100% humidity. Types 1 and 2 specimens maintained a normal appearance on electron microscopy during the entire 12 weeks of culture, while type 3 specimens showed marked cellular activation and cell loss soon after explantation. Morphometric studies regarding cell number in sections for light microscopy obtained from types 1 and 2 specimens revealed good preservation of trabecular cells during the 12 weeks of culture. Our culture system may be useful in investigating the direct effects produced on human trabecular meshwork by photocoagulation and various agents, for example anti-glaucoma drugs, steroids and viscoelastic materials.

Cadaver↗
PubMed1991

Differential smooth muscle-like contractile properties of trabecular meshwork and ciliary muscle.

The contractile properties of bovine trabecular meshwork and ciliary muscle strips were investigated using an electromagnetic force-length transducer for isometric force measurements. Acetylcholine, pilocarpine and aceclidine administration resulted in dose-dependent contractions of trabecular meshwork and ciliary muscle. Absolute forces were approximately 10 times larger in ciliary muscle than in trabecular meshwork. Maximal force evoked by aceclidine (5 x 10(-5) M), when compared to the pilocarpine (5 x 10(-5) M) response, was significantly higher in trabecular meshwork than in ciliary muscle. The results were 172.5 +/- 12.6% (n = 7) and 138.9 +/- 4.0% (n = 8, P less than 0.05), respectively. Depolarization induced by raised external potassium (120 mM), when compared to the acetylcholine response (10(-3) M), resulted in a small contraction of 19.3 +/- 4.2% in trabecular meshwork (n = 5), and of 59.0 +/- 13.7% in ciliary muscle (n = 4, P less than 0.01). Both responses were inhibited by atropine (10(-5) M). The differential potassium effect may be explained by the large number of cholinergic nerve endings in ciliary muscle as compared to trabecular meshwork tissue. Recently, a dissociation between the effects of aceclidine on outflow resistance and accommodation has been described. Our data are consistent with these observations and provide evidence for a direct role of trabecular meshwork contractility in aqueous outflow regulation.

Acetylcholine↗
PubMed1987

Lysosomal enzyme activities in cultured trabecular-meshwork cells.

We examined the lysosomal enzyme levels in cultured trabecular meshwork cells. Histochemical studies revealed that bovine trabecular meshwork cells stained prominently for acid lipase, acid phosphatase, and acid esterase activities. Following phagocytic challenges, such as incubations with latex microspheres or zymosan particles, lysosomal enzyme staining was visibly enhanced. The uptake of foreign particles by trabecular-meshwork cells was evident. Data from biochemical assays for acid lipase, cholesteryl esterase, and acid esterase confirmed the histochemical findings. These results indicate that trabecular meshwork cells are actively phagocytic in culture and that lysosomal enzyme levels in these cells may be modulated by phagocytic challenge.

Acid Phosphatase↗
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↗
PubMed1988

Monkey trabecular meshwork cells in culture: growth, morphologic, and biochemical characteristics.

We established tissue cultures of trabecular meshwork cells from cynomolgus monkey eyes. The cultures were initiated within 4 h of enucleation on Falcon Primaria flasks. Using medium containing 10% fetal bovine serum and 5% calf serum, trabecular meshwork cells could be grown for up to eight passages without additional growth factors. The growth pattern and cell morphology were distinct from those seen in fibroblastic or endothelial cultures derived from neighboring tissues. Ultrastructurally, our cells showed the characteristics of trabecular meshwork cells, exhibiting prominent basement membranes, intercellular junctions, pinocytotic vesicles, microvillous projections, and branched cell extensions. These cells were grown mostly as monolayers. However, they also appeared to form multi-layered arrays in densely confluent areas when plated at a high density. The extracellular matrix material was surrounded by cells and cell processes, simulating in vivo trabecular beam formation. Radiolabeling experiments demonstrated that our trabecular meshwork cells had the capacity to produce collagen. These results indicated that our cultured cells retain many in vivo characteristics and may be used for various biologic studies of trabecular meshwork.

Animals↗
PubMed1988

Effects of ascorbic acid on trabecular meshwork cells in culture.

We examined the effects of ascorbic acid on trabecular meshwork cells in culture. Bovine trabecular meshwork cells were plated for 6 days and were exposed to media containing either no ascorbic acid or ascorbic acid in the following concentrations for 24 hr: 50-, 100-, 500-, and 750 micrograms ml-1. Fresh media were then added and incubation was continued for an additional 24 hr. The cell number was subsequently determined for the effects of the various concentrations of ascorbic acid on cell growth. In a parallel experiment, cells were labeled with [35S] sulfate (50 microCi ml-1) and [3H]glucosamine (15 microCi ml-1) for 24 hr with or without ascorbic acid for glycosaminoglycan studies. Results indicated that ascorbic acid stimulated the trabecular cell growth in culture at concentrations of 50-, 100-, and 250 micrograms ml-1. However, at 750 micrograms ml-1, cell growth was inhibited. In addition, cells exposed to 100 micrograms ml-1 of ascorbic acid demonstrated increased incorporation of [3H]glucosamine and [35S]sulfate; enhancement of incorporation of [35S]sulfate was also noted at 250 micrograms ml-1. Incorporation of labels was otherwise either unchanged or retarded at other concentrations. These data suggest that the ascorbic acid level in the aqueous humour may influence trabecular meshwork cell metabolism.

Animals↗