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Biomedical subjects

I Grierson

Publications and source records attributed to I Grierson.

At least 91 records · Page 5Linked to original sources
PubMed1989

Morphological effects of argon laser trabeculoplasty upon the glaucomatous human meshwork.

Thirty four trabeculectomy specimens from open angle glaucoma patients who had under argon laser trabeculoplasty as part of their treatment, were studied by scanning electron microscopy. Three of these were also examined by transmission electron microscopy. The intervals between laser therapy and surgery ranged from one month to five years. A sub-group consisted of six patients who had received laser treatment on more than one occasion prior to surgery. Electron microscopy revealed distortion of trabecular beams, loss of trabecular endothelial cells and the development of a cellular sheet extending from the region of Schwalbe's line and covering the anterior surfaces of the anterior portion of the uveal meshwork. The sheet occluded the trabecular spaces of the region; thus, when extensive, contributing to laser trabeculoplasty failure. It is concluded that argon laser trabeculoplasty induces a repair process, in the form of repopulating a cellular deficient meshwork, but which can become detrimental as a consequence of its success.

Adult↗
PubMed1989

Retinal patching: a new approach to the management of selected retinal breaks.

Restoration of retinal continuity by a patching technique is proposed as a new means of treating selected rhegmatogenous retinal detachments where established techniques frequently fail. The patch consists of a substrate and adhesive applied to the inner surface of the retina surrounding the retinal break. Bovine eye cup experiments have been performed to explore the effectiveness of a range of adhesives, and cyanoacrylates and Tisseel have been found to be effective. Studies of these adhesives on confluent cultures of bovine retinal pigment epithelial cells and glia revealed temporary cyanoacrylate toxicity and stimulation of proliferation by Tisseel. Substrate biocompatability was investigated by observing the growth of cells on various substrates in tissue culture; biological substrates such as lens capsule supported cell growth whereas synthetic membranes only did so if pretreated with fibronectin.

Animals↗
PubMed1989

Cellular components of subretinal membranes in proliferative vitreoretinopathy.

To determine the cellular composition of subretinal membranes in proliferative vitreoretinopathy, surgically excised membranes were studied using electron microscopic and immunohistochemical procedures. Light microscopic immunohistochemistry was found to be superior to conventional electron microscopy as a means of evaluating the relative contributions of retinal pigment epithelium and glia to subretinal membranes. The cells of subretinal membranes chiefly comprised retinal pigment epithelium while glial cells were either absent or contributed only a minor component. It is proposed that the clinical properties of subretinal membranes in proliferative vitreoretinopathy derive from their retinal pigment epithelial cell element.

Glial Fibrillary Acidic Protein↗
PubMed1989

Taxol, cytochalasin B and colchicine effects on fibroblast migration and contraction: a role in glaucoma filtration surgery?

Migration and contraction are fibroblast activities in scar tissue formation which may contribute towards the failure of trabeculectomies. We attempted to modify the migration and contraction of Tenon's capsule fibroblasts in vitro using the drugs taxol, cytochalasin B and colchicine. Migration assays were conducted in 48-well micro-chemotaxis chambers, using rabbit aqueous humour which has been previously identified as a powerful chemoattractant for Tenon's fibroblasts, and fibronectin as the stimuli for migration. All three drugs inhibited the migration of fibroblasts to both fibronectin and aqueous humour, with maximal activity seen at 10(-6)M (taxol), 10(-5)M (cytochalasin B), and 10(-3) M (colchicine). In a single cell contractile assay in which contraction of whole fibroblasts was initiated with exogenous adenosine triphosphate (ATP), taxol and colchicine showed anticontractile activity, maximal at 10(-5)M and 10(-3)M respectively, but cytochalasin B was ineffective. The significance of the activities of these drugs in relation to their proposed use for improving the success of trabeculectomies is discussed.

Actins↗
PubMed1989

Wound healing in an animal model of glaucoma fistulizing surgery in the rabbit.

We developed a model of glaucoma fistulizing surgery in the rabbit. As is the case with wound healing in general, there was inflammation followed by repair. The sclerostomy and bleb closed due to bulk filling by granulation tissue and contraction by migratory fibroblasts (observed at three days) and by myofibroblasts (observed at ten and 17 days). Fifty-eight percent of blebs had collapsed by ten days, and 94% by 17 days. The fibroblasts were migrating from the episcleral tissues, from the epimysium of the superior rectus, and from subconjunctival connective tissue. Intraocular pressure and facility of aqueous outflow were measured, but we concluded that intraocular pressure is not a reliable indicator of bleb function or of a patent sclerostomy in this model.

Animals↗
PubMed1988

Exogenous ATP causes the contraction of intact fibroblasts in vitro.

The contraction of intact fibroblasts was investigated in vitro. The addition of ATP to the cells lead to a rapid, reversible reduction of cell area, which appeared to be a contraction. The change of cell area was measured using image analysis. ATP (15 mM) elicited the maximal contraction, with a 50% reduction in area achieved within 90 s. Adenosine was a partial agonist for the contraction. The contraction was dependent on control of the environmental calcium; cells in a calcium- and magnesium-free environment underwent spontaneous contraction. Replenishing the calcium and magnesium lead to stability of the cells. Since fibroblast contraction is involved in wound healing at many sites in the body, this system provides a physiological model for the direct investigation of fibroblasts with intact cell membranes, and allows for the testing of drugs which may influence wound healing in vivo.

Adenosine↗
PubMed1988

The effect of retinoids on the migration of Tenon's capsule fibroblasts.

The effect of the retinoids, retinol and all-trans acid, was assessed in vitro on the migration of rabbit Tenon's capsule fibroblasts, with a view to using these drugs as inhibitors of fibrosis in relation to trabeculectomies. No inhibition of fibroblast migration was demonstrated, and in fact retinol significantly enhanced both the random and directed migration of these cells (p less than 0.001 and p less than 0.01, respectively). This study emphasises the importance of using appropriate cells when investigating the effects of drugs on wound healing.

Animals↗
PubMed1988

Inflammation and the formation of epiretinal membranes.

In this review of the literature evidence is provided from clinical, histological and experimental sources that inflammatory processes play a central role in the pathogenesis of contractile epiretinal membranes and proliferative vitreoretinopathy.

Animals↗
PubMed1988

Tissue culture of retinal glial cells.

In order to be able to investigate the properties and characteristics of glia in the retina, a monotypic culture of retinal glial cells is likely to be an important research vehicle. Several techniques are now available to produce cultures of glial cells from the retina. These methods generally result in cultures of Mueller cells rather than retinal astrocytes. Publications on glial cultures involved complex procedures for the isolation of the target cell. Recent developments have resulted in simpler procedures with the advantage that large numbers of cultures can be established quickly and easily. Glial cultures have already been used in a variety of studies, simpler methods of culture, particularly if these can be adapted for culture of human glial cells, will probably result in more extensive use of cultures to unravel the properties of retinal glia.

Animals↗
PubMed1988

Recent experimental studies on the blood-aqueous barrier: the anatomical basis of the response to injury.

In the mammalian eye the tissue layers which effectively separate the neural retina and the transparent refractive media from the circulating blood are generally known as the blood-retinal barrier (BRB) and blood aqueous barrier (BAB) respectively. These have been delineated by morphologically identifying the ultrastructural features which impede the passage of molecules from the blood to the working parts of the eye; physiologically, there is a certain amount of overlap in their function, as there is free diffusion of solutes between the aqueous humour, the vitreous humour and the interstitial tissue of the neural retina. Notwithstanding, it is convenient and appropriate to maintain the distinction as the more recent work has focused on the fine structural aspects of these barrier systems. The abundant literature which describes the work leading to the identification and characterisation of these barriers has been reviewed in depth with great authority by several eminent researchers, notably the late Giuseppina Raviola, and Jose Cunha-Vaz. Certain pathological conditions, trauma--including surgical manipulation, and chemical irritation of the eye can cause significant disruption of these barriers with important clinical consequences. In our laboratory interest has centred around vascular and epithelial changes which occur when the eye is injured and which can lead to a breakdown of the BAB. More recently attention has been drawn to functional and behavioural differences between species, particularly with regard to the relative stability of the barrier.

Animals↗
PubMed1988

The retinal pigment epithelium and other tissues immunocytochemical studies using hybridoma supernatants.

We describe the production of hybridomas producing antibody reactive with retinal pigment epithelium. The patterns of reactivity obtained when supernatants from these hybrids were used to immuno-stain ocular and non-ocular tissues are described. From the patterns of reactivity obtained we suggest that the RPE shares common features with simple and glandular epithelia as well as myoepithelial cells. These findings may lend support to the hypotheses of RPE cell migration and contraction in the formation of epiretinal membranes and retinal detachment.

Animals↗
PubMed1988

Shape changes produced in detergent extracted bovine retinal pigment epithelium when exposed to ATP. A comparison with fibroblasts and smooth muscle cells.

The response of single detergent treated bovine retinal pigment epithelial cells in culture to ATP was measured with an image analyser. The most pronounced contraction was produced by 1.0 mM ATP with most change taking place in the first 10 min. At 1 h the area had decreased by about 33%, perimeter 22% and maximum length 25%. By way of comparison rabbit skin fibroblasts had a decreased area of approximately 40%, perimeter 25% and maximum length 22%. Bovine aortic smooth muscle cells on the other hand decreased in area by 55%, perimeter 40% and maximum length 36%. It is hoped that this assay may be used to evaluate drugs which could counteract contractile events in proliferative vitreoretinopathy.

Adenosine Triphosphate↗
PubMed1988

Growth and contractility of cells from fibrocellular epiretinal membranes in primary tissue culture.

Cells grew out in tissue culture from 37 of 53 fibrocellular epiretinal membrane explants, those from membranes of less than four months' clinical duration growing more consistently, more rapidly, and more exuberantly than those from membranes of more than four months' clinical duration. Electron microscopy demonstrated prominent microfilaments in the cytoplasm of some of the cells, and immunostaining for actin showed great variations in the pattern and intensity of staining. An ATP contraction assay conducted on 44 detergent-extracted cells and 47 intact cells revealed in each case a 30% average reduction in cell area. Immunostaining for cytokeratins following the ATP assay showed no significant difference in cell contraction between epithelial cells and non-epithelial cells. Clinical duration of the membrane had no significant influence on the contractility of cells growing from the explant.

Actin Cytoskeleton↗
PubMed1988

Intravitreal injection of fibroblasts: the pathological effects on the ocular tissues of the rabbit following an intravitreal injection of autologous skin fibroblasts.

The intravitreal injection of autologous cultured fibroblasts has been used by many groups to study proliferative vitreoretinopathy. Ninety-five New Zealand white rabbits were used to study the pathological effects on the ocular tissues following such an injection over various time periods up to six months. The ocular tissues were studied by light microscopy, electron microscopy, immunohistochemistry, and autoradiography. The cells which contributed to the inflammatory response (initially neutrophils, then later macrophages and lymphocytes) were found to gain entry into the vitreous via the pars plana, pars plicata, and the vessels associated with the optic nerve head. In the experimental eyes the detached retinae had a reduced ability to incorporate 3H proline. Both epiretinal and subretinal membranes were found on the retinal surfaces. The majority of the glial cells within the membranes were identified as Müller cells. The retinal pigment epithelium beneath the detached retinae incorporated 3H thymidine and detached into the subretinal space. Clear evidence was obtained of both epithelial cell migration through the retina and involvement within epiretinal membranes.

Animals↗
PubMed1988

The cytoskeletal elements of human retinal pigment epithelium: in vitro and in vivo.

The cytoskeletal elements of normal (in situ) and cultured human retinal pigment epithelium (RPE) were studied by a variety of immunocytochemical techniques. Primary antibodies to vimentin and cytokeratins were used. Positive immunoreactivity for vimentin was obtained with in situ and cultured material. The pattern of reactivity obtained with antisera and monoclonals to cytokeratins was more complex. Cytokeratin immunoreactivity could be demonstrated in situ and in cultured cells. The pattern of cytokeratin expression was similar to that of simple or glandular epithelia. A monoclonal antibody that specifically recognizes cytokeratin 18 identified a population of cultured RPE cells that had particularly well-defined filamentous networks within their cytoplasm. Freshly isolated RPE was cytokeratin 18 negative by immunofluorescence, but upon culture cytokeratin 18 positive cells were identifiable. Cytokeratin 18 positive cells were identified in all RPE cultures (other than early primaries), regardless of passage number, age or sex of the donor. In post-confluent cultures cytokeratin 18 cells were identified growing over cytokeratin 18 negative cells, suggesting an association of cytokeratin 18 immunoreactivity with cell proliferation. Immunofluorescence studies of retinal scar tissue from two individuals revealed the presence of numerous cytokeratin 18 positive cells. These findings indicate that RPE cells can be identified by their cytokeratin immunoreactivity and that the overt expression of cytokeratin 18 may be associated with proliferation of human RPE both in vitro and in vivo.

Aged↗
PubMed1988

The role of inflammation in the development of epiretinal membranes.

Single or multiple (3) injections of "Shigella" endotoxin were administered into the rabbit vitreous body to investigate the development of epiretinal membranes following intraocular inflammation. The evaluation included clinical assessment of the resulting traction retinal detachments, together with histological, autoradiographic, immunohistochemical and ultrastructural studies. Traction retinal detachments were found beneath fibroglial epiretinal membranes (being more extensive in eyes which had received 3 endotoxin injections) in the vicinity of the medullary rays, while purely glial membranes occurred over attached peripheral retina. The primary change at the vitreoretinal interface was an elevation of the inner limiting lamina of the retina followed by the extension of glial cells onto the retinal surface. It is postulated that glial cells breach the inner limiting lamina as a sequel to inflammation involving the vitreoretinal interface and form a scaffold upon which fibroblast-like cells migrate.

Animals↗