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Biomedical subjects

I Grierson

Publications and source records attributed to I Grierson.

At least 127 records · Page 7Linked to original sources
PubMed1985

Experimental scar membranes in the rabbit's vitreous. An autoradiographic and quantitative morphological study.

A morphological and autoradiographic assessment was made of scar tissue development in an experimental rabbit model of proliferative vitreoretinopathy which involves the intravitreal injection of cultured autologous skin fibroblasts. Within a few hours after injection as many as 40% of the cultured cells had autolysed. However, the remaining cells proliferated and formed membranes. The incorporation of [3H] thymidine was maximal at 1 week. Between 2 and 4 weeks spindle-shaped myofibroblasts were prominent, and this form of fibroblast has been considered to have an important role in scar tissue contraction. At the end of 4 weeks it was noted that all eyes had developed retinal detachments. Subsequently the membranes became progressively more fibrous and lipid-like material accumulated in the cytoplasm of many cells. The findings were discussed in relation to the use of this model to test the effectiveness of various drugs which may be of value in the treatment of proliferative vitreoretinopathy.

Animals↗
PubMed1985

Natural history of fibrocellular epiretinal membranes: a quantitative, autoradiographic, and immunohistochemical study.

Quantitative, autoradiographic, or immunohistochemical light microscopy was conducted on 85 surgically excised epiretinal membranes to investigate the activities of component cells and the natural history of the extraretinal scars. Membranes of less than four months' clinical duration ('early' membranes) contained significantly more cells than 'late' membranes, while collagen was more abundant in the older specimens. No correlation was established between membrane opacification and either the cellularity or the collagen content of the membranes. Epiretinal membranes had some features in common with healing skin wounds, but the activities of cells in the epiretinal membranes were relatively protracted and disordered. Fibronectin was found to be a significant component of epiretinal membranes and therefore represents a target at which pharmacological intervention could be aimed.

Actins↗
PubMed1985

Reparative epiretinal fibrosis after diabetic vitrectomy.

Closed microsurgery for the haemorrhagic and tractional sequelae of proliferative diabetic retinopathy is frequently successful in restoring and maintaining useful vision. Severe complications may arise, however, including the reproliferation of cellular membranes on the retinal surface with subsequent retinal distortion or redetachment. The clinical and histopathological features of such reparative epiretinal fibrosis are presented and methods of prevention are discussed.

Diabetic Retinopathy↗
PubMed1985

An animal model of filtration surgery.

An animal model for glaucoma fistulising surgery is described. The model is designed to fail after a few weeks. It is suggested that the model may be used to investigate the effects of topical or systemic agents on the results of glaucoma surgery. The preliminary results of intraocular pressure and facility of outflow in the control group of rabbits are presented.

Animals↗
PubMed1984

Age-related changes in the canal of Schlemm.

A quantitative study of semi-thin sections through Schlemm's canal from 44 human eyes was undertaken. It was shown from counts of endothelial nuclei that the cell population decreased with age. The decrease in cell population was estimated from linear regression equations to be in the order of 430 cells per year for the whole canal and 320 cells per year for the canal's inner wall. Evidence was provided which indicated that counts of the giant vacuoles also decreased with age.

Adult↗
PubMed1984

Retinal and epiretinal glia--an immunohistochemical study.

Immunohistochemical techniques were used to examine the distribution of cells containing glial fibrillary acidic protein (GFAP) in normal and pathological human specimens, including 22 globes (13 of which contained epiretinal membranes 'in situ'), 16 surgically excised epiretinal membranes, and monolayers of cells obtained from five epiretinal membranes placed in tissue culture. The astrocytic cells of normal and pathological retinae stained with the glial-cell marker, but Müller cells were GFAP-negative in normal retinae at the antisera dilutions used. Müller cells did, however, stain in retinae from glaucomatous eyes and in eyes with prolonged retinal detachment. Electron microscopy did not reveal any obvious morphological difference between the intermediate filaments of normal (GFAP-negative) and GFAP-positive Müller cells. Ten of the 13 epiretinal membranes 'in situ', all 16 excised membranes, and three of the five monolayers contained glial cells. Purely glial membranes were not associated with retinal puckering or detachment, while all membranes causing tractional complications had a prominent fibrous, non-glial component. Our findings suggest that glial cells do not contribute significantly to the contractile forces generated by epiretinal membranes. They may, however, provide a scaffold on which other cells proliferate and contract and an anchorage by means of which tangential forces are transmitted into and through the retina.

Adolescent↗
PubMed1984

Retinal pigment epithelial cells in epiretinal membranes: an immunohistochemical study.

Immunohistochemical techniques were used to identify cells containing cytokeratins in sections or tissue-culture monolayers from ocular (reference) tissues and also from 22 epiretinal membranes obtained during closed microsurgery for macular pucker or massive preretinal retraction. Results of cytokeratin immunostaining in reference tissues indicated that this is a valuable means of determining the contribution and distribution of epithelial cells in epiretinal membranes, and that the epithelial cells in the membranes were probably derived from the retinal pigment epithelium. Epithelial cells were identified in 17 of the 22 epiretinal membranes, but they did not usually constitute the predominant cell type. We concluded that the fibroblasts or fibroblast-like cells thought to be responsible for the contraction of epiretinal membranes are seldom of retinal pigment epithelial origin. Biomicroscopic pigmentation of a membrane was shown to be a poor guide to its epithelial cell population.

Animals↗
PubMed1984

Elastic and related fibres in the normal cornea and limbus of the domestic cat.

The presence of elastic and related fibres in the corneal and limbal tissue of the domestic cat is described. Various ages of animal from birth to maturity were studied by light and electron microscopy. Oxytalan fibres were present throughout the new-born kitten cornea. They were seen in greatest concentration both at the junction of the posterior limiting lamina with the inner substantia propria and beneath the peripheral anterior epithelium. With increasing maturity, oxytalan fibres disappeared from all but the most peripheral parts of the cornea where some of the, by now, thicker oxytalan fibres had matured into elaunin. All ages of animals studied showed an abrupt increase in fibre thickness and numbers at the corneal limbus. Oxytalan fibres predominated in the newborn kitten limbus but material from adult animals showed an increased proportion of elaunin fibres. Occasional elastic fibres were also seen in the more superficial region of the adult limbus. An overall decrease in elastic fibre types with increasing maturity was most obvious in the middle limbal layers.

Aging↗
PubMed1983

Human trabecular meshwork in primary culture: a morphological and autoradiographic study.

The growth and behaviour of human trabecular meshwork cells in primary culture was studied by light microscopy, time-lapse cinephotomicrography, autoradiography and electron microscopy. In all 925 explants of trabecular tissue from 132 eyes (68 +/- 14 years) were set up, and 20% produced extensive monolayers. Failure to produce primary outgrowths did not increase substantially until the eyes were over 5 days post-mortem. The latent period prior to growth was anything from a few days to 4 weeks; only then did meshwork cells label with [3H]-thymidine. The cells which grew incorporated large amounts of [3H]-leucine and this served as a useful marker to identify migratory cells. In addition they had the ultrastructural features of metabolically active cells including many mitochondria, a well-developed Golgi apparatus, abundant rough endoplasmic reticulum and prominent lysosomes. It was considered that the cells in primary culture had many features in common with 'activated' rather than normal meshwork cells.

Adult↗
PubMed1983

Mathematical modelling of aqueous humour outflow from the eye through the pores in the lining endothelium of Schlemm's canal.

Aqueous humour leaves the eye mainly by way of pore openings in vacuolar swellings in the endothelial cells which line the wall of Schlemm's canal. Calculation of the resistance to fluid flow offered by these small pores requires data on their incidence and dimensions linked to a suitable mathematical model. Data are derived from scanning electron microscopy (SEM) studies conducted on rhesus monkey eyes maintained at an intraocular pressure (IOP) of either 8 or 15 mmHg and on human eyes either untreated controls or treated with pilocarpine. Mathematical models of flow through the pore openings are developed. Application of a Venturi tube model to the SEM data shows that the pore resistance of rhesus monkey eyes at 8 mmHg was seventeen times greater than that at 15 mmHg while the pore resistance in untreated human eyes was five times greater than in eyes which received pilocarpine.

Animals↗
PubMed1983

Epiretinal membranes in vitro.

Monolayers of cells were grown from epiretinal membranes using standard tissue culture techniques. The growing cells were filmed by time-lapse cinephotomicrography to record their locomotory characteristics and cell-to-cell interactions. The established layers of cells were examined in the scanning electron microscope. In addition, the cultured cells were studied immunohistochemically to identify specific cell types and the distribution of contractile elements (e.g. actin). The locomotory patterns, the topography and the immunohistochemistry of cells from epiretinal membranes were compared to the movement, appearance and staining characteristics of a wide range of normal cells in culture. From the growth characteristics in tissue culture, early membranes appeared more hypercellular than longer standing membranes. Cell outgrowth was established more quickly and was more widespread in the young epiretinal membranes than in older, more fibrous, specimens. The locomotory and immunohistochemical studies demonstrated that a wide variety of cell types may contribute to epiretinal membranes. A remarkably wide range of cell forms were observed in cultures of individual membranes. Epithelial and glial cells were found in many of the monolayers. However, they did not constitute the majority of cells in the cultures. The predominating cell types had the morphological and locomotory characteristics of fibroblasts or macrophages.

Animals↗
PubMed1983

Life on implants.

Seven Ridley Mark I anterior chamber lenses were removed from patients at St Thomas's Hospital. The lenses had been in place for an average of 15 years. The indication for removal was corneal endothelial decompensation with painful bullous keratopathy. Examination of the lenses under the scanning electron microscope showed remarkably similar morphology in each case. A well organised fibrin membrane covered the implants to which iris pigment epithelial cells were adherent. Red blood cells, scattered fibroblasts and pigment granules were also found. Giant cells were not identified while macrophages and lymphocytes were rare. These findings suggest that corneal endothelial decompensation was not due to chronic inflammation but was probably caused by movement of the implants within the eyes.

Adult↗
PubMed1983

Giant vacuoles in the lining endothelium of the human Schlemm's canal after topical timolol maleate.

The outflow system was studied by light microscopy in nine human eyes that were treated with topical timolol maleate (0.5%) prior to enucleation for malignant melanoma of the choroid. The frequency of "giant vacuoles" in the lining endothelium of Schlemm's canal and the diameter of these structures was the same in a control group of eyes as in the timolol-treated series. There was no qualitative difference between the architecture of the meshwork in the control and treated groups. These morphologic findings suggested that timolol had no direct action on the outflow apparatus and did not reflect the intraocular pressure (IOP) lowering effect of the drug. The effects of anesthesia, surgical manipulations, and fixation by immersion may have masked any subtle drug effects.

Aqueous Humor↗
PubMed1981

The post-mortem vacuoles of Schlemm's canal.

A two-part study was conducted in which post-mortem changes were investigated in the baboon outflow system. It was found that the meshwork cells closest to the chamber angle were particularly susceptible to post-mortem advance. Post-mortem vacuoles developed in the endothelium of Schlemm's canal and by light microscopy these structures could be mistaken for giant vacuoles. On the other hand it was shown by electron microscopy that the giant vacuoles which have been implicated in the transendothelial transfer of aqueous humour and post-mortem vacuoles were distinct and separate entities.

Animals↗
PubMed1981

Histopathologic and clinical associations of scleritis and glaucoma.

Of 92 enucleated eyes with scleral inflammation and 114 eyes from 81 patients with scleritis, 45 (49%) and 20 (18%), respectively, showed evidence of increased intraocular pressure. Damage to the trabecular meshwork of iridocyclitis, overlying corneoscleral inflammation, or peripheral anterior synechiae was the most common cause of increased intraocular pressure. Other causes included topical corticosteroid use, angle neovascularization, and posterior scleritis with secondary angle closure.

Adolescent↗