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Biomedical subjects

I Grierson

Publications and source records attributed to I Grierson.

At least 109 records · Page 6Linked to original sources
PubMed1987

Age-related depletion of the cell population in the human trabecular meshwork.

The number of cells in the human trabecular meshwork was assessed for counting meshwork cell nuclei in semithin Araldite sections cut in the meridonal plane. The counts of nuclei decreased with increasing age and the decrease was associated with all regions of the meshwork. The appropriate regression equation and a mean length for meshwork nuclei was used to estimate cell numbers. At 20 years of age the estimated cell number for the whole meshwork was 763,000 which decreased to 403,000 cells by 80 years with a loss rate of 6,000 cells per year.

Adolescent↗
PubMed1987

Age-related cellular proliferation at the vitreoretinal juncture.

Clinical and pathological features of non-vascularised epiretinal membranes are reviewed with special attention to focal epimacular tractional lesions in the elderly. The role of immunohistochemistry in elucidating the nature of component cells of complex epiretinal membranes is emphasised. Clinicopathological correlation establishes the 'fibroglial membrane' as the causative lesion of age-related epimacular traction. The pathogenesis of this process is discussed, including relevant animal models, and chronic inflammation and ischaemia (rather than acute posterior vitreous detachment) are implicated. Vitrectomy and epimacular membrane peeling results in significant visual improvement in most patients.

Adult↗
PubMed1987

Normal rabbit aqueous humour, fibronectin, and fibroblast conditioned medium are chemoattractant to Tenon's capsule fibroblasts.

Some of the chemotactic and chemokinetic properties of rabbit Tenon's fibroblasts were examined in a 48-well micro-chemotaxis chamber. Normal rabbit aqueous humour, fibronectin, and fibroblast conditioned medium were used in the assay, and all were shown to be chemoattractant. In addition, aqueous humour was shown to be powerfully chemotactic. Since the failure of human trabeculectomies is associated with migration of fibroblasts to the operation site, the study of the chemoattractant influences acting on these cells may allow manipulation of their behaviour in order to influence favourably the outcome of surgery.

Animals↗
PubMed1987

Enzymatic activities in the iris-ciliary body of the rabbit eye during experimentally induced acute ocular inflammation.

Intravitreal injection of 5 micrograms of Shigella endotoxin, in the rabbit eye, induced an acute inflammatory response which was characterised by conjunctival hyperaemia, limbal and ciliary vascular injection, iritis, aqueous flare, miosis and reduction in intraocular pressure. Iris-ciliary body tissues, from normal and inflamed eyes, were fractionated into subcellular enriched fractions and the activities and distribution of selected enzymes were estimated. Alkaline phosphatase, a plasma membrane-bound enzyme, showed an increase in activity, whereas succinate dehydrogenase and Mn-Superoxide dismutase, both mitochondrial-bound enzymes, exhibited decreased activities. Lysosomal acid phosphatase displayed an increase in free activity and retention of latent activity inside the organelle. No alteration in free activity was shown by acid cathepsin. The cholinesterases did not exhibit any changes in activities nor did the cytosolic enzymes Cu/Zn-superoxide dismutase and lactate dehydrogenase. The decrease activity of the respiratory mitochondrial enzyme succinate dehydrogenase may contribute to the reduction in intraocular pressure, and the ability of the lysosomal organelles to retain their hydrolytic enzymes, ensures recovery of the cell from acute inflammatory attack.

Animals↗
PubMed1987

The viscous layer overlying the corneal posterior epithelium of the domestic cat.

The presence, nature, and composition of a layer of transparent mucinous material overlying the posterior epithelium (called here, 'the viscous layer of the posterior epithelium') was investigated in material from domestic cats. A number of different techniques were used. (a) A variety of different fixatives and histochemical stains was used to preserve and visualise the layer of examination by light microscopy. Frozen sections of fresh material were also examined after on-slide fixation. The preservation and appearance of the viscous layer was critically dependent on the type of fixative used and on minimal agitation during tissue processing. It appeared to contain sulphated acid GAGs, the staining of which was histochemically masked around pH 2.5. The use of frozen sections produced the most reliable preservation of the layer. (b) Ruthenium red or cetylpyridinium chloride was used to preserve the viscous layer for examination by transmission electron microscopy. It appeared in a dispersed form after stabilisation by ruthenium red and in a condensed form after stabilisation by cetylpyridinium chloride. (c) Freeze-dried tissue was examined by scanning electron microscopy. The viscous layer usually appeared as a band of coral- or moss-like material which was often many times the thickness of the posterior epithelium. Usually, the areas of the layer adjoining the posterior epithelium and the anterior chamber appeared more condensed when compared to the material between these two regions. The physiological significance of the viscous layer is discussed.

Animals↗
PubMed1986

Regional differences in phagocytosis by the corneal endothelium in the domestic cat.

The phagocytosis of IgG-coated latex microspheres by the central and peripheral regions of the corneal endothelium in the domestic cat was investigated by organ culture. The endothelium was exposed to 1.357 X 10(7) microspheres/mm2, and counts of ingested microspheres were made by scanning electron microscopy. Initial assessments of phagocytosis over 8-h and 24-h periods of culture gave extremely low levels of incorporation. Therefore, subsequently, a 48-h period of culture was adopted. Microsphere uptake levels per square millimeter over 48 h were as follows: peripheral endothelium 6,021 +/- 3,162; central endothelium 2,000 +/- 1,529; overall 4,011 +/- 3,294. The greater uptake of microspheres in the peripheral cornea was statistically significant (P less than 0.002, paired t-test). The involvement of microvilli in phagocytosis by corneal endothelial cells was proposed.

Animals↗
PubMed1986

Phagocytosis of latex microspheres by bovine meshwork cells in culture.

The ability of cultured bovine trabecular meshwork cells to phagocytose latex microspheres was studied by electron microscopy. In addition, the incorporation of 125I gamma-globulin-coated microspheres by the meshwork cells was monitored. The cultured cells, on the basis of quantitation by scanning electron microscopy, did not show significant preference between biotic particles (gamma-globulin-coated microspheres) and abiotic particles (uncoated microspheres). Surface microvilli appeared to be involved in the initial stages of phagocytosis; indeed a significant negative correlation was demonstrated between the incidence of microvilli and the commitment to phagocytosis of preconfluent cells. Two weeks postconfluent cells were shown to be significantly less phagocytic than preconfluent cells. The importance of these findings in terms of the behaviour of meshwork cells in vivo is discussed.

Animals↗
PubMed1986

The effects of various levels of intraocular pressure on the rabbit's outflow system.

The effects of various levels of intraocular pressure on the morphology of the rabbit outflow system were investigated. In a total of 20 rabbits, intraocular pressure was maintained at various levels between 0-50 mmHg in the experimental eye and at 20 mmHg in the control eye for 1 hr. Flow rates into the eyes were measured by following the movement of a miniscus through a calibrated capillary tube. Progressive increase in pressure lead to distension and enlargement of the ciliary cleft. The meshwork tissues stretched and distended, and the vessels of the angular aqueous plexus had pressure-sensitive giant vacuoles of their endothelium. These vessels were prone to closure at pressures of 30 mmHg and greater. Difficulties associated with quantitation of giant vacuoles in this species were discussed.

Animals↗
PubMed1986

Some effects of phagocytosis on bovine meshwork cells in culture.

In this tissue-culture study, some effects of phagocytosis on the cell were investigated. Third-passage bovine trabecular-meshwork cells were incubated with latex microspheres for periods of up to 60 hr. Cells which had been involved in phagocytosis were found to settle at a faster rate than control cells, but if microspheres were added to the medium of recently settled cells, there was a reduction in their proliferative activity. Incorporation of tritiated proline remained unchanged, whereas uptake of tritiated glucosamine increased with the time period of phagocytosis. The fibronectin scaffold was more extensive and elaborate when cells were pre-incubated with microspheres before settlement. Exposure to a low concentration of microspheres promoted a higher uptake of a second presentation of 125I-labelled microspheres--an effect which was not seen if the original dose was too high.

Animals↗
PubMed1986

Human retinal pigment epithelial cells in the vitreous of the owl monkey.

Cultured human retinal pigment epithelium was injected into the vitreous of owl monkeys. The epithelial cells were derived from either a foetal or an adult cell line. The five monkeys which were injected with cultured foetal cells developed substantial vitreal membranes and had retinal detachment by 2 weeks, whereas the five monkeys with cultured adult cells did not develop detachments within the period of investigation, and vitreal membranes were insubstantial. An electron-microscopic, immunohistochemical and autoradiographic study was conducted on these eyes to investigate in detail the behaviour and intraocular effects of the injected cells.

Adult↗
PubMed1986

Contraction of scar tissue in the rabbit vitreous.

Sheets of vitreous membrane (scar tissue) and associated retinal detachment were produced in the right eye of 86 adult New Zealand white rabbits by intravitreal injection of cultured autologous skin fibroblasts. The membranes were examined by light and electron microscopy and time-lapse cinephotomicrography. Immunohistochemistry was used to demonstrate alterations in the distribution of cytoplasmic contractile proteins. While retinal detachment and membrane contraction were taking place, there was pronounced increase in the numbers of fibroblasts with an elongated spindle shape. These spindle-shaped cells had some similarities to myofibroblasts including the presence of 'stress cables'. However, the myofibroblast-like cells stained much less avidly for cytoplasmic (actin) microfilaments than migratory fibroblasts seen at early stages of membrane development. The significance of migrating fibroblasts and myofibroblasts in scar contraction is discussed.

Animals↗
PubMed1986

Investigations of cytoskeletal elements in cultured bovine meshwork cells.

An ultrastructural, immunohistochemical, and functional study was conducted on cultured bovine meshwork cells. Particular emphasis was placed on the organization of the cytoskeleton, and the cells were viewed either as whole cells or following detergent extraction. For ultrastructural examination, several modes of viewing were adopted, including a detector situated above the specimens collecting secondary electrons (SE), a detector situated beneath the specimen collecting transmitted electrons (STEM), and conventional transmission electron microscopy at 100 KV (TEM). In whole cell mounts, information was obtained about the organization of the cytoskeleton and its relationship to other cytoplasmic organelles. Extraction procedures removed much of the plasma membrane and most organelles. The nucleus and cytoskeleton remained and stress fibers were prominent. Immunohistochemistry showed that the actin content of the cytoskeleton could be preserved after detergent extraction. Detergent-extracted cells decreased their surface area when exposed to MgATP in a dose-dependent manner. The decrease in surface area was associated with disassembly of cytoskeletal stress fibers and was optimal with 1 mM MgATP. Whether or not the change in surface area could be considered a "contractile event" was discussed.

Actins↗
PubMed1986

Aqueous drainage in the dog.

The anatomical features of the iridocorneal angle and its associated structures are described and their role in the drainage of aqueous in the dog discussed. Anterior segment material from 126 dogs of various ages and many breeds was examined by light and electron microscopy, the results confirming that the elements of bulk aqueous drainage in this species are essentially the same as those of the primate eye. In particular, the demonstration of an avascular aqueous plexus lined with a vacuolating endothelium as an analogue of the primate Schlemm's canal has indicated that the theory of capillary drainage of aqueous is no longer tenable for the dog.

Animals↗
PubMed1985

The morphological features of bovine meshwork cells in vitro and their synthetic activities.

The morphological characteristics of 3rd-passage cultured bovine meshwork cells were investigated, as were some of their synthetic activities. Growing meshwork cells had the ultrastructural characteristics of metabolically active cells whereas postconfluent cells formed gap junctions at their lateral borders and were closer in their fine structure to meshwork cells in vivo. The incorporation of 3H proline and 3H glucosamine was significantly greater in growing than postconfluent cultures. The normal bovine outflow system was rich in type I collagen but type V collagen and fibronectin was also evident. The 3rd-passage cells were shown to synthesize type I collagen, type V collagen and fibronectin. However, ultrastructural studies of the extracellular matrix which was produced in vitro demonstrated the presence of small fibrils with no distinctive banding pattern, unlike the larger collagen fibrils with a 640 A banding pattern seen in vivo.

Animals↗
PubMed1985

The effects of injections of cultured fibroblasts into the rabbit vitreous.

A comparison was made between rabbit's eyes which had an intravitreal injection of either 400,000 autologous or homologous skin fibroblasts. The follow-up period was up to 6 months with autologous and 10 weeks with homologous cells. The evaluation involved the clinical assessment of membrane formation, retinal detachment and anterior segment inflammation. In addition, a detailed histological, electron microscopic and autoradiographic study was made of membrane development and changes in the surrounding tissue. Clinical evaluations revealed little difference between the two models. However, on the basis of macroscopic and microscopic examination, homologous cells produced more extensive detachments and more pronounced retinal gliosis. Plasma cells were evident in the choroid 6 weeks after homologous fibroblast injection, but they were not associated to any appreciable extent with the autologous model. Fibrovascular proliferation from around the optic nerve head made a major contribution to the formation of membranes in the experiments with homologous fibroblasts but not those using the autologous cells.

Animals↗
PubMed1985

The cells of the bovine outflow system in tissue culture.

Meshwork cells from the bovine outflow system were grown in culture and their growth characteristics and behaviour in vitro reported. The cells were studied by inverted phase microscopy and time-lapse cinephotomicrography. It was found that plating efficiency was highest for third and seventh passage cells. These cells reached confluence within 2 weeks when plated out at 7.5 X 10(3) cells cm-2 in a conventional culture medium containing 10% serum. Third passage cells were studied in greatest detail. These cells exhibited postconfluence contact inhibition of division. By 2 weeks postconfluence the division rate decreased 10-fold to a level of less than six divisions per thousand cells per day. The contact inhibition was not overcome by increasing the serum content of the medium. On the other hand, a 30-fold increased division rate could be produced after scratching the culture flask. Postconfluent contact-inhibited cultures were considered to be a better reflection of the behaviour and activities of meshwork cells in vivo than cultures which retain a high level of division.

Animals↗