Biomedical subjects

Ian Grierson

Publications and source records attributed to Ian Grierson.

26 records · Page 2Linked to original sources

PubMed2002

An N-terminal truncated form of Orp150 is a cytoplasmic ligand for the anti-proliferative mushroom Agaricus bisporus lectin and is required for nuclear localization sequence-dependent nuclear protein import.

Nuclear localization sequence-dependent nuclear protein import is essential for maintaining cell function and can be selectively blocked in epithelial cells by mushroom (Agaricus bisporus) lectin. Here we report that a major intracellular ligand for this lectin is an N-terminally truncated form of oxygen-regulated protein 150 (Orp150), which lacks the endoplasmic reticulum translocation signal peptide of full-length Orp150. This cytoplasmic form of Orp150 expresses the lectin carbohydrate ligand (sialyl-2,3-galactosyl-beta1,3-N-acetylgalactosamine-alpha) and is shown to be essential for nuclear localization sequence-dependent nuclear protein import.

Active Transport, Cell Nucleus↗

PubMed2002

Histology and fine structure of the iris and outflow system following latanoprost therapy.

Latanoprost therapy can lead to iris darkening in susceptible individuals, particularly those with hazel eyes. Concerns have been raised about whether latanoprost, and for that matter other prostanoids, may have a harmful effect on the iris. In addition, it is unknown whether latanoprost causes increased pigmentation of the outflow pathways that might eventually lead to blockage and a type of pigmentary glaucoma. The present study summarizes findings from the authors' own laboratories on the effects of latanoprost as seen by light and electron microscopy of the iris and outflow tissues and reviews the as yet limited, relevant literature. The findings support the proposal that latanoprost-induced eye color change is likely to be due to an increased amount of melanin within iris stromal melanocytes rather than any increase in melanocyte numbers, although many aspects of the darkening process remain obscure. No marked pathological changes were found in the latanoprost-treated iris; however, the numbers of specimens examined by us to date are still small (40 specimens in all) and those with latanoprost-induced darkening are even fewer (18). In the authors' experience, pigmentation of the outflow system in latanoprost-treated eyes was no greater than in eyes with primary open-angle glaucoma without prostanoid treatment, but there have been only limited numbers of trabeculectomy specimens examined. Concerns about latanoprost producing meshwork hyperpigmentation and pigmentary glaucoma are discussed.

Antihypertensive Agents↗

PubMed2002

The role of matricellular proteins thrombospondin-1 and osteonectin during RPE cell migration in proliferative vitreoretinopathy.

PURPOSE: To investigate the hypothesis that the Matricellular proteins thrombospondin 1 (TSP1), tenascin (TN) and Secreted Protein Acidic and Rich in Cysteine (SPARC) modulate the migration of RPE cells in the epiretinal membranes of proliferative vitreoretinopathy. METHODS: Ten PVR epiretinal membranes were studied by immunohistochemical methods in which aggregates of RPE cells were identified by their expression of a broad range of cytokeratins. RPE subsets containing migratory RPE cells were detected by immunoreactivity for the monoclonal antibody RGE53 (which detects an epitope on cytokeratin-18 on motile RPE cells). Co-localisation of the RPE subsets with the glycoproteins TSP-1, SPARC and TN was evaluated. RESULTS: Nineteen migratory RPE (RGE53 positive) subsets and 13 RPE (RGE53 negative) subsets were identified. All of the RGE53+ subsets colocalised with TSP1 and SPARC and 17 with TN. Ten of the RGE53- aggregates stained for TN, 6 for SPARC and 5 for TSP1. The association between the presence of RGE53+ cells in the RPE cell aggregates and TSP1 immunoreactivity in the aggregates was significant (p < 0.001), and there was a comparable significant association between RGE53+ cells and SPARC (p < 0.001). No such association was detected for RGE53+ cells and TN (p > 0.2). CONCLUSIONS: The findings support the concept that the migration of retinal pigment cells in epiretinal membranes is modulated by TSP1 and SPARC and thus that these two proteins ultimately may represent therapeutic targets in the management of the membranes.

Cell Differentiation↗

PubMed2002

Ischaemic preconditioning of skeletal muscle. 1. Protection against the structural changes induced by ischaemia/reperfusion injury.

Ischaemic preconditioning is a process by which exposure of a tissue to a short period of non-damaging ischaemic stress leads to resistance to the deleterious effects of a subsequent prolonged ischaemic stress. It has been extensively described in the heart, but few studies have examined the possibility that it can occur in skeletal muscle. We have used a rat model of ischaemia of one limb to examine this possibility. Exposure of the hind limb to a period of ischaemia of five minutes and reperfusion for five minutes significantly protected the tibialis anterior muscle against the structural damage induced by a subsequent period of limb ischaemia for four hours and reperfusion for one hour. This protection was evident on examination of the muscle by both light and electron microscopy. Longer or shorter times of prior ischaemia had no effect.

Animals↗

PubMed2002

Ischaemic preconditioning of skeletal muscle 2. Investigation of the potential mechanisms involved.

We have previously shown that prior exposure of rat hind limbs to ischaemia for five minutes and reperfusion for five minutes reduced the structural damage to skeletal muscle which followed a subsequent period of ischaemia for four hours and reperfusion for one hour. We have now examined the potential mechanisms by which this ischaemic preconditioning protocol may be effective in reducing damage to skeletal muscle induced by prolonged ischaemia and reperfusion. Prior exposure of the hindlimb to ischaemia for five minutes and reperfusion for five minutes did not prevent the fall in the ATP content of tibialis anterior which occurred after a subsequent period of ischaemia for four hours and reperfusion for one hour. Similarly, no effect of the preconditioning protocol was seen on the elevated muscle myeloperoxidase, indicative of an elevated neutrophil content, or abnormal muscle cation content. Reperfused ischaemic muscle was also found to have an increased content of heat-shock protein (HSP) 72, but the preconditioning protocol did not further increase the content of this or other HSPs indicating that it was not acting by increasing the expression of these cytoprotective proteins. The protective effects of preconditioning appeared to be mimicked by the infusion of adenosine to animals immediately before exposure to the four-hour period, indicating a potential mechanism by which skeletal muscle may be preconditioned to maintain structural viability.

Adenosine Triphosphate↗

PubMed2002

Direct comparison of the migration of three cell types involved in epiretinal membrane formation.

PURPOSE: The purpose of the present study was to develop an accurate and sensitive migration assay to compare the migratory capabilities of retinal pigment epithelial (RPE) cells, retinal glial (RG) cells, and fibroblasts (the cell types crucial in epiretinal membrane [ERM] formation) under identical microenvironmental conditions and thus to identify potential target areas in ERM management. METHODS: Cultured bovine RPE and RG cells and scleral fibroblasts (SFs) in both single and mixed cell type populations were induced to migrate in modified 48-well Boyden chambers. The labels used to distinguish between the cell types were latex microspheres and carmine particles. The chemoattractants used were fibronectin and PDGF, both of which are associated with epiretinal membrane development. RESULTS: When migrating independently, all three cell types showed a positive response to fibronectin at an optimal concentration of 10 microg/mL. The RG cells migrated in a significantly greater number than the RPE cells (P < 0.05), but the differences in number of migrating cells between RG cells and SFs and RPE cells and SFs were not significant. When the cells were labeled and migrating together, it became clear that the RG cells consistently migrated in a higher number than the SFs (P <or= 0.001) and both the SFs and RG cells showed a greater migratory response than the RPE cells (P <or= 0.01). CONCLUSIONS: The mixed cell migration (MCM) test system is a simple and useful assay to distinguish between the migratory responses of different cell types in the same microenvironment. It has highlighted the pronounced migratory response of RG cells to standard chemoattractants and has cast some level of doubt that, in comparative migratory terms, RPE cells are particularly good responders.

Animals↗

PubMedDate not supplied

Latanoprost and pigmentation.

Latanoprost is a prostaglandin analogue with well-established efficacy in the treatment of open-angle glaucoma and ocular hypertension. Once-daily administration of this drug for up to 5 years is generally well tolerated both locally and systemically. While most reported side effects have been classified as mild in intensity, an increase in iris, eyelash, and periocular pigmentation has been associated with prostaglandin analogue use in some patients. Follow-up studies of patients withdrawn from latanoprost treatment suggest that the increased iridial pigmentation is irreversible while changes in eyelash and periocular skin pigmentation are reversible after cessation of therapy. Concern as to whether latanoprost affects proliferation of iridial melanocytes or other cellular components prompted investigation into its mechanism of action. All available evidence from in vitro, in vivo, and clinical studies suggests that latanoprost does not induce melanocyte proliferation. Morphologic study of human peripheral iridectomy specimens did not reveal any significant latanoprost-induced pathologic change in the iris. There was no evidence of melanin granules blocking the outflow pathways in treated patients. Stimulation of melanogenesis in iridial melanocytes, perhaps through an effect on tyrosinase, appears to account for induction of melanin production. Additional studies are in progress to further elucidate the mechanism of latanoprost-induced increased iridial pigmentation.

Antihypertensive Agents↗

PubMedDate not supplied

Edible mushroom (Agaricus bisporus) lectin inhibits human retinal pigment epithelial cell proliferation in vitro.

The retinal pigment epithelium (RPE) plays a major role in the development of the anomalous retinal scarring response termed proliferative vitreoretinopathy. The present study was undertaken to investigate whether agaricus bisporus lectin inhibited human RPE proliferation in vitro. Fluorescein isothiocyanate-labeled agaricus bisporus lectin was used to study binding of lectin to cultured human RPE. The effect of a 24-hour exposure of agaricus bisporus lectin on RPE proliferation was measured using (methyl-3H)-thymidine incorporation into DNA. Toxicity studies were assessed using morphologic evaluation, trypan blue exclusion, and a cell viability assay. Agaricus bisporus lectin bound to RPE cells and was inhibited by preincubation of lectin with asialomucin. Agaricus bisporus lectin caused a dose-dependent inhibition of RPE proliferation (one-way ANOVA, F = 94.470, p < 0.001) that was partially reversible on removal of the lectin. Compared with controls, cells remained viable and no morphological changes or trypan blue staining was noted in RPE exposed to agaricus bisporus lectin. Human RPE binds agaricus bisporus lectin and inhibits proliferation without apparent cytotoxicity. It therefore merits consideration as a potential antiproliferative agent in the prevention and treatment of proliferative vitreoretinopathy and other nonocular anomalous wound healing processes.

Cell Division↗