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Biomedical subjects

I Grierson

Publications and source records attributed to I Grierson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Active scatter factor (HGF/SF) in proliferative vitreoretinal disease.

PURPOSE: Hepatocyte growth factor/scatter factor (HGF/SF) possesses mitogenic, motogenic, and morphogenic properties and has recently been implicated in various retinal diseases. The role of HGF/SF in proliferative vitreoretinal disease was investigated. METHODS: Sections of epiretinal membranes were stained immunohistochemically for cytokeratins, to identify HRPE cells, and for HGF/SF receptor (c-Met). Cultured HRPE cells were stained for c-Met and investigated for shape change in response to HGF/SF, by using image analysis. The dose-response relationship for HRPE cells to HGF/SF was investigated by a cell migration assay and the specificity of this response evaluated by a neutralization experiment. Subretinal fluid (SRF) and vitreous from patients with retinal detachment and proliferative vitreoretinopathy (PVR) plus vitreous from eyes obtained after death, eyes with macular hole, and eyes with proliferative diabetic retinopathy (PDR) were investigated for the presence of HGF/SF using an enzyme-linked immunosorbent assay (ELISA). HGF/SF activity was measured using an MDCK cell scatter assay. RESULTS: HRPE cells in epiretinal membranes and in culture expressed c-Met. Cultured HRPE cells responded to HGF/SF by an epithelial-to-mesenchymal shape change and by cell migration, a response that increased with increasing concentrations of HGF/SF. This response was reduced in the presence of neutralizing antibody. There was evidence of HGF/SF in increasing concentrations in more severe PVR and in PDR when measured by ELISA, and, conversely, there was evidence of correspondingly decreasing HGF/SF activity when measured by MDCK cell scatter assay in these diseases. CONCLUSIONS: HGF/SF is present in normal and pathologic vitreous. HRPE cells respond by shape change and cell migration to HGF/SF. Concentrations of HGF/SF increase in proliferative vitreoretinal disease and increase in turn with increased severity of the disease, but HGF/SF bioactivity decreases (consistent with activator depletion). These findings are consistent with the hypothesis that HGF/SF may play a role in the HRPE mesenchymal transformation that typifies PVR.

Adult↗
PubMed1999

Edible mushroom (Agaricus bisporus) lectin, which reversibly inhibits epithelial cell proliferation, blocks nuclear localization sequence-dependent nuclear protein import.

The Galbeta1-3GalNAcalpha (TF antigen)-binding lectin (ABL) from the common edible mushroom (Agaricus bisporus) has a potent anti-proliferative effect without any apparent cytotoxicity. This unusual combination of properties prompted investigation of its mechanism of action. In contrast to soluble lectin, agarose-immobilized, and hence noninternalizable ABL had no effect on proliferation of HT29 colon cancer cells. Electron microscopy of HT29 cells incubated with fluorescein- and gold-conjugated ABL showed internalization of the lectin into endocytotic vesicles and multivesicular bodies. Confocal microscopy showed perinuclear accumulation of fluorescein isothiocyanate-conjugated lectin, which also inhibits HT29 cell proliferation, raising the possibility that the lectin might interfere with nuclear pore function. Transport of heat shock protein 70 into the nucleus in response to heat shock was blocked by preincubation of HT29 cells for 6 h with 40 micrograms/ml ABL. In digitonin-permeabilized cells, nuclear uptake of bovine albumin conjugated to a nuclear localization sequence (NLS)-containing peptide was also inhibited by a 15-min preincubation with 40-100 micrograms/ml ABL. In contrast, serum-stimulated nuclear translocation of mitogen-activated protein kinase, which is NLS-independent, was not affected by pretreatment of cells with the lectin. These results suggest that the anti-proliferative effect of ABL is likely to be a consequence of the lectin trafficking to the nuclear periphery, where it blocks NLS-dependent protein uptake into the nucleus.

Adult↗
PubMed1999

Localisation of connective tissue and inhibition of autofluorescence in the human optic nerve and nerve head using a modified picrosirius red technique and confocal microscopy.

The use of picrosirius red to localise connective tissue in thin tissue sections viewed by bright-field microscopy is well documented. Its use on thin tissue sections imaged by fluorescence confocal microscopy has also been reported. Here we describe modifications to published procedures that allow picrosirius red staining of thick 60-microm sections and their subsequent analysis by confocal microscopy. The use of phosphomolybdic acid pre-treatment was found to be essential for confocal analysis; in addition to preventing non-specific staining, it also quenched tissue autofluorescence. By incubating sections free-floating, pre-treating them with phosphomolybdic acid for 30 min and imaging them using an argon ion laser we were able to use confocal microscopy to image the entire depth of 60-microm human optic nerve and nerve head sections stained with picrosirius red. The application of this modified picrosirius red and confocal microscopy technique should be useful for analysing the three-dimensional structure of the optic nerve and other tissues with a similarly complex arrangement of connective tissue.

Adult↗
PubMed1999

Matrix and the retinal pigment epithelium in proliferative retinal disease.

In their normal state, RPE cell are strongly adherent to Bruch's membrane. Certain pathological conditions such as retinal detachment cause an injury-type response (probably augmented or induced by the local accumulation of a variety of substances which modulate cell behaviour) in which RPE begin to dissociate from the membrane. This RPE-Bruch's membrane separation may be mediated by proteins with counter-adhesive properties and proteolytic enzymes, partly derived from the RPE themselves. Concomitant with the RPE disassociation, the cells begin to lose tertiary differentiation characteristics and gain macrophage-like features. When the "free" RPE arrive at the surface of the neuroretina, they may attach to or create a provisional matrix. Some of the cells adopt a fibroblast-like phenotype. This phenotype is similar to that of the dermal fibroblast during cutaneous wound repair and the fibroblastic RPE synthesise the types of matrix components found in healing skin wounds. Many of these molecules in turn further modulate the activities of the cells via several families of cell surface receptors, while the RPE continue to remodel the new matrix with a range of proteolytic enzymes. The resulting tissue (or membrane) has many of the features of a contractile scar and is the hallmark of the condition known as proliferative vitreoretinopathy (PVR). Thus the development of PVR, and the resulting tractional distortion of the neuroretina, appears to be dependent on RPE-matrix interactions. The interactions present a number of potential therapeutic targets for the management of the disorder.

Animals↗
PubMed1999

Apoptosis in multinucleated skeletal muscle myotubes.

Several recent studies report endonuclease-mediated DNA degradation as evidence of apoptotic degeneration of skeletal muscle in the muscular dystrophies and other muscle disorders. Interpretation of the results of such studies is complicated by the ubiquitous presence of non-muscle cells within muscle in vivo and by a lack of knowledge concerning the nature of the process of apoptosis in postmitotic, multinucleated skeletal muscle and the potential mechanisms involved. Staurosporine treatment of C2C12 skeletal muscle myotubes induced several classic features of apoptosis, including cell and nuclear shrinkage with initial preservation of cellular membranes. Externalization of phosphatidylserine occurred within 2 hours of treatment, and myotubes contained procaspase 3, which seemed to be activated within 4 hours. DNA degradation was identified by transferase uridine triphosphate nick-end labeling within 4 hours, and DNA ladders were identified on agarose electrophoresis of genomic DNA within 8 hours. Thus, the process of apoptosis in postmitotic multinucleated skeletal muscle shares many of the characteristics of apoptosis in mononuclear mitotic cells. However, the pattern of degeneration does not seem to be compatible with that seen in the muscular dystrophies.

Animals↗
PubMed1998

Local effects of previous conjunctival incisional surgery and the subsequent outcome of filtration surgery.

PURPOSE: Previous ocular surgery involving conjunctival incision is a risk factor for failure of filtration surgery. To determine whether using adjunctive antimetabolite therapy may have a rational basis, a study was performed to determine whether the conjunctival cellular profile was altered by such surgery. METHODS: After a mean follow-up of 5.9 years, filtration surgery outcomes for 35 patients who had undergone conjunctival incisional surgery were retrospectively compared with 29 control and 18 matched patients who had not undergone such surgery. At the time of filtration surgery, a conjunctival biopsy specimen was obtained from all 82 patients, and these were quantitatively analyzed by light microscopy in a prospective manner. RESULTS: Trabeculectomy success for the control group (93%) was significantly higher than for the previous surgery group (38%) (P < .001). Compared with control tissue, conjunctiva from the patients who had undergone previous surgery contained more fibroblasts (P < .001, P < .05), macrophages (P < .01, P < .001), and lymphocytes (P = .001, P < .01) in both superficial and deep substantia propria (respective P values). Furthermore, trabeculectomy failure was associated with an increase in number of conjunctival fibroblasts in intraoperative specimens. CONCLUSIONS: Previous ocular surgery involving the conjunctiva increases the number of conjunctival fibroblasts and inflammatory cells. This may account for the increased risk of trabeculectomy failure. Perhaps on this basis, the use of adjunctive medication may be justified in patients who have undergone previous ocular surgery involving conjunctival incision.

Adolescent↗
PubMed1997

The three-dimensional structure of the connective tissue in the lamina cribrosa of the human optic nerve head.

Comprehensive understanding of the three-dimensional structure of the extracellular matrix (ECM) of the lamina cribrosa is central to understanding its role in health and disease, particularly how changes in configuration might precipitate nerve fibre death in glaucoma. Research until recently has relied almost entirely on light and scanning electron microscopy (SEM) to investigate the ECM of the lamina cribrosa. In this paper, we review the contribution of these methods to current understanding of the three-dimensional structure of the lamina ECM, highlight their potential weaknesses and emphasise that there is still much to be revealed about the structure of the lamina ECM. We then describe our development of confocal microscopy and computer reconstruction as a new and alternative method of investigating the three-dimensional structure of the lamina ECM. We show how optical sectioning allows the confocal microscope to acquire three-dimensional images of the lamina ECM without the degree of tissue disruption associated with preparation for SEM and demonstrate the versatility of analysis of these images by computer reconstructive software. A case is made for confocal microscopy and computer reconstruction contributing to our understanding of this important but complex and delicate structure.

Connective Tissue↗
PubMed1996

Reversal of topical antiglaucoma medication effects on the conjunctiva.

OBJECTIVE: To determine whether the adverse effects of antiglaucoma medications could be reversed before filtration surgery, potentially reducing the risk of subsequent failure. METHODS: One month before surgery, 30 patients who were receiving multiple antiglaucoma medications underwent an inferior bulbar conjunctival biopsy, ceased using sympathomimetic drops, and began treatment with topical corticosteroid, (1% fluorometholone four times daily). At the time of surgery two conjunctival biopsy specimens were obtained, one from the operation site (superior bulbar region), and one from the inferior bulbar region. The biopsy specimens were quantitatively analyzed by light microscopy. In addition, the outcome of first trabeculectomy for 16 of these patients was compared with that of 16 matched patients who had not undergone an altered preoperative regimen of topical therapy. RESULTS: During a 1-month period a notable decrease occurred in the number of fibroblasts and inflammatory cells throughout the conjunctiva. Inferior bulbar conjunctiva was found to be representative of superior bulbar conjunctiva with respect to these changes. Furthermore, evidence comparing the matched patients suggested that the altered preoperative regimen may have improved the success rate of trabeculectomy. CONCLUSIONS: The preoperative regimen used reversed the adverse conjunctival effect of topical medication. The regimen may be of clinical benefit in improving the success rate of trabeculectomy.

Administration, Topical↗
PubMed1996

Non-vascular vitreoretinopathy: the cells and the cellular basis of contraction.

BACKGROUND: We consider epiretinal membrane in terms of the two repair processes of gliosis and fibrosis and look at the cellular basis of contraction. METHODS: Pathological material removed at surgery was examined by a range of morphological procedures. Cultures of fibroblasts, retinal pigment epithelium cells and retinal glia were subjected to bioassays which relate to behavioural activities in scar formation. RESULTS AND CONCLUSIONS: Our findings highlight the importance of activities such as migration and adhesion in the formation of epiretinal membranes, and also show that these activities are central to our understanding of contraction.

Animals↗
PubMed1996

Ischemia-reperfusion-induced muscle damage. Protective effect of corticosteroids and antioxidants in rabbits.

We examined the potential protective effect of pretreatment with corticosteroids or antioxidants (ascorbic acid or allopurinol) in rabbits with reperfusion-induced damage to skeletal muscle after ischemia. 4 hours of limb ischemia induced by a pneumatic tourniquet, followed by reperfusion for 1 hour, caused a considerable amount of ultrastructural damage to the anterior tibialis muscles accompanied by a rise in circulating creatine kinase activity. Pretreatment of animals with depomedrone by a single 8 mg bolus injection led to a preservation of the anterior tibialis structure on both light and electron microscopy. High-dose continuous intravenous infusion with ascorbic acid (80 mg/hr) throughout the period of ischemia and reperfusion also preserved skeletal muscle structure, although allopurinol in various doses had no protective effect. These data are fully compatible with a mechanism of ischemia/reperfusion-induced injury to skeletal muscle, involving generation of oxygen radicals and neutrophil sequestration and activation. They also indicate that damage to human skeletal muscle caused by prolonged use of a tourniquet is likely to be reduced by simple pharmacological interventions.

Allopurinol↗
PubMed1996

Transscleral flow of aqueous humor: an in vitro experiment.

BACKGROUND AND OBJECTIVE: The minimal scleral flap thickness to ensure transscleral flow following a trabeculectomy has never been determined. The present study was designed to determine, in vitro, the critical scleral flap thickness that allows transscleral flow. MATERIALS AND METHODS: The apparatus consisted of two horizontal glass chambers (A and B) connected to each other by a customized scleral disc holder. High-pressure chamber A (at 25 mm Hg) was filled with sodium pertechnetate (99mTc) labeled normal saline and low-pressure chamber B (at 5 mm Hg) with normal saline. Transscleral flow of labeled normal saline from high-pressure chamber A via varying thickness scleral discs to low-pressure chamber B was observed over 16 hours using a gamma camera. Computer analysis was performed on the obtained images. RESULTS: Transscleral flow of labeled saline was observed only with scleral discs 0.5 mm thick or less. CONCLUSIONS: If the findings hold true for the in vivo situation, aqueous humor may reach the subconjunctival space following trabeculectomy via the transscleral route, provided scleral flap thickness is less than 0.5 mm. In addition, normal uveoscleral aqueous outflow may occur across sclera less than 0.5 mm thick, e.g., posterior to extraocular muscle insertions.

Aqueous Humor↗
PubMed1995

Migration of cultured bovine trabecular meshwork cells to aqueous humor and constituents.

PURPOSE: To investigate the migration of cultured bovine trabecular meshwork cells to aqueous humor and some of its constituents, and to compare the migration of normally proliferating and growth-arrested cells. METHODS: Cellular migration was evaluated in 48-well microchemoattraction chambers, and the chemoattractants used were bovine aqueous humor, glycoproteins, and growth factors. RESULTS: The meshwork cells responded well to bovine aqueous humor, and antibody neutralization experiments showed that fibronectin accounted for approximately 40% of aqueous chemoattraction. The glycoproteins laminin, thrombospondin, and transferrin elicited only modest migratory activity. Platelet-derived growth factor was the most powerful chemoattractant of the growth factors tested, and the others produced moderate migratory effects. Basic fibroblast growth factor was not chemoattractive on its own but stimulated migration when combined with heparin. Growth-arrested cells showed less migration to a standardized chemoattractive stimulus than did proliferating meshwork cells. CONCLUSIONS: For the first time, aqueous humor was shown to act as a migratory stimulus for meshwork cells in vitro. The major attractant is fibronectin; the remaining active constituents must still be identified.

Animals↗