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R Beuerman

Publications and source records attributed to R Beuerman.

10 recordsLinked to original sources
PubMed2006

Expression of insulin-like growth factor binding protein-3 in pterygium tissue.

BACKGROUND: Pterygium is a fibrovascular overgrowth from the conjunctiva onto the cornea. The pathogenesis of this common ocular surface disorder is not well understood and the only treatment is surgical removal. METHODS: DNA microarray analysis of primary pterygium tissue was carried out using uninvolved conjunctiva tissue as a comparison for gene expression levels. Real time polymerase chain reaction (PCR) was used to verify the mRNA level of expression for genes changed in pterygium. Western blot analysis and immunohistochemistry showed protein expression levels and the tissue distribution. RESULTS: Microarray analysis revealed that mRNA levels of a number of genes were changed in primary pterygium. In particular the gene for insulin-like growth factor binding protein-3, (IGFBP3), which modulates the effects of insulin-like growth factor on cells was significantly decreased. Both the message and protein expression of IGFBP3 in pterygium were decreased compared to normal, uninvolved conjunctiva. CONCLUSION: Decreased levels of IGFBP3 protein have been strongly correlated with the presence of cancer. Identification of the low level of expression of IGFBP3 in pterygium suggests that the pathway controlling cell proliferation has lost an important control mechanism, which may explain the continued growth of pterygium.

Adult↗
PubMed1997

Herpes simplex virus type-1 infection of corneal epithelial cells induces apoptosis of the underlying keratocytes.

The purpose of this study was to determine whether primary corneal infection with Herpes simplex virus (HSV)-1 induces keratocyte apoptosis in the rabbit. New Zealand white rabbit eyes were inoculated with HSV-1 strain 17 Syn+. Rabbits that developed slit lamp signs of epithelial infection were killed between 12 and 120 hr post infection. One cornea of each animal was fresh-frozen for TUNEL assay to detect DNA fragmentation in situ. The other cornea was fixed for transmission electron microscopy (TEM). Mechanical scrape wounded rabbit corneas were included as positive controls. DNA fragmentation consistent with apoptosis was detected in anterior keratocytes of corneas at 18, 24, and 48 hr after primary infection with HSV-1 and 2 hr after an epithelial scrape, but not in unwounded control corneas. Electron microscopic evidence of keratocyte apoptosis that included chromatin condensation, chromatin fragmentation, and cellular blebbing with formation of membrane bound cell fragments was detected in mechanical scrape wounded corneas and infected rabbit corneas at 12, 18, 24, 48, and 120 hr after infection, but not in unwounded control corneas. This study suggests that anterior stromal keratocyte apoptosis occurs following primary HSV-1 infection of the corneal epithelium. Previous studies have demonstrated that corneal epithelial scrape wounds induce apoptosis in the underlying keratocyte cells. We hypothesize that soluble mediators released by epithelial injury mediate anterior keratocyte apoptosis and that one of the physiologic functions of this epithelial-stromal apoptosis system is to limit viral extension.

Animals↗
PubMed1992

Effect of growth factors on collagen lattice contraction by human keratocytes.

A three-dimensional gel contraction model was used to evaluate interactions between human keratocytes and different kinds of collagen in the presence or absence of various growth factors. Bovine collagen type I or human placental copolymerized collagen type I/III was used to create the lattices. Normal keratocytes from neonatal, aged, and insulin-dependent diabetic donors, as well as abnormal keratocytes from a donor with macular corneal dystrophy, were cultured. Growth factors included epidermal growth factor (EGF), basic fibroblastic growth factor (FGF), insulin-like growth factor (IGF-I), and platelet-derived growth factor homodimer beta beta (PDGF). Gel area and optical transmittance were determined from computerized measurements. Dose-response experiments (0.01-100 ng/ml) demonstrated that PDGF at 10 ng/ml (P less than 0.005) and EGF at 1 and 10 ng/ml (P less than 0.0001) were the most effective in promoting gel contraction, compared to IGF-I and FGF. Comparison of cell strains revealed different dose-response profiles. Cells from insulin-dependent diabetics and cells from a donor with macular dystrophy contracted lattices more rapidly than cells from normal neonates (P less than 0.0001). Lattices of copolymerized human collagen type III/I demonstrated significantly reduced contraction rates (P less than 0.0001) and increased optical transmittance, compared to bovine collagen type I lattices. Ultrastructural studies revealed that keratocytes extend processes to form a network within the collagen lattice. Specialized intercellular junctional complexes were observed by transmission electron microscopy. This model provides a useful in vitro corneal stroma-equivalent for the study of keratocyte, extracellular matrix, and growth factor interactions.

Adolescent↗
PubMed1988

Pharmacokinetics and safety of transcorneal iontophoresis of tobramycin in the rabbit.

Transcorneal iontophoresis of tobramycin in normal eyes of New Zealand white rabbits was compared to an eye cup control and application of fortified topical drops. Iontophoresis was performed with 25 mg/ml of tobramycin at 0.8 mAmps for 10 or 5 min. The eye cup with 25 mg/ml of tobramycin was placed on the eye for 10 min without current. Topical fortified drops (13.6 mg/ml) were applied every half hour for 4 hr. Epithelium, stroma, and aqueous humor were assayed separately at 1, 4, 8 and 16 hr after treatment. The eyes were examined using the slit-lamp biomicroscope before and immediately after the treatment, and prior to sacrifice. Two eyes were examined by light and scanning electron microscopy 5 and 10 min after iontophoresis. Iontophoresis yielded significantly higher tobramycin concentrations than the eye cup or fortified topical drops at 1 hr and 4 hr after treatment (P = 0.001). In all treated eyes, iontophoresis resulted in epithelial edema and mucous discharge, which resolved by 24 hr after the treatment. Histologically there was evidence of epithelial disruption in the superficial layer after 5 min of iontophoresis and in all layers of the epithelium after 10 min of iontophoresis. Iontophoresis is a relatively safe, effective method to deliver medications to ocular tissues and may be useful alone or as an adjunct to current modes of antimicrobial chemotherapy.

Animals↗
PubMed1987

Immunohistochemical differentiation of Schwann and epithelial basal lamina in the rabbit cornea.

Transmission electron microscopy has shown that at the point of entry of axons into corneal epithelium, Schwann cell lamina densa merges with lamina densa of epithelial origin. Staining properties and the thickness of lamina densa from these sources are similar. Immunostaining with monoclonal antibodies to laminin and type IV collagen revealed that while Schwann cell basal lamina fluoresced to both of these probes, epithelial basal lamina was visualized only with anti-laminin. Monoclonal antibodies to neurofilament protein (70 and 200 kDa) were used to visualize the neural tissue. Segments of the deep stromal and subepithelial innervation appeared similar to those seen following gold chloride impregnation. The results suggest that intercalation of lamina densa from these tissue sources and regulation of the production of basal lamina components by both the epithelial and the Schwann cells probably occur.

Animals↗
PubMed1987

Effects of steroidal and non-steroidal anti-inflammatory agents on corneal wound healing.

This study was designed to compare corticosteroids with ketorolac, a non steroidal anti-inflammatory drug on corneal wound healing in rabbits. The present studies indicate that 0.5% ketorolac does not significantly impair wound healing as determined by corneal tensile strength, whereas 0.1% solution of dexamethasane phosphate resulted in a significant impairment of wound healing. In addition, ketorolac does not impair healing of corneal epithelial abrasion, whereas prednisolone acetate was found to impair wound healing. The development of a non-steroidal anti-inflammatory drug such as ketorolac provides an alternative method to suppress post-surgical inflammation and does not adversely affect the cellular system involved in corneal repair.

Animals↗
PubMed1985

Cryogenic lesion alters the metabolism of arachidonic acid in rabbit cornea layers.

The metabolism of radiolabeled arachidonic acid in epithelium, stroma, and endothelium was studied in normal and cryogenically lesioned rabbit corneas. The synthesis of cyclooxygenase- and lipoxygenase-reaction products, as well as the incorporation of arachidonic acid in phospholipids and neutral lipids, was followed by in vitro incubation (60 min) of corneas obtained 2 hr, 5 days, and 15 days after injury. In unwounded controls, prostaglandin E2 (PGE2) was the major cyclooxygenase product formed in the stroma, whereas thromboxane B2 predominated in the endothelium and epithelium. The major lipoxygenase product detected under these conditions in the epithelium was mono-hydroxyeicosatetraenoic acid (mono-HETE) and in the stroma, 12-HETE. In contrast, lipoxygenase products could not be detected in control endothelium. Two hours after injury, the labeling of lipids in epithelium and endothelium decreased; the largest decrease was in phosphatidylinositol, followed by phosphatidylcholine and phosphatidylethanolamine. At the same time, cyclooxygenase-reaction products in the epithelium increased, particularly PGF2 alpha. Prostaglandin levels in the stroma rose rapidly after injury and remained elevated for 15 days. In the endothelium, increases in PGF2 alpha and PGE2 were the most prominent effects of injury. After wounding, lipoxygenase products appeared for the first time in the endothelium and increased in the stroma and epithelium. Within 2 hr after lesioning, 12-HETE and 5-HETE increased in stroma. These studies show that the metabolism of arachidonic acid is altered by cryogenic injury and that the resulting changes differ in the three layers of the cornea. These changes involve arachidonoyl groups of phospholipids and cyclooxygenase and lipoxygenase products, and it is suggested that they are at least partly due to the migration of inflammatory cells to the wound site.

Animals↗
PubMed1982

A technique for controlled sensory denervation of the rabbit cornea.

Complications arising from the procedure to produce denervation of the cornea have made experiments on the trophic role of trigeminal nerve difficult. In this study, controlled lesions of the rabbit trigeminal ganglion were produced by radio-frequency thermocoagulation, delivered by a needle electrode inserted through the soft palate of the mouth. The advantages of the procedure were low mortality (less than 5%), permanent destruction of sensory neurons, and absence of spurious ocular effects. Two lesion sizes were reliably produced: 1. The smaller circumscribed lesion resulted in loss of corneal sensitivity, but preserved spontaneous blinking. 2. The larger lesion extended across the ganglion, abolished corneal sensation and spontaneous blink activity.

Animals↗
PubMedDate not supplied

Intracorneal lesions produced with focused ultrasound.

Focused ultrasound concentrates a large amount of ultrasonic energy into a small focal zone. We have used new techniques to develop a transducer that creates intracorneal, thermally induced lesions in rabbit eyes in vitro. Histologic study shows that these lesions are confined to the stroma and that the procedure causes no structural damage to the corneal epithelium or endothelium or other ocular structures. The potential uses of this device in corneal research and therapy are discussed.

Animals↗