Antimicrobial defensin peptides of the human ocular surface.
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BACKGROUND/AIMS: The antimicrobial activity of the tear film exceeds the activity of its known constituents. The authors postulate that this excess activity is the result of antimicrobial peptides called defensins, and they aimed to look for defensins in the human eye. METHODS: Evidence of defensin production was sought by reverse transcriptase polymerase chain reaction (RT-PCR). Intron spanning primers were designed for beta defensins 1 and 2, and alpha defensins 5 and 6. RT-PCR was performed on cornea, conjunctiva, and lacrimal gland samples, and reaction products were size fractionated and sequenced to confirm their identity. A monoclonal antibody was utilised for the detection of alpha defensins 1, 2, and 3 in tissue sections and in immunoblots of tears. RESULTS: RT-PCR revealed beta defensin 1 message in samples of conjunctiva, cornea, and lacrimal gland. beta Defensin 2 message was detected in the conjunctiva and cornea but was absent from the lacrimal gland. alpha Defensin 5 and 6 message was absent in these tissues but alpha defensins 1, 2, and 3 were detected in normal tears, lacrimal gland, and inflamed conjunctiva by immunochemistry. CONCLUSION: The data suggest the human eye innately produces a spectrum of antimicrobial defensin peptides. Defensins hold therapeutic potential in ocular infections as they have a broad spectrum of antimicrobial activity (bacteria fungi and viruses ) and accelerate epithelial healing. (+info)
Keratinocyte growth factor (KGF), also called fibroblast growth factor-7, is widely known as a paracrine growth and differentiation factor that is produced by mesenchymal cells and has been thought to act specifically on epithelial cells. Here it is shown to affect a new cell type, the microvascular endothelial cell. At subnanomolar concentrations KGF induced in vivo neovascularization in the rat cornea. In vitro it was not effective against endothelial cells cultured from large vessels, but did act directly on those cultured from small vessels, inducing chemotaxis with an ED50 of 0.02-0.05 ng/ml, stimulating proliferation and activating mitogen activated protein kinase (MAPK). KGF also helped to maintain the barrier function of monolayers of capillary but not aortic endothelial cells, protecting against hydrogen peroxide and vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) induced increases in permeability with an ED50 of 0.2-0.5 ng/ml. These newfound abilities of KGF to induce angiogenesis and to stabilize endothelial barriers suggest that it functions in microvascular tissue as it does in epithelial tissues to protect them against mild insults and to speed their repair after major damage. (+info)
Colchicine causes excessive ocular growth and myopia in chicks.
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Colchicine has been reported to destroy ganglion cells (GCs) in the retina of hatchling chicks. We tested whether colchicine influences normal ocular growth and form-deprivation myopia, and whether it affects cells other than GCs. Colchicine greatly increased axial length, equatorial diameter, eye weight, and myopic refractive error, while reducing corneal curvature. Colchicine caused DNA fragmentation in many GCs and some amacrine cells and photoreceptors, ultimately leading to the destruction of most GCs and particular sub-sets of amacrine cells. Colchicine-induced ocular growth may result from the destruction of amacrine cells that normally suppress ocular growth, and corneal flattening may result from the destruction of GCs whose central pathway normally plays a role in shaping the cornea. (+info)
The role of optical defocus in regulating refractive development in infant monkeys.
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Early in life, the two eyes of infant primates normally grow in a coordinated manner toward the ideal refractive state. We investigated the extent to which lens-induced changes in the effective focus of the eye affected refractive development in infant rhesus monkeys. The main finding was that spectacle lenses could predictably alter the growth of one or both eyes resulting in appropriate compensating refractive changes in both the hyperopic and myopic directions. Although the effective operating range of the emmetropization process in young monkeys is somewhat limited, the results demonstrate that emmetropization in this higher primate, as in a number of other species, is an active process that is regulated by optical defocus associated with the eye's effective refractive state. (+info)
Purine analogue 6-methylmercaptopurine riboside inhibits early and late phases of the angiogenesis process.
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Angiogenesis has been identified as an important target for antineoplastic therapy. The use of purine analogue antimetabolites in combination chemotherapy of solid tumors has been proposed. To assess the possibility that selected purine analogues may affect tumor neovascularization, 6-methylmercaptopurine riboside (6-MMPR), 6-methylmercaptopurine, 2-aminopurine, and adenosine were evaluated for the capacity to inhibit angiogenesis in vitro and in vivo. 6-MMPR inhibited fibroblast growth factor-2 (FGF2)-induced proliferation and delayed the repair of mechanically wounded monolayer in endothelial GM 7373 cell cultures. 6-MMPR also inhibited the formation of solid sprouts within fibrin gel by FGF2-treated murine brain microvascular endothelial cells and the formation of capillary-like structures on Matrigel by murine aortic endothelial cells transfected with FGF2 cDNA. 6-MMPR affected FGF2-induced intracellular signaling in murine aortic endothelial cells by inhibiting the phosphorylation of extracellular signal-regulated kinase-2. The other molecules were ineffective in all of the assays. In vivo, 6-MMPR inhibited vascularization in the chick embryo chorioallantoic membrane and prevented blood vessel formation induced by human endometrial adenocarcinoma specimens grafted onto the chorioallantoic membrane. Also, topical administration of 6-MMPR caused the regression of newly formed blood vessels in the rabbit cornea. Thus, 6-MMPR specifically inhibits both the early and the late phases of the angiogenesis process in vitro and exerts a potent anti-angiogenic activity in vivo. These results provide a new rationale for the use of selected purine analogues in combination therapy of solid cancer. (+info)
Effect of thiol-oxidation of glutathione with diamide on corneal endothelial function, junctional complexes, and microfilaments.
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Intracellular-reduced glutathione (GSH) was removed by thiol-oxidation with diamide during in vitro perfusion of the corneal endothelium. By 15 min the normal mosaic-like pattern of the endothelial cells was disrupted by serpentine-like lines of cell separation at the cell juntions. After 45 min of perfusion, infividual clusters of cells formed cup-shaped islands. The resultant exposure of Descemet's membrane to the perfusion solution resulted in corneal swelling. Transmission electron microscopy revealed that the endothelial cells separated at the apical junctions and that the microfilaments in the apical cytoplasm of cells formed dense bands, whereas the other subcellular organelles were normal in appearance. The change in cellular shape may be due to loss of cellular adhesion which results in the condensation of the microfilaments or contraction of the microfilaments. The addition of glucose to the perfusate prevented the diamide effect, and the diamide effect could be reversed upon removal and perfusion of a glutathione bicarbonate Ringer's solution. These results suggest that the ratio of reduced to oxidized glutathione in the endothelial cells plays a role in the maintenance of the endothelial cell barrier function. (+info)
Changes in corneal wavefront aberrations with aging.
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PURPOSE: To investigate whether corneal wavefront aberrations vary with aging. METHODS: One hundred two eyes of 102 normal subjects were evaluated with videokeratography. The data were decomposed using Taylor and Zernike polynomials to calculate the monochromatic aberrations of the cornea for both small (3-mm) and large (7-mm) pupils. RESULTS: For a 3-mm pupil, the amount of total aberrations (Spearman rank correlation coefficient r(s) = 0.145; P = 0.103) and spherical-like aberrations (r(s) = -0.068; P = 0.448) did not change with aging, whereas comalike aberrations exhibited a weak but statistically significant correlation with age (r(s) = 0.256; P = 0.004). For a 7-mm pupil, total aberrations (r(s) = 0.552; P < 0.001) and comalike aberrations (r(s) = 0.561; P < 0.001) significantly increased with aging, but spherical-like aberrations showed no age-related changes (r(s) = 0.124; P = 0.166). Simulated pupillary dilation from 3 mm to 7 mm caused a 38.0+/-28.5-fold increase in the total aberrations, and the extent of increases significantly correlated with age (r(s) = 0.354; P < 0.001). Pupillary dilation influenced the comalike aberrations more in the older subjects than in the younger subjects (r(s) = 0.243; P = 0.006), but such age dependence was not found for spherical-like aberrations (r(s) = 0.141; P = 0.115). CONCLUSIONS: Comalike aberrations of the cornea correlate with age, implying that the corneas become less symmetrical along with aging. Spherical-like aberrations do not vary significantly with aging. Pupillary dilation markedly increases wavefront aberrations, and those effects are more prominent in older subjects than in younger subjects. (+info)
Effect of PDGF, IL-1alpha, and BMP2/4 on corneal fibroblast chemotaxis: expression of the platelet-derived growth factor system in the cornea.
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PURPOSE: The purpose of this study was to examine expression of platelet-derived growth factor (PDGF) and PDGF receptors in the human cornea and to study the effects of the PDGF isotypes on proliferation and chemotaxis of human corneal fibroblasts. The effects of interleukin (IL)-1alpha, bone morphogenic protein (BMP)2, and BMP4 on chemotaxis of human corneal fibroblasts were also studied. METHODS: mRNA expression was monitored with reverse transcription-polymerase chain reaction (RT-PCR) in primary cultured cells. Protein expression in fresh-frozen human corneal sections was studied with immunocytology. Chemotaxis was measured using a modified Boyden chamber, and proliferation was quantitated by cell counting. RESULTS: PDGF A, PDGF B, PDGF receptor alpha, and PDGF receptor beta mRNAs were detected in corneal epithelial cells, fibroblasts, and endothelial cells in culture. The proteins were expressed in each major cell type in human corneal sections, with PDGF A and PDGF B detected at high levels in the epithelial basement membrane. PDGF, BMP2, and BMP4 had attractive chemotactic effects on corneal fibroblasts, with the PDGF BB dimer having a significantly greater positive chemotactic effect than the other PDGF isotypes. Interleukin-1alpha had a repulsive chemotactic effect on corneal fibroblasts. PDGF AA, AB, and BB stimulated proliferation of human corneal fibroblasts. CONCLUSIONS: The PDGF growth factor receptor system is expressed in the human cornea. PDGF, BMP2, BMP4, and IL-1alpha may modulate keratocyte chemotaxis and proliferation during homeostasis and wound healing. (+info)