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D Meller

Publications and source records attributed to D Meller.

At least 37 records · Page 2Linked to original sources
PubMed1998

Sialomucin complex at the rat ocular surface: a new model for ocular surface protection.

The ocular surface, which is among the most accessible and vulnerable tissues in mammals, is protected by a complex tear film composed of lipid, aqueous and mucin layers. In spite of its importance, the molecular nature of the mucin contribution remains uncertain. Since membrane mucins have been implicated in the protection of other epithelia, we have analysed rat corneal and conjunctival tissues for sialomucin complex (SMC), a membrane mucin found at the apical epithelial cell surfaces in the airway and uterus. Using Northern and Western blot analyses, SMC expression was found in both ocular tissues, being particularly abundant in the cornea. In contrast with the other known membrane mucin, MUC1, SMC was localized more heavily towards the apical surface of the epithelial cells. SMC in ocular surface epithelia was produced in both soluble and membrane forms, the latter being found predominantly in the most superficial cells and at apical surfaces. The soluble form was found loosely adsorbed to apical cell surfaces, particularly of the cornea, as indicated by a mild rinsing protocol. Finally, the tear fluid contained substantial amounts of SMC. From these results, we propose a new model for tear mucin components in which SMC is expressed at the apical ocular surface in both membrane-bound and adsorbed soluble forms to provide a direct protective barrier. SMC secreted into the tear fluid may also participate in maintaining the stability of the preocular tear film by acting with other secreted mucins to determine the physical properties and protective behaviour of the tear film.

Amino Acid Sequence↗
PubMed1998

Amniotic membrane transplantation with or without limbal allografts for corneal surface reconstruction in patients with limbal stem cell deficiency.

OBJECTIVE: To examine whether amniotic membrane transplantation (AMT), in preparing the perilimbal stroma, enhances the success of allograft limbal transplantation (ALT). METHODS: Thirty-one eyes of 26 consecutive patients had cytologically proven limbal deficiency resulting from chemical burns (14 eyes); Stevens-Johnson syndrome, toxic epidermal necrolysis, or pseudopemphigoid (5 eyes); contact lens-induced keratopathy (3 eyes); aniridia (3 eyes); multiple surgical procedures (2 eyes); atopy (2 eyes); or an unknown cause (2 eyes). Based on the severity of limbal deficiency, group A (mild), comprising 10 eyes, received AMT alone; group B (moderate), comprising 7 eyes, received AMT and ALT; and group C (severe), comprising 14 eyes, received AMT, ALT, and penetrating keratoplasty. All patients except those in group A received continuous oral cyclosporine. RESULTS: Except for the 2 eyes with atopy, all amniotic membrane-covered surfaces showed rapid epithelialization (in 2 to 4 weeks) and reduced inflammation, vascularization, and scarring, and the surfaces became smooth and wettable. For the mean follow-up period of 15.4 months, 25 (83%) of 30 eyes showed visual improvement, consisting of 6 or more lines (13 eyes), 4 to 5 lines (6 eyes), or 1 to 3 lines (6 eyes). Visual improvement decreased with the severity of limbal deficiency from 8 (100%) of 8 eyes in group A to 5 (71%) of 7 eyes in group B and 11 (79%) of 14 eyes in group C. In group C, corneal graft rejection occurred in 9 (64%) of 14 eyes, and reversible early limbal allograft rejection was noted in 3 (14%) of 21 eyes of groups B and C. CONCLUSIONS: For partial limbal deficiency with superficial involvement, AMT alone is sufficient and hence superior to ALT because there is no need to administer cyclosporine. For total limbal deficiency, additional ALT is needed, and AMT helps reconstruct the perilimbal stroma, with reduced inflammation and vascularization, which collectively may enhance the success of ALT.

Adult↗
PubMed1998

[Reconstruction of the conjunctival and corneal surface. Transplantation of amnionic membrane].

The ocular surface epithelia with the tear film as a unit provide clear vision and comfort and serve as the first line the defense. It is important to understand how ocular surface health is maintained and how ocular surface failure occurs. Furthermore, it is timely to summarize new information concerning action mechanisms and clinical uses of amniotic membrane transplantation for ocular surface reconstruction. When appropriately processed and preserved, amniotic membrane as a native matrix can be used as a graft to restore conjunctival surfaces following removal of lesions such as pterygium, tumor, scar, symblepharon, and conjunctivochalasis. It can also be used as a graft to restore corneal surfaces suffering from limbal stem-cell deficiency. For partial limbal deficiency, amniotic membrane alone is frequently sufficient, while for total limbal deficiency it needs to be combined with limbal stem-cell transplantation with or without corneal transplantation. When used as a graft or patch, amniotic membrane can facilitate healing of persistent corneal ulcers and recurrent corneal erosion and reduce corneal haze following keratectomy. Reported data indicate that amniotic membrane transplantation facilitates rapid healing with recovery of a normal epithelial phenotype in the epithelium and reduces inflammation, vascularization, and scarring in the stroma.

Biological Dressings↗
PubMed1998

Effects of different perfluorochemicals on dorsal root ganglion cells in vitro.

BACKGROUND: Investigation of the effects of different perfluorochemicals (PFC) on cultured dorsal root ganglion (DRG) cells. METHOD: DRG cell cultures from 9- to 11-day-old chicken embryos were exposed to emulsified perfluorodecalin (PFD; C10F18; 0.5%, 1% and 10%) or perfluorooctylbromide (PFO; C8F17Br; 0.5%, 1% and 10%). The cells were evaluated under phase-contrast optics after 30 h and 120 h for 0.5 and 1% and after 5 h for 10%. To study the integrity of neuronal cells, immunohistochemical labelling for neurofilaments (NF) and tubulin (TUB) was performed. RESULTS: Concentrations of 0.5% and 1% of PFD or PFO did not change immunohistochemical labelling of DRG cells. Co-cultured macrophages showed a foam cell response, presumably representing ingested PFC. At both concentrations PFD induced a weaker foam cell response than PFO. A concentration of 10% led to the death of DRG cells and macrophages within 5 h. CONCLUSION: PFC caused a dose-dependent damage of neuronal cells. Co-cultured macrophages developed a foam cell response similar to that observed in vivo after prolonged presence of PFC in the vitreous body. These observations indicate that PFD and PFO may not be suitable for long-term vitreous replacement in vitreoretinal surgery. However, the model is limited by several factors: (1) there are physiological differences between DRG cells and retinal ganglion cells; (2) in vivo retinal ganglion cells are protected by the overlying tissues; (3) the PFC used in tissue culture must be emulsified.

Animals↗
PubMed1997

Human cornea and sclera studied by atomic force microscopy.

The purpose of this study was to investigate the ultrastructure of the extracellular matrix of human cornea and sclera by using the atomic force microscope (AFM). Specimens of human cornea (n=16) and sclera (n=10) were obtained from a cornea bank or from enucleated eyes (n=1; clinical and histopathological diagnosis: choroidal melanoma) and fixed in Karnovsky solution. The AFM resolved individual collagen fibrils in corneal and scleral tissue. Scleral collagen fibrils had a diameter ranging from 118.3 to 1268.0 nm and showed clear banding with a mean axial D-periodicity of 77.02 nm. The mean gap depth between the two overlaps was larger in the sclera than in the cornea. The diameter of corneal collagen fibrils ranged from 48.0 to 113.0 nm. In contrast to the sclera, the corneal collagen fibrils did not exhibit clear banding as their surface pattern. Closely attached fibrils with a beaded to globular structure were predominant in the cornea. The mean axial D-periodicity of the corneal collagen fibrils was 68.50 nm. In both tissues, the AFM resolved structures resembling cross-bridges between adjacent fibrils. The corneal collagen fibrils showed fibrillar properties that were different from those of the sclera, and that therefore might be essential for the spatial organization responsible for the optical quality of the cornea.

Cornea↗
PubMed1997

Complications of misdiagnosed and inadequately treated necrotizing scleritis studied by ultrasound biomicroscopy and computerized corneal topography.

We present a case of misdiagnosed and inadequately treated necrotizing scleritis leading to ocular complications. Scleral thinning and a marked secondary corneal astigmatism were observed and measured by ultrasound biomicroscopy and corneal topography. The purpose of this case report is to demonstrate the clinical value of additional diagnostic tools, such as ultrasound biomicroscopy and corneal topography and to alert ophthalmologists as to the complications of necrotizing scleritis.

Astigmatism↗
PubMed1996

Effects of allopurinol and steroids on inflammation and oxidative tissue damage in experimental lens induced uveitis: a biochemical and morphological study.

AIMS: To evaluate the effects of allopurinol in lens induced uveitis (LIU) by morphological methods and to compare these effects with those of steroids and a combination of both drugs biochemically and morphologically. METHODS: Lipid peroxides (LPO) of the retinal tissue were determined by two different methods (thiobarbituric acid assay (TBA) and high performance liquid chromatography expressed as malondialdehyde-like substances). Myeloperoxidase (MPO) activity in the iris/ciliary body complex was analysed spectrophotometrically. Histological changes on three morphological levels of LIU eyes were evaluated. RESULTS: Both allopurinol and the combination of allopurinol/prednisolone led to a significant reduction in the increaed retinal LPO values. Prednisolone only revealed significant effects on retinal LPO when being measured with the TBA method. MPO activity in iris and ciliary body was significantly reduced in all therapy groups. The morphological evaluation of the sections by two masked investigators revealed a significant reduction (p < 0.05) in the inflammation score in all therapy groups. Morphometric studies using the QUANTIMED system (Leica, Cambridge) showed significantly reduced values (p < 0.05) in the allopurinol group and in the group receiving prednisolone and allopurinol. Prednisolone alone did not lead to a significant reduction in the values. CONCLUSIONS: The findings show that both allopurinol and steroids exert positive effects on the variables determined in LIU. The effects of steroids are believed to be mostly due to their direct action on inflammatory cells. The recently reported scavenging effects of methylprednisolone should play a minor role in this disease model. Allopurinol and oxypurinol act as direct scavengers of free radicals and hypochlorous acid, which is produced via MPO catalysis, thus leading to a reduction in tissue inflammation and tissue damage.

Allopurinol↗
PubMed1996

A modified technique of impression cytology to study the fine structure of corneal epithelium.

In this article, the development and application of a modified technique of impression cytology for the electron-microscopic examination of corneal epithelium is presented. Corneal epithelium of controls and diabetic patients was obtained using millipore filters, which had been presoaked with EDTA to weaken intercellular adhesions. Light and electron microscopy (EM) of the control samples showed sheets of well-preserved corneal epithelial cells. Therefore, this modified technique is supposed to be useful for the analysis of alterations of the corneal epithelium. EM of corneal cells of diabetic patients showed irregularly formed epithelial cells. The corneal epithelium of diabetic patients revealed thickening of the basement membrane and a decreased number of hemidesmosomes. The alterations observed in specimens of diabetic patients represent the morphological equivalent of an impaired epithelial barrier function, an increased fragility of epithelial lining and the disturbed healing properties occurring in diabetic keratopathy.

Adolescent↗
PubMed1995

Oxidative reactions in the tear fluid of patients suffering from dry eyes.

PURPOSE: To evaluate whether products of oxidative and inflammatory reactions are detectable in the tear fluid of patients suffering from dry eyes. METHODS: The tear fluid of 217 patients (397 eyes) was sampled. Criteria for grouping of the patients were (1) basic secretion test ("sicca 1": BST = 0-5 mm, n = 78 eyes; "sicca 2": BST = 6-10 mm, n = 109 eyes) and (2) subjective symptoms (normal BST, burning, foreign body sensations, tearing, dryness of the eyes: n = 78 eyes). One group of healthy patients (normal BST, n = 132 eyes) served as controls. Lipid peroxide levels and myeloperoxidase activity, as parameters for oxidative tissue damage and inflammatory activity, were determined in the tear fluid. Those patients whose consent could be obtained were subjected to the rose bengal test (sicca 1: 56 eyes; sicca 2: 97 eyes; subjective symptoms: 44 eyes; controls: 49 eyes). The correlation between BST and rose bengal test results was calculated. RESULTS: Lipid peroxides were significantly (P < 0.05) higher in the groups sicca 1 and subjective symptoms than in healthy controls, as was the inflammatory activity in groups sicca 1, sicca 2 and subjective symptoms. Additionally, the inflammatory activity in the group sicca 1 was significantly (P < 0.05) higher than in the groups sicca 2 and subjective symptoms. No evidence of a significant correlation between BST and rose bengal test results was observed. CONCLUSIONS: Both oxidative tissue damage and polymorphonuclear leukocytes indicating an oxidative potential occur in the tear film of patients suffering from dry eyes. These reactions lead to severe damage of the involved tissue. Free radicals and inflammation may be involved in the pathogenesis or in the self-propagation of the disease.

Dry Eye Syndromes↗
PubMed1995

Systemic effects of different perfluorochemical agents.

PURPOSE: An intravitreal injection of Fluosol-DA leads to a higher alteration of the macrophage system of the retina than perfluorooctane and perfluorodecalin administered by the same route. The difference may be due to different kinds of oxidative damage caused by the three chemicals. To test the validity of this assumption, the degree of cell alteration, expressed as reduction of cytoplasmic motility, caused by these three perfluorochemicals was examined. METHODS: Using the hepatic macrophage system of the rat, cell alteration was examined by magnetometry after intravenous application of various perfluorochemicals [emulsified perfluorodecalin (C10F18), perfluorooctane (C8F17Br) and Fluosol-DA (corresponding to a 20% emulsion of 70% perfluorodecalin and 30% perfluorotripropylamine, C9F21N)]. RESULTS: After administration of high doses, all perfluorochemicals led to cytoskeleton alteration. This alteration, expressed as retardation of the relaxation period of ferromagnetic iron oxide particles, was most pronounced after administration of Fluosol-DA. CONCLUSION: The compromising effect of perfluorochemicals is dose dependent and differs among the three compounds tested, with Fluosol-DA showing the greatest decrease in cytoplasmic motility.

Animals↗
PubMed1995

[Complex anterior chamber dysgenesis with bilateral corneal ectasia].

BACKGROUND: Sclerocornea is a congenital, uni- or bilateral, non-progressive, non-inflammatory malformation characterized by histological changes of the cornea resembling scleral tissue. CASE REPORT: We report the case of a 2-month-old child with bilateral dysplasia of the anterior segment including: 1. extreme corneal ectasia; 2. vascularized, opacified microcornea; 3. presence of rudimental limbus; 4. anterior scleral dysplasia. The axial length measured by means of ultrasonography (A-scan) was about 24 mm in both eyes. A penetrating keratoplasty was first performed in the right eye and one week later in the left eye. Intraoperatively an advanced iris atrophy with extensive anterior synechiae, as well as a localized anterior subcapsular cataract were seen bilaterally. A pale optic disk with a maximally enlarged optic cup could be seen only in the left eye. CONCLUSION: Although the histologic examination was compatible with the diagnosis of sclerocornea, the presence of atypical clinical findings previously unreported does not allow a definite classification of the case reported herein.

Anterior Chamber↗
PubMed1994

Transient immunohistochemical labelling of rat retinal axons during Wallerian degeneration by a monoclonal antibody to neurofilaments.

Immunohistochemical labelling with the monoclonal antibody SMI32 to non-phosphorylated epitopes on neurofilament proteins of high molecular weight class was low in rat central optic fibers of controls. After unilateral transection of optic nerve, a strong, transient increase of labelling with SMI32 occurred in degenerating fibers of optic tract at 2 and 4 days, which then declined at 8 and remained low at 21 days. Consequently, immunostaining with SMI32 may serve as a positive marker for degenerating fibers in rat optic system.

Animals↗
PubMed1994

Immunohistochemical markers for neurons and astrocytes show pan-necrosis following infusion of high-dose NMDA into rat cortex.

This study pertains to the transition between selective neuronal necrosis and the development of cerebral infarction (pan-necrosis). We infused the neuron selective excitotoxin N-methyl-D-aspartate (NMDA) at a relatively high concentration (10 microliters of 50 mM NMDA in phosphate buffer, pH 7.4) into the rat cortex. Local injection of lactic acid and a minor stab wound in the cortex were used as a reference. The tissue damage was evaluated with immunohistochemical markers for neurons (MAP2, parvalbumin) and for astrocytes (GFAP and S100 protein). The stab wound and infusion of lactic acid led to a small distinct area of pan-necrosis with a sharp border to the surrounding tissue. The NMDA lesions were characterized by a center of pan-necrosis with loss of all tissue elements that were larger and less distinctly demarcated than the other lesions. This study shows that activation of NMDA receptors per se can induce pan-necrosis, and we conclude that the transition from selective neuronal necrosis to infarction depends on the intensity of the neuronal damage process.

Animals↗
PubMed1994

[Chronic low grade endophthalmitis. A growing indication for explantation of intraocular lenses].

The aim of this study was to evaluate the effect of progress made in cataract surgery regarding the indications and results of intraocular lens (IOL) removal. For this purpose, the charts of all patients who had undergone IOL explantation at our institution between January 1990 and December 1992 were reviewed. Indications were divided into six groups: (a) chronic low-grade endophthalmitis; (b) pseudophakic bullous keratopathy; (c) luxation; (d) traumatic expulsion; (e) high-degree aniseikonia; (f) acute endophthalmitis. Visual acuities were grouped according to a good (1.0 to 0.5), acceptable (0.4 to 0.05) and poor (less than 0.05) outcome. Fifty-two IOL were removed from 52 eyes of 52 patients during the period considered in this study. Sixteen were anterior chamber, 5 were iris-fixated, and 31 were posterior chamber lenses. The removal rates were 30.8% for chronic, low-grade endophthalmitis (n = 16), 28.8% for bullous keratopathy (n = 15), 28.8% for luxation (n = 15), 5.8% for traumatic expulsion (n = 3), 3.8% for high-degree aniseikonia (n = 2), and 1.9% for acute endophthalmitis (n = 1). After explantation vision equal to or better than 20/400 was achieved by the vast majority of patients in all groups with the exception of those with bullous keratopathy. The progress made in cataract surgery over the last decade has greatly influenced the rate of complications leading to IOL removal. Continuous monitoring of explanted IOLs is mandatory to evaluate further changes in surgical technique and lens design.

Adolescent↗
PubMed1993

Immunohistochemical studies on neurofilamentous hypertrophy in degenerating retinal terminals of the olivary pretectal nucleus in the rat.

Following section of the optic nerve, degenerating retinal terminals reveal an accumulation of neurofilaments (neurofilamentous hypertrophy) as demonstrated by silver impregnation techniques or electron microscopy. The present study examined degenerating retinal terminals by means of immunohistochemistry and antibodies specific for the triplet of neurofilament proteins of low (NF-L), medium (NF-M), and high (NF-H) molecular weight class. Following unilateral optic nerve section in the rat and survival of 1, 2, 4, 8, and 21 days, brains were perfused with aldehyde fixative, sliced on a vibratome and stained for neurofilaments by using the peroxidase-antiperoxidase technique. Other brains were frozen, cut in the native state, and slide-mounted sections were fixed by acetone. Side comparisons in visual pathways were made in frontal sections, taking advantage of the near complete crossing of retinal fibers in the rat. Anterograde degeneration of axons occurred in the optic tract and branchium colliculi. Changes of terminals were investigated in the olivary pretectal nucleus, which contains a dense aggregation of retinal terminals in the core region. The optic tract and branchium colliculi showed a reduction in immunostaining for neurofilament proteins following axotomy. Within the core region of the olivary pretectal nucleus, strong increases of immunoreactivity of NF-L and NF-M were detected beginning at 2 days postlesion and persisting at 8 days. No changes in NF-H proteins were found in the terminal regions with three different antibody probes. The increase in immunostaining reflects the accumulation of neurofilament proteins in the degenerating retinal terminals, i.e., neurofilamentous hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Immunohistochemical studies with antibodies to neurofilament proteins on axonal damage in experimental focal lesions in rat.

Immunohistochemistry with monoclonal antibodies against neurofilament (NF) proteins of middle and high molecular weight class, NF-M and NF-H, was used to study axonal injury in the borderzone of focal lesions in rats. Focal injury in the cortex was produced by infusion of lactate at acid pH or by stab caused by needle insertion. Infarcts in substantia nigra pars reticulata were evoked by prolonged pilocarpine-induced status epilepticus. Immunohistochemical staining for NFs showed characteristic terminal clubs of axons in the borderzone of lesions. Differences in the labelling pattern occurred with different antibodies which apparently depended on molecular weight class of NFs and phosphorylation state. These immunohistochemical changes of NFs can serve as a marker for axonal damage in various experimental traumatic or ischemic lesions.

Animals↗
PubMed1993

A one-step immunohistochemical method for detection of blood-brain barrier disturbances for immunoglobulins in lesioned rat brain with special reference to false-positive labelling in immunohistochemistry.

Disturbances of the blood-brain barrier (BBB) following brain lesions lead to extravasation of serum proteins that can be detected by immunohistochemical methods in tissue sections. Here, extravasated immunoglobulins were visualized by a 1-step technique using rabbit anti-rat immunoglobulins conjugated to horseradish peroxidase (HRP). This method is associated with a lower background staining than the conventional 3-step peroxidase-antiperoxidase (PAP) technique using rabbit antibodies against rat whole-serum proteins or immunoglobulins (IgG). Further tests using a direct conjugate of rabbit anti-rat immunoglobulins to fluorescein isothiocyanate (FITC) showed usefulness of the approach for fluorescence microscopy. Additional experiments showed that antibodies directed against mouse immunoglobulins as used for detection of mouse monoclonal antibodies can cross-react with extravasated rat immunoglobulins. Therefore, immunohistochemical studies on lesioned rat brain should routinely include a visualization of areas containing extravasated serum proteins including immunoglobulins.

Animals↗