Synaptic contacts between bipolar and photoreceptor cells in the retina of Callionymus lyra L.

A combined light and electron microscopic study of Golgi-impregnated retinas of the marine teleost Callionymus lyra L. revealed mixed bipolar cells (M types) contacting rods and cones and pure cone bipolar cells (C types). Five types of mixed bipolar cells can be differentiated on the basis of their synaptic contacts. Two out of the five mixed bipolar cell types contact double cones, single cones, and rods (mixed, dark, pale, single [Mdps and midget-Mdps]). Their endbuds make narrow cleft junctions, with each type of photoreceptor, and in addition, two endbuds end centrally in the synaptic ribbon complexes of the dark and pale double-cone pedicles. Three types of mixed bipolar cells contact only double cones and rods. The endbuds of one type (mixed, dark, pale, ribbon [Mdpr]) end centrally in the synaptic ribbon complexes of the dark and pale double-cone pedicles as well as of the rod spherules. The endbuds of two types (Mdp and midget-Mdp) make wide cleft junctions in dark and pale double-cone pedicles and in rod spherules. All pure cone bipolar cell types contact cones exclusively with narrow cleft junctions. Four types are seen: a type that contacts predominantly pale double-cone pedicles but also a few dark double-cone pedicles (Cp), a type that is connected with dark and pale double-cone pedicles in about equal numbers (Cdp), a type that makes synaptic contacts with pale double-cone pedicles and single-cone pedicles (Cps), and a type that is connected with both types of double cones and to single-cone pedicles (Cdps). A resemblance between the ultrastructural features of mixed bipolar cell synapses in Callionymus and in Carassius auratus is noted.

Synaptic contacts of the horizontal cells in the retina of the marine teleost, Callionymus lyra L.

The horizontal cell system in the retina of the fish Callionymus lyra L. was investigated light microscopically and electron microscopically. One type of rod horizontal cells, which are only found in the mixed ventral part, exclusively contacts spherules with lateral endknobs in the triads. Three types of cone horizontal cells occur. The first type, c-H1, contacts pedicles of pale and dark double cones and single cones. The processes always have a lateral position in the triads. This type has a constant contact pattern with the photoreceptor cells. The second type, c-H2, selectively contacts pedicles of pale double cones and the endbuds occupy a central position in the triads. In the single cone pedicles in the dendritic field of the c-H2 horizontal cell, the endbuds never seem to reach the triads. The third type, c-H3, only sends processes to pedicles of single cones where the endbuds occupy a central position in the triads. The synaptic connections of the horizontal cells of Callionymus differ from those observed in Nannacara anomala and Carassius auratus. The difference from the results obtained from Carassius is such that the information transfer model proposed for Carassius cannot apply to Callionymus.

New aspects of dopaminergic interplexiform cell organization in the goldfish retina.

Dopaminergic interplexiform cells (DA-IPCs) in the goldfish retina have been reexamined by light and electron microscopic immunocytochemistry with antisera against dopamine (DA) or tyrosine hydroxylase (TH). Successful immunostaining with a specific anti-DA antiserum offers further direct support for DA-IPCs. Anti-DA immunocytochemistry in combination with [3H]-DA autoradiography shows 92% colocalization of the two markers, indicating that [3H]-DA autoradiography is a reliable technique for identification of DA-IPCs. Incubations with anti-TH antiserum show that immunoreactive DA-IPCs have a homogeneous distribution, with an average frequency of 71 +/- 8 cells/mm2 in retinas of 14-15 cm long goldfish. Their arrangement is distinctly nonrandom. Electron microscopy of TH-immunoreactive cell processes confirms that horizontal cell axons synapse onto DA-IPCs and adds the following junctional arrangements to the circuit diagram of the DA-IPC: 1) adjacent serial synapses between DA-IPCs, external horizontal cells, and putative glycinergic interplexiform cells, 2) junctional appositions between DA-IPCs and photoreceptor cells, 3) junctional appositions between neighbouring DA-IPCs, and 4) the "gap junctional complex," typically consisting of a DA-IPC process juxtaposed with a gap junction between horizontal cell axons. The gap junction is flanked by clusters of small, round vesicles and groups of electron-dense structures resembling intermediate filaments. These morphological results support the functional involvement of DA-IPCs in adaptive retinomotor movements and in horizontal cell gap junction modulation and/or dynamics. They also suggest particular interaction between the dopaminergic and the glycinergic IPC system in the outer plexiform layer of goldfish retina.

Lymphocytes and Langerhans cells in the normal human cornea.

The distribution of B- and T-lymphocytes, of OKIa positive cells, and of HLA-ABC antigens in the normal cornea was investigated using monoclonal antibodies. The lymphocytes and Langerhans cells are present mainly in the well-vascularized limbic region but also occur albeit in small number in the center of the cornea. HLA-ABC antigens are strongly expressed on the epithelial cells of the cornea and the limbus.

The transitional zone between limbus and peripheral cornea. An immunohistochemical study.

PURPOSE: The authors investigated the phenotypic characteristics of basally located "transitional cells" in peripheral superior cornea, characterized previously by their coexpression of cytokeratin 19 and vimentin and their negativity for AE5. METHODS: Twenty adult human corneas were studied, using in situ immunohistochemical techniques and a panel of specific monoclonal antibodies against various surface and cytoplasmic molecules. RESULTS: The transitional cells shared staining characteristics with limbal basal cells in their expression of alpha 6 beta 4-integrin, metallothionein, AE1, and transferrin receptor. CONCLUSIONS: These "transitional" epithelial cells exhibit a unique phenotype differing from that of the surrounding basal epithelial cells in the peripheral cornea but analogous to that of limbal basal cells. These findings further corroborate the hypothesis that, at least from an immunohistochemical point of view, transitional cells in the superior peripheral cornea exhibit stem cell characteristics.

A new epithelial cell type in the human cornea.

PURPOSE: To study the expression of intermediate filaments in the human cornea. METHODS: Light and electron microscopic and immunohistochemical studies were performed on 20 corneas from subjects of various ages. RESULTS: A hitherto unrecognized epithelial cell population emerged from the immunohistochemical studies. Epithelial cells were invariably present in the superior cornea, whereas the nasal, temporal, and inferior segments almost lacked these cells. They were situated at the transition between peripheral cornea and limbus, and occurred as small groups in the basal epithelium. On electron microscopy, they were recognized by their marginated nuclear chromatin, large nucleoli, prominent bundles of intermediate filaments, and numerous hemidesmosomes and desmosomes. Immunohistochemistry on frozen sections revealed a unique intermediate filament make-up: ie, strong co-expression of vimentin and cytokeratin 19; other intermediate filaments, including cytokeratins 3, 4, 6, 7, 8, 10, 13, and 18 were negative. Finally, the cells lacked ultrastructural and immunohistochemical features of melanocytes, neuroendocrine cells, Langerhans' cells, and leukocytes. CONCLUSIONS: A new epithelial cell type in the human cornea is described with characteristic morphologic and immunohistochemical features. According to their particular segmental distribution, restricted localization at the junction between cornea and limbus, and expression of an "early" intermediate filament profile, it is tempting to speculate that they represent stem cells of the human cornea. Further studies are aimed to characterize their phenotype and function more extensively.

Distribution of very late activation integrins in the human cornea. An immunohistochemical study using monoclonal antibodies.

There is growing evidence that cellular adhesion mechanisms characterized by cell-cell and cell-matrix interactions are a fundamental process in the immunobiology of the cornea. Interactions with various extracellular matrix components are mediated by the very late activation (VLA) subgroup of the integrin superfamily of adhesion molecules. The six different VLA dimers known thus far consist of a common beta 1 subunit and a variable alpha (1 to 6) subunit. They serve as receptors for laminin (alpha 3 and alpha 6), collagen (alpha 2 and alpha 3), and fibronectin (alpha 4 and alpha 5). Using in situ immunohistochemistry and monoclonal antibodies, the distribution of the common beta 1 and the variable alpha-chains of VLA molecules was studied in normal human cornea and in cases with scarring or subepithelial/retrocorneal fibrous tissue. Epithelial cells were VLA-beta 1 and VLA-alpha 2, -alpha 3, -alpha 4, -alpha 5, and -alpha 6 positive. This is consistent with their intercellular adhesion and may aid in their attachment to the basement membrane which is composed of collagen, laminin, and fibronectin. Keratocytes in normal stroma expressed only the common beta 1-chain and no detectable alpha-chains. In regions of scar or fibrous tissue, however, an upregulated expression of the alpha-chains was detected. The VLA- alpha 1, -alpha 3, -alpha 4, and -alpha 5 were expressed in young fibrous tissue; in older lesions, VLA- alpha 1, -alpha 2, -alpha 3, -alpha 4, and -alpha 5 could be detected. The corneal endothelium showed a strikingly strong positivity for all VLA integrins.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneous induction of major histocompatibility complex class II antigens on corneal endothelium by interferon-gamma.

The expression and distribution of major histocompatibility complex (MHC) class II gene products, HLA-DR, HLA-DQ, and the HLA-DR invariant chain, were studied on flat mounts of human corneal endothelial cells (HCEC) after in vitro incubation of donor corneas with interferon-gamma (IFN-gamma), interleukin-1 (IL-1), and IL-6, using a sensitive immunoperoxidase technique with monoclonal antibodies. Control HCEC and endothelium treated with IL-1 or IL-6 completely lacked MHC class II antigens. After treatment with 50 U/ml, 100 U/ml, 500 U/ml, and 5000 U/ml of human IFN-gamma, a mosaic-like, patchy staining for all MHC class II products was observed: part of the HCEC showed membranous and/or cytoplasmic positivity; other endothelial cells were negative. In addition, a dose-dependent response to IFN-gamma was observed: the proportion of cells expressing class II products rose with increasing doses of IFN-gamma. The induction of MHC class II antigen expression on HCEC by IFN-gamma was completely inhibited by the addition of a neutralizing antibody directed to IFN-gamma but not by IL-1 beta. The significance of these findings with respect to corneal transplantation immunology is discussed.

Ocular penetration of (125I)IVDU, a radiolabeled analogue of bromovinyldeoxyuridine.

Following topical application of (125)IVDU, the radiolabeled analogue of bromovinyldeoxyuridine ([E]-5-[2-bromovinyl]-2'-deoxyuridine), as 0.5% or 0.3% eyedrops, to rabbits, (125I)IVDU appeared in the anterior chamber fluid at drug levels well above the minimum concentration (0.01 microgram/mL) required for inhibition of herpes simplex virus type 1 replication. These findings are consistent with the efficacy of 0.5% bromovinyldeoxyuridine eyedrops in the topical treatment of herpes simplex uveitis.

Risk factors for open-angle glaucoma: a case-control study.

The objective of this study was to identify possible risk factors associated with open-angle glaucoma (OAG). A case-control study included patients seen at an ophthalmologic clinic. Cases were all consecutive new patients with either unilateral or bilateral OAG detected during the study period. Controls were a random sample of all other patients aged 30 or more, seen in the same department in the same period. Data on demographic, anthropometric and diet habits as well as medical characteristics were collected from 144 patients by medical examination and interview. The study took place at the University Department of Ophthalmology and general private practice of ophthalmology, both in the city of Kinshasa. Forty consecutive patients with OAG and 104 controls were chosen randomly between all consecutive non OAG patients. Odds ratio (OR) are presented for the relation between OAG and age, sex, ethnicity, family history of glaucoma, the length of stay in Kinshasa, body mass index, hypertension, diabetes mellitus, cigarette smoking, alcohol, diet habits. Adjusted odds ratio resulting from stepwise logistic regression was employed. Results indicate: family history of glaucoma (OR, 18; 95% CI, 5.80-59.00; P < 0.001), age (OR, 1.05; 95% CI, 1.01-1.09; P = 0.025), body mass index (OR, 1.09; 95% CI, 1.01-1.18; P = 0.05), hyperopia (OR, 2.9; 95% CI, 1.05-7.08; P = 0.03), Mongo ethnic group (OR, 3.5; 95% CI, 1.11-12.20; P = 0.03) and consumption of rice (OR, 4.6; 95% CI, 1.65-12.20; P = 0.004) conferred a significantly greater risk of OAG. This study seems confirm that Mongo ethnic group is associated with an increased risk of OAG.

Efficacy of bromovinyldeoxyuridine in the treatment of herpes simplex virus and varicella-zoster virus eye infections.

As has been established in rabbits, (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) is superior to 5-iodo-2'-deoxyuridine (IDU) in the topical treatment of epithelial HSV-1 (herpes simplex virus type 1) keratitis, and superior to 5-trifluoromethyl-2'-deoxyuridine (TFT) in the topical treatment of deep stromal HSV-1 keratitis and HSV-1 uveitis. BVDU 0.1% eye drops have also proven efficacious in the treatment of patients with dendritic corneal ulcers, geographic corneal ulcers and stromal keratitis, and combined treatment of BVDU 0.1% eye drops with oral BVDU at 375 mg/day for 5 days led to a prompt healing of keratouveitis and skin lesions in patients with ophthalmic herpes zoster.

Topical treatment of experimental herpes simplex keratouveitis with 2'-O-glycylacyclovir. A water-soluble ester of acyclovir.

2'-O-glycylacyclovir, a water-soluble ester derivative of acyclovir, has proved efficacious in the topical treatment of epithelial and stromal herpes simplex keratitis, and iritis therewith associated, when administered as a 1% eyedrop formulation to rabbits.

Effect of topical acyclovir therapy on experimental herpes simplex keratouveitis.

Stromal keratitis and associated iritis were produced in rabbit eyes with the intrastromal injection of live herpes simplex virus. Treatment with 3% acyclovir and 2% trifluridine eye ointments was initiated one day after infection and continued for five consecutive days. These therapies significantly suppressed the development of keratouveitis compared with a placebo ointment. The suppressive action of trifluridine ointment on keratouveitis was significantly more pronounced than that of acyclovir ointment.

Pseudotumor orbitae and myasthenia gravis. A case report.

A case of myasthenia gravis in association with benign orbital pseudotumor of lymphoid origin is described. To our knowledge, this is the second report of such a case.

Experimental stroma herpes simplex keratitis. Influence of treatment with topical bromovinyldeoxyuridine and trifluridine.

Two compounds, bromovinyldeoxyuridine ([E]-5-[2-bromovinyl]-2'-deoxyuridine) and trifluridine (5-trifluoromethyl-2' deoxyuridine) were compared for their efficacy in the topical treatment of experimental stroma herpetic keratitis produced by the injection of live herpes simplex virus, type 1, into the corneal stroma of rabbits. The trifluridine was used as 1% eyedrops, whereas bromovinyldeoxyuridine was used as either 0.1% or 0.5% eyedrops. All three treatment regimens caused a substantial healing of stroma disease in comparison with placebo treatment. The bromovinyldeoxyuridine (whether used as 0.1% or 0.5%) proved superior to 1% trifluridine eyedrops when the treatment was started one day after virus inoculation. However, bromovinyldeoxyuridine and trifluridine were equally effective if the treatment was started seven days after infection. The 0.5% bromovinyldeoxyuridine eyedrops seemed to be more effective in controlling the complicating severe iritis and secondary glaucoma than either 0.1% bromovinyldeoxyuridine or 1% trifluridine. No toxic effects were observed with bromovinyldeoxyuridine in any eye, whereas 1% trifluridine produced punctate epitheliopathy in some eyes.

Gelatinase B in vernal keratoconjunctivitis.

OBJECTIVES: To investigate the expression of gelatinase B in the conjunctiva of patients with vernal keratoconjunctivitis (VKC) and the cellular source of this enzyme. METHODS: Conjunctival biopsy specimens from 12 patients with active VKC and 12 control subjects were studied using immunohistochemical techniques and a monoclonal antibody against gelatinase B. The phenotype of gelatinase B(+) inflammatory cells was examined using double immunohistochemical analysis and monoclonal antibodies against eosinophil peroxidase or macrophage CD68. Quantitative zymography was used to compare the activity of gelatinase B in conjunctival biopsy specimens from 10 patients with active VKC and 7 control subjects. RESULTS: Gelatinase B was detected in a few polymorphonuclear cells in 8 control specimens. All VKC specimens showed gelatinase B immunoreactivity in the epithelial and stromal inflammatory infiltrate. Compared with control specimens, VKC specimens showed significantly more gelatinase B-positive cells (mean +/- SD, 40.8 +/- 29.9 vs 10.3 +/- 2.4; P<.02). Most gelatinase B-positive cells were eosinophils (90.2% +/- 3.6%). Zymography revealed that gelatinase B levels in VKC specimens were significantly higher than the levels found in normal conjunctiva (3780.3 +/- 3541.0 vs 610.1 +/- 397.1 scanning units; P<.03). CONCLUSIONS: These findings suggest overexpression of gelatinase B by eosinophils in VKC specimens and participation of gelatinase B in the pathologic changes in VKC. CLINICAL RELEVANCE: Control of the release and/or activation of gelatinase B in eosinophils may provide a new therapeutic strategy for treating VKC.

Glutamate-like immunoreactivity in the retina of a marine teleost, the dragonet.

The localisation of endogenous glutamate in the dragonet retina was investigated by light microscopic postembedding silver-enhanced immunogold labeling after incubation with an anti-glutamate antiserum. Rod and cone inner segments and synaptic terminals, as well as the inner plexiform layer, are moderately labeled. Bipolar cells and ganglion cell bodies show strong labeling. In the dorsal inner plexiform layer, the levels with square-patterned bipolar synaptic boutons can be identified by their prominent glutamate-immunoreactivity. These results support the idea that the majority of the neurons that constitute the direct, centripetal pathways through the retina use glutamate as their neurotransmitter.

A subgroup of bipolar cells in human retina is GABA-immunoreactive.

The distribution of GABA in the perifoveal and the near and far peripheral region of human retina was studied with peroxidase anti-peroxidase immunocytochemistry applied on semithin epoxy resin sections. Among the labeled amacrine cells in these regions, four types can be identified: putative diffuse A2 amacrines, stratified semilunar amacrines, interstitial amacrines and small displaced amacrines. GABA-immunoreactive interplexiform cells and ganglion cells also occur. Contrary to previous post-embedding studies, our preparations show that some bipolar cells in the near and far peripheral region are GABA-immunopositive. This indicates that a number of bipolar cells in human retina does have an enhanced GABA content.

The replica technique used to study superficial corneal epithelium in vivo.

We used 2.15 to 2.3% collodion in amyl acetate to form a replica of the corneal surface epithelium in vivo in seven rabbit eyes and ten human eyes. When it was peeled off the replica removed superficial epithelial cells in patches. The corneal epithelium regenerated within one week. Repeated applications at weekly intervals for three months produced no harmful long-term effects in five rabbit corneas as evaluated with slit-lamp biomicroscopy, histological methods, and vital staining of the endothelium. In ten human eyes, the technique was harmless and chemically cauterized the dendritic herpetic ulcers. We studied the replicas and cells by conventional histological methods and electron microscopy. The preservation of cells was fairly good even for ultrastructural study.

An immunohistochemical study of topical cyclosporine in vernal keratoconjunctivitis.

PURPOSE: To determine the immunomodulating effects of topical cyclosporine on the immune cells in the conjunctival biopsy specimens obtained from patients with active vernal keratoconjunctivitis. METHODS: We studied six patients who had severe active vernal keratoconjunctivitis. Each patient was given topical cyclosporine 2% eyedrops four times daily. A 2 x 2-mm limbal conjunctival biopsy specimen was obtained from each patient before and three weeks after treatment. Using a panel of monoclonal and polyclonal antibodies and immunohistochemical techniques, we analyzed the conjunctival immune cells before and after cyclosporine treatment. RESULTS: Three weeks after topical cyclosporine treatment, there was marked clinical improvement and a statistically significant reduction in the number of epithelial and stromal class II MHC+ cells, UCHL1+ T cells, and stromal IgA+ and IgG+ plasma cells. The mean number of cells before and after therapy, respectively, were: class II MHC+ (epithelium), 31.5 +/- 13.1 and 8.3 +/- 5.6 (P = .031); class II MHC+ (stroma), 77.0 +/- 28.7 and 24.7 +/- 17.5 (P = .031); UCHL1+ T cells (epithelium), 24.5 +/- 14.1 and 4.2 +/- 2.9 (P = .031); UCHL1+ T cells (stroma), 78.7 +/- 31.1 and 44.5 +/- 27.5 (P = .031); IgA+ plasma cells, 66.7 +/- 32.1 and 22.2 +/- 7.8 (P = .031); and IgG+ plasma cells, 37.3 +/- 30.0 and 9.0 +/- 6.4 (P = .031). There was a statistically insignificant decrease in the epithelial class II MHC+ dendritic Langerhans cells, epithelial and stromal KP1+ macrophages, stromal OPD4+ helper/inducer T cells, and stromal L26+ B cells. The numbers of IgE+ plasma cells and mast cells were unaltered. CONCLUSION: The clinical improvement in vernal keratoconjunctivitis after topical cyclosporine therapy may result from its immunomodulating effect on the components of cell-mediated and humoral immune responses. In contrast, the drug has no immunomodulatory effect on mast cells and IgE-mediated allergic response.