Human ocular mucus. Origins and preliminary characterisation

Moxifloxacin-Based Extended Depth-of-Field Fluorescence Microscopy for Real-Time Conjunctival Goblet Cell Examination

Conjunctival goblet cells (CGCs) are mucin-secreting cells in the eye and play essential roles for ocular surface homeostasis. Since various ocular surface pathologies are related to CGC dysfunction, CGC examination is important for the evaluation of ocular surface conditions. Recently we introduced moxifloxacin-based fluorescence microscopy (MBFM) for non-invasive CGC imaging. However, the imaging speed was up to 1 frame per second (fps) and needed to be improved for clinical applications. In this study, we developed a high-speed moxifloxacin-based, extended depth-of-field (EDOF) microscopy system that operates at a maximum imaging speed of 15 fps. The system used a deformable mirror for the high-speed axial sweeping of focal plane during single-frame acquisitions. The acquired images contained both in-focus and out-of-focus information, and deconvolution was used to filter the in-focus information. The system had a DOF of 800 [Formula: see text], field-of-view of 1.2 mm ×1.2 mm, and resolution of [Formula: see text]. Its performance was demonstrated by real-time, breathing-motion-insensitive CGC imaging of mouse and rabbit models, in vivo. High-speed EDOF microscopy has potentials for non-invasive, real-time CGC examinations of human subjects.

Morphology and Histology of the Orbital Region and Eye of the Asiatic Black Bear (Ursus thibetanus)—Similarities and Differences within the Caniformia Suborder

In this study, we present first data concerning the morphological observations of the orbital region, eye tunics, upper and lower eyelids, superficial gland of the third eyelid with the third eyelid, and lacrimal gland in captive adult male Asiatic black bear. The following research methods were used in the work: the eyeball morphometry, the orbital region description, macroscopic description, morphometric and histological analysis of the eye tunics and selected the accessory organs of the eye (Fontana–Masson, hematoxylin & eosin (H&E), Methyl-green-pyronin Y (MGP Y), Movat pentachrome, and picro-Mallory trichrome) as well as histochemical examination (PAS, AB pH 1.0, AB pH 2.5, AB pH 2.5/PAS and HDI). The eyeball of the Asiatic black bear was a spherical shape, while the periorbita was funnel/conical-shaped and the eye socket was of the open type. The cornea was absent of the Bowman’s membrane similar to all domestic dogs and some wild dogs. There were palisades of Vogt in the corneal limbus epithelium similar to the Canidae. Degenerative choroidal tapetum lucidum similar to ranch mink (Mustelidae) has been found. The pupil was big and round in shape. The ciliary muscle, dilatator and sphincter muscle were well developed, similar to the pinnipeds. The lens was biconvex round, similar to the Canidae. The retina was composed similarly to the diurnal terrestrial carnivores. In both eyelids were observed very well-developed tarsal glands, ciliary glands and sebaceous glands. The orbital zone in the eyelids was characterized by lymphoid follicles, diffuse lymphocytes and specialized high endothelial venules. In the anterior palpebral margin of the upper eyelid, soft and short eyelashes were observed, while in the lower eyelids they were absent. The third eyelid was T-shaped and composed of the hyaline tissue, and it contained CALT, similar to that in Canidae. The superficial gland of the third eyelid was a multilobar alveolar branched complex with seromucous nature, while the lacrimal gland was also a multilobar acinar branched complex gland, but producing a mucous–serous secretion. The results of our research indicate that the features of the anatomy of the eye and orbital region in Asiatic black bear are also typical of the Ursidae family. Moreover, a detailed analysis of the morphological eye region may be useful in comparative studies and veterinary diagnostics in this bear species.

Anatomical and morphometric evaluation of the orbit, eye tunics, eyelids and orbital glands of the captive females of the South African painted dog (Lycaon pictus pictus Temminck, 1820) (Caniformia: Canidae)

In this study, we present the first data concerning the anatomical, morphometrical, histological and histochemical study of the orbit, eye tunics, eyelids and orbital glands in South African Painted Dogs (Lycaon pictus pictus). The study was performed using eyeball morphometry, analysis of the bony orbit including its morphometry, macroscopic study, morphometry, histological examination of the eye tunics and chosen accessory organs of the eye and histochemical analysis. The orbit was funnel shaped and was open-type. There was a single ethmoid opening for the ethmoid nerve on the orbital lamina. The pupil was round, while the ciliary body occupied a relatively wide zone. The iris was brown and retina had a pigmented area. The cellular tapetum lucidum was semi-circular and milky and was composed of 14–17 layers of tapetal cells arranged in a bricklike structure. In the lower eyelid, there was a single conjunctival lymph nodule aggregate. One or two additional large conjunctval folds were observed within the posterior surface of the upper eyelids. The superficial gland of the third eyelid had a serous nature. The third eyelid was T-shaped and was composed of hyaline tissue. Two to three conjunctival lymph nodul aggregates were present within the bulbar conjunctiva of the third eyelid. The lacrimal gland produced a sero-mucous secretion. A detailed anatomic analysis of the eye area in the captive South African Painted Dogs females showed the similarities (especially in the histological examination of the eyetunics and orbital glands) as well as the differences between the Painted dog and the other representatives of Canidae. The differences included the shape and size od the orbita with comparison to the domestic dog. Such differences in the orbit measurements are most likely associated with the skull type, which are defined in relation to domestic dogs. The presented results significantly expand the existing knowledge on comparative anatomy in the orbit, eye and chosen accessory organs in wild Canidae.

A study on the morphoquantitative and cytological characteristics of the bulbar conjunctiva of the maned wolf (Chrysocyon brachyurus; Illiger, 1815)

The maned wolf, Chrysocyon brachyurus, is a near-threatened carnivore inhabiting the Brazilian Cerrado. Few studies have been conducted on this species, and even fewer have explored its ophthalmological characteristics. Vision is critical to wild canids; thus, this study aimed to provide a morphoquantitative description of the bulbar conjunctiva of the maned wolf using cytological and histological analyses. Ten healthy maned wolves from a conservational centre, including 4 females and 6 males aged 1-12 years (6.5 ± 2.8), were included in the study. The samples for cytological analysis were collected from the inferior conjunctival sac using a cytobrush, and conjunctival tissue was collected for histological analysis from the temporal canthus zone. The cytological samples were stained using the Papanicolaou method, and the histological sections were stained using haematoxylin and eosin, Periodic acid-Schiff, picrosirius red and Masson's trichrome stains. The cytological samples were studied for stain quality, and the different cell types were counted. Histological examination was used to determine tissue types in the conjunctiva and their proportions. Analyses revealed a stratified squamous epithelium with some goblet cells and eventual pigmentation in the basal layer. Loose connective tissue with the presence of some mononuclear and polymorphonuclear cells was also observed. The epithelium of the maned wolf's bulbar conjunctiva resembles that of dogs and other carnivore species; furthermore, its physiological and pathological responses were similar to those of other carnivore species.

Moxifloxacin based axially swept wide-field fluorescence microscopy for high-speed imaging of conjunctival goblet cells

Goblet cells (GCs) in the conjunctiva are specialized epithelial cells producing mucins on the ocular surface. GCs play important roles in maintaining homeostasis of the ocular surface, and GC dysfunction is associated with various complications including dry eye diseases. Current GC examination methods, which are conjunctival impression cytology and confocal reflection microscopy, have limitations for routine examination. Fluorescence microscopy using moxifloxacin was recently introduced as a non-invasive and high-contrast imaging method, but further development is needed to be used for GC examination. Here we developed a non-invasive high-speed high-contrast GC imaging method, called moxifloxacin based axially swept wide-field fluorescence microscopy (MBAS-WFFM). This method acquired multiple fluorescence images with the axial sweeping of the focal plane to capture moxifloxacin labeled GCs on the tilted conjunctival surface in focus and generated all-in-focus images by combining the acquired images. The imaging field of view and imaging speed were increased to 1.6 mm × 1.6 mm and 30 fps. An image processing method was developed for the analysis of GC density. MBAS-WFFM was applied to alkali burn mouse models and detected GC damage and recovery via longitudinal imaging. MBAS-WFFM could assess the status of GCs rapidly and non-invasively. We anticipate MBAS-WFFM to be a starting point for non-invasive GC examination and the diagnosis of GC associated diseases. For example, MBAS-WFFM could be used to classify dry eye diseases into detail categories for effective treatment.

In vivo fluorescence imaging of conjunctival goblet cells

Conjunctival goblet cells (GCs) are specialized epithelial cells that secrete mucins onto the ocular surface to maintain the wet environment. Assessment of GCs is important because various ocular surface diseases are associated with their loss. Although there are GC assessment methods available, the current methods are either invasive or difficult to use. In this report, we developed a simple and non-invasive GC assessment method based on fluorescence imaging. Moxifloxacin ophthalmic solution was used to label GCs via topical administration, and then various fluorescence microscopies could image GCs in high contrasts. Fluorescence imaging of GCs in the mouse conjunctiva was confirmed by both confocal reflection microscopy and histology with Periodic acid-Schiff (PAS) labeling. Real-time in-vivo conjunctival GC imaging was demonstrated in a rat model by using both confocal fluorescence microscopy and simple wide-field fluorescence microscopy. Different GC densities were observed in the forniceal and bulbar conjunctivas of the rat eye. Moxifloxacin based fluorescence imaging provides high-contrast images of conjunctival GCs non-invasively and could be useful for the study or diagnosis of GC related ocular surface diseases.

[Dry eye disease as a complex dysregulation of the functional anatomy of the ocular surface. New concepts for understanding dry eye disease]

INTRODUCTION

Dry eye disease is a disorder of the tear film that results in epithelial damage and in a disruption of the normal homeostasis at the ocular surface. It is widespread and causes symptoms ranging from discomfort to blindness.

METHODS

A review of the existing literature was used to compare different past and recent concepts for the understanding of dry eye disease with a focus on aspects of the integrating functional anatomy of the ocular surface.

RESULTS

The understanding of the pathogenesis of dry eye disease has proceeded from the mere recognition of a lack of tears to a consideration of their quality and to the concept of wetting of the ocular surface. However, several other aspects as epithelial differentiation, innervation, hormonal status or immune protection contribute to the intact functional anatomy of the ocular surface. Recently it has been recognized that immunologically regulated mechanisms of inflammation represent a primary or secondary pathogenetic factor for dry eye disease. This is conceivably regulated by the cells of the physiological mucosal immune defence system, the eye-associated lymphoid tissue (EALT). Androgens represent an important trophic factor for the ocular surface and their deficiency predisposes to inflammation.

CONCLUSION

Dry eye disease represents a complex dysregulation of the functional anatomy of the ocular surface that can start from different alterations (e.g. insufficient secretion, defects in wetting or innervation). Immune-based inflammation is able to interconnect and negatively reinforce these different pathomechanisms, resulting in a vicious circle.

Ligneous conjunctivitis: biochemical evidence for hypofibrinolysis

Ligneous conjunctivitis (LC) is a rare disease of unknown etiology characterized by the growth of "woody" plaques on ocular and extraocular mucosa. These lesions are comprised of fibrin and both direct and indirect evidence implicates hypofibrinolysis as the primary defect in LC. To further elucidate the pathophysiology of LC we investigated the biochemical aspects of ligneous lesions with respect to the fibrinolytic system. Ligneous lesions were obtained from the right eye of a 15 year-old female patient with longstanding LC since age 2.5 year. Ligneous conjunctivitis in this patient has exhibited a chronic recurrent coarse and has involved multiple muscosal sites. Samples analyzed included an abundant mucoid thread from the conjunctival fornix and the ligneous plaque attached to the inferior tarsus. Samples were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to characterize protein profiles and by a variety of zymographic methods to visualize fibrinolytic enzymes. We found that mucoid and ligneous samples were distinct entities. Specifically, ligneous samples contained polypeptides with electrophoretic profiles characteristic of intact fibrin, and were replete in fibrin-bound tissue plasminogen activator (t-PA). Despite the presence of ample t-PA, ligneous samples were essentially devoid of fibrinolytic activity. In contrast, neither proteins nor t-PA could be detected in mucoid samples when fractionated by 7.5-15% SDS-PAGE or analyzed by fibrin zymography, respectively. Despite the absence of t-PA, mucoid samples were replete in fibrinolytic activity. This activity was plasminogen independent, heterogenous and inhibited by PMSF. Degradation profiles suggested that this activity represented in part alpha-chymotrypsin, consistent with this patient's treatment regime, as well as plasmin, elastase and an unidentified neutrophil-derived activity. Interestingly, ligneous samples contained both latent and activated forms of matrix metalloproteinase-9 (MMP-9), whereas mucoid samples contained predominantly activated forms of MMP-9. LC is characterized by defective fibrinolysis, despite the presence of ample t-PA and intact fibrin, and by an abundant mucoid thread which binds both endogenous and exogenous enzymes including serine protease(s) and collagenase(s). The implications of these results with respect to a role for exuberant mucus production or abnormal mucins in the development of a relative mucosal-site specific plasmin(ogen) deficiency is discussed.

Ocular mucins: Purification, metabolism and functions

Mucins are present at the ocular surface in both secreted and membrane-bound forms. Mucins are produced in partby the conjunctial goblet cells, and are complemented by non-globet secretions. This review focuses on secreted ocular mucins. They are present in the tear film, probably both in gel and soluble form, and play a role in lubrication and ocular defense. It is apparent that mucins are highly adapted to their functions. State of the art techniques for mucin purification and analysis are presented. Density gradient centrifugation, gel filtration, ion-exchange chromatography and agarose gel electrophoresis are discussed, together with methods of oliogosaccharide analysis. Reagents for the detection of mucin are considered in conjunction with these methods, which we have employed in the analysis of human and canine ocular mucins. The general structure of mucins is reviewed. The biosyntheas and glycosylation of ocular mucins are not yet fully understood, and are discussed in relation to currently established concepts. The impaact of disease on the nature and secretion of mucins is considered, as well as the physiological and pathological significance of mucus degradation.

Diurnal variations in tear glycoproteins: evidence for an epithelial origin for the major non-reducible > or = 450 kDa sialoglycoprotein(s)

PURPOSE

To characterize the nature and origin of changes in tear glycoproteins accompanying eye closure.

METHODS

Reflex (R) and overnight closed (C) eye tears collected by capillary tubes were centrifuged with the resulting R pellets (primarily desquamated epithelial cells) and C pellets (primarily PMN and some epithelial cells) extracted in acidic PBS. Extracts and supernatants were separated by size-exclusion HPLC and/or SDS-PAGE. Gels were stained or blotted and immune- or lectin-probed. An HPLC glycoprotein fraction of > or = 450 kDa isolated from all four sources was characterized before and after partial deglycosylation, using antibodies specific to known mucin and carbohydrate epitopes. Immunofluorescence microscopy was carried out on human conjunctiva, using as probe a MAb to salivary mucin specific for a sialyl Lea epitope, which was found to cross-react specifically with the major non-reducible high molecular weight sialoglycoproteins (SGs) in tears. These SGs were immunoprecipitated and blot-probed along with tissue extracts.

RESULTS

R fluid contained minor amounts of numerous glycoproteins, including probably several of inducible lacrimal secretory origin. Results confirmed sIgA as the principal source of the intense reducible glycoprotein bands common to C fluid. Smaller amounts of free secretory component and serum glycoproteins were also visualized. The HPLC fraction (> or = 450 kDa) consisted of four major non-reducible glycoproteins. In R fluid, this fraction (< 1% total protein) consisted primarily of two entities: a 450-500 kDa SG and a larger asialoglycoprotein. The SG accounts for as much as 85% of the total protein in the R pellet extract. C fluid was associated with a selective increase in SGs and a shift in distribution to two SGs > 500 kDa. All SGs exhibited a common antigenicity reacting specifically with the MAb for the sialyl Lea epitope. SGs indistinguishable in size and antigenicity were recovered in epithelial extracts. Immunofluorescence microscopy revealed that reactivity was localized to the epithelial plasma membrane, increasing in intensity from basal to apical cells. Although these SGs exhibited some properties in common with MUC1, immunological and other data suggest a unique SG.

CONCLUSIONS

Tear glycoproteins are derived from four principal sources. In R fluid, an inducible lacrimal secretion predominates. In C fluid, a constitutive sIgA secretion predominates, augmented by a serum exudate and SGs derived at least in part from the epithelium. In R fluid and pellet extracts, the SGs consist primarily of a 450-500 kDa species that is most probably derived from the plasma membrane. Larger antigenically related SGs are prevalent in C fluid.

Correlation of goblet cell density and mucosal epithelial membrane mucin expression with rose bengal staining in patients with ocular irritation

PURPOSE

This study was designed to compare goblet cell densities and mucosal epithelial membrane mucin (MEM) expression in impression cytology specimens obtained from control subjects and patients with one of the following clinically defined diseases: aqueous tear deficiency (ATD) associated with Sjögren syndrome, ATD not associated with Sjögren syndrome, inflammatory Meibomian gland disease associated with rosacea, and Meibomian gland atrophy. These data were correlated with ocular surface rose Bengal staining scores, Schirmer scores, and HLA-DR antigen staining of conjunctival epithelial cells.

METHODS

Goblet cell density and MEM expression were studied by impression imprints with immunohistochemical staining using an anti-mucosal epithelial membrane mucin antibody in the temporal and inferior bulbar and inferior tarsal conjunctiva of study subjects.

RESULTS

Goblet cell density adjacent to the temporal limbus was significantly reduced at 3 mm posterior to the temporal limbus in both aqueous tear deficiency groups compared with the other groups and in patients with Sjögren syndrome compared with all other groups. In the inferior tarsus, goblet cell density was significantly reduced in patients with non-Sjögren syndrome ATD as compared with all other groups, except those with inflammatory Meibomian gland disease. Mucosal epithelial membrane mucin expression in the bulbar and tarsal conjunctiva was absent in a greater percentage of patients with Sjögren syndrome compared with all other groups. Total ocular surface rose Bengal staining scores were significantly higher in patients with Sjögren syndrome as compared with all other groups and in patients with non-Sjögren syndrome ATD as compared with control groups. Rose Bengal staining scores and Schirmer I test results (without anesthesia) were inversely correlated with bulbar, but not tarsal, conjunctival goblet cell densities, and with the absence of bulbar conjunctival MEM expression.

CONCLUSIONS

These results suggest that reduced goblet cell density and mucosal epithelial cell mucin expression could explain increased rose Bengal staining in patients with aqueous tear deficiency. In addition, MEM may be regarded as a marker for normal differentiation of ocular surface epithelia, with its absence signifying the development of squamous metaplasia.

Transforming growth factor beta-1 and beta-2 in human tear fluid

PURPOSE

To evaluate human tear fluid for transforming growth factor beta isoforms 1 and 2 (TGF-beta1 and TGF-beta2).

METHODS

To accomplish this, human tears were evaluated for TGF-betas by quantitative antibody sandwich ELISA (sELISA), mink lung epithelial cell (MLEC) growth inhibition bioassay and western blotting. Various physical and chemical treatments were used to activate TGF-beta in these assays.

RESULTS

TGF-betas could not be detected in untreated or heated tears by sELISA; however, mean TGF-beta1 concentrations of 2.32 ng/ml were detected in acid-activated tears by sELISA. Furthermore, 10.54 ng/ml of TGF-beta1 and 2.98 ng/ml of TGF-beta2 were detected in tears treated with the mucolytic agent, acetylcysteine. Total TGF-beta bioactivity in human tears measured by the MLEC assay was found to be 13.04 ng/ml in untreated tears and 24.85 ng/ml in acid-activated tears. Approximately one-half TGF-beta in tear specimens was biologically active (mean = 52%, range 39-71%). Total tear TGF-beta bioactivity could be completely neutralized by recombinant human TGF-beta1 latency associated peptide (rh TGF-beta1 LAP). Mean neutralization of tear TF-beta bioactivity was 83% by TGF-beta1-specific antisera, and was 13% by TBF-beta2-specific antisera. Immunoreactive TBF-beta bands at approximately 12.5 and 95 kD were observed in immunoblots of reduced acidified tears. A high molecular weight (MW) TGF-beta band (>203 dD) was noted in untreated tears; however, this band disappeared following treatment with acetylcysteine.

CONCLUSIONS

The results of these studies indicate that TGF-beta1 and TGF-beta2 are present in human tear fluid, and TGF-beta1 is the predominant isoform. There appear to be factors in human tears capable of binding TGF-beta.

Characterization of a bovine synovial fluid lubricating factor. II. Comparison with purified ocular and salivary mucin

Boundary lubricating activity and biochemical characteristics of purified lubricating factor from bovine synovial fluid (PSLF) were compared to those of mucinous glycoprotein from human submandibular saliva and stimulated tears. Mammalian synovial fluid and saliva contain mucinous glycoproteins which reduce the coefficient of friction (mu) in a bearing of latex:glass which isolates boundary lubrication. In contrast, mucin secreted by the lacrimal gland did not lubricate. Cleveland plotting showed that these species are not identical.

The normal human tear glycoprotein profile detected with lectin probes

Tear samples were collected from 46 healthy volunteers evenly distributed according to sex and age (mean age 43.5 years). Samples were denatured in a Tris-HCl sample buffer containing 2-mercaptoethanol and SDS, and applied to a gradient SDS-polyacrylamide gel for electrophoresis. The proteinaceous material was transferred to nitrocellulose by a semi-dry blotting technique, and the glycoprotein content subsequently visualized by incubation with four lectins (WGA, PHA, PSA and SBA) and staining with avidin horseradish-peroxidase. Glycoprotein bands were generally found to be significantly less frequent in persons under the age of 30 years. Apart from this the technique gave a uniform picture of the glycoprotein profile, with only modest differences according to age and/or sex. The technique may therefore be suitable for the detection of differences in the glycoprotein composition indicative of disease.

Sialic acid in human tear fluid

A simple assay for the determination of sialic acid (N-acetylneuraminic acid) in human tear fluid was evaluated. Sialic acid, terminally bound on carbohydrate side-chains of glycoproteins, was released after treatment with neuraminidase and measured by an enzymatic colorimetric test. Tear fluid samples were collected from ten healthy adults, using glass capillaries and cellulose sponges. Sialic acid levels in tears collected with sponges (0.8-1.8 mmol l-1) did not differ significantly from those found in capillary tears (0.9-1.8 mmol l-1). Sialic acid, expressed as mmol g-1 protein, was significantly lower in tears collected with sponges (0.18-0.32 mmol g-1) than with capillaries (0.19-0.42 mmol g-1). Recovery of sialic acid and protein after incubation of cellulose sponges with tears was more than 99%. Sialic acid levels in human tears, which had been centrifuged to remove insoluble material, remained unchanged. Furthermore, tear sialic acid activity did not pass a filter with a molecular weight cut-off point of 10,000. Our data indicate that with the assay used in this report, sialic acid in tears is not due to secretory immunoglobulin A (sIgA), lactoferrin and lysozyme. The fact that the major tear proteins do not contribute to the sialic acid levels detected in tears suggests that other as yet unknown soluble glycoproteins are involved.

The ocular surface in keratoconjunctivitis sicca

The ocular surface is altered in kerato-conjunctivitis sicca, a disorder of aqueous tear production. Many of the factors leading to these surface changes are now more clearly understood and are discussed in this paper.

Studies on the isolation and composition of human ocular mucin

A method for the isolation and purification of human ocular mucin from the brief saline extract of human ocular mucus is reported. Initial purification of ocular mucin was achieved by sequential chromatography of the saline-soluble mucus extract from an individual donor's mucus pool on columns of Sephadex G-50 and Sepharose CL-4B. A portion of such mucin isolate was subjected to quantitative analysis of the O-seryl (threonyl)-N-acetylgalactosaminyl linkage, characteristic of mucins, by alkaline beta-elimination and tritiated borohydride reduction. Following Bio-Gel P-2 filtration, the mucin isolate whose cleaved oligosaccharides contained tritiated galactosaminitol greater than 0.5 microCi mg-1, a value that represents at least 64% of that observed for bovine and ovine submaxillary reference mucins, was considered to be mucin-rich. These isolates were subjected to further purification on Sephacryl S-500 and DEAE-Trisacryl M column chromatographies. The purified mucin had a minimum molecular weight of 120 kDa. It consisted of 25-30% protein and 54-55% carbohydrate. Its amino acid and carbohydrate compositions are characteristic of a mucin structure. The purity of the mucin was verified by SDS-gradient PAGE. Upon isoelectric focusing, polydispersity/microheterogeneity were exhibited in the pI range 5.0-6.6.

Eyelid secretions and the prevention and production of disease

Tears are necessary for the continued health of the ocular surface. Normal constituents include water, mucin, and lipids, electrolytes, non-electrolytes, and proteins. Lacrimal secretion is under cholinergic control and modulated by sympathetic adrenergic, peptidergic (VIP) and humoral influences; the meibomian glands are innervated, but the goblet cells are not. Retinoids are important for ocular health and prealbumin may be a carrier for vitamin A in the tears to supply corneal epithelium with its requirements. Changes in tear constituents may cause certain ocular disorders. In dry eyes increased osmolarity is thought to cause surface ocular damage but the presence of granulocytes and inflammatory mediators such as prostaglandins and super-oxide may contribute to inflammatory events in this and other external diseases.

Ocular surface complex carbohydrates are modified with aging

Picric acid-paraformaldehyde-glutaraldehyde (PA-P-G) was used to stabilize chemically ocular surface-associated mucus in mice of various ages. Transmission electron microscopy was then used to examine those specimens stained with cationic ferritin (CF), dialysed iron and Alcian Blue. Collectively, all of these stains are markers for anionic sulfate or carboxyl groups. With each of them, positive labeling of the ocular surface was observed for all ages examined, even when mucus cannot be morphologically demonstrated. Except for dialysed iron, staining was weak in the youngest animals and heaviest in young adult and aged mice. The ocular surface was negative for high iron diamine (HID) in pups and older mice through 1 year of age. Scant positive staining for HID was seen at the ocular surface in 14-month-old mice indicating that mucus became slightly sulfated with aging. Treatment of eyes with neuraminidase prior to fixation reduced the number of CF binding sites in all ages of mice examined, confirming that many of the carboxyl groups at the ocular surface are associated with sialic acid residues. Comparison of percentage reduction in CF labeling following neuraminidase treatment of the eyes of 5- and 10-postnatal day mice with all other ages of mice suggested that fewer removable carboxyl groups at the ocular surface are associated with sialic acid residues in pups. The ocular surface of all eyes also stained positively at the TEM level when a periodic acid-thiocarbohydrazide-silver protein (PA-T-SP) staining sequence was used. Collectively, these data are of significance with respect to further characterization of the ocular surface, particularly with regard to development-associated changes and their possible role in defence of the eye surface.

SDS-gradient polyacrylamide gel electrophoresis of individual ocular mucus samples from patients with normal and diseased conjunctiva

Individual mucus samples were collected from normal individuals and from patients with ocular cicatricial pemphigoid (CP), Stevens-Johnson syndrome (SJS), and various types of conjunctival inflammation (rosacea, meibomianitis, atopy, keratoconjunctivitis sicca, etc.). The mucus samples were dissolved in sample buffer containing 8M urea, 2% SDS and 5% 2-mercaptoethanol and were electrophoresed on gradient 2-16% polyacrylamide gels. Four glycoproteins with molecular weights greater than 200,000 daltons were consistently observed in both individuals with normal conjunctiva and patients with CP, SJS, and other diseases exhibiting conjunctival inflammation. The amounts of each glycoprotein appeared to vary from one individual to another; however, the presence or absence of specific glycoproteins could not be correlated with the different ocular diseases. The techniques described for mucus analysis offer advantages over previously published techniques since improved resolution of the mucous glycoproteins can be achieved by electrophoresis on 2-16% gradient gels, and individual samples can be analyzed. Our results suggest that substantial amounts of ocular mucous glycoprotein are present in the eyes of patients with CP and SJS, diseases which have been previously described as mucin-deficient dry eye syndromes.

Deposits on soft contact lenses. Electrophoresis and scanning electron microscopic examinations

Deposits on soft contact lenses were studied by several methods, microscopic examination, scanning electron microscopy, electron microprobe and electrophoresis on polyacrylamide gels of removed proteins. The first two approaches permitted classification of deposits into globular deposits, "Mulberry-like growths", opaque deposits, protein films and red spots. The electron microprobe indicated specific compositions of each. The electrophoretic technique demonstrated the presence of lysozyme in all the deposit types, with other unidentified proteins or degradation peptides. Whatever the deposit type, heat disinfection is not advisable since proteins are always present. Combination of chelating agents and oxidizing products are logically to be preferred for cleaning lenses.

Detection of mucus glycoconjugates in human conjunctiva by using the lectin colloidal gold technique in TEM. I. A quantitative study in normal subjects

We applied a specific cytochemical reaction to characterize the glycoconjugates produced by goblet and non-goblet epithelial cells of normal human conjunctiva. For this purpose we utilized the lectins, proteins of vegetal origin, which are extremely sensitive in binding glycosidic residues. In particular, we used WGA, PNA, SBA and ConA conjugated with colloidal gold as ultrastructural marker for Transmission Electron Microscopy. This technique allowed us also to perform a quantitative analysis, by counting colloidal gold particles present on mucus granules. In this way we analyzed the content both of goblet and non-goblet epithelial cells. In the former, WGA, PNA, SBA and ConA receptors, here reported in decreasing density, were present. In the latter WGA was always positive, SBA and PNA sometimes were negative, ConA was always negative. We speculate the different contribution to mucus production by these two sources may be important in evaluating tear film stability alterations occurring in those diseases in which non-goblet epithelial cell vesicles increase.

Origin and composition of lipid deposits on soft contact lenses

"Jelly bump" deposits, common to high-water-content hydrogel extended-wear contact lenses, were shown to be composed primarily of lipids, with calcium an optional minor component. Extraction, separation, and analysis of deposited versus nondeposited regions of the same lenses reveals that lipids were restricted to the deposited regions of the lens, with a composition of long and intermediate chain cholesterol esters (possibly waxy esters) and triglycerides. This composition is independent of deposit size or individual depositor. Except for an elevated triglyceride level, the composition mirrors that of the tear lipid layer. Analysis of tear films of heavy and nondepositors, combined with clinical evidence, reveals that many depositors have a relatively decreased tear flow with some exhibiting an elevated tear-lipid fraction. A mechanism of deposition is proposed to require the local depletion of the aqueous tear layer stranding lipid on the lens surface, thereby creating a hydrophobic region suitable for further deposition. Deposition does not mechanistically involve tear film proteins, calcium, or microorganisms although they can, at times, be associated with the lipid deposit.

Immunocytochemical localization of immunoglobulins at the corneal surface of the mouse

Immunoglobulins A, G1, G2a and M were localized at the corneal surface of adult Swiss-Webster mice using Sternberger's peroxidase anti-peroxidase (PAP) technique. Immunoglobulins G2b, G3 and E and lysozyme were not present at the corneal surface of the mouse. Light microscopy of whole mouse eyes incubated for the detection of immunoglobulin A (IgA) demonstrated a population of positively-stained corneal surface cells. IgG1, IgG2a and IgM could not be similarly detected at the light microscopic level. At the transmission electron microscopic level, a greater amount of staining for IgA was localized over the mature corneal surface cells. A lesser amount of IgA staining occurred over the young and mature corneal surface cells. In contrast to this, IgG1, IgG2a and IgM were randomly distributed over the corneal surface and were not preferentially localized over young or mature surface cells. The staining for IgG1, IgG2a and IgM was less than the staining for IgA at the corneal surface. IgA was also localized at the corneal surface using an indirect immunoferritin technique. These studies suggest that immunoglobulins A, G and M are intimately associated with the glycocalyx and microvilli of the corneal surface cells. At present it is not known whether these immunoglobulins are bound directly to the surface cell apical plasma membrane or indirectly via mucus glycoproteins at the ocular surface.

Physiological and pathobiological significance of ocular glycoproteins. I. Studies using fluorescein labelled glycine max

Cell surface carbohydrates play an important role in several biological, immunological, and neoplastic phenomena including development, growth regulation, cellular locomotion, receptor activation, and tumour metastasis. Fluorescein labelled lectins which bind to specific carbohydrate residues in glycoproteins and glycolipids are being increasingly used as chemical probes to study cell components. Several different preparations of ocular tissues from human, rabbit, and rat were examined for the distribution of N-acetyl-D-galactosamine (D-gal NAc) by means of fluorescein-labelled lectin from soybean (glycine max). A very strong fluorescence was observed in the corneal epithelium; Descemet's membrane and corneal endothelium were also strongly fluorescent. The conjunctival epithelium similarly showed a strong reaction, as did the goblet cells. The iris epithelium and the dilator pupillae were only weakly fluorescent, but the ciliary body showed strong fluorescence, as did the blood vessels. As compared with lens fibres the lens epithelium was strongly fluorescent. The outer retina, that is, the photoreceptors, the pigment epithelium, and Bruch's membrane, showed a very strong reactivity. The optic nerve showed moderate fluorescence, but reaction with extraocular muscles was variable. The skin of the upper and lower eyelids, hair follicles, and blood vessels showed strong lectin binding. Sections of retinoblastoma and malignant melanoma showed no reaction. The physiological and pathological significance of these findings is discussed.

Adsorption of tear proteins on soft contact lenses

To better understand protein deposit formation on contact lenses, a study of adsorption of lacrymal proteins was undertaken. Purified tear proteins were radiolabelled with 125I. The time course of adsorption of single protein solutions at various pHs or in mixture systems at pH 7.5 was determined. The maximum amount of lysozyme and albumin adsorbed in the presence of diluted tears was obtained. The influence of an early adsorbed layer on further adsorption was investigated.

Deposits on hydrophilic 'bandage' lenses. A scanning electronmicroscopic and x-ray microanalytic study

Scanning electronmicroscopy of 34 continuously worn Sauflon PW 'bandage' lenses showed an initial deposition of cellular debris, followed by an increasing, general, non-penetrating, organic coating, particularly on the anterior lens surface. No microorganisms were found. X-ray microanalysis of the 34 Sauflon PW lenses as well as 11 daily worn Hydroflex m lenses showed that elements may be added to or 'washed out' from the lenses during storage before preparation for microscopy. The elements obtained were constituents of both normal tear fluid and lens storage solutions. Only sulphur appeared firmly bound in the deposits, probably as sulphur-containing macromolecules of ocular mucus. Calcium was only detected in a few cases.

Complex carbohydrates at the ocular surface of the mouse: an ultrastructural and cytochemical analysis

Scanning electron microscopy (SEM) of mouse cornea and conjunctiva fixed with picric acid-paraformaldehyde-glutaraldehyde (PA-P-G) mixture revealed a thin layer of amorphous material covering the microvilli of the corneal surface cells. At the transmission electron microscopic (TEM) level, this layer of material stained positively with dialyzed iron, alcian blue and cationized ferritin, all of which are markers for anionic sulfate or carboxyl groups. The corneal surface was negative for high iron diamine, which specifically stains sulfate groups. These results indicate that the murine ocular surface is rich in carboxyl groups. Treatment with neuraminidase prior to fixation significantly reduced (P less than 0.005) cationic ferritin binding, suggesting that most of the carboxyl groups at the ocular surface are associated with sialic acid residues. The corneal surface also stained positively at the TEM level when a periodic acid-thiocarbohydrazide-silver protein sequence (PA-T-SP) was applied. This result indicated the presence of periodic acid-Schiff (PAS)-positive glycoprotein and glycolipid at the ocular surface.

Application of lectins for detection of goblet cell carbohydrates of the human conjunctiva

Paraffin-embedded and frozen biopsies from the human conjunctival epithelium were examined by fluorescence microscopy after labeling with eight fluorescein-conjugated lectins: wheat germ agglutinin; soybean agglutinin; peanut agglutinin; Ricinus communis agglutinin-1; Limulus polyphemus agglutinin; Ulex europaeus agglutinin-1; Dolichos biflorus agglutinin; concanavalin A. The lectins were used as specific molecular probes to detect carbohydrate composition of glycoproteins secreted from the conjunctival goblet cells. The labeling pattern of goblet cells and conjunctival epithelial surfaces with various lectins suggested that N-acetyl-glucosamine, galactose, N-acetyl-galactosamine and sialic acid are contained in goblet cells and contribute to the formation of tear mucus glycoprotein. Fucose and mannose, which are present in the tear mucus, were not detectable in goblet cells.

O-glycosidic linkage in glycoprotein isolates from human ocular mucus

Alkaline beta-elimination and sodium borohydride reduction were used to study the O-glycosidic linkage of N-acetylgalactosamine to seryl and threonyl residues in the high molecular weight crude glycoprotein fractions isolated from human ocular mucus. Pure mucins, BSM and OSM, were used as models. Data are presented for the existence of such O-glycosidic linkages. It was estimated from sodium borohydride reaction that at least 22% of the total peptide bonded hydroxyamino acid residues are linked O-glycosidically. These findings, as a continuation of our previous work on the isolation and chemical characterization of human ocular mucus, provided additional evidence of the mucin nature of the glycoprotein isolates.

Fractionation and partial characterization of macromolecular components from human ocular mucus

Crude human ocular mucus was extracted with 0.154 M-NaCl to separate soluble protein components from mucus. Small amounts of lipoglycoprotein of high molecular weight, as well as twelve plasma proteins, were detected in the soluble extract by gel filtration and immunodiffusion studies. After the NaCl extraction, the remaining mucus residue was further extracted with 6 M-urea-0.2 M-Tris-phosphoric acid buffer. From this portion of soluble extract, a relatively larger amount of lipoglycoprotein of high molecular weight, as well as a lower molecular weight fraction containing eight detectable plasma proteins, were both isolated by gel filtration. The glycoprotein moieties of the lipoglycoproteins of high molecular weight had similar chemical composition. Both contained approximately 40-43% protein and 57-60% carbohydrate, giving a carbohydrate--protein ratio of 1.30 to 1.48. Fucose, galactose, N-acetylhexosamine and N-acetylneuraminic acid comprised about 423 516 residues per 1000 amino acid residues, while serine and threonine constituted about 285 299. All analyses indicated mucin-like character in the lipoglycoproteins of high molecular weight. Plasma proteins constituted approximately three-fifths of the macromolecular components in ocular mucus. These proteins also appeared to be in complexes with lipids, but to a much lesser extent than the high molecular weight fractions. The relevance of present findings to the structure and composition of precorneal tear film is discussed.

Specialized cell types and their regional distribution in the conjunctival epithelium of the cynomolgus monkey

In the superficial layer of the conjunctival epithelium of cynomolgus monkeys, five different cell types were found. The cell types were distinguished by ultrastructural criteria (e.g., cell organelles and cytoplasma) and are defined as follows: type I are the goblet cells; type II is characterized by the content of small electron-dense granules type III is particularly rich in Golgi material, type IV contains a specifically large amount of ER; type V shows an exceptionally large number of mitochondria. The quantitative evaluation of these cell types in 15 areas of the conjunctiva of 3 animals revealed a characteristic pattern of regional distribution, which may reflect the otherwise unknown functional significance of most of these cell types.

Clinical biochemistry of tears

The composition of tear fluid as it exists in the conjunctival fornix and in the precorneal tear film is of a complicated nature. The precorneal tear film is a physically inhomogenous system, produced by the lacrimal glands, the accessory lacrimal glands and the goblet cells of the conjunctiva and the Meibomian glands of the lid margin. The method of collection is crucial for the quantity and concentration of a great number of different compounds that have been demonstrated in tears. A survey is given of the literature concerning tears as they are composed of proteins, enzymes, lipids, metabolites, electrolytes and drugs, the latter secreted during therapy. Clinical applications of the determination of several compounds for diagnosis or for monitoring drug therapy are summarized.

Human conjunctival surface mucins: a quantitative study of normal and diseased (KCS) tissue

The architecture and distribution of surface mucins were studied qualitatively and quantitatively by transmission electron microscopy in ruthenium red stained biopsies of the human conjunctiva. Six control specimens were compared with three from early keratoconjunctivitis sicca (KCS) and with three specimens from severe KCS cases. The area of the ruthenium red/OsO4/mucin reaction product on the conjunctival epithelial surface was measured by image analysis and the values were expressed in micron2 per micron length of epithelium. The total area of surface mucins was differentiated from the narrow zone of mucins in close contact with the microplicae. The value for total mucins in two cases of early KCS was higher (0.4 micron2/micron) than the control range (0.1-0.3 micron2/micron) due to the presence of large clumps of mucins on the surface. The values for microplical mucins in early and severe KCS were within the control range, but were an overestimate owing to the presence of abnormal structures, e.g. vesicles, and abnormal clumps on the surface. This morphometric technique has limitations, but with appropriate material it might be a useful tool for the identification of conjunctival surface mucins.

The pathology of soft contact lens spoilage

Our study of a random series of more than 300 spoiled soft contact lenses reveals that virtually all lenses currently in use for daily or extended wear are subject to deterioration due to extraneous deposits, physical and chemical changes in the lens material, and microbial invasion. Common causes include ocular secretions, finger dirt and cosmetics, disinfecting and cleansing techniques, environmental factors, manufacturing defects and polymer impurities, mechanical stress and breakage, as well as aging and decay of the lens material. Mucoprotein-lipid deposits, with or without calcium, and calcareous deposits constitute the major forms of lens spoilage. Removal of encrusted deposits leaves surface irregularities and matrix defects which facilitate secondary spoilage including microbial invasion, and such lenses should be discarded. As virtually no soft lens material currently in use is "safe" for extended wear, the practitioner must carefully evaluated and follow his patients to identify those at risk of lens failure and spoilage complications. To eliminate spoilage, new lens materials and improved manufacturing techniques are needed. In the interim, for many patients, an inexpensive disposable soft lens which can be easily replaced, perhaps weekly or bi-weekly, may be the answer.