On the nature and the role of the subsurface vesicles in the outer epithelial cells of the conjunctiva

Ultrastructural Study of the Conjunctiva in Patients with Keratoconjunctivitis Sicca not Associated with Systemic Disorders

Purpose

The aim of this work was to evaluate ultrastructural alterations of the conjunctiva during the clinical course of keratoconjunctivitis sicca (KCS), and to detect its earliest and most characteristic morphological changes.

Methods

The conjunctiva was studied in biopsies from 75 patients and 10 controls. Patients were classified according to the results of the Schirmer I test, break-up time, rose Bengal staining, osmolarity and impression cytology.

Results

The conjunctiva in these KCS patients showed progressive hyperplasia, hypertrophy and cellular flattening, with diminution of goblet cell density and microvilli. In the severe cases, the epithelial cells lost their organelles, and fibrous material increased. From the early phases of KCS, clear nuclear alterations (indentation, binucleation) were found, but pyknotic nuclei or anucleated cells were only observed in the most severe cases. From the earliest stages to the most severe cases of KCS, decreases in cell membrane interdigitations were observed parallel to increases in the number and size of desmosomes. There were also increases in the number of inflammatory cells. Alterations in blood vessels were only observed in the most severe cases.

Conclusions

Morphological studies alone were able even in the earliest phases of KCS, to detect the squamous metaplasia that progresses from the surface of the epithelium to the connective tissue. This degenerative or adaptative cellular process was characterized mainly by marked proliferation of the cytoskeleton and a general loss of organelles, mitochondria being the least affected.

Mucosal microvilli in dry eye patients with chronic GVHD

The ocular surface is a frequent target tissue of mucosal chronic GVHD (cGVHD). We investigated the histopathological features of the conjunctival microvilli in patients with cGVHD. Conjunctival tissue specimens from patients with cGVHD or Sjögren's syndrome (SS) or from healthy individuals were examined by light microscopy and EM, impression cytology, and immunohistochemistry. The cGVHD conjunctivae showed significantly more metaplasia and fewer goblet cells than the SS and normal conjunctivae. Abundant CD8(+) T cells infiltrated the basal epithelia in the cGVHD conjunctiva. The microvilli per standard epithelial unit and the secretory vesicles were counted by analyzing electron micrographs. The mean number of mucosal microvilli was significantly lower in the cGVHD than that in the SS or normal specimens, and the microvilli were significantly shorter, with a smaller height-width ratio. The mean number of secretory vesicles was also significantly lower, and the membrane-spanning mucin thinner, in the cGVHD compared with the SS and normal specimens. Thus, the conjunctival mucosal microvilli of cGVHD patients were significantly different in number and morphology from those of SS and normal subjects. These may be important factors affecting the stability of the tear-film layer and its contribution to cGVHD-related dry eye.

Investigations on the conjunctival goblet cells and on the characteristics of glands associated with the eye in the guinea pig

OBJECTIVE

To investigate the distribution and density of conjunctival goblet cells (GC) and to study the anatomy and microscopic characteristics of glands associated with the eye in the guinea pig.

PROCEDURES

Twenty-five guinea pigs were used. Meibomian gland openings were counted using biomicroscopy. Conjunctiva, eyelids and glands were embedded in glycol methacrylate and paraffin. Sections were stained with hematoxylin and eosin (H&E), periodic acid Schiff's reaction (PAS) and Alcian blue (AB).

RESULTS

Highest GC densities were found in the bulbar and palpebral region of the nasal conjunctiva (GC index: 13.7-16.4%). Lowest GC densities (GC index: 0.0-1.0%) were found in 3/4 limbal regions (nasal and temporal upper eyelid, temporal lower eyelid). Guinea pigs have 27.1±3.0 (mean±SD) meibomian gland openings in the upper lid and 25.7±2.3 in the lower lid. Difference between upper and lower lid was significant (P=0.037). Two subconjunctival sebaceous glands occur temporal to each eye. The Harderian gland is very large. In the lacrimal gland three different cell types were distinguished both according to the cell structure and histochemical staining.

CONCLUSIONS

Goblet cell densities are lower in guinea pigs than in dogs and horses. Positive staining with PAS and AB could be an indication that mucins are produced in the lacrimal gland. If so, they may contribute to the mucin layer of the tear film. Both the extraordinarily large Harderian gland and the subconjunctival sebaceous glands produce lipids and may contribute to the lipid layer of the tear film.

Control of mucin production by ocular surface epithelial cells

Multiple species of mucins are synthesized and secreted by corneal and conjunctival epithelial cells. These mucins are vital components of the tear film protecting the ocular surface from the external environment by providing a physical and chemical barrier. The release of mucins must be tightly regulated as both mucin overproduction and underproduction cause ocular surface disorders. Mucin production can be regulated by controlling mucin synthesis, mucin release, or proliferation of the cells that produce the mucin. This review will focus on the evidence demonstrating the control of the mechanisms responsible for production of mucins, their secretion, and corneal and conjunctival epithelia cell proliferation. By understanding these mechanisms under normal conditions, treatments can be designed for diseases of the mucous production of the ocular surface.

The eicosanoid, 15-(S)-HETE, stimulates secretion of mucin-like glycoprotein by the corneal epithelium

PURPOSE

The eicosanoid, 15-(S)-hydroxyeicosa-5Z, 8Z-11Z, 13E-tetraenoic acid (15-(S)-HETE), is known to stimulate production of mucin glycoprotein by airway epithelium. This study investigated the effect of 15-(S)-HETE on the mucin glycoprotein secretion by the corneal epithelium.

METHODS

To determine the effect of dose, corneas of anesthetized New Zealand White rabbits were treated with 50, 500, or 5,000 nM 15-(S)-HETE in artificial tears for 120 minutes. To determine the time to onset of the response, corneas were treated with 500 or 1,000 nM 15-(S)-HETE in balanced salt solution for periods ranging from 5 to 120 minutes. Corneas were fixed for electron microscopy in fixative containing 0.5% cetylpyridinium chloride (CPC) to stabilize the layer of mucin-like glycoprotein on the corneal surface. The mucin layer thickness was measured by image analysis of electron micrographs.

RESULTS

The layer of CPC-fixed mucin-like glycoprotein on the surface of control corneas was 0.46 +/- 0.04 microm thick. After treatment with 15-(S)-HETE, the thickness of the mucin layer increased to 0.64 +/- 0.1 microm at 50 or 5,000 nM HETE and as much as 1.02 +/- 0.2 microm in response to 500 nM HETE. Mucin thickness reached a statistical maximum of 0.59 +/- 0.1 microm after only 5 minutes of exposure to 500 or 1,000 nM HETE.

CONCLUSIONS

Exposure of the cornea to 15-(S)-HETE causes a rapid-onset increase in the thickness of a layer of mucin-like glycoprotein on the surface of the corneal epithelium. This supports previous reports that corneal epithelial cells produce mucin and suggests that treatment with topical 15-(S)-HETE may be effective in treating ocular surface mucin deficiency in dry eye syndrome.

Flow cytometric analysis of conjunctival epithelium in ocular rosacea and keratoconjunctivitis sicca

PURPOSE

To investigate by flow cytometry and impression cytology (IC) specimens the inflammatory status of the conjunctival epithelium and goblet cell density in two series of patients with rosacea and dry eye syndrome compared with a population of healthy subjects.

DESIGN

Nonrandomized, prospective, comparative case series.

PARTICIPANTS

Twenty-six eyes of 13 patients with rosacea, 26 eyes of 13 patients with dry eye syndrome, and 24 eyes of 12 control subjects were included in this study.

METHODS

IC specimens were collected after clinical examination of the ocular surface and analyzed by flow cytometry, using antibodies directed to human lymphocyte antigen-DR (HLA-DR), intercellular adhesion molecule-1 (ICAM-1) (CD 54), and the peptidic core of the conjunctival mucin (M1/MUC5AC). The percentage of positive cells was calculated and levels of fluorescence expression quantified and compared with those obtained in a series of 12 healthy subjects.

MAIN OUTCOME MEASURES

Tear break-up time (TBUT), Schirmer test, fluorescein and lissamin green stainings, and IC were realized in this study.

RESULTS

A significant increase of HLA-DR and ICAM-1 expressions by epithelial cells was consistently found in the two pathologic groups compared with levels calculated in normal eyes. The two markers were well correlated with each other and inversely with TBUT and Schirmer test. The percentage of goblet cells was significantly decreased in rosacea patients and in dry eye patients compared with the normal group with a significant negative correlation with both HLA DR and ICAM-1 markers.

CONCLUSIONS

Ocular rosacea and keratoconjunctivitis sicca were associated with severe ocular surface changes, such as an overexpression of inflammatory markers and a significant decrease in the number of goblet cells.

The effects of experimental tear film removal on corneal surface regularity and barrier function

PURPOSE

To evaluate corneal surface regularity and asymmetry, corneal thickness, barrier function, and contrast sensitivity after experimental removal of the precorneal tear layer.

DESIGN

Prospective, clinic-based, nonrandomized (self-controlled) comparative trial.

PARTICIPANTS

Six eyes of six healthy volunteers (three males, three females; age range, 29-40 years).

METHODS

A precorneal tear lesion was created by pressing a sterile Biopore (Millipore, Bedford, MA) Teflon membrane against the central cornea. Corneal topography with both the Topographic Modeling System (TMS-1; Computed Anatomy, Tomey Technology, Cambridge, MA) and the Orbscan (Orbscan Inc., Salt Lake City, UT) were performed before the lesion was created and 30 seconds, 1 hour, and 4 hours after the lesion was created. Surface regularity and surface asymmetry indices were evaluated by the TMS-1 topography system. Maximum and minimum keratometric readings, corneal fluorescein staining, contrast sensitivity, and corneal thickness were evaluated before and after the tear lesion. Cytologic membranes were stained for MUC4 mucin using an indirect immunofluorescent staining technique. Confocal microscopy was performed to evaluate the integrity of the corneal epithelium in two eyes. Analysis of variance with polynomial contrasts was used to examine time trends of the outcome variables.

MAIN OUTCOME MEASURES

The change in corneal surface regularity and asymmetry indices, corneal thickness, permeability to fluorescein dye, and contrast sensitivity before and after the lesion was made were compared.

RESULTS

The corneal epithelium in the area of the lesion showed intense fluorescein staining 30 seconds postlesion but appeared normal by 4 hours. Confluent, homogeneous staining for MUC4 mucin was observed on the membranes used to create the lesion in all cases. The surface regularity index measured with the TMS-1 increased after the lesion was created and decreased toward normal by 4 hours (P = 0.017). Corneal thickness measured by the Orbscan instrument significantly increased in the central (P = 0.001), superior (P = 0.006), inferotemporal (P < 0.001) and superotemporal (P = 0.001) cornea immediately following the lesion and returned to normal by 4 hours. The lesion caused a decrease in visual acuity at 6.30%, 4% and 2.5% contrast sensitivities 1 hour postlesion and these measurements returned to prelesion values by 4 hours (P = 0.085, P = 0.005, P = 0.043).

CONCLUSIONS

The precorneal tear layer serves as a permeability barrier and is essential for maintaining a smooth quality optical surface.

Secreted human conjunctival mucus contains MUC5AC glycoforms

This study addresses the extent of variation in secreted end-product mucins in human conjunctival mucus. The aim was to determine whether the variety of mucin species found was encompassed by the mucin genes which have been cloned to date. Extraction into guanidine hydrochloride and separation of mucin constituents, by a combination of cesium chloride density gradient centrifugation, size separation on Sepharose CL-2B, MonoQ ion exchange chromatography and agarose gel electrophoresis, demonstrates a complex mixture of mucins. Sample size limitations precluded compositional amino acid analysis. MUC 5AC and MUC1, 2, and 4 are all detected in the buoyant density range 1.3-1.5 g/ml by antibody binding. The mucins vary in size from >40 x 10(6)to <97 x 10(3)Da. A wide range of molecular size was confirmed using rate zonal centrifugation. The presence of smaller species contrasts with other mucous secretions similarly studied. In each size range are low, medium, and high charge mucins. Sialylation predominates in the medium charge and sulfate in the high charge. Only MUC5AC cross-reactivity is maintained throughout the analysis. It is detected in large and medium sized mucins but accounts for only the least mobile mucins within copurified species of similar density, size, and charge resolved using agarose electrophoresis. MUC5AC cross-reactivity is also detected in both medium and high charge species, indicating the presence of glycoforms.

Biochemical analysis of ocular surface mucin abnormalities in dry eye: the canine model

This study examines the canine model of keratoconjunctivitis sicca (KCS, 'dry eye') in order to establish the biochemical basis of altered ocular mucin secretion in this condition. It follows a previous examination of ocular mucins in the normal dog. Mucus was collected by suction from the ocular surface of dogs with KCS, and dispersed in guanidine hydrochloride containing a cocktail of protease inhibitors. Caesium chloride density gradient centrifugation was used to separate floating 'rafts' of cell membranes from gradients containing secreted mucins. Gradient fractions were collected into pools on the basis of differential staining by Periodic Acid Schiff, Wheat Germ Agglutinin, and antibodies to MUC5AC peptide. High molecular weight glycoproteins were purified from the pooled material by gel filtration chromatography. Membrane-associated glycoproteins were also derived from the membrane rafts using octyl glucoside extraction and/or reduction and alkylation. Secreted mucins and membrane extracts from KCS samples were compared to equivalent material obtained from normal eyes. Density gradient staining profiles for normal and KCS mucus were similar over the buoyant density range typical for secreted mucins, enabling the collection of identical pools of gradient fractions for direct comparison. The following differences were observed in KCS secreted mucins compared to normal samples: an increase in the proportion of mucin with low buoyant density; a decrease in mannose content detected with Concanavalin A lectin; an increase in N-acetylglucosamine structures detected with Lycopersicon esculentum lectin; increased migration and lack of evidence for distinct subunit structure on agarose gels. In membrane extracts, the main difference was the presence of T antigen (Gal beta 1-3GalNAc) in KCS. These results demonstrate alterations in the subunit linkage of mucins in KCS, and suggest that glycosylation, core protein expression and/or post-synthetic modification of ocular surface mucins may also be changed.

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.

Cellular origin of mucins of the ocular surface tear film

In summary, we have demonstrated that the ocular surface epithelia express at least three mucin genes. We suggest that the gel-forming mucin MUC5AC is a major mucin forming the mucus gel of the tear film. We further suggest that MUC1 facilitates the spread of the MUC5-containing mucus on the ocular surface and, along with the mucus gel, prevents cell and debris adhesion to the ocular surface. The function of MUC4 at the ocular surface remains to be elucidated.

Mucin-like glycoprotein secretion is mediated by cyclic-AMP and protein kinase C signal transduction pathways in rat corneal epithelium

Ocular surface mucin is secreted from both goblet cells in the conjunctival epithelium and corneal epithelial cells. To clarify its mechanism of secretion in corneal epithelial cells, a rat cornea organ culture system was used to evaluate the second messenger roles of cyclic-AMP (cAMP), cyclic-GMP (cGMP) and protein kinase C (PKC) in modulating mucin-like glycoprotein secretion. Rat cornea sections (3 mm diameter) were cultured in TC-199 medium, and radiolabeled with sodium sulfate for 18 hr. After washing, the corneas were treated with various second messenger modulating agents for 30 min. The culture media were reacted with Dolichos biflorus (DBA)-lectin, and mucin-like glycoprotein was isolated. Then the radioactivity of DBA-binding mucin-like glycoprotein was isolated. Then the radioactivity of DBA-binding mucin-like glycoprotein was measured. There was a time-dependent increase in mucin-like glycoprotein was measured. There was a time-dependent increase in mucin-like glycoprotein secretion, whereas after corneal epithelial debridement the secretion was markedly inhibited by 81%. Mucin-like glycoprotein secretion was stimulated in a dose-dependent manner following elevation of cAMP levels by exposure to either forskolin, dibutyryl cAMP or 3-isobutyl-1-methylxanthine. Concomitant exposure to the cAMP dependent protein kinase inhibitor, KT5720 completely inhibited their stimulatory effects. Neither exposure to dibutyryl cGMP nor nitroprusside affected mucin-like glycoprotein secretion. Stimulation by PKC, phorbol 12, 13-dibutyrate (PDBu) also increased mucin-like glycoprotein secretion in a dose-dependent fashion. The PKC inhibitor, calphostin C completely inhibited the stimulation by PDBu of mucine-like glycoprotein secretion. These results demonstrate that corneal epithelial cells secrete mucin-like glycoprotein, which is mediated by cAMP and PKC signal transduction pathways.

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.

Gefarnate stimulates secretion of mucin-like glycoproteins by corneal epithelium in vitro and protects corneal epithelium from desiccation in vivo

The effect of drugs for gastritis and gastric ulcer (ecabet sodium, gefarnate, teprenone, and troxipide) on the secretion of mucin-like glycoproteins from rat cornea were investigated in vitro and on a short-term, rabbit dry eye model in vivo. For the studies in vitro, cultured rat cornea sections (3 mm diameter) were incubated with radiolabeled sodium sulfate, rinsed, and then incubated for 30 min in the presence of one of the drugs. The culture media were reacted with Dolichos biflorus agglutinate (DBA)-lectin, and the radioactivity of DBA-bound mucin-like glycoproteins was measured. A cytotoxicity assay confirmed that mucin-like glycoproteins had not leaked from damaged cells. For studies in vivo, eye drop vehicle or drops containing gefarnate were instilled in the eyes of nine anesthetized rabbits, and then the eyes were kept open with specula for two hours. These rabbits and two control rabbits not subjected to ocular drying were killed, and their eyes were enucleated and stained with methylene blue. Corneal epithelial damage from desiccation was evaluated based on the extent of methylene blue staining. Among the four kinds of drugs for gastritis and gastric ulcers, only gefarnate significantly increased the mucin-like glycoprotein secretion from cultured rat corneas in vitro; this stimulatory effect of gefarnate was dose-dependent. In vivo, the instillation of gefarnate reduced corneal epithelial damage from desiccation in a dose-dependent fashion. These results suggest that gefarnate reduces desiccation of corneal epithelium, perhaps by stimulating secretion of mucin-like glycoproteins from corneal epithelium.

Stratified squamous epithelia produce mucin-like glycoproteins

The stratified squamous epithelia of the ocular surface, larynx, and vagina are mucus-coated epithelia, apices of which are subject to abrasive pressure from epithelia-epithelia interactions from eyelid, vocal cords, or vaginal folds, respectively. Mucus coats on these epithelia have generally been considered to be derived from the specialized mucin-producing cells embedded either in the epithelia or in adjacent tissues. Here we report the isolation, partial characterization, and cellular localization of a mucin-like glycoprotein produced by these stratified epithelia. In all three epithelia, the mucin-like molecule is present on cytoplasmic vesicles in subapical cells. As cells differentiate to their apical-most position adjacent to their mucus coat, the mucin-like molecule moves to the cell membrane where it is particularly prominent on microplicae folds. Lectin affinity chromatography was used to isolate the molecule from rat vaginal and corneal epithelium. Isolated material was approximately 60% carbohydrate and 40% protein. The major monosaccharide was N-acetylgalactosamine with lesser amounts of N-acetylglucosamine, galactose, mannose, xylose and fucose. Amino acid analysis demonstrated the predominant amino acids to be glycine, serine, threonine and proline. These data plus PAS and Alcian blue binding to the isolate indicate a mucin-like glycoprotein.

Energetics of corneal epithelial cell-ocular mucus-tear film interactions: some surface-chemical pathways of corneal defense

The role of ocular mucous gel in the corneal epithelial hydration, lubrication, cleansing, wettability and defense against pathogens, is investigated based on a modified DLVO theory that accounts for the apolar, as well as polar, "acid-base" surface interactions. A strong polar repulsion keeps mucus in the form of highly hydrated "sloppy" gel, which does not adhere to the normal epithelium. Due to its strong electron donor type monopolarity, the mucus gel can form an effective barrier against contamination of the underlying epithelium by both the apolar (e.g., tear film lipids, cell debris) and the polar (e.g., hydrophilic bacteria) entities. In the absence of mucus, epithelial contamination becomes energetically favorable, which can also compromise its wettability by tears. Finally, a loss of polar surface properties can lead to adhesion of mucus to the cornea.

Qualitative tear film disease

Abnormalities of the lipid and mucin components of the preocular tear film may result from diseases of the eyelid margins and conjunctiva. Chronic keratoconjunctivitis with epithelial edema and superficial corneal neovascularization, with or without ulceration, characterizes qualitative tear diseases. Tear components other than lipid and mucin that carry probable clinical significance include tear proteins, all-trans retinal, cholesterol, glucose, and electrolytes. Although less common than quantitative or aqueous deficiencies, qualitative abnormalities are recognized as primary or secondary causes of ocular surface disease in companion animals.

Mucus alteration and eye dryness. A possible relationship

From a very early phase we studied 15 patients suffering from a dry-eye condition ant associated to systemic diseases. Conjunctival biopsies were studied in Transmission (TEM) and Scanning (SEM) electron microscopy. Moreover, the lectin-gold cytochemistry at ultrastructural level was applied to investigate the distribution of some glycosidic receptors produced by both the goblet cells and the vesicles belonging to the Second Mucus System (SMS). No evidence of epithelial stratification and only a decrease in the goblet cell population was observed. The SMS vesicles and the superficial cell microvilli did not appear greatly reduced in number. A difference in the mucus composition in terms of content of glycosidic residues was detected in dry-eye patients compared to the normal subjects. The role of the mucus produced by both the goblet cells and the SMS vesicles in debated. A possible correlation between the alteration of the mucus content and the failure of the tear film stability is proposed. On the basis of these data, a new therapeutic approach for eye dryness is suggested.

Conjunctival goblet cell response to vasoconstrictor use

Vasoconstrictors such as phenylephrine and naphazoline are used in ophthalmology to decrease hyperemia associated with allergic conjunctivitis and contact lens wear. There is a suspicion, however, that chronic use of these agents can produce dry-eye symptoms in some patients. The purpose of this study was to determine whether vasoconstrictor use interferes with tear film adequacy by decreasing mucin-secreting goblet cells. Cellulose acetate filter strip impressions were taken from the bulbar conjunctiva of rabbit eyes treated with vasoconstrictors or artificial tears for varying periods of time, and the number of goblet cells per light microscopic field counted. There was no significant difference between the number of goblet cells in control and vasoconstrictor-treated animals within each time period. These results indicate that conjunctival goblet cell density is not significantly affected by topical vasoconstrictor use.

An improved processing method for electron microscopy investigation of conjunctival biopsies

A new schedule in the processing of conjunctival biopsies for ultrastructural investigations is proposed. The specimens are first examined in Scanning Electron Microscopy (SEM), briefly rehydrated and secondly processed for observation in Transmission Electron Microscopy (TEM). The rehydration counterbalances the shrinkage due to the previous processing steps applied for SEM examination and allows a good TEM morphology of the recovered specimens to be achieved. The correlative SEM/TEM study on the same conjunctival biopsy provides complete informations on both the surface and the inner structure of the tissue. This appears of value in the investigation of conjunctival biopsy from eyes affected by tear film quantitative and/or qualitative alterations.

Electron microscopy of impression-acquired conjunctival epithelial cells

The authors describe a technique with which one can perform electron microscopy on conjunctival epithelial cells acquired by impression cytology. With adjacent excisional and impression biopsies of conjunctival epithelium in patients having mucopolysaccharidoses (MPS), typical fibrillo-granular inclusions are shown. This noninvasive procedure has potential for the study of subcellular, cellular, and intercellular morphology in diseases of the ocular surface.

Detection of mucus glycoconjugates in human conjunctiva by using the lectin-colloidal gold technique in TEM. II. A quantitative study in dry-eye patients

The mucus glycoconjugates produced by conjunctival goblet cells in dry-eye patients were studied by a specific cytochemical reaction in Transmission Electron Microscopy (TEM). Four lectins, proteins of vegetal origin which specifically bind glycosidic residues, (WGA, PNA, SBA and ConA) were used conjugated with colloidal gold as ultrastructural marker. We performed a quantitative analysis by counting the colloidal gold particles present on mucus granules. The results were compared with normal conditions. We found a decrease in sialic acid, N-acetyl-glucosamine, N-acetyl-galactosamine and galactose-N-acetyl-galactosamine and an increase in mannose. The different content of glycoconjugates in goblet cells may reflect in the change of physical and functional properties of mucus. We think these data may be useful in the search for a therapeutic mucomimetic drug.