Ultrastructural and histochemical observations of respiratory epithelium and gland

Presence of sialic acids in bronchioloalveolar cells and identification and quantification of N-acetylneuraminic and N-glycolylneuraminic acids in the lung

The lung, in air-breathing vertebrates, is a tree-like structure composed of branching tubes ending in alveoli and lined by diverse and highly specialized epithelial cells. A dense array of complex and diverse glycoconjugates is present on essentially all animal cell surfaces. Sialic acids are widely allocated at the outermost ends of glycan chains, attached to membrane proteins and lipids below. Due to their abundance and their terminal position in glycans, sialic acids are implicated in many physiological and pathological functions. Although the composition of lung epithelial cell-surface glycans has been studied over the years, it is not yet completely understood. In the present work, we aimed to histochemically localize N-acetylneuraminic acid (Neu5Ac)>N-glycolylneuraminic acid (Neu5Gc) residues on rat bronchioloalveolar epithelial cell surfaces using light microscopy (LM) methods. In lung membranes isolated from adult rat lung homogenates, we also separated, identified and quantified Neu5Ac and Neu5Gc by means of high-performance liquid chromatography (HPLC), and systematically described the optimized HPLC methods used. Sialic acid residues were localized on the surface coat of bronchioloalveolar cells, and the mean quantification of Neu5Ac and Neu5Gc in the adult rat lung homogenates was 12,26 and 2,73 μg/mg prot., respectively, revealing a manifest preponderance of Neu5Ac. A coefficient of variation (CV) of 4,98% and 4,40%, respectively was obtained and an optimal dispersion variability expressed by the SD and the CV was also reported, confirming the efficiency of the methodology. To the best of our knowledge, our group was the first to identify, separate and quantify sialic acids in purified lung membranes. The presence of these residues contributes to a strong anionic shield and may provide an hydrating and protective barrier as well as a repulsive structure that is crucial to lung physiology.

Synthesis of thiolated, PEGylated and POZylated silica nanoparticles and evaluation of their retention on rat intestinal mucosa in vitro

In this study, we synthesised thiolated silica nanoparticles using 3-mercaptopropyltrimethoxysilane and functionalised them with either 5 kDa methoxy polyethylene glycol maleimide (PEG) or 5 kDa alkyne-terminated poly(2-ethyl-2-oxazoline) (POZ). The main objectives of this study are to investigate the effects of pH on the size and ξ-potential of these nanoparticles and evaluate their mucoadhesive properties ex vivo using rat intestinal mucosa. The sizes of thiolated, PEGylated and POZylated silica nanoparticles were 53 ± 1, 68 ± 1 and 59 ± 1 nm, respectively. The size of both thiolated and POZylated nanoparticles significantly increased at pH ≤ 2, whereas no size change was observed at pH 2.5-9 for both these two types of nanoparticles. On the other hand, the size of PEGylated nanoparticles did not change over the studied pH range (1.5-9). Moreover, thiolated nanoparticles were more mucoadhesive in the rat small intestine than both PEGylated and POZylated nanoparticles. After 12 cycles of washing (with a total of 20 mL of phosphate buffer solution pH 6.8), a significantly greater amount of thiolated nanoparticles remained on the intestinal mucosa than FITC-dextran (non-mucoadhesive polymer, p < 0.005) and both PEGylated and POZylated nanoparticles (p < 0.05 both). However, both PEGylated and POZylated nanoparticles showed similar retention to FITC-dextran (p > 0.1 for both). Thus, this study indicates that thiolated nanoparticles are mucoadhesive, whereas PEGylated and POZylated nanoparticles are non-mucoadhesive in the ex vivo rat intestinal mucosa model. Each of these nanoparticles has potential applications in mucosal drug delivery.

Mucoadhesive vs. mucopenetrating particulate drug delivery

Mucus layer is a hydrophilic absorption barrier found in various regions of the body. The use of particulate delivery systems showed potential in drug delivery to mucosal membranes by either prolonging drug residence time at the absorption or target membrane or promoting permeation of particles across mucus gel layer to directly reach underlying epithelium. Mucoadhesive particles (MAP) are advantageous for delivering drug molecules to various mucosal membranes including eyes, oral cavity, bladder and vagina by prolonging drug residence time on those membranes. In contrast, a broader particle distribution and deeper penetration of the mucus gel layer are accomplished by mucopenetrating particles (MPP) especially in the gastrointestinal tract. Based on the available literature in particular dealing with in vivo results none of both systems (MAP and MPP) seems to be advantageous over the other. The choice of system primarily depends on the therapeutic target and peculiar properties of the target mucosa including thickness of the mucus gel layer, mucus turnover rate and water movement within the mucus. Future trends are heading in the direction of combining both systems to one i.e. mucoadhesive and mucopenetrating properties on the same particles.

Histochemical and ultrastructural observations of respiratory epithelium and gland in yak (Bos grunniens)

Submucous glands and epithelial mucous cells of yak (Bos grunniens) respiratory tract have been studied by a variety of histochemical methods and transmission electron microscopy for differentiating and characterizing serous and mucous cells. By light microscopy, the distribution, numbers of mucous cells, volume of mucous glands (Reid index), and the ratio of mucous cell to serous cell in the bronchial tree were measured with different staining. Histochemically, a majority of mucous cells, presented in the surface epithelium of bronchi and glands, secreted neutral and acid mucosubstances, only a few sulfated mucosubstances were present. No mucus-producing cells were observed from the terminal to respiratory bronchiolar level. Ultrastructurally, serous cells in glands of the lamina propria had two distinct forms: one type filled with many round dense secretory granules, plentiful RER and few other organelles, similar to other animals; the other type contained some oval mitochondrial and distended RER, the granules resembled the former. The mucous cells in gland were similar to that of epithelium, which containing abundant secretory granules with an eccentric core. The mucous cells of the surface epithelium differ from other animals in the structure and histochemistry of their secretory granules. Analysis of the size and distribution of the secretory granules and other organelles of serous cells suggested that differences represent different phases of a secretory cycle, not various populations of cell or granules.

Upper airway mucin gene expression: a review

INTRODUCTION

The gel-like properties of mucus depend primarily on its content of mucins. The protein backbones of mucins are encoded by mucin genes. Of the currently known 20 mucin genes that encode protein backbone of mucins, 16 have been identified in the airways.

METHOD

We explored the current knowledge about upper airway mucin expression in health and disease conditions using a Medline search. We have also studied upper airway mucin gene expression and compared our results with the results from other studies.

RESULTS

MUC5AC, MUC5B, and MUC2 are the principal gel-forming mucins secreted in the airway. However, the spectrum of mucin expression in chronic upper airway diseases such as nasal polyps, chronic sinusitis, middle ear effusion, and cystic fibrosis is generally wide and variable.

DISCUSSION

The wide spectrum of upper airway mucin expression is possibly caused by various anatomic and histologic features as well as physiologic and pathologic variables. These variables have not been fully explored yet, and the majority of airway mucin expression studies used small numbers of samples.

CONCLUSION

Studies including adequate numbers of samples (patients) are more likely to reveal a clearer profile and more precise expression patterns. Generating a clear profile of mucin expression patterns in health and disease requires the analysis of different variables, which can alter that expression. It is also essential to understand the various molecular mechanisms controlling mucin gene and protein expression. This could lead to the invention of novel therapeutic modalities to treat upper airway diseases.

TFF peptides in the human false vocal folds of the larynx

TFF peptides (formerly P domain peptides, trefoil factors) are typical secretory products of mucin-producing cells and are thought to influence the rheological properties of mucous gels. We investigated the localization of these peptides in the human false vocal folds of the larynx, also known as the ventricular folds or vestibular folds. An analysis of TFF peptide mRNA by RT-PCR and TFF protein by Western blot detected TFF1 and TFF3, but not TFF2. Immunohistochemistry revealed TFF1 to be associated with the secretory product of goblet cells and mucous parts of subepithelial seromucous glands. TFF3 occurred in columnar epithelial cells of the mucosa and in serous cells and excretory duct cells of seromucous glands. These peptides may play a role in the rheological function of mucus secreted onto the true vocal folds and are thus important constituents of vocal production.

Glycocalyx of lung epithelial cells

Due to their diversity and external location on cell membranes, glycans, as glycocalyx components, are key elements in eukaryotic cell, tissue, and organ homeostasis. Although information on the lung glycocalyx is scarce, this article aims to review, discuss, and summarize what is known about bronchoalveolar glycocalyx composition, mainly the sialic acids. It was deemed relevant, however, to make a brief introductory overview of the cell glycocalyx and its particular development in epithelial cells. After that, follows a summary of the evolution of the knowledge regarding the bronchoalveolar glycocalyx composition throughout the years, particularly its morphological features. Since sialic acids are located terminally on the bronchoalveolar lining cells' glycocalyx and play crucial roles, we focused mainly on the existing lung histochemical and biochemical data of these sugar residues, as well as their evolution throughout lung development. The functions of the lung glycocalyx sialic acids are discussed and interpretations of their roles analyzed, including those related to the negative overall superficial shield provided by these molecules. The increasing presence of these sugar residues throughout postnatal lung development should be regarded as pivotal in the development and maintenance of a dynamic bronchoalveolar architecture, supporting the normal histophysiology of the respiratory system. The case for a profound knowledge of lung glycocalyx--given its potential to provide answers to serious clinical problems--is made with particular reference to cystic fibrosis. Finally, concluding remarks and perspectives for future research in this field are put forth.

Ultrastructural of the bronchial epithelium in chronic inflammation

Light-optic and electron microscopic study of the bronchial biopsy specimens from 208 patients with primary and secondary chronic bronchitis was carried out. Variants of the bronchial epithelium states were described and classified according to characteristics of differentiation processes. As a result, groups with relatively normal structure, with deviated differentiation processes (hyperplasia of goblet glandular cells, hyperplasia of basal epithelial cells, hypoplasia and degeneration of goblet glandular cells), with incomplete differentiation processes (proliferative transformation and transitory state), and with altered differentiation processes (squamous metaplasia and atrophy) were described. These variants of the bronchial epithelium states are not only indicative of different levels of change or structural disorders, but may also represent a dynamic scheme of its consecutive changes during the development of chronic inflammatory process.

Levels of intracellular protein and messenger RNA of mucin and lysozyme in normal human nasal and polyp epithelium

OBJECTIVES

Mucus hypersecretion is a characteristic feature in chronic sinusitis with nasal polyps. The objective of this study is to examine whether the polyp epithelium itself contributes to a certain extent to the increased mucous secretions in chronic sinusitis with nasal polyps, and if it does, to determine which mucin genes are responsible for the increased mucin secretion.

METHODS

Three pooled samples of normal nasal epithelial cells from each subject were obtained by scrapings from the inferior turbinates of 30 healthy adult volunteers and nasal polyps from 6 patients who underwent intranasal ethmoidectomy and polypectomy. Isolated epithelial cells were used for total RNA isolation for reverse transcriptase polymerase chain reaction and cell lysates for immunoblotting.

RESULTS

The intracellular level of mucin from polyp epithelium was 2.9 times higher than that of normal nasal epithelium (P < .05). Interestingly, MUC2 and MUC8 messenger RNA (mRNA) levels were clearly upregulated in polyp epithelium compared with those of normal turbinate epithelium.

CONCLUSIONS

Polyp epithelium can be considered to contribute in part to increased secretion in chronic sinusitis with polyps, and increased mucous secretion might be related to the increased mRNA level of MUC2 or MUC8 or both.

Characterization of cell surface lectin-binding patterns of human airway epithelium

Glycosylated structures on the cell surface have a role in cell adhesion, migration, and proliferation. Repair of the airway epithelium after injury requires each of these processes, but the normal cell surface glycosylation of non-mucin producing airway epithelial cells is unknown. We examined cell surface glycosylation in human airway epithelial cells in tissue sections and in human airway epithelial cell lines in culture. Thirty-eight lectin probes were used to determine specific carbohydrate residues by lectin-histochemistry. Galactose or galactosamine-specific lectins labeled basal epithelial cells, lectins specific for several different carbohydrate structures bound columnar epithelial cells, and fucose-specific lectins labeled all airway epithelial cells. The epithelial cell lines 1HAEo- and 16HBE14o- bound lectins that were specific to basal epithelial cells. Flow cytometry of these cell lines with selected lectins demonstrated that lectin binding was to cell surface carbohydrates, and revealed possible hidden tissue antigens on dispersed cultured cells. We demonstrate specific lectin-binding patterns on the surface of normal human airway epithelial cells. The expression of specific carbohydrate residues may be useful to type epithelial cells and as a tool to examine cell events involved in epithelial repair.

Use of antibodies directed against blood group substances and lectins together with glycosidase digestion to study the composition and cellular distribution of glycoproteins in the large human airways

Some 30 lectins in combination with glycosidase digestion and immunohistochemistry with 5 antibodies directed against antigens of the ABO and Lewis blood group systems were used to analyse the distribution and synthesis of glycoconjugates in the epithelium of the large airways in man. Both mucous gland cells and goblet cells were labelled by 12 of 30 lectins and by the antibodies, dependent on the ABO, Lewis, and secretor status. The corresponding binding patterns of the serous gland cells differed markedly from those of goblet and mucous gland cells and in general were not dependent on the ABO, Lewis, and secretor status. After digestion with neuraminidase and fucosidase, binding of soy bean agglutinin and peanut agglutinin to goblet and mucous gland cells was increased. Binding of peanut agglutinin to serous gland cells was stronger only after the digestion with neuraminidase. Digestion with O-glycosidase after the use of neuraminidase or fucosidase resulted in a decrease of peanut agglutinin binding to goblet and mucous gland cells. The present results show that the secretory products of goblet and mucous gland cells on the one hand and those of serous cells on the other differ considerably with respect to their terminal glycosylation. The glycosyltransferases coded by genes of the ABO and Lewis blood group and secretor systems are active only in goblet and mucous gland cells, resulting in the presence of the corresponding antigens. Precursor substances of blood group antigens types 1, 2, and 3 are found only in these cell types. In serous gland cells, blood group systems do not influence the glycosylation of glycoproteins. The results of the digestion with O-glycosidase indicates the presence of O-glycosylation in mucous gland and goblet cells, but not in serous gland cells.

Respiratory mucins: identification of core proteins and glycoforms

At least eight mucin apoproteins are expressed by the tracheobronchial epithelium, but it is not known which, if any, of these are major constituents of the respiratory secretions responsible for the formation of the mucus gel. To address this we have isolated mucins from normal, asthmatic and chronic bronchitic secretions. The asthmatic mucin reduced subunits were fractionated into four populations (I-IV) by anion-exchange HPLC. Amino acid and monosaccharide compositional analysis, as well as M(r) and size measurements, indicate that two of these populations (I and II) are glycoforms of the same or related apoprotein(s) and that the other populations contain two different apoproteins. A panel of antibodies and antisera recognizing the variable number tandem repeat (VNTR) of specific mucin apoproteins did not, as predicted, react with the glycosylated molecules, but after deglycosylation the majority of these probes (with the exception of those to MUC2, which were negative) reacted at a low level with each of the subunit populations. In contrast, an antiserum against a non-VNTR sequence of MUC5AC identified one of the populations (III) as the MUC5AC mucin. The MUC5AC reduced subunit had an M(r) of 2.2 x 10(6) and an RG (radius of gyration) of 57 nm. The genetic identities of the major mucin (populations I and II) and a minor component (population IV) were not established. The MUC5AC mucin was also identified as a major component in the pooled normal secretions from 20 individuals, whereas in a chronic bronchitic sample it was only a minor constituent. Furthermore, in all these different respiratory secretions the MUC5AC mucin appears as a similar biochemical entity, as assessed by Mono Q chromatography and agarose electrophoresis, suggesting that it may have a well-defined pattern of glycosylation in the respiratory tract.

An evaluation of mucus glycoproteins in the larynges of victims of sudden infant death syndrome

Larynges from 24 victims of Sudden Infant Death Syndrome (S.I.D.S.) and 10 controls, with ages ranging from two days to 24 weeks in the controls and from two to 116 weeks in the S.I.D.S. victims, were transversely, step-serially sectioned and then stained to show acid, neutral and mixed mucus glycoproteins. The proportion of sulphated mucus glycoprotein and sialylated mucus glycoprotein to total acid mucus glycoprotein was determined by the use of various staining techniques and a comparison was made for each type between S.I.D.S. and controls. The differences were significant with a mean of 27 per cent in the controls compared to 59 per cent in the S.I.D.S. for sulphomucin (difference 32 per cent; standard error of difference 6 per cent; p < 0.01) and 73 per cent in the controls compared to 41 per cent in the S.I.D.S. larynges (difference 32 per cent; standard error of difference six per cent; p < 0.01) for sialomucin. The results suggest that sulphated mucus glycoprotein is secreted in excess in some victims of Sudden Infant Death Syndrome.

Regeneration of respiratory epithelia in the rat after free grafting

Following free grafting of septal mucosa from the rat to the rectus abdominis muscle, the mucosal membrane was found to degenerate into a flat squamous epithelium with loss of the majority of differentiated epithelial cells. Both the goblet cells and ciliated cells regenerated from stem cells, which appear in large numbers 2 days after transplantation. Microvilli were found initially on the surfaces of developing ciliated cells and were replaced 21 days post-grafting by cilia. The number of goblet cells during regeneration at first exceeded that of the ciliated cells, but decreased with the passage of time. After 4 months there were more ciliated cells, with the respiratory epithelium now appearing no different than the initially transplanted nasal mucosa.

Heterogeneity of mucus glycoproteins from cystic fibrotic sputum. Are there different families of mucins?

High-Mr mucin glycopeptides prepared from sputum of an individual with cystic fibrosis (CF) were studied by ion-exchange h.p.l.c. The glycopeptides were heterogeneous and a number of partially resolved populations were identified. Whole mucins from the gel phase were separated into four fractions by isopycnic density-gradient centrifugation in CsCl, and high-Mr glycopeptides from these fractions were examined by ion-exchange h.p.l.c. The acidic nature of the high-Mr glycopeptides increased with increasing buoyant density of the intact mucins, and a periodate-Schiff (PAS)-rich and an extremely high-iron diamine (HID)-reactive component were present in the lowest and highest density fractions respectively. The various glycopeptide populations were identified in different proportions in mucins from four other individuals with CF. CF sputum thus seems to contain distinct mucin populations containing different oligosaccharide clusters corresponding to these high-Mr glycopeptides.

Mucus glycoproteins from cystic fibrotic sputum. Macromolecular properties and structural 'architecture'

Mucus glycoproteins (mucins) were isolated from sputum of patients with cystic fibrosis (CF) after separation into sol and gel phases. The mucus gel was solubilized with gentle stirring in 6 M-guanidinium chloride supplemented with proteinase inhibitors, and purification of mucins was subsequently achieved by isopycnic density-gradient centrifugation in CsCl/guanidinium chloride. Density-gradient centrifugation also revealed a heterogeneity of the macromolecules, the pattern of which varied between individuals, and mucins from the gel phase was pooled as 'heavy' and 'light' fractions. Gel chromatography on Sepharose CL-2B showed that the heavy fraction contained a larger proportion of smaller species than the 'light' fraction and that the gel phase mucins were much larger than those from the sol. An apparently homogeneous high-Mr mucin population from one individual contained approx. 70% (w/w) carbohydrate, the major sugars being N-acetylglucosamine (17.8%), N-acetylgalactosamine (6.7%), galactose (20.7%), fucose (13.2%) and sialic acid (11.4%). These mucins had an S020.w of 47 S, and an Mr of 15 x 10(6) -20 x 10(6), and rate-zonal centrifugation revealed a polydisperse size distribution [range (5-30) x 10(6)] with a weight-average Mr of 17 x 10(6). The whole mucins were visualized with electron microscopy as linear and apparently flexible threads, disperse in size. Reduction produced subunits which were included on Sepharose CL-2B, and subsequent trypsin digestion yielded high-Mr glycopeptides which were further retarded. The size distributions and fragmentation patterns of mucin from two other CF patients were the same, as studied by gel chromatography, rate-zonal centrifugation and electron microscopy. We conclude that CF mucins are heterogeneous in both size and buoyant density and that the various populations, though differing in buoyant density, share the same architecture and macromolecular properties and are, in this respect, similar to mucins from normal respiratory secretions [Thornton, Davies, Kraayenbrink, Richardson, Sheehan & Carlstedt (1990) Biochem. J. 265, 179-186] and human cervical mucus [Carlstedt & Sheehan (1989) SEB Symp. XLIII 289-316].

Histochemical characterization of glycoconjugates in the epithelium of the extrapulmonary airways of several vertebrates

The glycoconjugates of the extrapulmonary airways of 11 tetrapode vertebrates have been characterized by means of both conventional and lectin histochemistry. Abundant sialosulphomucins were detected in the secretory cells and periciliary layer of turtles, snakes, birds and mammals while only sialomucins were observed in amphibians. Neutral and traces of acidic mucins were detected in the secretory cells of lizards. The secretory cells of the amphibian airways were reactive to Con-A, DBA and WGA. No alpha-L-fucose residues reactive with UEA-I or LTA were detected in amphibians. The goblet cells of the turtles were stained by DBA, SBA and WGA. Secretory cells of snakes and lizards reacted with Con-A and WGA. The mucous goblet cells of the birds were reactive to Con-A, LTA and WGA. In the chicken, they also showed affinity for PNA and SBA. The ciliated cells of the avian species studied were stained by Con-A and WGA. Mammalian goblet cells were reactive to Con-A, UEA-I and WGA. In the rat, affinity for DBA and SBA was also observed. The present results reveal the existence of marked differences in the sugar residues of the glycoconjugates of the extrapulmonary airways of tetrapode vertebrates. Only sialic acid residues appear to be constant constituents of the glycoconjugates of the airways of all species studied.

Changes in epithelial secretory cells and potentiation of neurogenic inflammation in the trachea of rats with respiratory tract infections

In rats respiratory tract infections due to Sendai virus and coronavirus usually are transient, but they can have long-lasting consequences when accompanied by Mycoplasma pulmonis infections. Morphological alterations in the tracheal epithelium and a potentiation of the inflammatory response evoked by sensory nerve stimulation ("neurogenic inflammation") are evident nine weeks after the infections begin, but the extent to which these changes are present at earlier times is not known. In the present study we characterized these abnormalities in the epithelium and determined the extent to which they are present 3 and 6 weeks after the infections begin. We also determined the magnitude of the potentiation of neurogenic inflammation at these times, whether the potentiation can be reversed by glucocorticoids, and whether a proliferation of blood vessels contributes to the abnormally large amount of plasma extravasation associated with this potentiation. To this end, we studied Long-Evans rats that acquired these viral and mycoplasmal infections from other rats. We found that the tracheal epithelium of the infected rats had ten times as many Alcian blue-PAS positive mucous cells as did that of pathogen-free rats; but it contained none of the serous cells typical of pathogen-free rats, so the total number of secretory cells was not increased. In addition, the epithelium of the infected rats had three times the number of ciliated cells and had only a third of the number of globule leukocytes. In response to an injection of capsaicin (150 micrograms/kg i.v.), the tracheas of the infected rats developed an abnormally large amount of extravasation of two tracers, Evans blue dye and Monastral blue pigment, and had an abnormally large number of Monastral blue-labeled venules, particularly in regions of mucosa overlying the cartilaginous rings. This abnormally large amount of extravasation was blocked by dexamethasone (1 mg/day i.p. for 5 days). We conclude that M. pulmonis infections, exacerbated at the outset by viral infections, result within three weeks in the transformation of epithelial serous cells into mucous cells, the proliferation of ciliated cells, and the depletion of globule leukocytes. They also cause a proliferation of mediator-sensitive blood vessels in the airway mucosa, which is likely to contribute to the potentiation of neurogenic inflammation that accompanies these infections.

Tracheobronchial epithelium of the sheep: III. Carbohydrate histochemical and cytochemical characterization of secretory epithelial cells

We examined histochemically (light microscopy-LM) and cytochemically (electron microscopy-EM) the secretory epithelial cells in the tracheobronchial mucosa of sheep. Six morphologically distinct, granule-containing cells have been described, on the basis of their morphology and airway distribution: four mucous (M1-M4), serous (SC), and Clara (CC). Stereological and morphometric data indicated that M3, M4, SC, and CC were distinctly different from each other and from M1 and M2 cells. Mucous cells M1 and M2 differed in granule morphology. Samples of tracheas, sixth-generation bronchi, distal bronchi, and terminal bronchioles of 18 adult sheep were examined. At the LM level, methacrylate sections were reacted with an alcian blue (pH 2.5), periodic acid Schiff (PAS) sequence to differentiate neutral from acidic glycoconjugates (GC), and a high-iron diamine (HID), alcian blue sequence to differentiate sulfated from nonsulfated (sialylated) GC. At the EM level the periodic acid-thiocarbohydrazide localized hexose-rich, neutral GC. Dialyzed iron (DI) and high-iron diamine localized carboxylated and sulfated GC, respectively. Granules of all but Clara cells were PAS-positive. All mucous cells contained acidic groups, but only M1 and M4 cells had LM-detectable sulfated GC. At the ultrastructural level, minimal but discernible HID and LID reaction product was observed on granule profiles of M2, M3, and SC, indicating acidic and sulfated GC not detected at the LM level. Histochemically, the sheep tracheobronchial epithelium was more similar to that of humans than some other examined mammalian species.

An altered lectin binding to mucus glycoprotein in goblet cells of human tracheobronchial epithelium among former mustard-gas workers

Lectins, which are well known to have an ability to bind with specific carbohydrate residues of glycoprotein, have been used to examine cellular changes associated with malignant transformation. For the analysis of mucus glycoprotein of goblet cells in the tracheobronchial epithelium, 192 paraffin-embedded sections from 54 autopsy cases including the cases with a history of mustard-gas (MG) exposure were stained with seven plant lectins using PAP method. PNA binding with no neuraminidase treatment as well as BSA-1 binding was observed most frequently in MG-exposed lung cancer cases. The proportion of cases positive for SBA binding in MG-exposed and/or lung cancer cases had a statistical difference from non-MG-exposed non-lung cancer cases. These observations may indicate a large heterogeneity in oligosaccharide chains of mucus glycoprotein and suggest its incomplete or abnormal synthesis, which is most likely to be due to previous exposure to carcinogen, such as MG.

Carbohydrate cytochemistry of rhesus monkey tracheal submucosal glands

This study was designed to characterize the ultrastructure and carbohydrate content of secretory cells in submucosal glands of rhesus monkey and to compare this information with that available for humans. The tracheas from five adult monkeys were fixed by airway infusion, processed, and embedded for both light and transmission electron microscopy. Histochemical strains including alcian blue-periodic acid-Schiff, dialyzed iron, and high-iron diamine-alcian blue were applied to serial glycol methacrylate sections. The cytochemical stains used included periodic acid-thiocarbohydrazide-silver proteinate, high-iron diamine, and low-iron diamine. The glandular secretory cells were divided into four categories based on ultrastructure and location within the gland. Cells in the first category resembled the mucous cell of the surface epithelium and were located in ducts most proximal to the tracheal lumen. The second category consisted of cells that were located in distal ducts and contained large electron-lucent granules. The granules in both of these cell groups contained material that was periodate-reactive and sulfated. Cells of the third category contained granules that were either electron-lucent or electron-dense. These cells, which were difficult to characterize as either serous or mucous, were located in secretory tubules and acini and contained periodate-reactive glycoconjugates that were either sulfated or nonsulfated. The last category consisted mainly of cells that contained electron-dense granules that were lightly periodate-reactive or a few that were unreactive with any of the cytochemical methods used here.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate cytochemistry of rhesus monkey tracheal epithelium

Three types of nonciliated secretory epithelial cells contribute material to the mucous lining of pulmonary airways: mucous cells, serous cells, and Clara cells. Extensive interspecies variation exists, especially between humans and laboratory mammals, with regard to occurrence, distribution, and granule content of these secretory cells. This study was designed to characterize one aspect of these differences in one species of nonhuman primate, the rhesus monkey. The complex carbohydrates of secretory granules present in the tracheal epithelium were characterized cytochemically. The tracheas of seven monkeys were fixed by airway infusion, processed, and embedded for both light and transmission electron microscopy. Histochemical stains including Alcian blue-periodic acid Schiff, dialyzed iron, and high iron diamine-Alcian blue were applied to serial methacrylate sections. The mucous cells were the predominant secretory cell type of the trachea and contained periodate-reactive sulfated glycoconjugates. The mucous secretory granules, as resolved with the electron microscope, consisted of a mesh or matrix surrounding a biphasic core. The matrix was stained by all cytochemical reactions used, which included periodic acid-thiocarbohydrazide-silver proteinate, dialyzed iron, low iron diamine, and high iron diamine. The biphasic core also reacted with the four stains, but most intensely with high iron diamine. We conclude from this study that 1) the mucous secretory granule contains carbohydrate throughout all phases of the granule, 2) the mucous granule contains periodate-reactive sulfated glycoconjugates, with sulfate esters concentrated in the core of the granule, and 3) the mucous granules of rhesus trachea morphologically and cytochemically resemble those described in human airways.