Ultrastructural visualization of galactosyl residues in various alimentary epithelial cells with the peanut lectin-horseradish peroxidase procedure

The Regulated Secretion and Models of Intracellular Transport: The Goblet Cell as an Example

Transport models are extremely important to map thousands of proteins and their interactions inside a cell. The transport pathways of luminal and at least initially soluble secretory proteins synthesized in the endoplasmic reticulum can be divided into two groups: the so-called constitutive secretory pathway and regulated secretion (RS) pathway, in which the RS proteins pass through the Golgi complex and are accumulated into storage/secretion granules (SGs). Their contents are released when stimuli trigger the fusion of SGs with the plasma membrane (PM). In specialized exocrine, endocrine, and nerve cells, the RS proteins pass through the baso-lateral plasmalemma. In polarized cells, the RS proteins secrete through the apical PM. This exocytosis of the RS proteins increases in response to external stimuli. Here, we analyze RS in goblet cells to try to understand the transport model that can be used for the explanation of the literature data related to the intracellular transport of their mucins.

PNA: A Marker of Neoplastic Progression and Differentiation in the Gastrointestinal Tract

We examined 35 cases of stomach carcinoma and 40 cases of colonic carcinoma with PNA associated with peroxidase (peanut agglutinin, lectin which binds to the terminal disaccharide galactose β (1, 3)-N-acetil-galacto-samine).

In this way evaluation of the functional aspects of the normal-neoplastic sequence was undertaken. This method was carried out for histological and ultrastructural investigations. The results obtained in both cases showed a different reactivity in the evolution of neoplastic disease: in fact, positivity in dysplasia is finely granular intracytoplasmic, whereas in well-differentiated neoplastic transformation such a reactivity is preferentially localized along the cellular membranes, with restoration of gross positivity in the cytoplasm for the poorly-differentiated neoplasm. We therefore believe PNA to be a marker not only of neoplastic progression but of differentiation as well: we also hypothesize it to reveal glycoprotein groups with possible antigenic power, involved in immunologic interactions between tumor and host.

Lectin histochemistry for light and electron microscopy

Glycoconjugates are complex macromolecules present in all tissues throughout the body. Depending on the tissue region, glycoconjugates express different carbohydrate moieties, which can be used to both distinguish cell type and examine changes in cell phenotype.Although the periodic acid-schiff (PAS) method has long been used to study the distribution of glycoconjugates, the usefulness of the technique is severely limited by its lack of specificity. A more specific technique makes use of the affinity that plant-derived lectins have for different carbohydrate moieties in glycoconjugates. Binding of lectins is therefore a particularly useful adjunct to conventional histology when it is important to characterise cell type. These well-characterised binding patterns have proved particularly valuable in helping us understand the pathogenesis of kidney disease, changes in cell surface carbohydrates on normal and neoplastic cells in tumours, and blood group biology.When labeled with a reporter molecule such as biotin or gold, lectin binding can be easily identified using light and electron microscopy. In this chapter, we describe the appropriate experimental protocols for light and electron microscopic examination of lectin binding, emphasising their utility in characterising nephron segments in renal disease.

Histochemical demonstration of two subtypes of O-linked oligosaccharides in the rat gastric glands

The gastric glands synthesize glycoproteins whose oligosaccharides are linked to the peptide core mainly by the O-glycosidic bond, specifically removed by beta-elimination procedure. Our aim was to research the possibility of the existence of two subtypes of O-linked oligosaccharides with a different behavior to the removal procedure. The lectins from peanut (PNA) and Maackia amurensis (MAA-I) were histochemically used as markers of the O-linked oligosaccharides. Sections were also pretreated with beta-elimination and/or peptide N-Glycosidase F (PNGase-F) for the specific removal of O- and N-linked oligosaccharides, respectively. The lectin GNA, which mainly labels to N-linked oligosaccharides, was used to test the correct working of PNGase-F. To test the possibility that the beta-elimination treatment could remove the terminal sialic acid residues, the lectin LFA was used. The surface epithelium was negative to PNA, while it became strongly positive when beta-elimination was performed for 1 day. This staining was resistant to PNGase-F, suggesting that PNA was labeling to O-linked oligosaccharides. However, after beta-elimination for 5 days this staining is not observed. A similar pattern appeared with MAA-I. We propose the existence of two subtypes of O-linked oligosaccharides: labile and resistant. The labile O-linked oligosaccharides are removed with beta-elimination for 1 day, unmasking the PNA-positive oligosaccharides. These oligosaccharides are resistant O-linked oligosaccharides because staining is abolished with longer treatment of beta-elimination. The results with MAA-I also support this suggestion. In summary, the labile O-linked oligosaccharides are removed with short treatment, while the resistant O-linked oligosaccharides need a stronger procedure (for 5 days).

Analysis of the distribution of binding sites for the plant lectin Bandeiraea simplicifolia I-isolectin B4 on primary sensory neurones in seven mammalian species

The purpose of the present study was to investigate the binding patterns of the plant lectin Bandeiraea simplicifolia I-isolectin B(4) (BSI-B(4)) to sensory neurones in seven mammalian species. The dorsal root ganglia and spinal cords of three rats, mice, guinea pigs, rabbits, flying foxes, cats, and marmoset monkeys were screened for BSI-B(4) using lectin histochemistry. BSI-B(4) binding was associated with the soma of predominantly small-diameter primary sensory neurones in the dorsal root ganglia and their axon terminals within laminae I and II of the superficial dorsal horn in all seven species. The similarities of lectin binding patterns in each of these species suggest that the glycoconjugate to which BSI-B(4) binds has a ubiquitous distribution in mammals, and supports the proposal that this lectin may preferentially bind to a subpopulation of sensory neurones with a similar functional role in each of these species.

Distribution of binding sites for the plant lectin Ulex europaeus agglutinin I on primary sensory neurones in seven different mammalian species

There is an increasing body of evidence to suggest that different functional classes of neurones express characteristic cell-surface carbohydrates. Previous studies have shown that the plant lectin Ulex europaeus agglutinin-I (UEA) binds to a population of small to medium diameter primary sensory neurones in rabbits and humans. This suggests that a fucose-containing glycoconjugate may be expressed by nociceptive primary sensory neurones. In order to determine the extent to which this glycoconjugate is expressed by other species, in the current study, we have examined the distribution of UEA-binding sites on primary sensory neurones in seven different mammals. Binding sites for UEA were associated with the plasma membrane and cytoplasmic granules of small to medium dorsal root ganglion cells and their axon terminals in laminae I-III of the grey matter of the spinal cord, in the rabbit, cat and marmoset monkey. However, no binding was observed in either the dorsal root ganglia or spinal cord in the mouse, rat, guinea pig or flying fox. These results indicate an inter-species variation in the expression of cell-surface glycoconjugates on mammalian primary sensory neurones.

Correlation between shell colour and ultrastructure in pheasant eggs

1. The histochemistry and ultrastructure of pheasant eggs were compared on the basis of blue or brown shell colour. 2. Differences in lectin histochemistry of the outer shell membrane calcification surface indicate a biochemical disruption of the calcification sites in blue eggs. 3. Significant differences were observed in all aspects of eggshell ultrastructure with blue eggs having thinner shells with structural defects. 4. Poor hatchability of blue eggs may reflect high rates of weight loss associated with a defective eggshell.

Cytochemical images of secretion in Saccharomyces cerevisiae and animal cells are different

Like in animal cells, the major secretory pathway of the ascomycetous budding yeast Saccharomyces (s.) cerevisiae consists of membrane-bound compartments which transport soluble and membrane (glyco)peptides to lysosomal vacuoles, cell wall, or out of the cell. The established model of the cellular machinery of the yeast secretory pathway was deduced largerly from molecular ex situ analyses and for budding yeast cells it was assumed to be identical with that of secretory animal cells. Interphase yeast cells were never considered. Glycosylation of peptides was detected in the endoplasmic reticulum (ER) and the putative Golgi cisternae. Coated membrane vesicles were assumed to transport intermediates into and within the Golgi cascade. Proteolytic trimming would occur in the last Golgi compartment. Golgi-derived membrane vesicles would serve for exocytosis or fuse with lysosomal vacuoles. In contrast to this notion, yeast cytologists showed specific features of secretion in S. cerevisiae and other Ascomycetes. Cytochemical observations in situ of both dividing and interphase yeast showed direct communication between nuclear envelope, ER and segregated Golgi cisternae. A new class of constitutive conveyors, coated protein globules smaller than membrane vesicles, was shown to exist throughout the cell cycle. The function of Golgi-derived membrane vesicles was constrained to promotion of exocytosis in budding yeast. Some of the Golgi apparatus functions were detected in both these classes of exocytotic conveyors. Uptake (phagocytosis) of transport conveyors and lipoprotein condensates has been shown to deliver enzymes and secretory compounds into vacuoles. This simplified machinery of secretion, postulated for S. cerevisiae, does not include the Golgi cascade.

Protein glycosylation in the endoplasmic reticulum and the Golgi apparatus and cell type-specificity of cell surface glycoconjugate expression: analysis by the protein A-gold and lectin-gold techniques

High resolution immunolabeling applying the protein A-gold technique and carbohydrate cytochemistry using lectin-gold labeling on Lowicryl K4M and thawed-frozen thin sections are most useful approaches for the detection of protein antigens and lectin binding sites in intracellular organelles and the plasma membrane. They provided the basis for modern electron microscopic studies on protein glycosylation reactions and the identification of their subcellular localization as reviewed here. These studies have demonstrated organelle subcompartments and the cell type-specific compartmentation of endoplasmic reticulum and Golgi apparatus-associated glycosylation reactions. The other subject reviewed in this paper is cell surface glycoconjugates, as they are expressed in relation to specific cell types present in various organs and during cellular differentiation processes.

Selective stimulation of epithelial cells in colonic crypts: relation to active chloride secretion

Stimulation of Cl secretion by prostaglandin E2 (PGE2) was measured as the short-circuit current (Isc) across isolated epithelium of the rabbit distal colon. Cellular morphology of columnar and goblet cells during secretion was monitored using light and electron microscopy. Stimulation by PGE2 altered epithelial cell morphology only by a reduction of vacuolar space in the apical pole of crypt columnar cells, consistent with release of vacuole contents. Imaging of isolated crypts using differential interference microscopy confirmed the release of material from columnar cells during the onset of secretion. Inhibition of Cl secretion with the loop diuretic bumetanide did not block vacuole release. The actin filament-disrupting agent, cytochalasin, reduced the PGE2-stimulated Isc by 40% and blocked emptying of the vacuolar space. These electrical and morphological results indicate that the process of active ion secretion is associated with release of the macromolecular contents from apical vacuoles through a mechanism involving the cytoskeleton. In addition, this relationship supports the concept that vacuolated columnar cells of the crypts of Lieberkühn are the cell type that secretes Cl in response to PGE2.

Lectin binding and identification of sialic acid acceptor sugars in rabbit oviduct under hormone administration

Localization of individual glycosidic residues and sialic acid acceptor sugars was investigated by conjugated lectins in the rabbit oviduct under physiological hormonal conditions and human chorionic gonadotropin (HCG) administration. Ampulla and isthmus were found to exhibit lectin binding profiles typical of each hormonal stage. Two different sialylated glycomolecules were identified within the epithelial lining; in particular, sialoglycoconjugates characterized by the terminal sequence sialic acid-galactose were visualized in the secretory cells and the sialic acid-N-acetylgalactosamine terminal disaccharides were localized on both ciliated and secretory cells of the entire oviduct. Surface and cytoplasmic sialoglycoconjugates were also found to exhibit a differential behaviour inside the two oviduct tracts examined. Present findings further supported the idea that in ampulla and isthmus, the greatest modifications consequent to hormone treatment take place at different times.

Ultracytochemical evidence of Golgi functions in microvesicles at all phases of cell cycle in Saccharomyces cerevisiae

The topical question of Golgi compartment identity in the ascomycetous yeast Saccharomyces cerevisiae is illustrated by a multiple ultracytochemical approach. For this eucaryotic single-cell organism the established scheme of secretory transport via a cascade of cisternae housing different functions of Golgi apparatus has been deduced principally of genetic and molecular analyses ex situ and confirms the mammalian secretion scheme. Nevertheless, ultracytochemical in situ localizations of enzyme activities engaged in secretion represented evidence for localization of important steps of secretory glycoprotein maturation in two morphologically distinct populations of transport microvesicles formed from endoplasmic reticulum and Golgi cisternae. Both types of microvesicles function in exocytosis or transport into lysosomal vacuoles and have identical charge. However, their presence differs in interphase and in budding cells of S. cerevisiae. Smooth, larger membrane bound microvesicles are conspicuous at the onset of budding and at construction of scars, while the coated, smaller microvesicles of globular ultrastructure are present constitutively, throughout the cell cycle. Because the established model of the yeast secretory path considers only the part of the budding phase preceding the onset of mitosis, an alternative scheme for the cellular mechanism of glycoprotein secretion in S. cerevisiae that distinguishes interphase and budding yeast, has been established. The lumen of microvesicles contains proteases catalysing maturation of the mating pheromone alpha-factor (yscIV, yscF), vacuolar protease yscY, alkaline phosphohydrolase, polyphosphorylated components of the bud scar and glycoproteins. The in situ approach also reveals a minimum level of alpha-factor precursor processing proteolytic activity at the budding phase of cells, a transient presence of polyphosphorylated compounds in the bud scars and their transport by microvesicles. Ultracytochemical reactions suggest that the nuclear envelope lumen houses certain functions attributed to endoplasmic reticulum and that some steps of outer-chain glycosylation may occur in microvesicles. Microvesicles which contain proteases and polyphosphorylated intermediates also appear in juvenile vacuoles (lysosomes). Ultracytochemical findings show the Golgi compartment of S. cerevisiae to consist not only of discrete endoplasmic cisternae, immunodetected by others as sites of outer chain alpha-1,6-mannosylation and of the Golgi membrane marker proteins Sec7p and Ypt1p, but also of microvesicles moving either to the cell plasma membrane or to vacuoles. The previously hypothesized hierarchy of segregated yeast Golgi cisternae was not revealed by ultracytochemical findings.(ABSTRACT TRUNCATED AT 400 WORDS)

Glycoconjugates of the normal human colorectum: a lectin histochemical study

Previous studies of the normal human colorectum by lectin histochemistry have used a mixture of tissues, including those derived from colons harbouring neoplasia and inflammatory bowel diseases. In the current investigation, tissues from patients without either of these conditions have been examined with a wide panel of lectins, encompassing specificities directed against both N- and O-linked sequences, using an avidin peroxidase revealing system and evaluated with a semiquantitative scoring method. The results of binding of these lectins have been compared with those seen in the resection margins of (at least 5 cm away from) colorectal carcinomas. Consistent regional variations were noted between right- and left-sided colonic tissues, with more diverse glycan structures and a greater sialyl content in the distal colon. There was evidence of graduation of formation of oligosaccharide chains in developing crypts, possibly related to the maturation and expression of glycosyl transferases responsible for the incorporation of mannose residues of N-linked oligosaccharides and of N-acetylgalactosamine and N-acetylglucosamine. Comparison with previous reports has revealed some variations, possibly related to tissue fixation and processing and to lectin concentrations employed, which raises the question of standardization of methodologies in lectin histochemical investigations.

Changes of lectin staining pattern of the Golgi stack during differentiation of the ameloblast in developing rat molar tooth germs

Changes of lectin staining patterns in the Golgi stack during cell differentiation were examined in the ameloblasts of developing rat molar tooth germs, using HRP-labeled lectins: Canavalia ensiformis (Con A), Griffonia simplicifolia I (GS-I), Glycine max (SBA), Ulex europeus I (UEA-I), Triticum vulgaris (WGA), and Arachis hypogaea (PNA). The Golgi stacks of the inner enamel epithelial cells and the presecretory ameloblasts were stained with the lectins, although the staining strength and pattern varied among the stacks with each lectin. In some cases, the reaction products for the lectins were observed in most or all saccules of the Golgi stack. In the secretory ameloblasts, however, discrete staining patterns of the Golgi stack were found for each lectin. The reaction products deposited in definite saccules of the Golgi stack of the secretory ameloblast, especially for UEA-I and PNA which stained only the trans Golgi saccules of the stack. The reaction-positive saccules distributed more extensively in the Golgi stack of the inner enamel epithelial cell and the presecretory ameloblast than in the secretory ameloblast. These findings suggest that the Golgi stack is not fully compartmentalized in the inner enamel epithelial cell and the presecretory ameloblast. It is proposed that, in the differentiating ameloblast, various glycosyltransferases may coexist in most saccules of the Golgi stack.

Ultrastructural distribution of lectin-binding sites on gastric superficial mucus-secreting epithelial cells. The role of Golgi apparatus in the initial glycosylation

Normal human gastric epithelial cells were examined by electron microscopy using each of five biotinylated lectins [Ulex europaeus agglutinin I (UEA-I), peanut agglutinin (PNA), wheat germ agglutinin (WGA), soybean agglutinin (SBA) and Dolichos biflorus agglutinin (DBA)] as a probe. We employed 35 gastric surgical specimens removed from complicated peptic disease. The lectin-binding sites were revealed with streptavidin-colloidal gold complex. All specimens were embedded in Spurr and LR White resins. In superficial foveolar epithelial cells, the lectins used were generally positive in all cell types (mainly UEA-1 and PNA) on the Golgi region and mucus cytoplasmic vacuoles, with many variations among cells in the same case. On the other hand, extracellular mucus was negative for WGA. Labelling with PNA revealed a biphasic pattern (peripheral positivity) on mucous droplets in surface and foveolar cells. The cis side of the Golgi apparatus was labelled with SBA and PNA and rough endoplasmic reticulum with SBA (only five cases). Lectin-binding variability could be related to heterogeneous composition of gastric mucus. Our results with SBA suggest initiation of O-glycosylation at the Golgi apparatus; however a role of the rough endoplasmic reticulum cannot be excluded (N-glycosylation). We propose the following sequence of sugar addition to the carbohydrate side-chains of gastric glycoproteins: (1) GaNAc (Golgi apparatus cis-side), (2) GlcNAc (Golgi apparatus intermediate face), (3) GalNac or Gal, alpha-L-fucose (Golgi apparatus trans-side).

Secretion of K and Cl across colonic epithelium: cellular localization using electron microprobe analysis

Electron microprobe analysis of quick-frozen distal colonic epithelium from guinea pig was used to locate the cells responding to secretory stimuli. Concentrations of Na, K, and Cl were similar for cells of surface and crypt in the unstimulated state, 8, 149, and 46 mmol/kg wet weight, respectively. Stimulation of either K and Cl secretion with prostaglandin E2 or K secretion alone with epinephrine increased Na to approximately 12 mmol/kg wet weight in crypt cells but not in surface cells or cells in the crypt neck. This result supports the location of ion secretory cells in the lower two-thirds of the crypt. In the vacuoles of crypt columnar cells, stimulation of KCl secretion decreased K, S, Mg, and Ca and increased Na and Cl, indicative of the concomitant release of vacuole contents. Mucin granules in crypt goblet cells contained more S and Mg than granules in surface goblet cells. These findings support the concept of differentiation in ion and macromolecular secretory function along the axis from crypt to surface epithelium.

Influence of sulphate groups in the binding of peanut agglutinin. Histochemical demonstration with light- and electron-microscopy

The influence of sulphation of mucus glycoproteins in the binding of peanut agglutinin (PNA) to tissue sections has been investigated by means of histochemical techniques at the light- and electron-microscopic level. A sequential methylation-saponification procedure was applied for the desulphation of tissue samples. Labelling by peroxidase- and colloidal gold-conjugated PNA was compared in control and desulphated samples of rat intestinal mucosa. The high-iron-diamine (HID) technique was used as a control for the effectiveness of the desulphation technique, and the Alcian Blue, pH 2.5 (AB 2.5), PAS and phosphotungstic acid-HCl (acid-PTA) techniques served as controls for the integrity of the oligosaccharide chains, respectively. In general, a marked increase of PNA reactivity was observed in desulphated samples when compared with control sections. These findings indicate that sulphation of galactose inhibits the binding of PNA to carbohydrate moieties in tissue sections. Staining patterns obtained with HID, PNA and the desulphation-PNA sequence in the goblet cells of the large intestine suggest a modification of the secretory product stored in these cells as the cell matures and moves from the lower crypt region toward the luminal surface. These modifications were not detected in the small intestine. Ultrastructural detection of PNA-binding sites suggests that galactose residues are incorporated into the oligosaccharide chains of O-linked glycoproteins at the medial cisternae of the Golgi apparatus. However, sulphation occurs at the trans side of the Golgi complex and the trans Golgi network. In conclusion, desulphation procedures are useful for revealing PNA-binding sites.

Cellular localization of PNA binding in colorectal adenomas: comparison with differentiation, nuclear:cell height ratio and effect of desialylation

The lectin Arachis Hypogaea (Peanut Agglutinin, PNA) was used to study the cellular localization of the Thomsen-Friedenreich (T) disaccharide Gal-beta (1-3)-GalNAc alpha 1-R in 22 formalin-fixed paraplast-embedded colorectal adenomas of varying cellular dysplasia. An indirect immunoperoxidase method was used prior to and after neuraminidase treatment. Detailed information on the cellular localization of PNA binding was obtained. In addition, morphometric measurements of the nuclear: cell height ratios were performed on staining-filtered micrographs of crypts from all adenomas. We found 1) a statistically significant increase in the nuclear:cell height ratio with increasing grade of dedifferentiation (p less than 0.003), 2) a statistically significant smaller nuclear:cell height ratio in crypts that were PNA-positive in the Golgi region when these were compared to crypts that were PNA-positive on luminal cell membranes, 3) a decreasing number of crypts expressing PNA binding sites in the Golgi region with increasing dedifferentiation, leading to complete absence of PNA binding sites in Grade IV adenomas, 4) neuraminidase pretreatment increased the number of crypts expressing PNA binding sites in cytoplasm and on luminal membranes, whereas no changes were detected in crypts expressing PNA binding sites in the Golgi region. Our results confirm the general concept of accumulation of precursors of carbohydrate antigens in dedifferentiated cells. On the basis of the results presented, we conclude that the nuclear:cell height ratio shows a good correlation with the cellular localization of PNA binding, cellular differentiation and classic pathologic grading.

Subcompartment sugar residues of gastric surface mucous cells studied with labeled lectins

We examined the intracellular localization of sugar residues of the rat gastric surface mucous cells in relation to the functional polarity of the cell organellae using preembedding method with several lectins. In the surface mucous cells, the nuclear envelope and rough endoplasmic reticulum (rER) and cis cisternae of the Golgi stacks were intensely stained with Maclura pomifera (MPA), which is specific to alpha-Gal and GalNAc residues. In the Golgi apparatus, one or two cis side cisternae were stained with MPA and Dolichos biflorus (DBA) which is specific to terminal alpha-N-acetylgalactosamine residues, while the intermediate lamellae were intensely labeled with Arachis hypogaea (PNA) which is specific to Gal beta 1,3 GalNAc. Cisternae of the trans Golgi region were also stained with MPA, Ricinus communis I (RCA I) which is specific to beta-Gal and Limax flavus (LFA) which is specific to alpha-NeuAc. Immature mucous granules which are contiguous with the trans Golgi lamellae were weakly stained with RCA I, while LFA stained both immature and mature granules. The differences between each lectin's reactivity in the rough endoplasmic reticulum, in each compartment of the Golgi lamellae and in the secretory granules suggest that there are compositional and structural differences between the glycoconjugates in the respective cell organellae, reflecting the various processes of glycosylation in the gastric surface mucous cells.

Cytochemical characteristics of the Golgi apparatus

Lectinocytochemistry provides a useful tool for localizing subcompartments of the complex reticular apparatus of Golgi. The technique is based on interactions of lectins with glycoconjugates present in the limiting membranes and luminal spaces of Golgi elements. Application of a series of lectins of different sugar specificities permits a differentiation between Golgi subcompartments containing glycoconjugates with different oligosaccharide side chains. These may be a) differnet glycoconjugates or b) glycoconjugates at different stages during synthesis or repair of their glycans. The lectinocytochemical studies with mannose-, glucose-, N-acetyl-glucosamine-, N-acetyl-galactosamine-, galactose-, fucose-, and sialic acid-recognizing lectins revealed predominating patterns that labeled distinct, i.e., cis, medial, trans, and transmost, regions of the Golgi apparatus. A further refinement could be achieved by differential lectin-inhibition that enables a dissection of lectin binding reactions on the basis of their binding affinities. High-affinity binding reactions showed that subcompartments are not necessarily confined to one single Golgi subregion and may change their position from one to another subregion. Some of the patterns observed may be interpreted in relation to certain steps during synthesis and modifications of glycans.

Ontogenic expression of histo-blood group antigens in the intestines of suckling pigs: lectin histochemical and immunohistochemical analysis

The expression of intestinal histo-blood group AO and related antigens was investigated in piglets during an 8 week suckling period. Lectin histochemical and immunohistochemical analyses were undertaken on sections of resin-embedded intestinal tissue and semi-quantitative scoring systems were adopted for categories of lectins and monoclonal antibodies reactive with carbohydrate moieties present in core, backbone and terminal oligosaccharide sequences of histo-blood group antigens. Distinct age-related changes were observed in the terminal glycosylation of both secretory and membrane glycoconjugates. Histo-blood group A antigen was identified in intestinal mucin 5 weeks after birth and the precursor H antigen was found in goblet cells at week 1. H antigen was undetectable on intestinal membranes during the first 3 weeks of suckling but a conspicuous and sustained level of this form of fucosylation was apparent during the latter half of the suckling period. More complex membrane glycosylation involving further fucosylation and/or the expression of A antigen, was evident in the latter part of the suckling period. These temporal changes in membrane and secretory glycosylation may be physiologically important during intestinal adaptation and development in young pigs.

Mucin histochemistry and lectin binding sites in intestinal metaplasia of the urinary bladder

We report a case of intestinal metaplasia of the bladder urothelium associated with dysplastic foci and a transitional cell carcinoma. A mixture of sialomucins, O-acetylated sialomucins and sulphomucins was found in the goblet cells. Neuraminidase resistant binding of the lectin peanut agglutinin was demonstrated in the brush border of columnar cells in intestinal metaplasia and diffusely in columnar cells in dysplastic foci. The histochemical findings are compared with those described in normal, dysplastic and neoplastic colonic mucosa.

Changes in lectin-binding pattern in the digestive tract of Xenopus laevis during metamorphosis. I. Gastric region

The distribution of structural and secretory glycoconjugates in the gastric region of metamorphosing Xenopus laevis was studied by the avidin-biotin-peroxidase (ABC) histochemical staining method using seven lectins (concanavalin A, Con A; Dolichos biflorus agglutinin, DBA; peanut agglutinin, PNA; Ricinus communis agglutinin I, RCA-I; soybean agglutinin, SBA; Ulex europeus agglutinin I, UEA-I; and wheat germ agglutinin, WGA). Throughout the larval period to stage 60, the epithelium consisting of surface cells and gland cells was stained in various patterns with all lectins examined, whereas the thin layer of connective tissue was positive only for RCA-I. At the beginning of metamorphic climax, the connective tissue became stained with Con A, SBA, and WGA, and its staining pattern varied with different lectins. The region just beneath the surface cells was strongly stained only with RCA-I. With the progression of development, both the epithelium and the connective tissue gradually changed their staining patterns. The surface cells, the gland cells, and the connective tissue conspicuously changed their staining patterns, respectively, for Con A and WGA; for Con A, PNA, RCA-I, SBA, and WGA; and for Con A, RCA-I, and WGA. At the completion of metamorphosis (stage 66), mucous neck cells became clearly identifiable in the epithelium, and their cytoplasm was strongly stained with DBA, PNA, RCA-I, and SBA. These results indicate that lectin histochemistry can provide good criteria for distinguishing among three epithelial cell types, namely, surface cells, gland cells, and mucous neck cells, and between adult and larval cells of each type.

Isolation and characterization of gastric microsomal glycoproteins. Evidence for a glycosylated beta-subunit of the H+/K(+)-ATPase

Detergent-solubilization of hog gastric microsomal membrane proteins followed by affinity chromatography using wheat germ agglutinin or Ricinus communis I agglutinin resulted in the isolation of five glycoproteins with the apparent molecular masses on sodium dodecyl sulfate polyacrylamide gels of (in kDa): 60-80 (two glycoproteins sharing this molecular mass); 125-150; and 190-210. In the nonionic detergent Nonidet P-40 (NP-40), the 94 kDa H+/K(+)-ATPase was recovered exclusively in the lectin-binding fraction; however, in the cationic detergent dodecyltrimethylammonium bromide, most of the ATPase was recovered in the nonbinding fraction. Detection of glycoproteins either by periodic acid-dansyl hydrazine staining of carbohydrate in polyacrylamide gels or by Western blots probed with lectins indicated that the majority of the ATPase molecules are not glycosylated. In addition, in the absence of microsomal glycoproteins, the NP-40-solubilized ATPase does not bind to a lectin column. Taken together, these results suggest that the recovery of NP-40-solubilized ATPase in the lectin-binding fraction is due to its noncovalent interaction with a gastric microsomal glycoprotein. Immunoprecipitation of the ATPase from NP-40-solubilized microsomal membrane proteins resulted in the co-precipitation of a single 60-80 kDa glycoprotein. Characterization of the 60-80 kDa glycoprotein associated with the ATPase revealed that: it is a transmembrane protein; it has an apparent core molecular mass of 32 kDa; and, it has five asparagine-linked oligosaccharide chains. Given its similarity to the glycosylated beta-subunit of the Na+/K(+)-ATPase, this 60-80 kDa gastric microsomal glycoprotein is suggested to be a beta-subunit of the H+/K(+)-ATPase.

The use of lectins in histopathology

Lectins are proteins and glycoproteins extracted predominantly from plants which have the capacity to bind sugars specifically. This property makes them of interest for histopathology since they will bind to saccharides forming parts of glycoproteins and glycolipids of tissue constituents. Lectins have and can be used as reagents for mucin histochemistry, to identify specific cells, in the recognition of glycoprotein alterations in disease states, in studies of infectious diseases, and in the assessment of glycoconjugate alterations occurring with malignancy. They can be used for both light microscopic and ultrastructural localisation and various methods are available. It is important though, to consider the nature of the glycoconjugates under study and select lectins appropriately because of their varying specificities and binding characteristics. A panel of lectins should be used to study a particular configuration. Care should be taken with tissue fixation and processing. It must be remembered that an open and critical mind should be kept concerning interpretation of results. At the present time lectins have a limited value diagnostically, but the binding of Ulex europeus agglutinin to endothelium is certainly of value.

Cycle- and function-related changes in lectin binding to human endometrium: a histochemical study with pronase treatment

Forty-eight endometrial biopsy specimens were obtained during a normal menstrual cycle, during pregnancy and from patients with dysfunctional bleeding. The specimens were examined for Peanut (PNA), Soybean (SBA), Vicia villosa (VVA), Phytohem- (PHA), Lens culinaris (LCA) and Concanavalin (succ. Con A) agglutinin binding. The study was performed on paraffin sections using the pronase digestion and either the peroxidase-antiperoxidase or the avidin-biotin-peroxidase method. Cycle-related changes of the PNA, SBA, VVA, and to some degree PHA binding, were based on the transfer of the cytoplasmic reaction toward the glandular lumena. PNA + and SBA + material moved to the cell surface at the transition of the follicular and luteal phase and before the basal vacuolization appeared. Functional disturbances mainly influenced the intensity of the reaction. It was true only for those lectins, whose binding pattern showed cycle-related changes. In curettings from patients with a prolonged menstrual cycle the lectin binding seen in normal late secretory endometrium was absent or significantly diminished. Lectin binding to the endometrial surface epithelium was variable; PHA was the only lectin, the binding pattern of which followed cyclic changes in the glycocalyx, detected previously by means of PAS and alcian blue methods.

O-glycosylation pathway for mucin-type glycoproteins

O-glycosylation is the post-translational process whereby carbohydrate is added to hydroxylated amino acids of proteins. The major O-glycosylation pathway in animal cells is involved in the synthesis of oligosaccharides linked by N-acetylgalactosamine to serine or threonine residues in 'mucin-type' proteins or their analogs. In this review, we discuss the evidence for the cellular localization of the biosynthetic steps in this pathway and propose a simplified, consensus version. We also propose variations of the simple pathway to account for its heterogeneity and variability in different cell types and differentiation states.

Lectin binding patterns in normal and neoplastic colonic mucosa. A study of Dolichos biflorus agglutinin, peanut agglutinin, and wheat germ agglutinin

The cellular distribution of the carbohydrates labeled by Dolichos bifluorus agglutinin (DBA), peanut agglutinin (PNA), and wheat germ agglutinin (WGA) were studied in 21 normal colonic mucosae, 17 transitional mucosae, 9 nonneoplastic polyps (NNP), 27 adenomas, and 25 colorectal carcinomas. In normal mucosa DBA bound selectively to mucin of the goblet cells in the upper colonic crypt and to apical cytoplasm of the superficial columnar cells with a strong linear pattern. PNA binding was present only in the supranuclear portion (Golgi area) of the cells. WGA showed a strong reactivity in the goblet-cell mucin and in the supranuclear portion and apical cytoplasm of columnar cells. Transitional mucosa (TM) showed a decrease in DBA binding to goblet-cell mucin, which was replaced by an increase in PNA reactivity. The DBA linear pattern in the apical cytoplasm of columnar cells was unmodified, however. Changes similar to those of TM were observed in juvenile and Peutz-Jeghers polyps. Adenomas showed a progressive loss of DBA reactivity and an increase in PNA positivity related to the degree of dysplasia. This change was more evident in the linear pattern of apical cytoplasm. Only 32% of the carcinomas reacted with DBA and those were mucinous and well-differentiated adenocarcinomas. WGA was positive in all carcinomas with a different pattern than in normal mucosa. These findings suggest that the different lectin-binding patterns in normal and neoplastic colonic mucosa are related to the degree of cellular differentiation. In the process of malignant transformation the carbohydrate distribution undergoes progressive changes through the adenoma-carcinoma sequence. These changes are related to the degree of dysplasia in adenomas and to the degree of differentiation in carcinomas.

Distribution of lectin-binding sites in oxyntic and chief cells of isolated rabbit gastric glands

The distribution of lectin-binding sites in oxyntic and chief cells of isolated rabbit gastric glands was determined with seven fluoresceinated lectins, to ascertain which lectins might best be used in the biochemical characterization of cell membranes and glycoproteins of these two cell types. Oxyntic cell canaliculi were labeled by wheat germ, Helix pomatia, and peanut lectins, suggesting a predominance of N-acetylhexosamines. Tubulovesicles were heavily stained by wheat germ, Helix pomatia, and Ricinus communis I lectins, indicative of N-acetylhexosamine- and galactose-containing glycoconjugates. Diffuse oxyntic cell cytoplasmic staining was observed with the mannose-binding lectin concanavalin A. This lectin, along with wheat germ, soybean, Helix pomatia, and Ricinus communis I lectins, bound to oxyntic cell basolateral membranes, indicating mannose, N-acetylhexosamine, and galactose residues. Chief cell apical membranes were labeled with peanut, Ricinus communis I, Helix pomatia, and Ulex europaeus lectins, suggesting a predominance of N-acetylhexosamine, galactose, and fucose residues. None of the lectins demonstrated any significant affinity for chief cell cytoplasm or basolateral membrane. Ulex europaeus agglutinin-binding sites were additionally concentrated in lateral intercellular spaces. The results of this study indicate that the range of utility of isolated rabbit gastric glands can be expanded to include histochemical work. In addition, the data suggest the applicability of lectin affinity chromatography in the isolation and characterization of oxyntic and chief cell membranes and glycoproteins.

Changes in the lectin-binding pattern of PNA-agglutinin and UEA1 during the DMH-induced carcinogenesis in the normal appearing colonic mucosa of the rat

The purpose of this study was the investigation of changes in the lectin-binding pattern prior to tumour formation in an experimental model. Female Wistar rats were treated with 1,2-dimethylhydrazine (DMH). After 4, 8, 16, 24, 32 and 40 weeks of treatment the lectin-binding-pattern of the colonic mucosa appearing morphologically normal was examined at the caecum, proximal colon, distal colon and rectum, using FITC-conjugated Peanut-agglutinin (PNA) and Ulex europaeus-agglutinin1 (UEA1). In contradistinction to what has been reported earlier by other authors, PNA did not indicate constant cancer-associated mucin changes. In addition, there was no difference in the UEA1-binding between the control animals and the DMH-treated rats. Thus, in the rat there is no specific PNA- and UEA1-binding pattern during tumour induction in the gut.

Ultrastructural demonstration of lectin binding sites in the Golgi apparatus of rat epiphyseal chondrocytes

Binding sites for wheat germ agglutinin (WGA), Dolichos biflorus agglutinin (DBA), Ricinus communis I agglutinin (RCA I) and Limax flavus agglutinin (LFA) have been ultrastructurally detected in rat epiphyseal chondrocytes by a post-embedding cytochemical technique using colloidal gold as marker. The four lectins labelled exclusively the Golgi apparatus of chondrocytes embedded in Lowicryl K4M resin by two different methods. WGA binding sites were localized in medial and trans cisternae as well as in immature secretory vesicles, whereas those for DBA were seen concentrated in cis and medial cisternae. Labelling with both RCA I and LFA lectins was distributed throughout all the cisternae of the Golgi stack, and the latter also in vesicles and tubules at the trans face. Neuraminidase pretreatment of the sections abolished LFA staining, decreased reaction with WGA and increased that with RCA I, while it did not affect DBA staining. After chondroitinase ABC treatment only the RCA I reaction was modified, revealing new binding sites in the trans Golgi face, secretory granules and extracellular matrix. These results indicate that the distribution of subcompartments in the Golgi apparatus of chondrocytes is different from that in cells secreting glycoproteins as major products.

Distribution and changes of glycoconjugates in rat colonic mucosa during development. A histochemical study using lectins

A study was made of the modifications of glycoconjugates in rat colonic mucosa during development. Sections of the caecum, and proximal and distal portions of the colon from Sprague Dawley rats at different stages of development (embryos, fetuses, suckling, weaning and adult rats) were examined. The sections were incubated with a battery of eight fluoresceinated lectins: DBA, SBA, WGA, LFA, PNA, GS-I, UEA-I and Con A. Some sections were treated with neuraminidase, and others were submitted to sequential saponification-neuraminidase treatment prior to incubation with the lectin (WGA, PNA or LFA). The intensity of the fluorescence was evaluated and graded from absent (-) to very positive (4+). Gradual and progressive changes were seen in colonic glycoconjugates during development. These changes revealed a unique developmental pattern for each lectin, which was independent for each cellular compartment (goblet cells, luminal surface and supranuclear region). Local and regional differences, observed between the different colonic sections, were already present from early stages of development. Moreover, our study showed that for several glycoconjugates, the differentiation process in colonic mucosa began in the distal region and continued through to the proximal region, the former being the first to reach the adult pattern. In the caecum, some lectins maintained a fetal pattern throughout all the periods of development up to the adult stage.

Lectin binding patterns in developing rat colon

To evaluate qualitative changes in brush-border and goblet cell glycoconjugates during colonic development, rhodamine-conjugated lectins were applied to tissue from fetal (18-22 day), suckling (1-20 day), and weanling (22-26 day) rats. Tissue from the proximal and distal colon of each animal was incubated with Triticum vulgaris, Arachis hypogaea, Glycine max, or Ulex europeus agglutinin I. Formalin-fixed paraffin sections and unfixed frozen sections were coded, read blindly, and graded from negative (-) or weak (+) to intensely positive (4+). The results showed a unique developmental pattern for each lectin, although in all cases the adult binding pattern was established by weaning. Alterations in the binding pattern between paraffin and frozen sections were noted only for Arachis hypogaea and Glycine max. Minimal Glycine max binding was seen at any age in paraffin sections, although in frozen sections a weak but consistent supranuclear binding was seen in goblet cells of postnatal animals. In contrast, both the brush-border and goblet cells were intensely fluorescent after exposure to Triticum vulgaris. This fluorescence was present in both regions at all ages studied. Ulex europeus agglutinin I also labeled goblet cells in the fetal and neonatal colon, but late in the suckling period regional differences appeared. This resulted in a significant loss of labeled goblet cells distally and a restriction of Ulex europeus agglutinin I-positive cells to the base of the crypts proximally. Finally, Arachis hypogaea showed a transient brush-border binding in paraffin sections of the proximal colon before weaning, whereas frozen sections revealed a supranuclear localization in goblet cells in both regions after birth. These studies indicate significant changes in membrane-associated and goblet cell secretory glycoconjugates in the developing rat colon.

The Golgi apparatus in the acinar cells of the developing embryonic pancreas: II. Localization of lectin-binding sites

The reaction patterns of the Golgi apparatus following staining with the lectins concanavalin A (ConA), Ricinus communis I agglutinin (RCA I), and Helix pomatia lectin (HPA) were studied in the pancreas acinar cells of rat embryos in the course of cell differentiation from day 13 through day 20 of gestation. The binding reactions were localized by means of pre-embedment incubation of 10-microns-thick cryosections of pancreas tissue, prefixed in a mixture of 4% formaldehyde/0.5% glutaraldehyde, using horseradish peroxidase for electron microscope visualization. ConA, which preferentially binds to alpha-D-mannosyl residues, consistently stained the cisternae of the cis Golgi side. The majority of the stacks also showed ConA staining of medial cisternae. The reaction of the trans side was variable; in each stage of development, the cisternae of the trans Golgi side either were devoid of labeling or appeared intensely stained. The reactions obtained with RCA I, which recognizes terminal beta-D-galactosyl residues, changed in the course of cell differentiation; in the protodifferentiated and early differentiated states, the system of "rigid lamellae," located at the trans side of the Golgi stacks, was intensely labeled, but became unreactive after production of secretion granules had started, the reaction then being restricted to the stacked saccules. In regard to the Golgi stacks in each of the developmental stages, RCA I binding sites either were confined to the trans cisternae, or, in addition, were found distributed across elements of the medial and cis compartments.(ABSTRACT TRUNCATED AT 250 WORDS)

Histochemical evaluation of glycoconjugates in the male reproductive tract with lectin-horseradish peroxidase conjugates: I. Staining of principal cells and spermatozoa in the mouse

Several glycoconjugates are thought to bind spermatozoa as they pass through reproductive ducts. Paraffin sections of testis, ductuli efferentes, epididymis, and vas deferens of male mice were stained with ten different lectin-horseradish peroxidase conjugates to localize possible sites of synthesis and secretion of such glycoconjugates, based on the carbohydrate moieties in their constituent oligosaccharide side chains. Principal (columnar) cells lining the efferent ducts, germinal epithelium, and developing and maturing spermatozoa were examined with light microscopy. Staining of the Golgi and apical zones of cells was interpreted as evidence for synthesis and secretion of glycoconjugates. Principal cells synthesized and secreted glycoconjugates with sugar moieties as follows: sialic acid, all regions of the efferent ducts examined; the terminal disaccharide D-galactose- (beta 1----3) -N-acetyl-D-galactosamine, all regions of ducts except epididymis I; terminal alpha-D-galactosamine, some cells in epididymis III-V; N-acetyl-D-galactosamine, ductuli efferentes, epididymis I, II, and some cells in epididymis III-V; alpha-L-fucose, ductuli efferentes, vas deferens, and all regions of the epididymis except IV; N-glycosidic side chains, ductuli efferentes, vas deferens, and epididymis I, IV, and V. All of these sugar residues as well as N-acetyl-D-glucosamine were associated with the acrosomes and tails of spermatozoa throughout the ducts except for alpha-N-acetyl-D-galactosamine in epididymis I, and all occurred during one or more stages of spermiogenesis. The synthesis and secretion of glycoconjugates that bind to spermatozoa appear to involve more regions of the primary reproductive structures than was believed previously.

Differential binding sites of peroxidase-labelled lectins in the submandibular gland of sucking and adult cats

The glycosidic residues in the submandibular gland of cat at different ages were studied using a battery of 6 lectins conjugated with horseradish peroxidase as histochemical reagents. The submandibular glands of sucking and adult cats showed diversities in the reaction intensity or in the localization of binding sites. The morphologically distinct secretory tracts appear to produce different types of oligosaccharides in sucking and adult subjects. The sugars that can be defined as growth markers in the cat submandibular gland seem to be alpha-L-fucose, N-acetyl-D-glycosamine and beta-galactose. The data originated from this research have been compared with biochemical data previously obtained by the authors on the cat submandibular gland during growth.

Evidence for glycoconjugate in nociceptive primary sensory neurons and its origin from the Golgi complex

Glycoconjugates with terminal galactose residues were localized in rat spinal cord and spinal ganglia using lectin-HRP conjugates of Griffonia simplicifolia and Glycine max agglutinins. Alternate staining of serial sections with HRP-labelled lectins and an antibody for substance P (SP) showed staining in identical primary sensory neurons with both methods. Similarly, lectin-reactive as well as SP-positive fibers were found in Rexed laminae I and II, Lissauer's tract, the spinal nucleus and tract of the trigeminal nerve, the nucleus commissuralis and a small bundle of fibers just ventral to the central canal. Administration of capsaicin to neonatal rats produced a significant decrease in lectin-reactive fibers of the substantia gelatinosa, and in the number of lectin-reactive sensory neurons. The coexistence of SP with galactose-containing glycoconjugates in spinal ganglion neurons, as well as sensitivity of these cells to capsaicin, provided a basis for classifying the reactive neurons as nociceptive in type. Ligation of dorsal roots resulted in disappearance of lectin reactivity in the spinal cord and caused accumulation of lectin-positive material proximal to the ligature, indicating somatofugal transport of galactose-containing glycoconjugates. Colchicine injection caused an increase in SP reactivity in dorsal ganglion neurons but no change in lectin staining of galactoconjugate. At the ultrastructural level affinity for the lectin conjugates was confined to the Golgi cisternae and the plasmalemma of B-type sensory neurons in the dorsal ganglion. The axolemma of unmyelinated processes stained selectively in dorsal roots and the substantia gelatinosa of the spinal cord. These findings provide evidence for the presence in certain sensory cells of a characteristic galactosylconjugate which may prove to be of significance in nerve function.

A post-embedding avidin-biotin peroxidase system to demonstrate the light and electron microscopic localization of lectin binding sites in rat kidney tubules

A post-embedding method for the light and electron microscopic demonstration of lectin binding sites in rat kidney tubules is described. The use of biotinylated lectins, followed by treatment with avidin peroxidase and the DAB-H2O2 sequence, produced intense staining of acrylic sections at the electron microscope level: brush borders and associated structures, cytoplasmic granules, basal infoldings and basement membrane-plasmalemmal interfaces of proximal tubules bound erythrophytohaemagglutinin, while distal tubules were mainly unstained. At the light microscope level, epoxy resin sections showed a similar staining pattern after etching, as did acrylic resin sections after intensification of the final reaction product. The binding of wheatgerm agglutinin to cytoplasmic granules and brush border structures in the proximal tubules was abolished, at both the light and electron microscope levels, by the competing sugar tri-N-acetylchitotriose. Epoxy resin ultrathin sections required etching before staining was achieved in the electron microscope, and results were far inferior to those obtained with acrylic resin. This method allows rapid and inexpensive screening of large numbers of lectins, if required, at both the light and electron microscope levels, using reagents that are stable for long periods of time.

Terminal glycosylation in rat hepatic Golgi fractions: heterogeneous locations for sialic acid and galactose acceptors and their transferases

Endogenous acceptors for N-acetylglucosamine (GlcNAc), galactose (Gal) or sialic acid (NeuAc) transfer were labeled to high activities when purified hepatic Golgi fractions were incubated with the corresponding radiolabeled nucleotide sugar in the absence of detergent. The in vitro conditions which were optimal for the endogenous glycosylation of GlcNAc and Gal acceptors (Mn2+, ATP) also promoted fusion within a subset of Golgi membranes. Electron microscope radioautography revealed that the majority of NeuAc acceptors were associated with unfused Golgi membranes, whereas the majority of Gal acceptors were localized to fused membranes. GlcNAc acceptors were approximately equally distributed between fused and unfused membranes. Under conditions in which Golgi membrane fusion was absent (-Mn2+), only NeuAc transfer was active. The majority of endogenous NeuAc acceptors were consequently assigned to the more trans regions of the hepatic Golgi apparatus as concluded from a combination of radioautography (NeuAc transfer) and acid NADPase cytochemistry (reactive medial and trans Golgi saccules). The distribution of NeuAc and Gal transferases was assessed after Percoll gradient centrifugation of disrupted Golgi fractions. The median density of NeuAc transferase was lower than that of Gal transferase. The studies are indicative of distinct Golgi components harboring the majority of acceptors and enzymes for terminal glycosylation.

Binding of lectin-fluorescein conjugates to intracellular compartments of growth-plate chondrocytes in situ

In this study, lectin-binding techniques are applied to growth-plate cartilage to analyze the intracellular localization of lectin-binding glycoconjugates of chondrocytes in situ. The binding of ten fluorescein-conjugated lectins is analyzed on 1-micron-thick Epon-embedded, nondecalcified sections of growth plates from Yucatan swine. Comparisons are made to intracellular binding in chondrocytes of tracheal, articular, and auricular cartilage. Ear epithelium, tracheal epithelium, and kidney are used as positive control tissues for the specificity of lectin binding. Only the mannose-binding lectins had affinity for the RER and nuclear envelope. Eight lectins reacted within the Golgi complex with characteristic patterns which ranged from localized fine linear strands to extensive vesicular accumulations. When cartilage slabs were exposed before embedment to the ionophore monensin to disrupt intracellular transport through the Golgi, it was possible to define differential subcompartments of the Golgi complex, based upon sites of sugar addition. Also, it was possible to characterize the cytoplasmic deposits of reserve-zone chondrocytes which were positive with concanavalin A as glycogen, based upon their sensitivity to amylase. This method allows resolution at the light-microscopic level of lectin-binding glycoconjugates with localization to specific organelles. Patterns of intracellular binding were consistent with biochemical data relating to the subcellular localization of processing steps of complex carbohydrates prior to secretion.

Post-embedding localization of glycoconjugates by means of lectins on thin sections of tissues embedded in LR white

A simple post-embedding technique for the electron microscopical detection of lectin-binding sites using thin sections of tissues embedded in the resin LR White is described. With this technique, no prior etching of the sections is necessary. The cellular fine structure is well preserved and permits close correlation of the labelling to distinct cellular compartments. After mild aldehyde fixation (4% formaldehyde and 0.5% glutaraldehyde for 30 min), enterocyte brush border, vesicles and lysosomes as well as goblet cell Golgi apparatus and mucin are intensely stained after 30-60 min. The hydrophilia and penetrability of LR White is shown by the formation of oxidized diaminobenzidine reaction product arising from horseradish peroxidase-conjugated lectins. The precipitate not only covers the surface of the sections but is also formed within the resin, as is revealed on cross-sections through thin and semithin sections. The addition of 0.2 M solutions of the appropriate inhibitory sugars prevented staining, which indicates a specific binding. Examples are given of the binding of gold-, ferritin- and peroxidase-conjugated lectins for the purpose of detecting glycoconjugates in various intracellular compartments.

Lectin-binding pattern in normal human gastric mucosa. A light and electron microscopic study

Normal human gastric mucosal cells were examined by light and electron microscopy using lectins as a probe. The ABC method was used with biotinylated lectins for light microscopy and HRP-labeled lectins for electron microscopy. The human gastric mucosal cells revealed specific binding patterns for each lectin by light microscopy. Among the lectins tested, in particular, DBA gave a characteristic pattern. It specifically stained the supranuclear region of surface epithelial cells and the perinuclear region of parietal cells. By electron microscopy, the stacked cisternae and the vesicles of the Golgi apparatus of the surface epithelial cells were positive for the DBA staining. These results show that the DBA-positive supranuclear region observed by light microscopy corresponds to the Golgi apparatus. In the parietal cells, DBA, RCA and ConA bound to the intracellular secretory canaliculi which are invaginations of the cell membrane running around the nucleus in the cytoplasm. Therefore, the tubular perinuclear positive region observed by light microscopy corresponds to the membranes of the intracellular secretory canaliculi. In addition, the ConA reagent stained the endoplasmic reticulum, Golgi apparatus, nuclear envelope, and cell membrane of the parietal cell, which explains the diffuse cytoplasmic staining observed at the light microscopic level with this lectin. Lectins have proved to be very useful for the evaluation of in situ cytochemical aspects of the glycoconjugates characteristic to human gastric mucosal cells.

Binding of lectins to goblet cell mucin in malignant and premalignant colonic epithelium in the CF-1 mouse

The lectin peanut agglutinin binds to mucin secreted by neoplastic but not normal human colonic epithelial cells. Peanut agglutinin was found to bind to mucin secreted by experimentally induced neoplasms in the distal colons of CF-1 mice, but not in the distal colons of control animals. Serial examination of colonic tissues after exposure to carcinogen has revealed the "cancer-associated" mucin in histologically normal but potentially premalignant epithelium. Thus, in the chemical carcinogen-rodent model, a diffuse alteration in glycoprotein structure is found in that part of the murine colon that subsequently develops cancer, and this precedes the appearance of neoplastic tissue. Changes in mucin structure may prove to be useful in the identification of premalignant gastrointestinal epithelium in certain humans at high risk for colon cancer.