Membrane-bound glycoconjugates of fetal mouse erythropoietic cells with special reference to phagocytosis by hepatic macrophages

Using lectin and colloidal iron (CI) stainings in combination with neuraminidase digestion, glycoconjugates on the surface of erythropoietic cells of the yolk sac and liver in fetal mice were examined. Fetal hepatic macrophages were capable of distinguishing between phagocytozed and non-phagocytozed erythroid elements as described in our previous study. Marked differences between these two elements could be ultrahistochemically detected on their cell surface. The phagocytozed elements, such as nuclei expelled from erythroblasts and degenerating primitive erythroblasts, faintly bound neuraminidase-sensitive CI, and neuraminidase digestion imparted a weak peanut agglutinin (PNA) binding. In contrast, erythroblasts at various maturation stages, erythrocytes and normal primitive erythroblasts heavily bound neuraminidase-sensitive CI, and neuraminidase digestion imparted a moderate PNA binding. No differences in binding of either concanavalin agglutinin,Ricinus communis agglutinin-I or PNA were noted between phagocytozed and non-phagocytozed erythroid elements. Desialylation appears to be one of the most important signs for the recognition mechanism of fetal macrophage phagocytosis. During maturation of hepatic erythroblasts, sialic acid changes its affinity forLimax flavus agglutinin from strong to weak, and soybean agglutinin binding sites disappear at the basophilic erythroblast stage. Glycoconjugates on polychromatophilic erythroblasts acquire similar compositions to those of erythrocytes.     

Receptors for thymosin alpha 1 on mouse thymocytes

Thymosin alpha 1 is able to act in vitro to stimulate T-cell precursors and to induce surface markers. The initial mechanism by which alpha 1 activates T cells could be the binding of alpha 1 to cell membranes. Using a specific anti-alpha 1 antibody and an indirect immunofluorescence procedure it was found that thymosin alpha 1 binds to the surface of a large portion of murine lymphocytes. Furthermore, thymocytes have been fractionated into immature and mature subpopulations by using the peanut agglutinin (PNA) technique. It was found that PNA+, immature cells showed specific receptors for alpha 1 on the cell membrane.     

AN ELECTRON MICROSCOPE STUDY OF THE EPITHELIUM IN THE NORMAL MATURE AND IMMATURE MOUSE CORNEA

1. An electron microscope study at high resolution of the corneal epithelium of the normal mature and immature mouse revealed new information regarding the submicroscopic appearance of these cells. 2. Two thin dense lines separated by a less dense area constituted the structure of the limiting surface membrane of epithelial cells; the thickness of this membrane was about 80 A. 3. Some differences in the appearance of the cytoplasm and mitochondria of cells from the immature mouse cornea and the appearance of the cytoplasm and mitochondria of cells from the adult mouse cornea were observed. 4. The basement membrane appeared as a dense band about 600 A wide separating the basal epithelial cells from the substantia propria. Suggestions of periodicity were seen in some phosphotungstic acid-treated specimens. 5. Round bodies believed to be bacteria were seen on the surface of the outer epithelial cells in the adult mouse cornea but not in the immature, unopened eye.     

Lectin binding in the anterior segment of the bovine eye

Summary Eleven different fluorescent lectin-conjugates were used to reveal the location of carbohydrate residues in frozen sections of the anterior segment of bovine eyes. The lectins were specific for the following five major carbohydrate groups: (1) glucose/mannose group (Concanavalin A (Con A)); (2)N-acetylglucosamine group (wheat germ agglutinin (WGA)); (3) galactose/N-acetylgalactosamine group (Dolichos biflorus agglutinin (DBA),Helix pomatia agglutinin (HPA),Helix aspersa agglutinin (HAA),Psophocarpus tetragonolobus agglutinin (PTA),Griffonia simplicifolia agglutinin-I-B₄ (GSA-I-B₄),Artocarpus integrifolia agglutinin (JAC), peanut agglutinin (PNA) andRicinus communis agglutinin (RCA-I)); (4)l-fucose group (Ukex europaeus agglutinin (UEA-I)); (5) sialic acid group (wheat germ agglutinin (WGA)). All the studied lectins except UEA-I reacted widely with different structures and the results suggest that there are distinct patterns of expression of carbohydrate residues in the anterior segment of the bovine eye. UEA-I bound only to epithelial structures. Some of the lectins reacted very intensely with apical cell surfaces of conjunctival and corneal epithelia suggesting a different glycosylation at the glycocalyx of the epithelia. Also, the binding patterns of conjunctival and corneal epithelia differed with some of the lectins: PNA and RCA-I did not bind at all, and GSA-I-B₄ bound only very weakly to the epithelium of the cornea, whereas they bound to the epithelium of the conjunctiva. In addition, HPA, HAA, PNA and WGA did not bind to the corneal basement membrane, but bound to the conjunctiva and vascular basement membranes. This suggests that corneal basement membrane is somehow different from other basement membranes. Lectins with the same carbohydrate specificity (DBA, HPA, HAA and PTA) reacted with the sections almost identically, but some differences were noticed: DBA did not bind to the basement membrane of the conjunctiva and the sclera and did bind to the basement membrane of the cornea, whereas other lectins with same carbohydrate specificities reacted vice versa. Also, the binding of PTA to the trabecular meshwork was negligible, whereas other lectins with the same carbohydrate specificities reacted with the trabecular meshwork. GSA-I-B₄ reacted avidly with the endothelium of blood vessels and did not bind to the stroma, so that it made blood vessels very prominent and it might be used as an endothelial marker. This lectin also reacted avidly with the corneal endothelium. Therefore, GSA-I-B₄ appears to be a specific marker in bovine tissues for both blood vessel and corneal endothelium cells.     

Identification of peanut agglutinin-binding glycoproteins on immature human thymocytes

Previous studies in our laboratory have shown that peanut agglutinin (PNA), a lectin specific for the disaccharide Gal beta 3GalNAc, binds to immature (cortical) thymocytes of mouse and man and not to the mature (medullary) cells. Using lectin overlay of protein blots and lectin-affinity chromatography, we have found that the major PNA-binding glycoproteins on total as well as on immature (PNA+) human thymocytes correspond to two bands of Mr 170,000 and 180,000. Another glycoprotein, of Mr 110,000, also binds PNA but to a lesser extent. All three glycoproteins contain sialic acid as demonstrated by cell surface labeling with NaIO4-NaB3H4, binding of wheat germ agglutinin, and reaction with alkaline phosphatase-hydrazide. After treatment with sialidase, binding of PNA to these glycoproteins is significantly enhanced.     

Cell differentiation of alveolar epithelium in the developing rat lung: ultrahistochemical studies of glycoconjugates on the epithelial cell surface

Glycoconjugates on the surface of pulmonary epithelial cells were ultrahistochemically examined in the fetal, neonatal and adult rat lung. Lectin and colloidal iron staining procedures were performed in combination with digestion using carbohydrate-degrading enzymes or methylation. The glycoconjugate composition of columnar cells at 16 days gestation was similar to that of cuboidal cells at 19 days gestation. Glycoconjugate differentiation on the cell surface occurred at 20 days gestation, and especially the loss of soybean agglutinin (SBA) binding sites could be detected on type II cells. The contents of Ricinus communis agglutinin-I (RCA-I) and Concanavalin A (Con A) binding sites on type II cells also began to decrease. On the contrary, the content of sulfated saccharides decreased on the surface of type I cells during development. Glycoconjugate differentiation on both type I and II cells was completed with the disappearance of hyaluronic acid and peanut agglutinin (PNA) binding sites; type I and II cells acquired a similar histochemical composition to that on adult type I and II cells at 5 days after birth. Both type I and II cells share a common early precursor cell, that is, the cuboidal epithelial cell at the canalicular stage.     

Localization of Mannose, TV-Acetylglucosamine and Galactose in the Golgi Apparatus, Plasma Membranes and Cell Walls of Scenedesmus acuminatus

The localization of lectin binding sites in the Golgi apparatus,plasma membranes and cell walls of Scenedesmus acuminatus wasinvestigated by cytochemical electron microscopy. The lectinsused were concanavalin A (Con A), peanut agglutinin (PNA) andwheat germ agglutinin (WGA), all labeled with gold. Con A-goldparticles were deposited not on the Golgi apparatus, but onthe outer cell-wall layer. PNA-gold and WGA-gold particles weredeposited on distal Golgi cisternae and vesicles derived fromthe Golgi apparatus. Entire cell-wall layers were evenly labeledby PNA-gold. The plasma membrane and cytoplasmic regions closeto the plasma membrane were labeled with WGA-gold. The processingof oligosaccharide in the Golgi apparatus, plasma membranesand cell walls of Scenedesmus acuminatus is discussed in referenceto that reported for animal cells. (Received March 5, 1987; Accepted July 18, 1987)     

Modulation of endothelial cell surface glycoconjugate expression by organ-derived biomatrices

Cell surface molecules play an important role in cellular communication, migration, and adherence. Here, we show the effect of organ-derived biomatrices on endothelial cell surface glycosylation. Five different lectins (with and without neuraminidase treatment) have been used as probes in an enzyme-linked lectin assay to quantitatively detect glycoconjugates on endothelial cells (BAEC) grown on tissue culture plastic or biomatrices isolated from bovine lung, liver, and kidney. BAEC generally exhibit strong binding of concanavalin A (Con A), Ricinus communis agglutinin I (RCA-I), wheat germ agglutinin (WGA), and soybean agglutinin, and peanut agglutinin after neuraminidase pretreatment of cells (Neu-SBA and Neu-PNA), while SBA and PNA consistently bind weakly to BAEC. BAEC grown on organ-derived biomatrices exhibit significantly altered binding intensities of Con A, RCA-I, WGA, and Neu-PNA: BAEC cultured on lung- or kidney-derived biomatrices express significantly stronger binding affinities for Con A and RCA-I than BAEC grown on liver-derived biomatrix or tissue culture plastic. In contrast, BAEC binding of WGA and PNA (after treatment of cells with neuraminidase) is significantly reduced when BAEC are grown on liver- or kidney-derived biomatrix. Quantitative lectin immunogold electron microscopy reveals consistently stronger lectin binding over nuclear regions compared to junctional regions between neighboring cells. These results indicate that extracellular matrix components regulate endothelial cell surface glycoconjugate expression, which determines cellular functions, e.g., preferential adhesion of lymphocytes or metastatic tumor cells.     

Expression of Thomsen-Friedenreich (TF) antigens on lymphocytes. I. Distribution of cryptic and exposed TF antigens on murine lymphocytes from different lymphoid organs: detection with an anti-TF monoclonal antibody and peanut agglutinin

Cryptic Thomsen-Friedenreich (TF) antigens were detected by the lectin peanut agglutinin (PNA) on the surface of murine lymphocytes after treatment of cells with neuraminidase. Thereby, a particular TF antigen could be distinguished using a monoclonal anti-TF antibody 49H8. In contrast to the known general galactoside specificity of PNA, the mAb was restricted to Gal beta(1-3)GalNAc/GlcNAc. Preincubation of cells with PNA abolished mAb 49H8 binding completely. However, only the intensity of staining with PNA was reduced by prior incubation of cells with the mAb. Cryptic TF antigens detected by the mAb were expressed on 39% of murine bone marrow cells, 88% of thymocytes, 62% of lymph node cells, and 65% of spleen cells. On the other hand, over 80% of the lymphatic cells carried cryptic PNA binding sites independent of the lymphoid organ they derived. In the thymus, a subpopulation of cells (76%) could be detected by PNA without neuraminidase treatment. Twenty-eight percent of thymocytes carried exposed mAb binding sites, too. All of them were shown to express further binding sites for PNA constantly. Therefore, a subpopulation of PNA-reactive, immature thymocytes can be distinguished by the mAb 49H8. During activation of splenic lymphocytes with PHA, the lymphoblasts completely lost their cryptic mAb binding sites while PNA reactivity was not affected. We conclude that the anti-TF mAb recognizes a particular TF antigen exposed on thymocytes and present in a cryptic form on other lymphocytes. The number of cells carrying mAb 49H8 binding sites varied, dependent on the organ from which the lymphocytes derived. PNA-reactive lymphocytes are distributed homogeneously in the lymphoid organs.     

Polarization of plasma membrane glycoconjugates in amphibian epidermis during metamorphosis

Summary Wheat germ agglutinin (WGA) binding sites have been examined in tadpole epidermal cells at the level of both light and electron microscopy using the WGA-ovomucoid-gold technique. In premetamorphic tadpoles the reaction was observed on the plasma membranes of epithelial cells showing a gradient from inner to outer membranes. These glycoconjugates were polarized during development, and at the end of metamorphic climax they were only located in plasma membranes of stratum corneum. The existence of an apical cell surface coat is needed to facilitate the absorption of water through the adult epidermis. The possible implications of this polarization process are discussed.     

Polarization of plasma membrane glycoconjugates in amphibian epidermis during metamorphosis

Wheat germ agglutinin (WGA) binding sites have been examined in tadpole epidermal cells at the level of both light and electron microscopy using the WGA-ovomucoid-gold technique. In premetamorphic tadpoles the reaction was observed on the plasma membranes of epithelial cells showing a gradient from inner to outer membranes. These glycoconjugates were polarized during development, and at the end of metamorphic climax they were only located in plasma membranes of stratum corneum. The existence of an apical cell surface coat is needed to facilitate the absorption of water through the adult epidermis. The possible implications of this polarization process are discussed.     

WGA-binding, mucin glycoproteins protect the apical cell surface of mouse uterine epithelial cells.

Expression of apical cell surface proteins and glycoproteins was examined in polarized primary cultures of mouse uterine epithelial cells (UEC). Lectin-gold cytochemistry revealed that wheat germ agglutinin (WGA) bound specifically to the components of the apical glycocalyx as well as intracellular vesicles. Double labeling with the pH sensitive dye 3-(2,4-dinitroanilino)-3'amino-N-methyldipropylamine (DAMP) demonstrated the acidic nature of the WGA-staining intracellular vesicles. The enzymatic and chemical sensitivities of the WGA binding sites on the apical cell surface were monitored both by WGA-gold staining as well as by 125I-WGA binding assays. In thin sections, a large fraction of these sites were removed by pronase; however, application of a wide variety of proteases, glycosidases, or chemical treatments to the apical surface of intact UEC failed to reduce WGA binding. In no case did treatments designed to remove sialic acids reduce 125I-WGA binding more than 12%. In contrast, endo-beta-galactosidase as well as a combination of beta-galactosidase with beta-hexosaminidase succeeded in removing 28% and 77% of these sites, respectively. These studies suggested that the majority of the apically disposed WGA binding sites involved N-acetylglucosamine residues rather than sialic acids and included lactosaminoglycans. Many of the proteins detected at the apical cell surface by lactoperoxidase-catalyzed radioiodination were WGA-binding glycoproteins. A major class of these glycoproteins displayed Mr > 200 kDa by SDS-PAGE and was heavily labeled metabolically by 3H-glucosamine or by vectorial labeling at the apical cell surface with galactosyl transferase and UDP-3H-galactose. Analyses of the 3H-labeled oligosaccharides labeled by either procedure indicated that a large fraction of the apically disposed WGA-binding oligosaccharides consisted of neutral, O-linked mucin-type structures with median MW of approximately 1,500. Oligosaccharides in this fraction were partially (15%) sensitive to endo-beta-galactosidase digestion and bound to Datura stramonium agglutinin (68%), demonstrating the presence of lactosaminoglycan sequences. UEC were an extremely effective barrier to attachment or invasion by either a highly invasive melanoma cell line, B16-BL6, or implantation-competent mouse blastocysts. In contrast, neither uterine stromal cells nor a non-polarizing UEC cell line, RL95, prevented B16-BL6 attachment.(ABSTRACT TRUNCATED AT 400 WORDS)     

Histochemical demonstration of O-glycosidically linked, type 3 based ABH antigens in human pancreas using lectin staining and glycosidase digestion procedures

Histochemical analyses of the chemical structures of sugar sequences with or without blood group specificity were carried out by combined stepwise digestion of tissue sections with exo- and endoglycosidases and subsequent lectin stainings in formalin-fixed, paraffin-embedded human pancreas. In acinar cells from blood group A or AB secretor individuals, sequential digestion with alpha-N-acetylgalactosaminidase and alpha-L-fucosidase imparted reactivity with peanut agglutinin (PNA) in cells reactive with Dolichos biflorus agglutinin as well as those with Ulex europaeus agglutinin I(UEA-I). Simple fucosidase digestion imparted the PNA reactivity only in UEA-I reactive cells. Sequential digestion with alpha-galactosidase and fucosidase likewise liberated the PNA binding sites in Griffonia simplicifolia agglutinin I-B4 reactive cells from blood group B and AB secretors. Sialidase digestion liberated the PNA binding sites not only in acinar cells but also intercalated duct cells, islet cells of Langerhans and endothelial cells. The PNA reactivity obtained by these enzyme digestions was eliminted by endo-alpha-N-acetylgalactosaminidase (endo-GalNAcdase) digestion. Preexisting PNA affinity in acinar cells from non-secretors was also susceptible to endo-GalNAcdase treatment. Following the endo-GalNAcdase digestion, fucosidase or sialidase digestion recovered the PNA reactivity in acinar cells from nonsecretors. These results show that ABH determinants carried on O-glycosidically linked type 3 chain (D-galactose-(beta 1-3)-N-acetyl-D-galactosamine alpha 1-serine or threonine) are secreted in pancreatic acinar cells and suggest that product coded by the secretor gene is required for the complete conversion of type 3 precursor chains into H determinants.     

Histochemical methods for characterizing secretory and cell surface sialoglycoconjugates

Paraffin sections of trachea, sublingual gland, and pancreas from rats, mice, and hamsters were stained with peanut agglutinin (PNA) or Dolichos biflorus agglutinin (DBA) conjugated to horseradish peroxidase before or after enzymatic removal of sialic acid. Adjacent sections were oxidized with periodate prior to incubation with sialidase and staining with PNA and DBA. PNA binding demonstrated terminal beta-galactose in secretions, at the basolateral plasmalemma of mouse tracheal serous cells, in or at the surface of zymogen granules, and at the apical and basolateral surface of mouse and hamster pancreatic acinar cells. Sialidase digestion revealed PNA binding, demonstrative of penultimate beta-galactose, in secretions of mucous cells in tracheal and sublingual glands and at the apical glycocalyx of ciliated and secretory cells in the tracheal surface epithelium of all the rodents studied. Sialidase also imparted PNA affinity to endothelium in all three species and to secretions and the basolateral plasmalemma of tracheal serous cells and pancreatic acinar cells in the rat. Periodate oxidation blocked the enzymatic removal of N-acetylneuraminic acid as judged by prevention of staining with the sialidase-PNA procedure. Sites in which periodate prevented sialidase-PNA staining included pancreatic islet cells and at the luminal glycocalyx of ciliated and secretory cells in tracheal surface epithelium in all three rodents, most sublingual mucous cells in the hamster, pancreatic acinar cells in the rat, and endothelium, except that of the rat. Glycoconjugate in other sites remained positive with the periodate-sialidase-PNA sequence. Resistance to periodate was interpreted as evidence for the presence of terminal sialic acid with an O-acetylated polyhydroxyl side chain. DBA binding demonstrated terminal alpha-N-acetylgalactosamine in the secretion of all mucous cells in the hamster trachea and 50-90% of those in the rat, secretion and the basolateral plasmalemma of all glandular serous cells in the mouse trachea, at the apical surface of most secretory cells lining the lumen of the rat and hamster trachea, and cilia of 5-10% of ciliated cells in the rat trachea. Periodate oxidation and sialidase digestion demonstrated N-acetylneuraminic acid and penultimate alpha-N-acetylgalactosamine in cilia in the mouse trachea and sialic acid containing O-acetylated polyhydroxyl side chains subtended by N-acetylgalactosamine in the secretion of all mucous cells in the rat and hamster trachea and of 80-90% of mucous cells in the hamster sublingual gland.(ABSTRACT TRUNCATED AT 400 WORDS)     

Alkaline phosphatase activity of the IVth ventricular choroidal epithelium of rats during embryonic and neonatal development

The cytochemical localization of alkaline phosphatase (AlPase) activity in the developing IVth ventricular choroidal epithelium was investigated in embryonic and neonatal rats. During the initial development of the choroidal primodium the flattened and/or cuboidal epithelial cells of the ventricular roof were changed to columnar cells with well-developed microvilli and apical tight junctions. When compared to AlPase activity on the lateral plasma membranes of the surrounding ependymal cells, these columnar cells of the choroidal primodium revealed activity on the lateral and luminal plasma membranes, but no activity was found on the basal surface of these cells. On the other hand, the epithelial cells in the neonatal choroid plexus showed a continuous morphological alteration from columnar cells with short microvilli to mature cuboidal cells with numerous long microvilli. AlPase activity in immature columnar cells was observed on all plasma membranes, except for the apical junctional area of the lateral surface. With maturing of the choroidal epithelial cells, the activity appeared to be eliminated from the lateral and luminal plasma membranes of the cuboidal cells, and mature choroidal epithelial cells showed activity on the basal surface only. These findings suggest that AlPase may play an important role in the membrane activity of epithelial cells differentiating between the primitive epithelial cells of the ventricular roof and the mature choroidal epithelial cells.     

Urothelium-specific antibody and lectin surface mapping of bladder urothelium

Summary Coupled ligand-colloidal gold complexes were found to provide a convenient approach for the localization by scanning electron microscopy of cell surface membrane antigens and lectin-binding sites on bladder urothelium and for the immunocytochemical identification of urothelial cell populations at different stages of differentiation. The ligands used to probe the membrane were a urothelium-specific rabbit antibody raised to a urothelial membrane-associated antigen (UMA), and two lectins: Concanavalin A (Con A) and peanut agglutinin (PNA). A complex luminal surface distribution pattern was demonstrated by the UMA antigen related to the stage of urothelial cell maturation and differentiation. UMA could be detected on the surface of immature and early differentiating intermediate cells, but was absent from the late differentiation stage, becoming re-expressed as the cells matured and was found in greatest abundance on the terminally differentiated superficial cells. It was absent on cells in benign hyperplasia of the urothelium. Cellular and regional differences in lectin binding to the urothelial cell surface was suggested with Con A receptors localized uniformly over the superficial cells, and PNA receptors confined to linear arrays or occasional clusters over the apical surface but evenly dispersed over the lateral surface of these cells.     

Lectin binding to injured corneal endothelium mimics patterns observed during development

Fluorochrome conjugated lectins were used to observe cell surface changes in the corneal endothelium during wound repair in the adult rat and during normal fetal development. Fluorescence microscopy of non-injured adult corneal endothelia incubated in wheat-germ agglutinin (WGA), Concanavalin A (Con A), and Ricinus communis agglutinin I (RCA), revealed that these lectins bound to cell surfaces. Conversely, binding was not observed for either Griffonia simplicifolia I (GS-I), soybean agglutinin (SBA) or Ulex europaeus agglutinin (UEA). Twenty-four hours after a circular freeze injury, endothelial cells surrounding the wound demonstrated decreased binding for WGA and Con A, whereas, RCA binding appeared reduced but centrally clustered on the apical cell surface. Furthermore, SBA now bound to endothelial cells adjacent to the wound area, but not to cells near the tissue periphery. Neither GS-I nor UEA exhibited any binding to injured tissue. By 48 h post-injury, the wound area repopulates and endothelial cells begin reestablishing the monolayer. These cells now exhibit increased binding for WGA, especially along regions of cell-to-cell contact, whereas, Con A, RCA and SBA binding patterns remain unchanged. Seventy-two hours after injury, the monolayer is well organized with WGA, Con A and RCA binding patterns becoming similar to those observed for non-injured tissue. However, at this time, SBA binding decreases dramatically. By 1 week post-injury, binding patterns for WGA, ConA and RCA closely resemble their non-injured counterparts while SBA continues to demonstrate low levels of binding. In early stages of its development, the endothelium actively proliferates and morphologically resembles adult tissue during wound repair.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lectin histochemistry of mammalian Brunner's glands

Lectin histochemical study was performed on twenty-eight specimens of formalin-fixed paraffin embedded tissues of proximal duodenum from human, cat, dog and Rhesus (macaque) monkey to demonstrate the pattern of carbohydrate residues in submucosal glands of Brunner as compared to that of the duodenal absorptive and goblet cells. Ten different biotinylated lectins were used as probes, and avidin-biotin-peroxidase (ABC) or avidin-gold-silver (AGS) complexes were used as "visualants". Brunner's gland cells of the four species studied exhibited a similar lectin-binding pattern which differ from other duodenal cells. The epithelium of Brunner's gland stained intensely with Ricinus communis agglutinin-I (RCA-I), succinylated-WGA (S-WGA) and wheat-germ agglutinin (WGA), moderately with Bandeirea simplicifolia agglutinin-I (BS-I), Concanavalia ensiformis agglutinin (Con A) peanut agglutinin (PNA) and Ulex europaeus agglutinin-I (UEA-I) and occasionally with Dolichos biflorus agglutinin (DBA), Lens culinaris agglutinin (LCA) and soybean agglutinin (SBA). Desialylation with neuraminidase resulted in only a slight elevation in binding intensities of PNA, DBA and SBA, indicating that glycoconjugates of the Brunner's gland cells are rich in asialo-oligosaccharides, which differs from duodenal epithelial cells. In addition, these histochemical reagents were useful in localizing Brunner's gland elements in the duodenal mucosa.     

Enhancement of cell-cell contact by a nonmitogenic lectin increases blastogenic response and IL-2 release by mitogen-stimulated mouse thymocytes

We have examined the influence of peanut agglutinin (PNA), a lectin which agglutinates but does not stimulate mouse thymocytes, on the responsiveness of these cells to concanavalin A (Con A) or galactose oxidase stimulation. Binding low amounts of PNA on unseparated mouse thymocytes pretreated with neuraminidase highly enhances the mitogenic response and the level of interleukin 2 release in the culture medium upon Con A stimulation. We have shown that PNA present on the cell surface acts as a crosslinking agent which favors intercellular binding between accessory cells (macrophages) and thymocytes, leading through this enhanced cooperation by cell-cell contact to an enhanced blastogenic response.     

Cell surface binding sites for peanut agglutinin in the differentiating eye disc of Drosophila

The distribution of peanut agglutinin (PNA) binding sites in imaginal discs is described using fluorescence and electron microscopy. PNA binds preferentially to the photoreceptor cell precursors in eye discs resulting in a rectilinear array of fluorescent spots that reflects that lattice-like arrangement of the presumptive ommatidia. The lectin binds to the apical surface of fixed disc cells and is taken up in presumed endocytotic vesicles in living discs. Photoreceptor precursors can be visualized with fluorescein isothyocyanate-PNA from the time they first form preclusters in the morphogenetic furrow and this technique is used to demonstrate a temperature-sensitive defect in precluster formation in the mutant shibire. PNA is localized along the sides of microvilli of disc cells, in general. The preferential binding of PNA to photoreceptor precursors is related in part to the high density of apical microvilli on these cells.