Effects of pimozide on the ultrastructure of the pars intermedia in the rat

Summary The effects of pimozide, a dopamine receptor-blocking agent, were studied in the pars intermedia of the rat. The animals received 100 g/100 g pimozide daily for 2, 5, 10, 15, and 20 days. Pimozide induces ultrastructural changes after 5 days of treatment. About 50% of the MSH-cells display characteristics of stimulation. Their cytoplasm is partially or totally depleted of secretory granules. The rough endoplasmic reticulum displays a network of interconnecting cisternae and ribbon-like structures. The well-developed Golgi complexes exhibit numerous dilatations of their cisternae, which contain electron-dense material. The nerve endings are not altered. Twenty days after treatment, the above-described changes have not decreased in magnitude. The present findings suggest that pimozide stimulates the mechanism of synthesis and release in some MSH-cells, most probably the elements underlying an inhibitory dopaminergic control.Supported by CONICET and CIUNC of ArgentinaMember of the Research Career of CONICET, ArgentinaFellow of CONICET, Argentina     

The effects of Tunicamycin and 2-deoxy-D-glucose on the development ofXenopus laevis embryos

Summary Tunicamycin and 2-deoxy-D-glucose were applied toXenopus laevis embryos in the first cleavage furrow, blastula and early gastrula stages. No effect was observed with 2-deoxy-D-glucose up to the concentration 0.1 M. The effect of Tunicamycin is dose- and stage-dependent. At the concentration of 5 g/ml cleaving embryos are arrested at the onset of gastrulation and their cells exhibit decreased intercellular adhesivity, while embryos treated in the blastula and early gastrula stages may develop up to the late neurula and tail-bud stage, respectively. Higher concentrations (up to 20 g/ml) drastically affect cleavage. Concentrations of 4 to 1 g/ml allow embryos to develop up to more advanced stages; however, developmental defects are the rule. Concentrations of less than 1 g/ml do not affect development.     

In vitro effects of puromycin aminonucleoside on the ultrastructure of rat glomerular podocytes

Summary Puromycin aminonucleoside (PAN)-induced nephrosis in rats provides a model for studying the pathogenesis of severe proteinuric conditions, such as minimal change disease. The present study used scanning (SEM) and transmission (TEM) electron microscopy to investigate the in vitro effects of PAN on rat glomerular podocytes. Slices of rat kidney were incubated for up to 3 days in Medium 199 with Hanks' salts (control) or in medium with PAN. Semiquantitative SEM analysis of glomeruli on the upper surface of kidney slices indicated that incubation with PAN (100 g/ml and 500 g/ml) decreased the number of microvilli on podocyte cell bodies (days 1, 2 and 3), increased the number of glomeruli showing flattening of podocyte cell bodies and major processes (days 2 and 3), and increased the number of glomeruli showing surface membrane blebbing on podocyte foot processes (day 3) (p<0.001 in all cases). TEM morphometry revealed that incubation with 500 g/ml PAN retarded significantly (p<0.001 at days 2 and 3) the loss of podocyte foot processes observed in control cultures. Whilst the SEM changes to podocyte ultrastructure largely mimic those seen in PAN nephrosis in vivo, the retardation of foot process loss runs counter to the major TEM change observed in vivo.     

Ultrastructural responses of pancreatic β cells to metabolic alkalosis

Summary The ultrastructural changes in pancreatic cells were studied following glucose-induced insulin secretion in vitro, at two different extracellular pH (7.4 and 7.8). The pancreata perfused at pH 7.4 exhibited a biphasic insulin response to glucose challenge together with signs of increased emiocytotic activity and numerous microtubules in the cells. Conversely, the pancreata perfused at pH 7.8 showed a significant decrease in insulin secretion, and their cells revealed scarce emiocytotic images and a marked increase of intracellular granulolysis. These results represent the ultrastructural correlate of the reduced insulin secretion produced by metabolic alkalosis in the perfused rat pancreas.The authors wish to thank Mrs. Elma P. de Gagliardino and Mrs. Susana Rivas for excellent technical assistance.This research was partially supported by funds from CONICET and CIC, Pcia de Bs.As. C.L. Gómez Dumm, O.R. Rebolledo and J.J. Gagliardino are members of Carrera del Investigador del CONICET (Argentina)     

Ultrastructural aspects of the effect of calcium ionophore A23187 on incubated anterior pituitary cells of rats

In order to study the fine structural effect of calcium influx on secretory activity of rat anterior pituitary cells, small pieces of anterior pituitary were incubated in Krebs' medium containing the calcium ionophore A23187 (0.15 mM) and were examined electron microscopically. Marked changes were present in all types of secretory cells incubated for 3, 12 and 20 min in the medium containing calcium and A23187. Secretory granules tended to accumulate in the peripheral cytoplasm of the secretory cells, and more numerous images of granule release by exocytosis were observed in somatotroph (STH cell), luteotroph (LTH cell), thyrotroph (TSH cell), corticotroph (ACTH cell), type 1 gonadotroph (Type 1 GTH cell), and type 2 gonadotroph (Type 2 GTH cell). In addition to the increase in the number of exocytosis of single granules, the simultaneous extrusion of multiple granules, "multigranular exocytosis", was often observed in all kinds of secretory cells, especially the ACTH-cells. Large numbers of granule cores were often located in large vacuole-like or channel-like structures, irregular in shape and size, which were open to the intercellular or pericapillary space. Some parts of the membrane of the vacuole-like or channel-like structures were coated. These observations are interpreted to suggest that the calcium influx stimulates the extrusion of the secretory granules by single or multigranular exocytosis.     

Chromate reduction by Microbacterium liquefaciens immobilised in polyvinyl alcohol

A polyvinyl alcohol-based immobilisation technique has been utilised for entrapping the newly-isolated chromate-reducing bacterium, Microbacterium liquefaciens MP30. Three immobilisation methods were evaluated: PVA-nitrate, PVA-borate and PVA-alginate. Chromate reduction was studied in batch and continuous-flow bioreactors, where the beads maintained integrity during continuous operation. PVA-borate and PVA-alginate cell beads showed a higher rate and extent of chromate reduction than PVA-nitrate cell beads in batch experiments. With the former 100 M Cr(VI) was removed within 4 days, while only 40 M Cr(VI) was removed using the latter, and with no increase in Cr(VI) removal subsequently. Cell activity was maintained during immobilisation but the rate of Cr(VI) removal by immobilised cells was only half that of an equivalent mass of free cells. Using PVA-alginate cell beads in a continuous-flow system, chromate removal was maintained at 90–95% from a 50 M solution over 20 days without signs of bead breakdown.     

Fine structure of the mouse anterior pituitary maintained in a short-term incubation system

Summary Anterior pituitaries of mice were incubated for periods up to four hours in Krebs-Ringer bicarbonate glucose gassed with 95% O₂5% CO₂. The incubated explants survived and retained a fine structure that approximated the condition in situ. The few necrotic cells were sharply localized, and were found to be due to initial mechanical damage to the tissue.Some cells of the six granulated types exhibited slight but significant changes attributable to the liberation from the hypothalamic control: in LTH cells there was a release of preexisting granules and a development of cell organelles, whereas in other cell types there was an inhibition of release of granules and an enhanced digestion of the accumulated granules by the lysosomal system.Follicular cells responded uniquely to the changed environment by hypertrophy of the cytoplasm and were found to phagocytize cell debris. A part of non-epithelial elements of the gland showed a tendency to modulate cytologically.The author would like to express his appreciation to Mr. T. Anzai and Mr. S. Terada for their excellent technical assistance.     

Nerve Cells Associated with the Endocrine Pancreas in Young Mice: An Ultrastructural Analysis of the Neuroinsular Complex Type I

The neuroinsular complex type 1 is composed of pancreatic endocrine islet cells and nerve cell bodies intrinsic to the islet. The details of the relation between nerve cells and between endocrine cells and nerve cells in the complex are unknown. Pancreata from newborn and 18-day-old mice were analysed by electron microscopy to establish the ultrastructural morphology of the neuroinsular complex. Immunohistochemical staining for protein gene-product 9.5 was also performed. The study showed that nerve cell bodies were closely associated to each other in the periphery of the islets with no connective tissue separating the cells. The nerve cells were closely associated to both -cells and -cells. Direct intercellular contacts were observed between nerve cells and endocrine cells and between Schwann cells and endocrine cells. Varicose nerve endings were frequently observed in the neuroinsular complex. In the peripheral parts the varicosities were mostly being associated to the nerve cell bodies. The varicosities contained small clear or small clear and larger dense cored vesicles, suggesting cholinergic and peptidergic contents. The varicosities made specialized synaptic connections with adjacently located nerve cells. The study shows that the neuronal part of the neuroinsular complex is closely associated to the endocrine islet cells and that it is richly innervated, indicating an important regulatory function of the nerve cell component in the neuroinsular complex.     

Synergistic tumor regressive activity observed following treatment of line-10 hepatocellular carcinomas with deproteinized BCG cell walls and mutant Salmonella typhimurium glycolipid

Summary Synergistic tumor-regressive activity was observed when the water-soluble portion of a phenol-water extract from mutant Salmonella typhimurium whole cells was combined with deproteinized cell walls from Mycobacterium bovis strain BCG. As little as 50 g deproteinized cell walls combined with 50 g water-soluble extract from the mutant salmonella produced 89–100% cures of line-10 dermal tumors in treated strain 2 guinea-pigs. However, none of the animals was cured following treatment with 50 g of deproteinized cell walls alone. Only 17% of treated animals were cured following treatment with 50 g of the water-soluble extract from the mutant salmonella. The deproteinized cell walls and water-soluble extract were suspended in oil-in-water emulsions and injected directly into 10 mm tumors. The deproteinized cell walls were prepared by treating BCG cell walls with proteolytic enzymes and denaturing agents (KCl, urea, Triton X-100, and guanidine hydrochloride). Urea or a combination of denaturing agents reduced the protein content of protease-treated cell walls from approximately 2% (w/w) protein to 0.7% protein. The antigenicity of the effectively deproteinized cell walls, as measured by skin testing in presensitized guinea-pigs, was reduced approximately ten-fold compared with untreated cell walls. Injection to mice of 500 g deproteinized cell walls in combination with 500 g water-soluble extract from the mutant salmonella produced transient, clinical signs of toxicity (malaise, conjunctivitis, diarrhea, and rough hair coats) lasting approximately 5 days. However, no deaths were observed. The synergistic antitumor effect of combining deproteinized BCG cell walls with the water-soluble extract from mutant salmonella may be useful for treatment of certain cases of spontaneous neoplastic disease.     

Diplosporous embryo-sac formation and the degree of diplospory inAllium tuberosum

Summary To obtain information on the dynamic and quantitative aspects of displospory in a facultative apomict,Allium tuberosum (2n = 32), we cytologically observed the entire course of female meiosis and embryosac development in cv Tender-Pole by the clearing-staining-squash method. A time-table of its course was constructed in terms of bud length and days pre-anthesis. Chromosome threads were observed in pairs at the earliest stage of meiosis, after which 32 autobivalents developed. Thus, endoreduplication must have occurred during premeiotic interphase or at the onset of female meiosis. Such endoreduplicational meiosis also occurred on the male side, though the frequency (3.9%) was much lower than that on the female side (80%). The degree of diplospory calculated as the percentage of reduplicated embryo-sac mother cells varied to some extent among six cultivars: Huhehaote and Manchuria showed the highest degree of diplospory (98%), and Kaohsiung the lowest (76%).     

Differentiation-dependent glycosylation of gp190, an oncofetal crypt cell antigen expressed by Caco-2 cells

gp190 is a glycoprotein expressed on the cell surface of several human colon carcinoma cells in culture, on epithelial cells of fetal colon, but not on the normal mucosa of adult colon; thus it is referred to as an oncofetal crypt cell antigen. We report the characterisation of O[emsp4 ]-linked glycans carried by gp190 synthesised by [³H]glucosamine-labelled Caco-2 cells at the confluence (undifferentiated cells) and at three weeks of postconfluence (differentiated cells). By using a specific monoclonal antibody, gp190 was isolated and analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The mobility of gp190 from differentiated cells was found to be lower than that from undifferentiated cells, suggesting a more extensive glycosylation process in the former glycoprotein. The major results of the glycan characterisation have been as follows: (i) gp190 carries mainly, if not exclusively, O-linked glycans with the core-2 structure; (ii) the elongation with N-acetyllactosamine units of the Gal1,4GlcNAc1,6(Gal1,3)GalNAc tetrasaccharide predominates in gp190 synthesised by differentiated cells, whereas the direct 2,3sialylation of the tetrasaccharide is prevalent in gp190 synthesised by undifferentiated cells. The increment in the core-2 1,6GlcNAc-transferase activity under the Caco-2 differentiation process may be relevant in producing the larger occurrence of polylactosaminoglycans in gp190 from differentiated cells. Since no change in the activity of the 2,3sialyltransferases upon cell differentiation was observed, we suggest that the lower 2,3sialylation in gp190 synthesised by polarised cells might be due to a changed transit-rate through the distal Golgi apparatus.     

Carbon fixation in eucalypts in the field

Summary The rate of CO₂ assimilation at light saturation and an intercellular CO₂ concentration of 350 l l^-1 (photosynthetic capacity), measured in leaves of Eucalyptus pauciflora, E. behriana, E. delegatensis and Acacia melanoxylon, declined over the course of cloudless days under naturally varying environmental conditions as well as under constant optimal conditions for high CO₂ uptake. Since the capacity did not recover during the light period, it was different from the midday depression of gas exchange. The change appeared to be caused neither by the diurnal variation of total leaf water potential, by photoinhibition of redox-reaction centres in photosystems nor by changes in the intrinsic properties of Ribulose-bisphosphate carboxylase-oxygenase. The decline was more pronounced in winter than in summer. It was related to the duration of illumination or the cumulative carbon gain. It was reversible in the following dark phase, and it did not occur on changeable days with short peaks of high light.Despite the decline in photosynthetic capacity, the initial slope of the CO₂ response of net photosynthesis, as obtained at low intercellular CO₂ concentrations, remained constant during the day, but declined at night when photosynthetic capacity recovered. In all cases stomatal conductance varied in parallel with photosynthetic capacity. The relevance of changes in photosynthetic capacity for the intercellular CO₂ concentration is discussed.Abbreviations and symbols A CO₂ assimilation - ABA abscisic acid - A_c350 photosynthetic capacity at c_i=350l l^-1 - c_i intercellular CO₂ concentration - g leaf conductance to water vapour - I photon flux density (irradiance) - P air pressure - P_i inorganic phosphate - R_d net CO₂ release at _* - Rubisco Ribulose-bisphosphate carboxylase-oxygenase - RuBP Ribulose-bisphosphate - T leaf temperature - w leaf-to-air water vapour concentration difference - A/c_i carboxylation efficiency at low c_i - _* light-independent CO₂ compensation point - total leaf water potential     

Homocysteine stimulates the expression of monocyte chemoattractant protein-1 in endothelial cells leading to enhanced monocyte chemotaxis

The effect of intraperitoneal administration of tocopherol (100 mg/kg wt/24 h) on ascorbate (0.4 mM) induced lipid peroxidation of mitochondria and microsomes isolated from rat liver and testis was studied. Special attention was paid to the changes produced on the highly polyunsaturated fatty acids C20:4 n6 and C22:6 n3 in liver and C20:4 n6 and C22:5 n6 in testis. The lipid peroxidation of liver mitochondria or microsomes produced a significant decrease of C20:4 n6 and C22:6 n3 in the control group, whereas changes in the fatty acid composition of the tocopherol treated group were not observed. The light emission was significantly higher in the control than in the tocopherol treated group. The lipid peroxidation of testis microsomes isolated from the tocopherol group produced a significant decrease of C20:4 n6 , C22:5 n6 and C22:6 n3, these changes were not observed in testis mitochondria. The light emission of both groups was similar. The treatment with tocopherol at the dose and times indicated showed a protector effect on the polyunsaturated fatty acids of liver mitochondria, microsomes and testis mitochondria, whereas those fatty acids situated in testis microsomes were not protected during non enzymatic ascorbateFe²⁺ lipid peroxidation. The protector effect observed by tocopherol treatment in the fatty acid composition of rat testis mitochondria but not in microsomes could be explained if we consider that the sum of C20:4 n6 + C22:5 n6 in testis microsomes is 2-fold than that present in mitochondria.     

Response of the seminiferous epithelium of the rat testis to withdrawal of androgen: evidence for direct effect upon intercellular spaces associated with Sertoli cell junctional complexes

The morphological response of the Sertoli cells to partial or complete withdrawal of testosterone was studied in adult rats following hypophysectomy or administration of ethane dimethanesulphonate (EDS), a toxicant known to destroy selectively the Leydig cells of the testis. To assess the role of germ cells in effecting changes to Sertoli cells following withdrawal of testosterone, germ cell-deficient rats with Sertoli-cell-only testes (SCO) were treated with EDS to remove the source of testosterone. At 6 days after hypophysectomy or 4,6 and 8 days after EDS treatment, stage VII and VIII seminiferous tubules showed degenerating germ cells and numerous basally-located vacuoles approximately 1–15 m in diameter. Ultrastructural analysis indicated that most of the vacuoles were multiple focal dilations of the intercellular space associated with Sertoli cell junctional complexes. In SCO rats, treatment with EDS resulted in a significant (P<0.05) increase in the formation of many vacuoles particularly in the base but also in the trunk of the Sertoli cells and again electron microscopic analysis showed multiple, localized expansions of the intercellular space associated with Sertoli cell junctional complexes. The appearance of intercellular spaces in SCO testes following androgen withdrawal cannot be attributed to shrinkage of degenerating germ cells since the seminiferous tubules did not contain germ cells. It is concluded that withdrawal of androgen induces early morphological alterations of the Sertoli cell junctional complexes in which the sites of membrane fusions representing tight junctions remain intact whereas the intercellular spaces exhibit major focal dilations. The results are discussed in relation to the fluid secretion by the seminiferous tubules which is regulated by the Sertoli cells.     

Growth inhibition of murine mammary carcinoma by monoclonal IgE antibodies specific for the mammary tumor virus

Summary Two IgE-producing hybridomas were established from spleen cells of Balb/c mice, which had been immunized with mouse mammary tumor virus (MMTV). These IgE monoclonal antibodies (mAbs) reacted specifically with the major envelope glycoprotein (gp36) of MMTV, as established by the immunoblot assay and by passive cutaneous anaphylaxis. The effect of the IgE mAbs (produced by clone A8) on the growth of the MMTV-secreting mammary adenocarcinoma H2712 was investigated in syngeneic C3H/HeJ mice. The mice were inoculated s.c. with either 10⁵ (100 × LD₅₀) or 10⁶ (1000 × LD₅₀) tumor cells and received repeated i.p. injections of 25 µg anti-gp36 IgE mAbs at 4-day intervals for 8 weeks. This treatment prevented the development of subcutaneous tumors in 50% of the animals. Similar protection was observed when the tumor cells (10⁵/animal) were injected i.p. 4 days prior to the beginning of the i.p. treatment consisting of injections of 25 µg mAbs at 4-day intervals for 6 weeks. However, these mAbs did not protect C3H/HeJ mice against the MMTV-negative MA16/c carcinoma cells. Hence, these results support the view that IgE-mediated cytotoxic mechanisms may play an immunologically specific antitumor surveillance role and that laboratory-induced antitumor IgE mAbs have the potential of specific therapeutic agents for in vivo destruction of tumor cells.     

Ability of a generalist insect,Schistocerca gregaria,to overcome thioglucoside defense in desert plants: tolerance or adaptation?

Desert locusts, Schistocerca gregaria (Forskål) (Orthoptera, Acrididae), are generalist herbivores that, in the Sahara desert, may at times feed only on Schouwia purpurea (Forskål) (Brassicaceae), that is 10 times richer in thioglucosides than currently observed in other crucifers (>100 moles/g d.w.). Thioglucosides, when ingested, release products that are usually toxic to generalist insects.We studied the short-term (8 days) and long-term (21–26 days) consequences of a Schouwia-only diet on the digestion of these insects. The response was compared to the effects of a diet of Brassica oleracea, a crucifer well consumed in laboratory rearing conditions (7 moles/g glucosinolates d.w.).We found that the production of a myrosinase was induced in the midgut as early as 8 days following exposure to glucosinolates. No negative short-term effects were observed on the growth of the insect, but the activity of -glucosidases decreased in the midgut. The long-term exposure to the Schouwia diet affected activities of -glucosidases and -galactosidases, growth and assimilation efficiency. The limited adaptation of the desert locust to plant glucosides is compensated by an ability to tolerate high concentrations of allelochemicals for a short period.     

Relief effect of vitamin A on the decreased motility of sperm and the increased incidence of malformed sperm in mice exposed neonatally to bisphenol A

Administration of 50 g of bisphenol A (BPA) for the first 5 days after birth resulted in a decrease in the percentage of moving sperm, and an increase in the incidence of malformed sperm, in the epididymides of mice at 10 weeks of age, although no marked changes were found in the testicular histology between BPA-treated and vehicle-treated control mice. The deteriorating effects of 50 g of BPA were ameliorated by the concurrent administration of 100 IU of retinol acetate (RA). Neonatal treatment with 0.5 g of BPA for 5 days resulted in an increase in the incidence of malformed sperm, whereas the BPA effect became more severe in mice nursed by mothers fed a vitamin A-deficient (VAD) diet only a few days before and after parturition. On the other hand, neonatal treatment with 20 g of estrogen for the first 5 days after birth resulted in an increase in the number of estrogen receptor (ER)-positive cells in the epithelium of the vas deferens, whereas only a few epithelial cells showed weak ER-positive signals in the vehicle-treated control mice at 18 days after birth. This increase, however, was suppressed by the concurrent administration of RA. Although five daily treatments with 50 g BPA led to no significant increase in the number of ER-positive cells, it may have been due to the weak estrogenic activity of BPA, as discussed. These findings clearly showed that in mice, neonatal exposure to a relatively large dose of BPA causes damage to the motility and morphology of sperm, but the BPA effect is, to some extent, inhibited by a supplement of VA, and enhanced under a VAD condition.This work was supported by Grants-in-Aid for Encouragement of Young Scientists, Scientific Research (C) and Scientific Research on Priority Areas (A) from the Ministry of Education, Science, Sports, and Culture, Japan     

Membrane differentiation in the cytoplasmic-tubule system of the intestinal absorptive cells of the lamprey,Lampetra japonica

Summary Specific membrane differentiation occurs in the cytoplasmic-tubule system of the absorptive cells lining the mucosa of the lamprey anterior intestine. The absorptive cells are characterized by the presence of abundant mitochondria and a system of well-developed cytoplasmic tubules (120 nm in diameter). The cytoplasmic tubules open on to the basolateral cell surface and contain numerous lipoprotein particles (50–100 nm diam.) in their lumina. Lipoprotein particles are also observed in the endoplasmic reticulum and the Golgi complex, and they are transfered to the lateral intercellular space and lamina propria by way of the cytoplasmic tubules. Spirally-wound parallel rows of particles are found in the luminal surface of the cytoplasmic tubules. The rows are 17 nm apart and are wound spirally at a pitch of 210 nm. Freeze-fracture images of the tubule membranes also show spiral arrays of particles (9 nm in diameter) on the P-face, and complementary shallow grooves on the E-face. From these observations, it is suggested that the cytoplasmic-tubule system of the intestinal absorptive cells serves as a channel for the transport of synthesized lipoprotein into the interstitium, and is also the site of the ion and water exchange essential for the maintenance of ionic homeostasis.     

Localization of GABAA receptors in the rabbit retina

The distribution of gamma-aminobutyric acid_A (GABA_A) receptors in the rabbit retina is investigated and compared with the distribution of GABAergic neurons using immunocytochemical methods. Antibodies against the 1, 2/3, and 2 subunits of the GABA_A receptor label subpopulations of bipolar, amacrine and ganglion cells. Double labeling experiments show that the 2 subunit is colocalized with the 1 and the 2/3 subunits in bipolar, amacrine and ganglion cells. Electron microscopy reveals that in the outer plexiform layer, GABA_A receptor immunoreactivity is present on dendrites of cone bipolar cells adjacent to the cone pedicles. Bipolar cell dendrites are also receptor-positive at synapses from interplexiform cells. Some receptor immunoreactivity is found intracellularly in processes of horizontal cells. In the inner plexiform layer, GABA_A receptor immunoreactivity is present on both rod bipolar and cone bipolar axon terminals at putative GABAergic input sites. Amacrine and ganglion cell processes in sublamina a and b are also labeled.     

Lectin cytochemical characterization of the N- and O-linked oligosaccharides in the human rectum

The oligosaccharides of the mucus glycoproteins of the human rectum are important for the lubricant and protective role suggested for the rectal mucus. Changes in oligosaccharide composition are observed in several colon diseases, and some of these changes could be used as diagnostic and prognostic indicators. Thus, a previous knowledge of the normal mucus glycoproteins is necessary. The aim of the present study is the characterization of the oligosaccharides of the goblet cells and enterocytes of the human rectum. For this, a battery of 15 lectins, in combination with chemical and enzymatic deglycosylation procedures, was used. Our results suggest the presence of N-acetylglucosamine (GlcNAc), Man, Glc, N-acetylneuraminic acid (Neu5Ac)(2–6)- and Neu5Ac(2–3)-linked, N-acetylgalactosamine (GalNAc) and Gal(1–3)GalNAc in the oligosaccharides of the goblet cells. Moreover, N-linked oligosaccharides specifically contained Gal(1–4)GlcNAc, while AAA-positive Fuc was only detected in O-linked oligosaccharides. Some of these carbohydrates were only visualized after removal of N- or O-linked oligosaccharides, suggesting a high level of approximation between the oligosaccharide chains, that render the carbohydrate inaccessible to the lectins. Differences in the labelling pattern between the goblet cells of the surface epithelium and the upper half of the crypts, and those of the lower half of the crypts suggests a maturation process for the goblet cells, which modifies the oligosaccharide composition of the secreted glycoproteins, as they ascend throughout the crypts. This maturation process includes the incorporation of new carbohydrates (GlcNAc), and the masking (Neu5Ac(2–3)-linked) or unmasking (Glc and GalNAc) of others.