Goblet cell fine structure

Clearance of small intestinal crypts involves goblet cell mucus secretion by intracellular granule rupture and enterocyte ion transport

Goblet cells in the small intestinal crypts contain large numbers of mucin granules that are rapidly discharged to clean bacteria from the crypt. Because acetylcholine released by neuronal and nonneuronal cells controls many aspects of intestinal epithelial function, we used tissue explants and organoids to investigate the response of the small intestinal crypt to cholinergic stimulation. The activation of muscarinic acetylcholine receptors initiated a coordinated and rapid emptying of crypt goblet cells that flushed the crypt contents into the intestinal lumen. Cholinergic stimulation induced an expansion of the granule contents followed by intracellular rupture of the mucin granules. The mucus expanded intracellularly before the rupture of the goblet cell apical membrane and continued to expand after its release into the crypt lumen. The goblet cells recovered from membrane rupture and replenished their stores of mucin granules. Mucus secretion from the goblet cells depended on Ca2+ signaling and the expansion of the mucus in the crypt depended on gap junctions and on ion and water transport by enterocytes adjacent to the goblet cells. This distinctive mode of mucus secretion, which we refer to as "expanding secretion," efficiently cleans the small intestine crypt through coordinated mucus, ion, and fluid secretion by goblet cells and enterocytes.

Cell-type diversity and regionalized gene expression in the planarian intestine

Proper function and repair of the digestive system are vital to most animals. Deciphering the mechanisms involved in these processes requires an atlas of gene expression and cell types. Here, we applied laser-capture microdissection (LCM) and RNA-seq to characterize the intestinal transcriptome of Schmidtea mediterranea, a planarian flatworm that can regenerate all organs, including the gut. We identified hundreds of genes with intestinal expression undetected by previous approaches. Systematic analyses revealed extensive conservation of digestive physiology and cell types with other animals, including humans. Furthermore, spatial LCM enabled us to uncover previously unappreciated regionalization of gene expression in the planarian intestine along the medio-lateral axis, especially among intestinal goblet cells. Finally, we identified two intestine-enriched transcription factors that specifically regulate regeneration (hedgehog signaling effector gli-1) or maintenance (RREB2) of goblet cells. Altogether, this work provides resources for further investigation of mechanisms involved in gastrointestinal function, repair and regeneration.

Endoplasmic reticulum stress is involved in the colonic epithelium damage induced by maternal separation

BACKGROUND

Maternal separation (MS) leads to intestinal barrier dysfunction in neonatal mice. Endoplasmic reticulum (ER) stress is associated with apoptosis and pro-inflammatory response induction. We hypothesized that MS induced gut damage is associated with ER stress and that administration of an ER stress inhibitor protects gut damage.

METHODS

C57BL/6 mice received intraperitoneal PBS (n=10) or Salubrinal (1mg/kg/day, n=10). MS was performed soon after treatment for 3h daily between P5 and P9. Ten untreated neonatal mice served as control. The colon was harvested on P9 and analyzed for ER stress markers (BiP, CHOP), apoptosis (CC3), goblet cell number per crypt and crypt length (Alcian blue, hematoxylin/eosin), and transcellular permeability (Ussing chamber). Groups were compared using one-way ANOVA with Bonferroni post-test.

RESULTS

Compared to controls, MS mice had higher relative protein expression of ER stress and apoptosis markers (p<0.05) and reduced goblet cell number per crypt and crypt length (p<0.001). In comparison to PBS mice, Salubrinal treated mice had higher goblet cell number (p<0.05), crypt length (p<0.001), and lower transcellular permeability (p<0.05).

CONCLUSIONS

Maternal separation induces ER stress and causes colon damage, but ER stress inhibitor protects morphology and permeability. This provides insights on bowel pathogenesis and potential novel treatments for diseases such as necrotizing enterocolitis.

Regulation of intestinal goblet cells in situ, in mucosal explants and in the isolated epithelium

Cholinergic secretagogues were previously shown to accelerate mucin secretion from intestinal goblet cells of adult rats and rabbits, both in vitro and in mucosal explants. This rapid secretory response occurs only in crypt cells; surface goblet cells are not affected. Rapid secretion involves the sequential fusion of secretory granule membranes with the plasma membrane and with each other, but does not require granule movement. In unstimulated cells, slow transport of secretory granules towards the luminal cell surface depends on functional microtubules. Goblet cells appear in the rat fetal intestine three to four days before birth but they are insensitive to cholinergic agents in the fetus and neonate. The secretory response of crypt goblet cells to carbachol, both in vivo and in mucosal slices in vitro, is established throughout the intestines only after weaning (20-25 days after birth). To determine whether acetylcholine from nerve endings in the intact mucosa may mediate a mucus secretory response in the absence of exogenous secretagogues, mucosal sheets were mounted in modified Ussing chambers and goblet cell secretion was assessed after electrical field stimulation. Electrical field stimulation elicited mucus secretion from crypt (but not surface) goblet cells. Secretion was inhibited by prior treatment of the mucosa with 500 nM-tetrodotoxin or 100 microM-atropine, but not by 10 microM-atropine. Thus, endogenous nerves may regulate mucus secretion from crypt goblet cells in the intact mucosa. When intact sheets of epithelium were isolated from adult rat ileum and colon, then maintained in vitro and exposed to 20 microM-carbachol, crypt goblet cells released mucin in response to the secretagogue but goblet cells in in portions of the epithelium derived from villi or mucosal surfaces were unresponsive. This suggests that crypt epithelial cells respond directly to cholinergic agents and that they lose this sensitivity as they migrate out of the crypts.

Site of synthesis, intracellular transport and secretion of glycoprotein in exocrine cells

The site of attachment of the first sugar, N-acetylgalactosamine, to the seryl and threonyl residues of the protein chain is unknown in exocrine cells. The subsequent sugars of the carbohydrate side chains, galactose and N-acetylglucosamine alternately, and the end-group sugars, galactose, N-acetylgalactosamine and fucose, are attached in the Golgi complex. Sulphate too is attached in that structure. In the stomach, sulphate is probably transferred in the most mature cisterna of the Golgi stacks, galactose and fucose in other cisternae, suggesting a gradient in transferase activities along the stack. The possibilities of regulating the amount and relative sugar composition of the glycoproteins are discussed. The secretory product is stored in granules. Their polygonal, large and swollen appearance and complex formation by loss of bordering membranes, as observed in many kinds of glycoprotein-secreting cells ('mucous cells') might be caused by ineffective fixation techniques. Direct vascular perfusion results in a picture no different from what is found in non-mucous cells. Whether secretion is merely exocytotic, as in non-mucous cells, or whether it is accompanied by a loss of membrane and even cytoplasm needs thorough investigation, with the effects of various fixation techniques being compared.

Unusual ultrastructural features in microvillous inclusion disease: A report of two cases

Microvillous Inclusion Disease (MID) is an inherited disorder characterized by intractable diarrhea in infancy. Ultrastructural detection of pathognomonic microvillous inclusions in the enterocytes is essential for diagnosis. The aim of this research is to contribute to the knowledge of MID studying enterocytes and goblet cells (gc). Samples of duodenal mucosa from two young infants with MID (aged 75 days and 3 months, respectively) were studied by light and electron microscopy. Detection in the intestinal villi of immature gc (with microvilli) in one of the cases led us to seek them in control samples. The total number of gc with microvilli (immature) and without microvilli (mature) were counted. In both MID specimens, light microscopy showed atrophy of villi and PAS-positive material in the enterocyte cytoplasm. The ultrastructure of villous enterocytes was characterized by brush-border abnormalities, microvillous inclusions, dense apical granules, and lysosomes. Intermediate structures between microvillous inclusions and lysosomes were also detected within a cell, as were rare microvilli on the lateral membrane of the enterocytes. In one MID specimen, immature gc were also identified in the absorptive compartment. Only mature gc were observed in the controls. The significance of the latter finding requires further studies.

Histology and ultrastructure of the gut epithelium of the neotenic cave salamander, Proteus anguinus (Amphibia, Caudata)

Histological, histochemical, and ultrastructural features of the gut of the European endemic cave salamander Proteus anguinus were studied. The gut is a relatively undifferentiated muscular tube lined with a simple columnar epithelium containing numerous goblet cells. The mucosa and underlying lamina propria/submucosa are elevated into a number of high longitudinal folds projecting into the lumen. The enterocytes are covered apically with uniform microvilli. Irregularity in the arrangement of microvilli was observed. Occasionally, irregular protrusions of the cytoplasm appear between groups of microvilli. Pinocytotic activity occurs at the bases of the intermicrovillous space. Mitochondria are numerous in the apical cytoplasm and basally beneath the nuclei. The supranuclear cytoplasm contains most of the cell organelles. The lateral plasma membranes of adjacent cells interdigitate and are joined by junctional complexes. The periodic acid-Schiff (PAS) reaction, indicating neutral mucosubstances, is positive only in the apical brush border of enterocytes and in goblet cells. The goblet cells also stained with Alcian blue (AB), at pH 2.5, thus revealing the presence of carboxylated glycosaminoglycans. Compact aggregations of AB- and PAS-negative cells are situated directly below the epithelium. Mitotic figures are present in individual clusters of cells. The fine structure of cells in these clusters indicated that these cells could be responsible for renewal of intestinal epithelium. Numerous endocrine-like cells could also be seen. The closely packed smooth muscle cells and amorphous extracellular material with collagen fibrils constitute a net-like structure under the basal lamina that is very closely associated with the epithelium. There are numerous acidophilic granular cells between epithelial cells, in the lamina propria/submucosa, and between cells aggregations. They seem to be associated with nematode infections and possibly constitute a humoral defense mechanism.

A novel in vitro model of Brunner's gland secretion in the guinea pig duodenum

A novel in vitro model that combined functional and morphological techniques was employed to directly examine pathways regulating Brunner's gland secretion in isolation from epithelium. In vitro submucosal preparations were dissected from guinea pig duodenum. A videomicroscopy technique was used to measure changes in luminal diameter of glandular acini as an index of activation of secretion. Carbachol elicited concentration-dependent dilations of the lumen (EC(50) = 2 microM) by activating muscarinic receptors on acinar cells. Ultrastructural and histological analyses demonstrated that dilation was accompanied by single and compound exocytosis of mucin-containing granules and the accumulation of mucoid material within the lumen. Inflammatory mediators (histamine, PGE(1), PGE(2)) and intestinal hormones (CCK, gastrin, vasoactive intestinal polypeptide, secretin) also stimulated glandular secretion, whereas activation of submucosal secretomotor neurons by 5-hydroxytryptamine did not. This study directly demonstrates that multiple hormonal, inflammatory, and neurocrine agents activate Brunner's glands, whereas many have dissimilar effects on the epithelium. This suggests that Brunner's glands are regulated by pathways that act both in parallel to and in isolation from those controlling epithelial secretion.

Collagen gel-embedding culture of conjunctival epithelial cells

BACKGROUND

Collagen has effects on cell morphology, differentiation characteristics and function. Using collagen gel culture, several studies about cell differentiation were reported. In this study, the differentiation of rabbit conjunctival epithelial cells in a collagen gel-embedding culture system was investigated by electron microscope and lectin labeling.

METHODS

Rabbit bulbar conjunctival epithelial cells were cultured in type I collagen gel. After 1 and 2 weeks of culture, some of these cells were stained with PAS and seven kinds of lectins, and others were examined by transmission electron microscopy.

RESULTS

The conjunctival epithelial cells cultured within collagen gel formed stratified cell layers and globules with cavities. The inner layer cells facing the cavities showed PAS and lectin staining patterns similar to those of conjunctival goblet cells in vivo, whereas the staining patterns of the outer layer cells on the collagen matrices resembled the patterns of non-goblet epithelial cells. Microvilli on the surface of the innermost cells, basement membranes beneath the outermost cells, tight junctions, adherent junctions, interdigitating folds and desmosomes between cells were identified on electron microscopic examination.

CONCLUSION

These results indicate that cell junction structures of the conjunctival epithelial cells are well developed in collagen gel-embedding culture systems, and that the inner layer cells have carbohydrates similar to those of conjunctival goblet cells. Culture of conjunctival epithelial cells within collagen gel is a useful model for examining differentiation of these cells.

Cytoarchitectural reorganization of rabbit colonic goblet cells during baseline secretion

Light and electron microscopy were coupled with point counting methods to quantitate shape and volume changes of goblet cells during their migration and maturation from the base of the crypt to the colonic surface epithelium in the rabbit. After differentiation, goblet cells attain a broad pyramidal configuration in the basal third of the crypt. The cells elongate and dramatically decrease in volume as they move into the surface epithelium. The distributions and volume fractions of organelles were found to vary considerably, depending on the location of the goblet cell in the epithelium. Mucin granules are initially synthesized throughout the cytoplasm, but become increasingly concentrated as the cell matures. Organelles involved in synthesis such as the Golgi apparatus and rough endoplasmic reticulum (RER) similarly attain a more concentrated arrangement as the cell moves up in the crypt. The mean cell volume decreases from 1,228.8 microns3 for cells in the basal third of the crypt to 541.3 microns3 for goblet cells on the surface. Most organelles decrease in proportion to this decrease, although a disproportionately large decrease in the RER was measured. When actual subcellular volumes are calculated, a net decrease in several subcellular compartments is detected. This loss of granules and organelles is accomplished by the continual synthesis and secretion of mucin granules. Cytoplasm and organelles become entrapped in the upward movement of granules towards the cell apex, become irretrievably isolated, and are sloughed into the crypt lumen. This process accounts for the decrease in cell volume and contributes to the altered cytoarchitecture of the cell.

Light and electron microscopic observation on the cervical epithelium of the rabbit. I

The light and electron microscopy of the cervical epithelium of ovulatory, estrous, and long-term ovariectomized rabbits have been studied to determine what structural changes occur under different hormonal conditions. The percentage of nonciliated secretory cells is 49.6 in ovulatory, 43.6 in estrous, and 23.7 in long-term ovariectomized rabbits, and of ciliated cells is 50.2 in ovulatory, 56.2 in estrous, and 76.3 in long-term ovariectomized animals. The values for the ovulatory and estrous rabbits are significantly different at the P less than 0.05 level from those of the ovariectomized animals. In all 3 groups the general ultrastructure of the normal ciliated cells is similar. Interestingly, the Golgi complex is very prominent in all. Glycogen bodies occur frequently only in ciliated cells of ovariectomized and occasionally of estrous animals. Abnormalities in ciliation are quite common in the ovariectomized rabbits. The structure of the nonciliated secretory cells varies appreciably within and between the 3 groups. In these cells from well-developed epithelia of certain ovulatory and estrous animals, the apical cytoplasm contains secretory granules of at least three types. In addition, very irregularly shaped, dense, perinuclear granules occur, which may be another type of secretory granule or lysosomes. As compared to ciliated cells, the secretory cells have less prominent Golgi complexes, more abundant bundles of intermediate filaments, a more extensive glycocalyx on their apical surface, and more heterochromatic nuclei. In comparison to the cells of well-developed epithelia, the nonciliated cells of some other ovulatory and estrous rabbits are less well differentiated with fewer or no secretory granules and less well developed organelles. In the nonciliated cells of the long-term ovariectomized rabbits, there are no secretory or dense perinuclear granules. There is a decrease in the number of organelles that are involved in secretion, in the size of the cells, and in the amount of nuclear euchromatin.

Odorant stimulation of secretory and neural processes in the salamander olfactory mucosa

Topical application of the odorants guaiacol (10(-3) mol/l, 1-30 min) and 2-isobutyl-3-methoxypyrazine (IBMP, 10(-5)-10(-3) mol/l, 15 min) caused time- and concentration-dependent reductions in the secretory granule content of acinar cells of the superficial Bowman's glands (sBG) and moderate to extensive vacuolation in acinar cells of sBG and deep olfactory glands (dG). Topical application of 9.8 mg/ml scopolamine 10 min before 10(-4) mol/l IBMP significantly reduced the amount of secretory granule depletion from sBG compared to that seen with IBMP alone and resulted in less extensive vacuolation in sBG and dG acinar cells. The i.p. injection of 42 mg/kg propranolol 10 min before topical application of 10(-4) mol/l IBMP had no effect on the action of IBMP. Guaiacol and IBMP also had time- and concentration-dependent effects on the secretory activity of sustentacular cells in the olfactory epithelium. The protrusion of secretory material into the mucociliary matrix that covers the epithelial surface and vacuolation within the secretory material resulted from odorant application. Scopolamine and propranolol had no effects on the action of IBMP on sustentacular cell secretory activity. When applied in the vapor phase, guaiacol elicited action potentials recorded from individual olfactory receptor neurons; the impulse frequency was concentration-dependent and showed tonic and phasic components when the duration of stimulation was varied. Low to moderate concentrations of IBMP delivered in the vapor phase evoked monophasic negative slow voltage transients recorded from the surface of the olfactory mucosa. The amplitudes of these transients increased with increasing stimulus concentrations. Higher concentrations or longer stimulus durations evoked longer-latency positive-voltage generating processes and negative afterpotentials. The properties of the electrophysiological responses to both odorants were characteristic of responses evoked by a wide variety of 'typical' odorants.

The histochemistry of glycoconjugates in the colonic epithelium of the chicken

In the colonic epithelium of the chicken, glycoconjugates have been studied by means of selected histochemical methods of light and electron microscopy. According to the results obtained, most of the colonic goblet cells contained acidic and neutral glycoconjugates with sulphate and vicinal diol groupings, alpha-D-mannose and alpha-D-glucose residues and sialic acid-galactose dimers. These goblet cells were found to undergo changes in histochemical reactivity during upward migration along the crypts; alpha-D-mannose and alpha-D-glucose residues and terminal sialic acid-galactose dimers increased in amount. The striated border of the colonic columnar cells has, likewise, been found to contain such glycoconjugates as were similar in reactivity to those of the goblet cells. The histophysiological significances of glycoconjugates involved in the chicken colonic epithelium have been discussed with special reference to the functional activities of the carbohydrates.

Estradiol-17 beta and progesterone regulate secretion of uteroglobin through different pathways

Uteroglobin, the primary secretory protein of rabbit uterine epithelium, was localized by the direct immunoperoxidase method in uteri of control ovariectomized rabbits and of ovariectomized rabbits injected with progesterone or estradiol-17 beta. In control rabbits, staining for uteroglobin was almost entirely abolished six weeks after bilateral ovariectomy. Two days following progesterone injection of ovariectomized rabbits, intense staining for uteroglobin could be detected within the endoplasmic reticulum, Golgi complexes, and compact secretory vesicles of most endometrial epithelial cells. Estradiol-17 beta injection resulted in a different intracellular pattern of uteroglobin distribution. Two days following treatment with that steroid hormone, intense staining for uteroglobin was localized within large apical mucous droplets and moderate staining was present in the endoplasmic reticulum and Golgi complexes of these cells. The increased mucin content of the endometrial epithelium following treatment with estradiol-17 beta was confirmed by a periodic acid-Schiff histochemical reaction in the presence of diastase. Quantitation by radioimmunoassay of uteroglobin production in vitro by uterine fragment confirmed that progesterone had a greater effect on enhancing uteroglobin production than estradiol-17 beta and that both steroid hormones did not have any effect after 30 min of incubation in vitro. We suggest that progesterone not only regulates uteroglobin production at the transcriptional level, but that it also regulates the mode of uteroglobin secretion by the induction of a different pathway, compared with the one used when estradiol-17 beta is administered alone.

New observations on the fine structure of the normal nasopharyngeal epithelium of the mouse

The ciliated columnar epithelium in the mouse nasopharynx was studied by use of light and electron microscopes. The ciliated cells were divided into 3 types because of the variability in electron density of the ground cytoplasm. The dark ciliated cells were characterized by well-developed rough endoplasmic reticulum and rod-shaped mitochondria with regular arrangements of pronounced cristae. In the light ciliated cells endoplasmic reticulum was poorly developed and mitochondria were vacuolated with irregular arrangements of cristae. Furthermore, there existed the "medium ciliated cells," termed by the authors, of which the cytoplasm was medium in electron density between the dark and the light ciliated cells, and some mitochondria were rod-shaped and others were vacuolated. The medium ciliated cells are regarded to be at a stage of transformation from the dark ciliated cells to the light ones. These findings suggest that the dark ciliated cells swell to decrease their electron density with declining activity, and finally transform into the light ciliated cells. The cells, termed the "potential ciliated cells" by the authors, were scattered between the ciliated cells, reached the lumen and had no cilia. They contained many procentrioles suggesting ciliogenesis and had a cytoplasm of the same electron density as that of the dark ciliated cells. It is considered that the dark ciliated cells originate from the potential ciliated cells.

Morphological and biochemical changes in mucous cells of the murine sublingual salivary gland during the carbamylcholine-induced secretory cycle

Changes in these cells have been evaluated over 6 h following cholinergic stimulation. Carbamylcholine administration resulted in the release of almost 50 per cent of secretory material within 15 min, which caused a reduction of 33 per cent in cell size. After 2 h the cells were depleted of secretory material. However, in the second hour the release of secretory material was accompanied by an enlargement of the nucleus, Golgi complexes and rough endoplasmic reticulum (RER), which suggests an elevation of biosynthetic activity. The enlargement of the RER was not the result of an increase in RNA, i.e. in the number of ribosomes, but of dilatation of its cisternal spaces. Before release took place, there was a continuous coalescence of secretory granules. After this extensive fusion, which is probably the result of an altered physiological state of the granule membrane and subsequent water uptake caused by cholinergic stimulation, the viscous mucins could be squeezed out, water transport is likely to assist in this ejection. Refilling of the mucous cells was almost complete within 6 h after stimulation.

Proteinases of Pseudomonas aeruginosa evoke mucin release by tracheal epithelium

We have determined the potential of exoproducts from pathogenic bacteria to stimulate the release of high molecular weight mucins from goblet cells of airway epithelium in a rabbit tracheal explant system. Culture supernatants from proteolytic strains of Pseudomonas aeruginosa and Serratia marcescens, but not supernatants from a number of non-proteolytic strains, released mucins from goblet cells. Highly purified elastase and alkaline proteinase from P. aeruginosa stimulated goblet cell mucin release in a dose-dependent fashion. Lipopolysaccharide, exotoxin A, and alginate of P. aeruginosa did not possess mucin release properties. Proteolytic activity was required for mucin release by P. aeruginosa elastase, but such release in goblet cells was not mediated by cyclic AMP. Morphologic studies suggested rapid release of mucins from goblet cells was response to elastase by a process resembling apocrine secretion. Several nonbacterial proteinases mimicked the effect of Pseudomonas proteases. These studies provide support for the hypothesis that bacterial and other play a role in the pathogenesis of mucus hypersecretion in acute and chronic lung infections.

Ultrastructure of a complex epithelial system: the pharyngeal lining of the larval lamprey Petromyzon marinus

Electron microscopy shows that the pharyngeal lining of the larval lamprey Petromyzon marinus is a structurally complex epithelial system that can be separated into eight epithelial types: gill lamellar, gill interlamellar, goblet cell, protective, terminal (taste) bud, preciliated, ciliated in tracts, and ciliated in grooves. Furthermore, these epithelial types encompass at least sixteen different cell types based on ultrastructure and, in some cases, correlative histochemistry (PAS, Alcian blue). Common to nearly all the epithelial types are basal cells and intermediate cells. These two cell types are seen as undifferentiated. Among mature cells, structural specialization as proceeded in three directions: 1) elaboration of mitochondria, probably related to molecular transport (ion-uptake cells, chloride cells); 2) ciliogenesis (preciliated and ciliated cell types); and 3) production of mucous secretory granules (mucous-platelet cells, goblet cells, superficial protective cells, columnar mucous cells, "cobblestone" cells, and marginal and dark cells in the terminal buds). Many of the functions of the cell types relate to the process of suspension feeding in this animal.

The 'transitional' mucosa adjacent to large bowel carcinoma--electron microscopic features and myofibroblast reaction

An electron microscopic study of the 'transitional' mucosa adjacent to 10 carcinomas of the colon showed impaired maturation of epithelial cells. The pericryptal fibroblast layer was absent, accounting for an increase in the length and distension of crypts. In the tunica propria a massive accumulation of myofibroblasts was noted and was indicative of an intensive fibre-producing activity. Review of the literature identifies various theories concerning the functions of myofibroblasts in respect of contraction, embryonal collagen-fibre formation and non-specific stromal reaction. Of these, the latter two are considered likely in relationship to transitional colonic mucosa.

Isolation, culture, and preliminary characterization of mucin-producing cells from trachea of the domestic fowl

Primary cell cultures enriched in mucin-producing cells and basal cells were established from the trachea of the domestic fowl. Epithelial cells were selectively removed from the trachea after incubation in 0.1% pronase/0.1% EDTA in Moscona's saline. The majority of the ciliated cells were removed during the initial 30 minutes of incubation. After 50 minutes of incubation, aggregates of mucin-producing cells and basal cells were removed in large numbers. The cellular aggregates rapidly attached to a collagen-coated substratum and the cells spread out on the culture surface. The mucin-producing cells retained their AB/PAS-reactive secretory granules. The basal cells replicated and as the culture approached confluency, these cells developed a fine dusting of AB/PAS-reactive material; later, larger secretory granules appeared in the cells. These observations suggest that mucin-producing cells are capable of retaining their AB/PAS-reactive secretory products in primary culture and that basal cells are capable of differentiating into mucin-producing cells in vitro.

The surface topography of the colonic crypt in rabbit and monkey

Scanning electron microscopy (SEM) was used to investigate the epithelial topography of the surface and crypt in rabbit and monkey colon. Crypt openings in monkey colon are arranged in a hexagonal pattern, in sharp contrast to rabbit colon where they are randomly arrayed and frequently hidden by epithelial folds. Crypt lumens were exposed by freezing ethanol-dehydrated tissue in liquid nitrogen and fracturing the tissue with a razor blade. The resulting overview of crypt-cell luminal surfaces showed that as columnar cells mature and migrate up the crypt and onto the colonic surface, their microvilli become progressively more abundant. Goblet cells were readily identified in the cross-fractured crypt epithelium; their luminal surfaces are characterized by short, sparse microvilli. The changing appearance of the luminal surface of goblet cells was visualized by SEM during the exocytosis of single mucous granules from unstimulated crypt goblet cells, and during the compound exocytosis of multiple granules in response to acetylcholine.

Electron-microscopic study of the villous adenoma of the colon

The author studied the electron-microscopic peculiarities of villous adenoma as illustrated by 12 cases. She found that the dominant cells of villous adenoma are undifferentiated epithelial cells. Electron-microscopic signs of malignant transformation were revealed by nuclear changes, by the changes in the cytoplasmic membrane and by the immaturity of cells. Leuchtenberger's inclusion bodies are assumed to develop by herniation of cytoplasmic processes of immature tumour cells. In one tumour associated with electrolyte loss, atypical cells were observed with an electronmicroscopic picture indicative of an intense secretory activity. However, the secretion drops differed from the normal mucus drops of the mature goblet cells of the colonic mucosa. The author believes it to be possible that the tumour cells of atypical morphological appearance secrete mucus of abnormal composition which could be responsible for the syndrome of electrolyte loss.

Mechanism of rapid mucus secretion in goblet cells stimulated by acetylcholine

The parasympathetic control of goblet cell secretion and the membrane events accompanying accelerated mucus release were studied in large intestinal mucosal biopsies maintained in an organ culture system. The secretory response of individual goblet cells to 10(-6) M acetylcholine chloride with 3 x 10(-3) M eserine sulfate (a cholinesterase inhibitor) was assessed by light microscopy and autoradiography, by scanning and transmission electron microscopy, and by freeze-fracture. Goblet cells on the mucosal surface are unaffected by acetylcholine. In crypt goblet cells acetylcholine-eserine induces rapid fusion of apical mucous granule membranes with the luminal plasma membrane (detectable by 2 min), followed by sequential, tandem fission of the pentalaminar, fused areas of adjacent mucous granule membranes. These events first involve the most central apical mucous granules, are then propagated to include peripheral granules, and finally spread toward the most basal granules. By 60 min, most crypt cells are nearly depleted. The apical membrane, although greatly amplified by these events, remains intact, and intracellular mucous granules do not coalesce with each other. During rapid secretion membrane-limited tags of cytoplasm are observed attached to the cavitated apical cell surface. These long, thin extensions of redundant apical membrane are rapidly lost, apparently by being shed into the crypt lumen.

Morphology of ovarian mucinous cystadenoma: surface ultrastructure, development and biologic behavior

Thirty mucinous cystadenomas, borderline tumors and cystadenocarcinomas were analyzed by scanning and transmission electron microscopy. Results were compared to those obtained by light microscopy. Benign tumors consisted of endocervical-type columnar, mucus-containing cells with microvilli and cilia, goblet cells and intestinal-type microvillous cells. Borderline tumors showed a decrease in number and size of specialized surface structures in relation to degree of cellular atypia, the number of nucleoli and nuclear indentations indicating areas of incipient malignancy. Invasive carcinomas consisted mainly of intestinal-like surface cells varying in size and shape in relation to degree of tumor differentiation.

The ultrastructure of the normal conjunctival epithelium of the guinea pig. IV. The palpebral and the perimarginal zones

The ultrastructure of the palpebral and perimarginal zones is described and compared to that of the other zones of the conjunctival epithelium of the guinea pig. The palpebral zone was characterized by frequently occurring goblet cells, the structure and function of which are discussed. The transition in the perimarginal zone from a four-layered epithelium with cylindrical superficial cells in the palpebral zone to a multilayered, squamous epithelium towards the lid margin is shown.

Ultrastructure of the goblet cell type of adenocarcinoid of the appendix

Two examples of the goblet cell form of adenocarcinoid were studied with electron microscopy. Mucin was present in the form of large and small vacuoles or small patches of denser mucin granules. A small population of cells had a complement of organelles similar to the more obvious goblet cells but contained little or no identifiable product. Enterochromaffin cells were similar to those seen in normal midgut and in conventional carcinoids of midgut derivation. Enterochromaffin granules and mucin were not mixed with one another. Cell types transitional between mucinous and enterochromaffin were not found. Although study of plasmalemmae was hindered to a degree by artifacts due to tengential sectioning and, possibly, insufficiently rapid fixation, we favor the interpretation that the goblet cell type of adenocarcinoid is composed of two separate classes of cells.

Morphological changes in the human conjunctival epithelium. I. In the normal elderly population

Forty-nine biopsies of bulbar conjunctiva from patients with no apparent conjunctival disease were studied by light and transmission electron microscopy. No significant morphological changes were recorded in those specimens from patients less than 79 years old. However, in the older age group the epithelium showed irregularities in thickness, a reduction in the goblet cell population, and in 25% the presence of 'hyaline bodies'. The epithelial irregularities consisted of mild superficial stratification, which was observed also in a few of the specimens from the younger age groups. The goblet cells appeared morphologically normal in all age groups. The significance of the hyaline bodies and their possible relationship to goblet cells is discussed.

Pathology of mucinous ovarian cystadenomas. 2. Ultrastructural findings

Fourteen mucinous ovarian cystadenomas of different grades of malignancy (7 benign, 4 borderline and 3 malignant) were investigated by electron microscopy. The main tumour cell type was a columnar mucous epithelial cell with short microvilli. With increasing grade of malignancy the shape and size of these cells became more irregular and the number of mucous granules in them decreased. Most of the mucous granules had a dense core and a less dense reticular component, which stained well with the periodic acid-silver methenamine (PASM) technique. Goblet cells with the usual ultrastructure were found rather frequently. The tumours in a given group of malignancy were relative similar to each other in their light and electron microscopic appearance. However, a number of tumours contained argyrophil and argentaffin cells in addition to the columnar and goblet cells. The findings of the present study support the view that the mucinous ovarian cystadenomas arise from the ovarian surface epithelium via a metaplastic process.

[Early alterations of the conjunctiva after alkali-burning (author's transl)]

Early alterations of the conjunctiva after alkaliburning (with 0.25 N NaOH) are described. After chemical damage, there is a nearly total loss of conjunctival epithelium, with simultaneous marked edema in the lower conjunctival parts. Alterations of the surface are examined by scanning electronic microscopy (SEM). Within 24 h marked infiltration of round cells into the conjunctival stroma takes place. After burning, we find a rapid decrease in the ATP level in the conjunctiva to about one-tenth of the normal value, whereas glucose and lactate showed only small alterations before and after chemical injury.

The cytochemical localization of adenylate cyclase activity in mucous and serous cells of the salivary gland

The present study was undertaken to localize adenylate cyclase activity in salivary glands by cytochemical means. For the study, serous parotid glands and mixed sublingual glands of the rat were used. Pieces of the fixed glands were incubated with adenosine triphosphate (ATP) or adenylyl-imidodiphosphate (AMP-PNP) as substrate: inorganic pyrophosphate or PNP liberated upon the action of adenylate cyclase on the substrates is precipitated by lead ions at their sites of production. In both glands, the reaction product was detected along the myoepithelial cell membranes in contact with secretory cells, indicating that a high level of adenylate cyclase activity occurs in association with these cell membranes. The association with a high level of the enzyme activity might be related to the contractile nature of myoepithelial cells which are supposed to aid secretory cells in discharging secretion products. A high level of adenylate cyclase activity was also detected associated with serous secretory cells (acinar cells of the parotid gland and demilune cells of the sublingual gland), but not with mucous secretory cells. In serous cells, deposits of reaction product were localized along the extracellular space of the apical cell membrane bordering the lumen. This is the portion of the cell membrane which fuses with the granule membranes during secretion. Since the granule membranes are not associated with a detectable level of adenylate cyclase activity, it appears that the enzyme activity becomes activated or associated with the granule membranes as they become part of the cell membrane by fusion. The association with a high level of adenylate cyclase activity appears to be related to the ability of the membrane to fuse with other membranes. It is likely, since the luminal membrane of mucous cells which does not fuse with mucous granule membranes during secretion is not associated with a detectable enzyme activity.

The cytochemical localization of adenyl cyclase activity in rat sublingual gland

Adenyl cyclase activity in mucous acinar cells and serous demilune cells of the rat sublingual gland was localized cytochemically. After incubation with adenylyl-imidodiphosphate (AMP-PNP) as substrate, deposits of reaction product are found along the cell membranes bordering the secretory surfaces of serous demilune cells. These are the membranes which participate directly in secretion by fusing with the granule membranes. The granule membranes of the demilune cells do not reveal reaction product, but the membranes of the granules which are fused with and become part of the cell membrane do show deposits. Thus, it appears that the cell membranes which fuse with granule membranes during secretion are associated with a high level of adenyl cyclase activity. In support of this, the luminal membranes of the mucous acinar cells which do not fuse with granule membranes during secretion are not associated with detectable amounts of adenyl cyclase activity.

Renewal of the epithelium in the descending colon of the mouse. IV. Cell population kinetics of vacuolated-columnar and mucous cells

Proliferation and migration of cells in the vacuolated-columnar and mucous cell lines were studied in the descending colon of adult female mice given a single injection or a continuous infusion of 3H-thymidine and killed at various intervals from one hour to 12 days. This investigation was carried out using one mum-thick Epon sections which were radioautographed after staining with the periodic acid-Schiff technique and iron-hematoxylin. In the normalized crypts with ten equal segments, labeled vacuolated cells at one hour after injection of 3H-thymidine were encountered in the lower four segments and in decreasing numbers in segments 5 through 7. From the percent labeled cells in segments of the crypt, the birth rate and fluxes of cells were computed. Moreover, it was found that a cell in the vacuolated-columnar cell line would undergo three mitotic cycles on the average from its birth at the cryptal base to its extrusion from the surface; of these three cycles, the last one which took place from segment 3 to segment 7 appeared to be a changeover from dividing cells to non-dividing cells, in accordance with the "slow cut-off" model of Cairnie et al. ('65b). Mucous cells located in segments 1 through 6 of the crypt were capable of incorporating 3H-thymidine and thus capable of undergoing mitosis. However, the rate of turnover of mucous cells based on proliferative rate was found to be much lower than the rate of turnover of mucous cells based on the transit time in the non-dividing segments of the crypt. Since there was a concomitant overproduction of cells in the vacuolated cells and newly formed mucous cells in the lower portion of the crypt, it was concluded that some vacuolated cells would give rise to mucous cells. This putative transformation occurred in the lower four segments of the crypt. Mucous cells which were formed by transformation would migrate upward along the cryptal wall and accumulate more mucus in the theca; in doing so, they would undergo two divisions, on the average, before they became non-dividing mucous cells. In ascending the cryptal walls, both vacuolated-columnar cells and mucous cells appeared to migrate at a similar speed; they moved much slower at the base of the crypt and accelerated toward the upper portion of the crypt, but they migrated at a constant speed in the non-dividing segments of the crypt.

[The development of the guinea pig gallbladder epithelial cells. II. Electron microscopical and enzymhistochemical investigations (author's transl)]

The development of the guinea pig gallbladder epithelium follows a distinct time schedule. During the first phase (up to 30th day of intrauterine life) the epithelial cells increase in number. They remain small and undifferentiated. In the second phase, from the 30th to the 44th day, cytodifferentiation is a dominating feature. The epithelial cells increase in height, the nuclei become more basal, the cells acquire their final zonal structure and the cell organelles exhibit their characteeristic appearance. Weak enzyme activities can be observed. In the third phase, from the 45th day until birth, there is functional differentiation and the adult pattern of enzyme distribution is established. Glycogen appears first on day 29, increases in amount and then disappears by day 57. There is a marked development of the Golgi apparatus associated with increased synthesis of secretory material. Between the 59th embryonic day and the 6th day of life mucoid cells with different functional states appear in the gallbladder epithelium. Later on these cells can be visualized only in the depths of the invaginations. After birth the epithelial cells become more columnar and by 10 days after birth the adult appearance of the epithelium is fully established.

Mucous change in the human duodenum: a light and electron microscopic study and correlation with disease and gastric acid secretion

The significance of mucous change in the human duodenum in a series of patients with peptic ulcer disease has been appraised. No specific correlation was demonstrated with the acid output of the stomach if the extent of the change is considered, but it was shown to be more common in the higher acid states. Electron microscopic studies confirmed the specific structure of the mucous cells of the duodenum and suggest that they arise either by transformation of Brunner's gland cells or as a distinctive population in the crypts. It is suggested that the mucous change is a protective mechanism involved in some way as yet unknown with the healing of ulcers.