Gastric surface mucous cells (SMC), mucous neck cells (MNC) and their undifferentiated and immature precursors were studied by light and electron microscopic histochemistry. The secretory granules of SMC were smaller, more electron dense and more reactive to PAS and its analogues than those of MNC. Alcian blue demonstrated that the mucus of SMC was acidic and that of MNC was neutral. The periodic acid —thiocarbohydrazide —silver proteinate method revealed the presence of carbohydrates in the Golgi apparatus, condensing vacuoles, secretory granules, apical vesicles and tubules and cell coat. Maturation of SMC during their migration towards the free surface was reflected by an increase in size and number of secretory granules, an increase of RER and microfilaments, and a decrease of microvilli and apical vesicles and tubules. The secretory granules of older SMC were less acidic and possessed a proteinaceous core. Most MNC were fully differentiated, but some immature MNC containing only a few granules were found. Furthermore, undifferentiated cells and intermediates between SMC and MNC were also observed. The presence of both transitional and intermediate forms indicates that both SMC and MNC arise from the same population of undifferentiated cells. Incorporation of 3H-thymidine revealed that undifferentiated cells, isthmic SMC, MNC and intermediate cells are proliferative. No proliferative activity was found in foveolar SMC, parietal, chief, fibrillovesicular or endocrine cells.

Ultrastructural and carbohydrate histochemical studies on the differentiation and renewal of mucous cells in the rat gastric fundus.

Ultrastructural and complex-carbohydrate cytochemical studies were carried out on guinea pig gastric mucosa to assess the histochemical properties of the secretions of different gastric epithelial cells and to investigate the differentiation, origin, and renewal of certain cell types. The observations disclosed heterogeneity or variability of the secretory granules within individual mucigenic cells and zymogen cells. The cytochemical methods also served in characterizing and distinguishing five cell types in the gastric glands, including the isthmus cell, a mucous cell considered comparable to the mucous neck cell, the chief cell, and forms transitional between the isthmus and mucous cells and the mucous and zymogenic cells. The several cell types differed widely in the cytochemical properties of the secretory granules and of the apical plasmalemma, and each had a distinctive distribution in the gastric gland. Cytochemical staining observed here provided evidence on synthesis and intracellular metamorphosis of mucous droplets and on formation of glycocalyx.

Ultrastructural cytochemistry of complex carbohydrates of gastric epithelium in the guinea pig.

The derangements in production and secretion of gastric mucus consist of: 

1)

Quantitative changes in concentration and output of mucus;




2)

Qualitative changes in its composition;




3)

Increased shedding of the mucus-containing surface epithelial cells and excessive extrusion of the mucus from the cells;




4)

Abnormalities in the biosynthesis of glycoproteins of the mucus.

Derangements of Biosynthesis, Production and Secretion of Mucus in Gastrointestinal Injury and Disease

The effect of ethanol on the mucosa of the Heidenhain pouch in dogs was studied by instilling ethanol in concentrations of 10, 20 and 40% using changes in ionic fluxes of an acid solution and mucosal alterations to measure the effects of ethanol. The instillation of 20 or 40% ethanol resulted in increased insorption of H+ and increased exorption of Na+ into the pouch lumen. Following the administration of 20 and 40% ethanol, the mucous layer and mucin content of the lining epithelial cells decreased markedly. Hourly bathing with the acid test solution aggravated the injury and induced bleeding, but hourly instillation of a buffer solution minimized the damage. Ionic fluxes returned to pre-ethanol levels 2 hr after 20% ethanol and 3–4 hr after 40% ethanol. Partial restoration of mucosal damage occurred in 4–6 hr and was complete in 24 hr.

Effects of ethanol on the gastric mucosa of the Heidenhain pouch of dogs

This paper describes the ultrastructural, topographical changes seen in rat gastric mucosa following application of 0.1 N HCl or 1, 10 or 50 mM NaF in 0.1 N HCl to the stomach. No morphological differences were noticed between the 0.1 N HCl (control) and 1 mM NaF in 0.1 N HCl specimens. Ten milliomolar NaF in 0.1 N HCl produced some desquamation of surface mucous epithelial cells while 50 mM NaF produced extensive damage to cells surrounding the gastric gland openings (foveolae) as well as interfoveolar cell loss.

Surface changes in rat gastric mucosa induced by sodium fluoride: a scanning electron microscopic study

The staining of mucous cells in the gastric fundic mucosa has been studied in various species, including man. In most cases, a mucous coat is observed, at the apical pole of mucous cells, in the epithelium and in the deep part of the gastric pits. This coat stands between the cell cytoplasm and the gastric lumen. The surface coat stains positively with PAS and alcian blue, and its characteristics differ depending on the species and the topography of the cell. In some cases, particularly in the cat, the coat is a very thin line, coalescent with the plasma membrane; this could be the optical appearance of the polysaccharidic extraneous coat described in ultrastructure. More often the coat is thick, projecting into either the gastric lumen or the cell cytoplasm, its significance being questionable. In the deep part of the gastric pits of the rat, histoautoradiography after injection of radiosulfate demonstrates an incorporation of sulfate-35 in the apical pole of these cells, encircling the plasma membrane. This mucous apical layer is thus rich in sulfated glycoproteins. This coating of the apical pole in the cells regenerating the mucosa could intervene in the resistance of the mucosa against pepsin. Indeed, such molecules can inhibit peptic proteolysis by a specific mechanism—the formation of a complex when joined with the proteins of the cell surface.

Apical localization of glycoproteins in gastric mucous cells

One of the most promising approaches in the drug delivery field is the use of naturally occurring self-assembling protein nanoparticles, such as virus-like particles, bacterial microcompartments or vault ribonucleoprotein particles as drug delivery systems (DDSs). Among them, eukaryotic vaults show a promising future due to their structural features, in vitro stability and non-immunogenicity. Recombinant vaults are routinely produced in insect cells and purified through several ultracentrifugations, both tedious and time-consuming processes. As an alternative, this work proposes a new approach and protocols for the production of recombinant vaults in human cells by transient gene expression of a His-tagged version of the major vault protein (MVP-H6), the development of new affinity-based purification processes for such recombinant vaults, and the all-in-one biofabrication and encapsulation of a cargo recombinant protein within such vaults by their co-expression in human cells. Protocols proposed here allow the easy and straightforward biofabrication and purification of engineered vaults loaded with virtually any INT-tagged cargo protein, in very short times, paving the way to faster and easier engineering and production of better and more efficient DDS.

All-in-one biofabrication and loading of recombinant vaults in human cells

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Apical localization of glycoproteins in gastric mucous cells

All-in-one biofabrication and loading of recombinant vaults in human cells